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100MW diesel station in Macau

EXERGY Examples for 2004 data off G7/G8 2-stroke 103 rpm Diesel Engines at the Coloane power station which belongs to Companhia de Electricidade de Macau - CEM, Macauan S.A.R, of The Peoples Republic of China.

This document describes a number of EXERGY analysis examples from the G7/G8 2x49 MW Diesel generators operated in Coloane power station in Macau.

Efficiency Alarms

Detection and alarming of efficiency excursions is a major feature of the EXERGY system which among others distinguishes it from conventional packages. The efficiency alarms identify deterioration of unit thermal efficiency (or specific fuel consumption) in real time, quantifies it in monetary terms, tracks down the root cause of the excursion. and notifies the Unit Operator (say). If a simple, costless remedy can be found, Exergy recommends it. Alarming can be implemented in two ways.

1. Alarms can be sent via email to a custom list of addresses.
2. An alarm client can be installed on any PC. This links to the server using internet protocols.

System tray when an alarm has been detected

System tray when an alarm has been detected

All alarms go to a database table. By default, this is in an MS Access database but it can be located within an enterprise database

The alarm client is a system tray component. The tray icon flashes and beeps once. An efficiency alarm is shown on the left.

Screenshot of EXERGY alarm

Screenshot of EXERGY alarm

In the screenshot to the right, note the unit number, date, and cost of the excursion are displayed. The costs is in 2004 oil prices (which means that the fig. 2 excursion today would cost some 600.0 MOP/hour). If the excursion is associated with a controllable parameter, then the alarm includes recommendations like in fig 2 above which are intended as heavy hints to the plant operators. In this case, if followed up, the efficiency is restored and a much greater loss is avoided.
To further investigate the alarm, associated trends can be displayed. Pressing the Analyze button will bring up trends associated with the alarm. EXERGY is designed to work with plant archive systems like PI and the PI Processbook application or other industry-standard graphics. However, this demo assumes that these are not present, hence the Analyse function uses the Plant Explorer, an application being developed by GNS and Eli Yasni for plant simulation and auto-optimisation.

Trends showing the unit heat rate deterioration and the associated causes



For the example, the upper graph shows the power (black line) and the efficiency (blue line) for the plant. The plant is G8 plus the exhaust boiler of G7 plus the steam-turbine plant. Note that efficiency is steadily decreasing (whilst the losses in red line, it mirror image are increasing). The Exergy Audit has identified that the loss of efficiency to be associated with components of G7 (called other) boiler as listed.

The system identifies that the efficiency drop is due to components of G7 boiler underperforming. EXERGY recommends to change the drum pressure to a certain level which can at least in principle, carried out by operator(s) . Refer to plant schematics in the appendix to see the cross-sections. If this recommendation is followed through then the efficiency will be at least partially restored. Had this been done at the time a much greater loss 10 minutes later could be avoided. See next screenshot below.

EXERGY coloane power station 4

The associated trend is shown below.

EXERGY coloane power station 5

In this example, which is in fact the previous one 10 minutes later, note the general deterioration of the efficiency of unit 8, ( G8 engine, G7 exh. boiler, and the steam turbine) continues. Here too the cost is in 2004 prices of oil, i.e. at about 4000. MOP/Hour in 2007 oil prices. Efficiency is indicated by the blue line at the top beginning at time 08:23, and ending at 11:23. The root cause is the same as in fig.2
The recommendation is not repeated this time around. In general operators may know of also indirect remedies, or otherwise inform management.

Long term condition monitoring

Besides alarming efficiency excursions, EXERGY data can also be used to monitor the long term condition of plant components. This is useful for making maintenance decisions. Below is an example of such a use.

EXERGY coloane power station 6

In this example the effect of air-coolers replacement is demonstrated. The efficiency of the 4 coolers as a group (black line tagged 04910.EF) is shown to increase between May 4 2003 and January 2 2004 from about 19% to 27% whilst the benchmark shown as the dotted line of the same colour is about 38% (in between this time data did not survive; the gap is closed by the graphics to focus on the relevant detail)

Similar increases is shown for the other coolers (except for air-cooler 3 where the efficiency appears negative, indicating probe(s) break-down). Note that for air-coolers 1,2,4 the efficiencies are restored to nearly the benchmark(s) when replaced. The efficiencies tapper off a bit later in April 2004 (here too the time-gap is suppressed) showing the deprecation from new condition.

APPENDIX

All of the code used in this demo, assumed that Coloane has a configuration as drawn below:

EXERGY coloane power station 7
EXERGY coloane power station 8

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