Efficiency Benefits
DE can reduce wasted fuel.
Efficiency gains can be obtained in two ways by a shift towards increased DE investment:
- Thermal efficiency gains
- Reduced line losses
Losses through DE – Efficiency Gains
The advantages of generating energy at the point of use are fundamentally thermodynamic. In fuel combustion processes most of the energy is released as heat, while only about 30 to 40% can be transformed into electricity. Electricity generation is therefore necessarily inefficient; unless the heat output is put to use as well.
Centralized power plants waste huge amounts of energy because their heat output cannot be used locally. Efficiency of the US electricity system, for example, is even lower today than in the early 20th century, and far below its potential. Only when electricity generation takes place at the place of demand, in decentralized applications, can the heat output be used and efficiencies of over 80% achieved. The below diagram illustrates the scale of waste in the global power sector. The green arrows on the left represent the total primary energy input from all sources to generate power. The large red arrow represents energy from all fuels wasted in the form of waste heat. Capturing waste heat then clearly represents the largest source of potential for efficiency improvement. High efficiency cogeneration is the DE technology best suited for tackling this potential.
The smaller red arrows represent power consumed by the power plants themselves and the power lost during transmission and distribution respectively. The yellow arrows represent the actual useful energy derived from the original fuel inputs – about a third of the actual energy society should be aiming to use.
Lower T&D Losses through DE – Reduced Network Losses
In addition to the increased efficiency from using the heat output, DE also reduces the distances over which electricity is transmitted to reach consumers, so that network losses are smaller in a decentralized system compared to centralized generation. This further increases the efficiency of a decentralized electricity system.
Losses from transmission and distribution (T&D) lines – the arterial system of central power generation – equaled 9.5% of the total global supply of electricity in 1999 according to the international energy agency. This is equivalent to the total electricity demand of Germany, the UK and France combined and is a colossal waste of energy. Greater use of DE worldwide can avoid most of these losses while also limiting the visual disruption which T&D causes and reducing the growing congestion of the power grid being experienced by most countries.
