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By James Piper, P.E.
Power & Communication Article Use Policy
While allocating costs to users is one of the driving forces behind the use of submeters, it also gives managers opportunities to curtail energy costs. Managing energy use requires that managers first understand the location and timing of its use. Submetering gives managers that information.
For example, managers can have submeters installed on systems and individual pieces of equipment, such as chillers, air handlers, and pumps. Over time, the meters will gather data managers can use to create energy-use profiles for those systems and pieces of equipment.
By monitoring performance, managers can detect any deviation, which could result from a change in occupancy, user requirements, or something related to the equipment itself, such as the fouling of heat-transfer surfaces. Early detection of these changes allows managers to take corrective action before problems develop into large energy losses or equipment failures.
Submetering mechanical equipment also allows managers to compare operating efficiency. For example, if a facility's central plant has two centrifugal chillers, developing energy load profiles for each chiller provides a basis to compare their operating efficiencies. While slight differences are normal, larger differences can indicate improper operation in the less efficient chiller.
Submetering individual pieces of equipment also can lead to more cost-effective use of electricity. Commercial and educational facilities often have particularly large electrical loads associated with the operation of one piece of equipment, equipment that is not operated for long periods of time. Submetering can show the impact a particular piece of equipment has on the facility's overall electrical demand.
And because demand charges are a significant portion of the monthly electrical bill in many applications, operating that equipment during periods of peak demand can have a large impact on the facility's electrical bill.
Moving the load to off-peak hours can save tenants, departments, and managers considerable charges.
Load shifting offers managers another advantage. By reducing a facility's peak demand — particularly if it coincides with the peak-demand period for the local utility — the facility might qualify for a lower rate structure.
For health care, educational, and commercial facilities, all that might be required is to have departments and tenants schedule their energy-intensive operations for off-peak periods.
Yet another benefit of submetering technology is that it helps managers focus their attention on the large targets. Energy-conservation opportunities exist in most facilities, particularly large ones. But managers have limited resources, both in personnel to implement changes and in funding to cover the costs of the changes.
To get the biggest return for their investment, managers must start with the big-ticket items, those with the highest energy-use levels or that offer the largest potential for improvement. Without data quantifying the amount of energy being used in the facility, managers will have to guess which opportunities offer the greatest potential.
While the largest energy users within a facility, such as chillers, will be obvious, the room for improvement that is available in those systems might not be as obvious.Identifying those opportunities requires benchmarking the current system against system norms, and benchmarking performance requires data that submeters provide.
Submetering: Taking Control of Power
Submetering Helps Managers Identify Savings Opportunities
Verifying Accomplishments Tough in Energy-Conservation Programs
Sidebar: Picking Candidates for Submetering