Page 163 - Alternative Energy Systems in Building Design

ECONOMICS OF SOLAR POWER SYSTEMS 139

In July 2006, Shell Solar Industries and its projects and technology, including the
Semitropic project and single-axis tracking technology, were purchased by SolarWorld
Industries. Installation of a comparable system with SolarWorld’s currently more efficient
modules would require 6576 SW-175 modules = 1150.8 kW. The modules could be
assembled into 1096 prewired panels. The basic elements of the single-axis tracking
system design and array would remain the same, but owing to reduced solar module
surface area, the system would require approximately 9 percent less space.

Economics of Solar Power Systems

Perhaps the most important task of a solar power engineer is to conduct preliminary
engineering and financial feasibility studies, which are necessary for establishing an
actual project design. The essence of the feasibility study is to evaluate and estimate
the power generation and cost of installation for the life span of the project. The
feasibility study is conducted as a first step in determining the limitations of the solar
project’s power production and ROI without expending a substantial amount of engi-
neering and labor effort. The steps needed to conduct a preliminary engineering and
financial study are presented in this section.

PRELIMINARY ENGINEERING DESIGN
Conduct a field survey of the existing roof or mounting area. For new projects, review
the available roof-mount area and mounting landscape. Care must be taken to ensure
that there are no mechanical, construction, or natural structures that could cast a shad-
ow on the solar panels. Shade from trees and sap drops could create an unwanted loss
of energy production. One of the solar PV modules in a chain, when shaded, could act
as a resistive element that could alter the current and voltage output of the whole array.
Always consult with the architect to ensure that the installation of solar panels will
not interfere with roof-mounted solar windows, vents, and air-conditioning unit duct-
work. The architect also must take into consideration roof penetrations, installed
weight, anchoring, and seismic requirements.
On establishment of solar power area clearances, the solar power designer must pre-
pare a set of electronic templates representing standard array configurations. Solar
array templates then can be used to establish a desirable output of dc power. It should
be noted that when laying blocks of PV arrays, consideration must be given to the
desirable tilt inclination to avoid cross-shadowing. In some instances, the designer
also must consider trading solar power output efficiency to maximize the power out-
put production. As mentioned earlier in this chapter, the most desirable mounting posi-
tion for a PV module to realize maximum solar insolation is about latitude −10 degrees.
For example, the optimal tilt angle in New York will be 39 degrees, whereas in Los
Angeles, it will be about 25–27 degrees. To avoid cross-shading, the adjacent profiles
of two solar rows of arrays could be determined by simple trigonometry. This could
determine the geometry of the tilt by the angle of the associated sine (shading height)
and cosine (tandem array separation space) of the support structure incline. It should