WHAT IS SOLAR?
Solar energy is the cleanest and most inexhaustible of all known energy sources. Solar radiation is the heat, light and other radiation that is emitted from the sun. Solar radiation contains huge amount of energy and is responsible for almost all the natural processes on earth. The sun energy, although plentiful, has been hard to directly harness until recently.
Solar Energy can be classified into two categories, Thermal and Light. Photo-voltaic cells (PV) use semiconductor based technology to convert light energy direct into an electric current that can either be used immediately or stored in a battery, for later use. PV panels are now becoming widely used as they are very versatile, and can be easily mounted on buildings and other structures. They can provide a clean, renewable energy source which can supplement and thus minimize the use of mains electricity supply. In regions without main electricity supply such as remote communities, farms, isolated points etc. PV energy can provide a reliable supply of electricity. The disadvantage of PV panels is their high cost and relatively low energy conversion rate ( only 13 - 15%). Thermal solar on the other hand has average efficiency level 4 - 5 times that of PV, and is therefore much cheaper per unit of energy produced.
Thermal energy can be used to passively heat buildings through the use of certain building materials and architectural design or used directly to heat water for household use. In many regions, solar water heaters are now a viable supplement or alternative to electric or gas hot water production.
Thermal energy obtained from the sun can be used for a number of applications including producing hot water, space heating and even cooling via use of absorption chilling technology.
Using solar and other forms of renewable energy reduces reliance on fossil fuels for energy production, thus directly reducing CO2 emissions. CO2 emissions contribute to global warming, an environmental issue which is now of great concern. The average household can reduce can reduce CO2 emissions by as much as 20% by installing a Sun Power Green Energy solar water heater.
Flat plate thermal solar collectors have been in use for several decades, but only in relatively small numbers, particularly in Western countries. Evacuated tubes have also been in use for more than 20 years, but have been much more expensive than flat plate, and therefore only chosen for high temperature applications or by those with money.
In recent years the production volume of evacuated tubes has exploded, resulting in greatly lower manufacturing and material costs. The result is that evacuated tubes are now similar in price to flat plate, but with insulating benefits of the evacuated tube, they are set to become the default choice for thermal solar applications worldwide.
Currently Sun Power Green Energy solar collectors are reducing CO2 emissions by more than 13,000 tonnes/ 28.6 million pounds per year, with collectors installed in the UK, USA , New Zealand, Germany, France, Sweden, Italy, Hungary, Portugal, Jordan, Lebanon, Australia, Canada, Mexico and many other locations.
There has been a great deal of information in the media over the past few years about global warming and the role of CO2 emissions. 2003 saw extremely weather conditions and a heat-wave throughout Europe, clear evidence of the realism of this problem, commonly referred to as the "greenhouse effect." Burning fossil fuels such as coal for electricity production, and gas for water heating both release large amounts of CO2 into the atmosphere, thus contributing to this environmentally harmful phenomenon.
By using renewable energy sources such a Solar Thermal, Solar PV, Wind, Hydro and Geothermal, reliance on fossil fuels can be minimized, thus directly reducing CO2 emissions. On average for every 1kWh of energy produced by a coal power station., 1kg (2.2 pound) of CO2 is produced. Burning natural gas for electricity production or water heating produces about 450grams of CO2 for every kWh of energy produced.
In the average household, water heating accounts for around 30% of CO2 emissions. By installing a solar water heater, which can provide between 50-70% of your hot water heating energy needs, you can reduce your total CO2 emissions by more than 20%.
Evacuated tubes are the absorber of the solar water heater.They absorb solar energy converting it into heat for use in water heating. Evacuated tubes have already been used for years in Germany, Canada, China and the UK. There are several types of evacuated tubes in use in the solar industry. Sun Power Green Energy collectors use the most common "twin-glass tube". This type of tube is chosen for its reliability, performance and low manufacturing cost.
Each evacuated tubes consists of two glass tubes made from extremely strong borosilicate glass. The outer tube is transparent allowing light rays to pass through with minimal reflection. The inner tube is coated with a special selective coating (AI- N/A) which features excellent solar radiation absorption and minimal reflection properties. The top of the two tubes are fused together and the air contained in the space between the two layers of glass is pumped out while exposing the tube to high temperatures. This "evacuation' of the gases forms a vacuum, which is an important factor in the performance of the evacuated tubes.
Why a "vacuum" As you would know if you have used a glass lined thermos flask, a vacuum is an excellent insulator. This is important because once the evacuated tube absorbs the radiation from the sun and converts it to heat; we don't want to lose it!! The vacuum helps to achieve this. This insulation properties are so good that while the inside of the tube may be 150oC/304oF, the outer tube is cold to touch. This means that evacuated tube water heaters can perform well even in cold weather, when flat plate collectors perform poorly due to heat loss (during high Delta- T conditions).
In order to maintain the vacuum between the two glass layers, a barium getter is used (the same as in television tubes). During manufacture of the evacuated tube this getter is exposed to high temperatures which cause the bottom of the evacuated tube to be coated with a pure layer of barium. This barium layer actively absorbs any CO, CO2, N2, O2, H20 and H2 out-gassed from the evacuated tube during the storage and operation, thus helping to maintaining the vacuum. The barium layer also provides a clear visual indicator of the vacuum status. The sliver colored barium layer will turn white if the vacuum is ever lost. This makes it easy to determine whether or not a tube is in good condition. Evacuated tubes are aligned in parallel; the angle of mounting depends upon the latitude of your location. In a North South orientation the tubes can passively track heat from the sun all day. In East West orientation they can track the sun all year round.