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.
Threats to 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
If you live near volcanoes, use them! But not in London If you have hot springs, use them too, e.g. in Bath, Lourdes
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
Interesting use of Thermal Mass, as passive design idea
Solar capture in buildings THREE 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 Institute Also: •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?
Try this
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)
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 See: Veissman Technical Guide
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
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
• MVHR can also be a Heat Pump - supplying See: Viessman Technical Guide
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 dropdowns, 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 Vertical collector
See: Veissman Technical Guide
Horizontal 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.
• 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) 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
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
DNC’s boreholes are twinned
• 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,
Drakes Landing cluster
over time. Retain energy level if solar charging
Local thermal contours vary, diurnally and seasonally
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 charging Solar 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 energy Storage • 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 http://en.wikipedia.org/wiki/Heat_capacity
• 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) where q = 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://www.engineeringtoolbox.com/ specific-heat-solids-d_154.html Specific Heat Beware, some tables are in Joules, others in KiloJoules Water 4.190 J/kgºC Limestone 0.91 J/kgºC Heavy stone 0.84 J/kgºC Concrete 0.75 J/kgºC Clay 0.92 J/kgºC Glass 0.84 J/kgºC Salt 0.88 J/kgºC Dry Sand 0.80 J/kgºC Steel 0.49 J/kgºC Oak 2.0 J/kgºC Pine 0.2.5 J/kgºC Wax 3.43 J/kgºC Aerogel 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.html http://www.simetric.co.uk/si_materials.htm Conductivities k = w/(m.K) Water 0.58 Aluminium 250 Limestone 1.26-1.33 Clay 0.15-1.8 (moisture content) Concrete 1.7 Blockwork 1.0-2.0 Earth dense 1.5 Glass 1.0 Oak 0.17 Pine 0.12 Wax 0.25 Snow 0.05-0.25 Ice 2.18 Air 0.024 Iron 55-80 Marble 2.08-2.94 Oil 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 C kWh=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 C kWh=4,200 / 3,600 = 1.16 kWh / cum
Consider other aspects: Water Good: 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 Water Water 1.0 Clay 1.7 Concrete 2.4 Earth dense 2.0 Glass 2.5 Oak 0.59-0.93 Pine 0.35-0.56 Lignum Vitae 1.3 Wax 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
Try a candle - completely cool to touch except immediately around flame
important • One cubic metre of PCM - theoretically 50kWh, in practical terms more like 20kWh • Has thermal capacity either side of changeover point. Example of Passive use: • Needs about 4-6 degrees to make full changeover in Ceiling • Warning! may swell after changing phase
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 House Negative Kilowatt Hours/Squr Metr/ Year See http:// ChargingTheEarth.blogspot.com
Peveril Solar House Active House Alternative solutions
This is the one!
Solar, using a buffer tank
Conventional solar thermal
Peveril Solar House Active House Normal and Augmented working See main site: http://ChargingTheEarth.blogspot.com See Active House website: http://www.activehouse.info/cases/peveril-solar-house
Peveril Solar House Active House Key Performance Indicators and data recording
• PV 3,400 kWh • Heat Pump 2,700 kWh Annual consumption improved
Heat pump workloar reduced
• Of which heating only is 2,000kWh
• 1,400kWh credit
= minus 12kWh/sqm/ year
•Daily figures on Ground Temperatures improved
All daily figures recorded
spreadsheet • http://tinyurl.com/ peveril-metering
•
Peveril Solar House Proposal to add Varisol Tubes March 2012 project Add 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 tarmac Playground, car parks Store under building, heat pump makes us of it. Can prevent icing of roads
Tall Buildings Tall 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 2011 K14TBI Work by CAS and SSW groups
New York 2011 K14TBI •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