Optimised storage of electricity

We asked PhD students Melina Sattelmeier and Noomi Westling Öhman about their work in the field of optimised electricity storage. Melina works in the field of Fluid Mechanics and Noomi in the Department of Law at Luleå University of Technology. Their work focuses on optimising the storage of electricity in water reservoirs and regulated rivers to increase the flexibility of the energy system.

With the increasing production of intermittent energy from solar and wind power, there is a need to investigate how hydropower can be combined with different forms of storage, such as mechanical, electrical, chemical and thermal storage, taking into account biodiversity and social acceptability. By using digital twins of rivers, a better understanding of the outflows and losses of dams can be gained, thus optimising the storage process.

Melina, could you briefly explain what your part of the sub-project is about?
It is primarily about the link between fluid mechanics and ecological aspects. This means that I will be investigating whether pumping power can be used to increase the storage of electricity in regulated rivers and how the ecological impact can be minimised.

What challenges do you see in combining hydropower with different forms of storage, especially in view of the increasing production of intermittent energy from solar and wind?
The work will primarily focus on pump energy as a form of storage. Practical challenges include the search for suitable locations where pumped energy can be used. For example, if the pump energy is to be used as a back-pumping system in an existing plant, you need a reservoir with a sufficiently large storage volume. This also has an impact on the selection of a suitable case study for my project.

What benefits do you expect from increasing the flexibility of the energy system by optimising electricity storage?
The implementation of renewable and intermittent energy is a major challenge for the Swedish energy system. Electricity generation will become increasingly difficult to plan with the increase in intermittent energy sources. Therefore, more balancing measures will be needed to ensure a stable power supply. Furthermore, if you want to utilise the full potential of e.g. wind energy, you need to be able to store the electricity for a later point in time so that the power plants do not have to shut down. In short, optimised electricity storage can lead to a more efficient use of resources when integrating renewable energy sources and stabilise the power supply in the event of fluctuations.

Can you say something about the ecological impact and what you have in mind?
In contrast to normal hydropower, the water in pumped storage power plants flows both downstream and upstream. The fact that the water is pumped upstream can, for example, lead to greater fluctuations in the water surface in the reservoir or to the entrainment of plants or microorganisms that can be transported upstream. However, one of the most important ecological factors in lakes is temperature stratification, and this is precisely what we are focussing on now: Which factors have the greatest impact on temperature stratification in reservoirs and how can the ecological impact of pumped storage power plants be mitigated?

And regarding the legal part of the project. Noomi, what are you working on?
The legal part of the project means, very briefly, that we will be looking at the legal requirements for pumped storage. I will first focus on the issue of authorisation and then build on that.

You are also looking at social acceptance. Tell us more about that and what will be analysed.
Social acceptance is a bit more difficult to analyse. As it stands at the moment, we will start by looking at what the barriers to pumping are.

Noomi, what do you hope will be the outcome of the work in about 5 years' time?
For the legal and social part, I hope that we have found an answer to the question of what conditions exist for the use of pumping energy and that we have been able to identify all the obstacles that the use of pumping energy could entail.

Can you say something about possible challenges and obstacles?
The biggest challenge in legal and social terms is actually social acceptance. However, I am optimistic about the future.