Roger Andrews at
Energy Matters recently did some
detailed analysis on ARES. Unlike many (most?) blogs, this is one where the comments are actually worth reading.
Poster "Willem Post" puts the cost at about $0.40/kWh, which he shows is comparable to Tesla batteries. To me it is almost axiomatic in the energy world that if you can achieve the same solution at the same cost, but in a distributed fashion then the distributed solution should be preferred. (FWIW, my estimate of cost of the Enphase AC Battery is that the BEST CASE cost is $0.12/kWh. In reality, the cost today will be higher than that because I used optimistic assumptions.)
But poster "TheProle" wrote the following:
TheProle commenting at Energy Matters said:
Increasing capacity could potentially be very cheap if you don’t want to draw it all down at once (i.e. to cover increasingly long periods of calm weather).
if you form trains with the locomotives separate to wagons loaded with weights, then you can have storage yards at the top and bottom of the system in which weighted wagons live for months at a time if needs be, with the locomotives returning up or down the system to collect more wagons as needed.
That is something that batteries do NOT offer: the ability to provide seasonal storage capability.
So for overnight storage, batteries almost certainly take the prize. But ARES will need to be weighed against other technologies such as hydrogen for seasonal storage. ARES has the benefits of high efficiency while hydrogen may have the benefit of low land-use cost (assuming it is stored in pipelines). Hydrogen also has the benefit of being able to be much more distributed.
Finally, "TheProle" also added this:
TheProle commenting at Energy Matters said:
All this said, as someone who has worked in connection with heavy rail and knows a bit about what would be involved, it all seems to me to be rather optimistic and fragile – I’m pretty sure it would work, but I’m also pretty sure it will cost a LOT more to maintain in working order than it’s proponents realize (railway track takes a good deal of looking after for instance)
But does his experience necessarily translate directly to fully-electric locomotives? Probably only partially. But clearly maintenance is something that needs to be considered here.
Bottom line is that I seriously doubt that ARES can compete with Li-ion batteries for "overnight" storage. But seasonal storage is still the nut that hasn't been cracked. If there is one interesting part of the Energiewende experiment, it is the seasonal storage of energy by putting hydrogen in the natural gas pipeline. This approach has the obvious benefit of being more efficient, but it has much higher land-use implications. Will either of these come into long-term use? Time will tell. (Are there other significant proposals out there for seasonal energy storage?)