Page 206 - Sustainable On-Site CHP Systems Design, Construction, and Operations

The Engineering Pr ocess 179

supply valve will modulate to maintain a HW supply temperature of 140°F). Often, as
a second step, a point list is prepared outlining all of the CHP plant’s: temperature,
pressure, and flow measurements; consumption meters (power, Btu, water); points of
modulating control (e.g., CHW pump speed or steam control valve position); valve
position; equipment to start or stop; equipment status (on/off); as well any alarm inputs
and alarm outputs (e.g., catalyst temperature of 1100°F is an alarm input and sounding
the alarm itself is an alarm output). The point list should also indicate any required
calculated points, such as CHP or Federal Energy Regulatory Commission (FERC)
system efficiency, or the value weighted energy utilization factor (please see Chap. 17).
Flexible controls that are well documented, easy to troubleshoot, and easy to mod-
ify are of great benefit to knowledgeable CHP plant operators. Future plant operating
constraints are likely to change along with facility business needs. Therefore, flexible
controls and well-planned instrumentation can assist in facilitating future additional
needs.

Sequence of Operations
Understanding how the proposed CHP plant will operate as well as the nature of the
facility loads (peak, profile, and seasonal) is critical to developing a workable sequence
of operations that will help the proposed CHP plant be sustainable. The developed
available thermal uses will also impact the proposed sequence of operations. For
example, will the proposed engine generator (or CTG) be used to meet the facilities
base electric load and therefore always be fully loaded? Or, will part load operations
need to be considered? Can all of the heat be used or will some heat dumping be
required? When and where can heat be used? At a higher level, decisions can be made
regarding which equipment would be most beneficial to operate. Chapters 17 and
18 provide some guidance regarding operational metrics and sustainable CHP plant
operation.

Intangibles
As a CHP facilities director once said, good karma is the key to selecting a CHP design
team that works effectively, communicates well, and on a good day has fun, and will
result in a better CHP design. Pragmatic, holistic approaches may prove more effective
than overdesigning the central CHP plant. For example, it may prove more cost-effective
to concentrate on improving the distribution system than initially requiring oversized
distribution pumps. It may be more cost-effective to get higher delta-T coils and better
control valves than to add more chillers. Retro-commissioning building controls may
free up large amounts of capacity that can be better utilized elsewhere (e.g., simultaneous
heating and cooling is shockingly common).
Specifying classroom and hands-on training as a part of every major equipment
purchase is often vital to achieving sustainable CHP plant operations. Specifying thor-
ough start-up and commissioning provisions can go a long way to ensuring that CHP
plant equipment and systems operate as designed and can make more likely a success-
ful transition from construction to operations. The commission team should be brought
on board at the beginning of the design processes (programming). The benefit that CHP
system operators obtain from commissioning and training is invaluable in their under-
standing of how best to achieve profitable and sustainable CHP plant performance in a
challenging energy use and cost environment.