Case Study

District Heating Scheme Brought Back from the Brink by Sustainable Steam

A picturesque royal burgh in Scotland is home to a local district heating scheme. In 2012, a company specialising in the generation of renewable energy from sustainably sourced timber invested £2.5 million into the revitalisation of the scheme. With energy prices in this area being some of the highest in the UK, the specialist company’s proposed introduction of energy-efficient, cost-saving measures proved attractive to residents and businesses alike, with the nearby distillery swiftly joining the scheme.

a new beginning

As part of the drive toward sustainability, in the old energy centre the specialist installed a 3.5MW biomass boiler, feed-tank, turbine and load-levelling vessel, all of which would provide renewable heat and energy for the plant. To identify where further efficiencies could be found, the company specialising in renewable energy generation worked closely with a leading construction and support services provider, who in turn contracted Spirax Sarco to design and specify energy-saving steam technology for the newly-developed plant.

The construction and support services provider has been an advocate of the energy market for decades, helping both public and private sector clients with a range of projects within building services, support services, facilities management, air conditioning and electrical requirements.

They felt strongly that with the distillery joining the district heating scheme, there was real scope to ensure that the new heat and power system could be used to benefit the local community, while making sure the distillery’s ambition of providing its plant with reliable heat, power and steam from renewable sources was fully realised.

Fuel poverty has long been an issue for certain areas of Scotland, with 56 per cent of households in the Highlands alone struggling to pay their energy bills.

“It’s a problem that shouldn’t really exist in the 21st Century, but it does,” says Martin Kent, Project Sales Support Manager at Spirax Sarco. “Areas such as the Highlands, or remote areas like the Orkney Islands, can be hit hard because of a lack of fuel choice, less energy-efficient buildings, and a more extreme climate. This often leads to higher bills than the rest of the UK.”

Martin adds: “This area still has a troubled heat and power infrastructure, with many residents relying on oil-fuelled technologies to keep warm. The investment by renewable energy specialists will serve the community and businesses like the distillery, to make heat and power more affordable.”

A Greener Steam System

The introduction of the biomass boiler to supply the district heating scheme in the burgh has ensured that nearly 200 homes can benefit from a lower-cost and more sustainable heating source.

With the Spirax Sarco project team now contracted by the construction services provider, to design and specify energy-saving steam technology for the newly developed plant, work quickly got underway.

Sarco’s role was to make sure that the new steam system used as much of the available energy as possible to ensure the biomass system would be able to meet both the needs of the community, and those of the nearby distillery.

Having created a full design specification with drawings and an accompanying stress analysis report, the construction and support services company, together with Spirax Sarco, devised a 20-barg steam system that incorporated a second load-levelling vessel with level, steam and condensate control systems, steam surplus pressure reduction systems, double-block and bleed isolation valves, steam ancillaries and a pressure reduction station for the steam turbine.

The plant’s control system reduces the pressure of the steam to 10 barg before supplying the neighbouring distillery, with the rest of the steam then passed through a steam to water heat exchanger that generates hot water for district heating.

With the supplied steam, the distillery is able to use the heat to increase the concentration of ethyl alcohol in the wash, once it has undergone fermentation. Steam provides a more low-carbon, energy-efficient way of heating the fermented wash, because both the latent and sensible heat dissipate into the liquid. Furthermore, the condensate system recycles collected condensate from the process to provide hot water, making it a highly sustainable solution.

The renewable energy specialists’ ambitious investment has certainly paid off, with the burgh now benefitting from the biomass plant’s sustainably-sourced heat and power via its extensive heating network. The construction and support services provider has since also installed a further gasification plant for the distillery, which is expected to generate 1200MWhe and 2000MWhth a year from renewable sources.

“It’s a wonderful feeling to contribute to a project like this district heating scheme, particularly when it benefits the local community in such a way,” says Martin. “Working with key stakeholders, we’ve been able to develop a sustainable, low-carbon heating system for the people of the area and an important part of the town’s heritage. This scheme should certainly keep homes warm and the distillery producing its signature single malts for many years to come. I’ll certainly raise a wee dram to that!”

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