OHLEH - Challenges and Solutions
The Western Isles’ location in the North West of Scotland means that, while some challenges are project-specific, many of the challenges faced, such as weak electrical grid and costs associated with logistics (both economical and environmental) are common to remote locations across the world.
- Weak Grid: The Western Isles electricity grid is weak and therefore limited in the level of new renewable energy that it can support. The wind turbine at Creed is rated at 300kW but, due to grid limitations, the turbine grid export is constrained to 225kW.
- Underutilised Resources: The fish waste produced by Scottish Salmon Company (SSC) currently gets sent to landfill or transported off-island. Meanwhile, Creed does not have sufficient intake of organic waste to fully utilise its anaerobic digester, hence there is insufficient biogas available to allow the Combined Heat and Power (CHP) system to meet the site heat and power demand, resulting in use of carbon intensive oil heating systems and imported electricity.
- Oxygen Price: Sufficient oxygen levels need to be maintained in the water in the hatcheries at all times and failure to supply oxygen to the fry, parr and smolts will result in mortalities and is therefore not an option for SSC. Bottled oxygen is used as a back-up and must be available at all times on-site to cover any failure of the static equipment. Extra transport costs means that bottled oxygen is relatively more expensive for the Western Isles, and cannot be delivered in bulk due to the challenges of transportation to the islands.
- Supply of energy: The remote location of the hatchery often results in failures of the electrical network. Similarly to oxygen, energy is fundamental to aquaculture and back-ups need to be in place. Often back-ups are ageing diesel generators, with associated higher CO2 emissions and delivery costs due to remoteness.
The aim of OHLEH is to overcome the above challenges and to demonstrate a circular energy economy that will have relevance and learning for other projects. The local energy economy philosophy lying behind the project is thought to be suitable for other locations in a similar context and therefore the potential for replicability of elements of the project is high.
The following project activities will complete the local energy economy:
- Diversion from Landfill: Diverting fish waste to the Anaerobic Digester (AD) system will provide a significant number of additional CHP operation hours, increasing the CHP capacity factor. This represents potentially important economical and environmental savings for Comhairle nan Eilean Siar (CnES), as well as for SSC. Integration of fish waste into the AD along with domestic waste is believed to be a first, and appropriate equipment has been installed to allow this integration.
- Hydrogen Production: Compressed hydrogen will be produced using the existing hydrogen system at the Creed site, for power and transport end-use applications for both CnES and SSC.
- Hydrogen Fuel Cell: A hydrogen fuel cell will be installed at one of SSC’s hatchery sites (Barvas), utilising hydrogen produced at Creed for power application at a lower cost than importing from the grid. If proved to be a viable option, hydrogen energy could potentially supplant diesel generation for critical power supply applications.
- Hydrogen Refuse Collection Vehicle: An adapted bin lorry that runs on hydrogen and diesel will be used to collect waste from across Lewis and Harris, some of which will be used to produce biogas via anaerobic digestion. The truck will be refilled with compressed hydrogen at Creed, using the existing 350bar refilling station.
- Oxygen Production: Retrofitting of the existing hydrogen electrolyser with oxygen-capture equipment will help to utilise otherwise-constrained power from the wind turbine and CHP, and will allow production of oxygen at a lower cost than the open market price.
The project will be an innovative, environmentally and financially sustainable demonstration of how various renewable energy technologies can be integrated to support the policy objectives of local energy economies and circular supply chains.