Fre-energy CHP Generator

Fre-energy has developed its own 80 kW biogas engine or CHP (Combined Heat and Power) generator based on a standard ‘off the shelf’ six-cylinder Perkins diesel engine.

Why? We felt the conventional engines were too expensive to both buy and service at sub 250 kW.

For clarity, the difference between a gas engine and an ordinary engine:

  • a gas engine is basically a diesel engine with spark ignition enabling the engine to run on methane or natural gas
  • as a gas engine runs hotter and at a lower compression than a diesel, it also requires a spark
  • engines that run on natural gas are becoming more common, typically as ‘stand-by’ generators

Biogas has some significant differences to natural gas. The methane content of biogas (the part that gives the energy) can typically vary between 45% and 75%, whereas the methane content of natural gas remains approximately 97%. The biogas is rarely clean; even with standard gas scrubbing it still contains varying levels of moisture, hydrogen sulphide and other contaminants which love to eat engines, with the contact areas being the cylinder head, pistons and bearings!

Fre-energy 80 kWh CHP GeneratorSince 2010 , Fre-energy has worked closely with experts on Perkins engines to develop a biogas engine with a significantly modified cylinder head, pistons ignition and mixture control to create a biogas engine CHP generator that is:

  • Durable
  • Inexpensive
  • Easily maintained

Our 80 kWh CHP is ideally sized to suit our smallest digester, which is a 750 cubic metre tank. This tank has been sized to manage the slurry from 150 dairy cows plus 2 tonnes of maize silage, grass silage or chicken muck.

Each 80kWh CHP is built on its own skid unit, which can be moved easily with pallet forks. The CHPs can be bolted to the floor in a shed or supplied in an acoustic container holding between two and four engines. The engine can be configured to run as an export generator or as a standby generator, to provide back-up power during power cuts.

Auxilliary Boiler
This is a high capacity gas boiler that we install in our 80kW Container Unit as a standby unit to heat the digester and burn off any excess gas if the CHP is not running

Multiple engines give the advantage of:

  • Improved generator output - service or repair downtime is reduced
  • Entire ‘Plug and Play’ unit can be replaced within a couple of hours
  • Improved generation flexibility enables more flexibility in generation capacity
  • Each engine can be purchased on asset finance
  • Three engines sit nicely below 250kWh at the higher FiT of 14.7p. Feed-In Tariffs (FITS) - Department of Energy and Climate Change
  • 80 kWh is not too big a jump to increase income if a better feedstock is sourced to produce more gas..

Parts and Maintenance

Fre-energy hold stocks of all the parts for our CHP, including an entire ‘Plug and Play’ service exchange unit for loan during a breakdown or scheduled rebuild.

The Fre-energy Operations and Maintenance Cover Plan offers a range of options, from remote monitoring of the Integrated Control System through to comprehensive cover, which includes parts, labour and 24-hour call out, providing peace of mind and ensuring optimum output to maximize return on investment.

Further Information

Fre-energy AD Management System

Acoustic Container for housing the CHP Generator and Management System

What is the difference between a gas engine and an ordinary engine? (FAQs page)


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