Feature in the CIBSE Journal, August 2018
Heat recovery from wastewater is gaining a significant toehold in Scotland. Plans for a 2MW wastewater heat- recovery scheme in Glasgow have received the green light after a £3.7m funding deal. Sharc Energy Systems will provide heating and cooling at the city’s Clyde Gateway Regeneration project.
Funding was secured in June, when leather manufacturer Andrew Muirhead & Son agreed to become the anchor customer for heat recovered from wastewater. Sharc closed the initial funding, with repayable assistance from the Scottish government’s Low Carbon Infrastructure Transition Programme (LCITP), supported by the 2014-2020 European Regional Development Fund programmes. The LCITP support is matched to commercial loans and investments from the Energy Saving Trust, regeneration agency Clyde Gateway and Sharc International, the Canadian parent company of the UK firm.
Sharc, based in Glasgow and Newark in Nottinghamshire, has a joint venture agreement with Scottish Water Horizons, the wholly owned commercial arm of Scottish Water, enabling it to tap in to the utility’s nearby sewers. The wastewater heat-recovery system at Clyde Gateway works by extracting wastewater from nearby sewers owned by Scottish Water. This passes through Sharc’s energy system in an on-site plantroom, which separates the solids using a series of screens and scrapers, to reduce the particulate content. The water then goes through a heat exchanger and the heat is transferred to the clean side of the system. Recovered heat is amplified via heat pumps to generate the appropriate temperatures for use in all types of buildings (see image on page 38).
Sharc provides heating and cooling to customers through a heat supply agreement with the main advantages including no up-front costs and competive prices capped for the length of the agreement. Additional benefits include reduced carbon emissions and protection against energy shortages because wastewater is an inexhaustible resource. Sharc will build its specialist energy centres on the Clyde Gateway site, manned by staff who monitor and maintain all the units required to serve the site, enabling occupiers to have direct contact with their energy provider. The plan is to grow beyond the 2MW capacity once more tenants sign up.
Sharc’s heat supply agreement includes planned and emergency maintenance, and life-cycle replacement parts. The contract works like that of any energy supplier, says Russ Burton, chief operating officer of Sharc Energy Systems, with the main advantages being no upfront costs and competitive prices capped for the length of the agreement.
Burton claims that using energy from a wastewater heat-recovery system can reduce heating and cooling costs by 15-20% over gas, and can cut carbon emissions by 50%.
Burton says that Sharc can support 70/40 flow return temperatures for district heating by adjusting the heat pump operating arrangement. When replacing gas boilers in buildings, Burton says heat pumps would ideally work on a 10K delta T with 60°C flow. The lower temperatures are a challenge to industry, says Burton, as subcontractors in the UK are more used to working with higher temperatures and conventional gas boilers.
He says his company uses its own internal engineering and project managers to control works delivery, and it prefabricates energy rooms in a factory to maintain the quality of system design. ‘We have developed a package-plantroom approach for the UK and European markets, constructing the equipment on skids in the factory before shipping to site,’ says Burton.
He added that the civil engineering works required to connect the system to the sewer is arranged through the water companies’ approved list of contractors. For its first UK installation in 2014 at Borders College in Galashiels – a Sharc project, supported by Scottish Water Horizons – a standard plate heat exchanger was used, and that is what it employs in the systems built in Canada.
The key lesson from the Borders College project was how the wastewater differed from that in North America. Twice as much water per head of population is used there than the UK, which means there is a higher proportion of solid content of wastewater in Britain’s sewers. To overcome this, additional screening and hydraulic management has been included in the UK installations.
This appears to be an area of growing interest with projects at various stages of development across Scotland, as well as several new enquiries for installations in England, including a district heating scheme for a university in the north of the country.
Ramboll Energy, which assessed the proposals at Clyde Gateway, says that sewer heat recovery should be considered for all district heating projects in urban centres.
Associate director Paul Steen says: ‘For our clients, it offers a commercial proposition that de-risks the challenge of breaking into water infrastructure and provides low carbon heat for individual or district heat supply.’
Aquallibrium Leisure Centre
Sharc’s heat recovery system is also being used at the Aqualibrium leisure centre, in Campbeltown. For this project, Sharc and Scottish Water Horizons formed a joint venture called Bandwith Energy. The £1m scheme will intercept wastewater from Scottish Water’s adjacent Kinloch Park pumping station, before extracting the residual heat and transferring it to the leisure centre’s clean hot-water network.
The new heat-recovery system will replace gas boilers and be integrated into the existing heating infrastructure. It will heat the leisure centre’s 25m swimming pool, fitness suite, steam room, sauna and library, operated by Argyll and Bute Council. The designers claim the system will provide 95% of the leisure centre’s heating needs and reduce energy bills by 25%.
Some minor adjustments were made to the pool’s plantroom, including changes to the heater batteries for the air handling units and replacement of the plate heat exchanger, to accommodate the adjusted flow temperature.
Original Feature is available here