Cogeneration Design Guide
Including two case studies to help illustrate the entire design process, this guide offers a thorough discussion of the theoretical as well as the practical aspects of a cogeneration system design.
TABLE OF CONTENTS Cogeneration Design Guide
8.3: Screening Analysis
8.3 Screening Analysis
The scope of a screening study was described in section 6.6. It includes additional collection and analysis of load data, cogeneration system performance, system costs, and incremental costs.
Data Collection and Analysis
Electric data for the most recent 12 months are shown in Figures 8-4 and 8-5. Gas use for the 12-month period is shown in Figure 8-6. An initial task in the screening study is the normalization of the monthly billing data, adjusting the consumption as billed to uses that are based on the length of calendar months (see Figures 8-7 and 8-8). Demands were assumed to be unchanged. Electric load factors were computed based on the revised usage and are shown in Figure 8-9. Electric costs were computed on a month-by-month basis using the following rate schedule:
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A customer charge of $250/month.
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Maximum demand was billed at $6.00/kW a month and is based on the actual peak demand occurring during the month.
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On-peak demand was billed at $15.00/kW a month and is based on the actual on-peak demand occurring during the month.
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On-peak energy was billed at $.045/kWh ($12.51/GJ), with the on-peak hours extending from 10:00 a.m. to 6:00 p.m. on weekdays.
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Off-peak energy was billed at $.035/kWh ($9.73/GJ).
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All charges were subject to a 5% state sales tax.
Figure 8-6: Monthly gas usage.
Figure 8-7: Actual vs. normalized electric energy hospital.
Figure 8-8: Actual vs. normalized displaceable fuel hospital.
Figure 8-9: Monthly electric load factor hospital.
The above rates are graphically shown as Figure 8-10. On-peak charges...
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