Renewable Energy and Energy Efficiency

It will depend on the location of where your solar panel is located. One key resource is the NASA website.

You can follow the following steps:

• Go to: http://eosweb.larc.nasa.gov/cgi-bin/sse/retscreen.cgi (you will need to register but the process is simple)
• Enter the latitude and longitude of the location. For example, the latitude of Bangalore is 12.980N and 77.580E and the latitude of Chennai is 13.080N and 80.270E.
• You will be taken to a page which has information on the average monthly temperature, wind speeds, and daily solar radiation – horizontal.
• You will also see the yearly average of the daily solar radiation – horizontal.
• The average daily solar radiation – horizontal for Chennai is 5.23 kWh/m2/d. we will use this data to calculate the potential of a 100 kW system.
• Typically solar panels are put at a tilt equal to the latitude which increases their efficiency by 15%.
• Total electricity units generated can be calculated for your project size can be calculated as shown below:

You can work with your solution provider to understand the specific values of the parameters in your case. In general, in India, and in the cost benefit scenarios that we have shown, the solar production varies from 145,000 to 165,00 kWh/100kW of solar panel. This is considered a safe assumption as the number of electricity units produced depends on the month.

The thumb rule is that 12 sq. m of area (about 130 sq. feet) is required to install 1 kW of system.

This is a fairly significant area requirement. In terms of planning new buildings, one consideration should be to keep a large portion of the roof free for installing solar. In existing buildings often the roof area is already utilized with solar water heaters, recreational areas, water tanks and lift rooms. This makes solar rooftops often difficult to install in retro-fit buildings. Work-arounds include using solar sheds on roofs or in areas such as bike parking (in commercial building campuses). A solar shed is a construction on the roof allowing for the usage of the roof for solar panels or other purposes.

At this point, excess units cannot be sold to the grid. Net metering regulations have to be introduced. Net metering enables monitoring and billing for a two way flow into the grid metering process. It records the import and export of electricity at a consumer level. Net metering enables customers to feed the excess electricity they generate back (typically from renewable sources) back to the grid. During this process, the electricity meter runs backwards, thus allowing customers to get the credit at retail prices for this excess generation. Net metering serves as an incentive for the consumer to install RE power and is particularly useful for promoting roof top solar.

In India net metering is not allowed so one type of system that is in vogue is net-tied (the capacity of the system is carefully calibrated so that all the power generated is consumed).

The solar system becomes viable in the case of green building certification requirements and/or when the solar is replacing diesel power. The cost of the diesel power will vary depending on the efficiency of the DG set and the costs of transporting and storing diesel. For the purpose of the cost benefit calculations that we have below we assume that the cost of diesel power is Rs. 15 /unit, which we believe is reasonable.

The solar system becomes viable in the case of green building certification requirements and/or when the solar is replacing diesel power. The cost of the diesel power will vary depending on the efficiency of the DG set and the costs of transporting and storing diesel. For the purpose of the cost benefit calculations that we have below we assume that the cost of diesel power is Rs. 15 /unit, which we believe is reasonable.

Like in all our cost benefit examples, the data shown is collected from vendor sources or customer case studies. The results are indicative and will depend on specific equipment and operating conditions.

Scenario One

Customers who are planning a marginal increase in electricity consumption and have to go in for a 11 kv dedicated feeder line or a 33 kV feeder line. In that case, the capital expenditure that will need to be put up for the feeder line from the substation can be utilized towards the solar panel.

Office Building

In this case the solar panel is assumed to meet 30% of the organizations energy needs. The company installs solar panels of 225 kW even though it can avail of subsidy benefit only to the extent of the capital expenditure of 100 kW. The company is profit making and claims depreciation on the solar panels to set off against its tax liability.

Scenario Two

Customers in states which are undergoing a power crisis situation where there are restrictions on peak on the maximum connected load and/or also on the maximum number of units consumed in a month.

Industrial Organization

The company has installed a 100kW solar panel. This is a “net tied” (that is the capacity of the system is carefully calibrated so that all the power generated is consumed) system in the sense that there is no battery in the implementation. The solar power system is sized correctly and the circuitry adjusted so that all the power produced is consumed instantaneously. In these cases, the payback period is often around 5 years without taking into consideration depreciation or subsidy. While this company can claim subsidy and can avail of tax benefit, in cases of power shortage solar makes fairly simple economic sense.

Residential Building

This is a small stand alone building with 23 flats (small flats of average area at 1000 sq. feet). In this case, the capital cost increase is about 4%. The rooftop space is utilized as a solar shed. The building does not have a DG set. The solar panels charge a solar UPS and the residents have the advantage of no power cuts and reduction in their electricity bills.

Bank Branches

Bank branches in fringe urban and rural areas are a good example where solar can be applied as the number of units required per day are not that high and the grid power situation requires DG sets to be run. Typically bank branches in these areas have about 2-3 computers, a few fans and lights. They do not have ACs.