The Knowle Manor Biomass project 2011

In early 2010 it was decided to install a woodchip district heating system to replace the existing oil and LPG boilers. The criterion was to meet the heating and hot water requirements of the Manor House, swimming pool and 2 cottages plus a barn which may be converted into accommodation in the future.

A 200kw ETA Hack fully automated woodchip boiler has been installed by a local company Dunster Forest Energy Ltd.

The boiler house and chip store were constructed in an existing barn approximately 100m from the Manor House. 260m of pre insulated underground heat main was laid to connect the pool, Manor House and 2 cottages to the new boiler.

Operation

The boiler is fed automatically with chips store via an auger. The chip store has a 6m floor mounted agitator with spring loaded arms and drive clutch which feeds chips into the auger.

The Chip store will hold 20 tonnes, enough fuel for 4-5 weeks in the winter months.

The boiler is supported by a 5000 litre accumulator tank. This facilitates a store of hot water to be generated at times of low heat usage, thus ensuring the system is able to meet peak demands and always operate at maximum efficiency.

Hot water is fed through the underground heat main to individual heat exchangers in each building.

Fuel

Initially the boiler will be fed on bought in woodchips, all locally sourced. The intention is to make our own chips in future, we have a large store of locally sourced, sustainably produced slabwood and round wood drying at present.

Preliminary calculations indicate the boiler will use approxamately 120 tonnes of woodchips per annum.

Carbon saving

By replacing the 5 boilers (4 oil & 1 lpg) we expect to reduce the carbon emissions at the Manor by 100 tonnes/year.

Environmental

When wood is burned it releases CO2 into the atmosphere, this is considered to equal the amount of CO2 absorbed by the tree whilst growing. Thus making woodfuel what is called ‘Carbon Neutral’.

The biomass project at Knowle Manor provides an outlet for low grade timber from local sawmills and forestry operations, hence benefitting the local economy and keeping our fuel miles to an absolute minimum.