Wednesday, August 27, 2008

Bio-Fuels I (Willow)

Biofuel can be broadly defined as solid, liquid, or gas fuel derived from recently dead biological material.
Bio-fuels are fuels that can be used to replace polluting fuels such as petrol, without damaging the environment. A fuel such as ‘willow’ is a good example. Willow grows quickly on most land and it can be harvested like any agricultural crop. Whilst it is growing it absorbs carbon from the atmosphere, reducing the amount of pollution in the atmosphere. When it is burned as a fuel it releases less carbon into the atmosphere than it absorbs whilst growing. This means that it is a ‘green’ fuel. It does not increase the amount of pollution in the atmosphere, in fact during its life cycle it reduces these damaging gases.

1. Willow grows quickly and is harvested. The wood is stored until transported to a processing plant for ‘chipping’.
2. The willow is processed. Each trunk is fed through a ‘chipping’ machine - the chippings are collected and packaged for distribution.
3. The willow chippings are fed into a boiler and burned to produce heat. This replaces gas, oil or coal as an energy source. Water is heated and pumped around the building in the same way as in most heating systems.
The boiler for burning chippings is usually slightly more expensive than a gas or oil burning boiler. However, the fuel is cheaper producing savings over a period of time.


Bio-Fuels II from Animal Waste

Another means of generating power is trough animal waste or dumps.
Methane is a gas that can be collected and burned as a fuel. This gas is produced by animal waste, as it decays. Some farms collect animal waste and store it in tanks, processing the collected gas. The resulting methane gas is then compressed in tanks/containers and distributed to customers. It can be used to heat cookers, houses and even to power car engines.

1. The cycle starts with animals on a farm, grazing and producing waste.

2. The waste is collected on a regular basic. It is transferred to decomposing tanks and the methane gas is collected and stored.

3. Gases are stored in tanks and transferred to tankers. It is transported to customers or compressed and transferred to smaller cylinder tanks.

4. The methane gas can be used for household appliances such as cookers. It can also be used as the fuel for cars specially adapted to burn methane gas rather than petrol. These vehicles are less polluting although their speed and acceleration are reduced.


Bio-Fuels from Burning Domestic Waste

Recently interest has grown in the burning of garbage / domestic waste to produce electricity. This is not a new idea although in the past when waste was burned it created pollution that could even be toxic. Today, the technology exists to remove almost all the pollutants from the fumes produced during the energy production cycle. Special filters remove dangerous chemicals and particles that would normally be found in the fumes.

1. The domestic waste is sorted usually by hand to remove materials than can be recycled. Steel is removed using electromagnets and this is stored until there is enough quantity for recycling to be economically viable. Aluminum, in the form of cans is removed by hand.

2. The waste is then ‘dropped’ into the hopper of a furnace. When the doors slide open it falls into the burning chamber. Gas is normally used to start the fire which burns at a high temperature, destroying the domestic waste. While the waste burns it heats a water tank, in turn, producing steam. The steam is used to turn turbines, producing electricity.

Once steam has been produced, the production of electrical power is no different than that used in any other power station. The high pressure steam is used to turn electrical turbines which produce electricity. The advantage of this way of producing electricity is that the domestic waste that would normally be buried in land fill sites or even dumped far out at sea, is burned. This means that vast areas of land that would have to be used for land fill are free for agriculture or for building.

The domestic waste is burned in the furnace. This heats water in a tank producing steam. The high pressure steam is used to turn turbines, producing electricity. The steam produced during the process condenses back to water and is recycled for heating once again. Pollutants are removed from the fumes before they are allowed into the atmosphere.


Bio-Fuels III (Alcohol fuel)

Ethanol (ethyl alcohol) often known as alcohol can be used as an environmentally friendly fuel. Brazil is currently the world’s largest producer having developed its processing industry since the 1970s. Brazil uses ethanol as a replacement fuel for petrol and diesel. Brazil has reduced its reliance on fossil fuels such oil through its enthusiastic use of ethanol. Currently twenty percent of Brazil ‘liquid’ fuel usage is ethanol based.
However, there is a negative side. In Brazil ethanol is processed from sugar cane. Brazil is a vast country and it has the land area to grow thousands of acres of this crop. However, it has been claimed that forested areas have been cut down to provide the land required for this from of agriculture. In the USA maize is being used to produce starch. This can also be processed to give ethanol.

Ethanol from Sugarcane
The first stage in ethanol production is to grow a crop such as sugar cane. The sugar cane of cut down and undergoes fermentation and distillation.

Crushed sugar cane in placed in fermentation tanks. Bacteria in the tanks acts on the sugar cane and in time produce a ‘crude’ form of ethanol. This is then passed on to the ‘distillation stills’ where it is refined to a pure form.

The impure/crude ethanol is heated in a ‘still’ until it vaporizes and rises into the neck where it cools and condenses back to pure liquid ethanol. The impurities are left behind in the still. The ethanol trickles down the condensing tube into a barrel, ready for distribution.

Ethanol can be used as a fuel for cars and Lorries, heating homes to mention a few. When burned it produces fewer pollutants than traditional fuels such as petrol and diesel.


What do you know about solar energy?

Solar energy can be defined in many ways but some of these definitions are highlighted below:
i. It can be defined as the power produce from the radiations of Sun;
ii. Heat and light radiated from the sun;
iii. Energy produced by the action of the sun's light or heat;
iv. The radiant energy of the sun that can be converted into other forms of energy, such as heat
or electricity; and
v. Energy produced by photovoltaic solar cells, which are made of semiconducting materials, to
directly convert sunlight into electricity and lot more.

Solar energy has been looked upon as a serious source of energy for many years because of the vast amounts of energy that are made freely available, if harnessed by modern technology.

A simple example of the power of the sun can be seen by using a magnifying glass to focus the suns rays on a piece of paper. Before long the paper ignites into flames.

This is one way of using the suns energy, but flames are dangerous and difficult to control. A much safer and practical way of harnessing the suns energy is to use the suns power to heat up water.

A magnifying glass can be used to heat up a small amount of water. A short piece of copper tube is sealed at one end and filled with water. A magnifying glass is then used to warm up the pipe. Using more than one magnifying glass will increase the temperature more rapidly. After a relatively short time the temperature of the water increases. Continuing to heat the water will cause water vapour to appear at the top of the tube. In theory, with enough patience, several magnifying glasses and very strong sun light enough heat should be generated to boil the water, producing steam. This is one way of harnessing solar power.

The principle of heating water to boiling point was used by the French in 1888. They developed a solar powered printing press. It used the energy of the sun to boil water, producing steam. The steam was used to drive a steam engine which provided the power to drive the mechanical printing press. The machine was unreliable and very expensive to manufacture.

Modern solar panels are a combination of magnifying glasses and fluid filled pipes. The solar panel seen opposite has a glass front which is specially made to focus the power of the sun on pipes behind it. The pipes carry a special fluid that heats up rapidly. They are painted black to absorb the heat from the sun. The silver reflective surface behind the pipes reflects sun light back, further heating the pipes and the fluid they contain. The reflective surface also protects anything behind the solar panel (such as a roof).

The heat produced in the pipes is then used to heat a tank of water. This saves using electricity or gas to heat up the water tank.

Significance of Solar Energy
1. Solar energy is free although there is a cost in the building of ‘collectors’ and other equipment required to convert solar energy into electricity or hot water.
2. Solar energy does not cause pollution. However, solar collectors and other associated equipment / machines are manufactured in factories that in turn cause some pollution.
3. Solar energy can be used in remote areas where it is too expensive to extend the electricity power grid.
4. Many everyday items such as calculators and other low power consuming devices can be powered by solar energy effectively.
5. It is estimated that the worlds oil reserves will last for 30 to 40 years. On the other hand, solar energy is infinite (forever).

Disadvantages of Solar Energy
1. Solar energy can only be harnessed when it is daytime and sunny.
2. Solar collectors, panels and cells are relatively expensive to manufacture although prices are falling rapidly.
3. Solar power stations can be built but they do not match the power output of similar sized conventional power stations. They are also very expensive.
4. In countries such as the UK, the unreliable climate means that solar energy is also unreliable as a source of energy. Cloudy skies reduce its effectiveness.
5. Large areas of land are required to capture the suns energy. Collectors are usually arranged together especially when electricity is to be produced and used in the same location.
6. Solar power is used to charge batteries so that solar powered devices can be used at night. However, the batteries are large and heavy and need storage space. They also need replacing from time to time.