Solar Electric System for Housing Society
Residential Solar Electricity
Solar Electricity is an excellent solution for Housing Societies & Residences to reduce the Electricity bill by as much as 80-90%. As most people are not well versed with the Technology, there is a fear factor inhibiting the execution of this choice. In our Society, I have successfully executed a 46kW Solar Electricity Project, resulting in a monthly savings of over Rs. 70,000/- in our Electricity bill.
With the new Policies of the Government, the Rooftop Solar Electric System of a Residential Premises can be connected to the Main Grid of the Electricity company thereby reducing the costs associated with Installation & Maintenance of Batteries, which was needed in earlier days. Such a Solar System connected to the Main Electricity Grid is called “Grid-Tied Rooftop Solar System”
The main components of a Grid-Tied Solar System are shown below:
Working of a Grid-tied Solar system in brief:
- Solar panels convert the sun’s energy into DC electricity
- The DC electricity is channelized into a solar inverter that converts it to 240V 50Hz AC electricity.
- The 240V AC electricity can be used to power home appliances
- Surplus electricity is fed back into the main grid.
We will now understand different components of the Solar System.
Solar Panels
Solar Panels operate on the Photo-Voltaic (PV) Principles and hence are called Solar PV Panels. Solar Panels convert Ultra-Violet (UV) radiation in the sunlight into Direct-Current (DC) Voltage and hence can develop electricity in cloudy conditions too, although at a reduced efficiency.
Solar Panels need to be installed facing south side to avail maximum sunlight through all the seasons (as India is located in the Northern Hemisphere).
While there are many Manufacturers of Solar Panels, they can be broadly segmented into “Made in India” and “Imported”.
Although, it is mandatory to use Indian Panels to avail Government Subsidy, the decision (for Indian or Imported panels) should be based on the Final Cost per kW after considering various cost heads.
Inverters
While Solar Panels develop Direct-Current (DC) Voltage, as we require Alternating-Current (AC) Voltage in our houses. The Conversion from DC to AC is done in an Inverter.
A Pure sine wave inverter is the best suited Inverter for Grid-Tie applications. There are many international & local Brands of Inverters.
Most of the good quality Inverters and Solar Systems are integrated with Web based Performance Monitoring which allows real-time tracking of System Parameters and quick reporting/ diagnosis of system faults, displayed on the Smartphones of assigned users.
Metering Of The Power
A typical Solar System uses two types of metering of the electrical energy – Net and Gross Metering.
Net Metering
When the sun shines, solar electricity generated by your solar panels is used by the appliances in your home. This means your home will be importing less electricity from the grid as your home’s appliances consume electricity directly from the solar panels.
If you don’t have enough solar electricity to power your appliances, the balance required to power up your home is imported from the grid. Thus, the Net Meter provides the difference between the Electricity used from the Grid vs. that generated by your Solar panels.
Gross Metering
The handy thing about gross metering is that your electricity bill tells you exactly how much electricity your solar system has generated avoiding the ambiguity of the net metering approach.
Gross metering also records the entire amount of electricity that is consumed by your home.
Circuit Breakers, Switch Boards & Power Cables
As the Solar system comprises of DC Circuit and AC Circuit, it is essential to provide suitable Protection devices for each circuit. It is very important to protect Solar panels with DC circuit breakers due to their high cost. Similarly, AC Circuit breakers are essential to protect the appliances and system components.
For DC Circuit, it is essential to use Copper conductor cables. For the AC Circuit, 4-core armored Alu. conductor cables can be used. The size of these Cables will depend upon the Power transferred and system load.
Earthing & Lightening Arrester
When installing a solar Photo-voltaic system (PV), it is extremely important that all the equipment is grounded correctly. Therefore, providing dedicated Earth pits and strong earthing connections is very vital.
As most of the Residential Projects do not have adequate protection from Lightening, it becomes essential to Install adequately large sized Lightening Arrester capable of covering the whole area of the Solar system Panels layout.
Key Steps During Execution Of A Solar System Project In A Housing Society
- Check if the building has sufficient Open space facing South direction viz, Terraces, Rooftop, Floor above Water Tanks & Lift shafts, etc. to suffice for the Solar Panel Installation. Some Key info about panels is as under
- Space required = approx. 100 Sq. ft. per kW
- Standard Panel size = 2 mtrs x 1 mtr.
- Power Production (average) = 120 units/kW/month
- Output capacity = 315-320Wp per Panel
- All the Electrical appliances in Common use (like Lights, Water Pumps, Water Heaters, Lifts, etc.) of the Society can be operated on this Solar PV Electric system
- Analyse Project feasibility
- Consider 80%-90% of the Sanctioned Load (or of your Average Monthly usage) as the Capacity of the Solar System
- Cost of the Solar System will vary between Rs. 55,000/- per kW to Rs. 85,000/- per kW depending upon the size of the system
- As the Life of the Solar system is between 20 to 25 years, the savings accrued after the break-even will be profits for the Society and can reflect in huge savings in the Maintenance Charges for each member
- Present the Project Calculations to the Society members, detailing the monthly savings in Electricity bill, its reflection on individual Maintenance Charges, increased benefits with inflation on Electricity Tariffs, total Investment needed and possible sources to raise the Capital.
- For the Project execution, constitute Project Team comprising of members with diverse expertise i.e. Engineering, Management, Civil, Structural, Legal
Author, Mr. Devdutta Chandavarkar can be contacted freely at ‘chandavar@gmail.com’ for any clarification or more detailed information.