Microturbine, chiller and cooling tower, together making up an integrated energy system, being tested at the IES Test Center at the University of Maryland

This engine-driven air conditioner is part of the integrated energy system which provides base load cooling for Zone 1 of the Chesapeake Building

CHP can also improve indoor environmental quality (IEQ). US buildings consume at least 30-50% more energy than necessary to provide adequate IEQ. However, heating, ventilation and air conditioning (HVAC) systems often do not provide sufficient humidity control or meet a building’s need for outside air. In combination with a desiccant dehumidifier, CHP systems can provide better humidity control than conventional systems, and reduce the potential for mould and bacteria growth.

Table 1 summarizes the costs and performance of CHP technologies. While price and performance data on reciprocating engines and gas turbines are fairly well established, data for fuel cells are based on a limited number of demonstration projects. As a result, comparisons of price and performance should be interpreted with some uncertainty.

The scope for the widespread use of domestic-sized ‘micro’ CHP in Europe has been much discussed, but greater potential exists for the use of the same technology based on the use of liquid biofuels, writes JEREMY HARRISON. However, in order to unlock the potential environmental benefits of biofuelled CHP, the relative taxation and pricing structures for fossil and plant-based fuels must be adjusted.

Micro CHP has the potential to revolutionize the electricity industry in the UK and much of western Europe. It is a cost-effective method of generating electricity with an estimated potential capacity of up to 22 GW installed in the UK, significantly greater than the entire nuclear industry.

Not only is it economically viable for the end-user without any form of subsidy, it also represents the most cost-effective carbon mitigation strategy of all technologies which are at or near market.

However, current estimates of market potential are invariably based on the assumption that micro CHP units will replace gas-fired boilers in hydronic central heating systems. Whilst this may be true in the early stages of market development, there is a substantial additional potential for installations in rural areas where a natural gas network is not available and opportunities for network support are considerably greater. Including such installations in the estimates for micro CHP raises the potential by around 10% in the UK, but up to 100% in other EU States, such as France.

Of greater significance, perhaps, is that these installations may also provide the earliest opportunity for the utilization of liquid biofuels, raising carbon mitigation potential to over 50 million tonnes per year in the UK, and demonstrating the longer term role of micro CHP as a carbon-free domestic energy supply option.


CHP has been identified by the UK Government as a key component of its carbon dioxide abatement programme and it also represents the most significant individual measure for achieving the European Union’s carbon dioxide reduction targets (150 Mt of a total of 800 Mt). In order to meet its carbon dioxide emission reduction target agreed at Kyoto, and to maintain security of supply, the EU aims to double the proportion of power generated by CHP to 18% of total capacity.