Page 342 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Sustaining CHP Operations 315

(the steam traps let steam pass through to the condensate system). All piping should be
well maintained, well insulated, and free from leaks. Plant pumps should be selected
and operated to minimize pumping horsepower. Most importantly, pumping horse-
power can be minimized by maximizing hydronic system delta-T (difference between
supply and return temperatures). Of course, many losses are set by the design and con-
struction of the CHP plant itself, for example, pipe sizes, inlet-air duct size, and inherent
pressure drops are set.
Improving CHP plant efficiencies including chiller plant efficiencies are important
and interesting subjects worthy of a separate chapter or even a separate book by them-
selves. Overall CHP efficiency as well as electric generation effectiveness are maximized
by recovering and beneficially using as much of the waste heat as possible. Dumping of
heat must be avoided or minimized. The challenge with improving CHP plant efficien-
cies is that equipment/systems are interrelated and the operations of one system, for
example, effects the operations of another system. For example, higher flow, colder
condenser water allows electric-drive chillers to operate more efficiently requiring less
motor horsepower. But providing higher condenser water flows requires higher con-
denser water pump power (for a given system), and providing colder condenser water
requires higher cooling tower fan horsepower (for a given wet-bulb temperature). The
question is whether the chiller horsepower savings are more than the condenser water
pump and fan horsepower increases (assumes variable frequency drive motors), and
the answer will depend on equipment loading (i.e., part load performance). As another
example, the cost of operating a chiller to generate chilled water for turbine inlet cool-
ing may be far outweighed by the value of increased combustion turbine generator
output. Algorithms exists to optimize individual plant systems, such as the chilled
water and condenser water systems, and to operate equipment along its natural curve
of best efficiency points for a given load and operating conditions. Using power con-
sumption meters, empirical method can also be used to plot power consumption versus
various applicable operating parameters in order to determine operating conditions
that minimize power consumption.
As discussed, the heat rate is a measurement of the power generation effectiveness
and the lower the heat rate the more efficient is the prime mover at generating power
(less fuel is required per unit power output). Minimizing the heat rate will help mini-
mize fuel consumption for a given output. The heat rate is affected by the prime mover
design, by the plant layout and installation (which are fixed in a constructed plant), and
by operating conditions such as the outside air temperature, which can be mitigated
through turbine inlet cooling.
Many institutions are making public, written pledges to reduce their facilities car-
bon footprint, and, as described, the use of CHP inherently minimizes a facility’s carbon
footprint. By minimizing losses, maximizing CHP efficiencies, minimizing parasitic
power consumption, and the heat rate, fuel consumption for a given load is minimized
and CHP environmental benefits will be enhanced.

Operator Training
Plant operators are very important in the success of any facility operations, as it is the plant
operators who are on the front line and can observe and report plant operating conditions
and make key suggestions for improvements, and it is the plant operators, for example,
who implement and make work (or not) management/consultant recommended plant