195Kw Woodchip District Heating System
Knowle Manor is a substantial house with 19 en-suite bedrooms and an indoor swimming pool which is available to rent for large groups and corporate events.
Prior to this installation, it was heated by a combination of oil and LPG boilers the cost of which was proving prohibitive. The owners decided to utilise a large, redundant, agricultural building as a chip store and boiler room and to provide heat through a ‘district heating system’ not only to the Manor but also to 2 adjacent cottages. Additional capacity has been retained in order to provide heat for 2 barns which may be converted in the future.
Fuel Supply and Chip Handling
Seasoned waste timber is purchased from a local sawmill and delivered in bulk to the estate where it is chipped by a contractor directly into the bulk chip store. The size and layout of the store mean this operation is only required about every 6 months. A tractor and loader is then used to push chip from the bulk store over an internal wall into the large hopper where it is fed into the boiler by a 6m spring arm agitator. The size of the hopper means that this latter operation is undertaken approximately monthly.
System Design and Installation
The system was designed for 100% of heat and hot water to be provided by Biomass. The heat is transferred from the boiler room to the Manor and adjacent cottages by 260m of pre-insulated district heating main. The 5000l accumulator tank store sufficient heat to allow peak demand to substantially exceed the 195Kw rating of the boiler and also ensures that it operates most efficiently by burning for long periods rather than ‘short cycling’.
Benefits
In addition to dramatically reducing the heating bills for the properties involved, the project has further contributed to the ‘green’ image of Knowle Manor.
December 2010
Supply of hot water and heating to a substantial country house, a swimming pool and 2 associated houses (Knowle Manor Website)
195Kw ETA Hack woodchip boiler installed in a converted outbuilding with a 5000-litre accumulator tank. This is connected to the properties being heated by 260m of pre-insulated district heating main.
The boiler is expected to use approximately 120 tonnes of wood chip per year to produce around 260,000Kwh of heat. A close relationship with a local timber yard allows Knowle to produce chips from bulk purchases of slab wood – the rounded edges of trees remaining when they are cut up into planks etc. Bulk deliveries of slab wood are received about every 6 months and chipped on arrival directly into the bulk store.
A large agricultural building that had become redundant was converted into fuel store, hopper and boiler room. It is sufficiently large to easily contain 6 months’ worth of chips. A tractor is used to push chips over the dividing wall from the store into the hopper which holds 20 tonnes – sufficient for at least a month’s supply. Woodchip is transferred direct from the hopper to the boiler by 6m auger and rotary arm agitator.
The system received a 37% grant from the Bioenergy Capital Grant Scheme but it is intended to repay this in order to qualify for the Renewable Heat Incentive when it opens.
The previous oil and LPG heating systems were generating bills of around £18,000 per year compared to a cost of £6,500 for purchase of timber and processing into woodchip. Without the RHI, but taking into account the capital grants received, the capital costs will be paid back within 6 years. This should be substantially reduced by the RHI.
Estimated at 100 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!
