Page 224 - Solar Power in Building Design The Engineer's Complete Design Resource

194 LEED—LEADERSHIP IN ENERGY AND ENVIRONMENTAL DESIGN

Figure 7.7 Nextek dc solar power lighting.

The logic of the lighting system is designed for optimum efficiency. Sources of light
and power are prioritized as follows:

■ First, daylight from the skylights is used.
■ Second, if daylighting is not sufficient and the area is occupied, then power from
the solar panels is added.
■ Third, if daylight and solar power are not enough, then the additional power
required is taken from the grid.

A number of factors contribute to the value of this system:
■ Using the electricity generated by the solar panels to power the lighting eliminates
inverter losses and improves efficiency by as much as 20 percent.
■ The low-voltage control capability of the dc ballasts eliminates rectification losses
and enables the innovative control system to be installed easily. Figure 7.8 depicts
occupancy sensors efficiency chart

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