Photovoltaic (PV)

• PV cells use semiconductors made from monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride or copper indium sulfide to transfer solar radiation into electricity. As these create electricity directly, this is what most people think of when solar power is mentioned. These can be used to generate electricity either in large power plants or in areas where no direct power source is available. This form of solar power has exploded recently, with a 60 percent increase between 2004 and 2009 and a 130 percent leap in 2010, according to the 2010 Global Status Report on Renewables.
  
  

Solar Thermal

• Although still using the sun's power, solar thermal cells are completely different, both in design and application, from PV cells. Solar radiation is used to heat water, which creates steam. This steam is then used to power turbines, which generate electricity. Liquid is either passed through the panel to be heated or the heat is transferred using heat pipe cores. This system is cheaper and more efficient than PV cells, but as it requires steam turbines, has much more limited applications.
  
  

Domestic Solar

• Many people have started to fit solar panels to the roofs of their homes in an attempt to lower electricity costs. These come in two basic forms, which are variations of the PV and solar thermal system. PV cells can be fitted to generate electricity for the whole house. This is an expensive system to install, but will eventually pay for itself. Excess electricity generated can also be sold back to electricity companies. Solar thermal cells are more limited, as installing steam turbines in a house is impractical. Solar thermal cells are used to heat water, which is then used in central heating and to generate hot water. This cuts down on electricity bills and is cheaper to install, but means the house will still get electricity bills as the thermal cells do not generate electricity.
  
  

Practicality

• The major issue with all solar panels is storage. Both PV and solar thermal cells generate electricity very efficiently on clear sunny days, but generate no electricity at night and only a limited amount if the weather conditions are not suitable. This means solar panels are limited in where they can be used, and the power generated during the day has to be stored. For solar thermal cells, this is no problem, as it is a case of keeping the water hot which involves technology not much different than thermal flasks. Storage for PV solar power is more problematic; progress has been made, but no practical storage system is readily available as of 2011.