Renewable heat and power cuts sawmill power bill

Plant room at sawmill with 2x CHP systems

Aims: Combined Heat and Power system to provide renewable heat for a woodchip drying floor and substantially reduce electrical power costs onsite

Location: Aberdeenshire

Customer: Rosehill Timber, Sawmill


The aim of the project was to deliver an efficient, renewable heat solution for the drying of woodchip, as well as providing sustainable power to either offset current electrical loads or export excess power to the grid. This system provides 90kWe and 200kWth of heat and power using woodchip from the sawmill as the fuel source.

Description of Project

Spares racking and pump layout within plant room

The sawmill has an instantaneous peak power use of 260kWe with an average usage of around 44kWe over the year. Our analysis of the half hourly data found that the power followed a trend of high demand between 08:00 and 17:00 during the week but little or no consumption outside of these hours due the to machinery not being in use. Using this information, we concluded that the CHP units would provide a 90kWe offset during the periods of high demand but would be able to export excess power out with these hours.

Most customers that install a biomass system would need to have a secure source of fuel which would need purchased and delivered on a regular basis – however, the sawmill had woodchip as a by-product of their work. By using the heat produced from the CHP systems to install a drying floor, the sawmill has been able to dry their own waste woodchip for selling directly to their own customers.


  • The CHP systems are fuelled with sustainable, waste woodchip produced onsite.
  • The installation of the drying floor enables the generation of up to 2,555 tonnes of woodchip per year.
    Drying floor installed drying waste woodchip
  • The drying floor will dry enough woodchip per year so that excess woodchip can be dried and sold to customers with their own biomass installations.
  • Utilising the Renewable Heat Incentive (RHI) scheme enabled the project to be financed, with full return on investment in less than 7 years.
  • Capital allowances can also offset capital costs.
    Biosus installed an Energy Management System (EMS) allowing the client to monitor power use and cost savings on a minute-by-minute basis.
  • The CHP system guarantees 56,000kWh per month – offsetting typical use of 32,000kWh.