Okay, so not 70% of the days, but 70+% of the time wind and solar farms are not producing any energy, period. Last I looked into this, the solar farms in AZ and NV had the best records for producing electricity but only did so 33% of the time. Also, the point when things go awry is between 8% to 10% capacity, although it could be as high as 12% depending on the other dynamics of the area.
Now, insofar as comparing prices, which you often reference or allude to, it is important to remember wind and solar energy prices have nothing to do with the cost of production, what most people think, nor do any other sources. The prices are just like the price of oil; the cost of production is irrelevant to the price that the market is willing to pay. The market is what dictates the price and is mainly dependent on when that source of energy is put on the market, with "when" being very important.
Wind and solar produce most during non-peak hours, when demand and price are low, and little during peak hours, when demand and price are high. This means when determining the average price of this electricity, most of the data is coming from the cheaper times of day and is not weighted evenly throughout the day. However, the base load sources (oil, gas, coal, nuclear) that produce energy on demand produce nearly the entire day, making the average price of electricity from these sources evenly weighted throughout the day. Because of this, you can not make a comparison of the price of wind/solar to anything else since it will be heavily distorted and give you a false sense that wind/solar is cheaper.
On top of that, a 2nd phenomenon of wind/solar makes the comparison even more distorted, that being you cant turn them off. If a wind/solar farm is producing energy, it will put it into the grid whether you want it or not, which could lead to an over supply if your capacity is large enough. If this happens, off-peak prices will crash causing the average price of wind/solar to drop even more. However, since wind/solar produce very little during peak hours, average prices of other sources will remain consistent, perhaps a slight drop, causing any comparison to be more unfair and misleading.
Now this is not necessarily a bad thing, so long as you are making enough money to cover your costs, but what tends to happen here is people fall into a trap. They falsely assume wind/solar is cheaper to produce based on the prices being charge, which have nothing to do with production, and start increasing their reliance on wind/solar. As they get into the 8% to 12% range of total energy coming from wind/solar, they will eventually start having supply shortages during peak hours since their required investment in base load sources gets, partially, diverted. This then causes the overall price of electricity to go up, but is only reflected in those sources producing at peak time. So the price of base load power goes up, while off-peak prices continue to crash, making wind/solar falsely look even more favorable. Due to this, if you do not recognize what is happening, people start to invest more in wind/solar, but since wind/solar is the source of the issue, they make the problem worse unknowingly.
This is where Germany and CA are currently at. 18.1% and ~25% of CA and Germany, respectively, lives in energy poverty. Their carbon footprint is just as abysmal too. It is all caused by too heavy a reliance on wind and solar.
Unfortunately I fear this is all coming soon to a place near you since Biden appears ready, willing, able and excited to jump in the same trap.
Insofar as batteries, did you miss my part about energy conversions loosing power? About 20% to 40% of power is lost when converting it into battery storage and then taking it out. This make batteries too inefficient to be worth wild, not to mention the amount of batteries you would need would be huge. I think CA has a total 6 minutes worth of battery power, and that includes every single battery in the state, all of them.
Although smart grids are important, typically what they best do is transfer power to other locales when there is an excess in one but a supply shortage in another. (It is bad to have the grid overcharged, so an excess of power needs to go somewhere.) This may seem beneficial for the excess energy produced by wind/solar at off-peak times, which is when they tend to produce power. The issue though is the price of electricity is already low and if you have too many wind/solar sources, the excess in electricity tends to crash prices at this time, which I mentioned before, to a point where the market price is often below the cost of production. So you lose money; this is a known problem for states/countries that have heavily invested in wind/solar already.
The main issue of cost is that you have to have a full 100% back up to meet the demand on the hottest day of the year. That's when air conditioners are being used. It requires the most electricity output in demand. If the wind isn't blowing on that hot afternoon in July, the grid relies on the regular generators. So you have to pay for complete backup for the entire system. You can't buy it from elsewhere because probably, that area is just as hot. That backup requires people and resources to build, man, and maintain. This is why green energy isn't cheap. You're paying for two sources. The charges quoted for green don't include the backup plant.
Con Ed, who handles NYC, charges a demand charge in addition to KWH usage charges for commercial accounts like office buildings, not for residential homes or apartments. So let's say a 60 story high-rise office building can consume 2000KW demand on the hottest day of the year with all the AC's working. Con Ed monitors their meters minute by minute. There is a separate demand charge for the maximum used every month even if it's only for 30 minutes. That's separate from the KWH consumption charge for total usage. The justification for demand charges from then utility is that they have to build and maintain large enough plants to handle the worse case situation, the hottest minute on the hottest day of the year. So the total demand for the whole city is required. Well, it's the same with green energy. The utility has to provide the maximum for the worse minute of the year even if the rest of the year they run at less than 70%. They can't count on the wind to be there at the worse time. NY Gov Cuomo proudly announced a year ago or so, NYS is buying billions of dollars of offshore wind. what he didn't mention, is that at the sale time, they going to match the demand with new traditional fossil fuel plants as a backup. The cost for those plants will be buried in surcharges on everyone's utility bill but not flagged as to the purpose of the surcharge. It's all a Ponzi scheme.
