1. Energy storage Prof Phil Banfill Urban Energy Research Group
OCTES workshop, 31st October 2012

2. Urban Energy Research Group
Skills/Experience in retrofit and new build:
Building simulation and modelling, including district and regional scale
Climate projections
System and equipment integration
Energy monitoring and analysis / metering
Retrofit measures - domestic and non-domestic
“Soft Landings” initiative - users and commissioning
Life Cycle Assessment - environmental impacts
Whole Life Costs
Thermal comfort
“Solar cities” initiative
£3.5m research project funding since 2004

3. Energy storage
Aims to reduce energy consumption by smoothing out the fluctuations – whether electrical or thermal energy
temp
time
Desired temp
Ambient temp
Heat surplus
Heat deficit

4. Energy storage
Aims to reduce energy consumption by smoothing out the fluctuations – whether electrical or thermal energy
Store this heat
temp
time
Desired temp
Ambient temp
Heat surplus
Heat deficit

5. Exposed thermal mass smoothes fluctuations

6. simple model: mass = storage
Thanks to Paul Tuohy

7. simple model: mass = storage
low thermal mass: surface temperature is responsive to solar gains and heating T
high thermal mass: surface temp less responsive to solar gains and heating

8. simple model T
Comfort?

9. Comfort depends on Tsurface and Tair
Standard House
Passive House T
from EIV

10. simple model: mass = storage
low thermal mass: surface temperature is responsive to solar gains and heating
2 days in October T
high thermal mass: surface temperature less responsive to solar gains and heating

11. simple model: mass = storage
low thermal mass: surface temperature is responsive to solar gains and heating
Faster response to heating system? T
high thermal mass: surface temp less responsive to solar gains and heating
Better storage of solar and internal gains?

12. Types of thermal storage
Sensible heat – i.e. elevated temperature, thermal mass
Latent heat – by change of phase
Chemical heat – by exo- or endo-thermic chemical reactions
The important parameter is the energy density = heat change x density

13. Energy density - materials
Sensible heat
Stone, concrete etc MJ/m3°C
Water MJ/m3°C
Latent heat
Eutectic mixtures, salt hydrates, organics (incl. waxes) up to 100 MJ/m3
Chemical heat
Absorbents etc MJ/m3°C

14. Phase change materials
Phase change materials as room linings can make a difference
Wax impregnated gypsum wallboard

15. Potential applications / systems
Room linings – products already available but issues of phase change temperature.
Storage tanks = “heat batteries” but issues of heat exchange, size, location.

16. Conclusions
Low thermal mass buildings respond faster to heating and occupancy
High thermal mass responds slower but stores the internal gains
Heat can be stored in various materials with a range of efficiencies – significant amounts of material are needed for the effects to be worthwhile. Issues of cost.

17. Thank you for listening
@HWUrbanEnergy