Peveril Solar Sunboxes lecture Feb 2013

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

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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 risks  Long term, major breakdown

Only one planet to live on!

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

systems  Teach others to do it

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’ concept  Using Technology and the Grid to balance

consumption and generation  Highly 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 Grid PV roof 4kW

Sunbox 4 m2, 3 m3 Solar House 120 m2

The Earth

The Borehole Clay+Limestone 3600 m3

GSHP 2kW normal 6kW panic

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

 Facing ESE  Not ideal, but it’s good enough  Shading from hill to south west

 Generates 3,200 kWh annually Space available

Space available

3,200 kWh annually

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

Design One

 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 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  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. 

Illustrations: Mark Aalf

Surya Sunboxes  First Design:  200mm deep solaria  1.1 cu metre volume  Vertical front panel, glassy  Metal reflectors above+ below  6mm polycarbonate walls

Design One

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

polycarbonate  Insulated detailing

Design Two

Surya Sunboxes  Wall mounted Sunbox

refronted with ETFE

Design Three

 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 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 layout 2013

Plumbing in airspace above the heat pump

Technology pentangle:Performance (annual) The Grid PV roof 3,200 kWh

Sunbox 2,700 kWh Solar House

The Earth

The Borehole 12,000 kWh

These two are in balance = Carbon Zero GSHP 3,200 kWh (5,200 kWh) No further need for ‘panic’ mode Saves 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’

Instal Sunbox

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

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!

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

Tubes operate in ‘swimming pool heating mode

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 ď &#x2021; Plumbing as, at May 2012

Solar thermal charging: will it happen? â&#x20AC;˘ The catalytic converter was invented in the 1950s, but took until the late 1990s to become a requirement. â&#x20AC;˘ Elisha Otis demonstrated the safety elevator in 1853, and died in 1861. â&#x20AC;˘ 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 ď &#x2021; The principle can be applied to

larger buildings ď &#x2021; Authorâ&#x20AC;&#x2122;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  

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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!