Page 193 - Handbook of Energy Engineering Calculations
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combination also ensures a reasonable constant, cost-effective supply of
essentially free electric power for general building use.
FIGURE 4 Packaged cogeneration I-C engine unit supplies waste
heat to desiccant regenerator. (Power and The Meckler Group.)
Recoverable internal-combustion engine heat should at least match the heat
requirement of the regenerator, Fig. 3. The selected engine size (see a later
procedure in this section), however, should not cause the cogeneration
system’s PURPA (Public Utility Regulatory & Policies Act) efficiency to
drop below 42.5 percent. (PURPA efficiency decreases as engine size
increases.) An engine size is selected to give the most economical
performance and still has a PURPA efficiency of greater than 42.5 percent.
The utility study indicated a favorable payout period and internal rate of
return both for retrofits of pre-Title-24 office buildings and for new buildings
in compliance with current Title-24 requirements (nominal 200 to 500
cooling tons). Although the study was limited to office-building occupancies,