Page 335 - Sustainable On-Site CHP Systems Design, Construction, and Operations

308 Op erations

CHP Data Analysis
Given the plant data, plant personnel and/or outside consultants can analyze CHP
plant operations. Important information can be gleaned directly from the basic data,
and there are a number of metrics that can be employed to analyze CHP plant opera-
tions. Results of data analysis can be benchmarked against other facilities and other
plant operating options in order to draw comparisons, contrasts, and conclusions.
Review of basic data obtained directly provides important information regarding:

• Total electricity generated
• Total heat produced
• Tons of cooling generated
• Amount of fuel consumed
• Electricity sales
• Thermal sales (heating and cooling)
• Key plant operating parameters, for example, temperatures, flows, and
pressures of steam and condensate systems, hot water systems, chilled water
systems, and condenser water systems to gain a better understanding of their
impact on overall plant efficiency

Metrics
In addition to the basic CHP/facility data, important metrics (performance indicators)
can be developed/calculated using the raw data taken and recorded from the CHP
plant in order to better understand the plant operations, and can provide guidance
toward more efficient sustained plant operations. Care should be taken not to draw
broad conclusions or to make false assumptions regarding individual metrics. Key CHP
metrics include the following:

• Cost per net kilowatthour generated
• Cost per therm [or Btu, or kilojoule (kJ), or other appropriate unit of heat recovered]
• Cost to produce CHP facility services versus the BAU case
• Amount of money saved by employing CHP versus the conventional BAU case
• ROI
• Overall CHP efficiency (which is equal to the sum of the net power output and
the recovered heat divided by the total fuel input)
• FERC efficiency in the United States (the recovered heat is multiplied by 0.5 in
the CHP efficiency calculation mentioned above)
• CHP heat rate (which is equal to fuel input per power output measured in Btu/
kWh or kJ/kWh)
• Electrical generation efficiency (which is equal to net power output divided by
fuel input in consistent units)
• Value-weighted energy utilization factor [which is equal to the value of the power
plus the value of all thermal uses divided by the fuel input (see Chap. 17)]