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
8.5: Conclusions
8.5 Conclusions
Table 8-26 is a comparison of the results of the three different modeling approaches. The walkthrough procedure produced the highest estimate of savings and the best payback. It did not provide adequate information for the selection of a specific system, as all options had approximately equal simple paybacks.
| OPTION (NOMINAL KW) | MODELLING APPROACH | 1996 SAVING ($1,000) | PAYBACK (YRS) | IRR (%) | NPV ($1,000) |
|---|---|---|---|---|---|
| 1500 | WALKTHROUGH | 472.6 | 3.8 | ||
| SCREENING | 501.7 | 5.6 | 20.8 | 3,350 | |
| HOURLY | 361.5 | 7.8 | 15.4 | 1,257 | |
| 3400 | WALKTHROUGH | 851.5 | 3.9 | ||
| SCREENING | 869.7 | 4.2 | 26.4 | 6,627 | |
| HOURLY | 616.1 | 5.9 | 19.6 | 2,792 | |
| 3900 | WALKTHROUGH | 1,020.2 | 3.8 | ||
| SCREENING | 944.8 | 4.4 | 25.7 | 7,057 | |
| HOURLY | 618.0 | 6.6 | 16.9 | 2,237 |
The screening approach also projected higher savings than the screening model with higher IRRs and NPVs. Based on the information available at the conclusion of the screening study, one would note that the 3,400-kW system provided the highest IRR, while the 3,900-kW system provided the highest NPV. In contrast, the hourly model clearly indicates that the 3,400-kW system would provide the highest return using either IRR or NPV.
The savings and economic measures computed using the hourly model are somewhat lower than those computed using the screening model and, depending on the relative accuracy and precision of the two studies, would be the basis for a final decision as to whether or not to proceed with development of a cogeneration system at this location.
Copyright American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 1996 under license agreement with Books24x7