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,
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