Alternative Energy Blog

Alternative Energy presents Applications of Solar Thermal Technology

Here on Alternative Energy we are pleased to present you with articles from our guest writers on a wide variety of alternative energy topics. We hope you enjoy this one:

Applications of Solar Thermal Technology
By Adrian Greetham

Solar thermal technology has a variety of domestic, commercial and industrial applications. They range in scale from simple cooking techniques, to large scale industrial power generation.

Cooking

There are two main types of solar thermal cooking technologies, direct solar concentrators and solar ovens.

Direct solar concentrators

Direct solar concentrators use reflectors to focus the suns rays onto a cooking container, achieving temperatures as high as 350°C. The reflectors used vary in design, with disc, flat plate and parabolic trough the most common types. They all require direct sunlight to operate and thus are most commonly used in countries where overcast days are rare.

Solar ovens

Solar ovens basically comprise of an insulated, internally reflective box with a transparent lid. Pots are placed within the box and can be heated to temperatures between 50 and 100°C. Although the temperatures are significantly lower than those achieved using direct solar concentrators, this system does have the advantage of being able to operate on overcast days.

Water heating

Domestic water heating is the most common use of solar thermal energy. In these systems solar energy is collected via solar panels and used to provide a significant portion of the total energy requirement for water heating within a home. This results in dramatically reduced conventional energy bills, particularly during the summer months.

These systems operate by either heating water directly within the solar collectors or by heating a transfer fluid that is then used to heat water via a heat exchange system. The water is moved from the collectors to a water tank either passively using thermodynamics or actively with an electric pump system.

There are two main types of solar collector, flat panel and vacuum tube. Flat panel collectors are cheap but inefficient whereas vacuum tube based collectors are more efficient but more costly.

Room heating, cooling and ventilation

Solar thermal technology can be used for both heating and ventilating rooms.

Room heating

Room heating is achieved by using materials of high thermal mass such as concrete, water or stone to store solar energy during the day, which can then be released when room temperatures drop.

Room cooling

It may seem odd that the suns heat can be used to actually cool air spaces but it is in fact true. There are multiple methods of solar air cooling one example being an absorption refrigerator. This works by using a source of heat (the sun) to drive a cooling system.

Ventilation

One example of a solar thermal ventilation system is the solar chimney. Solar chimneys use solar energy to heat air within them causing an up draft and therefore circulating air throughout a building.

Power generation

Solar energy can be used to generate electricity. This is achieved by using solar energy to drive steam or gas turbines. To reach the extreme temperatures required for efficient conversion to electricity, solar radiation must be concentrated by lenses or mirrors. This is known as concentrated solar power. As the sun moves throughout the day the lenses or mirrors used to concentrate the sunlight must also move to ensure that the solar radiation is focused in the correct position.

There are a variety of methods for concentrating the suns radiation and tracking the sun:

Solar towers

These consist of a central tower which houses a receiver for the solar radiation and an array of flat mirrors that reflect sun light onto the receiver. The mirrors are movable so that they can track the sun to maintain focus upon the receiver.

Parabolic trough

This is a curved reflective trough which reflects sunlight onto a pipe which contains a heat transfer fluid. The pipe is positioned above the reflectors and runs parallel to them. The trough can be tilted so that it can follow the position of the sun and maintain the focus of the suns radiation on the pipe. This design is less efficient than the solar tower system described above as the temperatures reached are lower.

Dishes

Dish systems use a large, reflective dish to focus light on a receiver that is positioned above the dish. The parabolic dish is movable so that it can track the suns position and maintain optimal focus.

Solar Energy Solution install solar panels for solar water heating across the UK.

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Alternative Energy presents Ethanol Fuel

Here on Alternative Energy we are pleased to present you with articles from our guest writers on a wide variety of alternative energy topics. We hope you enjoy this one:

Ethanol Fuel
By Levi Quinn

Ethanol is a fuel that is alcohol based and is made by distilling and fermenting crops which are broken down to very simple sugars. In some parts ethanol is usually made from crops that are starchy like the sorghum or maize. Research shows that consumed ethanol production was about eleven percent in the United States from all the corn that was grown in the year two thousand and four. In other parts ethanol is created from sugar cane where by those parts set goals of having all the cars that are on their roads to be using gasoline or ethanol. Ethanol is mainly used in alcoholic beverages as well as producing fuel that is referred to as the biofuel an alternative fuel to gasoline. Ethanol is very easy to process as well as manufacture; it also is renewable unlike the petroleum that can not be renewed.

To produce ethanol there are a few steps to follow the first one is fermentation, ethanol usually is made by means of microbial fermentation of sugar, which only works with sugars directly.

There are two components of plants that are major and both made of the sugars this is the cellulose and starch, which principally can be converted to sugars to use in fermentation. The corn and the sugarcane are the only economical sugars that can be converted with the many activities in the cellulosic ethanol, in which the cellulose area of the plant is usually broken down and converted to ethanol. For ethanol to be used as fuel it undergoes the distillation process where most water is removed through distillation, however it does not all come out so it undergoes a another process called dehydration with which there are five stages that are undergone to remove the water that remained from the azoetropic the ethanol and water mixture.

The process entails the azeotropic distillation that involves adding the cyclohexane and the benzene to the azeotropic. When added, they form vapor-liquid-liquid equilibrium then it is distilled it generates anhydrous ethanol and a mixture of water vapor and benzene or cyclohexane it then is condensed and creates two phase mixture of liquid. An alternative way known as the extractive distillation, is adding the ternary components increasing volatility of ethanol relatively. When distilled it produces ethanol that is anhydrous at the top of the column. There are engines that are specifically designed to use the ethanol based fuel which is commonly used by the automobile vehicles, though other vehicles are able to consume it to. With the ethanol blends a problem arises when less vapor is evaporated to spark the ignition, the ignition does not start for the cold weather affects the temperatures of the car hence not enough heat to boost vaporization. Ethanol consists of approximately thirty four percent less energy that is used per unit in volume compared to the gasoline consumption. Ethanol is also used to help in developing airplanes fuel for it is economical and in the electricity transformers that supply electricity.

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