Page 93 - Alternative Energy Systems in Building Design

SOLAR POWER SYSTEM DESIGN 69

Installation In contrast to standard roof tiling, MegaSlate elements are preferably
laid from top to bottom. Before being secured into the brackets, they are connected
with touch-safe electrical connectors. An appropriate functioning check is required
before operating the system.
After the cables are connected to the terminal box on the dc side and to the inverter
on the ac side, electricity produced by the building can be fed into the grid.
In the event of malfunction, the MegaSlate PV elements are easy to replace or
exchange. The MegaSlate roof-mount installations are also walkable. However, it is
recommended that system maintenance be undertaken by qualified personnel.

Solar Power System Design

This section is intended to acquaint readers with the basic design concepts of solar
power applications. The typical solar power applications that will be reviewed include
stand-alone systems with battery backup, commonly used in remote telemetry;
vehicle charging stations; communication repeater stations; and numerous installa-
tions where the installation cost of regular electrical service becomes prohibitive. An
extended design application of stand-alone systems also includes the integration of an
emergency power generation system.
Grid-connected solar power systems, which form a large majority of residential and
industrial applications, are reviewed in detail. To familiarize readers with the prevailing
state and federal assistance rebate programs, a special section is devoted to reviewing
the salient aspects of existing rebates.
Solar power design essentially consists of electronics and power systems engineering,
which requires a thorough understanding of the electrical engineering disciplines and
the prevailing standards outlined in Article 690 of the National Electrical Code (NEC).
The solar power design presented, in addition to reviewing the various electrical design
methodologies, provides detailed insights into PV modules, inverters, charge controllers,
lightning protection, power storage, battery sizing, and critical wiring requirements. To
assist readers with the economic issues of solar power cogeneration, a detailed analysis
of a typical project, including system planning, PV power system cogeneration estimates,
economic cost projections, and payback analysis, is presented later in this chapter.

SOLAR POWER SYSTEM COMPONENTS AND MATERIALS
As described below under “Ground-Mount PV Module Installation and Support
Hardware,” solar power PV modules are constructed from a series of cross-welded solar
cells, each typically producing a specific wattage with an output of 0.5 V. Effectively,
each solar cell could be considered as a 0.5-V battery that produces current under
adequate solar ray conditions. To obtain a desired voltage output from a PV panel
assembly, the cells, similar to batteries, are connected in series. For instance, to obtain a
12-V output, 24 cell modules in an assembly are connected in tandem. Likewise, for a
24-V output, 48 modules in an assembly are connected in series. To obtain a desired
wattage, a group of several series-connected solar cells is connected in parallel.