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Why go Solar PV?. Integrating a large solar array to enhance the performance of a low energy building. - A Case Study. Building Research Establishment 20 th June 2007. Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICE, CEnv HSBC Director of Low Carbon Innovation:
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Why go Solar PV? Integrating a large solar array to enhance the performance of a low energy building. - A Case Study Building Research Establishment 20th June 2007 • 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
Teaching wall Library Student residences Original buildings
Nelson Court Constable Terrace
Low Energy Educational Buildings Nursing and Midwifery School Medical School Phase 2 ZICER Elizabeth Fry Building Medical School
Integrating a large solar array to enhance the performance of a low energy building. • The ZICER Building • The Solar Arrays • Performance of PV • Issues of Shadowing • Electrical Integration • Economic Issues • Life Cycle Issues
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.
Two large open plan offices: Note: extensive use of computers
ZICER Building • 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
Performance of PV cells on ZICER Output per unit area Little difference between orientations in winter months Load factors Façade: 2% in winter ~8% in summer Roof 2% in winter 15% in summer
Performance of PV cells on ZICER All arrays of cells on roof have similar performance respond to actual solar radiation The three arrays on the façade respond differently
120 150 180 210 240 Orientation relative to True North
Arrangement of Cells on Facade Individual cells are connected horizontally If individual cells are connected vertically, only those cells actually in shadow are affected. As shadow covers one column all cells are inactive
Performance of PV cells on ZICER Cost of Generated Electricity • (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 Grant was ~ £172 000 out of a total of ~ £480 000
Efficiency of PV Cells Poly-crystalline Cell Efficiency Mono-crystalline Cell Efficiency • Peak Cell efficiency is ~ 9.5%. • Average efficiency over year is 7.5% • 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
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
Life Cycle Issues Life Time of cells (years)
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. • Important to use actual rather than test bed efficiencies in design appraisal • Energy Yield Ratios are lower than many other forms of generation. Long transportation distances associated with PVs do not necessarily lead to a low embodied carbon requirement. • 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
Why go Solar PV? Integrating a large solar array to enhance the performance of a low energy building. - A Case Study Building Research Establishment 20th June 2007 • 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