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Sunday, November 18, 2007

Renewable energy

Biomass


This one has actually been around for quite some time - remember wood? Our forests have taken a bit of a bashing but there is actually a little more to biomass than that. Biomass has a growing following as one of the great hopes as a sustainable energy source. High energy crops grown specifically to be used as fuel are being developed. Brazil, famously, has, for some time, been squeezing energy from sugar-cane, and scientists are beginning to consider agricultural and and even animal waste products as possible fuel sources (e.g. some zoos worldwide are using "animal by-products" to keep there electricity on). But it also means we need to face the "great recycler" by contemplating the reuse of our solid waste coming from paper, food and everyday wastes, plastics, wood, glass and tyres. In our rural areas or our factory farms it means
livestock waste and in our cities it means repurposing of sewage. Even such past burners of fossil fuel such as Russia has woken up to biomass(1). They are active in seeking a transition from fossil fuel to wood which they reckon will save between 10 and 20 million tons per year of fossil fuels, primarily coal, and reduce CO2 emissions dramatically. But of course you would expect that considering that Russia is endowed with over a fifth of the planet's forests, more than 177 million acres! Then comes the energy potential of crops such as corn, wheat, and barley. Brazil as mentioned has seen the possibilities of cane sugar and Europe(2) has begun to explore sugar beet. But this "cropucopia" extends even to the humble grasses, the humorously named alfalfa, and is it possible that we will all be in clover with clover? That only leaves the oilseed sources such as soybean, sunflower, safflower - strange to think that such everyday kitchen staples could have an impact on whether or not the planet survives until you ponder that aquatic plants may also play a role in keeping us warm, cold or out of the dark. A generator burning biomass requires crops from 250,000 hectares to match the electricity output of a nuclear power station. But biofuel has its downside, inevitably. If all of the land is turned over to the more profitable growth of biofuel then such essential as wheat and maize may be sacrificed.

Opinion : efficient, viable, relatively clean-burning and available worldwide but can be expensive and may hamper the growing of food for the planet

Geothermal


Living on a volcanic part of the earth can have its benefits. The earth's centre can reach 12,000 degrees F. that heat geothermal systems draw on this hot source(1) . Iceland is triving to be a completely clean, zero-emission energy economy through the boon of geothermal power. The island with 300,000 people is already well on its way to achieving that national goal, with its entire home heating and electricity generation systems renewable today. The biggest remaining hurdles are Iceland's 190,000 cars and trucks, plus its fishing fleet. Iceland has an abundant resource in geothermal energy, which provided 7,608 gigawatt- hours of electricity in 2005. But there are not so many places in the world where this kind of arrangement can be made with Mother Earth. In Asia, Indonesia(3) some time in the next century could be a world leader. Its hundreds of active and extinct volcanoes have been a bane of the country's people, the country is the core of the "ring of fire" with regular eruptions and earthquakes. But it does have an upside Indonesia sits on top of the world's largest geothermal reserves, equivalent to about 16,000 megawatts of electricity - quite enough to keep the country in energy into a distant future, if not perpetually.

Opinion: Inexhaustible where it can be found and tapped, non-polluting; doesn't need structures such as solar panels or windmills to collect the energy--can be directly used to heat or produce electricity, making it very cheap


Sun


These days this is usually energy obtained through the use of solar panels. Although this type of solar power is relatively new, the energy of the sun has been around for quite a few thousand years. "Solar collectors," or, as they are more commonly known as, "solar panels(1)" are the usual way of drawing on the power of the sun. There are two ways in which solar power is converted to energy. The first, "solar thermal applications," involves using the energy of the sun to directly heat air or a liquid. The second, known as "photoelectric applications," involves the use of photovoltaic cells to convert solar energy directly to electricity. Solar power is much feted as a future solution since it uses the sun's light, theoretically available anywhere, solar panels can be attached to almost anything. Photovoltaic cells covering an area of 150,000 square kilometres would be needed to meet US electricity needs for a year. But this hasn't daunted cities such as Melbourne (1) who are going for green sun-based solutions. Solar power costs are falling as oil and electricity costs go up, and concerns over global warming have focused renewed investment in the practical employment of solar energy. As the cells get cheaper more and more companies are seeing the potential for a clean, fast buck(2)

Opinion: Inexhaustible, non-polluting, versatile (can used for powering cars and satellites) but large numbers of solar panels are required to produce useful amounts of heat or electricity and only really viable in parts of the world with lots of sunlight.



Waste

One thing is sure as a species we have become incredibly wasteful. In 1960, the average American threw away 2.7 pounds of rubbish a day. Today, that figure is 4.5 pounds every day! In a last ditch attempt to turn bad to good - waste treatment creates energy in the form of electricity and/or heat from a waste source which otherwise may have ended up in your local landfill The other buzz term for this is "energy recovery." These processes often result in usable fuel commodity, such as methane, methanol, ethanol or synthetic fuels.
Waste-to-energy (WtE) facilities, which generate power by burning trash, have been in widespread operation in the U.S. and Europe since the 1970s and are considered by environmental advocates to be a mixed blessing. They get rid of garbage without adding to already stressed landfills and with the added benefit of contributing electricity to the power grid. But they also generate pollution, usually as a result of burning vinyl and plastics. WtE facilities evolved out of basic incinerator technology that simply burns trash and reduces it to ash and smoke. Waste-to-energy' plants instead use the garbage to fire a huge boiler. When the garbage "fuel" is burned, it releases heat that turns water into steam. The high-pressure steam turns the blades of a turbine generator to produce electricity.
Some critics of waste-to-energy plants are afraid that burning waste will hamper recycling programs. If everyone sends their trash to a waste-to-energy plant, they say, there will be little incentive to recycle. However a recent study of US cities(2) showed that people living in cities with waste-to-energy plants are more educated about municipal solid waste and strongly support their recycling programs.

So, while at first glance, recycling and waste-to-energy seem to be at odds, they can actually complement each other. Balancing the good sense good sense of recycling and controlled burning

Water


The power of water has been around for as long as we know and yet we still have problems maximising its usefulness to our lives. In 2005 this report set a benchmark for water use in the developing world but there are many things which more developed countries might equally think of applying. Falling or running water is ideal for powering a wide variety of tasks. Water power really surged as a solution to energy creation in the 20th century. The development of the electric generator helped increase hydropower's importance. Dams and hydroelectric power plants were built to drive the development of countries as diverse as the USA, China and Egypt(2). In the Asia region the Three Gorges Dam(3) has been a source of controversy ever since its inception. The enormous benefits to China are now, even in official channels, been seen as outweighed by the potential damage, medium term and long-term to the environment and to the Yangtse River itself. Hydroelectric energy is the least efficient way of using land to produce power. One square metre on average produces 0.1 watts.

Opinion:
A huge natural resource which if used carefully can bring enormous benefit but has over the years been seen to have negative impact. As water become scarcer this option may not be continuously or sustainably viable.

Wave


The sea is a vast source of energy but it also presents huge challenges in terms of harnessing that great potential(1). To be economically viable a wave power project needs to work with an area of sea measuring 2.5 miles by 1.25 miles. In this sort of space around 30 wave energy devices can be deployed. These float on top of the sea, transferring energy from the waves to equipment on the ocean floor. The energy is then transmitted via a cable to a substation onshore. Wave power generation is not a widely employed technology, and no commercial wave farm has yet been established.
Constructing devices that can survive storm damage and saltwater corrosion; likely sources of failure include seized bearings, broken welds, and snapped mooring lines. Knowing this, designers try to create prototypes that are so overbuilt that materials costs prohibit affordable production.Wave power will only be competitive when the total cost of generation is reduced. Conversion of marine energy sources, including ocean waves and tidal currents, into electricity is however a rapidly developing industry. Many technologies have been proposed(2) and some have generated electricity at full scale, it is difficult to predict which technology will be economic at large scales of installation. So far the only country which has deployed it successfully is Portugal

Opinion: Inexhaustible, non-polluting, but unreliable and potentially expensive to set up in a way that is robust and accident/fault-free

Wind

Wind has powered sea-going craft for thousands of years. Windmills have provided power for agricultural tasks which have contributed to the growth of civilization. So wind is nothing new. In our times wind generators take advantage of the power of wind. Long blades, or "rotors", catch the wind and spin. As with water in hydroelectric systems, the spinning movement is transformed into electrical energy by a generator powered by the wind force. Wind farms it has been estimated can generate around 1.2 watts for every square metre of land but often their benefits are now being weighed against how ugly these turbines can be in a pristine environment. Large-scale offshore wind farms(3) are not visible from land and according to various studies have no discernible effect on aquatic species and no effect on migratory bird patterns or mortality rates. At the end of 2006, worldwide capacity of wind-powered generators was 73.9 gigawatts; although it accounts for just over 1% of world-wide electricity use(3)

Opinion: Inexhaustible, non-polluting but requires large numbers of expensive-to-maintain wind generators (and thus large land areas) to produce significant amounts of heat or electricity and of course, places with lots of wind, most of the time are required.

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