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