With the increase of variable renewables on the grid, the need for electricity storage will only grow. But what kind of storage? According to Philip Hiersemenzel of German battery manufacturer Younicos, business opportunties will for now lie in short duration services. Based on his company’s modelling, he says large-scale grid storage does not make sense – yet. Without storage, 40% renewables is max. Mike Stone of Energy Storage Report interviewed Hiersemenzel.
The ever-increasing supply of renewables to the grid is to some extent an experiment. No one knows exactly at what point the instability will become too large to handle. Benedict De Meulemeester, chief executive of the energy consultancy E&C, has pointed out that, despite dire predictions of disruption as a result of the Energiewende, Germany’s grid actually still has one of the lowest outage rates in the world.
This is something of an achievement, given Germany’s renewable penetration of around 25%. However, according to Philip Hiersemenzel, spokesperson of German battery manufacturer Younicos, this conclusion is much too easy. Hiersemenzel says the ‘no problem’ attitude overlooks two inconvenient facts.
Firstly, as part of a pan-European grid, Germany can simply export grid instability to its neighbours when need be. Remember, he cautions, that only 8 to 9% of energy in this wider European grid comes from intermittent renewable sources.
Secondly, he points out that German Transmission System Operators (TSOs), the organisations entrusted with transmitting electrical power from generation plants over the grid to regional operators are “intervening once or several times a day where they intervened a few times per month before.”
Hiersemenzel and Younicos, the company he represents, believe that grid instability will only increase as the percentage of intermittent renewable power rises.
This is not all bad, because as instability grows, so will the opportunities for energy storage in Europe. What sort of storage? This, says Hiersemenzel, will change over time.
Various scenarios modeled by the company have convinced it that the initial business opportunities will be found in short duration services such as frequency regulation, plus primary control and black start capabilities.
It’s only when the entire European energy network reaches 40% renewables, says Hiersemenzel, that storing GWh of electricity for many hours or even days will start to make financial sense. And so “for now, that is the next 10 to 20 years, business is elsewhere,” he concludes.
As we were intrigued by the modelling that Hiersemenzel mentioned, we fired off a few more questions to him.
Energy Storage Report: Can you provide further details of the modelling you have done around renewable energy integration? What happens when you get above 30%?
Philip Hiersemenzel: Basically, you can’t go above an annual average of 30% without energy storage. If there is too much intermittency in the system, the rotating mass will go on strike at some point and the lights go out!
Even if you manage to build a very smart system – but without storage – which allows you to go down to as little as 40% diesel (which they did on the island of Bonaire and this seems to be the absolute maximum), you still end up with about 30% renewables annually – because you never have perfect continuous solar/wind conditions.
If you want to go above 30%, you need to be able to switch off the rotating mass entirely, which in turn means that you need something else to stabilise the system – and that something else is energy storage!
Now, when you plan to add energy storage, its power is pre-determined by the maximum load. This equation can be optimised for cost – which led to our first surprise: namely that four hours of storage would be enough to get to about 65% renewable energy.
Other islands (we have studied) have shown no significantly different results and there is no reason to believe that what holds for small islands doesn’t hold for big islands – which is what continental grids are too, at the end of the day.
ESR: Are your results based on a particular geographical area? Is it possible to increase the level of renewables by connecting larger regions with more options for generation and consumption?
PH: No, not really. There are some differences, yes. For instance: some islands have an economic optimum renewable energy level as high as 80% because they have stable wind and solar patters that fit the load curve nicely, both daily and annually. And, yes: larger systems are more stable, but there is a limit.
ESR: Have you done any financial modelling to show how energy storage deployment compares to other options (such as new base-load generation, improved interconnections and so on)? If so, what were the results?
PH: New base load is the last thing we need! Inflexible must-run plants are the problem, not the solution! We need more flexibility in the system. All studies that look at real costs and benefits clearly support short-term energy storage as a complement (not an alternative) to smart grids.
The problem is that the system is tailored to the fossil-nuclear world of big plants. So while the must-run capacity of such plants blocks space on the grid, the cost is – silently – passed on to everybody. In contrast, batteries always relieve the grid, because they always absorb excess energy and provide it when its scarce.
In our UK Power Networks project (the largest trial of energy storage in Europe), Imperial College estimated that the battery saves otherwise necessary grid expansion costs of UKP£6m. However, this is mainly because of the short, but power intensive electric heating period in England. Still, this is an add-on to all the other uses of the battery.
In conclusion, if the modelling from Younicos is correct, then instead of investing in more base load, Europe’s grid should be looking for a lot more energy storage in tandem with still more renewables. Only then can we truly, as Hiersemenzel puts it, “let the fossils rest in peace”.
Published first on Energy Storage Report and republished with permission here.