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What is a Solar Rooftop System? 

In a solar rooftop system, the solar panels are installed on the roof of any residential, commercial, institutional and industrial buildings. This can be of two types (i) Solar Rooftop System with storage facility using the battery, and (ii) Grid Connected Solar Rooftop System. 


What is a Solar Rooftop System with Storage facility? 

Such rooftop system has a battery as a storage facility. The solar electricity is stored in the battery and can be utilized during the night also when the sun is not available. 


What is a Grid Connected Solar Rooftop System? 

In grid-connected rooftop or small SPV system, the DC power generated from SPV panel is converted to AC power using power conditioning unit and is fed to the grid either of 33 kV/11 kV three phase lines or of 440/220 Volt three/single phase line depending on the capacity of the system installed at institution/commercial establishment or residential complex and the regulatory framework specified for respective States. These systems generate power during the day time which is utilized fully by powering captive loads and feed excess power to the grid as long as grid is available. In case, where solar power is not sufficient due to cloud cover etc., the captive loads are served by drawing power from the grid


Where can such plants be installed? 

Such rooftop systems can be installed on the roofs of residential and commercial complex, housing societies, community centers, government organizations, private institutions (Schools, Colleges, Hospitals, Ashrams, NGO’s, Hostels), factories, warehouses/ godowns, Car Garages, Function/ Marriage Halls etc.


How much Space is required for Solar Power Plant?

Typically, 1 KW Solar power plant requires 100~120 Sq. Ft (10-12 Sq Meter) roof space.  


What type of roof is suitable for a Solar Plant?

RCC Roof, Inclined Roofs (Metallic roof, with RCC slabs, Tiled Roof)/ sheds are suitable for mounting rooftop solar plants.  Asbestos corrugated sheet roofs are generally not suitable as the asbestos sheets tend to crack. 


What is the size of grid connected rooftop solar system? 

The rooftop solar systems from 1 kWp up to 500 kWp or in combination can be set up on the roofs.


What are the advantages of Grid-Connected Rooftop Solar System? 

  • Electricity generation is at the consumption center and hence Savings in transmission and distribution losses 

  • Low gestation time (typically a 100 kW plant can be installed in 4 months time from Order date. Actual installation takes 2 weeks time)

  • No requirement of additional land as unutilized roof is being used

  • Improvement of tail-end grid voltages and reduction in system congestion with higher self-consumption of solar electricity 


Is Solar Technology Proven?

Solar Power MW scale Plants are in successful operation for over 30 years globally.

  • In India kW scale plants are successfully operational for 30 years & MW scale projects are in successful operation for over 10 years


How does Solar Power Plant function? What are the components of the Solar plant?

A Grid interactive Rooftop solar PV system primarily comprises of Solar PV Modules (panels), Inverters, Mounting Structures, Junction Boxes, Cables, Panel and a Meter (Two-way meter). 

  • Solar PV Modules (Panels) absorb light energy of sunrays and convert to DC power (electricity).

  • DC power is converted to AC power in the Inverters

  • Solar Panels are mounted on structures (either Steel or Aluminum).  The Structures with panels are mounted on the rooftops with either concrete foundations (for RCC roof) or bolted to the Steel roof.  Solar Panels are connected through junction boxes to the inverter.  Multiple inverters will be connected through a common cable to a Panel which in turn will be connected to the same Meter from the Electricity Board

  • Existing Power meter will be replaced by a two-way meter (make and model approved by the Electricity Distribution company i.e. Discom of the state).

  • After Installation of solar plant, it will be connected and synchronized to the grid in presence of Discom Engineer who will certify the Commissioning. 

  • All this work will be in the scope of SolarBull


If I install Rooftop Solar Plant, will I continue to hold the power connection from the Electricity Board (EB) / Distribution Company (Discom)?

The connection from the Discom will be continued.  


Are you proposing a Battery Back-up? 

No. We are proposing a Grid Connected or Grid Interactive Rooftop Solar System. There is no battery back-up. Batteries need replacement every 3-5 years and are very expensive


Will the Client CMD - Contract Minimum Demand come down?

While you need to keep the same CMD as per Govt rules, the actual load/ actual demand will come down except for break-downs/ unexpected weather changes


What is surety of the quality of components? 

We will quote all Tier 1 components: Modules, Inverters, Cables and all other components.  These are all well-proven materials in Indian environment


What is the lifetime of a typical Solar Power plant?

The useful life of a typical Solar Power plant is considered to be 25 years. This is the duration for which long-term PPAs are signed and financial models are built. However, Solar Power plants can run beyond 25 years while producing a lower output. 


How much electricity does a rooftop solar PV system generate? 

The amount of electricity generated by a rooftop solar PV plant depends on the location, orientation of the roof, panel efficiency, and ambient temperature. As a rule of thumb, a 1 kWp plant will generate about 4 kWh (units) per day OR 120 kWh (units) per month or 1400 kWh per annum of electricity on average in the first year.  

The generation gets reduced by approx. 0.8% per annum over the life of the project. Typically Solar Panel manufacturers guarantee an output of 90% at the end of 10 years and 80% at the end of 25 years. 


What's the Guarantee of the Solar Power Generation?

We will assure Generation Guarantee in kWh/kW/annum (average) after site assessment


What's the Maintenance assurance?

  • SolarBull gives a comprehensive warranty for 1-5 years during which all maintenance complaints including parts replacements shall be attended by us free of cost to you.

  • We shall install a Remote monitoring system as part of the supply (no extra cost to you).  We will be monitoring the performance remotely


What about maintenance Post warranty of 5 years?

SolarBull offers a post warranty – Annual Maintenance Contract (AMC).We strongly recommend you to sign the AMC contract with us however this is optional.


What is Net Metering? 

The grid connected rooftop system can work on a net metering basis wherein the beneficiary pays to the utility on net meter reading basis only. Alternatively, two meters can also be installed to major the export and import of power separately. 

We are proposing a Net Meter which will be installed by us (SolarBull)

  1. What happens to the Solar power during holidays/ when the Client is having low load?

  • As per the Net Metering (will be installed by us at no extra cost): which will be certified by Local Electricity Board officials, any excess generation (solar generation - consumption in the college) will flow to the Grid and recorded in the Net Meter as "Export".  Any excess consumption (Total consumption - Solar generation) will be drawn from the grid and recorded in the Net meter as "Import".  

  • At the end of the month, the Electricity Board (Discom) takes readings of total Export and Import in the month. The Discom will raise the invoice for Net import in the month (Import - Export).  

  • If there is Net Export (Eg. Summer holidays), the Net Export kWh is kept as "Credit" in the account of the Client in the next month bill. The credit can be carried forward up to a year (April to March).

  • Hence the Solar power generation is not wasted and gainfully utilized by the College.


Does rooftop solar PV generate power during a power failure? 

No.  You need Grid Power or DG power as a reference for Rooftop to run.  When the power fails, DG needs to be operated. DG can be operated either manually OR on auto-mode using an auto-change over PLC system. However, with rooftop solar, the load on DG can be reduced to 30%-40% and the balance load can be taken by the Solar plant during the day.


Are there any days when there is no generation?

  • Solar power is generated on all days except fully cloudy days/ heavy rainy days.  The Generation per day/ month varies from month to month. 

  • Power generation is high during Summers, moderate in winters and low during monsoon. There will not be any generation during completely cloudy days. There will not be any generation during the nights.

  • We will assure an average generation kWh/kW per annum after site assessment


In the case of grid failure, is there any chance for shocks to the person who is repairing?

In case the grid fails, the solar power has to be fully utilized or stopped immediately feeding to the grid so as to safe-guard any grid person/technician from getting shocked (electrocuted) while working on the grid for maintenance etc. This feature is termed as ‘Islanding Protection’.


What are the grid connectivity levels for Rooftop Solar systems? 

The Rooftop Solar projects fall into two broad categories i.e. 

  1. the projects connected to HT voltage at distribution network (i.e. below 33 kV) 

  2. the projects connected to LT voltage i.e. 400/415/440 volts (3-phase) as the case may be or 230 volts (1-phase). 


Accordingly, the projects may be under the following two categories. 

Category 1: Projects connected at HT level (below33kV) of distribution network The Projects with proposed installed capacity of minimum 50 kW and up to 500 kW and connected at below 33kV shall fall within this category. The projects will have to follow appropriate technical connectivity standards in this regard. 

Category 2: Projects connected at LT level (400 Volts-3 phase or 230 Volts-1 phase) The Projects with proposed installed capacity of less than100kW and connected to the grid at LT level (400/ 415/ 440 volts for 3-phase or 230V for1-phase) shall fall within this category.


What are the business models that can facilitate the promotion of grid connected rooftop solar systems? 

There can be many possible business models, some of which can be considered are as follows: 

(a) Solar installations owned by consumer 

  1. Solar Rooftop facility owned, operated and maintained by the consumer(s). 

  2. Solar Rooftop facility owned by the consumer but operated and maintained by the 3rd party. 


(b) Solar installations owned, operated and maintained by 3rd Party. 

​​   3. Arrangement as a captive generating plant for the roof owners. The 3rd party implements the facility at the roof or within the premise of the consumers; the consumer may or may not invest as equity in the facility as mutually agreed between them. The power is then sold to the roof owner on Rs/kWh basis against a PPA – Power Purchase Agreement to be entered between the Consumer and the 3rd Party. In this arrangement, the Roof owner (Consumer) leases out the roof/ premises to the 3rd party solar developer for the period/tenor of the PPA. The PPA tenor varies from 15 years to 25 years.


Is rooftop solar power cheaper than diesel/grid power?

Rooftop solar power is much cheaper than power from diesel generators. Solar PV generates power at a cost of about Rs. 5.00/KWh while diesel generates power at about Rs. 16/KWh. 

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