India has a momentum with National Solar Mission with a goal of 40 GW IN 2022 for rooftop and recently, the goal for solar is extended to 100 GW in 2022. India and France launched International Solar Alliance to boost solar energy in 121 countries with an aim to deliberate on a finance mechanism for the promotion of solar energy in member countries, crowd-funding and technology transfer.

India’s present rooftop solar installed capacity is 1.9 GW which is 10% of total installed capacity of solar energy. Indian rooftop solar market is in nascent stage but government has an ambitious target of 15 GW by 2022. To add, several banks, including the State Bank of India (SBI) and Punjab National Bank, have committed to providing financing support to rooftop solar projects.

The World Bank announced a $625 million loan to SBI to provide discounted finance for rooftop solar installations on factories and institutions.

The environmental profile of rooftop solar is impressive compared to other renewable energy sources. Solar panels generate electricity with no air or carbon pollution, no ash or other waste products, and no inputs other than sunlight. Individuals and businesses have been attracted not just to the environmental benefits of solar power, but also to the ability to generate their own power.

Some of the major advantage of installing solar rooftop are:

  • Cleaner source of energy
  • Reduces imports of fossil fuel
  • Reduces dependency on grid power
  • Provides financial benefits as surplus energy produced is paid back (in the form of reduced electricity bill) by utility
  • Reduces T&D losses

As renewable energy is gaining popularity, the solar industry is growing very fast. But there are also challenges related to it. Some of them are listed below.

  • Variability and uncertainty of sunlight
  • No specific central regulation for solar PV power quality in India. As a result, validating the power quality of solar PV differs from state to state.
  • Massive exercise for DISCOM to keep check on power quality.
  • Criticality in performance measurement of Rooftop solar and inverter
  • No regulation for frequency response.
  • Karnataka is the only state in India having mandate for reactive power support.
  • No alternatives to meet contingencies of power flow.
  • Absence of accurate forecasting mechanism

Integration of rooftop solar has considerable impact on the grid which can be divided into technical and commercial impacts as mentioned by experts in APQI Webinar on ‘Impact of solar net metering on grid stability and preparations that Discoms can undertake’

  • Technical
    • Increases voltage rise, voltage imbalance and instability
    • Increases losses in the system and creates system protection issues
    • Stability of the system also hampers due to weather fluctuations.
    • Increases frequency fluctuation
  • Commercial
    • Initial installation cost is very high
    • Consumer is already sensitive and injection of solar system increases it

To overcome all the problems and make system more reliable and efficient, Discom has a vital role to play. Some of the major steps that DISCOM should undertake are as follows.

  • Participate from project development, installation and O&M stage for RTS.
  • Be proactive and consider RTS as a tool for providing supply
  • Act more like system operator and not network maintainer and power purchaser
  • Be brought on board through a technical and financial support
  • AMI should be used which enables accurate data gathering and establish two-way communication channel
  • Smart meters should be used to mitigate several grid integration challenges like transients, flickers, voltage fluctuations etc.
  • Energy Storage system (ESS) can be used which helps in proper demand supply management.
  • Micro grid controllers should be used as it helps in management of solar variability and uncertainty.

Conclusion: One of the important aspect to reduce the impact of roof top solar integration is to think of protection system for reverse power flow as current protection system is designed for unidirectional power flow. Load flow study needs to be done so that deciding capacity of distribution transformer for rooftop solar system gets easier.

The successful implementation of net metering policy will be critical for solar roof-top to grow in commercial and industrial segment. Different steps are already being taken by government such as National Smart Grid Mission, National Energy Storage Mission is in planning stage.

Discoms must be brought on board through a technical and financial support package.  Policy interventions by MNRE such as offering rooftop solar power a higher Renewable Purchase Obligation (RPO) credit can incentivize the Discoms to fulfill more of their RPO requirement. Such steps will reduce the perceived investment risk associated with the sector. Its implementation and proper functioning will be the key to scale up roof top solar and achieve the target of 40GW by 2022.



Yamini Keche and Ashutosh Durselwar

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