Micro Combined Heat and Power

Micro combined heat and power (MCHP) is a low carbon option which kills two birds with one stone.

MCHP boilers produce heat just like regular boilers but they also generate electricity for use in the home or to sell back into the Grid!

The principles of combined heat and power (CHP) or 'co-generation' have been used in industrial energy production for decades. Heat produced as a by-product in electricity generation is often captured and used to provide heating and hot water in the local area instead of simply being released into the atmosphere.

MCHP for Your Home

In combined heat and power, heat is the by-product of electricity generation. In 'micro' CHP for the home, the boiler is primarily producing heat for space and water heating but also acts as a dual energy system, generating up to 1kW of electricity per hour at the same time. This is enough to power lighting and appliances in the average home.

As you've probably guessed, electricity is only generated when the boiler is producing heat. Boiler manufacturers recommend coordinating energy use for washing and ironing etc with times when the heating is on to give you the best levels of efficiency.

If you don't use the electricity at that time or are producing an excess, you can sell it back into the National Grid and receive payment through the Government's Feed-in Tariff scheme.

Domestic micro combined heat and power boilers are a similar shape and size to normal domestic boilers and can be floor or wall mounted. They can be powered by gas, LPG, oil and increasingly by bio-fuels. Installation, maintenance and service costs are estimated to be similar to those of existing boilers but a specialist engineer will be required.

How Does MCHP Work?

There are three main types of micro combined heat and power system:

Fuel Cell - This technology is relatively new and still in development. Energy is taken from the fuel at a chemical level rather than from its combustion.

Internal Combustion Engine - Essentially, these are modified diesel engines hooked up to an electrical generator with heat captured from cooling fluids and exhaust gases. They are more suited to larger commercial installations.

Stirling Engine - This system is currently proving to be the most suitable for domestic use in the UK and incorporates the Stirling engine.
The Stirling engine was invented in the early 19th century and uses a simple cyclic system of gas expansion and compression through heating and cooling to drive pistons and create mechanical energy. This is converted into electrical energy using a generator.

These engines are simple, efficient and quiet and are incorporated into the boiler system to make additional use of the heat produced to generate electricity.

Boiler Manufacturers and Installation

Domestic MCHP systems are an emerging technology and could lead to a significant shift in home heating and microgeneration. Their inclusion in the Government's Feed-in Tariff scheme should encourage consumer uptake further.

Most boiler manufacturers are in the process of developing micro combined heat and power boilers but Baxi has led the way with the 'Baxi Ecogen', which was the first wall hung Stirling based boiler widely available to the UK market.

To qualify for the Feed-in Tariff scheme your MCHP boiler should be installed by a Microgeneration Certification Scheme (MCS) registered installer who will issue the relevant certificate for your application.