As concerns grow about environmental protection, global warming, and steadily rising energy prices, public interest is focusing more on energy efficiency. Germany is promoting and subsidizing efforts to expand the use of renewable energy, better building insulation, and cogeneration to make power and heat supply systems more energy-efficient. Current subsidy legislation, driven by economics and defined energy-efficiency and climate protection goals, is aimed at expanding combined heat and power generation to the extent that 25 percent of the nation’s electric power will be produced by cogeneration plants by the year 2020. Yet even as lawmakers recognize the significant contribution made by cogeneration to increasing energy efficiency, there are ongoing discussions about whether these subsidies make good sense. The doubters, in most cases, are contrasting figures and data that make no sense in comparative analyses, pitting, for example, the energy utilization factors of cogeneration plants against the electrical efficiency of plants generating purely electric power. Ultimately, it is the efficiency of the systems in our energy supply network that are the decisive variable. When electricity has to be generated from fossil fuels because currently available renewable energy sources are unable to completely meet the demand, waste heat is generated that is discharged to the environment without being utilized. According to publications, cogeneration enables fuel savings of anywhere from 10 to 20 percent compared with the separate generation of heat and power. It should also be noted that the theoretical savings potential is actually much higher. In theory, design and operation would always strive for optimized pairing of heat and power generation, entirely ruling out the possibility for peak-load heat generation from direct- fired boilers. In industrial plants, savings potentials of up to 40 percent are readily achievable, because in most cases the consumption of heat and electric power remains relatively constantand enables a narrow optimization window.
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