Solar Energy

There are 2 main types of solar energy…

Passive solar energy

Passive solar energy refers to collection of solar energy simply by the design and materials used in building construction. A greenhouse is probably the best example of a passive solar collector. This type of solar thermal heating has been used widely throughout history, with European buildings and windows often being oriented to the south in order to make the most of the sun’s heat.

Active solar energy

Active solar energy, on the other hand, uses equipment to capture and use the sun’s radiation. Such tools include solar panels and solar concentrating mirror dishes.

There are two main types of solar panel

  • Solar thermal panels use flat plate collectors containing a black metal plate, to absorb the sun’s heat. They are generally mounted onto south facing roofs (in the Northern hemisphere). The collector is also fitted with tubes containing a carrier fluid which can be heated up to 82°C by the plate. This can be used for total water and space heating or as the first heating stage before being boosted by other conventional heating sources.
  • Photovoltaic (PV) panels use solar energy to create electricity. These contain thin slices of semi-conducting materials which convert the sun’s energy into electricity. You can see a simple example of this technology in solar powered calculators.

Of the two, solar thermal is more popular as it is far more cost effective than PV, with PV panels currently being very expensive, and having a long pay-back period.

Solar concentrating reflectors can be used in extremely sunny, particularly desert, areas. They are mounted onto heliostats, which track the sun, and if set up in sufficient numbers, will focus enough solar radiation onto a central ‘power tower’, to heat the water contained within to several hundred and sometimes several thousand °C. The resulting steam drives a turbine, which when linked to a generator creates electricity, as normally happens at a power station. Alternatively, if heated sufficiently, this method can be used to split the water (H2O) into Hydrogen (H) and Oxygen (O2). Hydrogen can then be used as a clean, renewable fuel

Each square metre of the UK receives between 900 – 1200kWh of solar radiation annually. This is equivalent to the energy produced by 1000 power stations. As the average UK household has a footprint of around 50 square metres this means that a total of 45,000-65,000 kWh solar radiation will fall onto a property, each year, even before garden areas are taken into account. With annual UK household energy consumption currently standing at 25,000kWh, we can see that this is more than enough solar energy to tap into for our energy requirements, if it could be captured and used at necessary efficiencies.

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