Case study

Wiltshire Estate

130 kW woodchip district heating scheme

Key facts

Commissioned

September 2008

Boiler and Plant

130 kW ETA Hack woodchip boiler installed in a purpose built building with a 5,000 Litre Accumulator tank and 260 metres of district heating main.

Scheme

District Heating Scheme supplying hot water and heating to Manor House, Orangery, Cottage and swimming pool

Fuel

The boiler uses approximately 70 tonnes of woodchip producing over 200,000 kWh of heat per annum.

Chip storage

Chip storage is in a barn adjacent to the boiler room. This is a mixed use barn with approximately 180m3 being used for woodchip storage. The store requires refilling 2-3 times per annum.

Grant / Funding

No grant funding sought.

Savings / Investments

Total cost of the scheme was £73k. The payback of the scheme is expected to be 6.2 years with a ROI of 16%. Generated heat has cost circa. 1.4p per kWh.

CO2 saving

Estimated at 59 tonnes per annum.

The owner sought to install a biomass system on the estate to reduce heating costs and CO2 emmission as well as to move away from a dependence on existing oil fuelled systems.

Fuel supply and chip handling

An existing and undertilised corn store was converted to provide a boiler room and chip storage, some 100 metres from the main house. This avoided the cost of constructing a new building and had good access for fuel deliveries or chipping plant. This also avoided the intrusion of large delivery vehicles at the house. Approximately 50% of the timber chipped is directly from the Estate. This is stacked adjacent to the boiler room where it is left to dry for 12-18 months. The additional 50% of the fuel supply is either bought in as timber from neighbouring estates or purchased in as chip, where it is tipped onto a concrete pad outside the store and pushed in by telehandler. Chipping takes place approximately twice a year with around 180m3 of storage being used.


Loading wood chip store

System design and installation

Of particular importance to the client was to choose a boiler that was very tolerant of out of specification chip, as they were aware of the immature nature of chip supply in the UK at the time. After considering a number of different manufacturers, the client on the advice of Strutt & Co chose an ETA system.

The system was designed and installed by Dunster to provide all the heating and hot water in an 8 bedroom manor house, cottage, swimming pool and orangery. The properties were connected to the boiler room by 260 metres of district heating main. Oil boilers were retained in the individual properties to act as top up in the case of peak loads and as back up. This facility has not been required despite refcent cold winters.

Estate staff installed the district heating mains to Dunster's specifications. Dunster designed and installed all the main plant as well as local interfaces with pumps wirings and controls.

Benefits

The scheme has produced significant savings in line with expectations and has supported the sustainable sourcing of local woodfuel.

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