Combined Heat and Power

I just completed a webinar refresher on combined heat and power systems.  If you don’t know or have never heard of a combined heat and power system just picture a jet engine that doesn’t move.  The heat coming out of the exhaust is used to make steam.  On the other end, the rotating fan is connected by shaft to a generator and produces power.  Another type of system uses a boiler to make steam.  The waste heat from the flue gas is reclaimed using a heat exchanger to make additional steam.  The primary steam is then routed to a turbine which in turn, turns a generator and makes electric power.  The secondary steam is sent to whatever process will utilize the steam, such as an absorption chiller, for air conditioning.  Most CHP systems are well suited for industrial applications where large quantities of steam and power are required. However, smaller systems are also made and suited for light commercial applications.  Advertised efficiencies run between 70 and 75% depending on manufacturer.  These machines are fairly reliable and so, in the course of my practice, I have only encountered one instance where a gas turbine (jet engine) failed to perform as required.  Two engines were installed in a university setting and used to provide steam and power to various campus buildings.  Shortly after installation, it was noted that one of the gas turbines was not performing as warranted by the manufacturer.  After review of the design of the entire system, it was determined that one of the gas turbines was not performing according to its design specifications. The claim was finally resolved when the manufacturer agreed to replace the machine with a new gas turbine.

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