1. Building Research Establishment 20 th June 2007 Integrating a large solar array to enhance the performance of a low energy building. Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnv HSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental Sciences CRed

2. Original buildings Teaching wall Library Student residences

3. Nelson Court Constable Terrace

4. Low Energy Educational Buildings Elizabeth Fry Building Medical School ZICER Nursing and Midwifery School

5. The ZICER Building The Solar Arrays Performance of PV Issues of Shadowing Electrical Integration Integrating a large solar array to enhance the performance of a low energy building.

6. ZICER Building Heating Energy consumption as new in 2003 was reduced by further 50% by careful record keeping, management techniques and an adaptive approach to control. Incorporates 34 kW of Solar Panels on top floor Low Energy Building of the Year Award 2005 awarded by the Carbon Trust.

7. Two large open plan offices: Note: extensive use of computers

8. Top floor is an exhibition area – also to promote PV Windows are semi transparent Mono-crystalline PV on roof ~ 17 kW in 10 arrays Poly- crystalline on façade ~ 6/7 kW in 3 arrays ZICER Building

9. ZICER Building PV performance Façade (kWh)Roof (kWh)Total (kWh) 200426501940122051 200528401980922649

10. Performance of PV cells on ZICER

11. Load factors Façade: 2% in winter ~8% in summer Roof 2% in winter 15% in summer Output per unit area Little difference between orientations in winter months Performance of PV cells on ZICER

12. All arrays of cells on roof have similar performance respond to actual solar radiation The three arrays on the façade respond differently Performance of PV cells on ZICER

13. 120 150 180 210 240 Orientation relative to True North

16. Arrangement of Cells on Facade Individual cells are connected horizontally As shadow covers one column all cells are inactive If individual cells are connected vertically, only those cells actually in shadow are affected.

17. Performance of PV cells on ZICER

18. (A) Actual ZICER costs – no grant (B) Actual ZICER costs – with grant of £172 000 (C) Avoided costs (ZICER) – no grant (D) Avoided costs (ZICER) with grant of £172 000 (E) Average EU costs in 2006 (F) as E with 50% capital grant Performance of PV cells on ZICER Cost of Generated Electricity

19. Actual Situation excluding Grant Actual Situation with Grant Discount rate 3%5%7%3%5%7% Unit energy cost per kWh (£) 1.291.581.880.841.021.22 Avoided cost exc. the Grant Avoided Costs with Grant Discount rate 3%5%7%3%5%7% Unit energy cost per kWh (£) 0.570.700.830.120.140.16 Grant was ~ £172 000 out of a total of ~ £480 000 Performance of PV cells on ZICER Cost of Generated Electricity

20. Performance of Photo Voltaic Array Inverters are only 91% efficient Most use is for computers DC power packs are inefficient typically less than 60% efficient Need an integrated approach

21. Peak Cell efficiency is ~ 9.5%. Average efficiency over year is 7.5% Mono-crystalline Cell Efficiency Poly-crystalline Cell Efficiency Efficiency of PV Cells Peak Cell efficiency is ~ 14% and close to standard test bed efficiency. Most projections of performance use this efficiency Average efficiency over year is 11.1% Inverter Efficiencies reduce overall system efficiencies to 10.1% and 6.73% respectively

22. Life Cycle Issues Module embodied energy 3230 and 2750 kWh Array supports including sysetm = 285 kWh/kWp Installation energy 131.4 kWh/kWp 11250 vehicle kilometres > 453.2 kWh/kWp Total 4.1 MWh/kWp and 3.4 MWh/kWp EYR 20 25 30 allowing for degradiation 3.2 3.8 4.6 3.5 4.2 5.1

23. Conclusions Economics of PV was only viable on ZICER because of Grant Shading has some effect on façade, but improvements could be made by different method of wiring cells Overall Load Factor is 7.6% with 8.3% on roof and 4.7% on façade. In summer Load Factor can reach 15%. 9% of electricity is lost in inverters, and a further 50 – 60% is lost in IT equipment. Need to consider an integrated approach – possibly with DC networks in similar buildings. Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnv HSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental Sciences CRed

24. Building Research Establishment 20 th June 2007 Integrating a large solar array to enhance the performance of a low energy building. Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnv HSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental Sciences CRed