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Continuing Professional Development Photovoltaic panel installations


with MCS approved contractors in the early stages of the design to ensure that all installations are to an approved standard.


Hounslow Civic Centre


Specialist sustainable roofi ng company ICB (Projects) installed a large array of SunPower PV panels on the roof of the Hounslow Civic Centre in London. The 151-panel system will generate 39,919 kWh of energy and save over 20 tonnes of CO2


every year. The system will now play a key role in the London Borough of Hounslow


hitting its carbon reduction target of 40% by 2017, as part of the borough’s carbon management plan. It has an expected payback of investment in just eight years; thanks to the government’s feed-in tariff. This is a 20-year subsidy that provides income when electricity is fed back into the mains, meaning that a further 12 years of income/profi t will be added to the council’s funds. As specialists in all aspects of fl at roofi ng solutions, ICB also supplied and


installed its ultra-tough FiberTite single-ply membrane – which is fi ve times tougher than PVCp (plasticised polyvinyl chloride) and TPO (thermoplastic polyolefi n) despite being 67% thinner. The company completed the project with a Barrial safety rail and balustrade system.


>site if the PV array were designed to


meet the minimum or base load daytime electricity demand. It is of course good practice and sensible


to make energy savings where possible and to reduce electricity demand as well as employing renewable energy in whatever form. Good building design will reduce energy waste and reduce the size of the PV array needed to meet a building’s electricity requirements. It is also worth noting that under the current UK government fi nancial incentive, the feed-in tariff (FIT) scheme (see box, p43), the payment per kWh of electricity generated by a PV array will be lower for buildings that fail to meet a minimum standard of energy performance than those that do.


44 | APRIL 2015 | CONSTRUCTION MANAGER Specifi ers and designers should also be


aware that the regulations surrounding the government’s microgeneration certifi cation scheme (MCS) dictate that only approved PV systems installed by registered companies are eligible to receive benefi ts from the feed-in tariff (FIT) scheme. MCS installation companies receive annual audits on their internal quality assurance procedures and also have completed installations assessed. These companies work to a guide that covers the installation of photovoltaic systems, gives industry approved methods for site surveys, system designs, installation and operation and maintenance guidance. Specifi ers should therefore work closely


“The ideal location to optimise output is an unshaded position in a south-facing orientation at an inclination from the horizontal of about 30 degrees”


Maximum capacity of PV array In the domestic market, it is common for installers to recommend the maximum capacity of PV array that can be safely installed on the roof of a house, which is approximately 4kWp, or 4 kilowatt peak. Government fi gures suggest that each kWp should generate around 850kWh in optimum conditions but higher fi gures have been achieved.


This capacity is typically suffi cient to


meet the average UK household’s annual electricity needs. However, how much is consumed and generated may vary considerably between households and a grid connection will remain essential to ensure instantaneous demands can be met. As mentioned above, the location and


orientation of a PV array affects its ability to generate electricity and, consequently, income. The ideal location to optimise output is an unshaded position in a south- facing orientation at an inclination from the horizontal of about 30 degrees. The impact of inclination upon power output is indicative only and varies with latitude, with the optimum angle in summer steeper than that in winter. A system in the north of Scotland will need to be set up differently from one in Cornwall. The level of fi nancial payback received in Scotland will be less, but with UK government incentive schemes there is still a good fi nancial case for the use of PV technology throughout the UK. Where system design allows, it is possible to manually adjust the angle of inclination seasonally, or twice yearly, to optimise power output. This can increase annual power output up to 5%. Greater increases can be achieved by systems that track the sun’s position and optimise both inclination and orientation. However, the use of a fi xed angle of inclination is the most common UK practice, primarily as it provides a better return on investment. Any shadows that may fall across the panels should be avoided, as even a small shadow can severely affect the system’s >


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