Other sources of energy are possible.
Tidal, This would be good near cities that have a good size high and low tide daily. Power could be made when tides come in and go out. This could vary with areas and times. It would cost more than wind or solar.
Geothermal. This would work near hot springs or inactive volcanos. One way I read of geothermal could be used was drilling a large hole down to near the hot mantle. Then injecting water through small pipe that would instantly turn to steam and come up around it in the larger hole. It would then be routed at ground level through a steam turbine to make electricity. This would work near where the mantle is closer to the earths surface. If all the power in the world was made this way it would take over 1,000 years to cool the inside of the earth 1 degree. So this is not to bad. Again kind of expensive, but no more expensive than drilling for oil or natural gas.
I think Iceland makes most of their electricity from geothermal as they have a lot of hot springs.
This method hasn't been given much thought.
Hydro. Most areas of the world have already built large hydo dams for production of electricity and flood control. Small areas aren't really being used. If America put small generators at all the old grist mills on creeks and small rivers it would increase hydro production by around 35%. This too is not bad. Most of these system would only produce enough electricity for a few homes in the general area. But, hey, why don't the power companies do this and give the land owners a discount on power if they allowed them to do this.
There is enough methane (natural gas) produced at feed stalls and dairy farms to supply all the natural gas in America. This is what you call carbon neutral. The methane is going to waste anyway, and atmospheric methane warms the air about 5-10 times more than carbon dioxide from burning it. So cows produce methane, it is saved with capture domes over feed stalls and dairy barns, filtered and pumped into the natural gas sysem nearby. It is burned, grass grows to feed the cows and uses the carbon dioxide, cows eat and expel the manure which has the gas in it, it is saved to be burned again, so it is carbon neutral. This gas would cost about 4 times as much as drilling or fracking for gas because of the labor involved in scooping up the cow manure and putting it into a domed area trapping the gas. The manure after it goes through the "heat" cycle releasing the gas, can then be bagged up and sold as fertilizer. This may happen sooner than later.
Nuclear. This invokes fear in people. However, if units are made smaller and modular that can be transported on trucks, one this size can power from 200-400 homes. They can be built to fuel up, go by themselves about 20 years, then shut down to be recycled and refueled and started up again. Breeder reactors should also be built as they can burn spent fuel rods from existing nuke plants and reduce the nuclear waste to about 10% of what it was. This can be done now.
Hydrogen gas is another idea. However it is the smallest atom and is subject to leaking more so than natural gas. There is currently no infrastructure to use. The idea is to use excess power from wind and solar to make the gas from water. One good thing is Germany is using hydrogen made from excess wind power in the North Sea to mix with natural gas. They found out they can mix up to 20% hydrogen with 80% natural gas with no effects at the natural gas burner tips. This is being done now.
I personally think excess solar or wind power could use the Sabatier process pulling carbon dioxide out of the air and forcing it together with water to make synthetic natural gas and oxygen. Elon Musk is going to use this process to fuel up his Mars rocket. It can be applied to earth as we already have the natural gas infrastructure in place, and is already being used to make electricity during peek demands.
