| Neither the press release nor the research paper abstract provide the only number that matters: the energy efficiency. The energy stored per mass has little importance for a stationary system. What matters is the energy loss when the solar energy is stored into this chemical compound, instead of being converted directly by photovoltaic cells. 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. 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. In the absence of more precise information, this does not seem competitive with synthesizing hydrocarbons for long term energy storage, either in energy efficiency or in energy density, but only in the initial cost of the equipment, which is true only for now, as the living beings prove that synthesizing hydrocarbons from hydrogen generated with solar energy could be done at a very low cost. Because of the inherent very low efficiency of using this to generate electrical energy, the abstract of the research paper suggests as possible uses only "on-demand heat delivery for water heating, cooking, and surface defrosting". This may be useful, but far more useful is to use another method of energy storage that can be used for anything, not only for such limited applications. For myself, such a solution could provide only warm water for washing. For cooking, I would want my microwave oven, and I would also want my computers to work, so it would not make sense to invest in such a thing, instead of in a battery that could cover all my energy needs. Only if the energy efficiency from the incoming solar energy into the heat used to make hot water were significantly greater than when passing through photovoltaic cells and a battery, such a system could be useful to provide heating and warm water to a building, allowing for smaller batteries to cover the other energy consumption. |
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.