         
Based on an original article by Susan Ballard, updated in 2007 by Jane Pendlenton and Chris Jardine.
Read about how solar energy is turned into electricity, and about the results of a study comparing solar PV performance in the UK and in sunnier places.
Introduction The public perception of solar power may not have shifted since the 1960s. Some of us still only bring to mind rather dull black roof panels providing hot water if the sun shines. Yet space age technology has fuelled a revolution since then that not everyone may be aware of. It is now possible and affordable to generate electricity directly from daylight (it doesn't even have to be that sunny) using photovoltaic cells. Susan Ballard provides a brief introduction.
Photovoltaic Tiles Sections in this article "Photovoltaic" explained Benefits of PV The PV Compare Project, University of Oxford Current projects at the Environmental Change Institute and in Oxford Where Next: including where to find grants for installing PV systems "Photovoltaic" explained "The word "photovoltaic" is a marriage of the words photo, which means "relating to light", and voltaic, which means "relating to electricity". Photovoltaic technology generates electricity from light. Photovoltaics are made out of materials called semiconductors. Typically silicon is used, and it is a sustainable resource, making up 12% of the earth's crust (commonly found in sand). The silicon is sliced into wafers or made into thin layers and assembled into the modules. When light strikes the surface of the silicon, the energy of the light is capable of knocking electrons in the silicon free, so they can move around. Two different impurities are added to the silicon, which sets up an electric field that forces all the free electrons to move in one direction - producing an electric current. The brighter the sunshine, the greater the electric current produced.
Multicrystalline Structure of PV material. There is a whole range of products now available many of which are very beautiful and can enhance the appearance of buildings as well as generating more than enough electricity for everyday needs. Surplus can be sold back to the national grid. Benefits of PV An obvious benefit of using a PV system to provide electricity is that the electricity produced is pollution free at point of production, with no carbon dioxide emissions, or emissions of any kind. Some other benefits are listed below:
The PV Compare Project, University of Oxford One of the assumptions that may be deterring more widespread use of photovoltaic (PV) technology is that it is not suitable for cloudy northern countries like Britain. However, researchers at Oxford University's Environmental Change Institute, set about exploding this myth in a project called ‘PV Compare' which ran from 1999 to 2003. They analysed the performance of eleven different commercially available PV modules. These were set up on a roof top in Oxford and another in Palma in Mallorca. This allowed each product to be tested in identical conditions in different climates. The results of the PV Compare project have helped to identify the best product for different light conditions, providing valuable information for manufacturers, retailers and those of us looking to reduce our carbon dioxide emissions. An array in the UK will produce about 60% of the electricity of an array in Mallorca, from only 55% of the sunshine. Photovoltaics actually operate more efficiently in the UK due to the lower temperatures and the colour of the light received here. Furthermore a clear sunny day in the UK can produce more electricity than a clear sunny day in Mallorca, as our summer days are longer than locations further south. In general a 1 kWp PV system will produce 750-800 kWh of electricity per year. The average household uses 3300 kWh of electricity in lights and appliances, but energy efficiency measures are capable of reducing this to 1500 kWh per year. A 2kWp system could therefore provide all your electricity requirements, and is of the right size for a domestic roof.
PV array at Begbroke Science Park, Oxford Current projects at the Environmental Change Institute and in Oxford Following on from the PV compare project, the Environmental Change Institute undertook further research aimed at monitoring solar panel performance in actual systems in Oxford, and at encouraging awareness and education about PV use. The West Oxfordshire District Council Offices in Witney features 6 solar photovoltaic roofs integrated into the building fabric itself. This means that the roof is actually made of solar material, which performs all the functions of a normal roof (waterproofing, thermal insulation, soundproofing) but generates green electricity as well. Using PV in this way means that the cost of building a conventional roof can be avoided, making the whole system cheaper and more economic.
West Oxfordshire District Council Offices The Oxford Solar Initiative was a not-for-profit public partnership which culminated in an Oxford solar cities conference in 2006. Throughout the project, the partnership facilitated the installation of 80 active solar systems, over 450 energy efficiency measures and 3,000 low energy light bulbs (CFLs). They also produced a map aiming to show the location of all solar energy systems in Oxford city (to access this, see ‘Where next'). The Solar Schools Forum project has collated solar energy teaching materials and lesson plans from all across Europe. Information for teachers can be downloaded from the project website Where Next: including where to find grants for installing PV systems On ClimateX.org A case study featuring an Oxfordshire couple who have installed photovoltaic roof tiles to supply domestic electricity can be found in the article Be Your Own Electricity Generator in this section. To read about the inspirational story of the ongoing conversion of one Oxfordshire woman's ordinary semi-detached house into an ‘ecohouse' see http://www.sageoxford.org.uk/ecohouse.htm External sources of information To read about grant systems available for householders to offset some of the costs of a new PV or solar water heating system, visit the DTI's low carbon buildings programme. This website also contains listings of accredited suppliers searchable by area http://www.lowcarbonbuildings.org.uk/home/ More information about Oxford University's research project, PV Compare, and current initiatives, is available on the Environmental Change Institute's PV pages. The Oxford Solar Initiative provides details about the project and a map of Oxford solar systems. Solar Century is a commercial company that facilitates the take up of PV worldwide. Article by
Susan Ballard
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