Heating of the development by biomass was an integral part of planning application for this project, however, unfortunately, early advice on fuel storage and loading options was not sought.

Whilst the current system works, relying on chips being blown into the fuel store slows down the delivery and limits options for supply to only those with the correct specialist equipment. Had Dunster been involved earlier in the project, changes could have been made to the design to facilitate chip supply without any significant change to the capital costs. Despite that, the system operates effectively and offers substantial savings on conventional fuels.

Fuel Supply and Chip Handling

Dunster designed and implemented the conversion of an existing outbuilding to house the boiler and accumulator tank and sourced the second-hand grain silo and potato handler for the chip store and loading system. These were adapted to allow deliveries using a standard tipping trailer and have been a great success. There is no requirement for any chip handling by St Audrie’s staff or equipment.

System Design and Installation

The system was designed as a baseload boiler to provide 90%+ of heat and hot water with a combination of oil and gas boilers to deal with peak loads. In the event, the 3,000-litre primary thermal store and 2,000-litre satellite thermal store have sufficient reserve that the backup boilers have not yet been required.


In addition to the major financial benefit of becoming independent of oil and gas prices, the installation has further enhanced St Audrie’s environmental credentials.


February 2011


Supply of heating and hot water to block of 37 flats in a town centre location.

Boiler and Plant

130kw ETA Hack woodchip boiler with 3000-litre accumulator tank installed in a newly built block of flats in an urban location.


The boiler is expected to use about 100 tonnes of G30/50 woodchip per annum, producing around 350,000Kwh of heat. Seasoned woodchip fuel is bought in from local suppliers.

Chip Storage

A 40m3 fuel store was built as part of the plant room and this is loaded by blowing chip from the delivery vehicle through an xxx inch pipe. Woodchip is transferred direct from this store to the boiler by an auger and rotary arm agitator. Refilling of the chip store occurs approximately every 2 weeks. Dunster only became involved in this project after the design of the chip store had been finalised and, although it works, better solutions could have been found if specialist advice had been taken earlier in the design phase.

Grant / Funding

The system received a 40% grant under the Bio-Energy Capital Grants Scheme. It is expected to transfer to the upcoming RHI scheme.

Savings / Investment

As this system was installed as part of the building process, capital costs were kept relatively low. The savings compared with providing the heat with oil result in a return on investment of XX% even before any RHI payments have been factored in.

CO2 Saving

Estimated at 110 tonnes per annum

Our 90kw ETA Hack wood chip boiler suffered water damage in late 2014. Dunster Biomass Heating was the only company that could fix the issues without costing me new components. What we have learned is simple. Experience is key! When there is an unusual problem you need more than a guy with a manual – you need a company with the expertise, ability and willingness to solve the problem!

Nick Hiscox, Director, GSF Livestock Equipment