495kW Woodchip / Gas District Heating System
Chevening House, originally owned by the Stanhope family was gifted to the nation by the 7th Earl in 1967. It is now run as a Trust and is the official country residence of the Foreign Secretary and Deputy Prime Minister.
The ever-rising cost of oil combined with the need to replace inefficient and ageing boilers drove the Trustee’s decision to invest in a biomass heating system. The boiler and associated plant were installed in apurpose-built energy centre housing the plant room, fuel hopper and bulk woodchip storage area. Dunster worked with the estate to design a system and building that minimised the impact on the listed buildings whilst ensuring maximum flexibility in fuel supply.
Fuel Supply and Chip Handling
Timber from forestry operations on the 3,000-acre estate is expected to produce more than enough timber for fuel demand. Timber is stacked outside the new energy centre and chipped periodically into the bulk storage area. Wood chip is then transferred as required to the adjacent hopper by tractor and loader, on a weekly or bi-weekly basis.
System Design and Installation
Although the original tender was for a 500kW wood chip system, Dunster suggested that a hybrid system would offer significantly lower investment costs whilst still ensuring that over 75% of heat use was provided by biomass. This business case was further supported by the significantly lower cost of mains gas compared to the old oil-fuelled boilers. It is anticipated that the use of gas boilers will be reduced further by staggering peak load requirements and maintaining the house at a more constant temperature with baseload heat.
In addition to dramatically reducing the cost of heating, the project will encourage and support the management of the 530 acres of estate woodland. It will also enable the historic fabric of the house and contents to be maintained at a more constant and beneficial temperature.
Supply of hot water and heating to Chevening house, Estate Office and two cottages (Chevening House)
A 195kW ETA Hack woodchip boiler teamed with 300kW of mains gas boilers, a 5,000-litre accumulator tank and a 5m diameter agitator and auger fuel feed system. Properties are connected by a 375m district heating network.
The boiler is expected to use approximately 115 tonnes of G50 wood chip per year to produce around 350 mWh of heat.
A purpose-built energy centre was built to house the plant room, fuel hopper and bulk chip storage. Estate timber is stored by the energy centre and chipped directly into the bulk storage bays.
The system was funded by the Estate Trust and is awaiting RHI accreditation.
The Estate is expected to achieve fuel cost savings and an RHI income of around £40k per annum. The payback on the investment is forecast to be between 6 and 7 years.
Estimated at 111 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!