14th June 2024

Michael Barnard’s article and subsequent comments on CleanTechnica have prompted questions about RheEnergise’s high-density long duration energy storage (LDES) solution.

We are disappointed that Mr Barnard didn’t contact us before publishing to check facts and figures with us (some of which are commercially confidential). With respect to Mr Barnard, his article contains a number of errors and is based on a number of assumptions that we take a wholly different view on, not least on market demand and the need for new forms of energy storage, project financing and construction, and the availability (lack of) of water around the world.

The world is in a climate emergency; our small-scale solution can be built quickly, is cost-competitive with other forms of LDES, and has less environmental impacts than large-scale hydro. Our R&D work has been extensive and exhaustive, has been independently validated (by the UK National Engineering Laboratory, academics and different arms of the UK Government), and our R&D continues. We will take valuable lessons from our demonstrator project that is currently under construction in SW England.

Here are the facts about our High-Density Hydro® solution and why it will play such an important role in enabling the energy transition across the globe:

• The energy transition requires a 100x increase in the rate of long-duration energy storage [1]. The status quo will not work, and new solutions are required to solve the problem of scaling to large volumes, quickly and globally.

• Conventional pumped hydro storage (PHS) makes up more than 95% of all legacy energy storage [2]. But as good as conventional pumped hydro is, it is unable to scale to the required volumes. This ultimately comes down to site constraints: the overwhelming majority of PHS is open-loop and requires a river or water course, a sufficiently high mountain, and a natural alpine valley that can be dammed to form a reservoir. The most current industry statistics [3] confirm that conventional PHS cannot scale; only a handful of projects are under development globally with development times exceeding a decade.

• High-Density Hydro solves these site constraint limitations. A closed-loop design removes the need for significant water course and alpine valleys [4]. And the high-density fluid gives a 2.5x decrease in system size (on a like-for-like basis).

• RheEnergise has developed a high-density fluid for High-Density Hydro applications. It has a density 2.5x that of water, low viscosity, the required stability, low abrasion/erosion, non-toxic (as tested by third party labs [5]).

• We regularly run our high-density fluid in test rigs at our 15,000sq ft R&D facility in Montreal, through pipes, valves, pumps and turbines. The various parts of a full-size system have been under test over the last three years and the knowledge gained has fed into the completed design of our demonstration project which is now being built in SW England.

• Our High-Density Hydro solution won the UK Government’s “Longer Duration Energy Storage” competition [6], as part of which it has undergone intense scrutiny from the UK Department of Energy Security and Net Zero.

• Our solution is being developed in close cooperation with the established global hydro industry [7].

• The strong validation of winning the “Longer Duration Energy Storage” competition is echoed by customers, with a weighted commercial project pipeline of over £500m and signed commercial agreements in Chile [8], UK [9], Australia and the US.

• Respected international energy industry research organisation Bloomberg NEF surveyed LDES technologies and concluded that the lowest cost solutions were “novel pumped hydro storage”, which includes High-Density Hydro [10].

• Our flow rate is comparable to water, not 50 to 200 times slower than water as stated in the article; we have proven field test results validated by academics at the University of Exeter [11] and industry partners [7].

• The deployment of our technology does not require tunnelling into the mountain/hillside as our projects will be significantly smaller-scale than conventional pumped hydro. For a typical project, penstock (pipes and cut and cover excavation) are only 12% of the total project cost. For a 20MW RheEnergise project, the penstock diameter is between 1 and 1.6m. Volumetrically - everything (pipes, valves, turbo machinery) is ~60% smaller. This leads to cost savings, not cost increases.

• Mr Barnard compares the cost of a PHS water project, with a 500m head, to the cost of an HD Hydro project, with a 200m head. To make an accurate comparison, costs compared should be of either two 500m projects or two 200m projects. In either instance, when the heights are the same, the construction effort to create the volumes for the two projects are completely different. The HD Hydro project is ~60% smaller volumetrically. Everything is ~60% smaller volumetrically - the storage reservoirs, the pipes, the valves, the turbo machinery, the power-house footprint, etc.

• When considering the costs of a PHS project approx. 65% to 70% of the cost is the civil engineering costs, therefore a 60% reduction in volumes of civil engineering work represents a significant saving in overall project construction costs. These civil engineering cost savings offset the cost of the fluid, leading to comparable best in class economics, but with the advantage of scalability (more sites and faster build times). RheEnergise has worked with a global engineering consultancy, and supply chain economists to estimate project investment CAPEX, and even at a much smaller scale systems, the $/kWh is comparable to conventional pumped Hydro and one of the most cost competitive of all novel LDES solutions under development (BloombergNEF [10]). 

• Mr Barnard projects that HD Hydro is only 33% more expensive than conventional pumped hydro for the same energy, at an elevation 2.5x lower. However, it should also be noted that a closed loop pumped hydro system is almost certainly going to be more expensive to build than the conventional open loop version.

• The world needs energy storage that can be scaled rapidly and globally, and there are orders of magnitude more sites at 200m, than at 500m. Even if we were 33% more expensive (which we contest) at a project site with only 40% of the elevation need for the same performance, we would still take this scenario as a big win, because to solve the energy transition there is an urgent need for scalability. The need for scalability is vital without having to resort to new transmission infrastructure, which is costly, and has decade-long development timescales. RheEnergise offers a scalable solution whilst maintaining best in class economics of conventional pumped hydro.

• For those of you who read Mr Barnard's initial article, he discussed an oozing fluid. We thank Mr Barnard for correcting his calculations but wanted to add some detail to illustrate viscosity. When one thinks of ooze, one thinks of something with the viscosity of say treacle, which does not have a viscosity of cP200, as stated, but around cP20,000. One can see from our video above that our fluid is non-viscous, and that it is much closer to milk ~cP3, than to runny honey ~cP3,000, and certainly much lower than an ‘oozing’ liquid like treacle ~cP20,000.

We have the support of our investors, our business partners, government agencies, academics and energy industry professionals and the onus is now firmly upon us to deploy our first commercial scale HD Hydro project.

We do wonder why Mr Barnard has chosen to criticise us, rather than to engage with us, and we are disappointed that our engineering and business credibility has been questioned in such a manner. We trust that this statement is helpful to the readers of CleanTechnica.

References

[1] McKinsey & Co Report with LDES Council - Net-zero power - Long duration energy storage for a renewable grid - November 2021

[2] [3] Pumped Hydro Storage database

[4] Australian National University - Global Greenfield Pumped Hydro Energy Storage Atlas

[5] Toxicity tests carried out by Blue Frog Scientific, Chemex and Socotec

[6] Press release - RheEnergise awarded £8.25m UK Government contract to build its first advanced long duration hydro energy storage system - 28th November 2022

[7] Reports, work and analysis carried out by: Cost Models: Mott Macdonald (Global Engineering Consultancy), Computational Fluid Dynamics: TUV-NEL (National Engineering Laboratory - UK), Formulation Science: University of Greenwich - Formulation Science Department, and Turbine R&D: Energy Revolution Services.

[8] Press Release - RheEnergise Signs MOU with Leading Chilean Utility Colbun to Develop Long Duration Energy Storage Projects in Chile - 14th November 2023

[9] Press Release - Mercia Power Response and RheEnergise Working Together to Build Long Duration Energy Storage - 16th August 2023

[10] BloombergNEF - Lithium-Ion Batteries are set to Face Competition from Novel Tech for Long-Duration Storage: BloombergNEF Research - 30th May 2024

[11] University of Exeter - Cambourne School of Mines