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    BBC News

    Sunday 25 September 2005

    Small networks of power generators in "microgrids" could transform the electricity network in the way that the net changed distributed communication.

    That is one of the conclusions of a Southampton University project scoping out the feasibility of microgrids for power generation and distribution.

    Microgrids are small community networks that supply electricity and heat.

    They could make substantial savings, and emissions cuts with no major changes to lifestyles, researchers say.

    Electricity suppliers are aiming to meet the UK government's Renewables Obligation, requiring them to generate 15% of electricity from renewable sources by 2015.

    Microgrids, say the researchers, could easily integrate alternative energy production, such as wind or solar, into the electricity network.

    They could also make substantial savings and cuts to emissions without major changes to lifestyles, according to lead researcher, Dr. Tom Markvart.

    "This would save something like 20 to 30% of our emissions with hardly anyone knowing it," he told the BBC News website.

    "A microgrid is a collection of small generators for a collection of users in close proximity," explained Dr. Markvart, whose research appears in the Royal Academy of Engineering's Ingenia magazine.

    "It supplies heat through the household, but you already have cables in the ground, so it is easy to construct an electricity network. Then you create some sort of control network."

    That network could be made into a smart grid using more sophisticated software and grid computing technologies.

    As an analogy, the microgrids could work like peer-to-peer file-sharing technologies, such as BitTorrents, where demand is split up and shared around the network of "users".

    Microgrids could exist as stand alone power networks within small communities, or be owned and operated by existing power suppliers.

    Campaign groups such as the Green Alliance have been pushing for micropower generation technologies, such as micro-CHP (combined heat and power) boilers - a vital part of microgrids - mini-wind turbines and photovoltaic (PV) solar arrays.

    Micro-CHP units work by turning heat which would normally escape through flues into electricity. Homeowners then sell any surplus electricity back to the national grid.

    The Green Alliance says the government should take micro-generation more seriously.

    Putting just six panels of solar PVs on a typical new three-bedroom house would reduce that household's carbon emissions by over 20%, according to the group.

    Power Pressures

    Microgrids are designed for a smallish community - a typical UK housing estate for example. They deal much more efficiently with fluctuating power demands which the national grid is not flexible enough to cope with.

    Dr. Markvart's project was initiated in recognition that the UK's current electricity distribution system was built around the availability of fossil fuels.

    But the 21st Century throws up some pressing questions about the use of fossil fuels.

    "We wanted to look at what kind of energy system we would ideally construct today, in the 21st Century, in response to current pressures for higher energy use," Dr. Markvart said.

    "We looked at something to which the technology energy sector could evolve in response to the need to reduce emissions."

    Dr. Markvart and his team at Southampton University built a computer model to test out the viability of such small scale networks, combining micro-CHP units with PV solar arrays to convert sunlight into electricity.

    "It is a little bit like comparing the old style telephone network with the network today," said Dr. Markvart.

    Installing a microgrid would not need an entirely new network to be built, as some broadband networks have dictated.

    For developing countries, buildings could provide electricity without the need for vast infrastructures to be put in place.

    Close to Home

    As the cost of alternative technologies falls and their efficiencies rise, they become much more of a viable option.

    Greenhouse gas emissions could also be reduced if micro generators were powered by hydrogen, sunlight or small wind turbines, said Dr. Markvart.

    Having generators close to demand also cuts down the cost of getting power from a remote power station to the household.

    Generator sizes are similar to loads - which is very different to traditional systems with huge power stations serving lots of small users.

    Smaller networks mean ways to store unused power can be introduced, something that does not happen in large networks.

    "In a traditional system, you have the power station and electricity flows from power station to users - it is unidirectional. The whole network is constructed around that unidirectional power flow.

    "There is also a tremendous amount of heat generated during the process. The heat is just waste and it is disposed of," explained Dr. Markvart.

    The huge "chimneys" that have become a familiar part of many areas of the UK are the towers that cool down and then expel the heat waste.

    "Only about 30 to 40% of the primary energy ends up as electricity; 60 to 70% goes up the chimney. You don't have any use for it because there is no one located around the station that needs heat."

    Increasingly, micro-CHP units are being tested out in small communities to potentially replace conventional central-heating boiler units.

    According to estimates, eight million micro-CHP units could be in homes by 2020, supplying a third of a household's power.

    But renewable power groups have called for clearer government policy targets for alternative power strategies.

    "We could have microgrids tomorrow; it can be done now. The technology is there," said Dr. Markvart.

    The main barriers however, are institutional and regulatory. There are some moves afoot by regulators Ofgem, which is working on a registered power zones concept to convince the electricity companies of their potential.

    The cost of renewable energy devices has been recognised by the government, according to the Department of Trade and Industry (DTI). It wants to excite the industry so that the cost of individual units falls.

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