Oxford 5th April 2006

Integrating a large solar array to enhance the performance of a low energy building.

Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICEHSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental SciencesCRed

• The ZICER Building

• The Solar Arrays

• Performance of PV

• Issues of Shadowing

• Electrical Integration

• Some Observations on Solar Thermal

Integrating a large solar array to enhance the performance of a low energy building.

Zuckerman Institute for Connective Environmental Research (ZICER)

• Part of the School of Environmental Sciences• A World Renowned 5** Research Department:

Excellent Teaching Rating• Includes

– Tyndall Centre– Centre for Social and Economic Research into the

Global Environment– Centre for Environmental Risk– Climatic Research Unit– Low Carbon Innovation Centre

• 65 faculty, 145 Researchers, 200 Research Students, over 50 Postgraduate Students on taught courses and nearly 400 undergraduates.

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

Low Energy Building of the Year Award 2005 awarded by the Carbon Trust.

ZICER Building

• One of 7 Low Energy Buildings at UEA• One of 5 using Termodeck construction• Integrates Photovoltaic cells into initial design

– 6.7 kW on top floor of façade– ~27.2 kW on roof

•Two large open plan offices: Note: extensive use of computers

•Significantly more than originally planned – meant that target of PV generation was not reached

• Top floor is an exhibition area – also to promote PV

• Windows are semi transparent

• Mono-crystalline PV on roof ~ 27 kW in 10 arrays

• Poly- crystalline on façade ~ 6/7 kW in 3 arrays

ZICER Building

Photo shows only part of top

Floor

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ZICER Building PV performance

Façade (kWh) Roof (kWh) Total (kWh)

2004 2650 19401 22051

2005 2840 19809 22649

Summer day (27th June 2005)

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Solar Radiation

Performance of PV cells on ZICERNote: East Anglia mean solar radiation is just 1100 kWh per year

– in many places in world it is as high as 2000 kWh even at similar latitude

Only 1/10th of output on cloudy summer day

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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

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Top Row

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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 - January

Radiation is shown as percentage of mid-day maximum to highlight passage of clouds

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Arrangement of Cells on Facade

Individual cells are connected horizontally

As shadow covers one column all cells are inactive

Arrangement of Cells on Facade

Individual cells are connected vertically

Only those cells actually in shadow are affected.

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Performance of PV cells on ZICER

Actual Situation excluding Grant

Actual Situation with Grant

Discount rate 3% 5% 7% 3% 5% 7%

Unit energy cost per kWh (£) 0.89 0.90 0.91 0.56 0.57 0.57

Avoided cost exc. the Grant

Avoided Costs with Grant

Discount rate 3% 5% 7% 3% 5% 7%

Unit energy cost per kWh (£) 0.36 0.37 0.38 0.03 0.04 0.05

Grant was ~ £172 000 out of a total of ~ £480 000

Performance of PV cells on ZICER

Cost of Generated Electricity

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

Solar Energy - The BroadSol Community Project

Annual Solar Gain 911.384 kWh

Solar Collectors installed 27th January 2004

Performance when there was snow on ground

Store temperature was at base of tank

Normal hot water circuit

Solar Circuit

Solar Pump

• Efficiency of increases with increased day time use of water

• Efficiency increases with significant hot water use late in evening

• Efficiency decreases with significant hot water use early in morning

• Need for new intelligent self learning Hot Water Control Systems

• Optimum orientation is 10 – 20 degrees west of south

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.• Need for integrating behavioural use in design on

control of solar thermal systems.

Keith Tovey ( 杜伟贤 ) M.A., PhD, CEng, MICEHSBC Director of Low Carbon Innovation: and Charlotte Turner: School of Environmental SciencesCRed