Solar Energy is simply heat and light from the sun. Heat and light, along with other secondary solar resources, accounts for over 99.9% of renewable energy available on Earth; in one-day incoming solar radiation provides enough energy to satisfy global electricity needs for an entire year.
There are two ways of harnessing the radiation from the sun to generate energy:
Photovoltaic (PV) Systems use cells to convert sunlight into electricity. The PV cell is made up of one or two layers of a semi-conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers, causing electricity to flow: the greater the intensity of the light, the greater the flow of electricity. PV cells are sized to in terms of the amount of energy they generate in full sunlight, know as kilowatt peak or kWp. PV systems produce no greenhouse gases and each kWp can save approximately 455kg of carbon dioxide emissions per year, adding up to an average of 11 tonnes over a system's lifetime.
The second method of utilising solar power is Solar Water Heating Systems. The systems use direct heat from the sun that works alongside a conventional water heater. The technology is well developed, and a large range of equipment is available that will suit many application systems. Solar panels, or collectors, are fitted to your roof. These are designed to collect heat from the sun's radiation; a heat transfer system uses the collected heat to indirectly heat water, which is then stored in your Hot Water Cylinder until required. Solar water heating can provide you with about a third of your hot water needs. The average domestic system reduces C02 by around 350kg per year and can save you about £40 a year on you hot water bills, depending on the fuel replaced.
The efficiency of both systems depends on the installation: typically for the North-East of Scotland the panels should be facing between a Southeast and Southwest direction and at an angle of between 33° and 43°.
There are many advantages with using solar energy.
- Solar Energy is a renewable, inexhaustible resource
- Does not produce any chemical emissions
- The systems are silent, have no moving parts and require minimal maintenance
- Costs are falling and efficiency is continually on the increase
There are, however, disadvantages as well.
- The initial cost of the purchase and installation is high
- Areas of little sunlight can be problematic
- Cannot be used at night
There is a common misconception that a PV system will only work when in direct sunlight; a solar panel will produce electricity while sunlight is present, including the light available through cloud cover. The volume of electricity produced will depend on the intensity of the sunlight present, but it will nevertheless continue to produce electricity in relative quantities. However, it is the case that Solar Water Heating systems will rely on direct sunlight.