Solar and wind cannot be switched on.
Sure they can. If storage has been installed. Tesla is building dispatchable solar in Hawaii and another company is building dispatchable solar in Arizona.
There are a couple of questions which will need to be answered later. How much storage and what kind? Most grids have far too little wind and solar to worry about storage now.
if you want wind and solar, you want guaranteed payments for them
Not needed. If there's as much wind and solar online as the grid can use no one is going to build an additional wind or solar farm unless they can sell for less than another wind and solar farm. That could happen, that's what happens in open markets. Right now we see NG and wind putting coal out of business because NG and wind are cheaper. There's always a risk in business that someone will be able to undercut your price and take your market away.
In the absence of large-scale storage (or a highly geographically diversified grid) this is always going to be a problem, even more if there is major capacity overbuild to increase the renewables production during low wind/sun days.
In some cases it might be cheaper to overbuild than to store. I found ERCOt hourly demand and wind generation for 2014. I simplified it to daily averages and assumed enough 'one day' storage to even out supply/demand on a daily basis.
Then I calculated the number of days when the average annual production did not meet the daily demand. 206 days.
Next I 'overbuilt' 100% (2x). The number of underprovided days dropped to 71.
Then I 'overbuilt' by 200% (3x) and the number dropped to 32.
Suppose all Texas had to work with was onshore wind in the Panhandle. And suppose wind drops to $0.02/kWh, unsubsidized (it may be going lower). Texas could build 3x as much wind and cover all but 32 days a year. Their cost would be $0.06/kWh - about the cost of CCNG.
By the time one throws in solar and coastal/offshore wind Texas might be able to build an all wind/solar grid with only enough storage to even out 24 hour cycle supply/demand differences. No 2, 3, 14 day storage needed.