Case Studies

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The data logging systems offer key data trends showing how well the boilers are performing. Some examples of these are shown below, and the Case Studies also highlight issues, trends, and remedial actions.

Film showing delivery of wood chip fuel and some of the issues at a French Pilot Project Site

Optiwood case studies


Case study 1 – Public Sector Offices and Records Storage Facility

A 300kW Herz wood chip boiler, linked to a 5000 litre buffer tank. It has a modular back-up gas boiler system. The wood fuel is supplied via an underground silo.

The biomass system has had a number of issues including serious water ingress into the fuel silo, faults with heat meter failure, BMS problems and valve failures. The boiler is over-sized for the actual heat load due to not developing the whole site as initially planned.


Case study 2 – Community District Heating

A 200kW HDG boiler system heats 35 buildings in a 1.2km long community district heating (DH) design. It is linked to twin 5,000 litre accumulator tanks. There is no fossil fuel back-up. The boiler replaced an older 300kW biomass system in order to attract high RHI tariff income levels but it is under-sized for the heat load and some buildings are under-heated in winter.

Significant inefficiencies exist in boiler the boiler room hydraulic set-up and the heat losses throughout the underground pipework system.

Case study 3 – Large NHS Hospital

A 990kW Schmid underfed hearth boiler, de-rated from 1200kW to allow it to access the RHI tariff system. Has a 10,000 litre buffer tank and supported by three hook bin fuel silos. Designed to contribute 25% of the hospital’s heat load, (remainder supplied by natural gas). The boiler requires frequent manual cleaning due basic design and is shut down every weekend to manually clean the combustion hearth, plus every month the heat exchangers.

After a troubled operating history until late 2017 when a new servicing regime was agreed, the boiler efficiency and availability has steadily improved.

Case study 4 – Plant greenhouse and Retail company

Heated by a single 900kW Heizomat chip boiler with 10,000 litre buffer tank. Uses 30- 45% moisture content wood chip fuel. No fossil fuel back-up boiler.

The boiler system has a very basic set-up with limited controls. The design heat load has fallen considerably since the boiler was commissioned with a peak load now 40% of the boiler capacity. The buffer tank is exposed to weather and with indoor insulation only.

Case study 5 – Academy secondary school

This is a 450kW Gilles wood chip boiler system fuelled via twin hook bins. It was installed in 2010 and was accredited under the RHI in 2013. It has no buffer tank but heats a school / community swimming pool plus school buildings. There are also 3 x 140kW gas boilers.

After an initial period where the boiler ran poorly and there were a number of breakdowns, a committed new Operator and Manager significantly improved the efficiency levels of the boiler system and increased its availability.