January 1997 Volume 3 Issue 1
Whole-Plant Energy Use Monitoring
As mentioned in Issue 21, having an energy audit of your facility gives you a clear picture of where your energy dollars are going and what might be done to eliminate wasted energy. Let’s assume that
· your firm had an energy audit,
· you implemented some changes, and
· the energy bills went down.
End of story?
Unfortunately not. It would be nice if a one-time audit and one-time retrofit action would solve the problem forever, but that’s not what happens. Here, as in other areas of life, order tends to gradually revert to disorder. Just as houses need to be repainted and cars need to be repaired, boilers get dirty, steam traps wear out, control settings get changed, and energy consumption once again starts to rise. What can we do about this? There is one simple answer: Monitor ongoing energy use.
SET UP AN ENERGY MONITORING PROCESS
It would be nice if the first of each month your plant manager received a fresh energy audit report detailing the energy status of the entire plant. That, unfortunately, is not practical. What is practical is to collect and review each month a few energy-related numbers — numbers that tell you either “all is well,” or “there appears to be an energy efficiency problem.”
Existing accounting and production systems are rarely set up to collect energy data and do energy analysis, so a new system is usually needed. There is no one universal or “best” way to perform the task, but since you do not need a great deal of information, making the necessary arrangements is usually straightforward. The suggested steps are:
1. Make someone responsible for energy monitoring.
Who in your organization monitors production costs? It often makes sense for this person to add energy to the list of monitored costs, and to assume responsibility for watching energy expenditures.
2. Decide what data to record and what supplemental figures to calculate. Typical collected data includes:
· The kVA demand and kWh consumption figures from monthly electric bills
· Heating fuel (oil and/or propane) delivery dates and amounts
· Daily production figures, including quantity produced, number and length of shifts, etc.
· If production goes on all year, and if a substantial amount of fuel or electricity is used just to heat the facility in winter or cool it in summer, degree-day weather data will also be needed.
Plant energy consumption varies from month to month. If electricity or fuel consumption went up last month, does that mean a problem exists? Or did the increase simply reflect changes in plant operation and/or weather? To know, you need to make a few supplemental calculations. By introducing production and weather data in appropriate ways, it is possible to adjust the plant’s energy use figures for the effect of these two variables. Doing this helps make clear whether an increase in the electricity or oil bill was to be expected, or is a problem that needs to be investigated.
The “Basic Energy Accounting” section of the
new Windows-based $mart Energy Suite software accepts a year of fuel, production, and weather data and calculates average production and weather coefficients. These coefficients can then be used to help you decide whether a specific month’s data is about what it should be. The software is available free of charge from the Energy and Minerals Section. Call Mike Proud or Ron Estabrooks at 368-5010 (toll free).
3. Keep ongoing energy records, in either a notebook or a computer.
While raw data can be recorded in a notebook, and calculations can be done with pencil, paper and calculator, a computer program such as $mart Energy Suite can make the job easier. With this program you add new data month by month, and the program calculates monthly totals, and totals for the year to date. Summaries can be printed at any time, and when a whole year’s data has been entered, you can archive that file and start a new file for next year.
4. Alter the routing of electricity bills and fuel delivery slips.
In many companies, electricity bills and fuel delivery slips go straight to Accounting, and the production manager never gets to see the numbers. An alternate approach is to send all electric bills and fuel delivery slips first to the production manager — and then to Accounting.
5. Gather the data once a month, apply production and weather coefficients (as appropriate), and look for warning signs.
If energy use has gone up — and adjustments for production levels and weather don’t explain the rise — something is likely to be amiss. Finding it sooner will cost the firm less than finding it later!
USING THE UTILITY’S ELECTRIC METER
The electric company’s meter is there for your use as well as theirs. It can be helpful in your attempts to investigate mysteries such as a sudden, unexpected jump in the monthly demand charge. In the figure at the top of the next column, the long right-hand needle indicates the maximum (peak) demand so far this billing period. The needle to the left indicates the demand at the present time.
Some large plants also have their own meters that monitor demand and consumption, and many of these company-owned meters are capable of being connected to a computer. Such a connection allows hour-to-hour electrical consumption patterns to be monitored over long periods of time.
Accidentally turning a large load ON at the wrong time can significantly increase the peak demand. And if the plant is on an electric rate having a “ratchet clause,” this could boost monthly bills for a whole year. Demand monitoring, if done by a computer or other automatic means, is just a small step away from demand control. Demand control systems sound an alarm or shed non-critical loads when demand reaches a preset level.
METERING FUEL CONSUMPTION
Particularly if the plant has one fuel storage tank but several different uses for the fuel, it can be helpful to meter the amount of fuel that goes for each use. This can be done by installing fuel meters at the individual boilers or furnaces. A less expensive alternative, which works when burners have fixed firing rates, is simply to put a run time meter on each burner.
If you have questions about energy-use monitoring, or would like help in implementing a monitoring system, call Mike Proud or Ron Estabrooks at 368-5010 (toll free).