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Types of Solar Rooftop Power Systems
A typical rooftop solar power system has electricity-generating photovoltaic panels, commonly known as solar panels, on top of a house or building. But there is much more to it…
On-Grid System or Grid-tied System
Grid synchronous systems are designed to work in conjunction with the grid. The valuation of generated electricity is done via a net-meter.
Major components: Solar panels, Inverter, mounting structure, cables
When photons fall on solar panels they produce DC. That DC power is converted into AC power with the help of inverter, and it is then accessible for use. The grid tie inverter (GTI) is designed in such a way to synchronize its frequency with that of the grid (e.g. 50
or 60 Hz) using a local oscillator and limit the voltage to no higher than the grid voltage. A high-quality modern GTI has a fixed unity power factor, which means its output voltage and current are perfectly lined up, and its phase angle is within 1 degree of the AC power grid. The inverter has an on-board computer which senses the current AC grid waveform, and output a voltage to correspond with the grid. However, supplying reactive power to the grid might be necessary to keep the voltage in the local grid inside allowed limitations. Otherwise, in a grid segment with considerable power from renewable sources, voltage levels might rise too much at times of high production, i.e. around noon.
The electricity generated using the solar system is fed back to the grid. A net meter is installed alongside this system to monitor the export and import of electricity through grid resulting in savings which get reflected in the bill.
The excess power going into the grid turns your meter backwards, if more power is utilized than your system is producing, inverter will automatically pull the needed power from the utility grid. This back and forth process is called “net metering”, and it means you are only billed for the “net” electricity purchased over the entire billing period. If you produce more than you use during a billing period, utility company shall retain it as a credit, which will then be applied to future electric bills.
Off grid solar roof top systems
An off-grid system is not connected to the grid and requires battery storage. These systems store the electricity generated in batteries and utilize the stored energy by converting it back to AC when required. The rising cost of other power sources and the increasing demand for electricity, especially in remote areas that are from grid or high power cut or no grid areas, has resulted in an increased demand for such systems. The decrease in battery costs over the years has further brought the system cost down, so there is now a growing market for off-grid solar battery systems even in cities and towns.
Hybrid solar roof top systems
Modern hybrid systems combine solar and battery storage in one and are now available in many in a wide range of designs. Due to the decreasing cost of battery storage, systems that are already connected to the electricity grid can start taking advantage of battery storage as well. This means being able to store solar energy that is generated during the day and using it at night. When the stored energy is depleted, the grid is there as a backup. Hybrid systems are also able to charge the batteries using shabby off-peak electricity (usually after 12pm to 6am).
Different functions of a solar inverter
Conversion: The basic function of the inverter is to convert the variable DC output of the solar panels into AC.
Power maximization: Solar panels have a “Maximum Power Point”, a performance curve where they produce the most power. Inverters are equipped with Maximum Power Point Trackers (MPPT) which continually look for this and maximize the energy available from the solar array.
Regulation – As sunshine, solar output and grid conditions vary, an inverter will regulate and synchronies all these variables so the power quality is within specification and power harvest is maximized.
Monitoring – Inverters also measure and display information, so that one can check that system is performing as expected or diagnose faults if they occur.
According to Ministry of New and Renewable Energy (MNRE) Notification dated March 4, 2016 and September 2, 2016 only Residential, Institutional and Social Sectors are eligible to avail Central Financial Assistance CFA). Central Financial Assistance (CFA) of 30 % of the bench mark cost or as applicable from time to time is provided for 1 KWp upto 500KWp Grid Connected Solar Power Plants to institutional(Hospitals ,Schools etc ) /Social Sector (irrespective of the electricity connection) for installing Grid Connected Rooftop Solar PV Power Plants.