Solar energy simply refers to the energy that is derived from the sun, either as light or as heat. As we have discussed in previous articles, every source of energy can be traced back to the sun. From the energy we obtain from food, to the biofuels like ethanol, and even wood. These are all results of plants absorbing light and turning that light into energy to grow. Wind can also be traced to the sun. Different wind patterns are a result of different levels of heating from the sun around the Earth. Even fossil fuels emerge from sun. Plants that have captured energy but died and buried millions of years ago turn into sources like oil and coal.
In recent decades, people have become more aware of the potential behind solar energy and rather than depending on millions of years to mine into the Earth and obtain sources like oil and natural gas, scientists have been coming up with many types of technologies that directly turn solar energy into appliance friendly energy. These technologies essentially cut out the middle man and turn solar energy into useful energy like electricity without any harm to the environment and their efficiency keeps rising.
SOLAR PHOTOVOLTAICS (PV) The most common solar technology seen around the country is solar photovoltaic better known as “solar panels”. The concept of photovoltaics was first discovered by Alexandre- Edmond Becquerel, a French physicist, in 1839. PV gets its name from the proves of converting photons into a voltage. Today’s typical residential solar panel consists of an array of many small individual solar cells. These solar cells are most commonly made of crystalline silicone layers and generally are the most efficient. Second generation solar cells are often referred to as thin- film cells because they are made from amorphous silicon such as cadmium telluride. Third generation solar cells are the newest ones in the market and are composed from a variety of new materials. Some of these new materials being used include solar ink using conventional printing press technologies, solar dyes, and conductive plastics. A single solar cell typically produces about 1 or 2 watts of power. However, when solar cells are connected in series or other configurations to increase power output. A plate of solar cells connected is called a module. Modules have the ability to be used alone or connected with more modules to form an array. PV system can be built and tailored to a specific home in order to meet almost any electrical power need. Currently the largest PV system is located in a utility site in California. This solar power station generates approximately 579 megawatts of electricity.
CONCENTRATED SOLAR POWER (CSP)
Concentrated solar power technology is the second most common solar energy technology. CSP revolves around a very distinct process as PV systems. This technology uses reflectors (mirrors) to concentrate sunlight onto a very efficient collector where it usually heats up a certain working fluid. The working fluid is usually water or molten salt or even synthetic oil. This fluid is heated to produce steam with intensified reflection coming from the mirrors. This steam is then utilized to drive an electric generator or any type of system that can be powered with steam like heat engine or steam turbine to produce electricity. Sometimes these systems integrate a certain tracking system, which follow the path of the sun to increase the amount of sunlight incident to the mirrors. Different configuration of concentrating systems can produce different peak temperatures and correspondingly varying thermodynamic efficiencies, which can be a result of different ways of tracking sun and concentrating sunlight. The four most common types of concentrating technologies include parabolic troughs, linear Fresnel reflector, central receivers and parabolic dish. For the most part concentrating solar power plants are the most cost-effective when operating at a massive scale. The smallest concentrating solar power plant generates almost 1,000 more times the power of a typical home rooftop system. CSP technologies are most suitable for massive power plants and areas where there is minimum cloud coverage and high sun intensity such as deserts.
SOLAR THERMAL COLLECTORS – SOLAR WATER HEATERS
Solar thermal collectors are very similar to PV systems but instead of directly converting sunlight into electricity they convert sunlight into heat. Solar water heaters can provide hot water for a home by running water through a collector where it will be heated by the sun before sending back into the home. The key to solar thermal collectors is increasing the heat transfer efficiency from the collector to the working fluid. The main components of a solar heating system include:
Collectors – catch sun’s heat so that it can later be transferred to a working fluid Working fluid – usually water or specific fluid for application Storage tank – usually a big tank where the working fluid will be stored Heat exchanger – carries out the process of heat transfer Controllers – handle a pump which circulates the fluid