What you propose is about 5TWh of total storage. Currently there are 40GWh. Increasing the current capacity 125-fold is just as unrealistic as increasing it 2000-fold, seeing how a company who now tries to push plans for the 13GWh pumped storage Atdorf (http://de.wikipedia.org/wiki/Pumpspeicherkraftwerk_Atdorf#Pumpspeicherkraftwerk_Atdorf , sorry, no English version) has been struggled for years with their plans, primarily against the opposition of the Green party.
So your plans is to build a ~30-by-30 kilometers sea that is elevated by 100 meters. Do you even realize how giant this thing is? It's the size of Berlin! Do you realize that you also need to multiple it by 2, since you also need a sea at the low level to store the water?
80TWh will never happen, and 5TWh won't happen either, and 1TWh is maybe realistic within 200 years or so. The renewable revolution will not happen, all we're doing now is going back to burning lignite and gas.
1) This storage capacity was calculated by simulating wind, solar etc. output based on real weather data. It already assumed a realistic mix of renewables including ones with adjustable output such as biogas and a realistic possibilities of export/import.
And about "firing up fossil plants for a few days in a year". Just imagine what would any electricity company do if they had a power plant that they would be able to use only a few days a year? They would immediately close and dismantle it and fire the staff, because the maintenance and standby costs would dwarf any profit from it.
Actually, this effect can already be seen here in Germany. We're far away from 100% renewables, yet in the wake of closure of several NPPs, and the ever increasing demand for backup power because of growing renewable supply, there is a huge debate about building additional coal and gas power plants. One would guess there's a gold rush building these? Nope. The major electricity producers already said that unless they can fire them close to 24/365, there's simply no profit in building them. The government would have to do the despicable and actually start subsidizing coal and gas power plants if they want a stable supply.
2. Solar might have a generation curve that matches the daily consumption. But seasonally, it doesn't match the consumption at all. The season of the peak consumption in Germany is WINTER, because of less natural light and warmth. At the same time, the solar production is very low in winter, it falls way below 5% of what it does in the summer. It's the saisonal fluictuations that need the storage, not daily.
3. This list is obviously bullshit. It lists Germany with THE AVERAGE PRICE of 27 $ct/kWh. it's like 21.5 euroct/kWh. I'd like that price! Where can I get it?
If you look at verivox.de, there's a price calculator at the top. You can enter the postal code (try 10000-13000 for Berlin) and your expected consumption to get the cheapest tariffs. The cheapest one I get is 411 euros for 1700 kWh a year. That's ~30 US-cents/kWh in the current conversion ratio. However it's a prepaid package which everyone would recommend to stay the hell away from. Last year a major "cheap" supplier suddenly went bankrupt and many people lost their prepaid electricity packages. The average prices are much higher, typically around 26-27 euroct/kWh.
About the taxes: the major factor is in the recent price increase in Germany was indeed a tax - a sort of a tax that is levied on the electricity consumers and used to pay the renewable electricity producers.
4. Well, guess what? Germany is a couple of hundreds kilometers long. Yet the wind power manages to fluctuate between near zero and the maximum all the time!
1. the household electricity consumption is only a minor part, the most is consumed by the industry, and you need to provide storage capacity for them as well.
2. The regenerative power like wind and solar is subject for a major saisonal fluctuations. Which means, the storage needs to be able to load all the energy during one season with high production and keep it for months so you can use it in a season with low production.
3. Currently, Germany is in a "20% scenario". We already have the highest electricity prices in the world (for a major country) ~26 âct/kWh and the import/export saldo in the area of 15% of total production. The electricity prices will likely increase by another 3-4 cents next year and so far there's no end to the price hike in sight.
In Germany, the electricity production/use is ~7500kWh per capita, so 1MWh storage is sufficient for just about 50 days. Considering that the assured production of wind power is below 1% (that is, 200MW in the entire country with over 25GW wind turbines) of installed capacity at 99% of assured supply (that would mean 3.5 days of blackout per year on average, in reality we have only ~15min, or 99.997% assured supply here), it's not that astonishing at all.
Normally, CAESes, such as the on operating in Huntorf in Germany, IS burning natural gas. When storing energy, the air is pumped into the caverns. When extracting it back, the air may just turn the turbine directly, but this way, a lot of energy will be lost - the pumped air storage is tightly sealed, but the compression heat is inevitably leaking from the cavern.
What they normally do instead - they use compressed air as the input for a turbine burning natural gas - this way it does not need it's own compressor, making it more efficient than a conventional turbine. From 0.8kWh of stored electricity and 1.6kWh (thermal) of natural gas, they produce 1kWh of output electricity. Burning 1.6kWh gas in a normal turbine with 50% efficiency would produce 0.8kWh electricity, so the overall efficiency of this storage is just about 50% - or even less if you consider more efficient gas-and-steam power plants. Maybe this new CAES will utilize some more efficient technology, but don't expect wonders from it - this type of storage has quite high losses.
The CAES were never about storing power efficiently, their main advantage is the ability to power up really quickly. The Huntorf CAES for example is able to reach 50% output in just 3 minutes, and full output in under 10 minutes.
Kleeneness is next to Godelness.