Page 205 - Sustainable On-Site CHP Systems Design, Construction, and Operations

178 De s i g n

If the project is near critical sensitive equipment like electron microscopes in a nearby
building, extensive inertia bases may be required for the prime mover equipment.
Direct equipment breakout noise can be attenuated through the use of equipment
enclosures, where, for example, the CTG or IC engine generator is installed in its own
manufacturer supplied enclosure. In addition to an engine enclosure, a building can be
provided to not only reduce noise levels outside the plant, but also protect the CHP
equipment from the outdoor elements. When a CHP plant building is involved the
building elements also can provide some noise attenuation. Sound-rated doors and
windows must be incorporated, and the inner walls of the CHP plant can be provided
with an acoustical liner (provide a screen mesh for liner protection). Any opening into
or out of the CHP plant such as vents and louvers must also be acoustically treated.
Acoustical louvers can be provided on all air intakes and an inlet-air duct silencer
should be used on any combustion air-inlet system.
Heat recovery equipment helps to reduce the exhaust noise level, but an exhaust
muffler will likely still be required with an IC reciprocating engine. To help minimize
the adverse effects of vibration, vibration isolators are used on equipment and expan-
sion joints are used at points of connection to reduce vibration transmission, to account
for any small pipe/equipment misalignments, to help accommodate thermal expan-
sion, and to prevent excessive force and/or stress from being applied to equipment.
Excessive ambient noise may also require filing for permit as discussed in Chap. 11.

Plant Controls/Integration
Plant controls, which include monitoring, measurements, equipment starting and stop-
ping, alarms, and modulating control are an important, if not critical, piece of a successful,
sustainable CHP plant. As discussed in Chap. 16, an exceptional operator may not need
many visual readings to know if the plant is operating properly; he or she can tell by the
nature of equipment sounds, by the feel of vibrations, and by the touch of a hand
(e.g., to detect if a bearing or motor may be overheating). On the other hand, in today’s
world of modern computer-based, direct digital controls (DDC), making provision for
automatic monitoring and trending of operating points can make it easier for CHP plant
operators to evaluate and diagnose (i.e., to troubleshoot) any future system problems,
as well as make it possible to optimize CHP operations. In fact, modern controls
systems can adapt to changing conditions and parameters (adaptive control) as well as
warn ahead of time of pending failures by trending system parameters.
The prime mover and generator will have its control systems, for example, a con-
stant speed governor to maintain a constant engine-generator speed (rpm) and to
modulate the fuel control valve to match generator load. The electric power generator
will also have its own safety controls and paralleling system. The balance of the CHP
plant must be controlled and operated by the plant control system. Ideally, many of the
engine and electrical system monitoring points are incorporated into the plant control
system (see Chap. 17). The control system needs to be fast acting and capable of real-
time PID (proportional, integral, derivative) loop control. Many CHP plants do not have
operators located at the plant, and these plants must not only be automatic, but remote
monitoring and alarm needs to be provided to an operator at a remote point.
As previously discussed in this chapter, one of the first steps in planning for the
design of CHP plant control systems is to develop for each system a piping and instru-
mentation diagram (P&ID), which shows all major equipment, valves, instrumentation,
and proposed method of control for that system (e.g., the HW heat exchanger steam