ASHRAE Journal - October 2019 - 32

TECHNICAL FEATURE

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12a 1a 2a 3a 4a 5a 6a 7a 8a 9a 10a 11a12p 1p 2p 3p 4p 5p 6p 7p 8p 9p 10p11p

would overestimate the consumption. Figure 5 shows the
energy consumption (kWh) multiplier developed so a
typical hourly consumption from the released 0.71 MW
at the substation could be obtained, as follows:
For hour i = 1 to 24:
Energy Consumption Multiplieri
=

TLS Hourly Demand (kWi )
TLS Maximum Demand ( kW )

Annual Energy Consumption Released
24

= ∑Preleased × Energy Consumption Multiplieri ×
i =1

365 = 5,161 MWh

Figure 6 shows the substation typical hourly electricity consumption available from the released 0.71 MW,
resulting in a total of 5,161 MWh annually.
With the blended rate of $0.07/kWh the college is paying for its electricity consumption, the system-released
consumption as a result of the power factor correction
would be worth $361,286, which represents the avoided
cost of electricity savings (electricity that otherwise
would have to be either purchased or generated on site).
With the $3.14/kW demand monthly charge, the annual
savings will be reduced by $26,753 (12 × $2,229), resulting in a net annual savings of $334,533. With an average
of $500,000 monthly electricity bill, the $2,229 monthly
demand charge is minimal.
Typical PFC equipment manufacturers show installed
cost of various types of correction from fixed capacitors at
$15/kVAR to active harmonic filters ranging at $150/kVAR.
Active harmonic filter types of PFC are mainly
32

FIGURE 6 Typical load shape of the potential system released electric consumption
from the substation over a year period.

kWh (in Thousands)

kWh Multiplier

FIGURE 5 Typical load shape of the Fiscal Year 2016 electricity demand at the
substation subject to this study.

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designed for the service entrance of the facility where
the overall harmonics from the facility and the potential
harmonics from the utility power lines may be present.
Capacitors offer a low-impedance path to harmonic
frequencies and, therefore, can attract harmonics, often
resulting in reduced life, fuse blowing, or capacitors failure.1 Active harmonic filters were chosen for the study,
instead of capacitors, to address the fact that non-linear
loads (for instance, switched-mode power supply equipment, fluorescent lighting, variable frequency drives,
among others) are a substantial part of the campus
electric load. With an installed cost of $150/kVAR (which
happens to be the most expensive option) for an active
harmonic filter type of PFC system, the PFC would cost
$433,119. With supervision, inspection and overhead
(SIOH) cost and design cost (5.7% and 4% respectively),3
the cost grows to $475,132, resulting in a simple payback
period of 1.42 years (17 months). Any other type of PFC,
if warranted for a given and specific case at hand, would
result in a much shorter payback period.
The calculated PFC size is 2,887 kVAR. It is rarely possible
to find the exact calculated PFC size. It is left for the design
team to decide whether to select the immediately larger or
the immediately smaller size, depending on the existing
circuit configuration and the desired power factor. The PFC
equipment selection for this study resulted in a bank of two
1,500 kVAR active harmonics filters (3,000 kVAR total),
typically mounted in a steel enclosure and usually located
within a fenced-in substation or a switchgear room.

Conclusions
Power factor correction (active harmonic filters in this
case study) were proposed to enhance and improve the
energy performance for a college facility in New York,
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ASHRAE Journal - October 2019

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