Climal.com | Climate Change, Environment, News, Energy, Technology

Solar Electric Power

Solar electricity is generated in one of two ways. The first way is through the use of Solar Photovoltaic Panels, which convert sunlight directly into electricity. These panels are also known as Solar PV panels. The second is through heating systems, which often use large array of mirrors to focus sunlight to such strength that it boils water, or heats gas for use in a generator.

How do Solar Photovoltaic Panels Work?

Solar Photovoltaic panels take advantage of the Photoelectric Effect of certain materials. When sunlight falls on these materials, an electric current is naturally generated within them. This can be tapped by mounting these materials onto panels, which can then the fixed to the rooftops of buildings, on a sun-facing wall or on a stand-alone tower.

Solar photovoltaics are popular for generating clean energy for homes as they are easily fixed to rooftops, which provide a natural tilt to maximise sunlight exposure. Prices are dropping by 3%-5% per year and they can add 10% to the value of your property, potentially giving you a profit from the moment they are installed. Government grants are also available which can cover 50% of the cost of installation. They can supply a large proportion of the electricity needs of a typical home despite being quite inefficient, converting only 10%-15% of the available sunlight into electricity (this is due to the fact that the photovoltaic materials are only sensitive to a small part of the sun's energy), unlike solar hot water panels which can be as much as 90% efficient. However, as more energy is consumed generating electricity than heating water, solar photovoltaics save more carbon dioxide than solar thermal panels do.

How Much Electricity Can I Generate from Solar Photovoltaic Panels?

On average, 1000 kilowatt-hours (1000 Kwh, or 1000 units of electricity) of energy from the sun falls on every square metre of Earth every year. A typical household might consume 3000-5000 Kwh every year, so this could be provided by sunlight shining on 3-5 square metres of ground, or rooftop. The sunny side of a typical rooftop might be 7 metres across by 4 metres in height, giving 28 square metres of roof space. Whilst enough solar energy would fall on this side of the roof to power the house more than 5 times over, the solar PV panels are not 100% efficient so only 10%-15% of this energy would be converted into electricity. This would mean that the Solar PV panels would provide between 50% and 80% of the household's yearly electricity consumption, if they covered this entire area. Note that in Equatorial Regions, as much as several thousand Kwh of sunlight falls on every square metre of earth, whilst Polar Regions may only receive a few hundred Kwh per square metre.

panels on the non-sunny side of the roof, as well as on any sun-facing walls, garage rooftops and in your back garden, but it may be uneconomical. It is commonly thought that, at current energy prices, it could take anything between 20-40 years until the solar PV panels have paid for themselves. However, considering the fact they can add 10% to the value of the property, that energy consumption is likely to rise and the cost of electricity is sure to increase with it, in reality this is not true.

Electricity generated from solar PV panels needs to be used straight away if it cannot be stored in a battery bank, a hydroelectric system or in a hydrogen or aluminium storage facility. For this reason, you will sometimes be using the electricity you generate, but when you are not using all that you are making you will be selling it back to the electricity grid. If your overall electrical consumption is less than your production, you may even make a profit.

Are There Other Ways of Using Solar Energy to Generate Electricity?

Solar Energy can be converted into electricity by focussing it enough to produce considerable heat. The heat can be used to make steam for conventional steam turbine or to create an expansion of gas to drive a Stirling Engine or Updraft Turbine. There are various ways of capturing and concentrating the Sun's energy.

Heliostat Power Stations

Heliostats are small, moveable mirrors which are arranged in an array, covering a large area of land. They are positioned around a tower, which contains a heat-capturing device at its top. The mirrors are constantly adjusting themselves to reflect the Sun's rays to the device at the top of the tower. This produces extreme heat, which can be used to provide hot water or steam for steam turbines.

The mirrors cover a large area of land. Often hundreds of thousands of square metres of mirrors are used, with each square metre providing more than 1000 kwh of energy. It is effectively like holding a huge magnifying glass over the tower.

The heat-capturing device at the top of the tower is usually filled with liquid Sodium. This metal is very good at storing heat for later use, meaning that it can be 'charging up' with heat during the day and then using that heat to generate electricity during the night when it is needed the most.

Parabolic Reflector Generators

Parabolic reflectors are curved dishes or troughs. A satellite TV dish is a parabolic reflector, concentrating the signal from the satellite (which are very weak after travelling hundreds of thousands of miles through space) onto the aerial receiver on the end of the arm, pointing at the dish.

A parabolic reflector with a white or mirrored surface can be used to reflect sunlight onto a heat receiver to boil water for use in a Steam Turbine, or by expanding the gas in a Stirling Engine to generate electricity.

The current efficiency record of 30% was set by a parabolic system using a Stirling Engine. Parabolic reflectors have to be motorised so that they are always facing directly towards the sun, otherwise they do not work. They track the sun across the sky throughout the day, ensuring maximum sunlight capture, but are not very effective on overcast days.