Archive for the ‘Solar Energy’ Category

Solar Power Tower

December 16, 2009 1 comment

Power towers use a circular or semi-circular array of heliostats (large individually-tracking mirrors) to concentrate sunlight on to a central receiver mounted at the top of a tower.

A heat transfer medium in this central receiver absorbs the highly concentrated radiation reflected by the heliostats and converts it into thermal energy to be used for the subsequent generation of superheated steam for turbine operation. Heat transfer media so far demonstrated include water/steam, molten salts, liquid sodium and air.

Concentrating sunlight over 500 times, power tower technology has the potential advantage of delivering high temperature solar heat in utility scale quantities at temperatures of 500°C or more for steam cycles and greater than 1,000°C for gas turbines and combined cycle power plants.

Parabolic dish collector

December 14, 2009 Leave a comment

Using parabolic dishes is a well-tested approach to concentrate solar radiation, and was an early experimental tool at many locations worldwide. The optical efficiency of parabolic dishes is considerably higher than that of trough, LFR or power tower systems because the mirror is always pointed directly at the sun, whereas the trough, LFR and power tower have a reduction in projected area due to a frequent low angle of incidence of the solar radiation. A schematic is shown in Figure.

A typical Parabolic dish collector system

Solar bowl system

December 5, 2009 Leave a comment

A solar bowl is a spherical dish mirror that is fixed in place. The receiver follows the line focus created by the dish (as opposed to a point focus with tracking parabolic mirrors).

The concentration part of the job is performed using variations of lenses or mirrors that take in the solar rays and concentrate them on to the collectors.

The extreme energy thus produced then gets utilized in a way depending on the type of technology we’re dealing with, i.e. in case of concentrator photovoltaic, the concentrators concentrate the sun light directly on to the high-performance solar cells which convert the thermal energy into electrical energy.

Whilst in case of concentrating solar thermal systems, the concentrated light generates high thermal energy on a heat capturing point the heat from which can then be used directly.

Concentrating photovoltaic and thermal (CPVT)

December 4, 2009 Leave a comment

Concentrating Photovoltaic and Thermal (CPVT) technology produces both electricity and thermal heat in the same module, thermal heat that can be employed for hot tap water, heating and heat-powered air conditioning (solar cooling), desalination or solar process heat.

CPVT systems can be used in private homes and increase total energy output to 40-50%, as compared with normal PV panels with 10-20% efficiency. CST systems have been studied in this work and the relevant types of collectors are discussed in following section.

Concentrating solar thermal

December 4, 2009 Leave a comment

Concentrating solar thermal power (CST) technology uses mirrors to focus the sun’s light on a heat capturing point, the heat from which can then be either used directly or converted to electricity.

Concentrating Photovoltaic

December 3, 2009 Leave a comment

Concentrating photovoltaic (CPV) uses lenses (Fresnel lens for example) or variations of mirrors to focus or enhance the sun’s light on a photovoltaic solar panel or cell. This technology includes both a low-concentration approach, which increases the sun’s magnification by less than 5 “suns,” and high concentration approach, which can increase the magnification by hundreds of suns.  High-concentration CPV uses focusing lenses to concentrate the sun’s rays on a single, high efficiency solar cell that is very small, on the order of 1-centimeter square.

Focusing (concentrating) collectors

December 2, 2009 Leave a comment

There are a variety of types of concentrating solar thermal collectors. They achieve higher temperatures by using a concentrating reflector to direct sunlight from a large area to a smaller receiver and absorber area. A liquid is pumped through the absorber, where it is heated and then sent to a storage system or used directly for heating.

Concentrating collectors work best in climates that have a high amount of direct solar radiation. They do not function as well on cloudy days, when available solar radiation is mostly diffuse. The amount of useful heat they produce is mainly a function of the intensity of solar radiation available, the size of the reflector, how well they concentrate solar energy onto the receiver, the characteristics of the absorber, and the control of the flow rate of the heat transfer fluid.