Tuesday, 27 April 2010

Research on Wooden Tidal Energy Turbine Blades

Oslo, Norway [RenewableEnergyWorld.com]
The Harstad-based company Hydra Tidal will install a full-scale (1.5-MW) prototype of its tidal energy plant at Gims√łystraumen, a marine channel in Nordland County. The Morild floating power plant will be moored to the seabed and mostly submerged, with turbine wings spanning a diameter of 23 metres. However, its most unique feature is that its turbine blades are made of laminated pine.
Wood has not been used in modern turbine blade designs for decades. But company founder and R&D director Svein D. Henriksen extols the virtues of wood for such applications.
“Wood is a porous, homogenous material — so it has better mechanical and hydrological characteristics than today’s conventional materials such as composites and steel. The major challenge is the actual assembly process, but we believe we have found a good solution.” He points out that using wood in turbine blades is also an environmentally sound choice, especially in a lifecycle perspective.
Assembly, installation and maintenance are simpler for a floating facility than for one permanently anchored to the seabed. The Morild power plant can be assembled on land and then towed to its operating location for installation. It can also be detached and floated to the surface for repair.
Two Projects with Research Council Funding
Hydra Tidal is receiving funding for two different projects under the Research Council of Norway’s RENERGI programme. One project is studying Morild’s wood components at the Norwegian University of Science and Technology (NTNU) laboratories in Trondheim and will verify the company’s findings. The other project involves testing the effects of extreme environmental conditions on the entire Morild construction. The primary objective is to examine, test and analyse how such conditions affect a floating facility for converting the energy of slow coastal currents, tidal streams and ocean currents.
The projects will culminate in a full-scale test in the water in June 2010. The costs of developing the concept have totalled roughly NOK 125 million over the last 10 years, funded primarily by a large number of industrial participants and investors.
International Potential, Job Creation
In the channel where Morild is to be placed at the end of June, the maximum current is 3.5 knots, with tidal periods of six hours, 20 minutes. The plant will start out generating a modest 1 GWh annually, but the testing phase is intended to focus on verifying the technology rather than on production levels.
“After testing, we will move the plant to Moskenesstraumen (a channel with tidal streams up to six knots), where its output will be stepped up considerably,” explains Mr Henriksen, who also has great ambitions for Morild internationally. “There are powerful ocean currents along many of the world’s coastlines, and foreign players have shown considerable interest in this project. At the moment we have patent applications being processed in about 20 countries.”
“Our objective is to develop this technology in close collaboration with Norwegian industry players in order to create jobs in Norway. This can be done, provided that there are conducive framework conditions for commercialising successful technologies.”
Although he is a proponent of establishing better commercialisation schemes in Norway, Mr Henriksen believes that funding for development should remain highly competitive. “That’s the only way to ensure that the winning technologies really are the best ones in the long run.”
Atle Abelsen/Else Lie are writers at The Research Council of Norway. This article was translated from Norwegian by Darren McKellep and Victoria Coleman

Underwriters Laboratories Announces Personnel Certification Program for Solar Photovoltaic System Installers

UL University will train and certify system installers to meet growing demand for clean-energy technologies
NORTHBROOK, Ill., April 26 /PRNewswire/ -- Underwriters Laboratories (UL), a global leader in safety testing and certification, announced today the introduction of a new program to train and certify installers of photovoltaic (PV) products and systems. The program, available beginning July 2010 through UL University (ULU), represents the first of many the organization will provide for practitioners across a wide range of industries and professions.
The PV System Installer certification program was created to meet and exceed existing industry requirements through a working cooperation with leading PV industry stakeholders, NGOs and professional associations. The new offering from ULU, geared towards licensed electricians, aims to satisfy a need to improve the safety and performance of PV systems through a more qualified workforce. With solar power expected to generate 10 percent of the world's total electricity by 2035(1), the safety of installed systems will become even more important.
"ULU will offer hands-on training that will be closely aligned with the knowledge and skills required for practitioners to perform safely and effectively," said Patrick Boyle, President of ULU. "By increasing the number of qualified installers, UL is augmenting its 116-year-old commitment to public safety and helping the PV industry position itself to keep up with burgeoning demand and safely provide clean-energy solutions to the public."
Worldwide in 2009, PV installations reached a record high 7.3 gigawatt (GW), representing growth of 20 percent over the previous year.(2) To help sustain this growth, industry personnel can be trained to meet a comprehensive standard that outlines proper guidelines for everything from PV systems installation to the safe manufacture of the product itself. ULU's new PV installer program will increase the competence of personnel across the board and allow UL to engage its safety arm starting with equipment and extend it through to the actual installation, performance and safety of the end-user.
"The UL University program will streamline and standardize the education installers need to ensure the solar industry can fulfill its role as one of the primary energy sources of the future," said Bill Brooks, Professional Engineer of Brooks Solar and expert in the consulting and training needs of the PV industry. "Training these individuals to comply with an industry standard will provide the human capital needed to continue building upon the rapid and upward progress being made in the field."
In mid-summer 2010, ULU will unveil a new, full-service facility to support its venture into personnel certification. Located at UL's RTP laboratories in Raleigh, NC, the campus will offer training and personnel certification programs in categories like general laboratory technology, PV testing, food safety, National Electric Code, electric vehicles and fire safety.
For more information on UL University and the PV System Installer certification program, visit http://www.uluniversity.us/certification.
(1) 2008 Photovoltaic Industry Analysis and Forecast
(2) Solarbuzz's "MarketBuzz 2010" energy market research report
About Underwriters Laboratories
Underwriters Laboratories (UL) is an independent product safety certification organization that has been testing products and writing Standards for Safety for over a century. UL evaluates more than 19,000 types of products, components, materials and systems annually with 20 billion UL Marks appearing on 66,000 manufacturers products each year. UL's worldwide family of companies and network of service providers includes 68 laboratory, testing and certification facilities serving customers in 102 countries. UL is also the only National Certification Body (NCB) for PV in North America and an OSHA-accredited Nationally Recognized Testing Laboratory (NRTL). For more information, visit www.UL.com/newsroom.
SOURCE Underwriters Laboratories

Global UN report highlights booming low-carbon economy

Study says policy environment has improved in many countries since Copenhagen, putting low-carbon economy on track to exceed $2tr mark by 2020
James Murray, BusinessGreen, 23 Apr 2010

The global low-carbon economy has shown encouraging signs of growth since the turn of the year, despite the failure of the Copenhagen Summit to deliver a binding international climate change treaty.
That is the conclusion of a comprehensive new report undertaken by the United Nations Environment Programme (UNEP) and think-tank AccountAbility, which revealed that the policy environment and market conditions for many low-carbon firms are improving rapidly.
The study, which was released late last week at the Business for Environment Global Summit (B4E) in South Korea, analysed national climate change action plans and the scale of economic growth for low-carbon products and services in 95 countries responsible for 97 per cent of global economic activity and 96 per cent of global carbon emissions.
The resulting Climate Competitiveness Index (CCI) found that 46 per cent of countries had delivered improvements in their climate policy framework since the end of the Copenhagen Summit last year. Moreover, 32 countries were judged as having delivered "significant improvements" in their action plans, with Germany, China and the Republic of Korea praised as outstanding examples.
The report argued that this improvement in policy was driving a substantial growth in the low-carbon economy, which it estimates will now be worth over $2trn a year by 2020.
"This report comes as a breath of fresh air," said Alex MacGillivray, managing director at AccountAbility, in a statement. "The CCI shows that countries at all levels of development can develop political leadership, stronger institutions and engage with stakeholders to deliver climate competitiveness. Climate competitiveness is no longer rhetoric. It is a real, massive and dynamic economic frontier."
The report confirmed that a number of low-carbon hubs are quickly emerging, which are well positioned to dominate the fast-expanding global market for green goods and services.
In particular, it praised Sweden, Denmark, Germany, Japan and France for showing the "most consistent progress" in terms of both climate policy and low-carbon markets. Meanwhile, the US and UK were singled out for delivering strong climate policies, while the emerging BASIC nations (Brazil, South Africa, India and China) were also praised for "progressing towards climate competitiveness".

Camelina Biofuel Powers US Navy F/A-18 Test Flight

Montana, United States [RenewableEnergyWorld.com]
Sustainable Oils supplied the camelina-based biojet fuel that powered a test flight of the U.S. Navy's F/A-18 "Green Hornet" aircraft last week on Earth Day. Taking place at the Naval Air Warfare Center in Patuxent River, Maryland, the flight was the first to demonstrate the performance of a 50-50 blend of camelina-based biojet fuel and traditional petroleum-based jet fuel at supersonic speeds.
Sustainable Oils also provided the camelina-based jet fuel that powered the historic flight of a U.S. Air Force A-10C Thunderbolt II on March 25, 2010.
According to the U.S. Navy, the Green Hornet performed as engineers expected, successfully completing all aspects of the test flight. The fuel was produced by Honeywell’s UOP using its renewable jet fuel process technology and the flight won the praise of Secretary of the Navy Ray Mabus, who has provided ongoing leadership in the Navy’s focus on renewable energy and attended the test flight.
"The alternative fuels test program is a significant milestone in the certification and ultimate operational use of biofuels by the Navy and Marine Corps," Secretary of the Navy Mabus said. “It's important to emphasize, especially on Earth Day, the Navy's commitment to reducing dependence on foreign oil as well as safeguarding our environment. Our Navy, alongside industry, the other services and federal agency partners, will continue to be an early adopter of alternative energy sources."
In September 2009, Sustainable Oils was awarded a contract by the Defense Energy Support Center to supply camelina-based jet fuel to the U.S. Navy. The contract was for 100,000 gallons of HRJ-8 beginning 2009 through 2010, and includes an option to purchase an additional 100,000 gallons between June 2010 and December 2012. The camelina for the contract, including the Green Hornet test flight, was primarily grown in 2009 and harvested in September 2009 by farmers in Montana. The company also has several field trials in Washington State.
“The success of the Navy’s Earth Day flight again demonstrates that camelina-based jet fuel meets the quality and performance requirements that these aircraft demand,” said Tom Todaro, CEO of Sustainable Oils. “We look forward to continuing to work with the U.S. military, as well as commercial airlines, to provide the next generation of domestically-produced aviation biofuels that create revenue and jobs in rural areas, decrease greenhouse gas emissions, and reduce our nation’s dependence on foreign energy sources.”
Sustainable Oils also provided the camelina-based jet fuel that powered the historic flight of a U.S. Air Force A-10C Thunderbolt II on March 25, 2010, which flew from Florida’s Eglin Air Force Base on a 50-50 blend of camelina-based jet fuel and traditional jet fuel. The 90-minute flight marked the first time that any aircraft has been powered by conventional and biomass-based fuel in all engines.
Camelina was selected for initial testing by the military because it does not compete with food crops, has been proven to reduce carbon emissions by more than 80 percent, and has already been successfully tested in a Japan Airlines commercial test flight in January, 2009. In addition, camelina has naturally high oil content, and requires less fertilizer and herbicides. A life cycle analysis (LCA) of jet fuel created from camelina conducted at Michigan Tech University in conjunction with UOP LLC, a Honeywell Company, and Sustainable Oils found that the renewable fuel reduces carbon emissions by 80 percent compared to petroleum jet fuel.

Political rivals argue over who has greenest credentials of them all

Tom Baldwin and Ben Webster
Labour and the Tories clashed over their green credentials yesterday as David Cameron was accused of failing to confront climate-change deniers inside his party.
The Conservative leader made his pitch for eco-voters when he announced plans for a new generation of neighbourhood parks on derelict land. But he immediately came under attack from Labour, which pointed out that a number of Tory candidates were openly sceptical about man-made global warming.
Despite Mr Cameron’s slogan of “vote blue go green”, a recent survey found that only 22 per cent of Conservative candidates in winnable seats strongly supported Britain’s target of generating 15 per cent of Britain’s energy from renewable sources by 2020.
David Davis, the former Shadow Home Secretary, recently warned that the policy of tough targets to cut carbon emissions, supported by Mr Cameron, was “destined to collapse”.

At a Climate Question forum in London yesterday, Ed Miliband, the Energy Secretary, repeatedly clashed with his Conservative, Liberal Democrat and Green counterparts.
He said that the Tories had been “just found wanting” in dealing with climate-change deniers and that local authorities controlled by the party had too often opposed onshore wind farms. But Greg Clark, the Shadow Energy Secretary, said: “Maybe it’s a symptom of being in Whitehall too long, but Ed must recognise that there are different opinions in the country. I disagree strongly with deniers, but the way is to convince them of the case.”
Challenged over the views of Marcus Wood, the Conservative candidate in Torbay who has expressed scepticism about climate change, Mr Clark said: “I have never heard of him.”
Labelling people who oppose wind farms as antisocial is counter-productive, added Mr Clark. “This kind of lecturing from Westminster and officials in Whitehall doesn’t work.”
He detailed Conservative plans for dealing with the “climate emergency”, which include a “green deal” for every home to improve energy efficiency and a nationwide introduction of “smart meters” by 2016 — four years earlier than Labour proposals.
Labour’s opponents dismissed the Government’s “feeble” record on renewable energy and improving air quality after 13 years in power.
Simon Hughes, the Liberal Democrat climate-change spokesman, said that it was too late for Mr Miliband to claim that Labour cared about the environment. “Ed talks a good talk, but renewables targets are not met, fuel poverty not met, air quality targets not met,” he said. “The Government hasn’t delivered.”
Mr Miliband responded that Lib Dem opposition to nuclear power left a “massive hole” in their climate change strategy, which he contrasted with Labour’s willingness to take “tough decisions” on meeting carbon emission targets.
But Mr Hughes reiterated his view that nuclear power was too expensive and would undermine investment in renewable energy.
He said that his party had a clear commitment to a zero-carbon Britain and would create a green economy with 100,000 jobs, and £10,000 for each household to cut emissions.
“This is a fantastic opportunity, and this is the reality of this election, that for the first time in my lifetime there could be in government a party which has a commitment at every level to the green agenda,” he said.
Darren Johnson, of the Green Party, which hopes to win its first seats in this election, warned that a “massive transformation” of the economy was needed, and said thast the scale of the challenge was huge because of decades of “dithering and inaction”.

Cuts jeopardise solar utility IPO

A green utility company with plans to float on the London stock market is suffering delays due to economic problems in the eurozone

Terry Macalister
The Observer, Sunday 25 April 2010

A plan to set up an innovative "green" utility with a £1bn flotation on the London stock market risks being blown off course due to financial problems in the eurozone.
Engyco, led by former United Utilities boss John Roberts, has admitted that expected cutbacks to subsidies on renewable power projects in Spain would threaten its plan for an initial public offering (IPO). The company was formed as a vehicle for investing in the Spanish solar market with the hope of creating a pure renewables utility that could raise billions in the bond market.
An Engyco spokesman said €3bn of potential investment was at stake if Madrid introduced plans to reduce solar subsidies, which he believed would only save ministers €420m.
"This kind of move would be very damaging for investment in Spain. We need to get clarity about exactly what is going on but we are still confident that it will blow over as similar threats like this have done in the past," said an Engyco spokesman.
City analysts specialising in the clean-technology sector believe there is little chance of Engyco being launched in the next couple of weeks as scheduled given the negative noises coming out of Madrid. "This is nothing less than a catastrophe" for investors, said Stephane Aderca, an energy analyst at Liberum Capital in London. "We had believed that a promise [to pay a certain level of subsidy] is a promise. Going back on a promise brings the whole thing into question."
Spain's government has sucked in an estimated €18bn in solar-power projects since 2008 by offering generous public subsidies but is now looking at cutting back as the economy suffers.
The state has the authority to cut prices paid to operating renewable power plants under a 2007 law, according to an industry ministry spokesman who declined to be identified. All options are being assessed for a new strategic plan this year, he told local media, in comments that led some Spanish solar and wind developer shares to fall over 4% at the end of last week.

Amtrak trials first cow-powered train

Biodiesel made from beef byproducts fuels rail operator's first green train, cutting carbon emissions and improving air quality.
Danny Bradbury for BusinessGreen, part of the Guardian Environment Network
guardian.co.uk, Monday 26 April 2010 12.38 BST
US rail operator Amtrak may have given the term "cattle car" a whole new meaning with the first test of a biodiesel train that runs on beef byproducts.
Operating on a $274,000 (£178,000) grant from the Federal Railroad Administration, the state-owned rail company has begun operating its daily Heartland Flyer train, travelling between Oklahoma City and Forth Worth, using B20 biodiesel fuel.
The fuel, which mixes 80 per cent diesel with 20 per cent biofuel, cuts both hydrocarbon and carbon monoxide emissions by 10 per cent, according to the company, which said that the fuel also reduces particulates by 15 per cent and sulphates by 20 per cent compared to standard diesel fuels.
The biodiesel, which was refined from beef byproducts provided by a Texas supplier, will run as a 12-month experiment, during which Amtrak will collect data on emissions, and on the impact of the fuel on mechanical parts.
Although technically the fuel mix can run in unmodified trains, the locomotive was fitted with new engine assemblies so that detailed measurements could be taken to establish the effect of the fuel on the engine.
The impact of biofuel blends on engines can vary dramatically, with some biofuels leading to increased wear and tear, while others tend to burn cleaner and lead to improved engine performance and durability.
Amtrak is now promoting the biodiesel train to passengers with a 50 per cent discount on a companion fare until 28 May.
The biodiesel trial is the latest in a series of environmental initiatives from Amtrak designed to highlight the operator's position as a green alternative to domestic US flights.
The company has switched from low-sulphur fuel to ultra-low sulphur fuel across the railroad to tackle air pollution, and has installed recycling receptacles in its trains and stations. It has also stepped up efforts to reduc e idling times for its diesel trains, and has introduced regenerative braking systems similar to those in hybrid cars such as the Toyota Prius for its electric trains.
In addition, the company is a member of the Chicago Climate Exchange and has a public commitment to reduce emissions by seven per cent in 2011 and 2012.

UK Coal puts merger plans on hold

UK Coal's merger talks with Hargreaves Services postponed after £129m loss for 2009 and debts exceeding its value
Tim Webb
guardian.co.uk, Monday 26 April 2010 20.56 BST
UK Coal has put merger talks with Hargreaves Services on hold after announcing a huge increase in losses for the year as a result of geological problems at its deep mines, lower property and coal prices.
The company said it had sold £8.6m of farm land to reduce its debts and was looking at more land sales to bolster its flagging balance sheet. New standby borrowing facilities of £30m have also been arranged to see it over the next few months.
Chief executive Jon Lloyd and finance director David Brocksom also saw their salaries frozen and bonuses cut because of the losses, and after two workers died in accidents last year.
It was not clear tonight when, or if, meaningful discussions would take place between UK Coal and resources and energy support services group Hargreaves Services. UK Coal announced last month that it had received a tentative merger approach from Hargreaves. But the company has not handed over detailed financial information requested by Hargreaves to allow it to begin due diligence.
UK Coal is interested in a tie-up, partly to reduce its reliance on its deep mines, which are very expensive to maintain and are unpredictable to run because of unforeseen geological problems like those experienced last year.
UK Coal endured a torrid 2009 in almost every respect. It posted pre-tax losses of £129.1m, up from £15.6m the previous year. Coal production was down by over a tenth, mainly because of collapsing shafts at its deep mines. Because of the recession, demand from coal plants, UK Coal's main customers, fell, as did coal prices. It also had to slash the value of its property division, made up of land reclaimed from former mines, by £25.7m.
The company admitted: "The financial results for 2009 are not those we planned for." It also said that its debts at the end of March stood at £236m, in excess of tonight's market value of the company of £177m.
UK Coal hopes production at its deep mines will increase significantly this year after opening new seams, and that coal and property prices will rise as the economy recovers. It will also open three new surface mines this year, which are cheaper to operate but are unpopular with local residents and planners. UK Coal is Britain's largest producer of coal. It said the UK burned around 43m tonnes of steam coal in 2009, mainly to generate electricity.
Consumption fell by 17% compared to 2008, as electricity demand was hit by the economic downturn, improved performance at nuclear stations and low gas prices. While the firm did see a lull in short-term demand, it said long-term the appetite for coal would be unaffected by the electricity market as UK production can only meet a fraction of requirements and the country is a "substantial importer of coal".
"Demand will continue substantially to exceed our supply capacity throughout this decade," the firm said.

US research paper questions viability of carbon capture and storage

Document from Houston University claims governments overestimated CCS value

Terry Macalister
guardian.co.uk, Sunday 25 April 2010 17.26 BST
A new research paper from American academics is threatening to blow a hole in growing political support for carbon capture and storage as a weapon in the fight against global warming.
The document from Houston University claims that governments wanting to use CCS have overestimated its value and says it would take a reservoir the size of a small US state to hold the CO2 produced by one power station.
Previous modelling has hugely underestimated the space needed to store CO2 because it was based on the "totally erroneous" premise that the pressure feeding the carbon into the rock structures would be constant, argues Michael Economides, professor of chemical engineering at Houston, and his co-author Christene Ehlig-Economides, professor of energy engineering at Texas A&M University
"It is like putting a bicycle pump up against a wall. It would be hard to inject CO2 into a closed system without eventually producing so much pressure that it fractured the rock and allowed the carbon to migrate to other zones and possibly escape to the surface," Economides said.
The paper concludes that CCS "is not a practical means to provide any substantive reduction in CO2 emissions, although it has been repeatedly presented as such by others."
The report has come at a critical time when British and other governments worldwide have started to fast-track a series of CCS prototype schemes as a way of removing carbon from the atmosphere and helping with climate change.
On 8 April, Royal assent was given on to what is now the Energy Act 2010, which made law plans to raise a levy on power users to establish four CCS projects in Britain. Ministers see this as a potentially planet-friendly way of building new coal fired power stations, such as the one E.ON wants to construct at Kingsnorth, in Kent.
The Carbon Capture and Storage Association (CCSA), which lobbies on behalf of the sector, says Britain is now at the forefront of new technology with a legislative framework in place that offers the opportunity for long-term investment.
Projects are proceeding in the US, such as the experimental coal-fired Mountaineer plant in New Haven, West Virginia, which began small-scale carbon capture last year, as well as in Canada, China and other countries.
Jeff Chapman, chief executive of the CCSA, believes Economides has made inappropriate assumptions about the science and geology. He believes the conclusions in the paper are wrong and says his views are backed up by rebuttals from the Lawrence Berkeley National Laboratory, the Pacific Northwest National laboratory and the American Petroleum Institute.
The British Geological Survey confirmed it was looking at the Economides findings and was hoping to shortly produce a peer-reviewed analysis.
Economides, who has a PHD from Stanford University, said he had seen the arguments against his paper from the API and dismissed them as "nonsense" saying vested interests are protecting a new concept foisted on the world by geologists without proper thought.
"I was a [practising] petroleum engineer for many years and soon realised that geologists did not understand flow and the laws of physics, against which you can't argue."
Chapman pointed out that Statoil, a Norwegian oil company, had been injecting CO2 into an old reservoir on the North Sea Sleipner field for some time as a successful experiment in carbon storage. But Economides says the Sleipner scheme involved a million tonnes over three years, while one 500mW commercial station would need to absorb and store 3m tonnes annually for 25 years.Economides, who admits he veers towards being something of a climate change sceptic, says the oil and coal industries see these schemes as potential solutions so they can keep on doing what they have been doing in the past, but "CCS is the last refuge of the scoundrel," he said.

Giant gravel batteries could make renewable energy more reliable

Wind and solar power are often criticised for being too intermittent, but Cambridge researchers could change that

Alok Jha
guardian.co.uk, Monday 26 April 2010 12.33 BST
Newly designed giant gravel batteries could be the solution to the on-off nature of wind turbines and solar panels. By storing energy when the wind stops blowing or the sun stops shining, it is hoped the new technology will boost to renewable energy and blunt a persistent criticism of the technology - that the power from it is intermittent.
Electricity cannot be stored easily, but a new technique may hold the answer, so that energy from renewables doesn't switch off when nature stops playing ball. A team of engineers from Cambridge think they have a potential solution: a giant battery that can store energy using gravel.
"If you bolt this to a wind farm, you could store the intermittent and relatively erratic energy and give it back in a reliable and controlled manner," says Jonathan Howe, founder of Isentropic and previously an engineer at the Civil Aviation Authority.
The Labour government committed to cutting the country's carbon emissions by 34% by 2020 and 80% by 2050, both relative to 1990 levels. To achieve this, ministers outlined plans to build thousands of wind turbines by 2020. The only economically viable way of storing large amounts of energy is through pumped hydro – where excess electricity is used to pump water up a hill. The water is held back by a dam until the energy is needed, when it is released down the hill, turning turbines and generating electricity on the way.
Isentopic claims its gravel-based battery would be able to store equivalent amounts of energy but use less space and be cheaper to set up. Its system consists of two silos filled with a pulverised rock such as gravel. Electricity would be used to heat and pressurise argon gas that is then fed into one of the silos. By the time the gas leaves the chamber, it has cooled to ambient temperature but the gravel itself is heated to 500C.
After leaving the silo, the argon is then fed into the second silo, where it expands back to normal atmospheric pressure. This process acts like a giant refrigerator, causing the gas (and rock) temperature inside the second chamber to drop to -160C. The electrical energy generated originally by the wind turbines originally 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.
Isentropic claims a round-trip energy efficiency of up to 80% and, because gravel is cheap, the cost of a system per kilowatt-hour of storage would be between $10 and $55.
Howe says that the energy in the hot silo (which is insulated) can easily be stored for extended periods of time - by his calculations, a silo that stood 50m tall and was 50m in diameter would lose only half of its energy through its walls if left alone for three years.
To demonstrate how much less infrastructure his system requires, Howe uses the example of the Bath County Pumped Storage hydro-electric dam in Virginia, US. This is the biggest energy-storage system in the world, with two reservoirs covering 820 surface acres can store up to 30 GWh storage capacity. An Isentropic gravel battery of the same capacity would occupy 1/300th of the area, according to Howe.
John Loughhead, executive director of the UK Energy Research Centre, said that the novelty of the Isentropic system lay in using cheap materials as the heat store, thus making a normally expensive and mechanically complex process very simple. But he said demonstrators would need to be built to prove the idea actually functions. "The question is, does it work? From an engineering standpoint, the temperature differences they mention, +550C to -150C are initially credibility-stretching for a single-pass cycle, and the potential for gravel particles to pass through the engine and damage or clog the inevitable cooling and lubricating systems seems high."
Howe is in the process of designing a small pilot plant that could store 16MWh at full capacity - enough for the electrical needs of thousands of homes. That energy could be stored in two silos of gravel that are 7 metres tall and 7 metres in diameter. There is no reason why multiple units could not be connected together to store much more power, Howe says several gigawatt hours.
Howe says he is in talks with what he refers to as "a large utility company" to sponsor the construction of a full-storage demonstrator system, something around the 100 kilowatt scale.
Isentropic was selected recently by the government-sponsored Technology Strategy Board for a trade mission to meet Silicon Valley investors, one of around 20 of the Britain's most promising clean technology startup companies.
David Bott, director of innovation programmes at the Technology Strategy Board, one of the sponsors of the 2010 Clean and Cool trade mission said: "Isentropic have done something very exciting, by revisiting scientific theory and coming up with a new technology that answers the need to match the generation of electricity with its use. For instance, the system could enable the more efficient use of wind power, by storing the energy generated by a turbine until it is needed. We need ways to store the energy we generate when we have a surplus, so that it can be used when we need extra and this innovative new system could provide the answer."