Citizen Matters previously brought to you a series of articles on Rainwater harvesting that included information on how best to go about incorporating best management practices of tapping the resource of rainwater within your own community. An earlier piece answered some basic questions about Solar Power in India. In a continuation of that series, this piece explains in simple terms how people can introduce solar power as an additional or alternate source of energy in their homes.

Bangalore's daily power demand is about 2300 Mega Watts (MW), about one-third of the state's total power consumption. The average 2/3 bedroom home consumes approximately 15,000 Watts (0.015 MW) of power every day. Depending on the amount of unshaded roof space available in your home, you could cut your dependence on the electricity grid and even get paid for the electricity generated at your home.

What you need to know:

What is solar power? How is it generated?

Solar Power is the generation of electricity by photovoltaic cells placed on a rooftop or similar area with good access to sunlight.

There are three essential components in the standard Solar Power System:

  • Photovoltaic Panels: These are the photovoltaic cells that convert solar energy to electricity. This component has the greatest area requirement, with the number and size of panels corresponding to the energy requirements of the building.
  • Inverter: The inverter converts the Direct Current (DC) power generated by the panels into usable Alternating Current (AC) for use in the building. Inverters are available in a variety of capacities, depending on the expected electricity load.
  • Battery: The battery stores the electricity generated by the panels, which is generated during sunlight hours, for use during the night or whenever no power is being generated. Battery sizes vary, and are usually chosen based on the night load.

How does solar power fit into existing electricity systems?

There are two main ways in which any solar energy production system can be set up: Off-Grid and Grid-Tied systems.

An Off-Grid System is the one where any electricity generated is used for internal consumption alone. Such a system can be designed either as a supplemental or an alternate source to a local electricity supply. This type of system is easier to install, and, with smaller requirements, is often more economical. A disadvantage to this system is that any unutilised energy that might be generated goes unharnessed.

A Grid-Tied System is tied into the local electricity supply, e.g. BESCOM. This essentially means that any electricity generated by the system that is greater than the daily used amount is exported to the electricity utility company. In Bengaluru, the BESCOM currently offers a preferential tariff of ₹9.56 per unit when purchasing electricity from consumers, with a reduction to ₹7.20 per unit if they have availed the 30% subsidy at the time of installation. However, the specifications of connecting to the utility grid make this option a larger initial investment.

Why consider solar power?

Environment-friendly and convenient energy production: Unlike energy generated by thermal power plants dependent on fuels, solar energy has no costs associated with the source of energy. It does not generate any gases or disposable waste as in the case of other common grid-based power sources. Unlike hydel and wind power (which are also green and clean power sources), solar power is available throughout the year and is not drastically affected by adverse weather conditions. A rooftop solar energy system could save an average of a tonne of CO2 per year, more than 30 tonnes in its lifetime.

Freedom from power cuts and dependence on the utility grid: A well-designed solar electricity system provides uninterrupted flow of electricity to a residence, whether as a complete system or as a supplement to the utility grid.  

Long-term cost benefits: Setting up of a solar energy production system represents a large capital expense, usually costing a few lakh rupees. However, when considered over a long term, a solar power system guarantees production of electricity over a period between 15-25 years with minimal to no maintenance, compared to the fluctuating rates and availability of electricity through the utility grid. Additionally, setting up grid export schemes could eventually lead to the system running at a new profit due to the amount of electricity generated.

How do I assess my energy needs?

Energy requirements for a home are based on several factors:

  • The types of equipment used in terms of high load (e.g. ACs, motors, induction stoves etc.)
  • The usage patterns of different equipments in terms of duration and time of use
  • Total consumption in a month in terms of units

You can see the maximum KW usage for your household reflected in your electricity bill. Analyse your daily and monthly electricity usage and decide how much of that load needs to be taken up by the solar system.  If the solar system is to be used only as a backup to the utility grid, then the calculations could include only those appliances which would need to run under solar power, similar to assessing the needs of a backup generator or UPS. Many of these decisions will be affected by the budget and by technical requirements of the panels such as roof area, non-shaded area, possible angle of installation etc. Your service provider should be able to help you refine your requirements based on the limitations in your particular case.

How do I select a provider?

There are a number of established providers of solar energy systems in the city. The following points should be considered when making a choice:

  • Ask the provider what their background is in terms of training and experience.  
  • Check that the firm has an established customer base and track record. Consider contacting prior customers to find out how their systems have fared over time.
  • Ensure that their components meet current standards and that there is a way to ensure the quality of the work.
  • If opting to go for a Grid-Tie system, ensure that the provider is aware of all the technical requirements.

How is a system designed to suit my needs?

The solar system design is based on both energy needs and budget requirements. The three main components of the electricity system mentioned earlier form the bulk of the cost of the installation. The following guidelines are used by most providers in suggesting a system to meet your needs. A few typical loads and scenarios are laid out at the end of this article in greater detail.

Solar Panel

Solar panel cost depends on energy requirement. The average size requirement is 100 sq. ft. of panel area per KiloWatt of power. The KW requirement is calculated based on the usage patterns and the types of equipment that needs to be supported.

The size of the panel is generally calculated based on the KW requirement and the energy load of the selected inverter. Exact sizes may vary based on orientation of the roof and the installation, shade occurring on the roof and technology of the panels.

Since the solar panels are usually imported for installation, the cost is dependent on the time of the year and the foreign exchange rate. Installing during winter months can reduce the costs due to the off-season.

Inverter

Inverter prices depend on the load and on the design of electronic components.

Inverters with greater efficiency (e.g. 95-99%) are more expensive than those at lower efficiencies (e.g. 75-80%). Inverter prices also change based on technical specifications related to surge tolerance, data logging and tracking etc.

Solar panel requirement will increase in the case of cheaper inverters due to losses because of lower efficiency.

The BESCOM grid export scheme requires the installation of an approved high-efficiency hybrid (with battery) inverter.

Battery

Battery costs are proportional to amount of night-time load that needs to be met, since electricity generated during the day can either be used immediately or exported to the grid.

The other components that go into the installation are the mounting structure for the panels, and the electrical components including the wiring, junction box and fuses. It is highly recommended to ensure that the rating and specifications of the electrical components are high enough to support the loads generated. A primary cause of failure in the case of power generation is the use of low-quality materials that require expensive replacing and rewiring.

Different scenarios for solar power

In Bengaluru, electricity is billed on a tier system, as shown below:

Fixed charges per month

For the first KW

Rs 25/- per KW

For every additional KW

Rs 35/- per KW

Energy charges

For 0 - 30 units (Lifeline consumption)

270 Ps/unit

31 to 100 units

400 Ps /unit

101 to 200 units

540 Ps/unit

Above 200 units

640 Ps/unit

(Tariffs for 2015 according to BESCOM. LT-2(a)(i) : Applicable to areas coming under Bruhat Bangalore Mahanagara Palike (BBMP), Municipal Corporation and all Urban Local Bodies.)

Consider a typical family of four in a three-bedroom house with a monthly consumption of 200 to 400 units (KWH). Clearly, even reducing consumption from one tier to another can lead to a significant effect on the electricity bill.

Based on the types of appliances and the daily usage patterns, the maximum load for this household could range between 1 and 5 KW. Apartments or larger loads can go up to 10 KW. A solar power generation system can be designed to take care of any portion of this or the entire load.

Most solar power installation companies will work within the client’s budget to design the best solution for their specific needs. Following are a few examples of scenarios for different power requirements, based on information by Sekar of TerraCura.

Notes:

  • In all cases, the solar panels are assumed to be fixed on a flat roof with no additional mounting, and that the cabling is for one floor height at most. Prices will vary based on individual conditions.
  • The list is arranged from the simplest to more complex solutions (cheapest to more expensive). Grid Export solutions are marked with [GE].
  • The “Load” refers to the amount of electricity which needs to be generated from the solar panels. Actual panel sizing might increase based on the power needed to run the inverter itself.

Type of load requirement

Changes in component quality

Load

(KWp)

Price (₹Lakhs/KW)

Battery size

Inverter

Load mostly during the day (for example for Small Scale Industry use)

Can be minimal because of low night load

Inverter used here is at 70% efficiency and 110% surge tolerance, with basic data tracking and logging.

1 - 5

1.38 to 1.45

Lighting and fan loads only, with only one TV, one 500-700W mixie, etc to be supported.

Medium to high, with slight variations in rates

As above

2 - 3

1.42 to 1.48

Based on battery sizing and solar sizing

Lights, fans, and domestic loads such as refrigerator, washing machine, etc. (but not AC, induction stove, and similar motors)

As above

Inverter used is a higher quality with 75-85% efficiency, capacity for 150% surge tolerance, harmonic filters and more robust data logging and tracking.

2 - 5

1.35 to 1.45

Based on battery sizing

[GE] The above plus AC, induction cookers, lifts, etc. (as long as solar sizing and battery sizing match)

Includes Small to Medium Scale Industries

Based on BESCOM specifications*

Inverter efficiency is 90-95%, and it has electronics to deal with harmonics, provides surge tolerance of 500%, provides excellent data logging and analytics tools.*

2 - 10

1.75 to 1.95

*Here, the inverter is a hybrid type (with battery) and must be of a type approved by BESCOM. The BESCOM website gives a list of grid tie inverter manufacturers and the accepted inverters which can be used to supply electricity to the grid. The Studer brand inverter (Swiss imported) is the only one approved by BESCOM in this category (i.e. hybrid).

Grid Export solutions also exist without a battery. These are not suggested in an Indian context due to the lack of guaranteed 24-hour electricity, and so are used in Industrial contexts with mostly daytime loads.

Type of system and load requirement

Comments

Load

(KWp)

Price (₹Lakhs/KW)

[GE] Without batteries; mostly for good grid supply areas and medium-large industries.

Solar inverters are grid-tied, string inverters, and do not care about the type of loads.

The system requires power in the grid connection for the solar to operate and generate power.

Whatever maximum power that is generated at any point in time from solar is dumped on to the grid lines, which are connected to the load. If there is no load, the generated power gets exported.

No limitations on surge; inverter efficiencies are 95-99%.

3 - 100

1.1 to 0.75

(Price reduces per KW as total solar sizing is larger)

More on financing and return on investment

In the event that the solution chosen is one with a Grid Export, it is necessary to apply as an exporter of solar power. The application form is available here, and the guidelines for implementation are listed on the BESCOM website here.

Additionally, solar panels are now considered home improvements, and can be paid for using home improvement loans. The Ministry of New and Renewable Energy (MNRE) offers 30% subsidies for the total cost of the system. As mentioned earlier, if the subsidy is availed, preferential tariffs for Grid Export reduce from ₹9.56 per unit to ₹7.20 per unit.

Corporate users can avail an accelerated depreciation of 80% in the first year for their investment.

Based on your typical electricity usage, the type of installation, and the load of the solar system, the savings on the electricity bill will vary. A significant fact to remember is that solar panels come with a 25 year lifespan with steady power generation with no running costs, compared to fluctuating availability of electricity from the grid and possibility of increase in prices from the grid.

In general, assuming that the electricity tariffs from the grid remain at their current rates (which is highly unlikely), a solar system will pay for itself within 10-12 years following which the only costs will be the reduced electricity bill. If rates increase in the following years, savings can be significant enough to reduce this period to 8 or even 6 years. With an active grid export system, costs after return on investment (ROI) are negative; i.e. you are paid for the electricity you produce.