RENEWABLE & NON-RENEWABLE ENERGY

By their nature fossil fuels will inevitably run out. Renewable energies will therefore become one of the world's main energy sources in the new millennium

Coal, Oil and Gas are called "fossil fuels" because they have been formed from the fossilised remains of prehistoric plants and animals.

They provide around 66% of the world's electrical power, and 95% of the world's total energy demands (including heating, transport, electricity generation and other uses).

Coal provides around 28% of our energy and oil provides 40%.

Some products of coal combustion have detrimental effects on the environment. Burning coal produces carbon dioxide, among other byproducts. Some scientists believe that, owing to the widespread use of coal and other fossil fuels, the amount of carbon dioxide in the Earth's atmosphere could increase to such an extent that changes in the Earth's climate will occur Also, sulphur and nitrogen in the coal form oxides during combustion that can contribute to the formation of acid rain. This can be largely avoided using ‘flue gas desulphurisation’ to clean up the gases before they are released into the atmosphere. This uses limestone and produces gypsum, but it involves ALOT of limestone. Acid rain is the result of a series of complex reactions involving chemicals and compounds from many industrial, transport, and natural sources. Sulphur dioxide (SO ₂) emissions from new coal-fired facilities are now controlled in many countries. As a result, sulphur dioxide emissions have dropped in those countries even though coal use has increased.

All ranks of coal have some economic value. For centuries peat has been used as a fuel for open fires, and more recently peat and lignite have been made into briquettes for burning in furnaces. Electric utilities and general industry use bituminous coal. Steel producers use coke, or metallurgical coal, a fuel that is almost pure carbon, produced by distilling coal (heating it strongly in the absence of air, so that it does not burn).

The process of producing coke yields a number of chemical byproducts, including coal tar, which is used in the manufacture of many other products. Coal was also used, from the early 19th century to the World War II era, for the production of fuel gas, and coal liquefaction techniques were used to produce liquid oil products. Manufacture of fuel gas and other products from coal diminished as natural gas became widely available. In the 1980s, however, industrialized nations again became interested in gasification and new clean coal technology (CCT). Coal supplies all of the Republic of South Africa's oil needs.

Natural gas provides around 20% of the world’s consumption of energy, and as well as being burnt in power stations, it is used by many people to heat their home, and to cook food.

Easily transported along pipes, it is efficient and gas power stations produce much less pollution than coal power stations.

There are other fossil fuels we can use, but the problem is that they require expensive processes before we can use them.

Coal has many advantages, but also many disadvantages:

Advantages	Disadvantages
Very large amounts of electricity can be made in one place, cheaply	Pollution- coal (not as much in burning oil+gas) creates carbon dioxide which helps the ‘greenhouse effect’
Transporting oil and gas is easy	Sulphur Dioxide is produced by burning coal, which contributes to acid rain. We can reduce this however.
Gas-fired power stations are very efficient	Mining can be difficult and dangerous. Some types also destroy large areas of landscape.
A fossil-fuelled power station can be built almost anywhere, so long as you can get supplies of fuel to it easily	Coal power stations need huge supplies. They need reserves, meaning large areas nearby of land are covered in coal

Nuclear power is generated using uranium. Nuclear power produces about 11% of the worlds energy needs, and produces huge amounts of energy from small amounts of fuel, without the pollution of fossil fuels.

Nuclear power is a well-established source of electricity worldwide. Worldwide there are currently about 430 reactors operating in 25 countries providing about 17 per cent of the world’s electricity. Nuclear reactors are also used for propulsion of submarines and ships, and there are a number of prototype and experimental reactors around the world. At present, only a few experimental fusion reactors exist, none of which produce usable amounts of electrical power.

A nuclear power station

Few nuclear power stations are under construction at present, and some have been cancelled when partly built. This is mainly because of long-term resistance from the environmental movement (in particular since the Chernobyl disaster of 1986), but nuclear power stations are also not competitive with natural gas- and coal-fired power stations at present. It is uncertain whether nuclear power generation will increase or decrease worldwide over the next 50 years. However, the very low carbon dioxide emissions from nuclear power stations compared with coal- , gas- , or oil-fired units mean that there is potentially a future expansion in nuclear power driven by the need to control climate change.

More than 40 million kilowatt-hours (kWh) of electricity can generally be produced from one tone of natural uranium. Over 16,000 tonnes of coal or 80,000 barrels of oil would need to be burned to make the same amount of electricity. Moreover, the amount of carbon dioxide produced in generating one kWh of electricity would be 1 kg for coal, 0.5 kg for gas, and only 10 grams for nuclear power.

Other than economic factors, the main issues limiting expansion of nuclear power are disposal of radioactive waste, including waste left over from decommissioning of old facilities. Since the waste is radioactive, it will take centuries for it to become safe. Also security concerns over stockpiled plutonium, and the historical connection with nuclear weapons. Availability of nuclear fuel is unlikely to limit nuclear power production in the near future.

Advantages	Disadvantages
Nuclear power costs about the same as coal- cheap	Although not much waste is produced, it is very dangerous. It must bee sealed for many years to allow radioactivity to die away
Does not pollute Carbon Dioxide- little pollution
Huge amounts of energy from small amounts of fuel
Produces small amounts of waste
Nuclear power is reliable	A lot of money has to be spent on safety. They are very expensive to build, and even more expensive to decommission

Renewable Energy, energy present in the natural flows of wind, water, and sunlight in the environment and that is continually replenished as quickly as it is extracted and used up. Renewable energy will, therefore, never run out.

Most of the energy sources on Earth originate from the Sun, with the exceptions of the energy in the tides, caused by the gravitational pull of the Moon and Sun, and geothermal energy, which results from the heat escaping from hot rocks 2 km below the Earth’s surface and from the effects of radioactive decay. This solar radiation is converted naturally into various energy streams. Wave energy results from the interaction between the convection-driven winds and the surface of the sea; hydro-energy is produced by the hydrological cycle; and biological energy (biomass energy) is that which is stored in living organisms by the process of photosynthesis. All these forms of energy are available as renewable resources because of the continual replacement of the energy on a daily, or even hourly, basis.

By way of contrast, fossil fuels such as coal, oil, and gas, although originally laid down effectively as biomass, take millions of years to form and need to be regarded as finite, non-renewable resources.

Interest in renewable energy came to the fore during the worldwide energy crises of the 1970s, when high oil prices highlighted the world’s dependence on fossil fuels. Secure and affordable energy provision is vital for nations’ development, as all industrialization, manufacturing, and building programmes consume vast amounts of energy. Since the oil crises of the 1970s, and largely as a result of the increased exploration and exploitation of fossil fuel reserves, the abundant supply of oil and coal across the world has enabled market forces to drive down the price of fuel, and consequently electricity, to a very low level. However, estimates suggest that approximately half of the world’s oil reserves, and a smaller fraction of coal reserves, have been used in little over 200 years. Oil will never completely run out but, as demand outpaces supply, renewables can play a major role in bridging the gap.

As well as future supply problems, the environmental impact of sources of energy based on fossil fuel is rapidly generating great concern as the impact of increasing levels of “greenhouse gases” like carbon dioxide (CO2) on the global weather patterns is becoming more apparent. In addition, unburnt fuel and the products of combustion, such as oxides of nitrogen and sulphur, cause far-reaching damage to health and the environment. Renewable energy is largely available without chemical processes so production of CO2 and other gases involved in renewable energy is very little as they are only generated during the manufacturing and installation of the necessary devices. The burning of biomass, such as wood, does, however, directly produce CO2 as a result of combustion but the gas is absorbed by new wood as it grows and hence the net emission is zero, as long as the fuel crop is completely replenished.

There are three main ways that we use the Sun's energy:-

Solar Cells (really called "photovoltaic" or "photoelectric" cells) that convert light directly into electricity.

In a sunny climate, you can get enough power to run a 100W light bulb from just one square metre of solar panel. We use this method for powering calculators.

Solar water heating, where heat from the Sun is used to heat water in glass panels on your roof.

This means you don't need to use so much gas or electricity to heat your water at home. Water is pumped through pipes in the panel.
The pipes are painted black, so they get hot when the Sun shines on them.

This helps out your central heating system, and cuts your fuel bills. However, in the UK you must remember to drain the water out to stop the panels freezing in the winter.

Solar Furnaces use a huge array of mirrors to concentrate the Sun's energy into a small space and produce very high temperatures. This one at Odellio, in France, used for scientific experiments.
It can achieve temperatures up to 33,000 degrees Celsius.

Solar Energy is radiant energy produced in the Sun as a result of nuclear fusion reactions. It is transmitted to the Earth through space by electromagnetic radiation in quanta of energy called photons, which interact with the Earth’s atmosphere and surface.

The strength of the solar energy available at any point on the Earth depends, in a complicated but predictable way, on the day of the year, the time of day, and the latitude of the collection point.

Advantages	Disadvantages
Solar energy is free - it needs no fuel and produces no waste or pollution.	Very expensive to build solar power stations.
	Doesn’t work at night
Solar power can be used where there is no easy way to get electricity to remote places	Can be unreliable unless you're in a very sunny climate.

Bio-energy is the energy recovered from biomass. Chemical energy is stored by plants as they grow and convert the energy from the Sun using photosynthesis. Before the discovery of fossil fuels biomass supplied all the energy for all industrial and domestic activities. Wood is still the most significant fuel source in developing countries, accounting for 35 per cent of their demands. There is currently a variety of technologies for extracting energy from biomass in various degrees of maturity and financial viability.

Biomass fuels include urban refuse, industrial waste, agricultural and animal residues, sewage sludge, and energy crops. This means that using biomass as a fuel is doubly important. In addition to the obvious benefits of power generation, energy from waste plants can dramatically reduce the volume of waste to be disposed of in landfill sites. In particular, household and industrial waste is, in many cases, being deposited in landfill sites at considerable financial and environmental cost.

The price, or “gate fee”, for taking waste and putting it into landfill is being increased in the UK to promote the viability of deriving energy from waste power plants. The economics of such plants is unusual in that a facility can have a negative economy of scale. If the fuel is of low calorific value and has to be pre-processed or is collected from a distant source then the actual energy produced may be barely more than the energy used to collect and process the fuel. This highlights why the more concentrated fuel supplies are inherently more likely to make financial sense. These strict market incentives need to be balanced against the growing environmental issues associated with landfill and bio-waste disposal.

The most attractive biomass fuels are those that can be used directly, like wood chips and paper. Many biomass fuels, however, are converted into an intermediate fuel like charcoal, bio-ethanol (from sugar cane), sewage gas, landfill gas, and gas from the gasification of energy crops or waste.

The basic thermochemical process involved is pyrolysis, which uses heat to break down the fuel, such as wood, into gas, an oil-like liquid, and a pure carbon char. This pyrolytic technology has been in existence since 1830 and was used extensively to power vehicles during World War II, when oil was scarce. Coal could also be converted into diesel fuel via a gasification process.

Advantages	Disadvantages
Gets rid of waste	Getting enough waste to burn is difficult
Doesn’t use natural resources	Pollution
Cheap	Cannot get the waste materials all year round

The sea, which covers three quarters of the world’s surface, has been little utilized to meet the peoples’ energy needs. Offshore wind energy, wave energy, tidal energy, tidal stream energy, energy from thermal gradients in the sea, and energy from the great ocean currents are all little explored and have enormous potential.

Ocean thermal energy conversion (OTEC) was first proposed by the French scientist Jacques-Arsène d’Arsonval in 1881. A thermal machine or heat engine uses the temperature difference between cold water from the ocean depths and the warm surface water to provide a driving force, using a turbine running on ammonia vapour or some other appropriate working fluid. The temperature difference between the surface and 500 m (164 ft) down is around 20° in many tropical and equatorial zones. This is enough to give a thermodynamic efficiency of 8 per cent. Experimental devices generating up to 20 MW have been tested but are still at the development stage.

Harnessing the great currents of the oceans is an exciting prospect. The Gulf Stream flows at over 80 million cu m/s and the Kuroshivo at just over half that rate. Huge turbines could be used to convert this flow, which has an energy flux of 4 kW/cu m, into electricity. The potential is enormous: the flow rates are higher than those of the world’s rivers combined, but only 10 per cent of the potential energy would be available, as to extract more might induce instabilities in the flow and cause the stream to switch its direction of flow.

Tidal streams, which flow between islands, often at 5 knots or more, can also be harnessed, using water turbines in the flow to provide substantial amounts of energy. The harnessing of these flows is, as yet, in its infancy.

Tidal rise and fall can exceed 10 m in some places, such as the Severn estuary in the UK, making it possible to build a tidal barrage and so generate electricity using water turbines placed in the barrage as the tide flows in and out. A tidal station was built at La Rance, on the French coast, in 1967. The barrage is 750 m long and the tidal rise and fall is over 13 m. The station generates 240 MW of power and is still operating successfully. The Severn barrage has yet to be built.

Wave energy is an important resource if it is harvested effectively. It has been calculated that throughout the world waves dissipate an average of 10 kW/m as they break on the shore. In favoured locations, such as the west coast of Scotland, the average power in a metre length of wave is 40 kW, which in storm conditions can rise to 3 GW. A successful shoreline device is now operating on the island of Islay and generating at a rate of 500 kW.

Waves are generated by wind blowing over the surface of the sea, so the possibility of building offshore wind farms in protected but windy locations is attractive. Farms generating 100 MW have been built off the Danish coast and two 2 MW generators are now operating off the English coast in the inclement environment of the North Sea.

Huge areas of the oceans could be used to grow and harvest biomass. In warm locations off the coast of Florida, giant kelp has been grown and algae have also been farmed. Growing biomass has the added advantage of absorbing carbon dioxide additional to the huge amounts of carbon dioxide already absorbed by the oceans.

Advantages	Disadvantages
The energy is free - no fuel needed, no waste produced.	Depends on the waves - sometimes you'll get loads of energy, sometimes nothing.
Not expensive to operate and maintain	Needs a suitable site, where waves are consistently strong
Can produce a great deal of energy	Some designs are noisy.
	Must be able to withstand very rough weather

Like most other renewable energy sources, hydro-power is indirectly produced by the Sun when water evaporates from the Earth’s surface and is deposited as rain on the landmasses and runs back down to the sea via rivers. The potential energy, or energy due to height, can be extracted by flowing the water through turbines as it moves from a higher level to a lower one. Hydro is already a major contributor to world energy supplies and the technology required to convert this energy into motive power or electricity is very mature. Hydroelectricity has been generated over the past hundred years at prices that can directly compete with oil, coal, and nuclear power stations. About one fifth of the world’s annual electrical demand is met by hydroelectricity and 30 or more countries rely on it as their primary source of electricity. Many of the most suitable sites for hydro schemes have already been exploited, usually by building enormous dams, several of which constitute the largest structures in the world. Many of these schemes have resulted in the displacement of tens of thousands of people to higher ground as large valleys are flooded. This displacement has proved to be a high price to pay and there is growing concern for the safety of many tens of thousands of people who now live under the shadow of these huge dams and who would most likely receive no warning if the dam walls were to fail.

Advantages	Disadvantages
No pollution	The dams are very expensive to build.
Once the dam is built, it is cheap to run	Building a large dam will flood a very large area upstream, which causes habitat problems
VERY Reliable	Finding a suitable site can be difficult
Can be very quick to start up	Water quality and quantity downstream can be affected, damaging plant life
Water can be stored to cope with peak demand
Electricity can be generated constantly

Geothermal energy flows from the core of the Earth, where temperatures are as high as 4000° C. In areas the energy may be extracted directly as hot water for space heating or as steam, and run through conventional steam turbines to produce electricity. Where heat is available in hot dry rocks, it is much more difficult to extract and its successful and efficient extraction is the subject of current research.

The total installed hydrothermal capacity by 1998 was 8,000 MW. In El Salvador, geothermal electricity provides 30 per cent of total installed capacity. Although geothermal energy could make a significant contribution to local energy demand, it still only represents 0.15 per cent of global primary energy demand.

Geothermal energy is an important resource in volcanically active places such as Iceland and New Zealand.
How useful it is depends on how hot the water gets. This depends on how hot the rocks were to start with, and how much water we pump down to them.

Advantages	Disadvantages
No pollution	Hazardous gases and minerals may come up from underground, and can be difficult to safely dispose of.
No fuel needed	Sometimes a geothermal site may "run out of steam", perhaps for decades
Power stations take up little space	The big problem is that there are not many places where you can build a geothermal power station.
Once you've built a power station, it is almost free to run	You need hot rocks of a suitable type, at a depth where we can drill down to them.

As with all renewable energy sources (except tidal and geothermal), the energy in the wind comes from the Sun. One or two per cent of the energy absorbed by the Earth from the Sun is converted into wind via the mechanisms of convection and Coriolis forces. There are extensive sites around the world where the prevailing wind conditions could provide significant wind energy.

The Sun heats our atmosphere unevenly, so some patches become warmer than others.

These warm patches of air rise, other air blows in to replace them - and we feel a wind blowing.

We can use the energy in the wind by building a tall tower, with a large propeller on the top.

The wind blows the propellor round, which turns a generator to produce electricity. We tend to build many of these towers together, to make a "wind farm" and produce more electricity. The more towers, the more wind, and the larger the propellors, the more electricity we can make. It's only worth building wind farms in places that have strong, steady winds.

The propellors are large, to extract energy from the largest possible volume of air. The blades can be angled to "fine" or "coarse" pitch, to cope with varying wind speeds, and the generator and propellor can turn to face the wind wherever it comes from.

Advantages	Disadvantages
No fuel is needed- wind is free	Wind is not always available
No pollution	Suitable areas of land are expensive- near the coast
Land beneath can still be used for farming	Some people feel that covering the landscape with these towers is unsightly.
Wind farms can be tourist attractions	Can kill birds… SPLAT
Can supply energy to remote areas	Can affect television reception if you live nearby
	Noisy

Renewable energy will play an increasingly important part in ensuring supply but it cannot take on the whole burden. The future lies with “clean energy” and that means renewable energy together with nuclear power. This combination is unavoidable if we are to meet the pressing need for energy while reducing greenhouse gas emissions. The current “dash for gas” must ultimately falter. Looking to the second half of the 21st century, when demand for energy will have trebled or even quadrupled, energy supply could well be a mix of renewable energy and nuclear power, with clean-coal technology, gas and declining oil making up the rest. Energy prices will rise, which should encourage people to use energy more efficiently, and impounding of some of the carbon dioxide produced by burning fossil fuel will be essential if carbon dioxide emissions are to be kept within safe bounds.

There is a natural tension between the long-term requirements for successful energy policy and the short-term nature of national governments. The concern for the environment, coupled with the over-reliance on fossil fuels, is a global problem that begs a global response.