The PNNL claims this phase change energy storage can hibernate for long-term storage. They stated that the room temperature battery must be heated up to 150 deg C to bring it out of hibernation. There are a few problems that I see with this.
The battery takes time and power to heat it up to bring it online. This could cause it to be dependent on the grid and if the segment of the grid was down, the battery would not be able to be brought online.
The time delay from hibernation to being online is not a problem if it’s used for seasonal storage, but if there is an emergency, this time delay must be included in the battery’s dispatchability.
These time delay issues can be solved by including short term battery storage along with the hibernating battery. But if the power needed is a substantial part of the short term battery, then it must be increased in capacity so that power can be reserved for use to heat the hibernating battery in case of loss of the grid.
My thought is that pumped hydro is a better system that’s proven by decades of experience. It can be brought online in a minute, maybe less. Also there are other storage systems, such as CAES, that are being developed that are larger scale – hundreds of megawatts. This hibernating battery would probably be like the battery energy storage systems now made in a transportable container: it is manufactured in a factory and shipped to the site. Therefore it would take dozens or hundreds of them for a utility scale storage system.
Another story partly about this “freeze-thaw” battery.