Page 301 - Sustainable On-Site CHP Systems Design, Construction, and Operations

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The functional types of diagnostic algorithms needed are
• Component-level diagnostics. Diagnostic algorithms that monitor component
performance on a continuous basis to detect and diagnose faults in system
components.
• System-level diagnostics. Even if individual components are operating properly,
the system as a whole may not be operating optimally. Therefore, there is a need
for diagnostic algorithms that monitor whole-system performance on a contin-
uous basis and detect and diagnose faulty and degraded operation.
• Building integration diagnostics. Because the thermal output of CHP systems is
integrated with existing chilled and hot water distribution loops, there is a need
to optimize the performance of the integrated system.
• Prognostics. These tools are needed to enable operation and maintenance personnel
to anticipate and plan for repair and maintenance to maintain performance and
minimize downtime.

Performance Monitoring
This section explains the purpose of and a general approach to performance monitoring
and commissioning verification. This section also specifies the equations for perfor-
mance monitoring of all components of the generic CHP system. The components can
be combined in various ways to create CHP systems and, therefore, these algorithms
can be used to monitor the components of many different CHP system configurations.
The performance of CHP systems can be categorized according to the outcome of
primary interest. CHP systems have the objective of providing both electric power
and useful heat at the lowest cost possible, while meeting other requirements such as
constraints on environmental emissions. Once the physical system is designed and
built, operating costs can be controlled by maintaining efficient operation (maintain
to sustain). This involves both operating the system well (ideally optimally) and
maintaining the system so that it can perform efficiently. Efficiency should be maxi-
mized to minimize fuel use (and fuel cost) subject to meeting (but not exceeding)
facility loads. Of course, this must be balanced against the cost of each additional
maintenance activity.
The algorithms, when implemented in a tool, provide information to CHP system
operators so they can initially ensure that the performance of their CHP systems and
their individual components meet performance expectations established by the project
engineer or manufacturer(s) (through CxV) and then monitor performance to quickly
spot degradations in efficiency sufficient to warrant changes in operation or maintenance
action. Performance monitoring can then serve as the basis for corrections to operation
and initiation of maintenance (i.e., condition-based operation and maintenance).
To enable operators to track CHP system performance and detect problems, algo-
rithms are provided for monitoring the performance of the overall CHP system and the
efficiency of each individual component. The overall efficiency is an indicator of how
well the system is converting fuel into electricity and useful heat. Significant degrada-
tions in system efficiency indicate both a loss in the capacity to generate these useful
forms of energy and an increase in fuel use per unit of useful output energy. The latter
would lead to increased fuel costs.