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)