Karnataka Plans Rooftop Wind Aero Turbines, Issues Draft Rules

The Karnataka Electricity Regulatory Commission (KERC) has now issued draft norms to introduce grid-connected rooftop aero turbines in the state. The draft norms put forth by the state power regulator said that these systems could be installed onto the rooftops with or without rooftop solar systems. The draft notification aims to promote co-generation of electricity from renewable sources. KERC has asked the stakeholders concerned to send in their suggestions on the draft proposal till November, 8, 2024

The KERC draft supports the construction of Rooftop Aero Turbines (RAT). These are small-scale wind energy plants installed on rooftops to generate electricity by harnessing wind power. The regulation elaborated that these turbines are designed to operate in urban or suburban environments, where wind speeds are typically lower and more turbulent than in open areas. It mentioned the use of rooftop aero turbines to harness wind energy for residential power use, either in combination with solar power or without it. The Karnataka RE Policy 2022-27 under new initiatives also envisaged implementing rooftop aero turbines alongside solar power.

The KERC draft laid down conditions for the installation of RATs. It stated, “RAT plants with solar power must have a minimum installed capacity of one kilowatt, and the installed capacity of one resource shall not exceed the sanctioned load of the installation, while the other resource shall be up to a maximum of 25% of the installed capacity of the first resource. In such cases, the total installed capacity of the plant shall not exceed 1.25 times the sanctioned load.”

Procedure for Implementation & Reporting:

The notification stated, “The eligible consumer shall commission the RAT plant with or without solar power within 180 days from the date of approval of the PPA. If the eligible consumer fails to commission the RAT plant within this timeframe, the applicable tariff for electricity supplied from the RAT plant shall be the tariff determined by the Commission prevailing on the date of commissioning or 90% of the PPA tariff agreed upon, whichever is lower.”

Technical Parameters:

1. Interconnection with the Distribution System:
   • The RAT plant, with or without solar power, can be connected to the distribution network at the specified connectivity level.
   • In cases of gross metering, an exclusive line can be laid from the RAT plant to the distribution system.
   • The cost of the distribution network up to the interconnection point shall be borne by the eligible consumer.
2. Connection Requirements:
   • Every RAT plant with a capacity of less than 150 kW shall be connected only to the existing distribution transformer supplying electricity to the eligible consumer. In such cases, the total capacity of the existing and proposed RAT plants on that transformer shall not exceed 80% of the transformer’s rated capacity.
   • For example, if the transformer’s rated capacity is 100 kVA, the total allowable capacity of the RAT plants to be connected shall be 80 kVA.
   • Every RAT plant with a capacity greater than 150 kW shall be connected only to the existing 11kV distribution system. The total capacity of the RAT plants in such cases shall be limited so that the line current does not exceed 80% of the rated current-carrying capacity of the line.

Tariff Period and Tariff Design:

The regulation also laid down provision to enable the generate a Debt-Equity Ratio of 70:30, or such other ratio at the generic tariff, as the Commission may decide from time to time. Other provisions are mentioned below:

1. Depreciation:
   • The value base for depreciation shall be the capital cost of the asset as admitted by the Commission. Depreciation shall be allowed up to a maximum of 90% of the capital cost, and the salvage value of the asset shall be considered as 10% of the capital cost.
   • Depreciation shall be based on a ‘differential depreciation approach’ over the loan period and the useful life of the RAT plant beyond the loan tenure, computed annually using the ‘straight line method’.
   • If the debt component is 70% of the capital cost, the depreciation rate for the first 13 years of the tariff period shall be 5.83% per annum. In other cases, the depreciation rate shall depend on the debt component and loan tenure, with the remaining depreciation spread over the balance useful life of the project. Depreciation shall be chargeable from the first year of commissioning of the RAT plant.
2. Return on Equity: The value base for equity shall be 30% of the capital cost, and the normative return on equity shall be 14% per annum for the tariff period, or such other rate as decided by the Commission from time to time.
3. Operation and Maintenance (O&M) Expenses: O&M expenses shall be equivalent to 1% of the capital cost. The normative O&M expenses allowed during the first year of the control period shall be escalated at a rate of 5.72% per annum over the tariff period.