Reheat boosts an off-grid, remote community’s sustainable way of life with multi-technology, renewable heat solutions and a UK-first three-input district heat system.
- 120kW Biomass system feasibility, design and installation
- Immersion heater installation, integrated with Eigg Electric, to operate using the Island's surplus renewable electricity
- Solar thermal array installation to enhance sustainability during summer months
- UK-first trivalent district heat system is now in place, taking advantage of multiple renewable energy technologies
The Isle of Eigg, one of Scotland’s Inner Hebrides, has earned international acclaim for its bold transition to renewable energy. For decades, islanders relied on diesel generators—expensive, environmentally harmful, and only operational at night. In response, the community established Eigg Electric, a community-owned, off-grid electricity company launched in 2008. Powered by a mix of wind, solar, and hydro, Eigg Electric now provides 24/7 renewable electricity to the entire island.
Tourism has played a vital role in Eigg’s economy, with visitor numbers doubling since 1998. In recent years, the community undertook a major redevelopment of An Laimhrig - a multi-use hub including a shop, café, business space, heritage trust offices, and public wash facilities - to enhance tourism infrastructure while staying true to the island’s sustainable ethos. To achieve this, Reheat was appointed to deliver heat consultancy services, as well as the full design, specification, and installation of an appropriate renewable heating system.
Biomass Boiler Installation
Reheat carried out a full appraisal of fuel options for Eigg’s heating needs, evaluating wood chip vs. log supply based on the island’s accessible conifer plantation. The community opted for logs, a choice driven by local labour availability, lower processing costs, and the desire to avoid importing fuel. Importantly, using logs also avoided a 30% additional capital expense that would have been required for chip-related infrastructure, including a chipper and a large fuel storage shed.
Reheat designed and installed two 60kW biomass log boilers, overcoming logistical challenges such as transporting materials and personnel via the island’s supply vessel, the Spanish John. Today, the system reliably and sustainably heats the An Laimhrig buildings, including the Taigh Nighe wash house, serving campers and day visitors.
Integrating immersion heaters with Eigg Electric
Building on the biomass system, Year 2 of the project saw the installation of two immersion heaters in remote buffer tanks located in the ablutions block and the main community hub. These are directly connected to the Eigg Electric grid and are designed to activate when renewable electricity generation exceeds demand.
By converting surplus wind, solar, or hydro power into hot water, these immersion heaters reduce the reliance on log boilers while ensuring that no renewable electricity goes to waste. This smart integration adds significant efficiency to the island’s energy system and further reduces carbon output.
Solar Thermal Integration
In the third year, the system expanded once more with the installation of a 9m³ solar thermal array, linked to the main plant room buffer tank via ETA’s innovative solar thermal module. This addition is especially effective during the summer months, significantly reducing log fuel usage and enhancing the sustainability of the system.
A UK-First: Trivalent Community District Heating
With the combination of biomass, surplus renewable electricity, and solar thermal, the Isle of Eigg now operates the UK’s only trivalent (three-input) community district heating system. This pioneering solution is a testament to what can be achieved through community-led, low-carbon innovation and reinforces Reheat’s commitment to bespoke, sustainable energy projects in remote and off-grid locations.
