Combined Heat & Power Explained

By Ken Warner, MD, Energy Renewals

Combined heat and power (CHP) integrates heat and power or electricity into one process for greater levels of efficiency.

The benefit of CHP is its energy efficiency reducing ‘primary energy’ consumption without compromising the quality or reliability of the energy supply.

The cost savings can be impressive, between 15% and 40% compared to electricity sourced from the grid and heat generated by on-site boilers, according to ADE the Association for Decentralised Energy, the voice of cost effective efficient, low carbon, user-led energy.

Effectively, CHP generates electricity whilst at the same time capturing the heat produced as part of the process compared to the traditional way of producing electricity when the heat is lost. In fact, coal and gas fired power stations lose up to two thirds of the overall energy consumed as a result of heat wastage.

Efficiency ratings achieved at CHP plants can be in excess of 80% whereas efficiency of gas power stations in the UK range between 49% and 52% and coal-fired plants perform at around 38% efficiency. In addition, CHP energy is produced locally which means there is no energy lost through transmission and distribution of electricity through the National Grid and local distribution networks which would usually be around 7%.

CHP can also provide cooling delivering a trigeneration energy process providing heat, power and cooling, if the unit works in conjunction with an absorption chiller. Trigeneration can be fitted in buildings with continuous or seasonal cooling demands providing a low carbon way to achieve their heating and cooling needs. The waste heat produced by the CHP unit provides the required energy to produce chilled water.

Whilst you may be tempted to think that such new technology is for the likes of large scale businesses, in fact, it can be scaled up or down. Packaged and small scale CHP meets the heat requirements of large and medium-sized standalone buildings such as an office complex, hospital or block of flats as well as smaller sites such as a leisure centre, supermarket, care home or hotel.

CHP can also be designed for households or micro businesses.  Micro-CHP typically has an electrical output of less than 2kWe and as a replacement for a standard domestic gas boiler, it generates both electricity and heat for space heating and hot water.

There are over 350 industrial CHP sites in the UK, ranging in scale from a few MWe to the equivalent size of a conventional power station. These CHP plants provide heat in the form of hot water or steam and even electricity, depending on the needs of the site and its production processes.

According to government figures as of March 2015 there were 643 MicroCHP schemes registered to receive Feed in Tariff payments. By the end of January 2017, the figure was 5,976 MW (890,438 installations), a 10% increase in FIT installed capacity compared to the same period in 2016 and a 5% increase in the number of installations.