Frequently Asked Questions on Rooftop Solar. தமிழில் காண
There are two types of Solar Power Plants.
- On-Grid (without Batteries)
- Off-Grid AC (with Battery back-up)
- Off-Grid DC (Inverterless DC System)
On Grid System:
On Grid Solar Plants come without batteries.
The Solar Panels generate DC and an inverter converts that into usable AC form, and this out put is fed directly into the EB lines.
This type of Solar Plants can not be used as backup for EB.
Because, an On Grid System will not generate power when the EB power fails.
Unfortunately in Tamil Nadu On Grid system is on hold.. as the TNEB / TANGEDCO is planning to change the process of billing . Click here to read the relevant news article.
Government subsidy is available only for On Grid Systems. Not any more :=(
Off Grid System: AC
Off Grid Solar Power Plants come with Batteries. The Solar Power is converted into DC and is stored in Batteries. This stored power could be restored when there is a Power Cut. The DC Power from the battery is converted back into AC Power and used to operate the appliances.
Government Subsidy Scheme in Tamilnadu is not available for such systems.
Off Grid System: DC
This is a new technology getting popular because of the most efficient process.
In this system, the Solar Power is stored in the Batteries and retrieved to be used when there is no Sun Light or no Main Power supply.
This DC system does not involve multiple conversions and hence most efficient.This is the latest on Solar , designed by IIT-Madras and used to light up thousands of homes in Rajasthan and Bihar.
Click here to read more..
This is a valid question. Let us first see how an On Grid System works.
As in the above picture, we have solar panels on the roof, when sunlight falls on these panels, electricity is generated.
But this generated electricity is DC (Direct Current), whereas most of our equipments like Fan,light,Fridge,TV etc work on AC (Alternating Current).
So, to convert this DC to into AC an INVERTER is used.
The AC current from this INVERTER is fed directly on to the EB lines ,at the Meter Point.
It acts almost like a mini Power Station, that actually feeds our EB lines.
So, the Solar Power that is generated, should match the characteristics of the EB power.
If the EB voltage is at 200 Volts, Solar Power Output should also be 200 Volts.
If the EB frequency is 49.8 Hz, Solar Power output should also be exactly 49.8 Hz.
This is achieved by a process called synchronization on the INVERTER.
For this a small portion of the EB line is fed into the INVERTER, which checks at the Voltage/Frequency and uses that to produce the same Voltage and Frequency using Solar Power.
Now imagine what will happen when the EB power fails.
The inverted would not know if it has to Generate 200 V or 210 V at 50 Hz or 49.0 Hz.
So it switches itself off.
There is another important reason why an On Grid Plant goes off when EB power fails.
We know that every now and then the EB technical team needs to do maintenance on a Distribution transformer or other electrical parts on the line.
So they switch off the supply to the area and start their work.
During such time, if any of the On Grid Solar Power plant is generating the Power, the EB maintenance person would receive a huge shock.
Hence to ensure the safety of the EB personnel, the Solar Power that feeds into the EB lines need to be switched off whenever EB power fails.
Unfortunately the On Grid system is not available in Tamil Nadu until the FIT (Feed In Tariff) is decided by TNERC.
To read more about that click here.
Since On-Grid system does not require Batteries, we don’t have to do frequent maintenance/replace Batteries, and the cost would be considerably less.
Grid – Tied systems require the presence of EB power to make sure the power generated has the same characteristics (voltage / frequency etc) as the EB power.
The Generated Power would always be used, even if you do not switch on any light/Fan/TV. Because in an On-Grid system the Solar Generated Power is directly fed to the EB lines and you would be getting your electricity Bill reduced (using a Bi-directional Net Meter) to the extent of the power generated by the Solar Plant.
Hence when there is a power failure, the On Grid system stops working ,even though the sun is shining bright.The power generated by the solar Panel could not be used in this situation.
On-Grid system installation requires inspection/approval from the EB.
You need to apply, get the ‘Feasibility Report’ from the AE of your area and then install. After installation EB personnel would inspect, and allot a Net Meter , and only then the Solar Plant would become productive.
So this involves proper planning and some delay.
But this is a one- time trouble, and most of the Vendors providing the plant would help in this matter.
Since this type of system, needs batteries, they require frequent maintenance.
A good Battery has a limited life ( 3 to 5 Years).. and needs replacement.
This adds up to the cost of the system.
Unlike an On Grid system, an Off Grid system would supply power to only a specific set of equipments (like 2 fans, 5 Lights etc).
If these equipment are not being used during the day time, the Solar Power would only be used to charge the battery.
But Batteries have limited capacity (say 150 AH or 200 AH).
So once the batteries are fully charged, the remainder of the Solar Power goes waste.
So an Off grid system is not efficient or economical.
This type should be used only when EB power is not available at all even for a few hours a day.
If the requirement is only to provide back-up, we must use regular (non-solar) inverter/UPS with adequate Battery.
This will be more economical.
In an Off-Grid mode, the Solar Power plant does not require the presence of EB Power to operate. So during day-time, even if the EB power is cut, the Solar Plant will continue generating power.
Since Batteries are needed in Off-Grid mode, the cost of the plant is higher. Batteries need frequent maintenance / replacement.
This mode is suitable when EB power is un-reliable and there are frequent load-shedding /power failures for prolonged time.
Also in Off Grid mode the efficiency of the power plant is reduced. That means that though we have 1000 Watts Solar panels installed, we would not be able to extract the maximum, as we lose some power in the process of charging the batteries.
Also this mode would limit the type of load you can connect.
That is, only the load connected to the inverter would be working on Solar Power.
The regular Energy Meter in our homes work in one direction only.That is this meter records the amount of electricity drawn from the EB lines and used in the home.
A Net-Meter is a bi-directional meter. It works in two directions.
It records the amount of power drawn from the EB lines (import) and also the power sent to the EB lines (Export). So we get charged only for the difference.
For example, if in a month you consume 500 units of Power from EB and the solar plant generates 400 units, the meter will charge for only 100 units.
This works to our advantage when an On-Grid Power plant is used.
Even if we go on vacation, the power Generated by the solar plant will be completely exported and we get that much reduction in our EB Bill.
Net-Meter needs to be purchased from EB, and it costs around Rs.6000 for 3 Phase connection.
The Government subsidy is available only for Residential consumers.
To promote the use of Solar for other commercial users, Government had introduced the Accelerated Depreciation Scheme.
For commercial Organisations, who have taxable income Accelerated Depreciation could be used to claim tax benefits.
In solar projects, accelerated depreciation is widely used as an incentive to lessen the burden of tax. In India, Accelerated depreciation (AD) allows investors, mostly setting up capacity for captive use, to take advantage of up to 80% of the project cost.
Approximately 120 Sqft is required for 1 kW of solar plant.
Solar PV plants require a south-facing roof . The roof should also be free from shadows; portions of the roof that have shadows should be excluded while calculating the roof space available for the solar plant.
Shadows falling on solar panels reduce power generation, and may also damage the panels. Click here to see a video showing the effect of shadow on the Solar Power output.
The kind of roof determines if solar panels can be installed.
Ability of the roof to support the weight of the panels and mounting structure even in strong winds is the critical parameter.
Concrete Roofs – Solar PV plants can be easily installed on flat concrete roofs.
Inclined roofs may pose a challenge depending on the angle and direction of the inclination
Metal Roofs – This will depend on the type of structure and the weight it can withstand Asbestos/Other Sheet Roofs – These are the least likely of the 3 to be able to support solar panels, though it is possible in some cases.
Yes. In Tamil Nadu, under Chief Minister’s Cash Incentive Scheme (CIS), for the first 10,000 installations, subsidy up to Rs.50,000/ (Rs 20,000 from State Government and Rs 30,000 from central government’s MNRE) is available.
Starting 1st of April 2016, the central Government had revised the subsidy to Rs.24000/. So the actual subsidy available now is limited to Rs.44,000/- per installation.
From Oct 2016, the central Government had revised the subsidy to Rs.22500/. So the actual subsidy available now is limited to Rs.42,500/- per installation.
But there are some conditions:
- This CIS is applicable only for residential service connections . (Tariff LA1A).
- Only On Grid Type of Solar Plants (without Batteries) are eligible for subsidy.
- Plants installed by the TEDA (Tamil Nadu Energy Development Agency) approved Vendors are only eligible for Subsidy.
- On Grid Plant’s capacity should be 1 Kw, 2 Kw , 5 Kw or 10 KW.
- The maximum limit for the subsidy is
Rs. 50,000/- Rs.44,000/– Rs.42,500/-
Since above scheme is available only for residential consumers ,for the benefit of Commercial (non residential) consumers Central Government gives Income Tax benefits through Accelerated Depreciation.
A 1 KW On Grid power plant typically costs about Rs.1 Lakh to Rs. 1.5 Lakhs. After deducting subsidy the cost for a 1 KW On Grid Power Plant would be Rs 50, 000 to Rs.70,000.
Contact us for specific price range and how to order.
To get Government subsidy, you don’t have to do anything..!
Just choose the right Integrator / Installer… that’s all.
Most of the installers themselves would do the needful to get the subsidy from the Government.
For your reference here is the process anyway:
The subsidy is disbursed to end users by the State owned Enenrgy Development agencies.
In TN, this organisation is known as TEDA. (Tamil Nadu Energy Development Agency).
Tamilnadu Government had introduced a Cash Incentive Scheme for the first 10000 residential Solar Power Plant installations. (Only about 2500 people have availed this since 2013 !!)
As mentioned earlier, this Cash Incentive scheme bundles the subsidy from central Government (MNRE – Ministry of New and Renewable Energy) as well.
The subsidy is limited to a 1 KW system for residential user. That means even if you go for a 2 KW or higher capacity On Grid system, the subsidy would be limited to what is available for 1 KW.
The two components of this CIS scheme for a 1 KW system are:
- The state Government component is Rs:20,000/- (20% of the bench mark cost of Rs.1,00,000).
- The Central Government component is Rs:
24,000/– Rs:22,500(30% of the bench mark cost of Rs80,000Rs.75,000).
The subsidy amount will be paid to the Installer directly after the completion of the project.
The customer has to pay the installer only the balance amount after deducting the subsidy part.
To apply for this scheme, you need to register at the TEDA website with your EB service connection number. You may have to choose 3 Vendors (Installers) at this time.
Once registered, TEDA will verify your EB account that it comes under the residential Tariff (LA1A) and sanction your request. This request will be sent to the three installers. Once an Installer accepts the request, a work order would be generated for that company.
You need to down load that Work Order Form from the site, sign and send that to the chosen Vendor.
A Net Meter application form will also be generated at this time. That should also be downloaded and after verifying the details entered, submitted to your local TNEB Office.
The above process is for applying subsidy under the Chief Minister’s Cash Incentive scheme.
In TN making use of the above scheme is preferable..
In addition this scheme one can apply directly to MNRE under a different scheme (JNNSM – Jawaharlal Nehru National Solar Mission).
In Tamil Nadu Government’s CIS scheme, the end customer can deduct the subsidy amount and pay only the balance amount to the Installer.
But under JNNSM, we need to pay the full amount to the installer and later collect the subsidy from the Government. That is a tedious process and it seems there is huge backlog/wait list for this.
Technically speaking, yes, we can make an existing Inverter / Battery system to work with Solar PV panels in Off Grid mode provided the inverter and Battery bank are in good condition.
But practically such a system is not recommended for Residential users , since they cost more and not economical.
Commercial Establishments like Hospitals/Clinics, Shopping Malls, Warehouses and other Offices have huge open spaces on the terrace.
And many of them use Electricity almost 24 x 7 throughout the year.Resulting in a big , fat Electricity Bill..
By Installing ‘On Grid’ Solar Power Plants, the Electricity Bill could be greatly reduced.
A 10 KW On Grid Solar plant would generate approximately 1350 Units in a month.
At the Commercial Tariff (in TN) of Rs.8.05 this translates into a savings of Rs.10,867.50 a month.
These types of On Grid Solar Power plants are guaranteed to work for at least 25 years.
So in its lifetime a 10 KW Solar Plant would save Rs 32,60,250.
A 1000 square ft of empty space can generate this much money.!
They need practically no maintenance..all that is needed is to clean the Solar Panels once in a while, with plain water.
Making a one time capital expenditure will save a lot of money in the long run.. and hedge against the inevitable rise in the Electricity charges.
More over, the Accelerated Depreciation could be availed to claim 80% of this investment as depreciation in the very first year.
In the recent Budget proposals the Government has indicated this AD may be reduced to 40% from April 2017.
So if you are planning to go for Solar, time is NOW..!
Contact us for more details.