about heat pump technology

About Heat Pump Technology

Heat Pumps are widely used all over the world to heat water.

What is a Water Heat Pump?

A heat pump is a device that uses a compression vapour cycle, similar to that used in

fridges and air conditioners to heat up some sort of fluid such as water. There are two

main types of Heat Pumps – air to water and water to water. We will focus on air to

water Heat Pumps. Simply put, the heat found in the air is transferred to the water

through three key components – an evaporator, a condenser and a pump. The Heat

Pump is therefore mounted in a well ventilated area where the heat exchange process

can take place. Heat pumps are used in domestic, commercial and industrial

applications and are accepted worldwide as the number one water heating technology

(According to the French conference on energy efficiency). Heat Pumps are common

in Europe, Asia and the Americas as energy efficient water heating devices. Due to

their higher initial installation cost, they have not been as widely used on the African

continent.

The following pictures show what a Heat Pump looks like in various sizes:

Industrial Water

Heat Pump

Commercial

Water Heat

Pump

Domestic Water

Heat Pump

How does a Water Heat Pump Work?

A refrigerant fluid is pumped around in a circuit where it evaporates on one side of

the circuit and condenses at the other. Evaporation absorbs heat whilst condensation

releases heat. In a heat pump, heat is absorbed into the refrigerant fluid by the

evaporator at one side of the circuit, the fluid is pumped around to the other side of

About Heat Pumps, © Lemay Projects CC

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the circuit where the absorbed heat is released in the condenser. To most people heat

pumps will look very similar to an air-conditioning or refrigeration units because they

are very nearly identical, with the only difference being the roles of the condenser and

evaporator are used for different functions.

What are the Benefits of using Water Heat Pumps?

While the product does have some draw-backs which are listed below, the fantastic

advantage they do have is their ability to produce heating power at a fraction of the

cost of other technologies. Many studies and comparisons have been done to show the

energy saving capability of the product. In most of these studies the savings average

at between 60 and 70%. A recent study commissioned by Eskom was carried out by

the University of the North West which found the same overall result. Water Heat

Pumps although not a new technology have been identified as one of the foremost

products needed worldwide for energy saving. The following table shows the Pro's

and Con's of Heat Pumps:


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Pro's Con's

75% Energy Savings Achievable Operational noise level

Well established technology Higher initial capital outlay compared to

other water heating systems

Simple installation in either a new

application or retro-fit.

Needs well ventilated area

Low maintenance required Operation in extremely cold

environments (<-10˚C) problematic

Not dependant on the weather for

operation

Calcium build-up in water can lead to

extra maintenance

Good return on investment Not well established in South Africa

Cold air as a bi-product

Small installation foot print

Maintenance on Heat Pumps

A maintenance table below describes the measures that need to be taken to ensure

long life and maximum efficiency. The table should be used as the basis for any

maintenance schedules that need to be compiled and given to the maintenance staff.

The typical lifespan of a Heat Pump should be in excess of ten years and although

very little maintenance is required, regular checks should prevent possible damage to

the unit and prolong the life of the Heat Pump. Typical maintenance staff might

comprise of plumbers, electricians and air conditioning professionals. The only

addition to the list of maintenance staff when compared with electric boilers (geysers)

is that of an air-con technician.


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As can be seen in the above table, specialised attention is only required every 20,000

hours and this is typically done by an air conditioning professional. All other

maintenance must be undertaken as would be normal with current electric boilers.

Heat Pump Gas Specifications

Heat Pumps require a refrigerant to complete the vapour compression cycle. The

Deron Heat Pumps that are installed by Light and Sensor use R417A which is a

blended gas. It is directly interchangeable with R22 as it is considered the replacement

gas for R22. In South Africa, R417A is less commonly used and more expensive than

R22 or R134a. Although it is the choice of most manufacturers, Heat Pumps can be

run on either of these gasses. R417A can be interchanged with R22 if not available,

however under normal conditions, the need to re-gas or change gas is not necessary.

The gas should not need replacing during the lifespan of the unit in most instances

and if the need arises to do this, we recommend R417A be used. Although R134a can

also be used with some initial modification to the Heat Pump, it will change the

specifications of the Heat Pump unlike R22! Typically, R134a is only used when

higher than normal tank temperatures are required. We do not recommend this as it is

not common and not necessary. The following table shows the comparative

differences between R417A and R134a.


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No. Name:Chemical Formula

or % mass mixture:O.D.P.:

G.W.P.:

20; 100; 500yrs

Safety

Classification:

R134a Tetrafluoroethane C.F3.C.H2.F 0.0 3,300; 1,300; 400 A1

R417A HFC Blend HFC-125 (46.6%)

HFC-134a (50%)

HC-600 (3.4%)

0.0 4,400; 2,200; 700 A1/A2

O.D.P. referenced to Ozone Depletion Potential of CFC-11 (i.e. O.D.P. of

CFC-11 = 1.0).

G.W.P. referenced to the absolute global warming potential for CO2 using time

horizons of 20, 100 and 500 years. The bold figures refer to the 100 year time

horizon commonly used as the inventory standard. Calculated GWP values

for refrigerant blends have been rounded to the nearest 100.

SAFETY GROUP CLASSIFICATIONS as noted in AS 1677 part 1 are

indicated by alphanumeric characters (e.g. A1, A2, B3 etc). The capital letters

A or B indicate lower or higher toxicity respectively and the numeric value

refers to the refrigerant’s flammability (the number 1 being no flame

propagation and 3 being higher flammability).

Comparison with Other Existing Technologies

There are six main technologies used worldwide for water heating; Electric Boilers

(Geysers), Coal Boilers, Oil Boilers, Liquefied Gas, Solar Electric and Heat Pumps.

The table below shows the six types of technology compared. This information in the

table has been extracted from one particular report compiled in China. There are

numerous reports that compare water heating technologies, most of which come to the

conclusion that Solar Water Heaters and Heat Pumps are by far the most energy

efficient. Unfortunately Solar Water Heaters do not have a good commercial

application as they require a large amount of space at a high cost.


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Heating

Type

Calorie /

kWh

Energy /

Perf.

Ratio

Unit Price

Required

Energy /

ton of

water

Required

Cost / ton of

water

Labour Cost Coverage

Annual

Operational

Cost

Coal

Boiler

4000kcal/kg 40% $0.08/kg 25.10kg $2.32 $5,128 20m3 $12,641

Oil Boiler 8429kcal/kg 80% $0.6/l 6.40l $3.84 $5,128 20m3 $19,141

Liquified

Gas

10800kcal/kg 73% $0.85/kg 5.30kg $4.48 $2,564 10m3 $18,936

Solar

Electric

860kcal/kg 85% $0.09/kWh 51.6kWh $1.92 NO 150m3 $7,028

Electric

Boiler

860kcal/kg 90% $0.09/kWh 51.6kWh $4.63 NO 10-15m3 $13,487

Heat

Pump

860kcal/kg 400% $0.09/kWh 13kWh $1.17 NO 3-10m3 $4,256

Graph of the above data shown visually below.


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The following two simulated graphs are an extract from the Eskom report compiled

by the university of the Northwest. The simulation shows that Solar Electric systems

slightly out-perform Heat Pumps in a residential environment. They also show that

the payback period for Heat Pumps is better than that of Solar – again in a residential

environment. Typically, most Solar Electric installations are residential because of the

amount of space needed to produce adequate heat. In a commercial application, Solar

Electric systems can become very expensive and cumbersome to install. For this

reason, Heat Pumps have found majority of their market in commercial and industrial

environments. These types of installations include, hospitals, mines, apartment blocks,

hotels, offices and similar.


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The graph depicted below was compiled by the Plumbing Industry Association of

South Australia. The results of their report show that the Heat Pump out-performs the

Solar Electric system – again in the residential sector. Why the variance in results

from report to report? Firstly, Heat Pumps are fairly consistent and are not normally

affected by weather. Cloudy and rainy conditions produce less efficient results for

Solar Electric systems whereas these factors do not reduce the efficiency of Heat

Pumps as drastically. The reason for this is that the Heat Pumps COP (Co-efficient Of

Performance) is directly related to the ambient air temperature. Most Heat Pumps

operate comfortably in temperatures between -5˚C and 40˚C, which means their COP

values in general fluctuate between 2 and 6. In some instances where the ambient air

temperature does not permit the use of an air-to-water Heat Pump, water-to-water

systems can still be used. South African conditions are perfect for Heat Pump

installations because our ambient air temperatures are generally high throughout the

country and throughout the year.

Installation of Heat Pumps

Heat Pump installation, while simple at a glance – are engineered solutions. Many

factors are taken into account before an adequate Heat Pump can be recommended.

Since a Heat Pump comprises of a compressor, evaporator, fan, piping and valves,

each component must be matched to the required solution. In addition to the internal

components of the Heat Pump, other external factors are calculated. Water Storage

Tank size, number of tanks, water flow rate, external pump specification, volume of

water used, water temperature required, unit mounting and location are but a few of


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the elements used in the calculation of the specification. Although there are many

ways that a Heat Pump installation can be engineered, the most common installations

fit into two main categories as follows:

New Installations

A new installation usually occurs in the design phase of a building project. The Heat

Pump engineers will work closely with the architects and designers to provide the

perfect solution matched to the application. Water usage, ventilation, pipe length,

water tank size, location and insulation are just a few of the variables considered

when designing the correct solution. The Heat Pump specification once complete will

be included in the final design for production. The following diagram shows a

simplistic simulation of a typical installation. A Heat Pump is not always installed in

this manner and it should by no means be seen as a blueprint for installation. In most

industrial and commercial applications, more than one water storage tank is used and

they could be connected in series or parallel, in addition, multiple Heat Pumps may be

installed to produce the required result.


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Retro-fit Installations

Retro-fitting of Heat Pumps to existing installations is very common since both

corporates and end-users are either required by law to look at energy efficient (or

environmentally friendly) technologies or there is a requirement to save on running

costs. The term retro-fit implies that the Heat Pump (in this case) is installed to an

existing solution for water heating. The most common retro-fit occurs where clients

have an electric boiler (geyser) which needs to be retro-fitted with a Heat Pump to

replace electric element heating. As is common with the new type installation, design

and engineering is critical to the success of the installation. In most cases, retro-fitting

designs are more complex since buildings may not be designed with adequate

ventilation, insulation and so on… What is also common practice as part of a retro-fit

is the continued use of the existing electrical elements as a back-up means of heating

the water. The following diagram shows one possible simplistic retro-fit solution.

Again, it is not a blueprint and rather a visual representation.


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