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Synchronizing on West Point
Could local generators be used either to regulate voltage or control the power factor on distribution systems in New York?
kilowatt savings in cable and transformer heating from using adjustable speed drives to correct power factor was estimated above to be 15 kW. Over a one-year period this is 131 MWh. Using the conversion factor of 11,850 BTU/ kWh, this converts to 1,557,000 source BTU savings.
This is a meaningful level of source BTU savings, especially if it can be repeated at other commercial and industrial installations. Supplying reactive power from ASDs will provide an important service to distribution and transmission operators. The power factor of the load could be kept at 1.0, or even leading when needed. This will result in greater distribution and transmission system efficiency and reliability.
The results may be common to a wide range of industrial, commercial, and even residential distribution systems. The ASDs could be controlled easily to provide leading power factor when needed. A meter is available that measures power factor at the load and reports the power factor to the utility using a built-in cell phone. The meter also can transmit a local radio signal to the ASDs. The utility could thus request that power factor go leading when they are dealing with a system under stress and have inadequate reactive reserves.
Power Factor Correction Credit
There is yet another possibility that we should consider. Alliant Energy provides a power-factor credit to customers that can correct power factor to 0.95 or higher. Although Alliant is in Wisconsin and West Point is in New York, consider the hypothetical case of using the Alliant credit at West Point. This is a reasonable situation to consider as this sort of credit hopefully will become common across the nation.
We will assume an average West Point peak load of 14.5 MW. Alliant’s demand charge is about $10 per on-peak kilowatt per month. If West Point could correct their power factor from .9 to 1.0, Alliant would credit West Point ($10 x 14,500 x .1), or $14,500 per month. The annual credit would be about $174,000.
Inverters are used in both microturbines and adjustable speed drives. Inverters with active front ends can be used to control power factor. Next generation microturbines will have this capability. If microturbines could be used at West Point in a combined heat and power application, they could have an especially fast payback because of this power factor added credit. West Point already has a demonstrated need for the waste heat from the turbines. They use boilers to heat water for campus use. Microturbines or small turbines would be ideal to provide heat and real power from the turbine and reactive power from the microturbine’s inverter.
The savings to the system owners as well as to distribution system operators, who could control the inverters to provide leading power factor when needed, would be truly significant. Presenting a net power factor of near 1.0 is becoming increasingly important as the nation’s bulk power system is under more and more stress, and inverter-based distributed energy resources are a readily available and highly efficient method to accomplish this.
1. Reactive Power for Planning and Operation, Harrison