Rooftop Solar PV System Buying Guide for Urban Consumers

Today a typical urban house is equipped with – A tv, freeze, washing machine, AC, fans, lighting, CCTV, Mobile, Lift, Motors, etc

The common thing required to run all these gadgets is electricity. We can’t think of a smooth life without these gadgets and electricity. In Fact, backup systems like battery banks or DG sets are installed for uninterrupted supply.

The problem in urban area is not the availability is electricity, in fact in many A&B class or metro city availability is electricity is not an issue

But the issue is the charges, if you see your electric bill the average charge you pay is somewhere between Rs 6- 12 per unit in domestic sector.

Apart from that it keeps on increasing and it will keep increasing

Everyone tries to reduce his electric bills; some go for energy-efficient equipment’s and some limit their usage.

But everyone wishes for a one-time permanent solution for his electrical demand

Here Solar energy plays a vital role, you can generate your own electricity, use grid as storage, and use your electricity any time

Solar energy has solutions for every segment – the only thing is you have to understand the system and select the system as per your requirement

We can categorise these solar systems as per the prevailing problems

Grid Connected Rooftop (GCRT) Solar System

These systems are tied to the utility grid through a grid-interactive inverter and AC meter typically installed for residential, commercial, or utility applications and do NOT provide backup power in the event of an outage.

Working of an on-grid solar pv system

• In the daytime, the energy requirement by the connected loads is fulfilled by solar photovoltaic (pv) system installed.If or when the demand side consumption exceeds the power produced from solar PV plant, the grid-tied inverter imports the excess power from the grid.Similarly, if power
  • produced by solar modules is greater than demand load, the excess power is exported to the grid for which the consumer gets energy credits from the Electricity department.
  • Thus, in daytime, the primary source of energy is Solar.
• In the evening and night time, when the sun is not present, the grid powers the load connected throughout. Thus, during this time, the primary and only source of power is the grid supply.

An on-grid system is designed to first allow solar energy to be consumed by the customer. The system owner acquires the energy credit at the end of the month (maybe year – in some states) if the electricity exported exceeds the import and only pays for the electricity imported from the grid in case import exceeds the exports. This system involves, the installation of a net energy meter that keeps track of electricity imported and exported by and to the grid.

The following components in Figure 2 are the primary constituents of a typical residential On-grid solar pv system:

Power Flow through a Net-metered Grid Connected System

1. DC electricity is generated in the solar module, proportional to the sunlight intensity. The modules can be attached to a variety of mounting systems and secured to the roof with mechanical fasteners or in some cases secured solely with ballast. The goal is to mount the modules with proper tilt angle and orientation in a safe and mechanically sound manner and position them in an aesthetically pleasing design.
2. The array power flows through the wires (conductors) from the modules to a DC distribution box, which includes Surge protection devices for safety against over-voltages and may also include a DC disconnect switch, if not integrated within the inverter.
3. The DC Distribution box basically acts as a combiner, where multiple solar strings get combined.
4. The array of DC power flows into the inverter where it is converted into AC power at a voltage level equal to the utility service connection. The inverter operates the array at its maximum output potential throughout the day and then “goes to sleep” at night. (Power from multiple arrays flows into multiple inverters in large systems or can be routed into one large central inverter)
5. The AC Distribution box is where the AC side breaker is installed, to prevent the overcurrent on the AC side. If multiple inverters are installed, their outputs can be combined in the ACDB box.
6. The MCB or MCCB is the protection device, which protects the solar electric system against overcurrent.
7. A solar unidirectional energy meter is used to record the energy that is being generated by the solar array. The meter is set to measure production only, and power flows through the meter as if the Inverters were a utility, allowing the meter to count upward as energy is generated.
8. Existing load centre is the interconnection point where the solar inverter is coupled to the other AC loads.
9. A bi-directional energy meter is a 2-way meter that can measure the energy that is imported from the grid and exported to the grid by the solar system.
10. Conventional Lightning Arrestor is used to protect the solar system from direct and indirect lightning strikes that may occur or hit the nearby structure.
11. It is the dedicated earth pit for the lightning arrestor.
12. It is the dedicated earth pit where all the DC equipment (Inverter DC side and DCDB) are grounded.
13. It is the dedicated earth pit where all the AC equipment (Inverter AC side and ACDB) are grounded.

Applications:

1. It is best suited for customers with stable grid power and minimal power cuts.
2. Other than homes, even educational institutions, industrial units, and commercial establishments use these systems as their primary source of power.
3. Additionally, these establishments can install an on-grid system as the system can synchronize with diesel generators to provide uninterrupted power.

Advantages:

1. Huge reduction in electricity bills

With net meter in place, the consumer has to pay only for the surplus electricity he/she consumes, ensuring the bill generated every month is reduced drastically. They do not require bulky and costly battery storage solutions, as fewer solar panels are required due to no need to produce extra power when there is no sunlight.

• Reduction in carbon footprint

Solar PV systems generate clean, renewable energy that does not produce greenhouse gas emissions. This factor is among many potential pros of on-grid solar systems since the consumer contributes to safeguarding the eco-system.

• Easy maintenance

The elimination of batteries in the on-grid system makes maintenance quite easy. It also eliminates the cost of upkeep of the batteries.

• Synchronize with other sources of power

These systems can also synchronize with a diesel generator on site. This is important in case grid power is not available.

• Increase the value of home and business

The on-grid solar systems can increase the value of consumers’ homes or businesses. In some cases, solar panels can make your home more valuable than without them.

• Optimized energy production: 

On-grid solar inverters are optimized to produce the maximum amount of energy possible.

• Anti-islanding protection: 

On-grid solar inverters shut down the power supply to the house the minute electricity goes off from the grid. Although Anti-Islanding results in a power outage at home, it is important. If a lineman is working at a faulty site and your system keeps producing electricity despite the grid having been shut down, the working personnel will get electrocuted.

• Better Return on Investment

The cost of an On-grid solar system is lower than other types of solar systems because there are no batteries. It also generates the highest amount of power compared to other types of solar systems.

• Easy to install

Installation of an on-grid system is easy and can be done easily by oneself on the rooftop. It can be easily installed on residential rooftops, rooftops of commercial complexes, housing societies, community centres, government organizations, private institutions, etc.

1. Less Costly 

Since an on-grid solar system does not require batteries, it is cheaper to install when compared to an off-grid system. It is less costly when compared to other solar systems.

1. Subsidies and Other Incentives

A user can avail of government subsidies and other incentives to install on-grid solar systems.

Limitations:

1. On-grid solar systems are battery-less and therefore not able to function or generate electricity during a blackout.
2. They can’t produce solar energy and reduce power bills at night time or when there’s no sunlight.

Approx Cost of an On-Grid System

Described below is an approximate (minimum) cost of a 2 kW Grid Connected System (Non-Subsidized)

Total System Cost Including GST and Installation = ₹ 1,11,377

Return of Investment

Let’s calculate the return on Investment on a 2 Kw on-grid pv system.

Total Effective Cost of 2 kW Solar System = ₹ 1,11,377

Let’s assume that 1 kW of the solar system would generate 4.5 kWh (4.5 units) of AC energy.

Let’s also assume that average sunny days per year = 320 days

Total units generated by 2 kW solar system = 320 * 2 * 4.5 units = 2,880 units

Let’s consider the average electricity cost per unit = ₹ 7.00

Saving in 1 year = ₹ 7.00 * 2880 = ₹ 20160

Savings in 25 years = ₹ 5,04,000

Return on Investment in number of years = 5.52 years

Investment Return Rate for 1st Year= 18.10 %

Note – Here, an electricity rate is assumed to be constant, which is not the case usually. The customer can have a payback period of around 4.5 years if 3% increase per year in electricity cost per unit is considered.

Subsidy structure for on-grid solar pv system

Central Financial Assistance (CFA)/ Central Government Subsidy for rooftop solar plant installed by a residential consumer under the simplified procedure is as follows.

Calculation of CFA/subsidy: The CFA/subsidy would be calculated based on the total solar module capacity/solar inverter capacity/capacity approved by DISCOM, whichever is lower.

1. Apply online – National rooftop portal: https://youtu.be/gtwJx67pTCk