An overview concerning combined heat and power production: a smart way to improve energy efficiency

Cogeneration power plants simultaneously generate power and usable heat in a single, integrated system, which achieves a degree of overall efficiency that is much greater compared to electricity production alone. This makes better use of energy conversion and reduces greenhouse gas emissions. Combined heat and power production is already relatively common in Europe while it is less common, for example, in the USA. There is great potential for further implementation throughout Europe and worldwide, including in the industrial sector. Major challenges are the short potential distances for the transport of heat and the fact that consumers’ heat demands vary in quantity, mainly due to seasonal effects, and in quality as different applications require different temperature levels. Cleaner production schemes offer suitable frameworks to foster uptake of combined heat and power production by industry, in particular by small and medium sized enterprises. Cogeneration is also known as combined heat and power (CHP). Although no precise differentiation exists, the term ‘cogeneration’ often refers to central power stations delivering electricity to the general grid, and heat valorisation in this context is often in the form of district heating. The term ‘CHP’ is more common in decentralised applications, industrial settings, local community energy supply or individual applications such as energy valorisation of a biogas plant. The power in cogeneration schemes (CHP units) is usually electricity but it can also be mechanical energy for operating technical equipment such as fans, compressors or pumps (Carbon Trust, 2010). To implement cogeneration, three basic processes need to occur: power production, heat recovery and heat use (Carbon Trust, 2010). Cogeneration is neither a new idea nor an application that is limited to large power plants. A common example of applied cogeneration is the automobile heater, which makes use of heat from the engine to enable comfortable temperatures in the interior of the automobile (Bridgeman, 2011). The concept of cogeneration is smart and very appealing but in practice, a range of challenges need to be met and carefully assessed in order to ensure successful implementation. Electricity can be moved over long distances without significant losses, however, this is not the case for heat for which transport is limited to short distances. Another major challenge lies in the fact that consumers’ heat demands vary both in quantity (heat amounts) and in quality (temperature levels). District heating, which is closely linked to urban planning and can be fostered and promoted directly by the public sector, is often a focus in assessments on how to increase