Award-winning innovation in Shetland proves that Scandanavian countries aren’t the only ones ahead of the curve with large-scale district heating systems, and as Anthony Harrington discovers, sustainability will remain key to future provision as new onshore windfarms look set to provide the energy to extend Lerwick’s affordable heat network
WHEN you live on the same latitude as the southern tip of Greenland, a warm home or building is a very desirable thing.
Add in the fact that there is still no grid interconnector linking the Shetland Isles to the Scottish mainland – though one is on the way – and you might think that Shetland has a problem.
Fortunately, Shetland Islands Council (SIC) has long had a solution, one that has put it at the forefront of district heating scheme installations in the UK.
Back in the mid-1990s, the Council needed to find both a sustainable heating solution for its public buildings, and a way of dealing with domestic rubbish, also called solid municipal waste, or MSW.
Since the Scandinavian countries were – and still are – way ahead of the UK in sustainable, district-heating solutions, the SIC opted to study examples from the Nordic countries.
Research pointed towards using the heat from a waste incineration plant to power a district heating scheme. The solution would solve both the Council’s heating and waste problems, at a stroke as it were.
An additional benefit was that it would also provide an efficient waste solution for neighbouring Orkney while saving both councils from having to ship waste to the mainland.
Accordingly, in the late 1990s, the Council commissioned a waste-to-heat (WTH) plant and commissioned Vital Energi to build a district heating system capable of distributing heat from the incineration plant to homes and buildings in Lerwick.
Vital Energi has laid some 40 kilometres of piping so far, connecting over 1,300 homes and buildings to the heating system.
Above, the SHEAP plant in Lerwick heats around 1300 homes and buildings in the town, including schools, leisure centres, care homes and also a hospital
Today the district heating system is run by Shetland Heat and Power Ltd which is owned by the Shetland Charitable Trust, while the SIC owns the Lerwick waste incineration plant, also known as the Lerwick energy recovery plant.
Commenting on the plans for the system, Derek Leask, executive director of Shetland Heat and Power said: “We needed an efficient way of fuelling a district heating system.
“As well as having no connection to the UK gas network, we also have no connection to the electricity grid. All electric power on Shetland comes from the diesel-fired power station at Lerwick, which is not exactly a low-carbon solution. A waste-to-heat plant solved two problems simultaneously. It provides a far superior alternative to sending waste to landfill and at the same time, enables us to provide heat to homes and buildings,” he explains.
Commonly, waste-to-heat plants also generate electricity. However, as Leask notes, these plants are not a particularly efficient way of generating electricity. Opting to have a pure waste-to-heat plant provided a much more efficient solution.
Vital Energi oversaw the whole £6.5 million project, which won the coveted Environment Award for Engineers 2000.
The project has since become a benchmark for these sorts of schemes. The company designed the Peak Load Boiler Station, which includes its own pumping station and standby boilers. It oversaw the construction, testing and bringing online of the facility and put in place the connection between the district heating station and the incinerator.
Leask points out that Shetland Heat and Power currently has around 1050 private houses and social housing units connected to its district heating system, along with around 200 other customers that include schools, a hospital, leisure centres and private businesses.
“We buy the heat from the council and we deliver that heat to our customers. It is very much more carbon-efficient than electric heating, particularly since we are still without a grid connection to the mainland,” he comments.
There is scope to connect more customers, and Leask says that he and his colleagues are currently looking at developing more energy sources.
“There are new housing developments planned for Lerwick and we are hoping to connect into those when they are built. There is quite a lot of new developments planned for Lerwick over the next five years so we have to think in terms of adding to our heat sources. The heat-from-waste plant will not be able to meet all of the demand that could be coming our way in the future,” he notes.
Some of the possibilities here include the company investing in large heat pumps. However, to do this it would need to have its own sustainable energy generation capabilities. Although heat pumps work of heat differentials in either the ground, air or water, they need a modicum of electricity to operate.
Running them off electricity purchased from the national grid would be much too expensive for the scheme’s customers so owning the means of power generation for heat pumps would be required and is being looked in to.
“We have one of the biggest onshore wind farms in Europe being built here in Shetland right now, so that should be a great boost in terms of green energy. That will be connected to the grid in mainland Scotland which could have significant benefits for the Shetland Isles.
“Right now, the heat we generate compares very favourably, in carbon terms, against using electric or oil-based heaters in homes or public buildings. At the same time, particularly at this juncture, when fuel prices and electricity prices are soaring, we also compare very well in price terms.”
Leask points out that this price comparison is critical since Shetland Heat and Power is not just concerned about delivering low carbon heat.
It also has an objective to deliver affordable heat.
“Until we have our own sustainable power generation capability, it is just not viable for us to think about buying the electricity, at current prices, to power heat pumps. We couldn’t generate heat that could be sold at an affordable price,” he comments.
“The Shetland Isles is grappling with one of the worst fuel poverty statistics in the whole of Scotland. We are the only company with a heat network in Shetland providing affordable energy and that is very important to us,” he comments.
There are limits, however, on signing up new customers.
As Leask points out, where there is a new development of 100 or 200 houses, the cost of connecting to the district heating system is very economically feasible for the developer.
However, this is not the case when one considers individual houses. Individual connections are still just too expensive for individual households to sign up.
“People need to realise that hydrocarbons are a diminishing resource globally. Trying to generate heat from hydrocarbons, be it gas, diesel or oil, is not an realistic long-term solution. Without something to replace hydrocarbons as a heat source, we’re going to be in a lot of trouble.
“This is why district heating schemes like ours are so important,” he concludes.