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> The researchers plan to incorporate the TPV cell into a grid-scale thermal battery. The system would absorb excess energy from renewable sources such as the s

by danans 5y ago

> The researchers plan to incorporate the TPV cell into a grid-scale thermal battery. The system would absorb excess energy from renewable sources such as the sun and store that energy in heavily insulated banks of hot graphite. The article doesn't provide the efficiency of this insulated hot graphite battery. Given that this device is meant to be paired pretty exclusively with such a battery, it seems like a narrowly applicable solution. Or are there other renewable sources of heat between 1900C and 2400C that could be used for this purpose?

kragen 5y ago
The efficiency of heating things up is pretty much 100%. The efficiency of insulation can be arbitrarily high (up to 100%) or arbitrarily low; heat loss is proportional to surface area and storage time and inversely proportional to insulation thickness. If your heat engine is only 40% efficient you might as well design your insulation to be 80% efficient or so over the expected time span, which would be a few hours for grid storage systems.
- danans 5y ago
  I was thinking more about the efficiency of the mechanism that transfers the heat from battery to the TPV engine. The article said that the device has to be exposed to photons coming off a white-hot source. I suppose that if the TPV devices are closely coupled with the white-hot source this should be minimal but it's not clear from the article whether there is an intermediary step, or how they plan to control the TPV's exposure to the heat source to discharge the battery. Given that this works via radiation (vs convection like a traditional heat engine), the path between the heat source and the TPV would have to be fairly direct, and not lose much heat to any adjacent non-TPV material. Maybe they have some kind of massively insulated opening/closing heat shield that they can use in a manner similar to the gates used to control water in hydroelectric plants.
  - gysfjiutedgj 5y ago
    You are correct. There is a shutter over the eye of Sauron.

by danans 5y ago

kragen 5y ago

The efficiency of heating things up is pretty much 100%. The efficiency of insulation can be arbitrarily high (up to 100%) or arbitrarily low; heat loss is proportional to surface area and storage time and inversely proportional to insulation thickness. If your heat engine is only 40% efficient you might as well design your insulation to be 80% efficient or so over the expected time span, which would be a few hours for grid storage systems.

danans 5y ago
I was thinking more about the efficiency of the mechanism that transfers the heat from battery to the TPV engine. The article said that the device has to be exposed to photons coming off a white-hot source. I suppose that if the TPV devices are closely coupled with the white-hot source this should be minimal but it's not clear from the article whether there is an intermediary step, or how they plan to control the TPV's exposure to the heat source to discharge the battery. Given that this works via radiation (vs convection like a traditional heat engine), the path between the heat source and the TPV would have to be fairly direct, and not lose much heat to any adjacent non-TPV material. Maybe they have some kind of massively insulated opening/closing heat shield that they can use in a manner similar to the gates used to control water in hydroelectric plants.
- gysfjiutedgj 5y ago
  You are correct. There is a shutter over the eye of Sauron.