Find out everything you need to know about small scale CHP, including how it works, who uses it and the benefits that it brings.
What is Combined Heat and Power?
Combined Heat and Power - also known as cogeneration - is the simultaneous generation of usable heat and power in a single process. Power is usually in the form of electricity which, when generated on site, allows the capture of the resulting waste heat for local site use.
There are four simple stages to CHP:
1. Electricity generation
2. Electricity distribution to site
3. Heat recovery
4. Heat distribution to site
Heat from Combined Heat and Power can also be used to generate cooling by using an absorption chiller unit. This process is known as trigeneration.
How does small scale CHP work?
An engine, usually fuelled by mains gas, is coupled to an alternator to produce electricity. Heat that would usually be wasted is recovered from this process through the exhaust, water jacket and oil cooling circuits. This heat is then distributed to the site to meet local heating requirements instead of burning gas in a boiler.
Small scale CHP is an integrated package which contains the main component parts including:
- The gas engine
- The alternator
- The heat recovery system
- The base frame and enclosure
- The control, protection and monitoring system
Choosing a fuel depends on availability, storage and flexibility of supply. Small scale CHP tends to run on natural gas, though propane, butane, LPG, biodiesel or biogas are all options.
CHP maximises fuel efficiency and converts it into electricity at around 38% efficiency and heat at around 50%.
What are the benefits of small scale CHP?
Reduced running costs
Combined Heat and Power reduces the site’s actual energy cost. Organisations using CHP can save between 15 and 40% on their electricity costs over power sourced from the grid and heat generated by on-site boilers.
Reduced CO2 emissions
A good CHP scheme is able to deliver an increase in efficiency of up to 25% compared to the systems it replaces, and can provide aminimum of 10% carbon dioxide savings.
Security of supply
Cogeneration can act as a back-up generator and also provide a back-up heat source, reducing dependency on the main supply.
How to calculate CO2 savings:
Mains electricity displaced + boiler heat displaced – CHP fuel input = Net CO2 saving
Who uses small scale CHP?
Typical CHP users include:
- Leisure centres
- Commercial premises
- District heating schemes
- Industrial manufacturers
Cogeneration should be considered when:
- Designing a new building.
- Installing new boiler plant.
- Replacing or refurbishing an existing plant.
- Reviewing the electricity supply.
- Reviewing standby electricity generation.
- Considering energy efficiency in general.
- Exploring options towards building regulation compliance.
- Reducing CO2 emissions and environmental impact.
- Small scale CHP is a cost effective and energy efficient way to generate usable heat and power in a single process.
- It converts fuel into electricity at around 38% efficiency and heat at around 50%.
- Cogeneration can provide a minimum of 10% CO2 savings, as well as improve security of supply by acting as a back up generator.
- CHP should be considered when designing a new building, refurbishing a boiler plant, reviewing an electricity supply or considering energy efficiency in general.