Electric Thermal Storage

Published:
By Jeff MacKinnon, P.Eng., PE

There is a lot of talk about chemical based energy storage (batteries), but before batteries there was thermal storage.

Thermal storage is similar to using bricks or water for thermal mass, it limits the thermal swings by slowly releasing the thermal energy into the space even after the heat source (sun, fire, etc) has gone away.

Image of a thermal storage unit

Electric Thermal Storage (ETS) operates in a similar way. The ETS that we have installed in the studio used bricks to store the heat. When there is a call for heat in the space a fan draws air over the bricks "wicking" away the heat and releasing it in the space.

I'm not a mechanical engineer, so don't quote me on these terms.

Current Electric Thermal Research

There is still a lot of development in ETS technology, even with the attention to battery storage.

Most of the products we see on the market today, that are ready to buy still use thermal mass storage, but there is really neat chemical storage options being developed, like from Neo Thermal where they store the heat in a salt, similar to the heating pads you put in gloves to keep your hands warm.

Other Research in ETS

I did a quick search for "thermal storage" on IEEExplore and saw a few really interesting papers, including a couple that looked at using chilled water for "cooling" storage in commercial buildings [1]. This was an old paper, but thinking about it, with the AC load in California lining up with solar power, this may be a great place to dump excess generation from wind or solar installations.

Building on that old paper is this one from 2016 - Use of Adaptive Thermal Storage System as Smart Load for Voltage Control and Demand Response. [2]

In this paper they propose that a large scale ice thermal storage system, similar to the 1985 paper, could be used as part of a demand side management scheme for fast voltage control and load shaving.

Another paper spoke to the point that concrete waste from building demolition has a use as the thermal storage medium. [3] The specific heat measured in this paper ranged from 700 and 850 J/K*kg.

For comparison, the 176kg ETS that we have installed in the studio stores 32kWh and uses clay bricks that have a specific heat value b/w 900 and 1000 J/K*kg. [4] This recycled material may not be the best solution for small commercial applications, but possibly a solution for large industrial applications where there is more space and possibly a lot more waste heat.

So what?

If we are going to reduce our carbon emitions fast enough to limit the climate crisis to BAD, rather than great filter, then we will need to develop all the tools in parallel. There isn't a silver bullet.

While chemical storage in batteries is one great way to electrify everything, thermal storage is a great tool for building energy management and helping the shift to distribute energy resources (DERS) like solar everywhere, and wind.

This is something that I put together in an afternoon of reading, imagine the possibilities if you spent your masters, or made engineering thermal storage solutions a winter project.

Citations

[1]D.R. Laybourn and V.A. Baclawski, "The Benefits of Thermal Energy Storage for Cooling Commercial Buildings," in IEEE Power Engineering Review, vol. PER-5, no. 9, pp. 31-32, Sept. 1985, doi: 10.1109/MPER.1985.5526437.
[2]
  1. Luo, C. K. Lee, W. M. Ng, S. Yan, B. Chaudhuri and S. Y. R. Hui, "Use of Adaptive Thermal Storage System as Smart Load for Voltage Control and Demand Response," in IEEE Transactions on Smart Grid, vol. 8, no. 3, pp. 1231-1241, May 2017, doi: 10.1109/TSG.2015.2513743.
[3]J.B. Martinkauppi, T. Syrjälä, A. Mäkiranta and E. Hiltunen, "Some Aspects of Recycling Concrete Crush for Thermal Heat Storage" 2018 7th International Conference on Renewable Energy Research and Applications (ICRERA), Paris, 2018, pp. 707-710, doi: 10.1109/ICRERA.2018.8566981.
[4]https://www.engineeringtoolbox.com/specific-heat-solids-d_154.html