Page 194 - Handbook of Energy Engineering Calculations
P. 194

it  is  likely  that  other  building  types  with  high  ventilation  and  electrical
               requirements would also offer attractive investment opportunities.
                  Based on study findings, fuel savings ranged from 3300 to 7900 therms per
               year. Cost savings ranged from $322,000 to $370,000 for the 5-story-building
               case  studies  and  from  $545,000  to  $656,000  for  12-story-building  case

               studies where the synchronously powered, packaged cogeneration unit was
               not used for emergency power.
                  Where  the  cogeneration  unit  was  also  used  for  emergency  power,  the

               initial cost decreased from $257,000 to $243,000, representing a 31 percent
               drop  in  average  cost  for  the  5-story-building  cases,  and  from  $513,000  to
               $432,000, a 22 percent dip in average cost for the 12-story-building cases.
               The average cost decrease shifts the discounted payback period an average of
               5.6 and 5.9 years for the 5- and 12-story-building cases, respectively.

                  Study findings were conservatively reported, since no credit was taken for
               potential  income  resulting  from  PURPA  sales  to  the  serving  utility  at  off-
               peak  hours,  when  actual  building  operating  requirements  fall  below  rated

               cogenerator output. This study is another example of the importance of the
               internal-combustion engine in cogeneration around the world today.
                  Worldwide  there  is  a  movement  toward  making  internal-combustion
               engines,  and  particularly  diesel  engines,  cleaner-running.  In  general,  this
               means reducing particulate emissions from diesel-engine exhaust gases. For

               cities with large numbers of diesel-powered buses, exhaust emissions can be
               particularly unpleasant. And some medical personnel say that diesel exhaust
               gases can be harmful to the health of people breathing them.

                  The  approach  to  making  diesel  engines  cleaner  takes  two  tacts:  (1)
               improving the design of the engine so that fewer particulates are emitted and
               (2) using cleaner fuel to reduce the particulate emissions. Manufacturers are
               using  both  approaches  to  comply  with  the  demands  of  federal  and  state
               agencies regulating emissions. Today’s engineers will find that “cleaning up”

               diesel engines is a challenging and expensive procedure. However, cleaner-
               operating diesels are being introduced every year.


               ENERGY EFFICIENCY OF DIESEL GENERATING UNIT




               A 3000-kW diesel generating unit performs thus: fuel rate, 1.5 bbl (238.5 L)
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