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2008
26 November 2008
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Hot spot
Waste heat from a power station in east London could soon be warming local homes and schools. And it could be the start of a wider energy network in the region, writes
Lee Hibbert
The unglamorous environment of Barking power station on the banks of the Thames in east London is set to be home to a district heating project that could transform the nature of decentralised energy distribution.
Plans are afoot to recover heat from the production of electricity at the combined-cycle gas power station and use it to warm local homes. The station currently discharges 400MW of surplus heat to the Thames. The £100 million project – the first of its kind in the UK based on gas turbine power plant – will require the construction of more than 20km of underground hot-water pipes in a loop from the station, out to domestic, public sector and business users across the region, and back again. Its proponent, the London Development Agency (LDA), reckons it has the potential to save over 100,000 tonnes of carbon dioxide a year, significantly contributing to the Mayor of London’s target of cutting carbon emissions by 60% by 2025.
“This is a major piece of infrastructure which will bring some excellent benefits,” says Peter North, head of decentralised energy delivery at the LDA. “First and foremost, it is about carbon saving. Using heat from Barking power station enables us to deliver carbon savings at the lowest possible cost – way cheaper than we could using, say, solar photovoltaics or wind turbines. It’s also a technically low-risk project that can be easily scaled-up and extended to other areas, as and when the need arises.”
The project started as far back as 2005, when the London Borough of Barking and Dagenham investigated the potential of capturing the heat from the power station to use in its local housing stock. A study by consultancy Parsons Brinckerhoff suggested that there was potential to put heat from the power station to use.
On joining the LDA, North was keen to push the project forward with a plan to upgrade the existing plant and build a heat transmission network – a flow and return pipeline running east and west from the power station, to supply space heating and domestic hot-water requirements. The first customers could be supplied during 2011. “The Parsons Brinckerhoff report originally confirmed that such a scheme was practical, viable and broadly economic,” says North. “We then embarked on a more detailed feasibility study and that proved that to be the case. It became clear that this scheme had the potential to deliver a big prize in terms of carbon saving. We think it’s a real opportunity – it looks extremely attractive, both from a feasibility and economics point of view.”
The scheme is designed to provide heat in the form of hot water through a pipeline network from the power station to a range of buildings. The most suitable end uses would be in newbuild housing developments and public-sector organisations such as schools, which would be expected to sign contracts lasting for around 25 years.
Existing households are also an important customer group but difficulties supplying individual homes mean that this would not take place until some time after the first phase of the network is built. The scheme would provide all space heating and hot-water requirements to those connected, eliminating the need for end users to have their own gas boilers.
A total of 23km of trenched pipeline will be laid out from the power station. Installation will see the pipeline buried and backfilled using a so-called pre-compensated method that will minimise the need for expansion joints and bellows.
There are effectively two pipes: a flow and return, similar to a standard central heating system.
“The maximum design temperature would be around 115°C, but we would operate this on a variable temperature/variable flow rate regime, as is the practice on European district heating systems,” says North. “Our controlling parameter is the return temperature, where we would try and achieve around 50°C. As the ambient temperature changes throughout the year, the system will alter the flow rate/temperature to minimise the pumping and heat losses.”
One of the main benefits of the project would be its scalability. In its early stages, the pipe network would travel from the power station to conurbations around Barking town centre and Barking riverside. Once established, new housing developments and other heat customers further afield could be plugged into the main spine of the pipeline at nodes. Over time, says North, a fully-integrated “heat network” would evolve, linking other heat suppliers with new and existing heat users in the region.
“We have already held initial discussions with Tate and Lyle, who are installing biomass boilers at their facility near the Thames to complement their current CHP plant. There is the potential to take an energy supply from them and plug it into our system.
“Then there’s the Olympic park in Stratford which will also have CHP plants going in: why shouldn’t we have a capability to connect to them and take or deliver heat? There’s also a big interest in doing something around the area of advanced conversion technology/energy-from-waste from within the London Thames Gateway.”
The project, then, is far more than the mere construction of a water pipe network retrofitted to an existing power station. North says it is about promoting the trading of affordable low-carbon heat across the whole of the London Thames Gateway region. “Potentially the system could be expanded ad infinitum,” he says. “We would just require additional pipes, booster pumping stations and possibly some strategically placed hot-water boilers which can boost the temperature on the coldest winter days. That’s our long-term thinking.”
Other cities, primarily Sheffield and Nottingham, already have experience of district heating systems from energy-from-waste plants. But the Barking project will be the first in which a large-scale system will be retrofitted to an existing combined-cycle gas-fired power station.
That presents certain technical issues at the interface between the new system and the power station. “We have some very interesting issues around the power station,” says North. “That power station won’t necessarily operate 24 hours a day; it would operate according to the electricity market. So it might operate on a two-shift system over a 24-hour period.
“We are considering putting heat accumulators in so that we can capture all the heat available, even though the demand might not be there, and use these accumulators as a buffer store so that when the power station shuts down we can continue that heat supply. That’s a technical issue where we are trying to match the power plant availability with the heat demand.
“The control system at Barking power station is probably at least 13 years old, so modifying that will also represent an engineering challenge.”
The project is now moving forward with the appointment of a financial adviser to produce a business plan, investment model and delivery vehicle. This could involve the formation of a consortium known as a special purpose vehicle which might oversee development, construction and operation of the district heating system.
A lot of the economic assumptions that underpinned the project were made at a time when there were many housing developments planned for Barking town centre and other locations. The credit crunch means those developments might get cancelled or postponed. But North says that, with secure public funding channelled through the LDA, the project is still sound and has long-term viability. The project will start supplying its first heat to customers during 2011.
He says: “We are concentrating on getting the spine in place and then we can begin to consider how it can grow organically into other areas. If we can get it under way based on a limited customer base then we can grow it as the opportunities arise. We’ve already got a fairly good idea where the heat demands are, so we will be looking to build it in sections.
“The main challenge this brings is to ensure that we have consistent design standards and engineering parameters around the issues of temperatures, pressures and flow rates as we begin to build the different sections out. Then the scheme will evolve and interconnect as commercial opportunities permit.”
Looking to the future, North says that the heat recovery project at Barking power station is more than just an engineering challenge: it is being seen as a test-bed for a new energy policy. Decentralised power production is seen as a popular way forward because it reduces the costs and losses of distributing electricity over large distances and utilises the heat normally wasted in the generation of electricity to the benefit of the environment. Locally generated power – and recovered heat to supply substantial heat loads – works extremely well in densely populated urban areas such as London where demand is at its greatest.
“This is a pilot for other area-wide decentralised systems,” says North. “A lot of other regional development agencies are already looking with great interest at what is going on in London.
“There’s no reason why it couldn’t be easily replicated over the country as long as the right energy densities and energy sources are in place.”
© PE Publishing, 26 November 2008
