> at a rate that’s possibly less than what it cost to buy fuel?

You might need to sit down for this. The wind farms don't use fuel. Wind just happens, it's a natural phenomenon that has no real regard for our stupid "wind farm" even as we're harvesting gigawatts of power the wind doesn't ccare.

If you were thinking "Wait I thought all the providers have these contracts, not just renewables" then er no, they're a subsidy, the CfD is a subsidy scheme. That cheap to make, expensive to run open cycle gas turbine some asshole put on a local industrial estate doesn't get a CfD, it can offer to sell the resulting electricity at market prices, and really the big problem is as you observed, that's possibly less than what it costs to buy fuel. Yeah, it is, bad idea to keep building Open Cycle Gas Turbines I reckon. Sure enough the UK almostly exclusively has more expensive to build but cheaper to run Combined Cycle plants.

CfDs are used to subsidise renewable future power. A long term energy independence strategy. Even if you don't care about the planet warming and the sea levels rising you won't be burning all this gas in a thousand years 'cos there's not enough gas. Whereas the sun will shine until long after we're gone, and the accompanying winds won't stop either.

The size of the subsidy varies, if you're building a pilot plant of a new technology that you're sure will revolutionize clean energy but, alas, no-one ever made one that worked before, the government might be willing to pay you four or five times as much money for your energy, partly because they're not expecting you to actually make any energy because you will likely fail. If your plan's big problem is that it's way less mechanically reliable than you'd like, this is a big incentive to incrementally improve that reliability. If your device that involves being in and out of an incredibly powerful tidal stream of corrosive sea water at freezing temperatures makes power but doesn't crack, tear, fall to pieces or explode in the scheduled period of operation you're that much closer to actually having a useful technology and paying you five times over the odds for the MWh you did make is a reasonable price.