Generating electricity from the sun - Photovoltaics (PV)
Photovoltaic cells use light to generate electricity. There are a number of PV panel technologies, including polycrystalline, monocrystalline and thin-film. Solar PV cells can be arranged in panels on a building’s roof or walls, and can often directly feed electricity into the building. With the latest PV technology, cells can also be integrated into the roof tiles themselves. Groups of solar PV cells can be added together to provide increasing levels of power. This can range from small, kilowatt-sized solar panels for use in domestic households, to larger arrays, which function as separate solar power plants feeding power directly into the electricity grid.
PV panels are particularly suitable where a grid connection is difficult and the popular combination of a micro-wind turbine and PV panel uses the fact that there is more wind in the winter when the sun is weak and vice versa to provide a more reliable energy supply. You may have seen this technology on temporary signage on the motorway; a typical combined solar and wind application.
Small scale stand-alone PV applications
There are currently thousands of very small scale PV powered systems in use in the UK, for applications such as phone booths, traffic monitoring, street lighting, road signage. In the leisure industry there has been a significant take-up of PV technology for battery charging on boats, caravans and motorhomes and in garden applications such as lighting and powering aquatic features.
Click here for links to Mobile & Off-grid PV Applications
PV for Transport
PV systems have been incorporated into experimental vehicles for many years. There are even races such as the 3000km World Solar Challenge in Australia for PV powered vehicles but, as yet, no serious commercial transport applications.
However, one of the major UK food retailers is experimenting with trucks that have PV panels on the roof that power the refrigeration unit keeping the load frozen. PV has also recently been used for powering tractor mowers in the US which seems a promising avenue as grass only grows when the summer comes around and PV is most effective.
The US website Green Car Congress is an excellent site providing news and information on developments for sustainable mobility.
Click here for links to PV Powered Transport Companies and Organisations
PV for Buildings
PV heating systems are generally significantly more expensive than solar heating systems, but they do have the advantages that there are no moving parts so simpler and more reliable to maintain and waterproof PV panels can be incorporated into a roof as part of the structure replacing tiles.
A typical domestic 1 kilowatt (1kW) system will cover about 10 square metres, and produce about 750kWh (units of electricity) over a year - mostly in the summer. At that level the payback on £5000+ system is very long even with the grants available, and it is not yet a viable technology where one might consider selling any excess to the grid unless one installs a large array.
The cost of PV systems is falling as the efficiency of solar panels increases and the cost of manufacturing declines due to the introduction of new technologies, such as thin-film solar PV. The DTI’s Renewables Innovation Review estimated that solar PV could become cost-competitive with other forms of electricity generation by 2020–30.
The CIS tower in Manchester is Europe’s largest vertical solar array. Three sides of the 25 storey building's service tower are clad in 7,244 solar photovoltaic panels. The tower also has an urban wind farm on its roof, made up of 19 1kW wind turbines.
Click here for links to PV Panel Manufacturers & Suppliers
To install a grid-connected system, you will need permission from the local Distribution Network Operator (DNO). This is the company who operates the distribution network in your area, and may not be your electricity supplier. DNOs have different policies when it comes connecting small scale renewable generation systems to their networks. To find out who your local DNO is visit the British Photovoltaic Association website, from where you can also download application forms for DNO permission.
The Distribution Code of Licensed Network Operators: www.dcode.org.uk
You will need an inverter to transform the low-voltage DC power produced by a PV roof or wind turbine into high-voltage AC power that meets the quality requirements of the electricity network.
Look for inverters that meet the Engineering Recommendations G83/1 - 'connection of small-scale embedded generators in parallel with public low-voltage distribution networks', which sets out technical requirements that small-scale generators need to meet in order to connect to the mains network. These are only recommendations, but as they have been agreed by the DNOs, applications that conform are usually processed more quickly.
Solar photovoltaics is one of the supported technologies within the DTI's Low Carbon Buildings Programme providing grants for microgeneration technologies for householders, community organisations, schools, the public sector and businesses. Visit our Grants page for details.
British Photovoltaic Association: www.pv-uk.org.uk