Going green in a big way: A carbon-free electricity grid for Tamil Nadu

Our electricity grid is the most complex machine in the world. It connects millions of homes, offices and industries, their appliances and machines, and the power producing generators into a single and interconnected system. The electricity grid is also one of the major contributors to greenhouse gas emissions. In the case of Tamil Nadu’s grid, about 70% of its electricity comes from coal power plants. Curiously the electricity sector is also deemed by sector experts as one of the easiest sectors to be decarbonised. 

The Internet of Things (IoT), cheap renewables, the falling cost of energy storage solutions, and the advent of the Prosumer (the consuming-producer) are revolutionising the way our electricity grid is managed. The electricity sector is undergoing a fundamental transition, and while some utilities have realised the emerging opportunities of this transition and actively accelerate the same, others are holding on to the past and thereby compromising the future of all. The US, for example, has announced a carbon-free electricity grid by 2035. Great Britain is even more ambitious as it is on track to achieve a zero-emission grid by 2025. 

Technological advances enable us to power an electricity grid that is 100% carbon-free. The advent of the prosumer, the producing consumer, introduces distributed energy resources such as rooftop solar and behind-the-meter energy storage systems and has the potential to democratise the ownership of power generation assets. Instead of having a single large power generation plant at a remote location, every roof can have its own electricity generation system. After all, the sun shines on all roofs and is a distributed energy source. 

While Tamil Nadu was India’s poster child for renewable energy, it has lost its leadership position in recent years, it has not met its Renewable Energy Purchase Obligations for consecutive years and is planning to add 6.50 GW of new coal power plants to its generation fleet. How can Tamil Nadu get back on the map as a renewable energy leader? 

There are no technical or economical barriers to an electricity grid that is powered by 100 percent renewable energy at a low cost. A recent study by researchers from Stanford University, encompassing 20 world regions and 139 countries developed roadmaps for transitioning 139 countries to 100 percent clean, renewable energy by 2050 with 80 percent of that transition completed by 2030. If there are no technical or economic barriers for a carbon-free grid, the barrier remaining is the perception of grid operators and policymakers that it is too hard to keep the lights on with variable renewable energy. Setting a target for a carbon free electricity grid can address this barrier. A clear target will mobilise all stakeholders, align policy and planning, and attract investments. 

3.10 GW of the State’s coal power plants are 20 years and older and are approaching their end of their lifetime. The plants are the least efficient and most polluting ones and are not meeting the air and water emission norms notified by the Ministry of Environment, Forests, and Climate Change. Retrofitting these plants to meet these norms would come at a high cost and would lead to an increase in electricity tariffs. 

In addition, there is currently 6.50 GW of new coal power plants under various implementation stages. 3 GW of new coal power plants are nearing completion and another 3.50 GW is in the early stages of construction. As per IPCC, all coal power plants will need to be phased out by 2040 to stay below the 1.5 Celsius global warming scenario. Completing the construction of all of these new coal power plants would require a more rapid and costly move to less-emitting sources in the near future. A cost-benefit analysis including options to repurpose or retrofit the old and new coal power plants would provide greater clarity on the need and cost of these. Germany for example has started to retrofit its old cold power plants into molten salt energy storage systems. In such a retrofit, most of the existing infrastructure assets for the coal power plants can be utilised, making it an economically viable solution, and providing the much needed energy supply flexibility for higher integration for renewables. 

Tamil Nadu is endowed with one of the best wind and solar sites in India. The State’s solar energy potential is 17 GW, and its wind generation potential is 103 GW. The wind potential includes 68 GW of onshore wind potential and 35 GW of offshore wind potential. This combined potential is more than sufficient to make Tamil Nadu’s electricity grid carbon-free. As of May 2021, the State has an installed wind capacity of 8.52 GW and an installed solar capacity of 4 GW, combined this equals 12 percent of the States total renewable energy potential. Tamil Nadu has also the opportunity to supply surplus renewable energy to other States or to Sri Lanka, provided that adequate network capacity is in place for the evacuation of wind energy. Enhancement and upgradation of the transmission infrastructure to harvest the State’s renewables potential will make Tamil Nadu a global renewable energy powerhouse. 

Tamil Nadu’s electrical energy consumption is expected to double by 2030 as compared to 2020 values. The increase in demand will require the enhancement of the distribution network. At the same time, the distribution network management mode will change from a passive management system (fit and forget) with a unidirectional energy flow, to an ICT enabled and active management system with a bi-directional energy flow. Distributed energy resources, such as rooftop solar, and consumer energy storage systems will play an increasingly important role, increase energy security, and provide essential grid management services. Instead of actively resisting this change, TANGEDCO will need to develop innovative systems to manage the injection of variable renewable power by millions of consumers. 

To facilitate higher integration of variable renewable energy sources, grid flexibility services will be essential. Active and passive demand response programs, energy storage and flexible generation sources can provide multiple services from strengthening grid integration of renewables, to time shifting of energy, to providing capacity adequacy and services such as frequency and voltage support. This requires more dynamic energy tariffs, tariffs that vary with the time of the day and by season. It will also require a legal framework for third parties to aggregate distributed energy resources from individual prosumers, such as battery storage systems, into a virtual power plant. Such a virtual power plant will provide essential reliability services and help us keep the lights on. 

The technology solutions for the State’s carbon-free electricity grid are available, the cost economics support such a transition, and the global warming threat does not provide an alternative anyway. What is needed is the collective and political will to set a carbon free electricity grid target, align key players in the energy sector and develop implementation plans to achieve the target.