1. Sustainable Low Energy Cooling
... the quest for ‘free’ cooling

2. References: Essential reading:
CIBSE (2005) KS3: Sustainable low energy cooling: an overview
EEBPP (2001) GIR85: New ways of cooling - information for building designers
Further reading:
Martin Liddament (2000) Technical Synthesis Report EA ECBCS Annex 28: Low energy cooling
Tom De Saules (2004) BG8/2004: Free cooling systems, BSRIA

4. Ground cooling Air can be cooled or heated:-
air system
Air can be cooled or heated:-
from 28 °C down to around 17 °C in summer.
from below zero to around 5 °Cin winter.
A significant reduction in heating and cooling loads.
Ground temp varies depending on the depth and time of year.
Usually systems buried to a depth of 2–4 m give the best return.

5. UWE Architecture Studio Building

7. Ground cooling water system
Open vertical borehole – 130m deep
better performance
Closed horizontal loop – 2 m deep trench
cheaper to install
closed loop system
groundwater temps 6-10°C yield CW temp approx. 12°C

8. Bau Energie Forum, Berlin
Surface water cooling
Bau Energie Forum, Berlin

9. Recirculation air

10. Recirculation air hR

11. Direct evaporative cooling
Exercise 1:
For an outdoor air condition of 26°C d.b. 19°C w.b. plot the process and comment on the effect on chiller performance.
Assume evaporation saturation efficiency, E = 85%

12. Evaporative free cooling using plate HEX
Exercise 2: Plot cycles and compare the above arrangement with (a) HEX without evaporator, and (b) no HEX
R: 23°C d.b. 55% sat. O: 28°C d.b. 60% sat.
Assume: HEX effectiveness, η = 60% (sensible heat)
evaporation saturation efficiency, E = 90%
cooler coil ADP = 10°C and contact factor β= 1

13. Dessicant cooling system
Exercise 3: Plot the cycles and discuss

14. Dessicant cooling system

15. Dessicant cooling system
A – B
dehumidification by dessicant wheel
B – C
sensible cooling by thermal wheel
C – D
evaporative cooling
1 -2
adiabatic humidification
2 – 3
heat recovery from thermal wheel
3 – 4
regen. heating
4 – 5
evaporation from dessicant wheel
Note:
not ‘free’ cooling due to heat input
cooling COP ≈ 0·5 ― 0·7 in hot weather
system works better in ‘mid’ seasons, Spring & Autumn

16. Free cooling with cooling towers

17. Chiller using free cooling air coil

18. Chiller using free cooling air coil

19. Delivery systems to exploit free cooling
water cooled slabs
displacement ventilation
chilled beams/ceilings