This is predicated on the claim that solar energy will be so cheap in summer there’ll be no point paying for efficient storage, and a roughly 1/3rd storage efficiency is fine.
Let’s do some quick numbers on this.
Let’s make the simplifying assumption that energy requirements are constant throughout the year, solar energy availability follows a sin wave, with peaks at the summer and troughs in the winter. Let’s also assume that solar power is twice as powerful in summer as winter.
Then if storage efficiency was 100%, you’d need peak summer solar capacity to be 1/3rd more than requirements.
If storage efficiency is 1⁄3, then peak summer solar capacity has to be 4/5ths more than requirements. (Sorry can’t be bothered showing my working).
In other words using storage with 1/3rd efficiency instead of 100% efficiency requires installing 40% more solar capacity.
Somebody would have to check the relative price of solar Vs batteries to see whether it’s cheaper to have excess solar capacity, or to have more expensive batteries.
solar energy availability follows a sin wave, with peaks at the summer and troughs in the winter. Let’s also assume that solar power is twice as powerful in summer as winter.
Those are bad assumptions. Solar efficiency in winter is lower than that compared to summer.
Additionally, it’s no sin wave but highly irregular and you want to still have energy when you hit one of those irregular spots where there are multiple days after each other and clouds block most of the sunlight.
Right now with the amount of solar capacity we have, there are days when energy is free and you even get paid to use up energy in Germany.
If you have three times the energy production in summer with solar cells that you need in winter, you don’t have reliable energy in winter without energy storage. But you do have a massive energy surplus in summer that you can put to use.
You’re never going to have so much peak capacity that you can store it all as methane and not need to use any other energy sources during the night/winter. Or at least doing so would be very expensive.
So you’re going to have to use other energy sources at solar trough times. If we can dirty energy sources, energy at such times is likely to be expensive.
So the question stops being about how cheap energy is at peak times. It’s about whether it’s worth storing 3 times as much energy to sell when it’s most expensive, but using more expensive energy storage solutions.
At the moment levelised cost of storing a kWh in a gravity battery costs roughly the same as producing it does (highly dependent on country). However if due to high energy prices, or future improvement in technology, levelised cost of storage is more than 1⁄3 cheaper than producing electricity at the most expensive time in some particular region, it will always be worth using a gravity battery over SNG.
At the moment levelised cost of storing a kWh in a gravity battery costs roughly the same as producing it does (highly dependent on country).
That depends a lot on how long you store the energy. As far as I understand most of the projects expect to use the energy within less than 24 hours to reach the cost efficiency you are talking about. Storing energy from summer to use in winter is two orders of magnitude more costly with gravity batteries.
This is predicated on the claim that solar energy will be so cheap in summer there’ll be no point paying for efficient storage, and a roughly 1/3rd storage efficiency is fine.
Let’s do some quick numbers on this.
Let’s make the simplifying assumption that energy requirements are constant throughout the year, solar energy availability follows a sin wave, with peaks at the summer and troughs in the winter. Let’s also assume that solar power is twice as powerful in summer as winter.
Then if storage efficiency was 100%, you’d need peak summer solar capacity to be 1/3rd more than requirements.
If storage efficiency is 1⁄3, then peak summer solar capacity has to be 4/5ths more than requirements. (Sorry can’t be bothered showing my working).
In other words using storage with 1/3rd efficiency instead of 100% efficiency requires installing 40% more solar capacity.
Somebody would have to check the relative price of solar Vs batteries to see whether it’s cheaper to have excess solar capacity, or to have more expensive batteries.
Those are bad assumptions. Solar efficiency in winter is lower than that compared to summer.
Additionally, it’s no sin wave but highly irregular and you want to still have energy when you hit one of those irregular spots where there are multiple days after each other and clouds block most of the sunlight.
Right now with the amount of solar capacity we have, there are days when energy is free and you even get paid to use up energy in Germany.
If you have three times the energy production in summer with solar cells that you need in winter, you don’t have reliable energy in winter without energy storage. But you do have a massive energy surplus in summer that you can put to use.
Either way, the point still stands.
You’re never going to have so much peak capacity that you can store it all as methane and not need to use any other energy sources during the night/winter. Or at least doing so would be very expensive.
So you’re going to have to use other energy sources at solar trough times. If we can dirty energy sources, energy at such times is likely to be expensive.
So the question stops being about how cheap energy is at peak times. It’s about whether it’s worth storing 3 times as much energy to sell when it’s most expensive, but using more expensive energy storage solutions.
At the moment levelised cost of storing a kWh in a gravity battery costs roughly the same as producing it does (highly dependent on country). However if due to high energy prices, or future improvement in technology, levelised cost of storage is more than 1⁄3 cheaper than producing electricity at the most expensive time in some particular region, it will always be worth using a gravity battery over SNG.
That depends a lot on how long you store the energy. As far as I understand most of the projects expect to use the energy within less than 24 hours to reach the cost efficiency you are talking about. Storing energy from summer to use in winter is two orders of magnitude more costly with gravity batteries.