Trigeneration

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Trigeneration or trigen is the simultaneous production of mechanical power (often converted to electricity), heat and cooling from a single heat source such as fuel or solar energy. As with cogeneration, the "waste heat" byproduct that results from power generation is harnessed, thus increasing the overall efficiency of the system.

Usually space heating and hot water storage tanks serve as a heat sink for reasonable waste heat utilization. In summer, the heat demand is much lower but the heat of the electric generation process can be transformed into cooling energy by an absorption chiller. Trigeneration is sometimes referred to as CCHP (combined cooling, heating, and power generation).

Conventional thermoelectric stations convert only about 1/3 of the fuel energy into electricity. The rest is lost in the form of heat. The adverse effect to the environment from this waste suggests a need to increase the efficiency of electricity production.

One method for more efficient production of electricity is the Cogeneration of Heat and Power, where more than 4/5 of the fuels energy are converted in usable energy, resulting in both financial and environmental benefits.

Cogeneration is the consecutive (simultaneous) production and exploitation of two energy sources, electrical (or mechanical) and thermal, from a system utilising the same fuel. Combined heat and power production (CHP) is applied in industry and buildings where there is simultaneous demand of electricity and heat and, usually, when the annual hours of operation exceed 4000.

In warmer climates the need for heating is limited to a few winter months. There is, however, significant need for cooling (air conditioning) during the summer months. Heat by a cogeneration plant in this case is used to produce cooling, via absorption cycles. This “expanded” cogeneration process is known as trigeneration or combined heat, cooling and power production (CHCP).

CHP is a well-known acronym for cogeneration (combined heat and power production); CHCP may be a less familiar acronym for trigeneration (combined heat, cooling and power production). A modern American acronym is BCHP, Building Cooling, Heating and Power, for trigeneration applications in buildings. In German, the corresponding acronyms are KWK, Kraft-Waerme-Kopplung, or BHKW, Block-Heizkraftwerk, and KWKK, Kraft-Waerme-Kaelte-Kopplung, respectively.