| > There are 2 losses, before storage only a part of the incoming solar energy is eventually stored into chemical bonds, the rest being either converted into heat or not absorbed. Capturing some heat as non-heat still would make a house less warm in summer. > The second loss is when the energy is recovered. As it seems that the temperature that can be attained when extracting the stored energy is very low, the efficiency of conversion into other forms of energy will also be very low If you use it to heat a house in winter, wouldn’t losses be very low? (Since you say “For myself, such a solution could provide only warm water for washing”, that use case doesn’t apply to you, but many people do need to heat their houses in winter) > The energy stored per mass has little importance for a stationary system For the use case I mentioned above, I think it matters. If you want to store heat for 6 months and then extract it, the volume/mass needed will be significant. There also is a third loss: between the time you store the energy and the time you extract it. Many batteries have relatively high self-discharge (Google says 1-3% per month for Lithium-ion) _If_ this does away with most of those losses, it could be competitive even though it is less efficient at capturing heat. Having said that, this product probably has too low an energy density for that. Dry wood has ballpark ten times the energy per kg as modern batteries, but even for that, you need quite a bit of volume to warm a house in winter. |
Usually you can do something like light->electricity->battery[x]->electricity->heatpump->heat. The efficient in the heatpump is like 300%, i.e. for every 1 Joule stored in the battery, the heatpump extracts 2 Joules from the ambient and sends 3 Joules of heat inside your home.
This device is something like light->bath[y]->heat.
If you assume both get the same amount of light, it's misleading to compare the energy stored in battery[x] and bath[y], because the first has a magic x3 later that comes from the heat pump. This sods not depends on the exact setup, but it's an important difference between "work" and "heat" in a thermal machine.