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Chevening House, Kent495kW Woodchip / Gas District Heating System

Scheme Supply of hot water and heating to Chevening House, Estate Office and two cottages

Boiler and plant A 195kW ETA Hack woodchip boiler teamed with 300kW of mains gas boilers, a 5,000 litre accumulator tank, a 5m agitator and auger fuel feed system. Properties are connected by a 375m district heating network.

Fuel The boiler is expected to use approximately 115 tonnes of G50 wood chip per year to produce around 350MWh of heat.

Chip storage 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.

Grant / Funding The system was funded by the Estate, and is awaiting RHI accreditation.

Savings / Investment The Estate is expected to achieve fuel cost savings and a RHI income of around £40k per annum. The payback on the investment is forecast to be between 6 and 7 years.

CO2 saving Estimated at 111 tonnes per annum

Commissioned April 2013

APPROVED INSTALLER

MCS CER

TIFI

CATION BODYM

ARK

APPROVED

Project overviewChevening 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 a purpose 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

Timber from forestry operations on the 3,000 acre es-tate 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 installationAlthough 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 base load heat.

BenefitsIn addition to dramatically reducing the cost of heating, the project will encourage and support 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.

Dunster Biomass Heating Limited Higher Ford, Ford, Wiveliscombe. Taunton TA4 2RL

01984 624 811

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