Page 111 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Packaged CHP Systems 89

outputs. This inflexibility means that in order to use packaged systems, a family of pack-
aged systems must be available to meet the energy demand for a wide range of applica-
tions. Further, the preengineered/preassembled features result in a well-defined layout
that may not have the flexibility to be installed at every site. Modularity mitigates this
restriction but does not eliminate it. Hence, the desirable features of a packaged CHP
system may yield degrees of output or layout inflexibility that could be best addressed
by similar offerings in a family of packaged CHP systems.

Enhanced Performance
The packaged CHP system is preengineered to maximize both the output energies of
the prime mover and TAT device, and the CHP (or fuel utilization) efficiency to pro-
duce them. These features are accomplished through the proper matching of the major
CHP components and their operating characteristics and requirements. Parasitic losses
are minimized. Therefore, a packaged CHP system can achieve, at least, a slightly
higher performance than a similar system that is custom engineered for the site.
However, the primary performance benefit of a packaged CHP system comes from its
expanded functionality.
Any CHP system will achieve a high level of performance if it is base loaded to
match the energy demands of a facility and, therefore, operates continuously. Such a
situation may be encountered with small- and moderate-sized industrial customers
who employ a process with a continuous thermal energy demand such as for hot
water. This situation may also be encountered for commercial customers located in
climates where the building requires either continuous space heating or continuous
space cooling.
There are, however, many CHP opportunities for customers, particularly commer-
cial, governmental, and institutional customers, when the thermal energy demand is
not continuous throughout the year. Under such circumstances, the ability of the CHP
system to deliver alternative thermal energy outputs (e.g., hot water for space heating,
domestic hot water, and chilled water) becomes critical to realizing the significant CHP
performance advantage over the traditional utility methods delivering comparable
energy streams.
The ability of a CHP system to deliver alternative energy outputs can be a complex
challenge. It requires: (1) engineering efforts to select and match components, and to
develop the control strategies to ensure that the system operates reliably and safely;
(2) system design and assembly efforts to ensure that component placement does not
compromise performance such as may be encountered with longer duct runs or ther-
mal effects; and (3) system validation/qualification efforts to ensure that the system
achieves its promised performance. These three characteristics must match those of a
properly designed packaged CHP system. Hence, the expanded functionality of a well-
planned packaged CHP system can provide a more cost-effective pathway to achieve
high performance for customers with noncontinuous energy demands. In some circum-
stances, properly engineered packaged CHP systems are the most cost-effective means
available to achieve acceptable performance for customer needs.
Note that “enhanced performance” is also one of several benefits of selecting a pack-
aged CHP system. There are instances when the lower installation cost of a packaged
CHP system—without expanded functionality—justifies its selection as the preferred
approach to meet noncontinuous energy demands.