By Jason Deign
Doubts over the strength of the grid have called into question a USD$17.2bn plan to build 10GW of pumped hydro storage in India.
Central Electricity Authority chairman SD Dubey unveiled the five-to-six-year pumped hydro programme last month.
The administration would be adopting pumped hydro to store excess power from India’s growing renewable energy sector because the storage medium is cheaper than batteries, he said.
But being able to store energy in pumped hydro reserves depends upon getting it to the dams in the first place.
And observers have questioned whether India’s grid is up to the task, particularly since it is already groaning under the impact of solar energy.
Curtailing solar power
Last week, for instance, reports surfaced of the Tamil Nadu Generation and Distribution Corporation (Tangedco) curtailing solar power because the grid could not cope.
“The Tamil Nadu Electricity Regulatory Commission has asked the Tamil Nadu Generation and Distribution Corporation to technically justify why it asks solar power plants to back down from the grid,” The Hindu Business Line reported.
“Tangedco argued that it had only asked solar plants to back down when grid stability was affected,” said the report.
“Recently, the Solar Power Developers Association had also written to the MNRE [Ministry of New and Renewable Energy] and Tangedco expressing concern over 50-100% ‘generation curtailment’ during peak generation periods.”
The weakness of India’s grid could end up being a powerful argument for installing distributed battery storage instead of relying on large pumped hydro projects, said a respected Indian energy analyst.
“Pumped storage will be idling”
“For pumped storage, the power generated from solar plants has to be first evacuated to the grid, after which it can be converted to hydraulic head,” said Madhavan Nampoothiri, founder and director of RESolve Energy Consultants.
“In a country like India, where the ‘backing down’ happens because the grid infrastructure is not sufficient, pumped storage will be idling since this solar power is getting wasted and not reaching the grid in the first place.”
In contrast, he noted: “Battery storage can be sited within the solar power plant. In case of in-situ storage, the power can be stored in the battery during peak hours, and gradually evacuated when the grid can handle it.
“In this sense, battery storage has a distinct advantage over pumped storage, as long as evacuation constraints remain.”
Pumped hydro has several other apparent disadvantages compared to batteries. The first is that it is highly location-specific.
Suited to the mountainous northeast
From a purely geographical perspective it would seem pumped hydro would be most suited to the mountainous northeast of the country.
This would potentially put it some distance away from India’s top solar and wind resource areas in the west and south, exacerbating the stress on the national grid.
Such distances could also lead to major transmission losses, reducing round-trip efficiency.
Even assuming a solid grid and relatively low transmission losses, however, the fact remains that the capital costs for pumped hydro are currently about as low as they will get, while batteries are predicted to get significantly cheaper.
In particular, the second-life battery effect is expected to slash the cost of lithium-ion batteries significantly in the next three or four years. And India has the world’s biggest lithium-ion battery right on its doorstep, in China.
Cheap second-life batteries
Given the scale of lithium-ion production in China it is entirely likely the Indian market could soon be swamped with cheap second-life batteries from its northern neighbour.
How far second-life products could eventually decrease the cost of batteries remains to be seen, of course.
However, it is possible that in a couple of years battery costs in India could reach a level that makes solar-plus-storage a option not just for plant owners wanting to avoid curtailment but also for industrial and commercial-scale users.
If this happens, batteries could easily pull ahead of pumped hydro as a large-scale storage medium since the planning, permitting and construction process for battery plants is potentially much easier than that for reservoirs and pipes.
Given this mid-term outlook, there are good reasons to suspect that India’s big plans for pumped hydro could end up joining a list of other major development programmes the country has failed to bring to fruition.
The main difference between this and grand schemes such as India’s national broadband rollout is that if it fails then at least there might be an alternative that allows the country to still enjoy the benefits.