Very well said !

Thanks Vivek... Do we have some readily available details about the Off River Closed loop PHES being planned in Indian Grid.

Okutataragi Pumped Storage Power Station might be a good exampler.

Thnaks David..

Yes Okutataragi Pumped Storage Power Station is a large PHES system with an installed capacity of around 2000 MW and with its Embankment dam located at Ichi River.

In my initial query possibly what I am enquiring is about Off River closed loop PHES. These could be of smaller capacity pumped storage plants have natural upper and lower reservoirs and once filled may need only make up water by way of mansoon water and or river tributeries etc. Due to minimal civil construction, they may not affect the natural surroundings and may have minimal gestation period during construction.

Definitely with off-peak surplus it is a very good option to pump back from lower reservoir to the higher one for deriving the benefits mentioned. But as it is a negative source of energy on net basis, like 900 MW generating but drawing 1,100 MW while in pumping mode, commercially it should be acceptable to the participants in the grid. Of course to some extent support of Solar Power may be supportive in the venture, as in the case of Purulia Pumped-Storage.

For the other issues mentioned some example may be seen by looking at the Article Trial Operation of Chukha Unit as Synchronous Motor

The main barrier is the recovery of capital cost ,PSP being a negative energy source ....

PSP renaissance can be traced to the nuclear plants to counter the steadiness of cheap nuclear generation .....

I believe EXISTING PHES is a potent option IF the operation of these could be optimized under the aegis of the national system operator. There are few GWs of it in India and any other form of storage notwithstanding the excitement around battery costs falling by the months, is miles away from it. It is not easy by any means but worth a shot. They are large (say min 300 MW size and ~2000 MWh - an order magnitude of larger than the largest battery at the moment), has inertia, well proven technology etc apart from being cheap with costs largely sunk.

NEW PHES even if we are talking about relatively cheap and smart design is a different story. Vast majority of the PHES were built in centralized planning era when the command and control system just made these available. There has been far fewer since the advent of markets as the business model of a negative energy option is still amiss even in fairly sophisticated markets. Australia for instance has a 5-min market including 8 categories of reserve with prices that can reach several thousand AUS dollar per MWh. However, even existing PHES is not doing terribly well - the reasons are complex and in fact there have been allegations that one of the big ones tend to withdraw generation precisely when its needed so that other thermals can make a killing. My point is not to refute the existence of a sane business model but there simply is not one at the moment YET and in India it is going to take some work to even bring the market design in line with a business model. I have scanned the literature and reflected on the Vietnam experience in this article:Preprint Commercial Realities of Pumped-Storage Plant Development: Re...

As Himalayan Glaciers rapidly recede , seasonal melts will likely reduce so there are some agricultural advantages too from higher level old river meander capture pondages of surplus wet season rainfall water runoff storage and be used in two reservoir pumped storage peak demandside management power recycling to maximise renewable energy harvests , eg daytime PV and wind . Such project cost evaluation in NPV terms likely needs multi partial budget inclusions to boot return incomes such as from agriculture need for water , and also consider climate changes advantages and disadvantages in long service life infrastructure projects for service lives of say 50 to 100 years ahead. Some Chinese agricultural flood water diversion run of river schemes go back 5000 years operation. It helps to talk widely for gathering all other cost benefits.

@ Subrata Mukhopadhyay - Thanks Sir for the inputs. You have very rightly pointed out, it is a negative source of energy on net basis - with a net loss of energy in the range of 15-20%. However with large penetartion of solar/wind energy in the grid, it is anticipated that at certain periods in the day, the energy may be almost of zero value and may have to be spilled. Hence with abundance of RE in the grid, negative source of energy may not be that imporatnt crieteria. However there may be host of other issues like large cost, gestation period and the mechanisem to channalise the produced energy in a most optimum manner.

@ Sushil Kumar Soonee - Thanks Sir for the inputs. The high capital cost and negative source of energy would be a major challenge. However under your guidance a number of new products and services are being added by the Grid Opeartors in the power sector and these (PHES) would definetly be able to play an imporatnt role in filling some of the voids. Regarding the cost and construction challenges, as I had indicated in my main query, the focus can be on small sizes, off-river closed loop systems, where the cost involvement, gestation period as well as effect on the environment may be comparitively less hostile.

@ Deb Chattopadhyay - Thanks Dr Deb for the inputs. Your message clearly encompasses the advantage of this technology over other storages as well as the challenges it has been facing.

The renewed discussion initaited on the subject is mailny in view of the large penetration of the RE in the Indian Grid and the ways and means required to balance RE energy as well as maintain the grid stabilty.

You must had observed that in the recent past a number of developments have taken place in the Indian Grid, which give way to the NLDC ( National Load Despatch Centre) to take corrective/optimising steps, in spite of de-centralised grid opeartion and control and these include RRAS ( Regulatory Reserve Ancillary Services), SCED (Security Constraint Economy Despatch) etc., . With all this it is almost certain that sources like PHES, if available in the grid can be optimally utilised once they are available.

The dicssuions on the 5 Minutes market in Indian Power system are alraedy under progress and with large RE penetration, some balancing sources of energy would definetly be essentatial. It is fully agreed and appreciated that it is also a costly proposition, particularly being a negative energy source. However if we compare this with other storage technologies, whether it is battery storage, compressed air and/or any other type, possibly in terms of cost as well as quantum it still may come out to be more competitive. But of course it also has associated challenges and we need to continously venture into these.

@David Eccles - Thanks Mr David for the contents. With the proposed large addition of the RE to the Indian Grid all possible avanues which may provide balancing and stabilty to the grid are being explored and PHES is also a possible candidate towards this.

Just wanted to add a point here that the connection between RE variability and storage in general (much less a specific storage technology within it) is a bit overstated everywhere. We have effectively created an overload of RE a bit too early through expensive FiT and now we want storage because we have the overload! There is a need to face some of these humbling truths even before we get onto the need for storage because rejection of super expensive RE may not necessarily be a bad idea. Surely, in the last 1+ years we have reached a different price point on solar and wind and they ought to be part of the mix on their own without any subsidy (except perhaps rooftop solar).

Secondly, there is a lot of flexibility inherent in a system that ought to be captured first. Storage hydro can and should be operated differently. Thermal plants have a lot of flexibility too that does not meet the eye simply because they have been operated in a very different way. Storage has to be the last option given their cost. And we need not be fixated on storage of a specific type a priori. Let an unbiased analysis state if the solution should be large point source like a PHES unit (min 300 MW) or more modular battery storage.

Finally, the intra-day variability that PHES can take care of is only part of the RE variability. There are other issues that are important if not more important to do with seasonal and inter-annual variability. A power system needs to be deal with the low wind period in April/May prior to monsoon, low solar availability during the monsoon and surprisingly large swings in availability in some years relative to others. The system needs not so much storage but back-up generation (e.g., OCGT) to deal with these which also affects the need for intra-day storage.

Yes Dr Deb, I cannot agree with you more to what you have said. Of-course there may be numerous reasons towards pushing RE into the Indian Grid, however from a grid operators’ experience what I can state confidently is that in addition to address sustainability angle, it has brought a number of supporting measures to the Grid, which were pending since long and were not moving.

Regarding the other compulsions, like storage etc., though lot of discussions/ advocacies may be there, however I feel that so far Indian Utilities have moved with caution and the first grid connected 10 MW capacity battery storage plant has been brought only very recently by Tata’s in Delhi (under NDPL) . On the other hand, under the compulsion of Renewables, the different grid friendly actions, which have been pushed and realised include, enhancing flexibility of thermal generation by bringing the minimum operating level up to 50%, instead of 70-80% earlier, allowing RRAS in the grid by regulators - which were pending since long and bringing the renewables under scheduling domain. It is only due to all above measures, that no sustained spillage/rejection of RE has been observed so far, without having any major expenditure towards the expansive solutions like storage etc.

However one another thing what we have to consider particularly with reference to Indian Grid is that such a large interconnected/synchronous grid is being operated and frequency and other parameters are being maintained in such a close range, without having certain basics in place, like primary and secondary controls in the system. Hence when there is a talk of storage systems etc. in the grid, solely it may not be due to the reasons of renewables, but taking into consideration all above situations in the grid. However as in the face of Renewables, getting anything pushed/implemented is relatively softer, the newer actions like addition of storage etc. are ovbiously/conveniently linked with renewables.

Thank you for your comments. There are definitely a lot of good measures being put in place including ancillary services that are essential for a modern power system and incidentally they would also help to create a business model for storage. If renewables foster these developments, so be it! One interesting development has been to repurpose old and unprofitable coal units into all sorts of things including a PSP in Germany, synchronous condensers in various places including the USA and solar/wind site too. USA, India and China might at some stage will follow the example of UK and the interesting thought is that these coal plants may well become RE and Flexibility (RE+FLEX) centers! I have written a blog on the topic which I will share on my page soon.

Ok Sure Dr Deb..shall look for the blog..

Simply, It (HPS) is recomended if you have periodic tarrif and a considrable diffirience between peak an off peak demand .

Pumped storage plants are the best ramp capability sources. They can be in generation and motoring mode...generation mode enhances system up ramp capability and motoring mode enhances down ramp capability. So we have to increase number of such plants in our grid to support the planned 175 GW renewables. And there should be more research to improve the cycle efficiency of such plants..