What is biomass CHP?
Biomass CHP (Combined Heat and Power) is the term used to describe the process of producing both electricity and heat, at the same time, using Biomass i.e. plant and animal matter, food waste or more commonly, wood in the form of wood chips or pellets, as the fuel source.
The co-production of electricity and heat is extremely fuel efficient compared with more conventional technologies and dependant upon the type of technology employed, can be more than twice as efficient as producing electricity alone.
The use of Biomass, rather than natural gas; the most commonly used fuel type in conventional CHP, translates the energy generated from merely sustainable to being Renewable energy.
What are the benefits of biomass CHP?
There are clear benefits to the use of Biomass CHP, derived from it’s efficiency coupled with it’s low carbon impact as a Renewable energy source, which make it an increasingly an “in demand” technology.
Biomass is considered a significant tool in the battle against carbon emissions. Wood fuel, in particular, is a carbon neutral resource and can make a significant contribution to meeting the UK's commitment to reducing CO2 emissions. Operators of biomass CHP schemes therefore enjoy significant environmental and financial benefits.
In addition CHP delivers value energy as it recovers heat that would otherwise be wasted. This represents substantial energy savings especially when combined with other energy efficiency measures.
Biomass CHP delivers an environmentally friendly and operationally efficient solution that works on environmental, operational and financial levels. The extent to which the UK government is supporting biomass CHP technologies ensures that projects should achieve attractive payback performance.
There are two established processes for delivering biomass CHP in small - medium size applications in the 200KWe – 2.5MWe range: the Organic Rankine Cycle (ORC) and Gasification technology .
The suitability of either process depends on the individual circumstances of the potential project and would be established during the design phase.
The Organic Rankine Cycle (ORC) is based on the ordinary Rankine cycle, with the difference that instead of water an organic medium is vaporized. Since this organic medium has a lower boiling point than water, the ORC has the advantage of using heat sources with substantially lower temperature than in the case of a steam cycle.
The ORC process runs at atmospheric pressure and requires minimal operator intervention. ORC is an established technology and there are many installation examples in mainland Europe.
The main elements of an ORC solution are the biomass boiler for initial firing and provision of heat for the thermal oil boiler. The thermal oil is used as a transfer medium and runs through a heat exchanger. The organic working medium in the ORC module is evaporated and then expanded in an asynchronous turbine which runs at low speed generating electricity.
Downstream the organic medium is cooled in a regenerator and then condensed in the heat condenser, producing hot water at 80-90c for use within the heating system.
Gasification is a process involving partial combustion of a portion of the biomass fuel in the reactor with air, pure oxygen, oxygen enriched with air or by reaction with steam.
It is a thermal upgrading process in which the majority of carbon in the solid fuel is converted into gaseous form (syngas) leaving an inert residue (char or ash) which is removed. The energy content of the fuel is therefore transferred into the gas phase as chemical energy.
The output from the gasification process is used as fuel to power a traditional engine which in turn provides the heat and power requirement. These engines are not subject to particular modification for the gasification process. As such the fuel derived from the gasification process needs to be of good enough quality for these standard engines.
There are several types of gasifier:
Fixed bed gasifiers are generally most suitable for installations in the 200KWe to 10MWe range. Fixed bed gasifiers are further grouped as downdraft (200KWe – 1MWe), updraft gasifiers (1MWe – 10MWe).
Fluidized bed gasifiers are more suitable for larger installation up to 100MWe in power requirement. Fluidized bed gasifiers are further grouped as bubbling bed, circulating bed, entrained bed and twin reactor.
The Right Application?
The different technology options need careful consideration. Systems need to be precisely specified based on the ratio and extent of heat and power requirements. The energy within the biomass fuel being used also needs to be taken into account along with fuel storage and delivery capacity.
For a project to be successful, all these considerations need to be addressed. Vital Energi is able to provide the necessary level of expertise and knowledge in these technologies to make sure that the solution to you requirement is properly designed and delivered from start to finish.
How relevant is Biomass CHP?
The various government subsidies available to this kind of new technology means that biomass CHP is a viable solution to energy requirements. Vital Energi is currently working with leading exponents of biomass CHP solutions in mainland Europe as interest in this technology continues to grow in the UK
Email a member of our expert Vital Energi team with your community energy query and they will get back to you as soon as possible.