As district heating networks proliferate across the UK, community-scale energy production is stoked up and ready to flow, reports Rebecca Poole.
In a matter of months, a dazzling district energy system will come online at the Greenwich Peninsula, UK. Comprising a low-carbon energy centre and Europe’s largest residential new-build district heating system, the structure is set to provide heat and electricity to thousands of new homes and businesses under construction in this up and coming area of London.
Greenwich Peninsula is just one of hundreds of district heating networks springing up in cities and towns across the UK. Right now only around two per cent of UK domestic heat demand is served by a heat network but the UK government reckons this meagre figure could swell to a mighty 20 per cent come 2020 and even 40 per cent by 2050.
In recent years, a steady trickle of government funds has re-kindled interest in heat networks in Newcastle, Nottingham and more, as report after report has exposed the ugly extent to which heat is squandered in the UK. Engineering consultancy Buro Happold, for one, estimated London’s wasted heat could meet 70 per cent of the Capital’s heating demand.
Fanning the flames of development, the Department for Energy and Climate Change drew up its National Heat Map, comprising high-resolution web-based maps of heat demand by region. Now, with aspirations to match the community heating successes scored across Europe, the UK government has set aside a hefty £300 million to fund up to 200 heat networks. Decades after its inception, the community heating scheme looks set to make a comeback.
“To bring our carbon targets down we really need to link the nation’s waste heat into district heat networks and the only way to do that is to encourage project development now,” highlights Toby Heysham, director of Pinnacle Power, the company leading the development of the district energy centre and network on the Greenwich Peninsula.
“We’re constantly looking for waste heat sources around London and I see no reason why we can’t use more waste heat to provide heating to people, just as we are in Greenwich,” he adds.
Project development at the Greenwich Peninsula is already well underway. Pinnacle Power has installed kilometres of pre-insulated steel pipework, which currently connects to phase 1, temporary energy centres.
As Heysham, points out: “Right now we provide heat to 750 homes and are connected to 1000 more homes that are under construction.”
Standby for energy
Later this year, the permanent phase 2 energy centre will come online, comprising gas-fired combined heat and power (CHP), standby gas boilers and hot water thermal storage.
With its spectacular Conrad Shawcross-designed 49-mentre high ‘optic cloak’ surrounding the flue, this energy centre is designed to generate some 87 MWth of heat. Given time, it will provide heat to more than 10,000 homes and a hefty 300,000 square metres of commercial space via a long and winding district heating network more than 10-km long.
However, in the meantime, and crucially for the project, the network recently connected to the Greenwich Peninsula Intercontinental Hotel, which according to Heysham demands a massive 4.5 MW in heating, thanks to its 453 rooms across 18 floors, car lift and more.
“This building requires a lot of heating, and securing this commercial connection is gold-dust to us,” says the director. “It allows us to run the combined heat and power plant at a higher baseload, helping us to provide an efficient and cost effective energy supply.”
According to Heysham, the next challenge for the project is to identify a lower-carbon heat source for the energy centre that could replace the gas-fired CHP. Many district heating systems rely on biomass CHP plants, but as Heysham points out, the Greenwich Peninsula is sited next to the Blackwall tunnel; a pair of road tunnels that run beneath the River Thames. “We have a problem with NOx emissions here so until more electric cars are used, we need to reduce reliance on NOx emitting technology,” he says.
His team has also looked at biogas, but concluded this is too expensive at the moment, and while extracting heat from the London Underground tube network is a further option, the network close to Greenwich is not hot enough for this to be viable.
“Extracting heat from the River Thames is another option and we’re looking at how to get this to our network at the right temperature so we can run the system efficiently,” says Heysham. “Choosing the next heat source is very important.”
“The Peninsula is very much a work in progress and will be for the next 25 years,” he adds.
In a similar vein to Greenwich Peninsula, Gateshead town centre will soon be home to a new district energy centre and network, designed to deliver heat and power to the equivalent of 5,000 homes via 3 km of heat network.
Scheduled to come online in the summer of this year, the centralised energy centre is currently under construction and will house two gas engine CHP units, each rated at 2.6 MWth, as well as back-up gas fired top-up boilers. At the same time, the heat network and private wire electrical network are also being installed, as is thermal storage.
“Initially we’re looking to connect 18.9 MWh per annum, which will be predominantly non-residential loads,” says Dominic Bowers, energy solutions director at WSP/Parsons Brinckerhoff, the engineering consultancy leading the Gateshead project. “This [figure] will rise to 31 MWh per annum by 2030.”
In the meantime, more and more businesses and residential buildings are expected to connect to the heat network, and eventually Gateshead Council would like to see other areas of the borough connected to this, and similar, district heating networks.
“We need to bring in a diversity of customers with different types of building with different load profiles,” says Bowers. “This will help to develop a solid demand profile and constant baseload so we can cost effectively install further CHP capacity and bring down operating costs.”
Like Pinnacle Power, future phases of the project will involve looking at alternative sources of heat, including biomass and biomethane. At the same time, WSP/Parsons Brinckerhoff is also working on other district heating projects across the UK, most notably in Bristol and Exeter.
As Bower asserts, a lot more development is needed before district heating is fully established in the UK. “You know, in the 1970s, Denmark was 90 per cent dependent on imported energy and that drove energy policy towards maximising efficiency,” he says. “This is why the nation now has such a large quantity of CHP and district heating networks.”
“We’re moving in the right direction, but we’ve still got a long way to go before [heat networks] become the norm and every town and city has an operational network,” he adds.
Lessons from Sweden
E.ON is a key player in district heating, currently operating more than 300 facilities across Europe, including the Öresundsverket CHP plant in Sweden’s renowned sustainable city Malmö.
This 440 MWe natural gas CHP plant can produce a hefty 3 TWh of electricity for southern Swedish markets and deliver around 1 TWh of heat via its district heating network, to meet 40 per cent of Malmö’s heating needs. The figures are impressive, the technology is more than proven, and now E.ON intends to replicate its Scandinavian experiences in the UK.
“The [Malmö] network was developed in the 1950s, was originally run off coal-fired power stations, then oil, then gas, and now it uses 85 per cent renewable generation,” highlights Jeremy Bungey, head of community energy at E.ON UK. “But this is still the same heat network albeit improved and maintained.”
“So it is very much at the forefront of our minds that we have, in principle, these heat networks at many sites in the UK,” he adds.
Indeed, E.ON currently has 36 district heating projects peppered around the UK. In June 2014, its Blackburn Meadows biomass facility in Sheffield came online, and is now connected to an 8 km district heating network in the city’s Lower Don Valley.
This biomass district heating facility can produce 29 MW of electricity and then capture a further 25 MW of heat, some of which is currently piped to South Yorkshire Police, heavy energy user Sheffield Forgemasters, as well as local sports and leisure facilities.
More major business connections are expected alongside hundreds of residential homes. As Bungey highlights: “It’s a pretty ground-breaking, industrial-size development.”
At the same time, E.ON subsidiary, Citigen, is in the process of extending its district heating network in London. The large-scale CHP-based community energy system has been operating at a central power station near Smithfield Market since 1993, supplying heat to 10 key properties including Guildhall, Smithfield Market and the Barbican Centre.
According to Bungey, ageing diesel CHP engines were recently stripped out and replaced with two 4.3 MW high-efficiency gas-powered generators. The company is now in the process of connecting new customers to the growing heating network.
For Bungey, the South-West of England is also of enormous importance in terms of demonstrating and growing district heating capacity. E.ON currently has several key developments in Exeter, including Cranbrook, Skypark and Monkerton, and as the head of community energy highlights, these are a little different.
“Many of our developments are, say, high-rise blocks in cities, whereas these are lower density developments that will connect houses, schools, community centres; we’re going to connect an entire town to our district heating,” he says.
“However, a lot of people think that district heating just doesn’t work on these lower-density developments, and we’re proving it does,” he adds. “These are ground-breaking projects and people are welcome to come and see what is possible.”
Building a town
Exeter is now home to two ground-breaking, long-term projects; Cranbrook, a largely residential development; and Skypark business park. District heating will provide heat from an energy centre to around 3,000 residential homes and commercial buildings across the two sites.
As Bungey points out, right now, some 1,250 homes at Cranbrook are currently receiving heat through a 35-km long pipe network. “On the Cranbrook development we have homes as well as schools and community centres connected,” he points out. “Although take-up on Skypark has been slower than anticipated, with around three connections.”
Crucially, E.ON’s £3 million energy centre has now been running for around three years, generating electricity and heat for the developments, with surplus electricity fed back into the national grid. Currently relying on a 600 kW gas CHP engine, to meet the baseload energy requirement of Cranbrook and Skypark, as well as additional gas boilers, the company intends to move away from gas-fired CHP once more buildings are connected to the district heating system.
“We aim to use a biomass-fuelled system to meet the baseload over time, probably once we’ve connected around 2,000 units,” says Bungey. “We’ve looked at different technologies to provide that biomass system including pyrolysis and gasification, but we’re not taking on huge technology risks as we have customers that need heat 24 hours a day, every day.”
“This piecemeal approach means we can provide a low-cost, efficient supply from the outset [given] the energy demand profile,” he adds.
Since early last year, E.ON has also been working with the University of Exeter and SK Solar and Star Renewable Energy, on a £1.39 million government-funded project to demonstrate how solar thermal panels and heat pumps can work alongside the existing CHP scheme. Compared to using gas supplied by the National Grid, E.ON predicts that the completed Cranbrook and Skypark district heating network system, running off biomass CHP, will slash carbon emissions by up to 60 per cent and 13,000 tonnes a year, the equivalent of taking 5,000 cars off the road. However, integrating a solar thermal and heat pump scheme could shave off a further 50 to 120 tonnes of carbon dioxide.
Initial modelling from Richard Cochrane, director of education in renewable energy at the University of Exeter, and colleagues, has determined how best to operate a solar thermal array and heat pump with the system. And as a consequence, a hefty 2,000 m² solar thermal panel array is now being constructed next to the energy centre alongside a high temperature heat pump, with twelve-month trials then planned to test the system.
“It will be the UK’s largest solar thermal array... and we will now demonstrate this [set-up] is feasible, practical and can be integrated with an existing district heating system,” says Cochrane.
Testing will take place across different weather patterns and seasons. As Cochrane points out: “You may have a nominal panel efficiency of 80 per cent in the summer, in good levels of solar radiation, but this figure might drop to 30 per cent [in other seasons], with lower levels of radiation and lower air temperatures.”
“At this point, the heat pump can be used to bring efficiency back up again, not all the way to 80 per cent, but somewhere in the middle,” he adds.
Looking to the future, Cochrane is hopeful the scheme could be rolled out with additional district heating facilities.
“As a country we still get a significant proportion of our emissions from our heat demand so I think there is still a lot we need to do to decarbonise our heat,” he says.
“There is scope for similar systems to be rolled out on a range of scales and while the south west has higher levels of solar radiation, it’s viable we could install volumes further north as costs come down.”
Bungey also sees the potential for such alternative heat source schemes. “If successful, this integrated technology could be replicated in existing and new district heating schemes right across the country,” he says. “This and other schemes could make a significant contribution to easing the impact on the environment from domestic heating.”
“The ability of energy centres to adapt to different heat sources is going to be vital to the success and endurance of district heating networks in the future,” he adds.
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