As described above, the methanation of electricity must be viewed critically. Methanation is not needed for the energy transition, it is also highly inefficient. No matter how much excess power is generated: Only with "Power to Heat to Power" it will be possible not to waste excess electricity, but to make it usable again in the future as needed.
Overall, the existing technologies for storing electricity are too expensive, too inefficient, resource-intensive and/or cannot be implemented on a large scale.
With "Power To Heat To Power" efficiencies of reconversion in a heat and power machine of up to 50% can be achieved.
Heat accumulators are not characterized by a particularly high energy storage density. Rather, their most important advantages are their low price, storage efficiency of around 90%, high cycle stability and resource frugality.
What is interesting about the technology is that existing solar (thermal) power plants or wind power plants can be retrofitted with heat storage for "power-to-heat-to-power" with manageable effort.
High-temperature storage is cost-effectively scalable.
The grids are not suitable for the strong fluctuations in volatile energy production. The fewer decentralized storage options are available, the more investments have to be made in the networks. This is only more cost-effective if you fixate on power-to-gas and battery storage.
"Power-to-heat" has so far been a synonym for the utilization of electrical energy in the heating sector. By using electricity from renewable energies, "Power-To-Heat" systems represent an important building block for the decarbonization of the heating sector.
But now it's all about converting heat back into electricity
: Power to Heat to Power.
Conclusion 4: In order to counteract long-lasting dark doldrums, we need storage that can store the average power (base load) for several days.
A 1,000 kW wind turbine (24,000 kWh per day) has an average output of approx. 150 kW (3,600 kWh per day). For every 1,000 kW of installed power, a storage tank of 7,200kWh is needed per day to be bridged. With a nominal output of 5,000 kW, that would be around 36,000 kWh per day.
Rule of thumb: 1 kW of installed nominal power x 7 = required storage size in usable kWh per day
Conclusion 5: The reconversion is best done in a system that is fed by thermal storage tanks, and can also be operated with gas.