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An EPRI White Paper

DC Power Production, Delivery and Utilization

A PV-DC case study, distribution warehouse, Rochester, NewYork, continued

Figure 16. SensorSwitch daylight, occupancy sensors

A number of factors contribute to the value of this system:

  • Using the electricity generated by the solar panels to power the lighting eliminated significant inverter losses and improved efficiency by as much as 20%.

  • The low-voltage control capability of the DC ballasts enabled the control system to be installed easily, with- out additional AC wiring.

  • Roof-integrated solar panels reduced installation costs and allow the cost of the roof to be recovered using a 5-year accelerated depreciation formula.

Figure 17 illustrates the energy savings due to the daylighting and occupancy controls.

Figure 17. Performance of occupancy and daylight sensors

Frito-Lay Rochester Green DC lighting load shedding with daylighting & occupancy control

kWatts 35

Irradiance ( /m^2) or temperature °F 1,000

30

25

20

15

10

5

-

Automatic 33% and 66% load reduction

900 800 700 600 500 400 300 200 100 -

Actual DC lighting load with load shedding Lighting load without load shedding Daylight levels

0:00

6:00

12:00

18:00

0:00

The red line shows the lighting profile of the building without load shedding. Most of the lighting comes on at 3:00 am. All lights are turned on from 6:00 am to 6:00 pm.The blue line shows the lighting load with the occupancy and daylight sensors controlling the lighting. Between March and mid-June 2005 between 20% and 30% savings were achieved due to the controls.

June 2006

Page 21

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