1 Government regulations and policies
MNRE has several incentives, including subsidies and rebates, for the installation of solar rooftop systems. In addition, some state governments have additional benefits for those installing solar systems. Contact your local vendor for more information.
2 Location of the PV array
In most urban areas, the array is located on the roof of a building. For both flat and pitched roofs, ensuring there is sufficient roof area and safe access is a must for any solar array installation.
3 Roof specifications
The energy output of solar panels is affected by two major factors: orientation and tilt. As the roof affects panel positioning, it should be assessed in advance for both factors.
- Orientation
This is the direction in which the roof is facing. For maximum energy yield, solar modules should face south in India.
- Tilt angle
This is the inclination angle of the roof. The optimum tilt angle is equal to the latitude angle of the location. In India this varies between 10° and 30°. For flat roofs, special pre-fabricated mounting structures are used to tilt the modules at the required angle.
Other factors to consider include:- Roofing material
The mounting structure used for installing PV modules depends on the type of roofing material, such as concrete cemented or tiles. Also, it is important to note whether drilling is permitted on the roof or not.
- Roof age
It is important to ascertain that the roof will be stable enough to sustain the weight of the solar system, and age is a major contributing factor to structural integrity.
4 Is the roof shade-free?
Shading on the PV array can significantly decrease its output. Any permanent source of shading needs to be identified during the initial planning stages. Potential sources of shading include:
- Trees and vegetation.
- Exposed columns and beams.
- Other buildings.
- Components of a building, such as overhead tanks, poles, pipes and dish antennas.
- The natural landscape in hilly areas
5 Available area
A major design constraint on the system is how many modules can physically fit into the shade-free location identified. Calculate the available area for installation by:
- Measuring the maximum available roof space after shadow analysis.
- Determining the edge zone (the required amount of space between the array and the roof edge) and subtracting this from the maximum roof space.
Once the available area has been determined, you must determine the maximum number of modules that can fit in it (which depends on the size of the modules you will be using). You should check both portrait and landscape orientations of the panels for optimisation.As a rule of thumb, 6–10 m2 of effective roof area is required for 1 kWP solar system.
6 Energy efficiency initiatives
Before installing a solar system, it is important to implement energy efficiency measures, such as:
- Turning off electrical appliances when not in use.
- Using energy-efficient appliances with higher star ratings.
- Using energy-efficient CFL and LED lighting, and reducing the use of halogen down lighting.
- Insulating the walls, roof and flooring, and double-glazing the windows.
- Using programmable timers and temperature controllers when using air conditioners or heaters.
- Using desert coolers during dry summer months (as they consume less energy than air conditioners).
- Using a solar water heater or gas heaters for space and water heating.
7 Locating balance of system equipment
The solar PV array will be combined with several other components, such as inverters, junction boxes, combiner boxes, meters and batteries. Sufficient space should be available for the installation and maintenance of these supplementary devices.
8 Health, safety and environmental risks
Installing a solar system can be a risky job in places with constrained roof access. Some of the risks are:
- Working at heights.
- Manual handling of heavy objects.
- Working with DC electricity sources.
For more details, read GSES ‘Grid Connected PV Systems: Design and Installation’ training manual.
Adapted from: GSES ‘Grid Connected PV Systems: Design and Installation’ training manual.