Energy Storage>>David Nicholson-Cole Feb 2012 : K14DMT

ENTROPY - Tendency of energy and information to disperse, flow away... become chaotic. • Humans spend their existence trying to reverse or control entropy.

Threatsto our survival

•• Climate change•• End of Oil•• Water-Food•• Population•

•• No easy solutions: as architects, we do the best we can

Solar energy

Amount of Solar Energy falling on the planet - billions of GWhr/annum. It is Free! Catch it!

• 20 mins worth would power the human race for a year (this estimate is very vague).• All our energy comes from the Sun, except Tidal, deep Geothermal, Nuclear • (Wind is half Coriolis, half Solar/sea effect)• Direct radiation, Wind, Biomass (food), the water cycle, indirect warming

TWO problems• Most of it falls in places we don’t inhabit• Most of it falls at times we don’t need it SO.... we are challenged• Its difficult to Move it to where we want it• Its difficult to Store for later

Magma energy

PS, We are not talking about Geothermal Energy from the Magma!

• As found in Iceland, near Etna, etc.• Very localised availability - great if you have it!• To get it, must drill very deeply - 3 km• Risks of Seismic kickback

• Magma energy rising to surface is 1000th of the Solar falling on to it - about 1 watt/sqm. Not harvestable unless it is naturally near surface. Hasn’t stopped the ice in Antarctica being several kilometres deep

http://openlearn.open.ac.uk/mod/oucontent/view.php?id=398820&section=1

If you live near volcanoes, use them! But not in London

If you have hot springs, use them too, e.g. in Bath, Lourdes

Interesting use of Thermal Mass, as passive design idea

Solar capture in buildingsTHREE main methods available to us for using Sun:

Passive design •Form of building, orientation, sunspace design, materials, stack effect etc

Active design•Solar Thermal: Panels or tubes or devices to capture heat

•Solar PV: Panels or devices to capture electricity

‘Passive House’‘Passivhaus’‘Active House’BRE distinguishes :•Passive House as at Hockerton, or Integer house (BRE). Sunspace, thermal mass etc•Passivhaus - as defined by Passivhaus InstituteAlso:•Active House - defined by Active House Alliance. New build or Retrofit, the Key thing is to return more Energy than you use• IMHO, Tall Building is Active House - Passivhaus where possible, but supported by Systems!

Above, Passivhaus. Below, Active

Storing Energy, or Heat?

Energy is different from Heat

Energy can be converted • Direct transfer suffers losses (entropy)• Heat pump enables conversion of energy

- solar energy enables plants to grow into trees, or to feed us- food enables us to run a Marathon- Countless examples of energy conversion

Example:The Earth under my house doesn’t get Hot when it is thermally charged, but the Energy level increases (widening sphere of thermal influence)

Try this

Ice houses proof that Man made use of thermal storage for thousands of years

Red hot ball bearing dropped into a cup of cold tea cools immediately. Cup has vastly more energy than the ball.

Electrical Storage

PV process Radiant energy converts to:• 10-15% Electricity• 85-90% Heat, (by-product or wasted)(some advanced methods can get to over 30% Electricity e.g. focusing dishes, micro-lenses on Gallium arsenide)

Catching• PV panels roof or facade• Dishes, troughs, tubes• Local Micro generation • Major installations

Electrical Storage

Usable storage (after you’ve used what you want on site)• Grid - export to others• Pumping water uphill - Hydro-electric• Building scale (Tall buildings large enough)• National scale (eg, Norway, Austria)• Convert to Hydrogen

No Go storage• Batteries• Converting to heat

http://en.wikipedia.org/wiki/Electrical_grid

Heat Pump: Why use one?

• Use gas? or CHP?• Majority of heat comes from a FREE source, only needs converting• No Carbon emission: can use renewable electricity source. • More efficient if installed well

• Makes best use of electricity - 1% loss• Power needs could be met by on-site PV.• DNC’s is met entirely by PV capture.

• CHP produces more heat than power• Well insulated building doesn’t need all that heat• Tall Buildings have more heat gain than loss - CHP is a vanity• Biomass? Can’t be having truckloads of woodchip driving into city every week. Smoke emission...

See: Viessman Technical Guide

Heat Pump: the basics• Heat Pumps - converting energy from one temperature to another.

• Lost energy is the consumption of electricity for pumps, compressor etc.

• Useful energy is finally transferred from thermal source to the building

• Ratio of electricity used to heat delivered is the COP - Coefficient of Performance

• Typical COP is 2.5-3.0, theoretical maximum of 4.0.• Solar augmentation can turbo charge this. • DNC’s HP is 2kW/6kW, nominal COP of 6/3=3.0• With Solar, the actual COP near 4.8.

•

See: Veissman Technical Guide

Heat Pump: the works

• Refrigerators and air conditioners are producing coolth by heating something else - the atmosphere.

• Heating heat pumps are the same engine, producing warmth for building but cooling something else - ground, air, water

• Can be reversible - heat and cool building - heat and cool thermal mass

Getting heat from?• Atmosphere - cheap, plentiful, inefficient• Ground - best option - vertical or horizontal• Water - efficient, but very few sources• Other Thermal source - most efficient, but very unusual - solar, or burning of waste. If warm enough, may not need HP.• Note: COP improves 3-4% with every extra degree C of temperature in thermal source

How do heat pumps work? • Evaporator / condenser cycle. • Closed loop of refrigerant cycling endlessly• Another loop to the thermal mass• Another loop to the building

See: Veissman Technical Guide

Heat Pump: Others

• Heat Pumps - Absorption and Adsorption - Input of heat results in cooling!• Using ammonia dissolving and releasing from a solvent• Its the sort of thing you would use in Hot climate, making use of solar heat to drive it.• At the end of process, surplus heat has to be dispersed - to ground, atmosphere or water• If using the atmosphere, it contributes to heat island effect.

• See also, HP as MVHR

• If you want to research them fully, they are explained in Viessman Tech Guide

See: Viessman Technical Guide

• MVHR can also be a Heat Pump - supplying warm air in winter. Ground exchange for tempering incoming air

Delivery methods

•Must be efficient at low temperature.

Yes• Chilled beam for cooling• Underfloor heating• Fan coil unit, floor or ceiling• Assisted radiators e.g. Jaga, Dimplex• Prewarmed air to MVHR• Air from Sunspace - use passive methods

No• Normal hot radiators

Avoid:• Suspended Ceiling

Consider:• Consider solid ceiling, with localised drop-downs, and a shallow raised floor.• Insulate floor above slab - heating stays in apartment

Heat Pump: Large

• Heat Pumps for large buildings:• Available, in larger sizes... e.g. 20kW each, up to maximum of 200kW each.

• For very large installations, easier to cascade in groups, e.g. string together

• Dual compressor: one only for summer DHW, both for peak heating demand

• If you want to research them fully, they are explained in Viessman Tech Guide

See: Viessman Technical Guide

Cascading Dual compressor

Heating without Heat Pump: Solar

• Anneberg - near Stockholm• 70 family houses, 2002• Major thermal injection heats ground up to blood temperature. Large surface area, high temperature collectors on every roof.• Return liquid needs small heat pump only for hot water, not for heating.

• Drawbacks - long transmission lines in both directions - high capital cost• excessive system losses in v long trenches• systems losses in energy drain from borehole cluster• Needs years to build up.... disappointing results

Ground Source• Borehole draws energy from all around,• Horizontal loop from upper part of ground.• Solar heat takes decades to get down deep

• Below 18m, temperature is stable• In the UK, this is about 10º• In hot climates, e.g. Vietnam, could be over 20º• Solar, seasonal activity modifies upper levels• Top 3-5 metres variable• Many heat pump installations use Horizontal loops, if there’s enough land• A town or city installation will go to a vertical Borehole. • For Tall Buildings,• Vertical is only logical direction

See: Veissman Technical Guide

Horizontal collectorVertical collector

Boreholes: Drilling• Boreholes - mobile rig can get almost anywhere• For closed loop, about 100mm diameter• Refill with Bentonite after drilling and putting in pipes• Drillers should keep note of the quality of soil drilled through.

http://www.synergyboreholes.co.uk/

geothermal_boreholes/related_page.php?id=38

DNC house with mobile rig

Larger rigs can do deeper ones and more in less time

• Solar charging, or dumping summer heat gains depends on this information • If ground conditions not good enough for Solar charging, it cannot be done. •(Gravelly, Water bearing, Limestone caverns, mining works etc)

Boreholes: Depth• Drilling cost about £40-£60/ metre (depending on economy of scale)• Multiple boreholes can be done, with a manifold• Horizontal loop, assume 15-25 Watts/metre (depends on many factors, land, solar visibility, shading)• Vertical loop, assume 45-50 Watts/metre (depends on soil type)

• For Calculation purposes:

• Calculate Peak Load of Building • Determines size of HP• e.g. DNC’s house Peak Load is 4.74kW, plus DHW• Heat pump installed is 2kw/6kW • 4kW has to come from the borehole• Length of Borehole = (Peak demand - electrical) / (W/m)• DNC house = 4000 / 50 = 80 metres• Ignore top 5m, so make it 85m• Twinning, need 40m+40m, so make it 45m +45m

See: Veissman Technical Guide

Boreholes: charging

• Borehole can be charged actively with solar energy

• Bad to cluster them if they are alone - need the largest sphere of thermal capture

• Good to cluster them if solar charging - nursing the energy between the holes, reducing loss outwards

• Pattern of decline of energy level around borehole, over time. Retain energy level if solar charging

DNC’s boreholes are twinned

Local thermal contours vary, diurnally and seasonally

Drakes Landing cluster

Thermal Storage: Scale

• Single systems in a house e.g. countless water tank systems or borehole as in DNC house • Schools, moderate buildings, using carpark or borehole e.g. ICAX systems• Large Buildings - e.g. Linz, NYC Student projects

• Urban Blocks - Sweden, Canada - District heating

Thermal Storage:Solar chargingSolar heat exists in the earth already. Absorbed by crust. Takes many decades to get down deep

Active technology can help us exploit it. Put it down, get it out later

When do we Put and Get it?

• Interseasonal - Summertime: store thermal energy from May to end of September. No building heating required, so all heat energy goes down below. (Hot water from solar thermal tanks.)

• Diurnial - Equinox: October-Nov and March-April, warm days enable energy storage. Bring up in the cold evenings of the same day.

• Realtime - Wintertime: living mostly off previously stored energy. Frequently, winter sunshine is enough to supplement heat pump, or rapidly defrost borehole after heating cycle. Reduce deep chilling.

Thermal Storage

Buildings on Nottingham Campus using storage(It’s a University Policy)

Faculty of Eng. Learning Centre : approx 30 boreholes, 160m deep. No Air conditioning - all building heat gains captured by air-to-liquid heat exchangers, and buried underground. Retrieve in Winter using Heat pumps.

Maths building - same as for Fac-Eng building.

Humanities buildings uses boreholes, but these are directly to Groundwater - sucked up at one end of building and injected back at other end. Need special licence from Water Authority.

Faculty Eng. Centre: •Concrete Ceiling for thermal capacity = temperature stability,•Fibreboard acoustic absorbers,•Raised floor for services,•Air exchangers feed heat to boreholes

Power Tower,Linz• by Kaufman and Haas• 19 stories, 74 metre high

• Heating in Winter - retrieve• Cooling in Summer - dump gains• If balance of Building size and Borehole length is correct it is inexaustible source of energy• Reverse cycle heatpumps do the business!• Radiators and Chilled beams distribute• 700sqm PV capture 42,000 kWh electrical energyStorage• 46 boreholes, 150m deep, closed loop, total length 6,900m. Loops are also in 90 foundation piles 10m deep. • Groundwater also used from 2 wells for direct cooling, e.g. of computer centre, and heat recovered for the building.

Power Tower, Linz• Passivhaus facade - insulating and photovoltaic. • Entire building is a ‘Solar Thermal Collector’ - storing energy below• 6,900m of boreholes suggests a ‘worst case’ Peak Load of 350kW• Without energy charging, the boreholes are too close together and this would not work• With energy thermal charging, this does work, and it would never be exhausted.

Thermal Capacity calculation: Specific Heat

• How does one calculate thermal energy stored?• Thermal energy can be stored in a material as sensible heat by raising its temperature.• Look up cp Thermal capacity (Specific Heat) of common materials - Water, Clay, Concrete• Look up its Density, or calculate Mass.

The heat storage can be calculated in Joules as

q = V ρ cp dt (using volume and density)q = m cp dt (using mass)

whereq = sensible heat stored in the material (Joules)V = volume of substance (m3)ρ = density of substance (kg/m3)m = mass of substance (kg)cp = specific heat capacity of the substance (J/kgºC)dt = temperature change (degs C)

Convert q to kWh - dividing by seconds in the hour (3,600)

http://en.wikipedia.org/wiki/Heat_capacity

http://www.engineeringtoolbox.com/specific-heat-solids-d_154.html

Specific HeatBeware, some tables are in Joules, others in KiloJoules

Water 4.190 J/kgºCLimestone 0.91 J/kgºCHeavy stone 0.84 J/kgºCConcrete 0.75 J/kgºCClay 0.92 J/kgºCGlass 0.84 J/kgºCSalt 0.88 J/kgºCDry Sand 0.80 J/kgºCSteel 0.49 J/kgºCOak 2.0 J/kgºCPine 0.2.5 J/kgºCWax 3.43 J/kgºCAerogel 0.84 J/kgºC

Some of these are deceptive. Light materials have high capacity. But you would need a block of aerogel the size of a house to be the weight of a brick.

Thermal Capacity calculation: Conductivity

Conductivity is important•If your material can’t convey heat from a pipe carrying solar energy into the body of the thermal store, then it will not work for storage.

• Aerogel has good thermal capacity - but with the lowest density in existence, and immeasurably small conductivity.• Water has good conductivity, and can be stirred for faster action.• Some materials conductivity change with moisture content, one of the biggest being Clay, and if it dries out, it shrinks, and cracks, and loses contact with pipes.

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.htmlhttp://www.simetric.co.uk/si_materials.htm

Conductivities k = w/(m.K)Water 0.58Aluminium 250Limestone 1.26-1.33Clay 0.15-1.8 (moisture content)Concrete 1.7Blockwork 1.0-2.0Earth dense 1.5Glass 1.0Oak 0.17Pine 0.12Wax 0.25Snow 0.05-0.25Ice 2.18Air 0.024Iron 55-80Marble 2.08-2.94Oil 0.15

Thermal Capacity calculation: Do it

• Sample: One cubic metre of Clay 1000 litres x 1.7 = 1,700 kg q = 1,700 x 0.92 = 1,564 Joules / deg CkWh=1,564 / 3,600 = 0.43 kWh / cum

• Sample: One cubic metre of Water 1000 litres x 1.0 = 1,000 kg q = 1,000 x 4.2 = 4,200 Joules / deg CkWh=4,200 / 3,600 = 1.16 kWh / cum

Consider other aspects:WaterGood: Water can be pumped, stored, drained, stirred, used for firefighting. Very conductive.Bad: Water evaporates if hot, freezes and expands if iced, gets legionnaires’ bacteria, algae growth etc(Ice gives us a clue - Latent heat!)

Clay - shrinks when warmed, cracks, loses conductivity. Heavy... cheap...

http://www.engineeringtoolbox.com/density-materials-d_1652.html http://www.simetric.co.uk/si_materials.htm

Densities relative to WaterWater 1.0Clay 1.7Concrete 2.4Earth dense 2.0Glass 2.5Oak 0.59-0.93Pine 0.35-0.56Lignum Vitae 1.3Wax 0.93-0.97

PCM Phase Change Material• Uses Latent Heat of melting or freezing

• If not wanting to use Heat Pump, or wanting a store that a heat pump could use

• Store has to be warm enough e.g. if store is at 35-45% , use direct exchange, with flow rate to control rate of energy transfer

• PCM best for thermal energy storage - energy builds up, with a stable temperature, not getting ‘Hot’

•Can be a Passive device - no pumping required! Just instal brickettes or tubes in a space

Best known example is Water - requires a lot of heat to boil (stays at 100ºC) and a lot of cooling to freeze (stays at 0ºC)

Buildings normally use:•Eutectic Salts•Salt Hydrates•Organic: Waxes, Oils, fatty Acids

PCM Phase Change Material•http://www.netgreensolar.com/products/solarheat/pcm_how_it_works.htm• http://www.pcmproducts.net/Passive_Enclosure_Cooling.htm•http://www.rubitherm.de/english/pages/04b_glossary_02.htm

• Reduces heat load of computer, server installations• Thermal Capacity astonishing• Very poor conductivity - high surface area is very important• One cubic metre of PCM - theoretically 50kWh, in practical terms more like 20kWh• Has thermal capacity either side of changeover point.• Needs about 4-6 degrees to make full changeover• Warning! may swell after changing phase

Try a candle - completely cool to touch except immediately around flame

Example of Passive use: in Ceiling

Example of Active use: in Flooring

PCM : Rubitherm• Rubitherm: German company with range of PCM products.• Compact Storage Modules (CSM) - aluminium cased - v high conductivity, no corrosion risk.• http://www.rubitherm.de/english/pages/04b_glossary_02.htm

• Panels can be arranged like condenser plates, to achieve maximum surface area - blow air through the box• Box 0.38 cubic metre 4kWh• Box 0.56 cum 8kWh.• Equivalent to 12-16 kWh/cubic metre depending on thickness and spacing of panels, and PCM material chosen. • Not for long term storage - used as a thermal buffer, with air blown through 230-420 m3/hour• CSM panels can be used with water and sea water.

Peveril Solar House

Active HouseNegative Kilowatt Hours/Squr Metr/ Year

See http://ChargingTheEarth.blogspot.com

Peveril Solar House

Active HouseAlternative solutions

This is the one!

Conventional solar thermal

Solar, using a buffer tank

Peveril Solar House

Active HouseNormal and Augmented working

See main site: http://ChargingTheEarth.blogspot.comSee Active House website:http://www.activehouse.info/cases/peveril-solar-house

Peveril Solar House

Active HouseKey Performance Indicators and data recording

• PV 3,400 kWh

• Heat Pump 2,700 kWh

• Of which heating only is 2,000kWh

• 1,400kWh credit = minus 12kWh/sqm/year

•Daily figures on spreadsheet• http://tinyurl.com/peveril-metering•

Ground Temperatures improved

Annual consumption improved Heat pump workloar reduced

All daily figures recorded

Peveril Solar House

Proposal to add Varisol TubesMarch 2012 projectAdd high temperature, low volume collector to the system.Compare with existing high volume, low temperature.See http://ChargingTheEarth.blogspot.com

Drakes Landing

Okotoks, Alberta, Canada

Solar thermal panels on garages feed heat to cluster of boreholes

ICAX -

ICAX -> http://www.icax.co.uk/

Gathering heat from under tarmacPlayground, car parks

Store under building, heat pump makes us of it.

Can prevent icing of roads

Tall BuildingsTall Buildings intrinsically build up heat gains. Can this be stored or moved? Mixed use Buildings - offices give heat to residential

TBs intrinsically better for picking up sunlight - higher, not shaded, above dust levels, high tech design of facade.

Verticality is not so much a problem. In summer, you are storing free thermal energy. There is six times as much of it as electrical, for the same surface area.

Vertical surfaces pick up thermal energy when you want it - Equinox and Winter

Energy distribution: Tall Building

Thanks to Group A for this illustration!

New York 2011K14TBI Work by CAS and SSW groups

New York 2011K14TBI •Work by CAS and SSW groups•PV and Solar thermal panels in facade•Energy storage at service levels at intervals in building, short term stores collecting solar thermal energy and providing energy back to local heat pumps. •Office areas providing surplus energy to stores for residential.

Solar Earth Charging.....Where is it going?

• Long timescale to change buildings, or way of creating buildings

• Energy market still keeps conventional heating methods too cheap

• 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. • It took until 1883 before the first ‘Tall Building’ emerged, the Home Insurance in Chicago.

Some inventions take time to be accepted!

Please do it in your building!>>David Nicholson-Cole Feb 2012