Combined Heat and Power

摘要

Combined heat and power (CHP) is the sequential use of one fuel source to produce power and thermal energy. The energy cascade provided, avoids losses that occur when power is traditionally generated at a central station power plant and thermal energy is consumed on site in a boiler. CHP can be used in either a topping cycle or bottoming cycle mode with topping cycles being the most dominant application. CHP was used at the beginning of the 20th century -- primarily for industrial uses. With the expansion of the electric grid and cheap raw energy, its use declined. A major expansion of the technology occurred in the eighties as a result of the Public Utilities Regulatory Policy Act of 1978. As a result of heavy opposition by the electric utility industry, the interest in CHP declined towards the end of the eighties. High-energy prices and constrained generating capacity has renewed interest in the technology in 2001. Four "prime movers" are considered in CHP applications. Available today are the combustion turbine and the reciprocating engine. The combustion turbine has the advantage of being able to provide high quality heat to applications. The reciprocating engine however, it typically more efficient in the smaller applications (< 3 mw). Micro turbines are just becoming commercial with their share of growing pains. The industry looks forward to their value proposition of being as efficient as reciprocating engines while being cheaper to purchase and maintain. Fuel cells offer enormous promise regarding improved efficiency and emission reductions. There are significant technical hurdles to overcome for this promise to be realized however. The economics of CHP are robust in California today. Simple paybacks for combustion turbine/process heating applications, combustion turbine/building cooling applications, and reciprocating engine/water-heating applications can be as low as from 2 to 3 years. As important to society as the economics, are CHP's contributions to social goals. A 5 mw CHP facility could be expected to save enough energy to heat 1,500 homes, reduce CO_2 emissions as if 1,400 cars were taken of the nation's highways and reduce NO_x emissions as if 8,400 cars were removed from the road. CHP is an effective but capital-intensive energy management technique. Therefore reliable rules and tariffs need to be in place to attract the investment. This places a significant responsibility on regulators and legislators to produce such an environment if we, as a society, are to reap the aforementioned rewards. The needs of the electric utilities' investors must be balanced against the need to conserve energy and reduce both green house gases and criteria emissions.