geothermal heat pumps a guide for planning and installing

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00000___4906723f9fcb7caa5873a30191061927.pdf

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00001___3e0ed7463e3cc3215cd7f3721d778111.pdfGeothermal Heat Pumps

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00002___7a60067263273a00461654df3cb4b313.pdf

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00003___a713d81a52aaf2ad26e62a84cf8c58e6.pdfGeothermal Heat PumpsA Guide for Planning and Installing

Karl Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00004___bff6ced00d193a67dde274065fa149ca.pdfFirst published by Earthscan in the UK and USA in 2007

Copyright Karl Ochsner

All rights reserved

ISBN-13: 978-1-84407-406-8Typeset by 4word Ltd, BristolPrinted and bound in the UK by Cromwell Press, TrowbridgeCover design by Yvonne Booth

For a full list of publications, please contact:

Earthscan812 Camden High StreetLondon NW1 0JH, UKTel: +44 (0)20 7387 8558Fax: +44 (0)20 7387 8998Email: [email protected]: www.earthscan.co.uk

22883 Quicksilver Drive, Sterling,VA 20166-2012, USA

Earthscan publishes in association with the International Institute forEnvironment and Development

A catalogue record for this book is available from the British Library

The information and data contained in this book were produced to the bestknowledge of the author and were carefully reviewed by both the author andpublisher. Nevertheless, errors in the contents may exist. For this reason, data aregiven without the guarantee of the author or publisher. The author and publishertake no responsibility for the existing inaccuracies in content.

The German Library lists this publication in the German National Bibliography;detailed bibliographical information is available on the Internet athttp://dnb.ddb.de.

Library of Congress Cataloging-in-Publication Data[!data to be inserted here!]

The paper used for this book is FSC-certified and totally chlorine-free. FSC (theForest Stewardship Council) is an international network promoting responsiblemanagement of the worlds forests.

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00005___8a2e6e7b0c64a4debb7238d980bfb6b2.pdfTable of Contents

Preface xiIntroduction by Robin H. Curtis xiiList of Acronyms and Abbreviations xix

1 Reasons to Use a Heat Pump 11.1 Environmental benefits 1

1.1.1 Our environment is in danger 11.1.2 Tracking down the culprit 21.1.3 Heat pumps offer emission-free operation on-site 2

1.2 Operating costs 41.3 Independence 51.4 Comfort 61.5 Security for the future 61.6 Non-flammability 81.7 Responsibility for the future 81.8 Ideal for low energy houses 81.9 Retrofit 81.10 Multiple functions 91.11 Public promotion 91.12 Energy politics/laws 9

2 Theory of the Heat Pump 112.1 The principle 112.2 The refrigeration cycle 122.3 Coefficient of performance 122.4 Carnot Cycle 132.5 Working fluid/refrigerant 152.6 Enthalpy-pressure diagram 162.7 Heat pump cycle with injection cooling 17

3 Heat Pump Types 183.1 Brine/water, water/water heat pump 18

3.1.1 Refrigeration cycle 193.1.2 Refrigerant 193.1.3 Electrical components and controller 203.1.4 Safety measures 203.1.5 Display 20

3.2 Direct expansion/water heat pump 213.2.1 Refrigeration cycle 223.2.2 Refrigerant 22

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00006___10f941b84a980f72e9a02b50a2868c44.pdf3.2.3 Electrical components and controller 233.2.4 Safety measures 233.2.5 Display 23

3.3 Direct expansion/direct condensation heat pump 233.4 Air/water heat pump split units 24

3.4.1 Refrigeration components indoor unit 243.4.2 Refrigeration components outdoor unit 243.4.3 Refrigerant 253.4.4 Electrical components and controller 253.4.5 Safety measures 253.4.6 Display 25

3.5 Air/water heat pump compact units, indoor installation 263.5.1 Refrigeration cycle 263.5.2 Refrigerant 263.5.3 Electrical components and controller 273.5.4 Safety measures 273.5.5 Display 27

3.6 Air/water heat pump compact units, outdoor installation 273.7 Domestic hot water/heat pumps air source, split units 28

3.7.1 Refrigeration cycle 283.7.2 Refrigerant 293.7.3 Electrical components 30

3.8 Domestic hot water heat pump air source, split units 303.9 Ground/water heat pump domestic hot water heat pump air source,

split units 323.10 Air/air heat pump ventilation 333.11 Exhaust-air heat pumps, additional design 333.12 Heat pumps for air heating/cooling 33

4 Complete System Planning 354.1 Planning a heat pump heating system 354.2 Heat source selection 364.3 Heating system selection 364.4 Heat pump selection 37

4.4.1 Determination of heating demand 374.4.2 Utility interruptible rates 384.4.3 Domestic hot water heating 394.4.4 Operation configurations 394.4.5 Heat pump selection 41

4.5 Retrofit/renovation 44

5 Planning Instructions for Ground Heat Source Brine Systems(Horizontal Collector, Trench, Vertical Loop) 46

5.1 Ground heat source 465.1.1 System description 46

vi GEOTHERMAL HEAT PUMPS: A GUIDE FOR PLANNING AND INSTALLING

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00007___07abdf35f435b8436df8f1cdbc477da4.pdf5.2 Ground conditions 465.3 Layout and installation of ground collector 47

5.3.1 Horizontal collector installations 475.3.2 Trench collector/spiral collector 495.3.3 Vertical loop 49

5.4 Connection 525.4.1 Collection vault 525.4.2 Safety clearance 535.4.3 Building penetrations 53

5.5 Brine circulation loop 535.6 Commissioning 565.7 CO2 loop 57

6 Planning Instructions for Ground Heat Source Direct ExpansionSystems 58

6.1 Ground heat source 586.2 Ground conditions 596.3 Layout and installation of collector 59

6.3.1 Horizontal loop installations 596.4 Connection 61

6.4.1 Collection vault 616.4.2 Safety clearance 616.4.3 Building penetration 62

6.5 Commissioning 62

7 Planning Instructions for Water Heat Source Systems 637.1 Water heat source 637.2 Ground and well conditions 647.3 Design 647.4 Connection 667.5 Components/filter 667.6 Building penetrations 667.7 Commissioning 66

8 Planning Details for Air Heat Source Systems 698.1 Air heat source 698.2 Design 70

8.2.1 Split-system 708.2.2 Compact systems indoor set-up 728.2.3 Compact systems outdoor set-up 73

8.3 Operation configuration 758.3.1 Monovalent systems 758.3.2 Bivalent-parallel 768.3.3 Bivalent-alternate 77

8.4 Commissioning 77

TABLE OF CONTENTS vii

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00008___c160f8fb0db356fcb1bab5908287d8d8.pdf9 Planning Instructions Heating Systems 789.1 Heating circulation loop control 789.2 Hydraulic separation 789.3 Buffer storage tank 809.4 Circulation pump 809.5 Connection group 819.6 Heating/cooling distribution system 81

9.6.1 Radiant floor heating 829.6.2 Heating capacity and self-controlling effect 849.6.3 Radiant wall heating 869.6.4 Radiators 87

9.7 Domestic hot water production 87

10 Heating and Cooling Reversible Heat Pump 9010.1 Response to climate change 9010.2 Technical requirements for buildings 9010.3 Planning for active cooling 9110.4 Sizing of ground collectors and vertical loops 9210.5 Cooling distribution system: radiant/surface cooling 9310.6 Refrigeration circuit for active cooling 9310.7 Control 9410.8 Economics 9410.9 Solar cooling 9510.10Groundwater heat source 9510.11Operating range 95

11 Control of Heat Pump Heating Systems Electrical Connections 9611.1 Controller and control system 9611.2 Heat pump control 9611.3 Additional functions of heat pump control 9711.4 Hydraulic schematics 9711.5 Single room control/zone control 9711.6 Other systems 9811.7 Electrical connections 98

12 Domestic Hot Water Production 10012.1 General instructions for domestic hot water 100

12.1.1 Why not with the heating loop? 10012.1.2 Domestic hot water system comparison 10012.1.3 Separation of domestic hot water from the heating system 10312.1.4 Information for planning and operation of a domestic hot water

system 10412.1.5 Installation instructions 10412.1.6 Hot water demand guidelines 10412.1.7 DVGW worksheet W551 104

viii GEOTHERMAL HEAT PUMPS: A GUIDE FOR PLANNING AND INSTALLING

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00009___14fa58cef2ff18747ea14adc7b9e882b.pdf12.2 Additional optional functions of hot water heat pumps 10512.2.1 Additional cooling benefit 10612.2.2 Additional basement dehumidifying benefit 10612.2.3 Additional distilled water benefit 10612.2.4 Additional ventilation benefit 107

12.3 Installation 10812.4 Water connections 109

12.4.1 Water connections 10912.4.2 Air connections 10912.4.3 Air ducts 10912.4.4 Condensate water drain 10912.4.5 Ground collector connection 10912.4.6 Heating heat exchanger 109

13 Controlled Dwelling Ventilation 11113.1 Why ventilate? 11113.2 Why controlled dwelling ventilation? 11213.3 Types of controlled dwelling ventilation 11313.4 Comprehensive living climate 11413.5 Combined units for heating, hot water preparation and ventilation 115

14 Specialized Installations 11614.1 Renovations 11614.2 Low energy/passive house 11714.3 Swimming pool heating 11914.4 Livestock stable heat pump 11914.5 Absorber 12014.6 Heat pumps for industrial applications 12014.7 Industrial waste heat use/indirect water source 12214.8 CO2-heat pipes 123

15 Appendices 126A Hydraulic schematics 126B Investment/operation costs (1/2007) 133C Units, symbols and conversion 141

List of Figures and SourcesList of Tables and Sources

TABLE OF CONTENTS ix

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00010___3be4a9de8ee3807424068c80f1828fcc.pdf

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00011___782fdf272856a06c94a874193c4ebcef.pdfPreface

Since the release of the first edition in 2000, significant strides have been maderegarding the acceptance of heat pump technology by operators and technicians, aswell as by the public. Finally, the gap between national Kyoto Protocol goals andactual CO2 emissions is being addressed with new policies. Heat pump technology,which has received too little attention until now, is now gaining some of the creditto which it is entitled.This is due to the fact that energy efficiency and environmentalimpact guidelines for heating technology are often best fulfilled through the use ofheat pump technology.This handbook is intended to act as a guideline for the planning and installation

of heat pump heating systems. The contents are based on years of practicalexperience and results of ongoing development, as well as broad, internationalknowledge exchange.Today, heat pump systems can provide an optimal indoor climate, optimal heating

comfort, health and contentment in living and working areas. They do so moreefficiently, more economically and with less environmental impact than most otherheat sources (including some renewable sources). In addition, heat pumps can oftenoffer the lowest heating, air conditioning and hot water preparation costs.An honest and technologically up-to-date assessment of global emissions and

economic factors favours heat pump technology. In the interest of energy securityand operational reliability in the future, heat pumps deserve our attention today.In this edition, the changes in energy prices and environmental requirements over

the last 12 months are taken into account. The reader receives a newly revisedhandbook for a growing, innovative market, with new figures, graphics and tables.

Karl Ochsner, Dipl. Ing. ETH

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00012___dd2aa3467304700f3d7fe259d874ac21.pdfIntroduction

When Lord Kelvin described the theoretical basis for the heat pump in 1852, he couldsee no contemporary use for it as a heating device but only for the provision ofcooling in large colonial residences in Imperial India. He was prophetic inthis respect, in that the use of heat pumps in buildings went on to be dominatedby air conditioning and cooling. Millions of air conditioners, chillers andrefrigerators (i.e. heat pumps) are manufactured and installed every year throughoutthe world.The widespread use of heat pumps for heating buildings has taken longer to

evolve. For many years, heat pumps for heating were seen as the domain of eccentricengineers who built and installed them in small numbers, primarily in Europe andthe US.Over the last 50 years the technology has been slowly perfected, to the pointwhere heat pumps for domestic heating are now mainstream technology in severalEuropean countries and in the US, and are growing in significant numbers elsewhere.It is difficult to find definitive numbers for every country, but at the five-yearlyWorldGeothermal Congress in 2005 a worldwide review based on national submissionsconcluded that there are in excess of 1.3 million 12 thermal kilowatt (kWth)equivalent systems installed (Lund et al, 2005). These range in size from a fewkilowatts (kW) to several megawatts (MW) of heating and/or cooling.Despite his eminence in most things thermodynamic, what Lord Kelvin would

probably not have foreseen was the role that heat pumps could play in reducingcarbon emissions. In 1851 the world population was 1.1 billion. Today it has passed6 billion, and is predicted to reach 9 billion by 2050.The use of fossil fuels to deliverheating in homes and offices is one of the largest sources of carbon dioxide (CO2)emissions worldwide. With the release of the most recent report of theIntergovernmental Panel on Climate Change in February 2007 (IPCC, 2007), thereis overwhelming evidence of the significance that manmade carbon emissions arehaving on global warming. Heat pumps are one of the few developed, reliable andwidely available heating technologies that can deliver thermal comfort at either zeroor greatly reduced carbon emissions. Most heat pumps are electrically driven, andas the generators reduce the amount of carbon dioxide emitted as a by-product ofelectricity production, so heat pumps will become even more carbon efficient withtime something that no fossil fuelled boilers can aspire to.Ultimately it is possibleto envisage heat pumps being powered by zero carbon content electricity.While it was not the original stimulation for the use of heat pumps, the reduction

in carbon emissions arising from the heating of buildings is probably the mostsignificant driver for their use in todays environment certainly in central Europe.The International EnergyAgency (IEA)Heat Pump Centre has recognized that heatpumps are one of the most significant single market available technologies that canoffer large CO2 reductions.

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00013___fa141469b5360a08f93ad10ac8b5aaa6.pdfIn addition, heat pumps offer other benefits: no on-site emissions, no on-site fuelstorage, no flues or chimneys, a completely clean operation.Depending on local fueltariffs, they can offer reduced heating costs, as well as deliver increased fuel pricestability and fuel independence. With the arrival of Peak Oil, growing oil and gasdemand, and the inevitable forthcoming rise in fossil fuel prices, the running costadvantages are likely to tip further in favour of heat pumps.Because heat pumps derive the bulk of their delivered thermal energy from the

environment (i.e. air, water or ground), this significant utilization of renewableenergy is also capable of meeting the growing national and local targets for theincreased adoption of renewable heat.In the last half of the 20th century, heat pumps for heating, particularly in the

domestic sector, evolved from a small, cottage/garage based operation populated byenthusiasts into a mainstream activity.Today, there are internationally known brandleaders capable of manufacturing tens of thousands of heating heat pumps every year in addition to the many hundreds of thousands, if not millions, of heat pumps thatare manufactured for cooling.The challenge now is to train enough knowledgeablesales staff, designers, installers and maintenance engineers to ensure that these heatpumps are correctly sold, specified, designed, installed and commissioned.The challenge for anyone coming into this industry is that customers can rightly

expect to be sold a fully functioning, modern, properly installed heat pump system.New players,whether individual installers or large heating contractors, are not goingto have the luxury of learning and experimenting on the job over 10 or 20 years, atcustomers expense.The experience of the established players, primarily in northernand central Europe and in the US must be adapted to local conditions quickly andappropriately so that high quality systems come on stream straight away. It issobering to recognize that domestic heat pumps for heating, particularly groundsource heat pumps, have had a history of poor quality selling, design, installation andequipment in several countries. So bad was this experience that the industry nearlycollapsed before adequate training and standards were put in place to recover thesituation. This must be avoided as the industry moves forwards in countries justembarking on the widespread adoption of heat pumps for heating.One of the difficulties in acquiring the required knowledge is the lack of generic,

English language reference material on heat pumps for the domestic sector. Thereis high quality material in the US primarily emanating from the InternationalGround Source Heat Pump Association (IGSHPA) but much of this relates towater to air, and ground to air systems which are very uncommon in the Europeandomestic scene.High quality, non-English material exists in Europe, primarily in theform of manufacturers technical guides some of which have yet to be translated.Naturally they relate to the manufacturers own product range.In this book, a highly respected, long-term player in the European domestic heat

pump sector has put together a wealth of information related to his experience overthe last 30 years.While the author is himself a heat pump manufacturer, he stronglyfeels that generic information must be made widely available to all those wishing toget involved in this industry in order to drive forward the number of qualityinstallations. The first edition of this book, in German, was released in 2000. Since

INTRODUCTION xiii

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00014___55be93784915c8d2a583c7c3398803a4.pdfthen it has been through four editions and is here translated into English to meetthe growth of heat pump installation, particularly outside of the well establishedGerman/Austrian/Swiss markets.For those who already know about heat pumps, they can proceed directly to the

main introduction. The focus of the book is on types of heat pumps and theirselection and application.While aspects of ground design are referred to in relationto ground source heat pumps, this book is not intended as a detailed reference forwould-be ground loop designers.The author pulls together his widespread, long-termexperience in manufacturing and installing high quality water, ground and air sourceheat pumps. Combining this material with the relevant manufacturers data sheetsand technical guides should allow any would-be practitioner to embark on the designand installation of high quality heat pump systems that meet their customersrequirements and hopefully their expectations. Existing heat pump installers willundoubtedly find new and relevant information that will be of use to them as theyexpand their repertoire of installations.For those who are new to heat pumps, particularly for heating in the domestic

and small commercial sectors, a few words of explanation may be useful beforedelving further into the book.Heat pumps do exactly what they say they pump heat.Kelvins great theoretical

advance was that he overturned the notion that heat could only flow downhill, i.e.from hot to cold.The heat pump is able to collect low grade heat and deliver it at ahigher temperature albeit using some imported energy to do so.This is the principleof the refrigerator. The heating heat pumps discussed here collect low grade heatfrom the atmosphere (air), bodies of water (boreholes, lakes, rivers), or the ground.Using a refrigerant circuit, this heat is upgraded by an electrically driven compressorand can then be delivered at a useful temperature for heating. For cooling, theprocess is simply reversed: low temperature heat is collected from inside a building,upgraded and rejected to the atmosphere, water or ground. Using moderncompressors and refrigerant cycles in well designed heat pump systems, it is possibleto deliver heat at high energy efficiencies. A properly sized system using modernequipment can deliver between 2.5 and 4.5 units of heat (kWhth) for every unit ofelectricity consumed (kWhe).The ratio of these two numbers is commonly referredto as the Coefficient of Performance (COP). Readers should recognize that thequantity of electricity used to drive the heat pump is not insignificant compressorsare electrically demanding. However, depending on the fuel tariff for electricity vsfossil fuels, it is not uncommon to find that heat pumps can offer lower running coststhan conventional fossil fuels or direct electric heating systems. Obviously it takesfuel to generate the electricity to drive the compressor.However,with modern powerstations generating at ~35 per cent efficiency, and a heat pump with a COP of say3.5, the heat pump will be 1.4 times more energy efficient than a gas fired boiler.With a modern combined cycle power station generating at say 45 per cent efficiency,and a heat pump in a new house with a COP of 4, the heat pump can be twice asenergy efficient as the boiler.The cost savings will depend on the relative fuel tariffs.Depending on the fuel sources that are used to generate the electricity, the overallcarbon savings can be very significant.

xiv GEOTHERMAL HEAT PUMPS: A GUIDE FOR PLANNING AND INSTALLING

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00015___f98e82ed5ea32ce8012d478668fe2b71.pdfThe reader may wonder why heat pumps are not the panacea for every buildingin the country. It is safe to say that any new building in the US or northern/centralEurope that is built to the current building regulations is a suitable candidate for aheat pump.The total heating load and some, or all, of the hot water load can be metby todays heat pumps. There are some local limitations, for example in countrieswith single phase electrical supplies in the housing sector, that have upper limits onthe size of compressor that can be used. The levels of insulation used in modernhouses means that this is less of a restriction than it used to be.The main limitationon heat pumps arises in the older, existing housing market. This is because heatpumps currently deliver maximum temperatures in the range 55C to 65C.Traditional boiler systems can work at anywhere between 70C and 90C. In poorlyinsulated buildings, heat pumps may not be able to deliver year round comfort levelsif such high temperatures are really required. In these situations, it is still possibleto have hybrid or bi-valent heating systems where the heat pump works for asmuch of the heating season as possible, and the secondary source meets demandson the coldest days. This is not an unusual combination for air source heat pumpsin mainland Europe. Improvements to the insulation, draft proofing andmodificationof the heat emitters to utilize the lower output temperatures of heat pumps is alsoan approach for older buildings.In the context of this book, the types of heat pumps that are discussed derive their

main heat input from the air, water or ground.While all three sources are used inEurope and the US, they tend to diverge in terms of the output side.The bulk of thedomestic systems installed in NorthAmerica deliver warm (or cool) air via ductworkinto the building. In Europe, the most common form of heat distribution system inthe domestic sector is water, either via wet radiator systems or wet underfloor(hydronic) heating. Many US units, particularly in the southern states, are reversecycle units, capable of delivering warm or cool air.Thus in Europe the predominantheat pumps are air/ground/water-to-water heat pumps, whereas in the US andCanada they are more likely to be /air/ground/water-to-air.For historical reasons the ground source heat pumps in Europe are often referred

to as brine systems because brine was originally used as the antifreeze in closedloop systems.Heat pumps for heating and cooling buildings use the wider environment as their

energy source (or sink for cooling). Clearly the most widely available source is theair.The traditional difficulty for an air source heat pump is that on the days that themost heat is required, the outside air will be at its coldest making it very difficultfor the heat pump to achieve high efficiency, or possibly not being able to deliverenough output.With advances in compressor technology, heat exchanger design andcontrol methods, this limitation is gradually being eroded and air source heat pumpsfor domestic heating are becoming more widely adopted. For well insulated buildingsin moderate climates they can meet all heating needs: in more demanding situationsthey may have to work in conjunction with a secondary heat source.Water and ground source heat pumps have a basic technical advantage over air

source units in that water has a far higher heat carrying capacity than air, better heattransfer characteristics, and can be moved around very efficiently with small

INTRODUCTION xv

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00016___6a2ee123dbebf5efe0aa4962f324f77d.pdfcirculating pumps.Thus water source heat pumps have always been very efficient its just that most buildings have not had a suitable water source.Where there is ariver, lake or borehole water, a water source heat pump is a very efficient means ofdelivering heating (and/or cooling).However,much of todays interest in heat pumpshas been generated by the introduction of ground source (or geothermal) heatpumps. Technically these should be referred to as closed loop, ground source heatpumps. These use the ground around (or under) a building as their heat source orsink. By installing a suitably sized loop of pipework in the ground, water can becirculated to collect the renewable energy stored in the earth and deliver it to a watersource heat pump.While very simple in concept, these closed loop systems are a littlemore complex in their design and operation, because the loop temperatures areengineered to change in order to induce the movement of heat by conductionthrough the ground. Considerably more care has to be taken in the selection, designand installation of closed loop (geothermal or brine) systems, compared to air andwater source units, to ensure satisfactory, efficient operation.The designer needs toappreciate that closed loop ground source heat pumps are a coupled systemcomprising the building, the heat pump and the ground loops.All three need to becarefully matched to achieve a system that delivers the required amount of heat,efficiently, year-on-year for many years.While some general guidelines are providedin this book on ground loop sizing, it is recommended that designers of larger ormore complex ground loop systems will need to garner further information on thisspecialist aspect.While trained heating engineers, plumbers or building contractorswill be able to handle the installation of horizontal or trenched based groundloops, experienced drilling companies should be used to install borehole basedsystems.While we have talked about the use of heat pumps for heating and cooling, it

should be appreciated that heat pumps can also be used for generating domestic hotwater to varying temperatures. The simplest way of doing this may be to use anintegrated stand alone air-to-water unit specifically designed for this purpose thatcomes fully integrated with a hot water tank.These are relatively new in the marketplace and have some way to go as a common method of generating hot water withheat pumps. The would-be practitioner should be warned that there are numeroussuggestions for how a heating heat pump should be configured to generate hot water.Many thousands of systems are successfully delivering domestic hot water, butattention must be paid to the use of appropriately sized tanks, using significantlylarger hot water coils or plate heat exchangers. Conventional hot water tanks usedfor boilers or solar panels will not perform satisfactorily on the lower temperatureoutput from heat pumps.There is a significant difference between the US and European approaches to hot

water generation. Because of the dominance of water to air units in the US, it iscommon to use a specialized heat exchanger tapped into the refrigeration circuit called a de-superheater. This can produce modest amounts of hot water while theheat pump is heating (or cooling) but not at other times. In Europe, with air orwater-to-water heat pumps, it is perfectly possible to switch the heat pump at anytime to hot water generation. In particular, this allows the generation of hot water

xvi GEOTHERMAL HEAT PUMPS: A GUIDE FOR PLANNING AND INSTALLING

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00017___7682bda4a99c2f2ee274430884ff26aa.pdfin the summer when the heat pump is not being used for heating. Installers mustpay attention to local and national codes and practices related to domestic hot watersystems, particularly in respect of pressurized systems.As Lord Kelvin pointed out, heat pumps can be used for cooling and in fact

this application still dominates the world market in heat pumps. It is very easy fora heating heat pump to be fitted with a reversing valve to allow it to be used forwhat is termed active (or refrigeration based) cooling.While there is a case to bemade that ground source or water source heat pumps are one of the most efficientways of providing cooling for buildings, there are reservations as to the widespreadadoption of active cooling in countries where domestic cooling has not traditionallybeen required. It should be recognized that any form of active cooling can usesignificant quantities of electricity, and governments are concerned that unnecessaryadoption of active cooling will wipe out hard won gains in energy conservation andcarbon reduction. In climates that do not really require full-blown, active airconditioning, the use of passive cooling may be of benefit. This particularly appliesto water and ground loop systems where simply circulating cool water from thesource side of the heat pump through underfloor loops or fan coils can deliver a fewdegrees of cooling.This is referred to as passive cooling and is provided as an optionwith many European heat pumps. This allows the heat pumps to be optimized forthe heating cycle,with no engineering compromise being required to deliver reversecycle cooling.With these basics in mind, the reader should now be in a position to appreciate

the wealth of information contained in the body of this book.With the experiencethat the author brings, coupled to manufacturers data sheets and technical guides,it should be possible to embark on the design and installation of successful domesticheat pump systems.

Robin H. CurtisApril 2007

INTRODUCTION xvii

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00018___7ea329cf02c3d98619e9f4f313a47c67.pdfReferences

IPCC (Intergovernmental Panel on Climate Change) (2007) Climate change 2007:The physical science basis summary for policymakers, IPCC Secretariat, Geneva,Lund J.W., Freeston D.H., Boyd T. L. (2005) World-wide direct uses of geothermalenergy 2005, Proceedings of theWorld Geothermal Congress,Antalya,Turkey,April.Thompson,W. (Lord Kelvin) (1985) On the economy of the heating or coolingof buildings by means of currents of air, Proceedings of the Royal PhilosophicalSociety (Glasgow), vol. 3, pp. 269272.

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00019___fdc906b9e5f61b506e0fe826c178cfc1.pdfList of Acronyms andAbbreviations

ASSA Austrian Solar and Space AgencyAWP AWPWrmepumpen GmbH (heat pump producer)BW Brine/WaterCOP Coefficient of PerformanceEER Energy Efficiency RatioEU European UnionGMDW Golf Midi/Maxi ground/direct expansion (type code)GMSW Golf Midi/Maxi brine/water (type code)GMWW Golf Midi/Maxi water/water (type code)GWP Global Warming PotentialHSPF Heating Seasonal Performance FactorIPCC Intergovernmental Panel on Climate ChangeODP Ozone Depletion PotentialRECS Renewable Energy Certificate SystemSEER Seasonal Energy Efficiency RatiosUN United NationsWW Water/water

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00020___40446613f496d0b4221577d55791333f.pdf

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00021___a9cdd4c28776587f6ab29874dc5feec8.pdf1Reasons to Use a HeatPump

1.1 Environmental benefits

1.1.1 Our environment is in dangerOver millions of years, the ancient forests and plants of our planet have producedthe oxygen that we breathe today. The decaying plants and forests were swallowedup by the young Earth, and transformed over long periods of time into coal, oil andnatural gas.These are the fossil fuels that people burn today.During the burning process, the

oxygen store is consumed and carbon dioxide is produced again. Anotherphenomenon is the enormous increase of methane gas in the atmosphere.There areseveral causes for this: the excessive production and use of natural gas world-wide

Figure 1.1 Emissions that contribute to the greenhouse effect and climate changeSource: Professor D. Schnwiese, Institut fr Geophysik, Universitt Frankfurt/M

61%

9%

11%

15%

4%

1

2

3

4

5

1 Carbon dioxide2 Methane3 Chlorofluorocarbons4 Ground level ozone and upper atmospheric water vapour5 Nitrous oxide

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00022___da755e7ae9226e196bcb4def9cd30de7.pdfhas resulted in an increasing concentration ofmethane too.These gases intensify thenatural greenhouse effect and present a climate threat (see Figure 1.1). In addition,the environmental pollution and damage caused by leaks in oil and gas pipelines andby tanker spills must be considered.According to United Nations (UN) studies, the expected consequence is an aver-

age temperature increase of 1.5 to 6C in the next century. This is predicted to giverise to dramatic climate changes: increasingly frequent storms, hail and heavy pre-cipitation, as well as droughts and a rising sea level (see IPCC IntergovernmentalPanel on Climate Change report released in February 2007).The environmental pollution and damage caused by leaks in oil and gas

pipelines and by tanker spills must also be considered.

1.1.2 Tracking down the culpritHeating with fossil fuels is achieved mainly by burning oil and natural gas. Duringthe chemical process of combustion, considerable amounts of sulphur dioxide,nitrogen oxides, soot and other pollutants are emitted, causing acid rain, damagingforests and endangering our health.All types of combustion, including that with natural gas and biofuels, produces

carbon dioxide (CO2). This intensifies the greenhouse effect and leads to climatechange. Heating an average family home using oil produces some 6000 kilo-grammes (kg) CO2 each year, and using natural gas some 4000kg CO2. Domesticheating accounts for as much as 40 per cent of our CO2 emissions in central Europe.For this reason, new building codes are designed to limit primary energy con-

sumption.Heating with wood logs, wood chips or pellets is arguably CO2-neutral provided

that sustainable forestry is adopted, but still results in the emission of the pollutiondescribed above, as well as microparticles.

1.1.3 Heat pumps offer emission-free operation on-siteHeat pumps deliver heat without producing any on-site soot or other toxic exhaust.Depending on the heat source, heat pumps produce pollutant-free heating energyusing solar energy, environmental energy, geothermal energy or waste heat.So on the one hand you can store your white laundry in the heating room, cre-

ating another usable room, and on the other hand there are no pollutants whichcould harm your garden or backyard. Even your neighbours will be thankful foryour commitment to national and global environmental protection (see Figure 1.2).The leading heat pump manufacturers use only chlorine-free refrigerants with

zero ozone depletion potential.Depending on the mix of generating capacity on the grid, heat pumps generally

offer excellent overall CO2 emissions, i.e. as per the next figure with 50 per centhydropower. It is also worth pointing out that even with 100 per cent modern fossilpower generation there is an overall reduction in CO2 emissions compared to indi-vidual condensing boilers, thanks to the efficiency of todays power plants.Figure 1.3 shows how much on-site energy in kilowatt-hours per square meter

per year must be expended.This energy is the quantity the user requires to heat the

2 GEOTHERMAL HEAT PUMPS: A GUIDE FOR PLANNING AND INSTALLING

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00023___348fe9c6391f85e14a37d8f1603da682.pdfREASONS TO USE A HEAT PUMP 3

Figure 1.2 Emission comparison: typical single family house with 8.8kW heating demandNote: Electricity: 50 per cent emission free (i.e. hydropower); 50 per cent thermal power plant.Source: Institut fr Wrmetechnik TU Graz, Energiebericht der sterr. Bundesregierung 1990,actualised 12/1998.

CO2(kg

/Year)

Oil

boile

r

Nat

ura

lgas

boile

r Hea

tpu

mp

50% Thermal power plant

Figure 1.3 Energy demand for various heating systemsSource: GEMIS-VDEW

300

200

100

0

Oil

cen

tral

heat

ing

Gas

cen

tral

heat

ing

Hea

tpu

mp

heat

ing

232

197

70

KW/h

/m2

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00024___b72ca2ea578c8710b54c4e8d55dd1c1b.pdfrequired area (i.e. how many kilowatt-hours of electricity, litres of heating oil orcubic metres of natural gas).One kilowatt-hour of electricity is equivalent to approximately 0.1 litres of oil. It

is clear that heating with heat pumps requires significantly less energy than heatingwith gas or oil. The reason is that the heat pump draws up to 75 per cent of therequired energy from its surroundings.In Figure 1.4 the environmental impact of a heat pump is compared with that of

gas and oil boilers. The CO2 emissions from the (caloric) production of electricityare taken into account.

1.2 Operating costs

Depending on the efficiency of the heat pump, up to three-quarters of the requiredheating energy is drawn from the environment (without cost) when heating with aheat pump system.This environmental energy comes from the sun or in the case ofgeothermal systems with vertical loops from the ground. Heat pumps make use ofthe free renewable energy stored in air, water or the earth.With the help of a heatexchanger, the heat pump boosts the energy extracted from the environment to thetemperature level required for heating. In Figure 1.5, a typical cost comparison (forGermany) is shown. With a heat pump, you can utilize solar energy economicallyyear-round.


Figure 1.4 Comparison of environmental impact of heat pumps with oil or gas combustionNote: Comparison of the impact of various environmental influences. 1. Heat pump (CH): Swiss electricity;2. Gas: low-NOX, condensing boilers; 3. Oil: low-NOX.Source: AWP Zrich

600%

500%

400%

300%

200%

100%

0%Greenhouse effect

100a in to CO2equivalent

Visible smog (groundlevel ozone) in kgAeth-equivalent

1 12 3 2 3

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00025___f997949125741491b670e8510479a627.pdf1.3 Independence

The ambient energy sources of heat pumps solar energy stored in the air, waterand ground all exist crisis-free, right outside your own door. Considering theforthcoming impacts of limited oil supply, and the rapidly increasing demand for oil

REASONS TO USE A HEAT PUMP 5

Figure 1.5 Operating costs per year, residential house 175m2, heating capacity 9 kW, example Energie AG,09/2006

0 500 1.000 1.500 2.000 2.500 Euro

Propane

Heating oil (extra light)

Off-peak electricity

District heating

Natural gas

Pellets

Heat Pump = 3.0

Heat Pump = 3.8

Heat Pump = 4.2

2.206 Euro

1.910

1.722

1.488

1.328

1.322

742

1.091

524

002051001050

aibarAiduaSotsnot.nB0.63

narIotsnot.nB0.81

qarIotsnot.nB6.51

tiawuKsnot.nB8.31

setarimEbarAotsnot.nB3.31

aleuzeneVotsnot.nB8.01

aissuRotsnot.nB1.01

aibyLotsnot.nB3.5

airegiNotsnot.nB9.4

ASUotsnot.nB0.4

anihCotsnot.nB1.3

ocixeMotsnot.nB2.2

yawroNotsnot.nB2.1

dlrowotsnot.nB6.161

snotnoilliB

sraeyniegarevoC

.Y14

.Y86

.Y09

.Y571

.Y601

.Y201

.Y07

.Y22

.Y66

.Y93

.Y31

.Y71

.Y21

.Y9

5002srevreseRliO

Figure 1.6 Oil reserves in billion tons 2005Source: Bundesanstalt fr Geowissenschaften und Rohstoffe

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00026___ea56d175b1cbf3b6bb4460eeec8cf523.pdfand gas, it is easy to recognize that dangerous dependence on volatile foreignenergy sources is an additional risk factor (see Figure 1.6). Because of their efficientuse of local, ambient energy resources, heat pumps help to reduce dependence onimported fuel supplies.

1.4 Comfort

Heating with heat pumps offers the highest possible living comfort and ease ofoperation.The heat distribution systems commonly implemented with heat pumps,such as low temperature radiant floor and wall heating, guarantee a comfortableand healthy living climate. Low temperature radiant heat also minimizes overheat-ing and excessive air and dust turbulence. Reversible heat pumps can also cool ondemand during the summer. Heat pump heating systems generally operate quietly,automatically and are maintenance free. Fuel deliveries, disposal of ashes and chim-ney cleaning are all eliminated.

1.5 Security for the future

Heat pumps represent the most modern heating technology available. Today, heatpumps are no longer replacing just wood and coal heating, but also coke and cen-tral oil heating, and with increasing frequency even natural gas heating systems.Additionally, there is the question of whether or not we will still be able to afford

our heating systems in 20 years. The selection of a heating system should be a deci-sion for decades. Future-oriented consumers will undoubtedly arrive at oneconclusion: the heat pump. Even today, correctly implemented heat pumps can bethe heating system with the lowest operation costs.With each increase in fossil fuelprices, the cost of heating with heat pumps becomes even more competitive whencompared to oil, gas, or pellets. The savings will increase because with heat pumps,three-quarters of the energy remains free, even if electricity costs increase.


Figure 1.7 Supply of primary energy sourcesSource: Ochsner

Oil

Natural gas

Coal

Uranium

today Years

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00027___ead87498b2407881e2885b699589e7d1.pdfREASONS TO USE A HEAT PUMP 7

Figure 1.8 Development of oil priceSource: WTRG Economics

Figure 1.9 Growth of global population (in billions)Source: Ochsner based on UN-Population Division 97

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00028___b8a0e3a53ad06212cb396ccbe1266ca1.pdfThe energy resources of a heat pump are practically unlimited as far as quantity,availability and time are concerned. Figure 1.7 shows that resources such as oil andgas will become increasingly limited and expensive.Since the year 1900, the worlds population has increased by a factor of 3.5. The

global energy demand, however, has increased by a factor of 10. Today, 6.2 billionpeople inhabit the Earth by 2050 the population will grow to 9.1 billion (UN-Population Division,Average Assumptions).In developing countries, the energy demand is growing at higher than propor-

tional rates compared to population and gross domestic product (domestic, industryand trade). At current growth rates, Chinas demand for oil will exceed that of theUS (currently the largest consumer) within 10 to 15 years.

1.6 Non-flammability

Heat pumps heat by means of a thermodynamic cycle, without combustion andflames.This significantly reduces any chance of a dangerous accident.Additionally,most units operate only with non-flammable refrigerants.

1.7 Responsibility for the future

We do not want to upset the ecological equilibrium which belongs to our children.Today, we carry the responsibility for tomorrow. In the future, oil and gas will beurgently needed as raw materials for applications in which they cannot be replaced.They are too precious to waste on domestic heating.In addition, natural gas and oil imports burden the balance of payments of our

national budget, while environmental energy represents a domestic asset.

1.8 Ideal for low energy houses

Heat pumps are the ideal heating system for low energy houses in which only a min-imal heating capacity is required. Conventional heating systems are generally notavailable or technically or economically feasible for such low heating capacities.

1.9 Retrofit

Increasing energy costs, regulations or simply the breakdown of an existing boilermake a new investment necessary. Retrofitting a heat pump becomes more feasibleas new technologies permit flow temperatures of 65C. Furthermore, using air as asource is becoming more and more attractive as split units in particular offer a highcoefficient of performance (COP).Air is available anywhere as a heat source.


Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00029___1dd7a0d8f994324d99b2dde2eb011f7a.pdf1.10 Multiple functions

Heat pumps can also be used to cool in special configurations. With the provenincrease in summer temperatures, cooling will soon be necessary in more and moregeographical areas.Heat pumps used for domestic hot water heating can also be used to ventilate or

cool and dehumidify at the same time without additional investment or operationcosts.Heat pumps used for controlled dwelling ventilation can provide additional

heating or cooling using exhaust heat.

1.11 Public promotion

The installation of a heat pump is promoted by several authorities as an ecologi-cally and economically important technology. This support varies from subsidiesthrough the government, community and utilities to tax credits and reduced inter-est rates for credit financing.

1.12 Energy politics/laws

Heat pumps can be used in the most important end energy segments (see Figures1.10 and 1.11), substituting for fossil fuels and reducing emissions.Heat pumps are one of the few technologies that can lead to a significant reduc-

tion in CO2 emissions and thereby help to reach Kyoto Protocol goals. For example,the German Energy Conservation Act, European Union (EU) Buildings Directiveor the Australian Renewable Energy Certificate System (RECS) promote heatpumps through the placement of limits on primary energy consumption.

REASONS TO USE A HEAT PUMP 9

Figure 1.10 Space heating represents a significant portion of national energy consumptionSource: VEDW

MechanicalEnergy

39%

Lighting2% Space heating

32%

Process heating27%

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00030___79ab4b2e7554c3adfa140e88a6c8154e.pdf10 GEOTHERMAL HEAT PUMPS: A GUIDE FOR PLANNING AND INSTALLING

Figure 1.11 Heating and domestic hot water preparation are by far the largest energy consumers in privatehouseholdsSource: VEDW

Domestichot water

11%

Lighting2%

Electricdevices

8%Cooking

3%

Heating76%

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00031___904a0e395f1dbcd4b52b4af97dfa2f20.pdf2Theory of the Heat Pump

Principle of Thermodynamic Heating

The heat pump transforms thermal energy at a low temperature into thermalenergy at a higher temperature which is suitable for heating purposes. This occursin a closed-cycle process in which the working fluid is constantly undergoing achange of state (evaporation, compression, condensation and expansion).The heat pump draws stored solar energy from its surroundings the air, water,

or the ground and transfers this energy, plus the electrical energy used to operatethe cycle, in the form of heat, into a heating or water heating circulation loop.

The Heat Pump Cycle

2.1 The principle

As shown in Figure 2.1 and Figure 2.2, the heat pump draws about three-quartersof the required heating energy from the environment.

one part

3 parts 4 parts

Figure 2.1 Energy Flow DiagramSource: Building Advice Guide

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00032___289e7669c6ded883b94cd894a5990ff6.pdf2.2 The refrigeration cycle

Example of a heat pump refrigeration cycle with pressure and temperature valuesfor refrigerant R 134a, 1.4 kWth,A7/W50 (see Figure 2.3):

A7/W50 = input air at 7C, output water at 50C


Figure 2.2 Principle of Heat Pump OperationSource: BWP

Environmental heat 3/4 + Purchased energy, electrical 1/4 = Usable heating energy 4/4

2.3 Coefficient of performance

The coefficient of performance COP () indicates the amount of delivered heat inrelation to the drive power required.Therefore, a coefficient of performance of fourmeans that the usable thermal output is quadruple the required electrical input.Thecoefficient of performance is an instantaneous value. It depends on the design of theheat pump and the operating characteristics of the refrigerant. For a given heatpump the COP varies with the temperature of the input and the output. Typically,the COP is quoted at specified input and output conditions e.g. B0/W35 means aninput water temperature to the evaporator of 0C, and an output water temperaturefrom the condenser of 35C.

= COP =Delivered heat energy (kW)

electrical input to compressor (kW) =Environmental Energy + el.i.to.c.

el.i.to.c.

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00033___34677990c7a9dca23bb9c0a544872c1f.pdf2.4 Carnot Cycle

The heat pump cycle more or less reverses the (ideal) Carnot Cycle for a combus-tion engine. This means that the COP can also be calculated using the temperaturedifference between the heat source (evaporator) and the heat sink (condenser):

c = T/TTu = T/T

c = COP from Carnot (Carnot efficiency)

Tu = Temperature of environment out of which the heat is to be collected (specifi-cally, To evaporator temperature)

T = Temperature of environment into which the heat is distributed (specifically,condenser temperature)

T = Temperature difference between the warm and cool sides

(all temperatures given in absolute temperature, in degrees Kelvin, or K)

THEORY OF THE HEAT PUMP 13

Figure 2.3 Heat pump refrigeration cycleSource: Ochsner

T = 73.5C

T = 73.5C

p = 1.7 barp = 13.5 bar

Temp.rises

Temp.falls

Pressurefalls

Hot gas

FlowHeatingTVL=50C

ReturnHeatingTRL=45C

Air

Cond

ensa

tion

tem

pera

ture

53C

(Con

stant

pres

sure

)

(Con

stant

pres

sure

)

Suction gas Refrigerant vapour

Refrigerant liquid

Expansion valve

Cond

ense

rCompressor

Evap

orat

or

Evap

orat

ionte

mpe

ratu

reco

nsta

nt2

C

Pressurerises

Superheating(5K)

Subcooling(5K)

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00034___8d072a02cfe7ecea5bd976bef0fb6891.pdfExample 1: Temperature difference 50 K (simplified)

Example 2: Temperature difference 30 K (simplified)

In practice, ideal processes are not possible.The COP for an actual heat pump cycleincludes various losses and is therefore smaller than the theoretical value. Due tothermal, mechanical and electrical losses, as well as the power demand of the aux-iliary pump, the achieved COP is smaller than the Carnot Efficiency. As anapproximation, the actual COP can be taken as 0.5 the Carnot Efficiency.


Figure 2.4 The Carnot Cycle in the T-S diagramSource: Ochsner

T(K)

A

B

3 2

4 1

S0

T

Tu

Energy taken from environment:Area A

Drive power of compressor:Area B

Total delivered energy:Areas A + B

S = Entropy = Energy Content

4-1 Evaporation / 1-2 Compression (Temperature Increase)2-3 Condensation / 3-4 Expansion

%XAMPLE EC E%XAMPLE EC E

4U # +4 # + EC 4

4n4U n

TEMPERATURE DIFFERENCE DETERMINES THE COPIn all cases, the Coefficient Of Performance depends on the temperature differencebetween the heat source and the heat sink (see Figure 2.5).The smaller the requiredtemperature difference, the more efficiently and economically the heat pumpoperates because the compressor has to do less work to lift the temperature of therefrigerant gas.Therefore, optimization of the entire system is extremely important.The COP is also dependent on other factors such as the temperature differences

within the heat collection and distribution systems. These effects should be takeninto account when comparing manufacturer and test data.

SEASONAL PERFORMANCE FACTOR (ANNUAL EFFICIENCY)The annual efficiency indicates the total amount of heating energy delivered in anannual heating period in relation to the total electrical power consumed in the same

4U # +4 # + EC 4

4n4U n

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00035___d9d029a6f5694ff636c1a9fce9992691.pdfperiod. Furthermore, working efficiencies can be defined for the heat pump aloneor for the complete heating system. The average COP over a heating (or cooling)season is often referred to as the Seasonal Performance Factor (SPF). SeeVDI 4650.

Calculation of Seasonal Efficiency Ratios (SEER) Heating Seasonal Performance Factor (HSPF)

In North America see ANSI/ASHRAE Standard 1161995 (RA 2005) see Figure 15.20

2.5 Working fluid/refrigerant

For working fluid (refrigerant), suitable substances are those with large specific heatcapacities and which evaporate at low temperatures.Today, only chlorine-free refrigerants are permitted. These are non-ozone

depleting refrigerants (Ozone Depletion Potential, ODP = 0). R 134a, R 407C,R410A,R404A and propane fulfil these conditions. In domestic applications,R 134a,R 407C and other blends are often used as they are both non-flammable and non-toxic.To provide compressor lubrication, biodegradable esther oil is used in modernheat pumps, further minimizing any potential environmental impact.Even in systemswith direct vaporization, the theoretical possibility of environmental damage ispractically eliminated.Heat pumps with inflammable refrigerants (e.g. propane) are subject to numer-

ous safety guidelines and are therefore restricted with respect to installationlocation.Systems with CO2 as refrigerant are still in development, mainly due to the high

pressure which this technology requires.


Figure 2.5 Coefficient of performance with respect to temperature differenceSoure: BWP

Coefficient of Performance

Temperature Difference T

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00036___74fd1305e116557a76e09c2a30526d51.pdfMost of the heat pumps that are being discussed here have their refrigerantinstalled during the manufacturing process as with domestic refrigerators. It istherefore extremely unlikely that the refrigerant will be lost to the atmosphere aslong as care is taken when the heat pump is disposed of. However, concerns overthe large losses of refrigerant that occur in other sectors means that there areincreasing requirements on heat pump installers to be fully aware of, and trained in,controlling potential refrigerant losses.

2.6 Enthalpy-pressure diagram

The enthalpy, h, is a measure of energy contained in a substance.The progression ofthe ideal cycle follows the path 1 2 2 3 4. The vapour dome shows the separationbetween the liquid phase (left), unsaturated-vapour (middle) and super-heatedvapour phases (right) (Figure 2.6).In an ideal cycle, the refrigerant behaves as an ideal gas and all processes occur

without losses (isentropic).In real cycles, the compression does not occur along the line 12 (isentropic), but

due to losses to a somewhat higher compression temperature at the same saturationpressure.Therefore,more compression work is required in order to achieve the sameend pressure and saturation temperature.The energy transferred in the cycle can betaken directly as the enthalpy differences from the h, lg p-diagram (Figure 2.6).TheCarnot Efficiency can be quickly determined using these values:

c = h2 h3/h2 h1

For actual processes, the COP may be determined as:

c = h2* h3*/h2* h1*


Figure 2.6 Determination of the COP in the h, lg p-diagramSource: Ochsner

Example R 134a

Pressure p

30

10 Bar

5

3

1

0,5

0,3

200 250 300 350 400 kJ/kg

Enthalpy h

100C

80C

60C

40C

20C

0C

-20C

55C 3* 2 2 2*

1 1*44*

x=0

-2C

x=1

3

h =h3* 4*h =h3 4 h1

h1* h2*h2

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00037___2bc0ae90644748030318715bf295e7d7.pdfCycle with super-heating and sub-cooling:

4* 1 Evaporation, absorption of vaporization energy h1 h41 1* Super-heating of intake gas1* 2* Compression to set compression temperature (super-heated refrigerant

vapour)2* 2 Cooling to saturated vapour temperature, release of super-heating energy

h2* h22 3 Condensation, release of vaporization energy, h2 h33 3* Sub-cooling of fluid3* 4* Expansion in the unsaturated vapor phase; no energy release

(transformation from sensible to latent heat)

Cycle without super-heating and sub-cooling:

4 1 2 3 4

2.7 Heat pump cycle with injection cooling

In order to increase COP and heating capacity and to make a higher temperature-lift possible, heat pumps can be designed with injection cooling, e.g. air source heatpumps with vapour-injection cooling can supply temperatures up to 65C even incoldest climates.


Figure 2.7 Refrigerant Cycle with Enhanced Vapour InjectionSource: Copeland GmbH

m Mass flow, main evaporatori Mass flow, vapor injection,m + i Mass flow, condenser

Higher mass flowachieves higher heat output

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00038___290e549379d354c45a92118105cb61db.pdf3Heat Pump Types

Heat pumps can be categorized according to:

function:heating, cooling, domestic water heating, ventilation, drying, heat recovery etc.

heat source:ground, ground water, air, exhaust air etc.

working fluids heat source/heat distribution:brine/water, water/water, direct-expansion/water, air/water, air/air etc.

unit construction:compact, splitinstallation location (indoor, outdoor)compression heat pumpabsorption heat pumpdrive power (electric, gas)number of compression stagesetc.

Air conditioners and refrigerators are also heat pumps,making use of the cold sideof the heat pump cycle.The following is a short summary of the standard electrically driven, vapour

compression type heat pumps which are available for applications in single andmultiple family homes, and in industrial, commercial and community buildings.Dueto the diverse range of manufacturers construction methods, this should only beconsidered as an overview.

3.1 Brine/water, water/water heat pump

APPLICATIONSBoth brine/water and water/water heat pumps are used for monovalent heatingoperation (usually ground source), as well as cooling, heat recovery and domestic

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00039___c48a78b3fcd9abfbed59dfc8da0b2c2b.pdfhot water production. Water/water (WW) heat pumps are used with an availablewater source, e.g. aquifer-fed borehole, lake, or water body. Brine/water (BW) heatpumps are used in closed loop ground coupled installations.The brine refers to thefact that these systems can run at low source temperatures, often below freezing so it is necessary to have an antifreeze solution in the source water circuit.This wastraditionally a brine solution, but today is usually a water/antifreeze mixture.

CONSTRUCTION/HOUSINGBrine/water and water/water heat pumps are generally compact units for indoorinstallation, and consist of the following components (see Figures 3.2 and 3.3).

3.1.1 Refrigeration cycleGenerally a fully hermetic compressor (piston or scroll for extremely quietoperation) with built-in, internal overload protection is used in these heat pumps.Stainless steel flat plate heat exchangers or other types like shell and tube or coaxialare used for the evaporator and condenser.Other items in the refrigerant cycle are the expansion valve and possibly a sight

glass, accumulator and a filter/drier. The refrigeration cycle (Figure 3.1) should befully insulated against thermal losses and prevent condensation inside the heatpump. For heating/cooling reversible operation, see Figure 10.3.

HEAT PUMP TYPES 19

Figure 3.1 Refrigeration cycle of a brine/water or water/water heat pumpSource: Ochsner

Flow DiagramRefrigeration Cycle: Brine/Water and Water/Water

Low PressureSafety Switch

Compressor

High PressureSafety Switch

Conde

nse

r

Evapo

rato

r

Filter-Dryer

SightGlass

Expansion Valve

RefrigerantReciever

WNA Heat Delivery System WQA Heat Collection System VLH Heating Supply VLQ Collector SupplyRLH Heating Return RLQ Collector Return

3.1.2 RefrigerantChlorine-free working fluids which do not cause damage to the ozone layer and havelow global warming potential are to be used.With non-flammable refrigerants (R407C, R 404A, R 410A, R 134a etc.), installation in any location is possible.Inflammable refrigerants (R 290 and others) are uncommon due to safetyrequirements.

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00040___deea8ec6c848255a15e323084958ff9a.pdfThe non-flammable safety refrigerants also enable use of biodegradable,synthetic refrigerant oil (esther oil).

3.1.3 Electrical components and controllerElectrical components and the controller are either integrated or externallymounted, depending on manufacturer and model. Control of the heating system iscommonly integrated. A micro-processor driven heating controller should beweather-and-load-dependent. The heating curve as well as many functions andprogrammes can be individually set.

3.1.4 Safety measuresMotor protection relays, high and low refrigerant pressure switches, and a frostprotection thermostat are used.

3.1.5 DisplayThese vary considerably with heat pumpmanufacturers depending on the simplicityor complexity of the controller. Typically, any or all of the following will be found:Temperature display for heat pump supply and heat source supply, illuminatedoperation switch, operation-hour counter,warning indicators for high-pressure, low-pressure, frost-protection, motor-relays and more, and reset button.

HEATING AND BRINE ACCESSORIES, HOT WATER TANKIn numerous models, the heating system circulation pump (including a check valve)and/or the source side (brine) circulation pump are integrated into the heat pumpcasing to simplify installation andminimize the space requirements. In some compactunits the domestic hot water tank is also built in.


Figure 3.2 Water/water heat pump Golf series (midi): (a) closed and (b) open unitSource: Ochsner

(a) (b)

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00041___3d8ebbff115824a14168a30b8debf38a.pdfIn modern domestic heat pumps attention will have been paid to minimizing noiseand vibration arising from the compressor operation. This will take the form ofacoustic shielding in the casing, together with vibration isolation of the compressorfrom the casing. The use of flexible hydraulic connections and anti-vibration feetfurther reduce any noise and vibration.

3.2 Direct expansion/water heat pump

Direct expansion heat pumps do not have an intermediate heat exchanger on theirsource side. Instead, a loop of suitable pipe containing the refrigerant and lubricantis put in direct contact with the ground or water body. The compressor operationcirculates the refrigerant directly around this loop thus eliminating the heat transferlosses associated with the intermediate water/DX heat exchanger found inconventional water source heat pumps. There is also no need for a source sidecirculation pump the compressor undertakes this role. However, care has to be

HEAT PUMP TYPES 21

Figure 3.3 Brine/water heat pumpSource: AWP

Figure 3.4 Brine/water heat pump with integrated hot water tank,Source: Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00042___20fb95719bd73f5a1271312fcf1cda0d.pdftaken to ensure that the DX loops are totally sealed, corrosion resistant, and thatthe lubricant is adequately circulated to meet the needs of the compressor.Environmental authorities in different countries are enforcing special standards

on these systems depending on local concerns over increasing volumes of refrigerantbeing installed in vulnerable ground loop arrays. For example, there are double-walled continuous ground loops and solenoid valves that are automatically closedwhen the compressor is not operating.

APPLICATIONSDirect expansion/water heat pumps are used for monovalent heating operation (withground source) and for domestic hot water preparation.

CONSTRUCTION/HOUSINGInstallation of these compact units is unrestricted indoors if non-flammablerefrigerants are used (see DIN 8901).

3.2.1 Refrigeration cycleGenerally, a fully-hermetic compressor (piston or scroll for extremely quietoperation) with built-in, internal over-load protection. Usually stainless steel flatplate heat exchanger for condenser.Collector tubing for evaporator loop.Expansionvalve. The refrigeration cycle should be fully insulated against thermal losses andprevent condensation. The refrigerant receiver should be generously dimensioned(see Figure 3.5).

3.2.2 RefrigerantChlorine-free working fluids which do not cause damage to the ozone layerand with low global warming potential are to be used. With non-flammable


Figure 3.5 Heat Pump cycle of Direct Expansion system (simplified)Source: Ochsner

WNA Heat Delivery SystemVLH Heating SupplyRLH Heating Return

Flow DiagramRefrigeration Cycle: Direct Expansion/Water

Con

dense

r

Eva

pora

tor

RefrigerantReciever

SolenoidValve

Filter-Dryer

SightGlass

Expansion Valve

High PressureSafety Switch

Low PressureSafety Switch

CompressorSuction

LineAccumulator

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00043___d7a8b8b6ab12ab18d73c76c4916404b3.pdfrefrigerants (R 407C, R 404A, R 410A, R 134a etc.), installation in any location ispossible.The non-flammable safety refrigerants also enable use of biodegradable,

synthetic refrigerant oil (esther oil).Use of inflammable refrigerants (R 290, and others) is restricted to outdoor

installation. For combination with CO2 loops, see Chapter 14.8.

3.2.3 Electrical components and controllerElectrical components and the controller are either integrated or externallymounted, depending on manufacturer and model. Control of the heating system iscommonly integrated. A micro-processor driven heating controller should beweather and load dependent. The heating curve as well as many functions andprogrammes can be individually set.

3.2.4 Safety measuresMotor protection relays, high and low pressure switches.A solenoid valve should beincluded which in the event of collector damage automatically closes to preventrefrigerant in the heat pump from draining into the ground.

3.2.5 DisplayThese vary considerably with heat pumpmanufacturers depending on the simplicityor complexity of the controller. Typically, any or all of the following will be found:Temperature display for heat pump supply and heat source supply, illuminatedoperation switch, operation-hour counter,warning indicators for high-pressure, low-pressure, frost-protection, motor-relays and more, and reset button.

HEATING ACCESSORIESIn numerous models, the heating system circulation pump (including check valve)is integrated into the heat pump and is operation ready.Figure 3.6 shows a direct expansion/water heat pump and the separate multi-

function unit Europa for domestic water heating and ventilation.

3.3 Direct expansion/direct condensation heat pump

In this variation of the direct expansion system, the distribution of heat is achieveddirectly using the refrigerant, e.g. in a radiant floor heating system. The condenser,like the evaporator, is composed of seamless, plastic-sheathed copper tubing. Thelatent condensation energy is released at a constant temperature.Instead of individual room control, zone control of the individual loops only is

possible. Careful attention must be given to the sizing and quality of copper tubing,as well as the other components. Obviously, considerable care has to be taken incarrying out the load side installation in order to prevent loss of refrigerant due toleaks or damage.

HEAT PUMP TYPES 23

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00044___0155c1ea4c941bd4f47e54cefa67e956.pdf3.4 Air/water heat pump split units

APPLICATIONSAir/water heat pumps use outside air as their heat source and are mostly operatedin bivalent heating systems, as well as for cooling, heat recovery and domestic hotwater preparation. They are particularly well suited for retrofit and renovationapplications (see Chapter 14.1).

CONSTRUCTION/HOUSINGThe indoor unit contains the substantial components and is fitted indoors, protectedfromweather and freezing temperatures.The outdoor unit is connected to the indoorunit via refrigeration lines. Through the elimination of air ducts, extremely quiet,energy efficient fans are made possible (see Figure 3.7).

3.4.1 Refrigeration components indoor unitGenerally a fully-hermetic compressor (piston or scroll for extremely quietoperation) with built-in, internal overload protection is used in these heat pumps.Stainless steel flat plate heat exchangers are used for the condenser.Expansion valve,weather-dependent defrost mechanism preferably hot gas.The refrigeration cycleshould be fully insulated against thermal losses and prevent condensation.Designs with vapour-injection cooling are suitable for use to 65C flow

temperature.

3.4.2 Refrigeration components outdoor unitCopper-tube aluminium finned evaporator. For quiet operation an axial fan with low


Figure 3.6 Heat Pump Direct Expansion/Water with Buffer Tank and Hot Water TankSource: Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00045___8302fbaea579587e1c125162dfca22cc.pdfspeed should be used. Split systems allow for the use of large, high capacityevaporators and quiet, slow rotating, energy efficient fans.Follow manufacturer guidelines for the connection of the units.

3.4.3 RefrigerantChlorine-free working fluids which do not cause damage to the ozone layer and withlow global warming potential are to be used.With non-flammable refrigerants (R 407C,R 404A, R 410A, R 134a etc.), installation in any location is possible. Inflammablerefrigerants (R 290 and others) are uncommon due to safety requirements.The non-flammable safety refrigerants also enable use of biodegradable, syn-

thetic refrigerant oil (esther oil).

3.4.4 Electrical components and controllerElectrical components and the controller are either integrated or externallymounted, depending on manufacturer and model. Control of the heating system iscommonly integrated.Amicro-processor driven heating controller should be weatherand load dependent. The heating curve as well as many functions and programmescan be individually set. An electronic controller for the defrost mechanism isgenerally provided. Demand activated defrosting increases system performance.

3.4.5 Safety measuresMotor protection relays, high and low refrigerant pressure switches, and thermostatfor defrost control.

3.4.6 DisplayThese vary considerably with heat pumpmanufacturers, depending on the simplicityor complexity of the controller. Typically, any or all of the following will be found:

HEAT PUMP TYPES 25

Figure 3.7 Air/Water Heat Pump (Split-Configuration)Source: Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00046___fa4635f10405f14c8f686bc96e6373a6.pdfTemperature display for heat pump supply, illuminated operation switch, operation-hour counter, warning indicators for high-pressure, low-pressure, motor-relays andmore, and reset button.

3.5 Air/water heat pump compact units, indoorinstallation

APPLICATIONSAir/water heat pumps use outside air as their heat source and are mostly operatedin bivalent heating systems, as well as for cooling, heat recovery and domestic hotwater preparation.

CONSTRUCTION/HOUSINGCompact unit suitable for indoor installation (see Figure 3.8).

3.5.1 Refrigeration cycleGenerally a fully-hermetic compressor (piston or scroll for extremely quietoperation) with built-in, internal over-load protection. Copper-tube aluminiumfinned evaporator, axial fan for silent operation and short ducts, otherwise radial fan,defrost mechanism (preferably hot-gas), drain pan (preferably heated), stainless steelplate heat exchanger for condenser, expansion valve.The refrigeration cycle shouldbe fully insulated against thermal losses and prevent condensation.Designs with vapour-injection cooling are suitable for up to 65C flow

temperature.

3.5.2 RefrigerantChlorine-free working fluids which do not cause damage to the ozone layer and withlow global warming potential are to be used.With non-flammable refrigerants (R


Figure 3.8 Air/water heat pump for indoor installationSource: AWP

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00047___04e32b6885ba3e95d02539c33391b104.pdf407C, R 404A, R 410A, R 134a etc.), installation in any location is possible.Inflammable refrigerants (R 290 and others) are uncommondue to safety requirements.

3.5.3 Electrical components and controllerElectrical components and the controller are either integrated or externallymounted, depending on manufacturer and model. Control of the heating system iscommonly integrated. A micro-processor driven heating controller should beweather and load dependent. The heating curve as well as many functions andprogrammes can be individually set. An appropriate control device for the defrostfunction is necessary. Demand activated defrosting increases system performance.

3.5.4 Safety measuresMotor protection relays, high and low refrigerant pressure switches, and thermostatfor defrost control.

3.5.5 DisplayThese vary considerably with heat pumpmanufacturers depending on the simplicityor complexity of the controller. Typically, any or all of the following will be found:Temperature display for heat pump supply, illuminated operation switch, operation-hour counter, warning indicators for high-pressure, low-pressure, motor-relays andmore, and reset button.

3.6 Air/water heat pump compact units, outdoorinstallation

Figure 3.9 shows that compact outdoor units can be installed in any open location.

HEAT PUMP TYPES 27

Figure 3.9 Air/water heat pump outdoor setupSource: Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00048___2f315eb14f31409b82c31bf6326cac37.pdfAll components of the refrigeration cycle are integrated into the unit, so no air ductsare required. The housing must provide protection against weather elements.The connection to the heating system in the building consists of two insulated

pipes for the supply and return.These are to be installed underground with the heatpump power supply and control cable. Noise emissions are dependent upon sizing,construction and speed of the fan.Large, slow rotating fans operate quietly, insulationpanels further reduce noise. Followmanufacturer instructions regarding orientation.The defrost function for outdoor temperatures to approximately 16C is usuallyachieved with hot gas reverse cycle.Designs with vapour-injection cooling are suitable for up to 65C flow

temperature.

3.7 Domestic hot water/heat pumps air source,compact units

CONSTRUCTIONThese are supplied as fully integrated compact units, normally as exhaust air heatpumps with a 200300 litre hot water storage tank. All components such as thecompressor, condenser, evaporator and controller are integrated into the unit (seeFigures 3.103.13).

3.7.1 Refrigeration cycleFull-hermetic compressor, finned evaporator, axial or radial fan.The air intakes andexhaust can be placed in different locations.Air ducts up to 20 metres in length areacceptable (for radial fan). Condenser located in tank, in heat pump together with


Figure 3.10 Multi-Function Unit Europa 312 with Tiptronik E (temperature display, illuminated operationswitch). With the Tiptronik, all temperatures, operating conditions and parameters are displayed on an LCDdisplay. A hot-gas defrost mechanism enables operation at any outdoor temperature. Ventilation isindependent of heat pump compressor operationSource: Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00049___448809f0849f834f0c15a83187e0a4dd.pdffeed pump or external. Optional defrost mechanism (hot-gas) for operation at alloutdoor temperatures.

3.7.2 RefrigerantUsually, environmentally friendly, chlorine-free and non-flammable safetyrefrigerant R 134a with biodegradable esther oil is used.

HEAT PUMP TYPES 29

Figure 3.11 Section: Domestic Hot Water Heat Pump with Condenser-Coil and Heat Exchanger for optionalHeat sourceSource: Ochsner

Figure 3.12 Air/Water Heat Pump Compact Unit AWP/ALKOSource: AWP

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00050___ca49a597b35bfa1fe98635365f6d9254.pdf3.7.3 Electrical componentsThe most sophisticated units offer the following functions: fully automatic defrostcontrol, programmable heat-up function, auxiliary electric element, Legionellafunction for thermal water treatment on demand, use of off-peak power, independentfan function for ventilation, diagnostic display, and many more.

Auxiliary heating with external boiler:For configurations with tanks with built-in heating coils, alternative water heatingwith auxiliary separate boiler or solar pannel is possible.

Auxiliary electrical element:Many units have an electrical element (wet or dry) for elevated hot water demandand back up.

3.8 Domestic hot water heat pump air source,split units

With split domestic hot water units, external domestic hot water storage tanks areused.A built-in feed pump will circulate water from the heat pump through the hotwater tank. In this way, existing tanks of any model or capacity can be used(advantage: desired storage volume).Heat pumps with ca. 2kW capacity can be usefully combined with tanks from 200

to 500 litre volume. Units with ca. 5kW capacity can be used for commercial andindustrial applications with 1000 to 2000 litre storage volume. There are split heatpumps which stand next to the tank and others are mounted directly on to the tank(see Figures 3.14 and 3.15).


Figure 3.13 Section: Domestic Hot Water Heat Pump with Loading-Pump and Heat Exchanger for optionalHeat sourceSource: AWP

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00051___c82223a1ca4b1b59593c3d289b1b19a4.pdfHEAT PUMP TYPES 31

Figure 3.14 Split unitSource: Ochsner

Figure 3.15 Insert heat pumpSource: Thermo Energie

Figure 3.16 Split unit with internal flat plate heat exchangerSource: Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00052___6a086f1d6cd06c1ba8a059ebacfc7169.pdfAdditionally, split units with internal flat plate heat exchangers are available(Figure 3.16).

3.9 Ground/water heat pump domestic hot waterheat pump ground source, split units

Ground source split units use heat stored in the ground (Figure 3.17).


Figure 3.17 Module mini + ground loopSource: Ochsner

3.10 Air/air heat pump ventilation

Heat pumps are also found in controlled dwelling ventilation applications. Thisenables an increase in heat recovery from the exhaust air and can even allow forcooling of selected rooms. For these applications, various units are used.The air/airheat pumps have a full-hermetic compressor, finned heat exchanger for evaporatorand condenser, as well as an expansion valve and necessary safety mechanisms.The control of the unit is achieved with a simple room and supply air thermostat

or complex electronics. Figures 3.18 and 3.19 show ventilation heat pumps fromdifferent firms.

3.11 Exhaust-air heat pumps, additional designs

There are various other designs on the market which use heat from exhaust air forheating and for water production.Hydronic systems as well as air ventilation is used for heat distribution.Direct electric heating is normally used as an additional heat source, but this may

result in increased heating costs.

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00053___fb46602b7551c568f659e7471000f299.pdf3.12 Heat pumps for air heating/cooling

Air-based heating systems are common in America and Southern Europe. In thesesystems the heat distribution via the heat pump occurs using air ducts, not using ahydraulic system (see Figure 3.20).

HEAT PUMP TYPES 33

Figure 3.18 Controlled dwelling ventilation with kwl-centreSource: Helios

Figure 3.19 Controlled dwelling ventilation, auxiliary heating and cooling Europa 122Source: Ochsner

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00054___a1ea23ae6cf3de1ea640fb8b4a3a114e.pdf34 GEOTHERMAL HEAT PUMPS: A GUIDE FOR PLANNING AND INSTALLING

Figure 3.20 Residential GeoExchange SystemSource: GeoExchange

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00055___f36f967590c89aea58886d32006549cf.pdf4Complete System Planning

4.1 Planning a heat pump heating system

Figure 4.1 depicts a heat pump heating system, consisting of a heat source (HS), aheat pump (HP) and a heat delivery system (HD).

Figure 4.1 Heat pump system heating functionSource: DIN

Heating CapacityCollection Capacity(Environmental Energy) Drive Power

HS HP HD

Figure 4.2 Heat pump system cooling function Cooling function (see Chapter 10)Source: DIN

= Cooling Capacity(Environmental Energy)Heat Rejection(Heat sourcebecomes heat sink)

Drive Power

HS HP HD

For system planning all components must be designed to interact optimally, inorder to ensure the highest level of performance and reliable operation. Criticaldesign data should be supplied in manufacturers data sheets, and the system shouldadhere to quality control standards and installation recommendations also found inthe manufacturers technical guide.

Terminology: For instance water/water means heat source water and hydronicheat delivery.

Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00056___95d0c6e2df40c27d3b891d8325d7bd04.pdf4.2 Heat source selection

As a rule, the heat source with the highest temperature levels should be selected(Figure 4.3).This ensures the highest possible coefficient of performance and therebythe lowest operation costs.

WATERIf groundwater is available at a reasonable depth and temperature, at acceptablequality and in sufficient quantity, the highest COP can be achieved. The bestgroundwater heat source system is an open system and may require approval.Regulations concerning the use of groundwater resources differ from country tocountry and region to region. Attention must be paid to these local require-mentsand regulations before an open loop groundwater system is installed and operated.

If groundwater is not available, the ground heat source may be an option.

GROUND (BRINE)If the use of groundwater is not available, the ground can function as an efficient,effective thermal storage medium with a relatively high temperature level. If asufficient surface area is available, horizontal collectors offer the most cost effectivesolution (approval may be required). If space is limited, vertical loops usinggeothermal energy are an effective solution.These heat sources are closed systems,meaning that the brine (i.e. antifreeze solution) stays within the buried tube system.Heating and cooling options are possible.

GROUND (DIRECT EXPANSION)In direct expansion systems, the warmth stored in the ground is absorbed directlyby the working fluid (refrigerant). This results in an increased coefficient ofperformance. Horizontal collectors are mainly used with this system.

AIRIf groundwater or ground source systems cannot be used, air as a heat source isavailable practically anywhere. These systems are particularly suitable for retrofitsor in combined operation with another heat source (i.e. bivalent operation).Heatingand cooling options are possible. (For details on all heat sources, see Heat SourcePlanning Tips.)

4.3 Heating system selection

In this book hydronic heat distribution systems are described.

Determination of the maximum heating supply temperatureAs a rule, the lower the heating system temperature, the higher the coefficient of

performance of the heat pump and the lower the heating costs. In order to achieve


Geothermal_Heat_Pumps_A_Guide_for_Planning_and_Installing/1844074064/files/00057___ab30817f354ff78e90b58b57f6cf217d.pdfthis, the largest possible surface area for heat transfer must be selected. Ideal for thiscriteria are low temperature rad

geothermal heat pumps a guide for planning and installing

Documents