Page 167 - Boiler plant and distribution system optimization manual

152 Boiler Plant and Distribution System Optimization Manual

Advantages/Disadvantages
This option may take an extensive analysis
but should not be overlooked as a way to improve
the bottom line of your operation. High cost, load
matching, utility intertie, red tape and pollution
control are a few of the challenges that must be
faced with cogeneration. It is a very good way to
reduce steam and electrical power costs and may
be well worth the trouble.
Figure 10.46—Heat Pumps can raise efficiencies sig-
nificantly when combined with low grade waste heat
from engines, boilers and turbines. 9. COMBINED CYCLE ELECTRICAL
GENERATION

a cogeneration facility at a good economic ad- Cost
vantage. Peak shaving is another consideration, a High
large part of many electric utility bills is for “de-
mand” charges which is a charge based on the Potential Savings
peak demand for electricity and not actual energy High
use. Often the peak demand for electricity occurs
at the same time as the demand for other types of Description
energy such as heat and cooling, so if the onsite Because of the high price of electricity in some
generation of electricity can reduce electrical de- sections of the country, it is very cost effective to
mand and provide other forms of energy at the use a Combined Cycle plant to provide steam and
same time, large savings are possible. The key to power while producing electricity. A utility plant
effective cogeneration is to have both electrical usually wastes about 68% of the input energy and
and heat demands occur at the same time. (Figure another 5-8% can be lost in transmission and dis-
10.47) tribution of the power to the plant.

Figure 10.47—Cogeneration is
best suited for a location where
both the electrical load and waste
hear load are consistent like in
this case where the electric pow-
er requirement and the require-
ment for steam, a product of the
heat from the cogeneration ex-
haust both exist uninterrupted
for a maximum number of hours
a year. The economics of cogene-
ration declines to the degree that
either the demand for steam or
electricity is not consistent.