Heat & Power Demands Further infomation
In an ideal situation, the demand information available would be based on heat and power consumption measured every hour for one year.
In the case of a gas engine – at present the most common generation unit for packaged CHP – the heat to power ratio is about 1.5:1. This means that, for every kilowatt (kW) of electricity generated, about 1.5 kW of heat will be generated for use. For gas turbine-based CHP systems, a heat to power ratio of 1.5:1 up to 3:1 can be expected. An understanding of site demand will indicate the level of simultaneous heat and power demand that a CHP unit would experience for 4,500 hours/year or more.
Information on electricity consumption might be available from the electricity supplier’s half-hourly meter readings. This information can be supplied on a computer disk and will require some manipulation and analysis using a spreadsheet package.
N.B. Check the units. Half-hourly consumptions measured in kilowatt hours (kWh) must be multiplied by two to convert them to the instantaneous demand measured in kilowatts electrical (kW).
Heat demand data are rarely comprehensive and, where information is sparse, some degree of estimation may be required. The monthly fuel bills will provide an indication of seasonal variation. However, for weekly and daily profiles it is helpful to understand the operating pattern of the facility (building or process) and to back this up with a short term monitoring exercise or audit. It is important to get as close as reasonably possible to half-hourly consumption figures and to avoid assessing demand from data averaged over long periods of time.
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