No batteries required: pumped hydro for solar energy storage

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Kidson Pumped Hydro Project

                                        Kidson Pumped Hydro Project

With the change-over from centralised fossil fuel power to distributed renewable energy, there is intense interest in battery storage to cope with intermittency of solar PV and wind power. There is no doubt that batteries will have a major part in the transition. Apart from flow batteries, however, the opportunities for multiple-hour storage and discharge at scale over a period of hours is still unresolved. It is implemented for cars and household storage and indeed the first steps to access power stored in the batteries of Electric Vehicles have already been taken.

The interesting thing about accessing EV batteries by the grid, is that the capital costs of these batteries have already been covered to provide transport. Hence the storage costs involve only accelerated wear and tear on the batteries which occurs when charging and accessing power (whether at home or wherever the vehicle gets connected to the grid). The amount of power available from a fully implemented EV program is astonishing. This is not yet realised as there are not enough EVs. Furthermore, the technology for accessing and managing this power is not yet implemented.

There is a complementary energy storage system that is well established globally, with ~143GW of storage currently accessed in 40 countries. This power can handle massive capacity requirements and also allows seasonal storage. This is pumped hydro and it is attractive because it involves recycling of water between adjacent upper and lower reservoirs which have a substantial height differential. The cycle efficiency of modern pumped hydro is ~80 per cent, which compares favourably with CCGT (Combined Cycle Gas Turbine) cycle efficiency of 30-60 per cent.

Most of these facilities involve flow-through water (i.e. they involve damming waterways); these were essentially all built more than 25 years ago.

Pumped hydro can also involve cycling between two storage systems that are not connected to a waterway. New generation reversible pumps/generators simplify the engineering and capital costs. Also variable speed pumps allow great flexibility in power capture/generation. Business models for implementing this type of storage are somewhat limited at this time.

hydro 2

Schematic for pumped hydro

Here I review an example of a corporate play in this space. It involves a small company listed on the Australian Stock Exchange, and gives a flavour of how this emerging industry might play out.
I also make some comments about what is happening around the world.

Genex Power (ASX:GNX) Kidson project

Australia has three well-established pumped hydro facilities: Tumut 3 in NSW (0.6GW), Wivenhoe in Queensland (0.5GW) and Shoalhaven in NSW (0.24GW). Genex Power plans to build the fourth significant pumped hydro project in Australia.

As envisaged when the company listed on the ASX in July 2015, the plan was to develop a 330MW pumped hydro project on the old Kidston gold mine, involving water transfer between two pits at different altitudes. Queensland is a good place to develop such a project as peaking power is primarily provided by gas turbine generators. With substantial increases in gas prices expected, this makes the project financially interesting.

The transactions involved in setting up the company for ASX listing are complex. The Kidston mine and associated infrastructure were acquired from the world’s largest gold miner, Barrick Gold Corporation (NYSE:ABX). There is a 20GL dam, which was built to service the mine, 18km away. The Kidston project owns piping between the dam and the mine and it has water rights of 4.6GL annually should there be a drought.

The basic plan was to connect two dams which are located at ~190 metres vertically from each other. The initial plan involved 3 x 110MW reversible pumps, which will pump water from below to the top dam when there is excess power, or generate electricity via water from the top dam entering the lower dam. There is already a 132kV transmission line providing connection to the North Queensland grid and this will be enhanced with a further 275kV line.

There is also a planned 50MW solar PV farm, and this will be the highest quality solar resource in Australia, with strong community support. A binding agreement with Ergon Energy has been announced for power uptake. The planning for the solar PV farm in the old tailings area, can now proceed with the certainty that the power produced is sold into the grid and there is the possibility of extending this solar PV farm to 150MW.

The existing 132kV line from Townsville to Kidston means that no augmentation of the infrastructure power lines will be needed to service the solar PV project. The solar aspect of the project is advancing rapidly, as Genex has very recently entered into a debt-funding mandate with Societe Generale, which will cover most of the funds required for the project. Equity and grant funding through ARENA is actively being explored to cover the gap from financing provided through the Societe Generale agreement. Genex plans to commence construction of the solar facility in late 2016 and to generate first cash flow within 12 months of construction commencement (i.e. in 2017).

The close relationship between a solar PV farm and a pumped hydro project in the Genex business model is reminiscent of combined solar park/hydro facilities in China and Chile. Many pumped hydro projects are located in rugged terrain that is not suitable for solar farms, so the Kidston project is unusual in having elevation difference combined with a flat tailings area close by.

Since listing on the ASX last July, the pumped hydro project has developed significantly due to involvement of a key investor in the project, HydroChina, one of the largest hydro electrical and mechanical equipment manufacturers in China. HydroChina has a 3GW hydro equipment manufacturing capacity annually and it has installed 200 medium and large-scale turbine generators in 20 countries. It is a top three hydro equipment and service supplier (along with GE-Alstom and Andritz).

Experienced hydro consulting group Entura, which is owned by Hydro Tasmania, has been involved in consulting on project development, with really interesting results. The upshot is that a revised plan will deliver not 330MW (1.65 GWh) of power storage, but up to 450MW for 5 hours (2.2 GWh) depending on the final configuration. This involves building a new upper storage facility that is 35-40 metres higher than the originally envisaged facility, making the vertical drop 225-230 metres.

The new dam will be a cheap “turkey nest” construction that is lined to prevent seepage. A turkey nest dam is cheap to construct as it is shallow (5 metre depth), but has large capacity due to covering a large flat area. The cost of building 5 metre walls is dramatically different to a conventional dam construction where the water pressure of an elevated wall means substantial construction costs. An additional advantage of the revised plan is that less concrete is required due to the proximity between the new upper and lower dams. The plan also leaves an existing dam for storing excess water and for flood mitigation.

A critical issue for a pumped hydro project is that the project has strong state and federal Government support. ~$A2 million has been advanced through convertible notes to ARENA (Australian Renewable Energy Agency) towards the cost of the pumped hydro feasibility study. The project has been given “State Prescribed Project” designation and this has facilitated discussions with various Queensland government departments in the development phase. The solar PV aspect of the project already has environmental approval to proceed.

Of considerable interest is that Genex has identified as many as 12 other mining sites around Australia that may allow pumped hydro projects based on former mines. Of course each location has specific conditions that need to be addressed, so no single project is easily replicated. However there is no doubt that the experience of completing a major project of this type builds a knowledge base to take on additional projects.

So the Kidston site is a proof of concept that can probably be replicated. The scale of these storage opportunities suggests that if a funding model can be sorted out, pumped hydro can offer a substantial and complementary energy balancing opportunity to battery storage. There is a substantial report (2014) from the University of Melbourne Energy Institute detailing pumped hydro opportunities in Australia. This references a ROAM (2012) report which started with 100,000 potential sites and identified 68 sites for detailed analysis (53 freshwater and 15 seawater sites).

Identifying a site which is basically set-up, and using the best engineers to scope out the project, the Genex facility looks like it will be substantially cheaper than the generally accepted construction costs of $US1.5-2.5 million for 1MW storage capacity (assuming large capacity of ~1GW). If the Genex project is now an up to 450MW (instead of a 330MW) project that will cost ~$A300 million, this looks like a very cost-effective pumped hydro project, costing ~$US0.5 million/MW. Note that the construction cost includes an additional 275 kV line to the grid. Genex’s goal is to complete the feasibility study for the pumped hydro facility in Q3 2016 and to begin power storage in 2019.

Pumped hydro in Europe

The first pumped hydro systems were installed in alpine Switzerland, Austria and Italy in the 1890’s.

As one has come to expect from Europe in the renewable energy space, there has been substantial work done on assessing prospective sites for substantial pumped hydro power facilities.

A recent European Commission project addressed economically viable solutions to support large scale integration of intermittent renewable energy production into the EU electricity grid. The detailed 2016 report on pumped hydro storage identified paired water masses that were close together and separated by sufficient height to make substantial power storage and generation feasible (at least 1 GWh) in EU-15 countries, plus Norway and Switzerland. The report is thorough and has been prepared with significant industry input. No realisable pairs were found in Denmark, Ireland, Luxembourg or the Netherlands. Only one or two pairs were defined in Belgium, Finland, Germany and Greece, due to insufficient slope (head divided by distance between the water bodies).

The report identified 6,924 GWh of substantial (more than 1 GWh storage) theoretical new pumped hydro power storage available in Europe, of which 2,291 GWh was classified as realisable potential. There were 714 paired water bodies identified as theoretically feasible, with 117 being chosen as realisable.

The grounds for defining realisable potential varied between countries, including issues concerning permitting and the granting of concessions. Decisions for inclusion included a combination of computer modelling and input from national hydro experts.

Note that the report only addresses situations where both water bodies already exist and therefore excludes situations where a second water body needs to be built. Notably this means opportunities where the sea might be one water body are excluded.

Unfortunately the most prospective pumped hydro regions in Norway, the Alps and the Pyrenees did not coincide with locations of major power generation or power requirement . However, the report notes that Europe’s interconnected market allows power to be distributed between countries.

The report indicates that the pumped hydro storage identified is 7 times current installed European pumped hydro capacity and is equivalent to 95 million lithium ion batteries of the size used for electric vehicles. Three areas comprise 72% of the potential capacity : 54% Southern Norway; 13% The Alps (Austria, France, Italy, Switzerland, Germany); 5% the Pyrenees (France & Spain).

Since these sites are prospective it allows current best practice to be implemented, most notably this would involve use of variable speed reversible pumps/generators.

What is happening in the US?

While there are 40 pumped hydro facilities in the US, which provide 22GW of power storage, virtually all of this capacity was built more than 25 years ago. For example, Duke Energy (NYSE:DUK) has two substantial pumped hydro facilities, Bad Creek (1.06GW, commercial 1991) and Jocassee (0.71GW, commercial 1973), both in South Carolina.

In recent years, damming natural waters has become essentially impossible. However the realisation that burgeoning solar PV and wind power needed balancing has meant a resurgence of interest in pumped hydro; there are now 60 pumped hydro projects involving 51GW of power in the FERC (Federal Energy Regulatory Commission) queue for licensing and permitting.

Two large-scale opportunities (both in California) have permits and these have been under development for a very long time; they are struggling to raise capital. In fact there is doubt that either will proceed. Sourcing water to provide initial water supply and then annual replacement for seepage and evaporation are critical issues for these projects in California, which is experiencing a long-term drought.

There is a project starting out on the FERC approval process, Gordon Butte Pumped Storage based in Montana, that seems quite similar to the Genex project, although Gordon Butte uses a natural geological feature rather than an old mine.

Gordon Butte Pumped Storage will be located on private land. It is a closed loop facility that will access water from a nearby irrigation system, so (apart from denying water to irrigators, who presumably will be paid) the water source is not controversial. The head of water is ~300 metres and the dams will be connected by a steel-lined underground concrete shaft. The project requires 4000 acre feet of water to fill the lower dam and then ~400 acre feet of water annually to replenish water lost by evaporation and seepage. The facility will have 400MW/~3.6GWh installed capacity and an annual power supply/consumption of up to 1,300 GWh.

Major turbine manufacturer Alstom will supply the variable reversible pump/generators and the facility will be able to deliver power within seconds. Smart hydraulic short circuit pump technology, with pump and generator operating in the same shaft rotating in the same direction, will allow the system to pump water upwards and at the same time generate power. This will allow rapid balancing of renewable power, as well as increasing grid stability in Montana. This will be the first hydraulic short circuit pump installed in the US.


Japan’s Okinawa Yanbaru pumped hydro facility, built in 1999, is the world’s first system that uses sea water as the lower reservoir. It is small (30MW) and the water head is 150 metres. (How far this technology has moved is indicated by recent environmental approval in Chile for a 300MW facility with 600 metre head that has received environmental approvals and construction is planned to be completed in 2020. Like the Genex project, it will be coupled with a 600 MW solar PV facility.)

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Japanese Okinawa Yanbaru pumped hydro facility

Japan had the world’s largest installed pumped hydro capacity of 27.4GW in 2014.


China, with 21.5 GW pumped hydro, eclipsed the US (20.9 GW) in 2014.

While China only installed 1.2GW of pumped hydro storage in 2015 (compared with 18.2 GW of conventional hydro power added), interesting things are happening in coupling hydro power with renewable energy. In 2015 China implemented the second phase of its 850 MW Longyangxia solar park by coupling the power generation directly to one of four turbines at a nearby 1,280MW hydropower station. The advanced controls on the hydro turbine allowed variable solar power supply to be dispatched as firm power to the grid.

China plans to have 100 GW pumped hydro by 2025!


Like much of the renewable energy transition, finding appropriate business models to enable this major transition is not straightforward. This isn’t a problem for a ‘command and control’ economy, and so China is powering on. Well-planned economies like Europe and Japan also have pumped hydro strategies well in hand. In the US there are still not clear investment opportunities for pumped hydro storage currently, but in free enterprise US there are a number of major projects emerging. Perhaps the coupling of solar PV (or wind) with pumped hydro is the way this will play out. Australian company Genex is an interesting example.

This article stems from my research on the latest developments in the Genex project. I liked what I saw so much that I recently bought some shares. So I declare an interest in Genex Power.

Keith Williams AM FTSE is an AgScientist/Biochemist proteomics pioneer who has been involved in the biotech industry for 30 years, with experience in startups and ASX listing. He is focused on how business/technology can help address climate change and drive energy transitions. 


  • Cooma Doug

    Large pump storage was used to enable coal stations to remain in service in low loads. Coal generating at 30% efficiency then the energy stored and returned via further pump/gen losses to some terrible filthy efficiency number.
    This is perhaps the dirtiest thing we could do in a large fossil fuel base load system. It is a no brainer.

    The solution is already available and involves a prioritised process of load management.
    As the load falls remove all fossil fuel generation .
    When we run out of fossil fuel gens on line we store and smart switch on the load side of the meter.
    The problem with large hydro pump storage is the retention of infrastructure that could be avoided.
    The other issue is that in the transition to renewables the market forces are stacked against management of low loads via large pump storage.
    On smaller islanded systems where pump storage can be implemented, I cant see how smart switched loadside and batteries is not a clear winner.
    At the moment I pay 10 times the money that the generators get for generating my power. I believe large scale pump storage solutions would sustain this money puzzle
    for us.

    • David Hall

      Isn’t energy storage, energy storage whether it is by batteries or molten salt or pumped storage? If pumped storage provides a cost effective means to supplement solar PV when the sun isn’t shining, why not have it?

      • Cooma Doug

        It’s all about the nature of the market, what energy is potentially worth and the distance from the user.
        There is a difference between peaking load management and smart switching batteries and efficiency on the load side.
        Peaking profiles are going to vanish with the coal gens.

        Pump storage is similar to batteries and clean as long as it isnt pumping fossil energy. But it is in the wrong location, on the wrong side of the meter when solar is distributed across the nation in the future.

        Large pump storage is a wonderful support for a base load grid when pollution is ignored and there is virtually zero load side management. For the future energy system it will not be a viable investment.

        • Ian

          Ignoring costs, any type of electricity storage is good. It has a number of functions and matching demand with supply is one of them. As you say, previously the constant generation of coal power required pumped hydro to match the variable load. Well not much will change in a purely renewables supplied grid. There will still be a mismatch between supply and demand. Hydro storage will still be an option. The question is will it be a viable option ? Behind the meter storage does not have a grid cost but is not very cheap. One can have a crack at estimating pumped hydro costs plus grid distribution costs to check its viability. Until we have the data for each storage method’s costs our preferences will just be random guesses.

          Maybe Giles or Sophie can enlighten us on a cost comparison between behind the meter battery storage versus pumped hydro. We already have examples of both types. How does that compare with gas peaker plants ?

          • Cooma Doug

            A battery can be discharged at say 3 times it’s rating within milli seconds of a frequency trigger. This makes a gas peaker that takes 2 min to reach max output look a bit ordinary especially when located on the other side of the meter.

            You must also realise that storage happens in other ways and emerges in the new technology options on the load side. The battery discharge is the last option on the load side after other technology options. In the pump storage solution there is just one option.

            The water in a dam is the same as the energy in a battery to some extent. But it requires response times in minutes rather then milli seconds and for this reason there are few opportunities to discriminate.

            The rapid load side response options, initiated in milli seconds, virtually divides the network into individual load response/frequency islands and provides discrimination.

          • Bob_Wallace

            Batteries are likely to be the most economical choice for frequent cycling (storing for 1 – 3 days) but expensive for “deep storage”.

            PuHS can do frequent cycling, earning money, plus store lots of energy for longer periods of low wind/solar input at a low cost. The same is true of flow batteries which can store their chemicals in large unpressurized tanks. (No longer used petroleum tanks?)

            We’ll probably need some of both. When we hit a period of low wind/solar then start pulling from the PuHS or flow batteries 24 hours a day. When demand is low (late at night) then use the extra coming out of deep storage to refill short cycle storage for peak demand use.

            Secretary Chu (previous US Secretary of Energy) said that PuHS costs about $0.10/kWh. Frequent cycle battery storage should drop below $0.03/kWh as batteries move to larger scale.

            Cost of storage with batteries = total annual cost / number of kWh stored and sold per year. If batteries are cycled only a couple of times a year the cost per kWh becomes very expensive.

  • Ian

    Given the efficiencies, capital costs and projected lifetime of such a project, what is the cost of storing electricity for the kidson project? We know that once through hydro in Tasmania costs roughly $50/MWH wholesale, wind farms $80/ MWH, the FiT for distributed solar $50 to $60/MWH, lithium batteries storage costs approximately $400/MWH (40c/KWH). Before we can get a real sense of what different types of storage and standby gas generation cost we cannot fully appreciate these sorts of projects.

    Once through hydro is intrinsically cheaper than pumped storage and can be utilised so much more effectively by increasing the peak output for a shorter period of time. Tasmania, Victoria, South Australia and New South Wales have a large storage resource that is the once through hydro in Tasmania and the Snowy Mountains. This can be utilised very intermittently for peak shaving and after hours power generation. For the sake of illustration 1GW of continuous hydro is equal in water use to 4GW of hydro over 6 hours per day. If you’re worried about a surge in water flows in the downstream part of the system then a small tailgate dam would suffice to smooth the water flow. Freeing up hydro for its dispatchability would allow a lot more solar and wind generation to be installed and would allow proper pricing and reward for hydro’s capacity function. A proper price signal could be sent to hydro operators. When wind and solar output is high pay hydro a depressed fee and when wind and solar is scarce reward hydro a generous fee in the usual manner. Also encourage the use of hydro purely for its dispatchability with capacity payments – similar to those offered to gas generators. Any capacity payment can be linked to the storage capacity of the dam. 100% full 100% capacity payment 10% full 10% capacity payment.

    One way to recognise hydro’s storage function is to structure tariffs for solar households and businesses around the concept of grid storage. For instance a solar household could buy ‘grid storage’ the grid could emulate and compete with battery storage. IE, a household might pay for 10 KWH of storage and up load to and down load from this up to their 10KWH limit as much as they want. Any excess export or import would revert to the usual FIT or import tariff. In the day the household could ‘store’ 10KWH and at night use 10KWH. The only cost to them is the monthly storage rental. Export more than your accumulative limit and the FiT is 5c/ KWH.Import more than what you have stored and the cost is 26c/KWH. The cost of the ‘storage’ product would need to be competitive with actual battery storage and cheaper than the usual FiT plus import. A figure of $30 to $40 per month would be a reasonable starting point.

    • KenFabos

      Yes, it doesn’t require purpose made pumped storage for hydro to find opportunities as backup to renewables – flows held back by any hydro during the sunny and windy times will be worth much more outside them and it will be a no-brainer to take advantage of the ongoing transformation of our energy supply. Wind, solar and hydro add up to a powerful combination.

      • Miles Harding

        Tell that to the Tasmanians who managed to squander their stored hydro in the pursuit of quick profits.
        The dam walls are perfectly visible form both sides, maybe we can stand a few of those very clever executives in front of them.

  • Pumped-storage hydro for solar or wind energy “allows seasonal storage” aplenty considering that the gravitational potential energy naturally stored in Lake Titicaca (Peru / Bolivia) with respect to sea level is more than the electrical energy generated in the US in one year.

    Water masses not so “close together” can still be feasibly paired for pumped-storage using power canals, as per my design for a proposed up to 6,800 GWh “Strathdearn Pumped-Storage Hydro Scheme” in the Scottish Highlands which pairs a new build reservoir with the sea.

  • solarguy

    I have always liked the idea of pumped hydro, but what is the median cost built? Molten salt storage currently cost $134/kw built. It can be put in places that you can’t cost effectively build p/hydro or the terrain isn’t right. Molten salt tanks can store heat for 60 days easy without any further energy input, as they only lose 1 degree F per day.

    • john

      From the article { If the Genex project is now an up to 450MW (instead of a 330MW) project that will cost ~$A300 million, this looks like a very cost-effective pumped hydro project, costing ~$US0.5 million/MW }

      The articles also had generally accepted cost of { $US1.5-2.5 million for 1MW storage capacity }

      So it would appear this project is below previous build figures helped no doubt by the existing 132 kV power line connector.
      { Note that the construction cost includes an additional 275 kV line to the grid. }

  • CG

    The development of Gravity Power Plants will be starting soon in Bavaria.

  • Tim Forcey
  • Dispassionate

    Professor Andrew Blakers discusses pumped hydro here

  • Bob_Wallace

    In the US we have thousands of existing dams which could be converted to PuHS. We have about 80,000 dams in total and use about 2,500 for electricity generation.

    Based on a survey of dams on federal lands over 10% of the non-producing dams should be expected to have adequate head and be reasonably close to existing transmission lines.

    We also have thousands of abandoned rock quarries and open pit mines.

    What we don’t have at the moment is need for massive grid storage. We’ve still got a lot of natural gas to replace. It’s going to take several more years before we will have significant times when all the coal and all the NG plants are idled by wind and solar.

  • Miles Harding

    Maybe it’s possible to get a triple benefit from a seaside storage facility: Energy storage, Solar PV energy and aquaculture?

  • Gary Park

    I wish Genex all the luck in the world on their project but if the Schematic is anything to go by they are going to have major issues to get it to work. It doesn’t matter what medium you use to store the energy, the trick is to recycle that medium as quickly as possible, that’s where the money is, if your pump or turbine is not turning you are under utilised. You only need to look at the AEMO site to see the price differentials in wholesale market price of power. Slightly confused with Molten Salt storage Carnot efficiency is (TH-TC)/TH best efficiency with Molten Salt 60%, PuHS getting efficiencies upto 90%, I guess by no heat loss!