Combined heat and power (Chp)
Author: Professor P.J Harvey, Head of Bioenergy Research,University of Greenwich.
( Article Type: Explanation )
Combined heat and power (CHP – also sometimes referred to as co-generation) describes technologies that generate electricity simultaneously with useable heat in one single, highly efficient process at or close to the point of energy use. When the captured heat is then cooled by linking it to absorption chillers the technologies provide cooling as well as heat and power and are then referred to as tri-generation CHP (CCHP).
Conventional ways of generating electricity in coal and gas fired power stations generate vast amounts of heat which is wasted, (up to two thirds of the overall energy generated), with further 7-9% of electricity lost in the process of transmission and distribution to end-users through centralised grid and local distribution networks. By contrast the relative sophistication of CHP systems means that CHP plants can reach in excess of 90% overall efficiency at the point of use.
CHP systems are specifically designed to meet the thermal demand of the end user at industrial, individual building or city-wide levels. They can encompass a range of technologies and they can be applied to both renewable and fossil fuels. When supplied with locally-sourced biofuels (e.g. plant oil, wood and wood wastes, combustible agricultural wastes, or biogas created in anaerobic digesters from the breakdown of waste organic matter), CHP systems can provide energy with a low/zero carbon footprint. They can also combust glycerol, which has the safest handling properties of all known fuels, at very high efficiency without chemical alteration or the addition of combustion enhancers using a new compression ignition innovation called the McNeil cycle. The driving force behind CHP lies in provision of an efficient, integrated system that combines electricity production and a heat recovery system.
To summarise, CHP benefits include:
• Dramatically-increased fuel efficiency with concomitant cost-savings
• Reduced emissions of CO2 and other pollutants
• Reduced need for transmission and large distribution networks
• Beneficial use of local energy resources providing a transition to a low-carbon future. As a result, the G8 leaders meeting in 2007 issued a direct charge that nations must increase their use of CHP to deliver a “clean, clever and competitive energy future”. Analyses conducted by the International Energy Agency (IEA) indicate that CHP currently generates only 10% of global electricity, but argue that this could rise to 24% with thoughtful, well implemented policy intervention. In Africa, CHP installations running on biofuels will be of tremendous value because they can deliver electricity to small rural communities for which connection via the grid is too costly. They can target poverty eradication at the small-scale farmer level, increase living standards, lower fossil fuel use and improve the ecological footprint of energy production. In recognition of the importance of CHP to Africa, the EU-Africa Caribbean Pacific (ACP) Science and Technology programme has established a new project for 2009-2012 aimed at capacity building to create sustainable non-food biofuel supply chains for CHP in Africa.
