Among all known energy sources, Solar energy is the cleanest and most inexhaustible one. The sun can emmitte solar radiation, which contains the heat, light and other radiation. Solar radiation is in charge of almost all the natural processes on earth .And it can produce huge amounts of energy. This energy ,although plentiful, has been hard to use directly until recently.

 

There are two categories of Solar Energy : Thermal and Light. Demiconductor-based technology is use in photo-voltaic cells (PV) to convert light energy directly into an electric current that can either be used immediately, or stored in a battery, for later use. Recently PV are widely used for its multi-function and easily mounted on buildings and other structures .Besides they can provide a clean, renewable energy source. By using them,they can minimize the use of mains electricity supply.It is a good choice to use PV energy in regions without main electricity supply such as remote communities, emergency phones etc for its reliable supply of electricity. Compared to thermal solar, the high cost and relatively low energy conversion rate (only 13-15%) is its obvious disadvantage,because thermal solar has average efficiency levels 4-5 times that of PV, and is therefore much cheaper per unit of energy produced.

 

With the use of certain building materials and architectural design,we can use thermal energy to heat buildings passively or heat water for household use directly. Electric or gas hot water production is added or even replaced by solar water heaters in many areas.

 

The application of thermal energy obtained from the sun is various such as producing hot water, space heating and even cooling via use of absorption chilling technology etc.

 

The environmental issue of CO2 emissions is of great concern nowdays for its contribution to global warming.However by using solar and other forms of renewable energy we can reduce reliance on fossil fuels for energy production and reduce CO2 emissions.If a average household install an Sunflower solar collector,they can reduce as much as 20% CO2 emissions CO2 emissions by as much as 20% by installing an Sunflower solar collector.

 

The use of only chosen for high temperature applications or by those with money thermal solar collectors has been lasted for several decades,however it is just be used in relatively small numbers, particularly in Western countries. Evacuated tubes have also been in use for more than 20 years,but it is only chosen for high temperature applications or by those with money, because flat plate is much cheaper than evacuated tube.

 

Recently the greatly lower manufacturing and material costs lead to the production volume breakthrough of evacuated tubes,so now evacuated tubes are as cheap as flat plate. However evacuated tubes are set to become choice for thermal solar applications worldwide for the advantage of insulation