Engineers at Isentropic Ltd, a company in Cambridge UK, have developed a system fo storing large amounts of energy cheaply using gravel.

Currently, the most economically viable way of storing large amounts of energy is through pumped hydro, in which excess electricity is used to pump water up a hill. The water is held back by a dam until the energy is needed and then released to turn turbines and generate electricity.

Isentopic claims that its gravel-based battery would be able to store equivalent amounts of energy but use less space and be cheaper to set up.

The system consists of two silos filled with gravel. Electricity is used to heat and pressurise argon gas that is fed into one of the silos, heating the gravel to 500°C. When the gas leaves the chamber, it has cooled to ambient temperature but is still pressurised. The pressurised argon is fed into the second silo, where it expands back to normal atmospheric pressure. This process acts like a giant refrigerator, causing the temperature inside the second chamber to drop to -160°C.

In effect, electrical energy is stored as a temperature difference between the two rock-filled silos. To release the energy, the cycle is reversed, and as the energy passes from hot to cold it powers a generator that makes electricity.
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The Solar PowerFlower is a portable concentrated photovoltaic power generator intended for agricultural use.

It was designed by Jason Halpern, co-founder of PowerFlower Solar, who began developing the technology while still a student at the University of Pennsylvania.

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The Plumas and Sierra Counties in California are testing a smart grid using the television broadcasting system’s "white space".

"White space" is the part of the broadcast spectrum left vacant when television broadcasting is switched from analogue to digital. It can transmit data significantly faster than the current standard Internet Wi-Fi, and can be broadcast for extended distances and through obstacles - making it ideal for use in smart grid communications.

The Plumas and Sierra Counties are located in the Sierra Nevada Mountains and present some very technical challenges with respect to wireless coverage - making them a good test site for the technology.

The smart grid trial is being conducted by Spectrum Bridge, which has a database which dynamically assigns white space frequences to prevent interfernce with TV broadcasts, Google which is providing power metering and control software and the local electricity and telecommunications utility.

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Researchers at the Massachusetts Institute of Technology, led by Associate Professor Yang Shao-Horn, in collaboration with Professor Paula Hammond, have found that using carbon nanotubes for one of the battery’s electrodes produced up to a tenfold increase in the amount of power that a lithiun-ion battery could deliver from a given weight of material.

In the new battery electrode, carbon nanotubes are "electrostatically self-assembled" into a tightly bound structure that is porous at the nanometer scale. The carbon nanotubes have many oxygen groups on their surfaces, which can store a large number of lithium ions. This enables carbon nanotubes to serve as the positive electrode in lithium batteries.

Carbon nanotubes are a form of pure carbon in which sheets of carbon atoms are rolled up into tiny tubes. Normally, carbon nanotubes on a surface tend to clump together in bundles, leaving few exposed surfaces to undergo reactions. The "electrostatic self-assembly" process incorporates organic molecules on the nanotubes and they assemble in a way that has a many exposed surfaces.

The new batteries have some of the advantages of both capacitors and conventional lithium batteries. Like capacitors, they can produce very high power outputs in short bursts - but the energy output for a given weight of the new electrode material is five times greater than for conventional capacitors. Like conventional batteries, they can provide lower power steadily for long periods - but the total power delivery rate with the new batteries is10  times that of lithium-ion batteries

In addition to their high power output, the carbon nanotube electrodes showed very good stability over time. After 1,000 cycles of charging and discharging a test battery, there was no detectable change in the material’s performance.

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Four men from the remote village of Licapa in Peru have decided to combat global warming by painting the Andes white.

In the last 35 years, rising temperatures have reduced the size of glaciers in the Peruvian Andes by 22%. The hope is that the whitewash will reflect heat away and stop the glaciers melting.

Peruvian Andes (by Martin St-Amant via Wikimedia)

As eccentric as it may seem, the whitewashing project was selected as one of the top proposals in the World Bank’s "100 Ideas to Save the Planet" competition held last year. As a result, Eduardo Gold, who proposed the scheme, secured £135,000 ($au 227,000) to carry it out. The funds are being used to paint about 70 hectares on three mountain peaks.

The team is using an environmentally friendly paint, based on an old Peruvian formula. It contains lime, egg whites and water.

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Researchers at Purdue University have developed a new highly efficient technique for making hydrogen fuel cells suitable for vehicles. The technology has the potential to be twice as effective as current fuel cells at around half the temperature and much lower pressure.

The process uses ammonia borane, a high hydrogen-content powdered chemical and combines two hydrogen generating processes — hydrolysis and thermolysis — to achieve conditions appropriate for use in vehicles.

Currently hydrogen fuel cells run at pressures of aound 5,000 psi. Hydrolysis alone requires a catalyst to turn hydrogen into energy, and thermolysis requires a temperature of 170°C to function. By combining hydrolysis and thermolysis processes, and introducing ammonia borane into the reaction, the required temperature is lowered to about 85°C and the pressure requirements lower to 200 psi.

The researchers believe that, if this technology can be scaled up, it would be the perfect reaction to generate electricity for hydrogen fuel cell vehicles and small appliances. As well as scaling up the process, the researchers are working on ways to recycle the ammonia borane used in the reaction and return it to its original state.

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The U.S. Department of Energy’s National Renewable Energy Laboratory has developed a new air conditioning process with the potential of using 50 to 90 percent less energy than the best current units.

The process uses a unique combination of membranes, evaporative cooling and liquid desiccants. It uses the desiccant (highly concentrated aqueous salt solutions of lithium chloride or calcium chloride) to create dry air using heat and then uses evaporative cooling to make the dry air cold.

Engineers have known for decades the value of desiccants in air conditioning but, because of the complexity of desiccant cooling systems, they have traditionally only been used in industrial drying processes. To create a device simple enough for easy installation and maintenance, the NREL engineers used thin membranes that simplify the process of integrating air flow, desiccants and evaporative cooling. The air is cooled and dried from a hot-humid condition to a cold and dry condition all in one step.

Because the system uses salt solutions rather than refrigerants, there are no harmful chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs).

The air conditioner uses very little electricity and can be powered by natural gas or solar electricity and will work in all climates.

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Hydrogen can be produced in a way that is carbon neutral by adding bacteria to forestry or household waste in a similar way to that used for biogas production. However, this process does not produce much hydrogen gas for the amount of biomass needed.

Now, researchers at Lund University in Sweden have found that a bacterium called Caldicellulosiruptor saccharolyticus, which was isolated in a hot spring in New Zealand, .produces twice as much hydrogen gas as the bacteria currently used. The discovery increase the possibilities of competitive biological production of hydrogen gas.

According to Karin Willquist, who is presenting a doctoral thesis on the research, "If hydrogen gas is produced from biomass, there is no addition of carbon dioxide because the carbon dioxide formed in the production is the same that is absorbed from the atmosphere by the plants being used. Bio-hydrogen gas will probably complement biogas in the future. A first step towards a hydrogen gas society could be to mix hydrogen gas with methane gas and use the existing methane gas infrastructure. Buses in Malmö, for example, drive on a mixture of hydrogen gas and methane gas."

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Physicists at Boston College have developed a nano-scale solar cell, inspired by the coaxial cable, which offers greater efficiency than any previously designed nanotech thin film solar cell

A limiting factor in making highly efficient thin film sollar cells is the need for the cells to be thick enough to collect a sufficient amount of light, yet thin enough to extract current. The Boston College researchers have found a way to resolve this challenge using a coaxial design for cells constructed with amorphous, rather than crystalline, silicon

The researchers say that the nanocoax cells yield power conversion efficiency in excess of 8 percent, which is higher than any nanostructured thin film solar cell to date.

"Many groups around the world are working on nanowire-type solar cells, most using crystalline semiconductors," said Michael Naughton, a professor of physics at Boston College. "This nanocoax cell architecture, on the other hand, does not require crystalline materials, and therefore offers promise for lower-cost solar power with ultrathin absorbers. With continued optimization, efficiencies beyond anything achieved in conventional planar architectures may be possible, while using smaller quantities of less costly material."

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A team led by Professor Benoît Marsan at the Université du Québec à Montréal say that they have solved some of the problems have been hampering the development of efficient and affordable solar cells.

One of the most promising solar cells designs is the dye-sensitized cell, which was designed in the early ’90s based on the principle of photosynthesis. A dye-sensitized solar cell consists of a porous layer of nanoparticles of a white pigment (titanium dioxide) covered with a molecular dye that absorbs sunlight. The pigment-coated titanium dioxide is immersed in an electrolyte solution with a platinum-based catalyst. Sunlight passes through the platinum-based cathode and the electrolyte, and then withdraws electrons from the titanium dioxide anode.

This type of cell has some problems that have prevented its large-scale commercialisation:

• The electrolyte is extremely corrosive, resulting in a lack of durability
• The titanium oxide is a densely coloured, preventing the efficient passage of light; and
• The cathode is covered with platinum, which is expensive, non-transparent and rare.

Professor Marsan realized that two of the technologies developed for the electrochemical solar cell could also be applied to the dye-sensitized solar cell. Entirely new molecules, created in the laboratory, can be used in a liquid or gel electrolyte which is transparent and non-corrosive -  thus improving the cell’s output and stability - and platinum can be replaced by cobalt sulphide, which is far less expensive, more efficient, more stable and more readily available.

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