Table of contents :

• hybrid solar lighting (HSL) would reduce this energy usage with fixtures that supplement or completely replace electric light with sunlight, at times when it’s available. Scientists are developing a technology to save energy by transmitting sunlight into buildings through tubes. Indoor electric lighting is the largest consumer of electricity in commercial buildings. In the system, a rooftop collector concentrates and sends sunlight through optical fibers, tubes made of special, high-purity material that transmit light by reflecting it down their inner walls. The fibers would transmit sunlight to special fixtures inside the building, which also contain high-efficiency fluorescent lighting. When the transmitted sunlight completely illuminates each room, the electric lights stay off. When less natural light is available during cloudy days and at night, a sensor activates controls that increase electric lighting adequately to supplement natural lighting and maintain desired illumination levels, according to the magazine. The Oak Ridge labortory plans to help install hybrid solar lighting at the headquarters of the Sacramento Municipal Utility District in Sacramento, Calif., under a contract by the California Energy Commission. The laboratory also plans to install an HSL system in a Wal-Mart store in Kauai, Hawaii, to evaluate energy savings and sales trends associated with HSL daylighting.
• fossil fuels such as oil and natural gas are organic materials made up of carbon and hydrogen. The consensus view is that all commercially viable petroleum and natural gas is made by biological processes - although methane can also be made in small amounts within volcanoes. In fact, the recent detection of methane in Mars's atmosphere has been interpreted as evidence either of ongoing volcanic activity or of life. Methane can be made in the lab from non-biological material by squeezing together water, iron (II) oxide and calcite between 2 flattened diamond tips at 50,000-110,000 times the pressure at sea level, and heating the mixture to 1,500 °C. : it is stable at the intense temperatures and pressures found in Earth's mantle, 100-300 km beneath the surface. Because the mantle makes up 80% of the planet's volume, much more carbon in the Earth could be in the form of hydrocarbons than we previously imagined. The methane result has already increased speculation that oil and natural gas reserves may exist in the mantle, ready to be tapped into, but you probably won't be able to drill for it, because it's far too deep. Oil wells usually only drill down to between 5 and 8 km below Earth's surface, into relatively low-pressure regions. The best way to obtain methane generated in the mantle would be to look for pockets in the crust where rising gas has become trapped. But the amount of gas is unlikely to be significant compared with the oil and gas reserves we already know about : by the time the gas has reached the upper crust, most of it will have dispersed. The mechanism for methane production might also be at work on other planets : a hydrocarbon-rich body such as Saturn's moon Titan could produce hydrocarbons throughout its interior (even near its centre, the pressure is within experimental range). Methane could also be present in Mars's mantl, : this might explain recent observations of methane in Mars's atmosphere, without any need for martian creatures. But the result could still be good news for those hoping to find life on the red planet as methane could be used as a fuel source by life forms
• hydrogen : fuel cells have long been lauded as the 'green dream' of energy. The cells combine oxygen and hydrogen in a kind of battery, producing electricity. The only waste product is water. But although oxygen can be extracted free from the air, hydrogen is harder to come by
• the main method of large-scale production involves reacting hydrocarbons with steam at high temperatures and pressures. Most hydrogen is currently made from methane, in a process that releases CO₂ into the atmosphere. Splitting water molecules with huge amounts of electricity generates hydrogen - but the electricity is likely to have been generated from fossil fuels. Although this may shift urban pollution to out-of-town electricity plants, it makes little difference to greenhouse-gas output, or to free countries from relying on oil and coal for their energy needs. The only technology that can currently make large amounts of hydrogen without using fossil fuels relies on :
• renewable power sources : converting every vehicle in the USA to hydrogen power would demand so much electricity that the country would need enough wind turbines to cover half of California or 1,000 extra nuclear power stations. In the UK the hydrogen switch would require 100,000 wind turbines, enough to occupy an area greater than Wales^ref.
• nuclear energy : public opposition to nuclear energy deters many politicians
• another potential source of hydrogen is alcohols such as ethanol. The USA produces about 2.8 billion gallons of industrial alcohol a year by fermenting plant matter such as corn. This ethanol is added to petrol to make it burn more cleanly. Researchers have found several ways to pull hydrogen from ethanol, but this has generally proven difficult and costly. Now Lanny Schmidt and colleagues at the University of Minnesota have made the process cheaper and easier - perhaps enough so to make it an economically viable source of hydrogen^ref. The team says that when their process is optimized it should be able to produce electricity at around 4 cents per kW-hour, rivalling the costs of conventional electricity. The reactor pushes a mixture of watery ethanol and air over a rhodium-based catalyst heated to about 700°C. It takes only 5 seconds to start up, and produces a steady stream of hydrogen and CO₂ with very few other waste products. The process therefore still produces greenhouse gas, but because it is more efficient than burning fuel it should belch out less pollution for the energy it produces, say the researchers. Ethanol in car engines is burned with 20% efficiency, but if you used ethanol to make hydrogen for a fuel cell, you would get 60% efficiency. Ethanol can usually only be burnt if it is completely free of water - and getting the water out is an energy-intensive process. Schmidt's reactor works with wet ethanol. The hydrogen that comes from the reactor is only about 50% pure, which makes it unsuitable for some fuel cells that easily become clogged by impurities. But the mix can be tolerated by one type of cell called a solid oxide fuel cell. Such cells are typically better for stationary applications, such as powering a house that's far from power lines, as they tend to run best at very high temperatures. For cars, most research has focused on another type of fuel cell - a proton exchange membrane (PEM) - which generally requires a cleaner source of hydrogen. For portable devices there may be even better options : the best solution for 'green' transportation is fuel cells that burn methanol, rather than hydrogen. Methanol, or wood alcohol, can be produced from plant cellulose on a much larger scale than ethanol, and the process makes more efficient use of the whole plant
• scientists have found a way to harness the Sun's energy to extract zinc metal, which can then be used to produce hydrogen simply by pouring water over it. With improvements, the process may prove a cleaner, more efficient way of producing hydrogen for fuel-cell-powered vehicles, which would emit nothing more polluting than water. Current methods of producing hydrogen gas rely either on the fossil fuels they purport to replace, or water-splitting technology that has so far been too inefficient to deliver cheap hydrogen. It has long been known that metals such as zinc can release hydrogen from water. But purifying the metal is the hard part. The traditional method of obtaining zinc involves many chemical steps, baths of acid and masses of electricity. Researchers at the solar-powered plant of the Solar Research Unit at the Weizmann Institute of Science in Rehovot, Israel, have found a better way to deliver the metal. They use 64 7-m-wide mirrors to focus a beam of sunlight onto a tower containing the mineral zinc oxide and wood charcoal. The beam delivers 300 kW of power, heating the chemical reactor up to 1,200 °C and delivering up to 50 kg of powdered zinc per hour. We can imagine solar plants around the Mediterranean producing zinc. As a bonus, the zinc should also be useful for making batteries. Epstein will present results from the SOLZINC project, which includes researchers from Switzerland, Sweden and France, on 8 Aug 2005 at the International Solar Energy Society conference in Orlando, Florida. The process isn't yet entirely clean. The zinc-forming reaction also releases CO from the charcoal, which eventually converts to the greenhouse gas CO₂ in the atmosphere. In a full-scale industrial process, the CO could be harnessed to help produce even more hydrogen from water. But this too would produce CO₂. For now the process produces as much CO₂ as extracting the same amount of hydrogen from natural gas, but the carbon in this reaction is a renewable resource rather than a fossil fuel. Eventually, the team hopes to replace charcoal with agricultural waste. And, if they can get the solar mirrors to heat things up to 1,800 °C, they would be able to extract zinc without any carbon. The work could be useful in sunny climes, but transporting either zinc or hydrogen over long distances is a major hurdle. The team is trying to produce other, lighter metals, such as magnesium, in the same way, although these require hotter temperatures to extract.  If a clean way can be found to make these low-density metals, they could be used to produce hydrogen right in the tank of a car. That would remove the need to transport the gas altogether.
• if we could trap the CO₂ produced by fossil fuels underground, we could convert them to hydrogen. It's not tried and tested, but it's a possibility and it could become a reality by the time we have enough hydrogen-powered cars to make it necessary
• hydrogen-powered vehicles will save thousands of lives a year in the USA alone. If all the nation's vehicles were powered by hydrogen fuel cells rather than fossil fuels, the drop in pollutants that cause asthma, respiratory problems and other potentially life-threatening conditions could reduce deaths by over 6,000 a year. The work challenges a common objection to working towards a 'hydrogen economy', in which hydrogen replaces oil as the main fuel source. Many people argue that because hydrogen will probably be generated by burning fossil fuels, a hydrogen system is no better for our planet than oil. Both produce the greenhouse gas carbon dioxide, although at different points in the cycle of fuel production and use. However, the problem with the internal combustion engine is not just its carbon dioxide emissions. It also produces poisonous carbon monoxide, smog-inducing nitrogen oxides, and ozone, an eye and respiratory irritant. Worst of all, it creates microscopic soot particles that cause a host of health risks and affect climate. Moreover, fossil-fuel vehicles tend to concentrate these pollutants in areas of high population density. Focusing on the health issues of hydrogen vehicles might convey their benefits to policy-makers in a better way than more general talk about emissions and pollution. The effects of replacing all fossil-fuel vehicles in the USA with ones powered by hydrogen fuel cells, which burn hydrogen in air to produce electricity and water, were considered. Such vehicles exist already, although not in large numbers. The team then considered different ways in which the USA might obtain this hydrogen, including extraction from natural gas or coal, or electrolysis of water (which requires electricity, perhaps generated from fossil fuels). They ran computer simulations to determine the state of the atmosphere for each scenario. They also calculated what it would be like if all vehicles were converted to fossil-fuel/electric hybrids, of which there are various models on the market. Regardless of the hydrogen or electricity source, air quality improved in all cases. There was less carbon monoxide, ozone, nitrogen oxides and the eye irritant peroxyacetyl nitrate, as well as fewer sooty carbon particles. This would bring substantial health benefits. The incidence of minor ailments such as headaches, sore throats and eye irritation drops by tens of millions a year in all the scenarios. The number of mortalities caused by air-quality problems falls by up to 6,400 a year with hydrogen cars. Hybrids would save fewer lives than that, but would be better for health than today's fossil-fuel burning cars. Unsurprisingly, the best-case scenario is that in which hydrogen is produced from water using electricity generated by wind turbines. The problem, however, is determining whether these scenarios are feasible. Producing hydrogen from water through wind power is expensive. And there are problems with storing, transporting and distributing hydrogen fuels. Still, focusing on the health effects will help to make the case for hydrogen and renewable energy^ref
Web resources :
• Nature: Fossil Fuels Focus
• Fuel Cell Network
• National Hydrogen Association
• solar energy
• American Solar Challenge (ASC) (2,300 miles (3,700 kilometres) from Chicago, Illinois, to Claremont, California : a 10-day, biannual event)
• World Solar Challenge (WSC) (annual  race across Australia)
A car with a single crew member is allowed up to eight square metres of solar panels plastered over its sleek body : the power gained from an extra four square metres of solar panels will offset the weight of a second person on board. Top-of-the-range solar cells to convert sunlight into electricity are essential for a winning car : today's best solar cells, called dual- or triple-junction gallium arsenide cells, are similar to those used on spacecraft. The cells suck extra energy from sunlight by using 2 or 3 layers, each of which absorbs light of a slightly different wavelength. Though up to 30 times more expensive per watt of power than standard commercial cells, they are around twice as efficient, converting 20% or more of the Sun's energy into electricity. But even coated with such cells, a good solar car generates only 1.6 kW at best - about enough to run a hairdryer. So designers must ensure that all power is channelled to the motor and wheels and not wasted in air resistance and friction.
biofuels : producing biofuels such as ethanol from food crops isn't worth the effort^ref. Researchers should instead concentrate either on producing ethanol from indigestible plant material such as cellulose, or on synthetic hydrocarbon fuels. The comprehensive study finds that if all the corn (maize) produced in the USA in 2005 were removed from food supplies and turned into ethanol, just 12% of US gasoline demand would be offset. Turning soybeans into diesel would account for only 9% of US diesel demand. Contrary to some recent studies, this review finds that corn ethanol and soybean biodiesel do supply more energy than is needed to produce them; soybean biodiesel wins out over ethanol, providing 93% more energy than the amount used in growing, reaping and converting the soy crop to fuel, as compared with 25% for ethanol. Both also reduce levels of greenhouse gas emissions over fossil fuels; biodiesel much more so. But neither biofuel could replace much petroleum without a serious impact on food supplies, the researchers note. Corn ethanol is a first-generation biofuel. It's as likely to realistically meet US energy demand as a Wright brothers' plane would be to fly across the Atlantic. Corn ethanol comes at the price of soil erosion and nutrient runoff. Producing ethanol from cellulose is a much more environmentally preferable option. Cellulose, an inedible plant fibre, could be obtained from switchgrass, a prairie grass that could be grown on abandoned agricultural land. This would avoid destroying natural habitats and would require small pesticide input. Cellulosic ethanol plants are on trial in Spain and Canada. A US Department of Energy report released on Friday 7 July said that biofuels such as cellulosic ethanol could displace 30% of the fuel consumed in US transportation by 2030, which Tilman thinks is a long-term viable goal; although it would take significant technological advances.
• biomass fuels : the diesel fuel in your car could one day come from plants rather than oil wells, according to chemists who have converted plant chemicals into useful hydrocarbons. Biomass fuels are often touted as a green alternative to oil. Although the CO₂ they produce when burnt is a greenhouse gas that contributes to global warming, in theory it should be sucked up by the following year's crop as it grows. The easiest way to extract energy from plants is simply to burn them, and convert the heat to electricity. Although this is good for stationary power plants, it isn't ideal for cars. Electric cars have to be recharged frequently, which may make them unsuitable for long journeys. A better idea is to convert plant material into fuel that vehicles can use directly. This has been done with the fatty acids in vegetable oils, which make up a small part of plant material. But now researchers have found a way to create fuel from the carbohydrates that make up about 75% of a plant's dried weight. The result is a much more efficient use of plant material^ref. The plant-derived hydrocarbons are just like conventional diesel, so they can be distributed through existing infrastructure. This makes the fuel easier to use than hydrogen, for example, which requires a different kind of pumping station and storage system. If all goes according to plan, one could grow enough plants in the USA to power a significant percentage of the country's vehicles. Carbohydrates have proven an expensive source of fuel in the past. Glucose, for example, can be fermented into ethanol and then added to gasoline, but this process is very inefficient, largely because of the energy it takes to boil ethanol away from water at the end of the fermentation. This energy-intensive process could be avoided if plant carbohydrates were converted directly to the long-chain hydrocarbons that make up diesel fuel. Because oil and water do not mix, these hydrocarbons float to the top of the reaction mixture, where they are easily siphoned off. The chemists first used a platinum catalyst to make carbohydrates containing five or six carbon atoms react with hydrogen gas: plant material provides both the carbs and the gas^ref. A magnesium-based catalyst then knits these molecules together to create the longer carbon chains required for diesel fuel. Adding more pressurized hydrogen, and removing any remaining oxygen atoms with a platinum catalyst, delivers the finished fuel. If this can be streamlined into a simpler process, it would be able to compete commercially with ethanol production. The next challenge is to work out how to extract the all-important carbohydrates from plant matter. The chemists used a pure carbohydrate supply in their tests, and plants may have to undergo extensive processing to remove unwanted chemicals. We don't know how dirty a biomass stream we can tolerate
• banana power could soon provide energy for 500 Australian homes. The Australian Banana Growers’ Council has launched a study into the economics of burning or fermenting unwanted fruit to provide electricity. Picky shoppers reject bananas with discoloured skins, so at least 40,000 tonnes of bananas are fed to cattle or mulched in Queensland every year. Researchers at the University of Queensland, Brisbane, will work out the best way to turn this waste into watts.
• ethanol's reputation as an environmentally friendly fuel is overblown, say researchers who claim that large-scale farming of sugar cane or corn for alcohol is damaging the planet. Ethanol is fermented from plant sugars and added to gasoline to boost the oxygen content of car fuels and reduce pollution. Its use is on the rise, particularly in Brazil and the USA. Its proponents argue that using it helps to reduce the amount of CO₂ in the atmosphere, which may lessen global warming. Although ethanol burns just like gasoline, the carbon it releases is absorbed by the plants that will make the next lot of fuel. This means that only a small amount of carbon dioxide (from transport and processing) stays in the atmosphere. But supporters may be ignoring ethanol's other environmental impacts. Producing ethanol-rich fuels tends to reduce biodiversity and increase soil erosion because of the way that sugar cane is grown. In Brazil, ethanol from sugar cane now accounts for about 40% of the fuel in the country's vehicles. In the USA, a relatively cheap blend of fuel, called E85 after its 85% ethanol content, is enjoying a growing popularity. And on 28 June 2005, the US Senate passed an energy bill that requires gasoline suppliers to add 8 billion gallons of ethanol a year to their fuel by 2012, rising from the current consumption of 3 billion gallons. But this increase is bad news for the environment, given the way that crops are currently grown. When the sugar-cane fields are burned, which is done to make harvesting easier, the fires can spread to nearby native vegetation. The energy needed to generate and transport plant fertilizer leads to significant CO₂ emissions, and cleaning the sugar cane also consumes vast quantities of water. In a visit to one of the distilleries I observed about 3,900 litres of water being used per ton of sugarcane. This drain coincides with the dry season, contributing to water shortages and damaging river life (Dias de Oliveira M. E., Vaughan B. E. & Rykiel E. J. Bioscience, 55. 593 - 602 (2005)). The research promises to reignite the debate over whether ethanol is a green energy source. David Pimentel, an agricultural scientist at Cornell University in Ithaca, New York, has famously claimed that ethanol production consumes more energy than it can release in a car^ref, but it has been contradicted by studies from Argonne National Laboratory^ref in Illinois and the US Department of Agriculture^ref. Vaughan and his colleagues claim that their analysis is more thorough because it accounts for the energy consumed in making fertilizer and farming practice. Others say that although it is important to consider the environmental implications of ethanol, it may still be a better bet than gasoline. Ethanol isn't perfect, but I find it hard to believe we'd be better off with 100% petroleum. A significant amount of ethanol production makes use of the waste material left over after sugar cane or corn is harvested for food. Better fermentation using different bacteria has also streamlined the extraction process. Ethanol production efficiency has really improved over the last few years
• methanol : if you can't bear to be away from your laptop during that camping trip to deepest Borneo, help may soon be at hand. Lightweight generators powered by methanol are now on the market... for the rich, at least. The device, designed to specifications for the US Army by the California company UltraCell, weighs just 1.3 kg when fuelled up and is the size of a novel. With a supply of 500 millilitres of methanol, the cell can chuck out 45 watts for a day, which is enough to power a laptop. The cell and fuel together are half the weight of the lithium batteries needed to provide the same power. Unlike traditional generators, fuel cells are totally quiet. And unlike batteries, they can be 'recharged' without being plugged into the wall. Companies such as Toshiba have come up with their own fuel cells for laptops. But most of these products run directly on methanol, giving them a relatively low power output for their weight. UltraCell focused instead on turning methanol into hydrogen inside the device, which lets them pump out twice as much power. The difficulty is that 'reforming' methanol to hydrogen involves a chemical reaction that runs at about 280 °C. As the system gets smaller you really have to work hard to manage the heat. UltraCell has managed to isolate the heat in their cell from sensitive components just centimetres away, and the whole thing is cool enough for you to put your hand on the casing.  Hill won't share the secret of how their insulation system works.  The hydrogen fuel cell in the device is similar to others that are already on the market, with the added advantages of a better catalyst. This helps to keep down the production of carbon monoxide, a by-product that can clog fuel cells. The model now on sale is every bit as impressive as what the big players have been touting for four or five years and haven't shown us yet. With a price tag in the tens of thousands of dollars, the army may be the only customer willing to pay for portable power just now. But it should cost mere thousands in a year's time, opening the market to emergency-rescue crews and others who spend long stints in the wilderness. Hill hopes prices will fall to hundreds of dollars as the technology improves, low enough to tempt adventurous campers. UltraCell plans to develop an even smaller fuel cell that runs at 25 watts, which would be sufficient for a low-power laptop. This lighter device should be much cheaper, and will be available from the end of 2006.
• a German inventor has angered animal rights activists with his answer to fighting the soaring cost of fuel -- dead cats. Christian Koch, 55, from the eastern county of Saxony, told Bild newspaper that his organic diesel fuel -- a home-made blend of garbage, run-over cats, and other ingredients -- is a proven alternative to normal consumer diesel. "I drive my normal diesel-powered car with this mixture," Koch said. "I have gone 170,000 km (106,000 miles) without a problem." The Web site of Koch's firm, "Alphakat GmbH," says his patented "KDV 500" machine can produce what he calls the "bio-diesel" fuel at about 23 euro cents (30 cents) a litre, which is about one-fifth the price at petrol stations now. Koch said around 20 dead cats added into the mix could help produce enough fuel to fill up a 50-litre (11 gallon) tank. But the president of the German Society for the Protection of Animals, Wolfgang Apel, said using dead cats for fuel was illegal. "There's no danger for cats and dogs in Germany because this practice is outlawed in Germany," Apel told Bild on Wednesday in a story entitled "Can you really make fuel out of cats?"
Web resources :
• U.S. Department of Energy Biomass Program
• David Tilman
• geothermal power
• wind turbines : modellers have devised a map that could guide the positioning of wind turbines. It shows wind speeds 80 metres above the ground,which is the right height to turn most turbines' blades and generate electricity. Coming up with speed measurements at this height was difficult. Most windspeed recordings are made about 10 m off the ground, but wind speed increases the higher you go. So the pair had to extrapolate from the few places where wind is measured at 80 metres, deriving models of how quickly the wind speed increases with height in different parts of the world. They then applied these models to thousands of the lower-altitude wind measurements. Electricity generation becomes practical at locations with average wind speeds of about 25 kilometres per hour. The researchers say there are enough places with this kind of wind to produce 72 terawatts of electricity annually, in theory. Just 20% of this could satisfy the world's energy needs. The map definitely would be of interest to the wind power industry. From the early days, there has been an issue with where the resource is. However, there are practical obstacles to producing that much wind energy. Turbines cannot be erected just anywhere; they are big, often noisy, and many worry about their effect on bird populations. Although this limits the potential sites, the untapped reserves of wind power could be even greater than 72 terawatts. All their numbers are low estimate. Some of the world's windiest sites include the North Sea, the tip of South America, Tasmania, and North America's great lakes. The overall champ is Mount Washington in New Hampshire, where winds clock in at 60 kilometres an hour


Tapping the power of the wind doesn't have to mean peppering the skyline with vast turbines. The inventor of a pocket-sized windmill says his tiny device could power wireless networks of sensors in remote locations. Wireless networks have freed us from miles of cumbersome wiring needed to carry information, but the electronic 'nodes' of such networks still need power. If geologists want to place hundreds of sensors on a mountain to monitor seismic activity, for example, they either have to supply electricity using cables or hike out to each sensor every 6 months or so to replace batteries. The problem is keeping the nodes powered all the time. His windmill is about 10 cm across, and is attached to a rotating cam that flexes a series of piezoelectric crystals as it rotates. Piezoelectric materials generate a current when they are squeezed or stretched, and are commonly used to make a spark in gas lighters. Priya has found that a gentle breeze of 16 km/hr can generate a constant power of 7.5 milliwatts, which is more than enough to keep an electronic sensor running. He unveiled his windmill earlier in 2005^ref, and has now followed up with precise details of the device's abilities (Priya S, App. Phys. Lett. 87, 184101 (2005)). The first trials of completely wireless sensor networks used photovoltaic cells for power. But these did not always work, since a spate of cloudy days could cause a node to shut down. The idea failed because light isn't available everywhere and all the time. So researchers have turned to piezoelectric materials that can harvest 'ambient power' from the vibrations around them. Some scientists are trying to use the vibrations of passing cars to power sensors that monitor the structural health of bridges, or to tap the shaking of an aircraft to run sensor networks without needing to pack more wiring into an already crowded hull. We're all trying to scavenge that wasted vibrational energy. His clever contribution to the field is to create vibrations where they do not already exist, from the power of a breeze. The piezoelectric generator is much more efficient way of converting wind energy on a small scale than the conventional generators that create energy for the national power grid from wind turbines. A conventional generator that used a 10-centimetre turbine would convert only 1% of the available wind energy directly into electricity. A piezoelectric generator ups that to 18%, which is comparable to the average efficiency of the best large-scale windmills. Piezoelectric harvesting is a rapidly developing field, which will probably become much more common as electronic circuits get smaller and require less power. Priya has also patented a much smaller device, measuring just 0.5 cm a side. This is driven by a smaller turbine fitted with tiny wind-catching cups, just like the devices used by meteorologists to measure wind speed. He is developing this system to capture energy from even lighter winds.
Web resources :
• Journal of Geophysical Research: Atmospheres
• American Wind Energy Association (AWEA)
• tidal turbines : the biggest tidal project that has been installed is a huge barrage across the river in La Rance, France, which has a capacity of 240 megawatts. The first experimental tidal mills were installed in 2003: a 300-kilowatt turbine was sited off the north Devon coast in Britain and another of the same capacity was placed near Hammerfest, Norway. On September 2004 6 turbines will be attached to concrete piles hammered into the bedrock 9 metres below New York's East River's surface. As the tide surges in and out, the heads pivot to face the current and the blades spin.

Web resources :
• Verdant Power
• Hammerfest Strom
• Marine Current Turbines
• harnessing power from the vertical motion of a walker's hips : hikers toiling under the weight of a heavy backpack needn't just get hot and sweaty from their efforts. Some of the energy they expend in walking can now be captured by a backpack devised by US researchers, which converts it to electricity that can power portable electronics. The pack, which weighs about 20-38 kg depending how much power you need, generated up to 7.4 watts of power when tested on a treadmill. That's enough to keep your GPS locator and a head-lamp running indefinitely in the wilderness - potentially useful for soldiers or rescue workers. They could even take a break now and then without losing power, as surpluss energy is stored in lightweight batteries. Walking is a particularly good source of human power: during steady hiking the muscles produce up to 100 W. As far back as 1967, scientists at the Massachusetts Institute of Technology used piezoelectric devices, which generate electricity when squeezed, inserted into the heel of a shoe to create power for portable electronics such as pacemakers. But mechanical generators housed in shoe heels have tended to be rather cumbersome and fragile. The pack sits on sliding rails, to harness the up and down movement of your hips. The backpack is spring-loaded, so it can bounce up and down when the wearer walks. This moves a toothed rod, which meshes with a gearwheel. As the gearwheel rotates, it generates electricity. The heavier the load, the more power the pack generates. But the researchers were concerned that the shifting load might force the wearer to use more energy in walking, much as a bicycle dynamo puts a greater strain on a cyclist. So they measured the metabolic rates of their test subjects by looking at how much oxygen they consume. To their surprise, they found that the extra energy needed, relative to a fixed pack, was far less than predicted. It seems that the wearers changed their gait to walk more efficiently when wearing the sliding pack^{ref1, ref2, ref3}. This doesn't come as a shock to Andy Ruina of Cornell University in Ithaca, New York, a specialist in the mechanics of walking. He has shown in theory how systems of masses and springs attached to a human body can reduce the energy cost of walking. It seems that Rome and colleagues have hit on a similar arrangement. "There is probably room for improvement both in getting more electricity out and in decreasing the metabolic cost. Perhaps that could one day make it light enough for use by casual backpackers. Such improvements might be made as the pack is developed for commercialization by a spin-off company in Pennsylvania called Lightning Packs. One could then generate electricity while carrying a load more economically and with greater comfort than with a conventional backpack. It would be almost like getting energy for free. This backpack is just the latest in a series of devices that aim to extract energy from the human body. Such devices, which rely on the ever-decreasing power consumption of consumer electronics, could eventually spell an end to the frustration of having your laptop's batteries run out halfway through a long flight. Thermoelectric devices that convert body heat to electricity were explored in the late 1970s, and the Japanese electronics company Seiko used this principle in the 1990s to make a human-powered 'thermic' wristwatch. Also in the 1990s Seiko released its more successful 'kinetic' range of watches, which harvest the energy of movements of the wearer's arm to spin a tiny energy-generating rotor. There may be even more dramatic ways of harnessing power from the human body. Some researchers have devised 'biofuel' cells that produce electricity from the metabolic energy released in living organisms as they burn up glucose. In principle, such a device could be plugged directly into your bloodstream. So far, however, these bio-batteries have been demonstrated only in grapes.

Web resources : Human-powered electronics

• Institute for Biological Energy Alternatives
• Pew Center report on Reducing Greenhouse Gasses
• Renewable Fuels Association (RFA)

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