Page 323 - Sustainable On-Site CHP Systems Design, Construction, and Operations

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fuel streams into the CHP system. All variables in Eqs. (17-56) through (17-64) are
defined in Table 17-2.
Equations (17-56) through (17-64) can be used to determine average values of any of
the system-level metrics identified earlier in this section and in Table 17-2. Averages for
longer time periods (e.g., a week or a month) can be obtained by increasing the limits
on the integrations or summations to the corresponding start and end times for which
the average values are desired.

Example Application of Data from Simulation and Laboratory Testing
This section demonstrates the use of the algorithms developed in this project for
monitoring the performance of a CHP system and detecting faults and performance
degradation. The demonstration uses both simulated data from models and data from
the laboratory to demonstrate the use of the algorithms developed in the previous
section.
The data used for testing were recorded from the CHP system in the Integrated
Energy Systems (IES) Laboratory at Oak Ridge National Laboratory, ORNL (Rizy
et al. 2002 and 2003; Zaltash et al. 2006). The CHP system consists of a microturbine
generator (MTG), exhaust-to-water heat recovery unit (HRU), hot water–fired absorp-
tion chiller, and cooling tower. The MTG is a 30-kW natural gas–fired Capstone unit
that produces three-phase 480-V AC electric power and releases exhaust gases in the
approximate temperature range 480 to 560°F. A gas compressor is used to raise the
pressure of the natural gas provided by the distributor (at 5 psig) to the pressure of
55 psig required by the MTG. The unit uses heat recuperation to preheat the air before
it enters the combustion chamber, which increases electrical generation efficiency and
reduces the available exhaust heat. The hot exhaust gases pass through a gas-to-water
heat recovery unit, producing hot water at 185 to 203°F. The exhaust gases are then
vented to the atmosphere at approximately 248°F. To increase fuel utilization effi-
ciency, these vented gases could be used to feed a direct-fired desiccant unit, which is
possible at the IES lab, but the IES system is configured with exhaust gases venting
from the HRU directly to the atmosphere for these tests. The hot water output from
the HRU is used to thermally power a 10-ton (35-kW) single-effect LiBr-water absorp-
tion chiller, providing chilled water at approximately 44°F. Cooling for the chiller con-
denser is provided by a closed cooling-water loop that uses a wet cooling tower to
reject heat to the environment.
A schematic of the CHP monitoring system is shown in Fig. 17-1. The monitoring
system not only shows the measured data from the sensors, it also shows the calcu-
lated performance data. The data collected at ORNL were fed into the monitoring
system to simulate real-time CHP operation. The calculated values are shown in the
left bottom portion of the monitoring screen (Fig. 17-1) or inside the component. The
monitoring system is also capable of setting alarm limits for the sensor values and
the calculated values. Although the monitoring system shows measured or calculated
values for any given time and alarm, if a value is out of a reasonable range, it does not
show up on the trends.
The efficiencies are calculated using equations summarized in Tables 17-1 and 17-2.
Trends for the efficiency, effectiveness and energy utilization factor are shown in Figs. 17-2
and 17-3.