Cryogenic Energy Storage for Data Centers by Peter Judge
Liquid air isn’t the most obvious energy storage system, but it is being proposed to help solve the problems of the electrical grid. I wonder if it could also help sort out some of the issues in data center power.
Storing electricity is one of the biggest industrial problems we have - if it were solved, we could operate a much leaner and cleaner energy system. That sounds great, but there are lots of questions, and I just saw them worked on at an ecoConnect Green in the City event in London.
This was aimed at investors and business people associated with the utilities, but it held my interest just as much as the last one I went to, on Green IT.
First we heard why storage is important. Water can be delivered via reservoirs and storage tanks, but electricity can’t be stored eoncomically, so it has to be generated on demand. And since that demand shoots up and down during the day, we have to have lots of “spare” capacity ready for peak times.
There is some storage on the network: large capacitors, and giant pumped hydro-electric stations like Dinorwig in Wales. When demand is low, it can use electricity to pump water up into a reservoir, so it can be used later to generate electricity when that is needed.
But Britain doesn’t have mountains wherever they are needed, and much more storage is needed. The Institute of Mechanical Engineers is campaigning to get more investment in electricity storage, and has produced a paper describing how this might be done.
One of the most surprising ideas is cooling air to liquid form: cryogenic energy storage. The theory has been worked out, and for a couple of years now, one company in the UK, Highview, has been running a cryogenic energy facility at Slough near London.
It uses industrial chillers to cool air down till it condenses, and then stores it in large tanks. When more electricity is needed, it evaporates the liquid gas, and uses it to drive turbines.
When energy is stored, it’s never completely efficient. Highview gets back about 50 percent of the energy it puts in - but if that allows the country to avoid building new generating capacity for peak demand, it is worth doing.
The system becomes even more efficient if it can use waste heat from other nearby industry to warm the liquid gas up. It can be as much as 70 percent, which is about the same as pumped hydro.
For this reason. it’s a good idea to have cryogenic storage near a conventional power station - there is plenty of waste heat there.
Highview wants to site cryo-storage systems across the country, to even out the load and supply energy for peak demand.
But what about data centers? Apple is using a lot of solar energy at its center in Maiden North Carolina, but that is only available during the day. Other data centers use wind power, which fluctuates in much the same way.
Data centers also have a lot of backup provision: diesel generators that can be switched on quickly when needed. Cryogenic storage can be available quickly - that’s one of the reasons it can balance loads on the power grid.
I’d be interested to see if cryogenic storage would work as backup and load balancing in data centers.