WHAT IS SOLAR ENERGY ? Solar Energy is the energy received from the Sun that sustains life on Earth. For many decades Solar Energy has been considered as a huge source of energy and also an economical source of energy because it is freely available. Solar energy ,radiant heat and light from sun has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar energy technologies include solar heating, solar photovoltaics, solar thermal electricity and solar architecture.
Solar technologies are broadly characterized as:-1. Passive solar2. Active solar
ACTIVE SOLAR:-Active solar techniquesinclude the use of photovoltaic panelsand solar thermal collectors to harnessthe energy.PASSIVE SOLAR:- Passive solartechniques include orienting a buildingto the Sun, selecting materials withfavorable thermal mass or lightdispersing properties, and designingspaces that naturally circulate air.
In 2011, the International Energy Agency saidthat "the development ofaffordable, inexhaustible and clean solarenergy technologies will have huge longer-term benefits. It will increase countries’energy security through reliance on anindigenous, inexhaustible and mostlyimportant-independent resource, enhancesustainability, reduce pollution, lower thecosts of mitigating climate change, and keepfossil fuel prices lower than otherwise.
Architecture and urban planning Agriculture and horticulture Solar lighting Solar thermal Water heating Water treatment Cooking
Sunlight has influenced building design since the beginning of architectural history. Advanced solar architecture and urban planning methods were first employed by the Greeks and Chinese, who oriented their buildings toward the south to provide light and warmth.
Day lighting systems collect and distribute sunlight to provide interior illumination. This passive technology directly offsets energy use by replacing artificial lighting, and indirectly offsets non-solar energy use by reducing the need for Air-Conditioning. Although difficult to quantify, the use of natural lighting also offers physiological and psychological benefits compared to Artificial lightning.
Solar hot water systems use sunlight to heat water. In low geographical latitudes (below 40 degrees) from 60 to 70% of the domestic hot water use with temperatures up to 60 °C can be provided by solar heating systems. The most common types of solar water heaters are evacuated tube collectors (44%) and glazed flat plate collectors (34%) generally used for domestic hot water; and unglazed plastic collectors (21%) used mainly to heat swimming pools.
Solar distillation can be used to make saline or brackish water potable. The first recorded instance of this was by 16th century Arab alchemists. A large-scale solar distillation project was first constructed in 1872 in the Chilean mining town of Las Salinas.The plant, which had solar collection area of 4,700 m2, could produce up to 22,700 L per day and operated for 40 years.
Solar cookers use sunlight for cooking, drying and pasteurization. They can be grouped into three broad categories: box cookers, panel cookers and reflector cookers.The simplest solar cooker is the box cooker first built by Horace de Saussure in 1767. A basic box cooker consists of an insulated container with a transparent lid. It can be used effectively with partially overcast skies and will typically reach temperatures of 90–150 °C.
Panel cookers use a reflective panel todirect sunlight onto an insulated containerand reach temperatures comparable to boxcookers. Reflector cookers use variousconcentrating geometries(dish, trough, Fresnel mirrors) to focus lighton a cooking container. These cookersreach temperatures of 315 °C and above butrequire direct light to function properly andmust be repositioned to track the Sun.