Photovotic Cells

Green Energy > Photovotic Cells

The sun is a good, clean, renewable energy source but capturing it isn’t cheap

Slim and rather sophisticated looking, photovoltaic (PV) cells are made from a semi-conducting material, typically silicon, that uses sunlight to create an electric field and stimulate the flow of electricity. This electricity can then be used to power lights and other appliances, for either domestic or other uses.

The good and the bad

PV cells don’t rely on finite fossil fuels and are independent from the price fluctuations that mark the fossil fuel energy market. They use the sun, a clean renewable energy source that isn’t going to run out any time soon. Just as importantly, PV cells don’t emit any harmful greenhouse gases. In fact, a typical , domestic PV system operating will, in its expected lifetime of 25 to 30 years, save the world from around 6900kg of damaging CO2.

At the same time, a PV system can increase the value and overall energy efficiency rating of properties, reducing electricity bills along the way. When sited correctly, PV cells are relatively unobtrusive. They’re silent, have a low visual impact, and are low-maintenance. They’re largely self-cleaning, and, with no moving parts, they only demand the occasional checking of wiring and components.

Unfortunately, as with many new technologies, and other renewable energy solutions, PV installation is expensive. For domestic use, it currently costs around £6,000 to £7,500 to install a 4kWp system. This would generate around 3,400 kWh of electricity per year making a saving or income of about £750 per year.  Click here for more information.

Where grants are available, they can help cover some of the gap; in some cases up to 50% or more of the costs. But after the carrot might come the stick if governments consider that legislation for new builds is needed to force the adoption of renewable technologies. This would help to make PV cells more cost effective for both the domestic and non-domestic client.

PV cells only need daylight so even sun-deprived parts of the globe, such as the UK and Ireland, can benefit from their use. Amazingly, in our less-than-Saharan part of the world, between 900 and 1100 kWh of solar energy falls annually on each square metre of un-shaded surface.

Installation and integration

PV cells use only low voltages and currents, so they tend to be grouped into rectangular, weatherproof modules. These modules are often grouped into arrays to cover a surface large enough to produce the energy demanded of them. The cells can be moulded into solar slates or tiles for integration into roofs, or bonded onto glass or metal sheets and fixed onto brackets just above the roof.

It’s possible to have standalone PV systems, but they require large expensive storage batteries. Typically, PV installations for buildings will be connected to the grid by means of an AC inverter. This enables the system to put any excess energy into the grid, and to receive top-ups when supply is low.

Optimally, PV systems should be installed on a roof or wall facing south, with an optimal inclination of around 30-40º. The surface should be free from any potential shadow obstructions such as trees or buildings. A typical domestic system would provide around 1.5kWp* of power – that’s around a third to a half of the average household’s electricity requirements.

Finally

It’s certain that PV cells will play a part in the drive for zero-carbon homes. They may be pricey at the moment, but they’re flexible, make good use of an obvious renewable energy source, and can be integrated into a range of different environments.

Most likely the use of PV systems will be in conjunction with one or more other forms of renewable energy, such as ground source heat pumps. At present, the adoption of these technologies is at the discretion of developers, but this could change in the face of legislation.

While the cash savings may not be huge, we each have a global responsibility to consider our carbon output. PV systems can be a suitable solution for homeowners and business users wanting to reduce their carbon footprint.

notes
* A kWp is a kilowatt peak hour and is the amount of energy a system can produce when it’s generating at 100%. Current PV systems typically only perform at 12% of maximum output.