Keywords: cogeneration, power-to-heat ratio, gas turbines, steam turbine, internal combustion engine, production possibility sets, feed-in prices, joint outputs, heat recovery, performance indicators, combined heat and power, CHP, thermal power generation
Combined Heat and Power (CHP) essentials
'CHP essentials' introduces the concept of power and heat 'production possibility sets', starting at the cradle of CHP, i.e., the thermal power generation plant. The latter always occasions 'fatal' heat that is either recovered (the 'merit' of CHP) or wasted (condensing). This split paves the way to defining the production possibility sets of CHP plants, shown for steam turbines, internal combustion engines and gas turbines as main CHP technologies. Three indicators are widely used to monitor CHP performance: the overall conversion efficiency (quantity indicator), the (mostly ill-defined) power to heat ratio (quality indicator), the 'quality norm' advertised by the EU Directive 2004/8/EC. The paper levels the field for discussing the crucial issue of identifying and quantifying CHP activity.