Stirling District Heat Network

May 6

The Stirling District Heat Network is the first, large-scale, sewage heat recovery system to be based within a wastewater treatment plant in Scotland. It has been developed in response to the drive to decarbonise heat and provides a demonstrator for other projects. A range of Scottish based suppliers have demonstrated their capabilities, putting them in an excellent position to benefit from future low carbon heat projects. The projected growth of low carbon heat projects in Scotland, and beyond, makes this an attractive market for other suppliers looking for new opportunities.

Benefits for residents and businesses

The Stirling District Heat Network is a pioneering low-carbon energy project developed by Stirling Council and Scottish Water Horizons (part of Scottish Water). It uses a heat pump system to recover waste heat from the local wastewater sewage system and delivers this low-carbon heat to various users through a new district heat network. A number of Scottish suppliers were involved at various stages of the project’s development and it continues to provide economic benefits through ongoing operation and maintenance services.

The benefits of the new system are:

— Generates income from a wastewater treatment plant owned by Scottish Water
— Reduces waste and emissions from the wastewater treatment process
— Provides affordable and low-carbon energy to residents and businesses
— Reduces carbon emissions from Stirling Council owned buildings.

Putting plans into action

The project received vital funding support from the Scottish Government’s Low Carbon Infrastructure Transition Programme (£2M towards a total project budget of £6M). The project will also receive the Non-Domestic Renewable Heat Incentive for 20 years.

This financial support, combined with leadership from both Stirling Council and Scottish Water Horizons, enabled the project to proceed and provides a valuable innovative example of renewable and low carbon technologies in action.

This is the first large scale example in Scotland of using heat generating equipment within a wastewater treatment works, following a smaller scale heat recovery scheme from a sewage pipeline at Borders College.

By showcasing the approach in Stirling, the aim is to act as an inspiration for other potential similar projects around Scotland and beyond. The network is now fully operational and is successfully utilising heat pumps to extract thermal energy from wastewater.

What does the network look like?

The network made up of two key facilities:

An energy centre owned by Scottish Water Horizons and operated at its local wastewater treatment plant. It includes the networks’ low-carbon and renewable technologies.

A district heating network owned and operated by Stirling Council that supplies heat in the local area through an underground pipe network. It delivers low-carbon heat and financial savings to organisations including a local leisure centre and a secondary school. There is scope for the network to be expanded to include local businesses and homes, with the potential to help address fuel poverty experienced by some local residents.

Low Carbon Heat Technologies Used

Water Source Heat Pumps
These capture low temperature heat energy from the wastewater system and concentrate this energy to a higher temperature. Compared with traditional heating sources, the heat pumps reduce carbon emissions since the majority of generated heat is sourced from the wastewater without any direct greenhouse gases being released.

Anaerobic Digestion
The use of biological processes to convert the wastewater sewage into a biogas and a solid material which can be used to create compost.. The biogas is used as a replacement for natural gas and reduces carbon emissions.

Gas-fired Combined Heat & Power
A natural gas-fired internal combustion engine provides electricity (via a generator) and heat energy.

Benefits to Scottish low carbon heat and renewables companies

The design and development of the network involved several low-carbon and renewable companies in Scotland, with the ground-breaking nature of the project enhancing their expertise and reputation. Stirling-based FES Support Services Ltd led the technical design and installation of both the energy centre and the district heating network. Successful delivery of this innovative project has undoubtedly expanded their capabilities, as well as those of their Scottish partners. The main Scottish based companies that contributed to the success of the project were:

During the development and construction of the network the community also benefited in a number of ways, including work experience, training and apprenticeships. This included local staff employed during the installation of the district heat pipework by Doncaster based contractor, Isoplus. The new local skills developed were a valuable result for the project.

Throughout the lifetime of the network, the system will be operated and maintained by specialist contractors, providing continuing work, continually developing local skills in this growing sector.

Benefits expected

Carbon emission savings
— A predicted saving of 381 tonnes of CO2e annually. This represents a 20% reduction in emissions and is equivalent to:

- Taking over 200 average petrol cars off the road
- 2,805 aircraft flights from Glasgow to London

For Users
— A 10% reduction in heating costs to users connected to the network, as defined in heat supply agreement.
— Increased energy security and reduced costs for users, as they will no longer require on-site heating equipment.

For Stakeholders
— Greater energy efficiency and cost savings for users.
— Local community regeneration and economic development.
— Local job creation and upskilling.
— Long term income generation for Stirling Council.
— Improved air quality.

The project is being supported by the Scottish Government’s Low Carbon Infrastructure Transition Programme.
This case study has been developed with support from: