Building Integrating Photovoltaic

The depletion of fossil fuels and the increasing awareness of greenhouse harmful effects are turning renewable energies into one of the most suitable alternatives for sustainable development. There are many possibilities offered by this field, regarding the sources of energy: hydro, geothermal, solar, waves, wind and biomass. The last three sources are directly dependent on the solar irradiance that constitutes the biggest source of energy for the planet Earth. There are two methods to generate electricity, the first, discovered by Faraday in 1821, involves the relative movement of a conductor within a magnetic field and the second, using photovoltaics cells, produces electricity directly from solar irradiance, without the need of any moving part (Twidell, 2009). This characteristic makes photovoltaic power generation a suitable technology not just to bring electricity to remote areas but also through the contribution of a grid-connected system. The 2003 Energy White Paper from the Department of Energy and Climate Change suggested that after 2020, PV will be able to provide a significant contribution to the UK's energy consumption (www.decc.gov.uk). In 2009 there was 32.5 cumulative installed photovoltaic powers, 31.4 more than in 1999; the increase in 2009 over 2008 was 44.4% (Howard, 2009). At present, this technology is still developing and it is likely that the cost of photovoltaic electricity will fall considerably. Furthermore, the development of third generation devices (dye sensitized and organic semiconductor devices) and nanotechnologies are increasing efficiency and reducing costs. Most photovoltaic collectors now at UK are attached to buildings in the form of roof or wall panels (Howard, 2009). PV systems have no moving parts and consequently require minimal maintenance. They generate clean electricity without greenhouse emissions and operate in silence. In addition, they can be easily integrated into the building's façade and roof and are consequently one of the best alternatives to generate electricity in urban environments (www.nef.org.uk).