Photovoltaic power with Solar energy storage, augmenting Heat Pump to achieve Carbon Zero CIBSE ASHRAE London April 2012

by David Nicholson-Cole with help from Prof S Riffat, Dr B

Mempouo, Dr Chris Wood and David Atkins

Department of Architecture and Built Environment University of Nottingham

House solar-heated for the entire year: it is beyond zero-carbon, for both heating and hot water

Hybrid retrofit; could be applied to existing houses

Project from Aug 2009- present day

Carbon Zero

Why do we want it? Climate change

Long term, major risk Sea levels, migration, food

water

Energy shortage Short term, serious risksLong term, major breakdown

What can we do? (...as architects & engineers)Design better buildings and

systemsTeach others to do it

Only one planet to live on!

Increasingly difficult to get energy from the ground

Carbon reducing tricks without special technology

Simplify lifestyle Buy power from 100%

renewable suppliers Yes, we do that!

Feed in tariff Yes, financial incentive

Plant trees Yes, but where? We are doing that Not being done enough, takes too long

Live off Grid? No, we cannot all do it, urban society

Insulate and design better? Yes! But what about existing housing stock?

With all these - follow with the Technology to reduce carbon emission

Solar Energy

Amount of Solar Energy falling on the planet - billions of GWhr/annum. It is Free! Catch it!• Ground source heat pumps use stored Solar energy (not Magma energy)• In Urban areas, direct solar heat cannot reach ground, too much shading • Tall buildings can reach up and claw that energy down into storage

Buildings and urban landscape shade the earth

Peveril Solar house

How do we do it? ‘Active House’ conceptUsing Technology and the Grid to balance

consumption and generationHighly applicable

to Retrofit Yes, new houses should

be Passivhaus

Peveril Solar house Developer house 120m2, 2007 Brick-block, well insulated 3.6 sqm extension added 2012

Includes:• Vertical Elevator• Disabled kitchen• Light tube• PV panels• Thermal bottle-store• Partial Heat reclaim• Efficient lighting• GS heat pump• Underfloor heating• Double glazing• Vegetable garden

Technology pentangle: Components

The Earth

The Grid

Solar House120 m2

Sunbox4 m2, 3 m3

PV roof 4kW

The BoreholeClay+Limestone

3600 m3

GSHP2kW normal6kW panic

Photovoltaic Roof

22 x 180W Sharp panels, 28 sqm = 3.96 kW, installed Oct 2009

Facing ESENot ideal, but it’s good enough Shading from hill to south west

Generates 3,200 kWh annually

3,200 kWh annually

Space available

Space available

Heat pump - Ground Source

Heat pump: Swedish IVT Greenline C6 with integrated water tank

6 kW nominal output, power consumed about 2.2 kW Has ‘additional heat’ option

if it cannot get heat from ground

Annual power consumption in 2008 was 4,800-5,600 kWh/year depending on weather, for this house size & parameters

With Solar Augmentation, the heat pump is running at approx 3,200 kWh/ year average

Borehole, vertical

‘Warm’ medium is 2 vertical boreholes, 48 metres deep (equivalent to 16 storeys)

Soil is dense ‘Marl’ (Glacial Clay-Rock mixture)

Vertical boreholes are ideal to recharge with solar heat if soil is good

No garden space here for horizontal ‘slinkies’ or collector These could not easily be solar

charged If too small, horizontal ones can

freeze or swell ground

Borehole, vertical

Twin 48m boreholes Upper part affected by seasonal change -

less useful Not fully stable until 5-18m down

Active Volume 3,600 m3 Active Mass 6,800 tonnes Thermal capacity of active volume is 1750

kWh/ºK This is approximate

Depends on how far heat goes in one season, rate of heating, conductivity

Twinning of Holes is better for Solar Charging Space between, reduces loss, nurses the

added heat Opposite of normal advice for boreholes. Shallow hole less risk of hitting caverns

Charging Principle 1 Without charging, deep ground

temperature falls Reaches a new stasis, lower than in the

first year of operation Too deep to recover in one summer

Reduction in COP of heat pump COP worsens 3-4% with each degree C of

‘coolth’ in source

Let us put solar heat down NOW! • Every day!• Summer sunshine• Equinox sunshine• some Sun even in winter!

Charging Principle 2

Use Solar collector Can be flat plate or evacuated tube Can be Custom-designed Sunbox, as in the Surya models

designed for this project, using recycled swimming pool panels, and mini-solarium design. Low temperature high volume flow seems to be most effective

Future: could be PVT, PV with thermal loop behind glass

Circulate glycol mixture Warmed liquid can be trickle fed into the ground loop (Original design took ground loop through Sunbox, now

replaced by trickle-feed)

Sunboxes driven by Thermostat Delta-T >2.5 degs C or Real-T >15ºC

Charging Principle 3

Summer - Interseasonal charging Heat pump dormant, doing hot water only Solar Sunbox pump depositing heat, every day,

equivalent to 1.15 kW. Triggered by delta-T or real-T

Equinox - Diurnial Heat pump working intermittently, as required,

drawing heat from Sunbox if there is a Delta-T Sunbox captures daytime heat on nice days for

evening use

Winter - Realtime Heat pump busy much of the day - good Delta-T If enough heat up above, will divert some flow

to Sunbox and download it, equivalent to 2 kW but for shorter hours

Surya Sunboxes Both designs use the same

black poly-propylene chillers, each 1 m2 . 4 m2

face the sun, and for collecting from the air, the surface area is 8 m2.

First design:Mar 2010-July 2011

Second design: August 2011->

Third design Autumn 2012

Design One

Design Two

Greenhouse effect

Solar energy entering transparent enclosure converting to heat because

wavelength changes and it does not reflect out again

Internal air temperature rises Basis for all greenhouses, global

warming, solar thermal panels

Solar cooker reflectors

Illustrations: Mark Aalf

Installed 2010, de-installed 2012 Concentrate additional solar heat

into the container Millions of these in use in rural villages,

India+Africa Reflectors used to boost the performance on

sunny days - were effective Removed 2012 because the addition of ETFE

is so significant that contribution of mirrors is reduced.

Surya Sunboxes First Design:

200mm deep solaria 1.1 cu metre volume Vertical front panel, glassy Metal reflectors above+

below 6mm polycarbonate walls

Second Design: 700mm deep solarium 2.8 cu metre volume Sloping front panel, matt Top reflectors only Multi-wall thin

polycarbonate Insulated detailing

Design One

Design Two

Surya Sunboxes

Wall mounted Sunbox refronted with ETFE Greater thermal

transparency Lightness, long life Double stretched skin Increasing winter

capture

New roof mounted Sunbox Metal radiator collectors Polycarbonate enclosure Small bore pipes Unitised construction on

standard racking

Design Three

Design Four

Sunbox build 2010

Designed and built entirely by DNC, researcher and householder Scaffold, open ended time

limit Indoor plumbing too

Decisions Design continues to evolve

even while up there 3D Model every step

Precision Metal and Plastic - little

tolerance for errors Keep it all Plumb and

Square!

System: schematic during 2011 Three possible system layouts

Left, Peveril Solar house uses the simplest possible circuit, entire loop through Sunbox

Right, a idea combining HW tank or heat exchanger with high performance solar panels

Third, the one we are using, see next slide

System:schematic layout2013

Plumbing in airspace above the heat pump

The Earth

Technology pentangle:Performance (annual)

The Grid

Solar House

Sunbox2,700 kWh

PV roof 3,200 kWh

The Borehole12,000 kWh

GSHP3,200 kWh

(5,200 kWh)

These two are in balance = Carbon Zero

No further need for ‘panic’ modeSaves 1,200 kWh / year

Ground Temperature

Deep Ground temperature is key performance indicator

Efficiency of GSHP related to warmth of source

Ground temperature not fallen below 10.0º in three winters since Sunbox installed

Ground does not get ‘hot’ - energy level expands to a larger cylinder of ‘warmth’

Graph of ground temps over four winters shows that the solar augmented one has a smoother curve and recovers quickly after the heating season

Instal Sunbox

Degree day <->Heating workload Red curve =heating requirements of any building in

Nottingham region, base 15.5º Blue curve = heating workload of GSHP

Electrical consumption of Space heating only (omitting DHW and floor pump)

Instal Sunbox

Thermal Energy model

Energy simulation based on 3+ years of meter readings Input data is GSHP meter, Solar thermal meter Computes figure for amount drawn from borehole Computes a figure for the thermal elasticity of soil, i.e. the

tendency for borehole to restore its temperature from the infinite surroundings

Computes a radius of a theoretical single borehole energy volume

Displays radius as a curve - the orange one

COP improvement?

COP is assumed to improve by 3% / degree C The deep ground hints that there is approx 5 degrees of

benefit in the cold season compared with previous year Heat pump electrical consumption saving should be 15% but

improvement has been greater - is more than 40% annually Heating requirement of 14,600 kWh is met by 3,200 kWh of

electricity - suggests a virtual COP of >4. GSHP annual running time (FLEQ) is reduced to 1200-1600 hrs

depending on weather The author notes that some of the saving is by the heat pump

never needing to use its ‘additional Heat’ mode, saving perhaps 1000 kWh/yr

Addition of Tubes 2012 Evacuated tubes were added March

2012 Comparing the types of collector:

all connected to same ground loop Tubes need a Heat Exchange or they

‘snuff out’ with cold ground loop Very intermittent operation Early indication is that Sunbox is far

more effective DONT fit tubes unless facing due south

and have space to fit them upright!

Tubes operate in ‘swimming pool heating mode

Solar controller can manage two pumps, so a heat exchanger can be positioned between the loops.

Additional Roof unit 2012

Unitised construction Can be built off site, delivered and

set up on rails Piping with 15mm copper Metal collectors Working well during first winter

Views of the Loft Plumbing as, at May 2012

Solar thermal charging: will it happen?

• The catalytic converter was invented in the 1950s, but took until the late 1990s to become a requirement.

• Elisha Otis demonstrated the safety elevator in 1853, and died in 1861.

• First lifts were in shops and warehouses. It took until 1883 before the first Tall Building emerged

Some inventions take time to be accepted!

Conclusion: GSHP with or without charging? GSHP expensive enough, you deserve to

have it perform better This should be considered with every GSHP,

especially in urban area This Add-on could attract Renewable Heat

Incentive Solar charging is a Defroster even if it does

not actually ‘Heat’ the ground.

Nota bene: Could be done with standard or PVT

panels, not sunbox Only possible if ground conditions permit Solar Boreholes should be shallow and

clustered, not deep and singular

Scaling up the technology

Hearst Tower in New York stores surplus energy underground for later retrieval

Power Tower in Linz is like a huge solar panel, with a PV solar facade, and 7 km of boreholes storing energy gains below ground

Recent new Nottingham University buildings cool building by storing heat gains underground for later retrieval

Researcher Nic Wincott has documented many examples in Sweden

Scaling up the technology

The principle can be applied to larger buildings

Author’s postgraduate students applying it to very tall buildings for sites in New York and London: intermediate stores on mechanical floors

Website

Research process and construction process is recorded on a blog / website:

http://chargingtheearth.blogspot.com/ Daily, weekly + monthly meter

readings are stored on a web based spreadsheet:

http://tinyurl.com/peveril-metering The project is continuing and evolving

into the long term Data collected shows that the

experiment has worked!

Thankyou!