The difficulty with renewables
The difficulty with renewables


By Somit Dasgupta

India’s push towards decarbonisation has to be backed with adequate storage facilities, without which it clearly cannot go forward beyond a point. This is because of two reasons. The first is that the storage will handle the intermittency problem (due to sudden cloud cover or drop in wind velocity) of renewables. Second, coal-based generation cannot be phased out till such time as we can rely on stored energy to provide electricity in the non-solar hours.

As of now, we are not feeling the pinch because we have more than 200 GW of coal-based capacity and are managing the show by backing down these stations when required. The Central Electricity Regulatory Commission (CERC) recognises 55 per cent as the technical minimum — which means that a 1,000 MW plant can run at 550 MW. The additional operating cost for running the plant at 55 per cent capacity (on account of higher auxiliary consumption or self-consumption by the generating plant amongst others) is allowed by the CERC as legitimate expenditure and hence, is reflected in the generation tariff.

Efforts are on right now to ascertain whether the technical minimum can be further brought down to 40 per cent. Of course, all this requires a detailed study in consultation with the original equipment manufacturers to assess the loss of life to these machines, if any, by operating at such low capacities.

When India’s renewable capacity goes up further and assuming that they “must run” so that solar and wind energy is not wasted, coal-based capacity may need to go below the technical minimum, which is not feasible. At this point, some of the coal-based units would generate at the technical minimum and the extra renewable energy (over and above what is required by the grid) would be used to charge the batteries. This stored energy could then be used to supply electricity during the non-solar hours, especially in a situation where the coal-based generating units would be phased out gradually to enable us to become net zero by 2070. However, some minimum coal-based generation would still be required for meeting a part of the base load and one has to rely on the available carbon sinks to neutralise the carbon dioxide emissions.

How much should the minimum coal-based generation be? How much storage capacity we need to maintain depends upon a lot of factors like the demand for power existing at that point in time, the shape of the load curve, the cost of generation from each source, and cost of batteries.

Now, what are the storage options before us? One usually speaks of hydrogen-based storage, lithium-ion batteries and pump storage plants. As far as hydrogen storage is concerned, it is found to be feasible for long-term storage, meaning across seasons. One can use this stored energy, for example, in situations when coal mining goes down (which happens during monsoons) affecting thermal generation or when hydro generation depletes due to low reservoir levels etc. For day-to-day storage and dissipation, batteries are still the ideal source. Though the cost of batteries has declined by about 80 per cent over the last decade, it is still quite expensive as the levelised cost of a battery is about Rs 8 to Rs 10 per unit. Moreover, the pace of decline in the cost of batteries has reached a plateau and in fact, has started rising. This happened for the first time since 2010, due to an increase in the cost of lithium and battery components.

Coming to pump storage plants, India has a total capacity of about 4.7 GW (out of a worldwide capacity of 169 GW, China alone accounting for about 32 GW) but only 3.3 GW is functional. Though a survey of the CEA estimated a pump storage potential of about 100 GW, it is not clear how much of this will pass the environmental test. The actual potential could turn out to be much less. Pump storage plants have not really grown in India due to several factors, including high investment costs, long gestation periods, non-remunerative pricing models and lack of adequate sites having the topography that is required for operating a pump storage plant.

Besides, India’s expertise in pump storage plants is somewhat suspect with the Tehri pump storage project yet to be commissioned though construction began in 2011 and was to be completed in four and a half years!

With batteries and pump storage options facing hurdles, India’s growth in renewable capacity is likely to hit a roadblock after some time due to inadequate storage capacity. We would not be able to phase out our coal-based generation and would need thermal support during the non-solar hours. Incidentally, storage will not be our only roadblock.

The financial condition of our distribution companies (discoms) will be another hindrance. The additional solar and wind capacity has to come from the private sector and no developer is going to come forward unless there is some credible payment security mechanism. Problems with land acquisition, and securing the right of way for laying down transmission lines will also continue to hinder progress.

To sum up, the lack of storage capacity is likely to affect our resolve to go net zero by 2070 unless battery costs go down in the years to come. Batteries, incidentally, will not only adversely affect phasing out our coal-based generation but will also affect the pace of introducing electric vehicles (EVs) since batteries account for about 30 to 40 per cent of the cost of EVs.

The target of having 500 GW of non-fossil generating capacity by 2030 may sound impressive but may prove to be elusive unless we can enhance our storage capacity through not only batteries but also pump storage plants.

[The writer is senior visitng fellow, ICRIER and former member (Economic & Commercial), CEA.]