By Judith Plummer Braeckman and Sanna Markkanen

In early March, an article in the Los Angeles Times, asked whether hydropower is “an environmental disaster or key to a clean energy future?”  It goes on to describe the Eagle Mountain pump storage hydropower scheme which will use old mine workings to create a storage facility to complement solar photovoltaic generation.  An alternative suggested is the use of the mine as a national park, which leads the article to question whether there is a balance to be struck between environmental protection and climate change mitigation.

This not a new question.  It has been raised in relation to many technologies that will be needed to mitigate climate change, from the potential biodiversity loss associated with biofuels and wood-based fibres to replace plastics, to the environmental and social impacts of lithium and cobalt mining for batteries and the risks that wind turbines may present to birds.  However, few other low carbon technologies evoke such strong feelings – or as vehement opposition – as those in relation to the development of hydropower.

Yet the opinions of the opponents to hydropower are partly based on the historic failings of the industry rather than the current best practice.  In particular, there has been a considerable improvement in the management of environmental and social impacts of hydropower over the past 20 years, culminating in the development and adoption of industry-wide standards and toolkits for ensuring sustainable projects, such as the Hydropower Sustainability Assessment Protocol (HSAP).

Weighing up the impacts and benefits

Considering that some adverse impact is inevitable in any renewable energy development (think here a battery’s need for cobalt or lithium and the lack of recyclability of some wind turbine components) – the problem of hydropower and pump storage projects is that the stations are large, making the potentially adverse impacts associated with any one project similarly large.  However, the extent of these impacts does not increase linearly: a 500MW power station will inevitably have a larger footprint than a 10MW station, but this is highly unlikely to be 50 times larger. Perhaps a bigger challenge, therefore, is that hydropower’s impacts are localised and obvious – rather than occurring on a mining site or a factory on another continent. This makes them difficult for the local people to accept, while the climate benefits are much less obvious at the local level.  For pump storage in particular there is a need to weigh the localised social and environmental impacts of a project against the benefits that are much more broadly distributed, such as the use of these projects to help decarbonise the grid by facilitating the integration of more wind and solar generation.

The storage solution

IRENA’s Transforming Energy Scenario for 2050 states that, to meet the Paris Agreement target, almost two thirds of the world’s electricity will need to come from wind and solar photovoltaics by mid-century, as overall renewable contribution to electrical generation grows to 86%.  This creates a significant challenge for the management of global electricity grids.  If all grids were interconnected at the global scale, then the odds would be that the wind would be blowing and the sun shining somewhere, at all times.  However, the grids are not fully interconnected and such global scale interconnection would be hugely expensive, technologically challenging and politically explosive.

In the absence of a global electricity grid, some level of interconnection may grow – for example linking landlocked countries to coastal zones – but a certain degree of intermittency that each grid will have to address is likely to remain.  There will be times when electricity is needed when its dark and the air stands still, and times when the wind blows at 3am when electricity demand is low. This is why we need electricity storage. As the share of electricity in overall energy demand grows and the share of renewables in power generation also increases, so does the need for effective, short and long-term electricity storage solutions.

While battery technology is improving rapidly (to the extent that it is difficult to forecast what batteries can deliver by 2050), at present it remains expensive and has certain environmental caveats which may present a cause for concern and caution.  Batteries are also optimal primarily for short term storage – from seconds or minutes – but less cost competitive or suitable for longer term storage – and indeed at least currently unable to provide monthly or seasonal storage. This is where Pump Storage Hydropower comes in.

Pump storage hydropower relies on a height differential between two water reservoirs.  When electricity is needed, water flows downhill generating electricity as it flows through the hydropower turbine as in traditional hydropower projects. However, when surplus electricity is available on the grid, the water is pumped up to the upper reservoir to be used later to smooth the peak in electricity demand and to balance the variability of supply as the grids become more reliant on intermittent renewables. In spite of recent improvements in battery technology and some innovative solutions such as concentrated solar, pumped storage hydropower currently supplies more than 95% of the grid connected storage capacity and the demand for it is likely to grow in the coming decades. According to IRENA’s 2050 roadmap, the installed pumped storage capacity will need to double from 160GW in 2020 to 325GW by 2050 to support the power sector transition.

Ensuring sustainability

Like all hydropower projects, pump storage has potentially adverse impacts that need to be assessed and mitigated.  However, the understanding of these challenges – and how best to handle them – has developed rapidly since the World Commission on Dams launched their final report in 2000, resulting in fundamental improvements in the planning and consultation processes to ensure that new projects are sustainable. The extent of environmental and social impacts associated with pumped storage can also mitigated through so-called brownfield development, which minimises the destruction of undisturbed natural areas. For example, pumped storage capacity can be added to an existing hydropower project on a river, thus causing no additional disruption to the downstream river flow, or developed using a decommissioned industrial site to create a “closed loop” system that is not reliant on a major water course.

Any two reservoirs with a height difference can be used for a pumped storage project, as illustrated by the Dinorwig pump storage station in North Wales and, akin the Eagle Mountain scheme, the Kidson Pump Storage project in North Queensland, Australia. The Kidson project is particularly interesting as it uses an old mine to create its two reservoirs and, co-located with solar PV, can provide a consistent supply of electricity at a competitive price. Although the environmental impacts are not non-existent, they have been well managed, partly because the project was developed on a historic mine site.

In the coming decades, as governments seek to decarbonise their economies, we need to develop a strong and diverse arsenal of technologies to deliver this transition. Due to its multiple functionalities, sustainably developed pumped storage will likely be a fundamental part of the solution and should therefore be on the policymakers’ radar – in spite of the potential challenges.


Note: This article gives the views of the authors featured and does not represent the views of FutureDAMS as a whole.

Image: The Ludington Pumped Storage Plant, Michigan. By Consumers Energy (licence Creative Commons 2.0).


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