tively identify plant deficiencies enables
you to catch problems as they begin to
occur, before they severely degrade performance. Data values can be collected,
stored and monitored in real time.
Individual component performance data
can be viewed on the human-machine
interface (HMI) screen or accessed by a
desktop Internet connection. One year’s
history can be stored on the system, and
the data can be easily downloaded to a
plant operator’s desktop or network drive.
The screen image in figure 1 shows the
type of information that performance
monitoring systems can make available
to chilled-water system operators.
In addition to measuring key data
points relevant to power in kilowatts in
instantaneous demand, refrigeration
capacity and leaving water, performance
monitoring will also track and measure
the difference between refrigeration temperature and leaving water temperature.
This is called the ‘approach.’
By monitoring and measuring the
approach as it degrades with normal
operation, operators can assess and determine when to schedule maintenance on
the condenser tubes. This maintenance
is a highly labor-intensive process, and
most operators do not know what their
typical approaches should be. Consequently, having a management tool that
measures the approach and gauges when
to schedule costly downtime helps not
only to ensure reliable operation, but also
minimizes the impact and cost of planned
maintenance. This can also be a valuable
tool in helping to analyze the effectiveness of the water treatment program.
Most plant operators are motivated
by performance evaluations or appropriate
incentives to achieve plant optimization
within budget guidelines. Performance
monitoring not only supports plant operators in the daily execution of this responsibility, but it also goes a significant step
beyond to help companies minimize their
electricity use and control operating costs.
Tight operating-cost control is especially important in competitive markets,
most notably when energy prices are
increasing at double-digit rates. Plant
managers now have a tool to minimize
operating cost without compromising
plant operation or building comfort. To
maximize a plant operator’s ability to
analyze central plant performance,
selected data may be exported from the
plant’s programmable logic controller
system via the Internet or the operator’s
desktop computer.
Step 3: Take Corrective Action
Simply having data is meaningless
unless the data is actionable. Performance
monitoring captures, organizes and compiles data, enabling operators to easily
assess how efficiently and effectively their
plants are operating and to make any
needed operational changes.
Once captured, the data will be stored
on the PLC system. The stored data can
be accessed by anyone designated by
the owner/operator, a third party or an
assigned employee. As data is compiled,
they are accessible via select screens,
which allows for performance tracking
of individual components and data points.
The HMI is the central feature of this
service. It is responsible for data acquisition from power meters, flow meters and
differential temperature indicator devices
as well as directly from the chillers. The
HMI screens are customized for each
installation and capture all of the data
values that plant operators need to proactively monitor for maximum plant efficiency.
With performance monitoring integral
to the plant’s control system, it is easy
for operators to take corrective action to
resolve performance issues. Integration
is the first step in long-term performance
monitoring and control strategy, as soft-
Performance monitoring for CHP installation.
ware can be designed to take predetermined corrective action through controls
integration.
Step 4: Assess Effectiveness
Data only has value if it is actionable,
and if the results of the corrective actions
can be measured and assessed. Plant operators can remotely query their data at any
point during operation and assess whether
any corrective steps have achieved their
desired result. Prior to the introduction
of this capability, assessing performance
and operating characteristics had been an
imperfect science. Due to the difficulty of
extracting exact performance data, plant
operators were not able to fully monitor
and optimize their central plant as an
operating asset. In the days of low-cost
electricity, this was not a significant business issue, but as electricity costs have
risen – in some cases skyrocketed – operating cost is suddenly a significant concern,
particularly during peak hours.
Step 5: Track Energy Savings
As is the case with all business investments, capital equipment or services are
purchased to either make money or save
money. Performance monitoring will save
money. It is a business tool created for
the express purpose of reducing central
plant life-cycle costs by effectively increasing the efficiency of central plant operations. Performance monitoring helps
Courtesy TAS.
