Introduction

 As the demand for solar electric systems grows, progressive builders are adding solar photovoltaics (PV) as an option for their customers. This overview of solar photovoltaic systems will give the builder a basic understanding of: 

  • Evaluating a building site for its solar potential 
  • Common grid-connected PV system configurations and components 
  • Considerations in selecting components 
  • Considerations in design and installation of a PV system 
  • Typical costs and the labor required to install a PV system 

System Components

Pre-engineered photovoltaic systems can be purchased that come with all the components you will need, right down to the nuts and bolts. Any good dealer can size and specify systems for you, given a description of your site and needs. Nevertheless, familiarity with system components, the different types that are available, and criteria for making a selection is important.

 Basic components of grid-connected PV systems with and without batteries are:

  • Solar photovoltaic modules 
  • Array mounting racks
  • Grounding equipment 
  • Combiner box 
  • Surge protection (often part of the combiner box) 
  • Inverter 
  • Meters – system meter and kilowatt-hour meter 
  • Disconnects: – Array DC disconnect – Inverter DC disconnect – Inverter AC disconnect – Exterior AC disconnect If the system includes batteries, it will also require: 
  • Battery bank with cabling and housing structure 
  • Charge controller 
  • Battery disconnect

Evaluating a Site for Solar PV Potential 

Evaluating a Building Site – While INDIA may have good to excellent solar potential, not every building site will be suitable for a solar installation. The first step in the design of a photovoltaic system is determining if the site you are considering has good solar potential. Some questions you should ask are: 

  • Is the installation site free from shading by nearby trees, buildings or other obstructions? 
  • Can the PV system be oriented for good performance? 
  • Does the roof or property have enough area to accommodate the solar array?
  • If the array will be roof-mounted, what kind of roof is it and what is its condition? 

Mounting Location – Solar modules are usually mounted on roofs. If roof area is not available, PV modules can be pole-mounted, ground-mounted, wall-mounted or installed as part of a shade structure 

Shading – Photovoltaic arrays are adversely affected by shading. A well-designed PV system needs clear and unobstructed access to the sun’s rays from about 9 a.m. to 3 p.m., throughout the year. Even small shadows, such as the shadow of a single branch of a leafless tree can significantly reduce the power output of a solar module. Shading from the building itself – due to vents, attic fans, skylights, gables or overhangs – must also be avoided. Keep in mind that an area may be unshaded during one part of the day, but shaded at another part of the day. Also, a site that is unshaded in the summer may be shaded in the winter due to longer winter shadows. 

Tilt – Generally the optimum tilt of a PV array about 18 degrees to achieve yearly maximum output of power. An increased tilt favors power output in the winter and a decreased tilt favors output in the summer.

Required Area – Residential and small commercial systems require as little as 50 square feet for a small system up to as much as 1,000 square feet. As a general rule for the Pacific Northwest, every 1,000 watts of PV modules requires 100 square feet of collector area for modules using crystalline silicon (currently the most common PV cell type).