Case study

Walhampton School

200kW woodchip boiler with 5,000 litre accumulator tank

Key facts


November 2013


Heating and hot water for the school campus

Boiler and plant

200kW woodchip boiler with 5,000 litre accumulator tank and 5m diameter agitator / auger fuel feed. The plant room and fuel store was housed in a purpose built container solution. The system is supported by 200kW of back-up and peak load gas boilers.


The boiler is expected to use around 120 tonnes of woodchip
to produce over 432Mwh of heat per annum.

Chip storage

A purpose built 5m2 fuel store was erected on a new concrete slab beside the boiler house, designed to take both blown and manual deliveries from a tractor and front loader.

Grant / Funding

The project was self-funded and is fully accredited on the
non-domestic RHI scheme.

Savings / Investments

Income from the RHI and fuel cost savings has resulted in a
return on investment exceeding 22%.

Walhampton is an independent day and boarding school for boys and girls aged 2-13 situated on the southern edge of the New Forest. Dunster was originally engaged to study how biomass could improve efficiency and generate cost savings.

The existing system was a combination of a 400kW oil boiler for heating and a 230kW mains gas boiler for hot water. Using a non-invasive ‘Dynasonic’ metering system Dunster established the existing boiler outputs and the pattern of heat loads. This enabled Dunster to design a new biomass installation that could fully integrate with the existing system and act as a base load undertaking the majority of the school’s heating and hot water requirements.

The plant room was sited 110m from the main school building in order to keep deliveries and heavy machinery away from areas used by the children. In order to avoid disruption and to respect the sensitivities of working in a regulated educational establishment, on-site working was kept to a minimum by building the plant room and fuel store off-site in a specially designed containerised solution.

Once completed the containers were craned into position onto pre-installed concrete pads and connected to the Rehau Rauthermex district heating pipe transferring heat from the plant room to the main school building. The majority of the work was undertaken during the school holidays, with only minor works undertaken during term time.

Fuel supply and chip handling

The fuel store was designed to take blown woodchip deliveries as well as manual loading from a tractor or tele-handler with a front loader. This gave the school both the option of deliveries from a wood fuel supplier but also the facility to utilise their own wood if this was stored and then chipped on site.

System design and installation

Dunster undertook all aspects of the project as a turnkey solution. Dunster designed and built the bespoke plant room and fuel store for the 200kW woodchip system and installed the district heating main. Having undertaken an evaluation and study of the existing systems and heat loads, Dunster designed a new control system and interface to ensure the minimum usage of fossil fuels. Dunster installed a 200kW gas boiler to ensure that peak load heat requirements were met and to provide an additional level of back-up.


In addition to an attractive return on investment of over 22%, the school is now benefiting from new controls, heat transfer pumps and valves. The system now delivers all of the schools heat and hot water whilst halving their energy bills.

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