Get your basic Solar FAQs cleared here. The following are the initial questions asked frequently by persons interested in solar.
The sun is source of infinite energy and the energy produced by sun is called Solar Energy. The amount of solar energy reaching the surface of earth is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth’s non-renewable sources of coal, oil, natural gas and mined uranium combined. But most of this free and clean solar energy goes waste in the atmosphere. But with viable technology now available, this energy from sun can be directly converted to electricity by the use of solar Photo-Voltaic (PV) cells. A large no. of cells are arranged together to form a Solar panel. When sunlight falls on these solar panels, it gets converted to electricity and this electricity produced from the sunlight is called Solar Power. The complete system generating the solar energy is called Solar system.
Solar modules convert the sunlight into DC electricity and in specifications which are not suitable for direct use. Additional components are required to convert, condition and monitor the electricity produced so that it may be utilized by common appliances used in homes and offices or may be feed into the grid. This combination of solar panels, inverters, Junction boxes, wires, transformers and other components which finally deliver useful electricity is called a Solar Photo-voltaic (PV) System or a Solar PV Power Plant. The size of a solar power plant can be very small (1 kW or less) which can be easily mounted on home rooftop to thousands of MW (covering huge amount of land).
There are three types of PV plants:
- Grid connected systems
- Off-grid systems
- Hybrid Systems
Grid connected PV systems, as the name suggests, are connected to the electric utility grid. The ground mounted power Grid connected plants have size usually greater than 1 MW and feed electricity into the grid. The roof mounted grid connected plants have sizes from 1 kW onwards but are mostly less than 250 kW and are usually for captive (self) consumption. There is no electricity storage (battery) with these systems and therefore these can provide electricity only in the daytime. One drawback of this system is that it does not provide the electricity when the grid is down and works only when there is supply from the grid. It reduces the load on the grid by as much power as it is generating. It means they are suitable only for areas which have less number of day time blackouts.
Off-grid PV systems provide electricity even during the night as they have dedicated battery banks which get charged during the day and the stored electricity can be used during the night. These systems are not connected to grid and are usually very small in size (less than 50 kW). The large battery banks is the drawback of these systems as they are costly and have to be maintained properly and regularly.
These systems are connected to the grid but also have a small battery storage or DG set to work with, so that the system can produce power in no-grid conditions. This system brings the best of above two as it is capable of feeding the extra power to the grid as well as provides power when the grid is down within manageable costs.
Various parts of a solar system are:
- Solar photo-voltaic panels
- MPPT inverters
- Solar charge controllers
- Distribution boxes
- Mounting Structures
- Protection & Controls
- Remote Monitoring System
Solar PV panels convert the sunlight directly into DC electricity. The panels are rated according to their peak wattage. Note that a 200 watt peak solar panel does not produce 200 watt power when kept in sun but less than 80% of the 200 W depending on the time of day and angle of panel with the sun. Three types of panels are available in the market, Mono-crystalline, Poly-crystalline and thin film type in decreasing order of efficiency. Higher efficiency modules require lesser space for installation. Various Indian and foreign panels manufactures are present in the market providing panels with different peak wattages. The best available panels have efficiency around 15 – 18%.
The DC electricity produced by the solar panels is converted to AC by solar inverters. Solar inverters are different from common inverters as they have Maximum Power Point Tracking (MPPT) technology to increase the efficiency of the solar panels. This inverter automatically synchronizes its AC output to the exact AC voltage and frequency of the grid. The efficiency of good quality inverters is greater than 94%.
One kW of Solar panels requires shadow-free roof space of 100-120 square feet if Crystalline PV panels are used and around 150-175 square feet if Thin-Film panels are used. This is only a rough benchmark and may vary based on type and efficiency of panels, and style of installation.
For solar panels, a flat or south facing roof is required. The type of your roof and its load bearing capacity can affect the size of solar system which can be installed and the type of mounting structures needed. Concrete roof and Metal roof can accommodate panels directly or with some special structures but in case of asbestos roof, it is very critical to check the load bearing capacity and mounting feasibility.
The usual benchmark for energy generated from a 1 kW Solar system is considered as 1,500 units per year. This is a conservative benchmark and actual generation is different for different locations. The amount of actual energy generated from a Solar Power system in a year depends on both internal and external factors. External factors which are beyond the control of a solar installer include the following:
- Number of sunny days
- Solar Irradiation
- Day Temperatures
- Air Mass
The output also depends on the following internal factors all of which are within the control of a solar installer: