Biomass ORC and CHP

Organic Rankine Cycle (ORC)

There are four main of types of CHP boiler. These are:

  • Natural/LPG Gas CHP (as seen above)
  • Biomass gasification CHP
  • Steam Heliex
  • Organic Rankine Cycle

A gasification type is renewable and , in simple terms, cooks wood to release wood gas, which is then captured and fed into an internal combustion engine (modified petrol engine like you find in a car) which drives a generator. The cooling water of the engine and exhaust provides the heat you need, and the generator the power. The drawbacks are that they are temperamental, very fussy about the fuel quality and moisture content and the gas they produce is very dirty when compared with other sources of gas. This leads to the engine needing a lot of attention, such as filters changed every few days, engine oil change every week or so, and an engine overhaul once a year, not to mention engine replacement every four years or so. Imagine running your car engine night and day at 6,000 rpm for 8,000 hours straight for 333 days of the year. Does that sound like it would be trouble free?

Steam heliex relies on a steam generating boiler. It’s a much more reliable and relatively trouble free process compared to the gasification CHP. The drawbacks are the steam biomass boiler is very expensive, with a complex control system, and creating steam with biomass is relatively inefficient when compared to running a low temperature hot water boiler. It’s also potentially far more dangerous if anything goes wrong.

Organic Rankine Cycle (ORC) uses a fairly standard biomass boiler to heat a thermal oil, and is therefore cheaper than steam generating. It uses a similar process to a refrigeration cycle, causing the thermal oil to boil and turn into a gas to drive a turbine, which creates power, then when the gas cools it turns back into a liquid again to be re-heated. Once the process has used the heat it needs to generate power, the water then is circulated around your heating system and back to the boiler.

An Enogia Organic Rankine Cycle setup
An Enogia Organic Rankine Cycle setup

We choose to install ORC because:

  • Lower capital cost makes payback quicker
  • Low maintenance requirement makes for cheaper running costs
  • Fewer moving parts and lower pressures in the biomass system makes for good reliability

Our ORC manufacturing partner is Enogia in combination with the Gilles industrial boiler range, which can run on very low grade fuel to give you the lowest running costs, combined with the best returns.

Gilles HPKI-R cut through
Gilles HPKI-R cut through
How it all goes together
How it all goes together

Quick return on investment due to Renewable Heat Incentive payments on the biomass heat produced, as well as another RHI payment on CHP (Combined Heat and Power)

Biomass only Biomass with ORC  
 RHI RHI CHP with 40°C waterRHI CHP with 45°C waterRHI CHP with 50°C water
Eligible thermal power [kWth]1000100010001000
Running hours6500650065006500
ORC net efficiency0.0%5.7%5.2%4.7%
Relative efficiency (compared to 20%)0.0%28.5%26.0%23.5%
Tier 1 Incomes (3.05 p/kWh)£93,513£66,862£69,200£71,537
Tier 2 Incomes (2.14p/kWh)£110,980£79,351£82,125£84,900
CHP efficiency incomes (4.42p/kWh)£0£81,881£74,698£67,516
Total Incomes RHI CHP£204,493£228,093£226,023£223,953

These are annual payments, which will be paid for twenty years: £228,093 x 20 = £4,561,860 and that’s not all. Because you are generating your own electricity, you get to keep it at a cost of around 6p per Kilowatt, saving on average 8p per Kilowatt on what your electricity currently costs you to buy from the grid. You also get hot water to heat a building or a swimming pool, or an industrial process. Why would you not do it?

For further information, please contact Commercial Biomass Ltd on 01935 476927