We held a Rethink Energy webinar this week entitled “Can Lithium-Ion batteries play in 10 hour capacity markets, or do we need another technology?” The upshot was broad agreement about the way the markets would move from their frequency response beginnings, through to lulls in intermittent supply today lasting around 4 hours today.
The experts we assembled were Marek Kubik of Fluence, a lithium ion whole system provider; Charlie Blair, CEO of UK based mechanical storage outfit Gravitricity; Stefan Schauss, from Enerox, an Austrian based Vanadium flow provider, and Maximilian Schumacher, who represents Siemens Gamesa, which has a thermal “hot rocks” heat storage system.
There seemed to be quite a lot of consensus among the four experts on what the future holds and it really splits into the current 4 hour market expanding a few hours at a time, topping out at potentially 10 or 12 hours, with the search very much on, but undecided on technology, for inter-seasonal top ups required either for heat or cold.
Most of the panel agreed that heat was the big worry, but that while hydrogen may have a role to play in the future, it was unlikely to be power to gas, back to power, to drive heat, as it was tough to make a business case for this due to the round trip efficiency. Schumacher made the point that really cheap materials available all over the world were likely to form the basis of district heat initiatives, with thermal storage supplying heat directly as heat.
The early parts of the discussion all centered on round trip efficiency, with both the mechanical Gravitricity system, which relies on either one large weight or a series of weights, and lithium ion accepting that they were on a par in the high eighty percent levels, say around 89%, including going from DC to AC and back again and taking into account how young the battery was.
Kubik accepted that lithium ion decayed somewhat and said output was dependent upon the power to energy ratio, Blair said that in mechanical it was winches and gearboxes that wore down, but were 1% of the total system outlay. But both agreed they could beat the 70% likely with existing pumped hydro. Peter White, the Rethink Energy CEO who was asking the questions reminded everyone that in the US there is 22 GW of pumped hydro and up to the end of 2019 just 1.1 GW of battery storage in the US.
Schauss reported that quite a few of his installations were already used for long duration storage after a fashion, because Vanadium Flow works differently and does not have an upper limit on discharges and can go from one state to another, from charging to providing energy, as many times as was required in a day, and at any part in its cycle, and it was not a once a day cycle service like lithium.
It was Schauss who summed up the conversation best saying that the 4 hours market that was prevalent today was because that’s how energy was traded, and pointed out this would top out at ten hours, because there were 24 hours in a day, and if it took 14 hours to charge a battery fully, and ten hours to discharge, than once we moved from that usage pattern to something seasonal, there was not a business case. Blair described this as a usage issue, with two peaks a day in energy usage in most parts of the world.
So is there a storage market beyond the 10 hour level? Blair thought there was and hydrogen or thermal was likely to be the answer, “For situations where you need long duration of days, or weeks, or inter-seasonal storage, it is clear that chemical, flow, mechanical and CAES all have to cycle, and so if you have to wait a year to discharge or a week, there is no business case for them. It is more likely to end up with hydrogen or thermal.”
We find that in hot climates the peaks are during the day for air conditioning, and that can be resolved by installing more solar, but in colder climates, heat is the issue, and it is best if there is no round trip involved, so if you generate green hydrogen from power it makes sense that you use the hydrogen as a fuel, or better still, as Schumacher said, use it to heat up volcanic rock, top that up occasionally, and keep it all as heat, and syphon some off as hot air when it is needed.
Rethink Energy was fairly shocked to find that most of the panelists agreed with Schumacher on this, and went back to focusing on the four hour market and rising. The overall feeling was that each technology had an advantage in some special situations, and that yes lithium ion energy storage would grow to work over ten hours at some point and all of them would share in the market which was huge. How big? Well Rethink Energy has just launched a forecast that says the opportunity for battery energy storage is 365 GW by 2030. “Why stop there?” said Schauss, I think the market for peakers is already closing in on 900 GW,” which shows that by 2030 we will have only just scratched the surface of this market.