So is every fuel. Even the heavy unstable elements used in nuclear reactors formed at the heart of a star. Petroleum fuel is just converting solar energy from millions of years ago.
I wouldn't be surprised if current solar cells are more efficient, as bad as they are, overall.
I would. Even the best modern solar cells are only about 20% efficient, and the ones you can actually buy are only 15% efficient.
They can be used all year.
Not hardly. Maybe in Arizona and other sunshine states, but not everywhere. Ever been to the Pacific Northwest?
don't require large amounts of water and other resources to make them continue to produce.
But they do require tremendous energy and resources to manufacture. Even the 15% efficient industrial solar panels are very expensive; expect for them to take 20 years or more to pay for themselves.
Plants are much more efficient at gathering and converting solar energy, especially in less than optimal lighting conditions. To maximize its energy output, a solar panel needs to be connected to an expensive actuator called a "solar tracker" to keep the panel pointed at the sun. Plants do this automatically. Solar panels also lose efficiency as they heat up, but plants have no such restrictions and are self cooling through transpiration. Granted, only a portion of the energy plants collect goes into stored energy in sugars, starches, and oils. However, the rest is used for constructing the plant itself, giving them a much lower cost to produce than expensive solar cells. And some plants still store a large amount of energy indeed. Certain algae are more than half oil by mass.
So plants are much better than solar cells at capturing and storing usable solar energy. This shouldn't be surprising. Solar cells have only been around for 50 years. We've been able to quadruple their efficiency in that short time. However, plants have been around for billions of years, constantly improving through competition and natural selection. Or, if you're of a more religious persuasion, they were handmade by God himself. Either way, we cannot expect to do better with a man made device after only a few decades.
Even if we manage to make 100% efficient solar panels, there's still the problem of storing and transporting the electricity produced. Solar panels need large, expensive, toxic, and inefficient batteries to store the power they generate. You can store vegetable oil in a bucket.
Right now oil is cheaper than all those other means. Until that changes, oil will remain our primary energy source.
But oil has many many hidden costs, not the least of which is having to bow and scrape before a bunch of religious nutjobs. The petroleum industry is also heavily subsidized to keep prices down. What you don't pay at the pump, you pay every April 15th. At the same time, the agricultural industry is also heavily subsidized, but to keep prices up. Vegetable oil is only $5 a gallon because of corporate farm subsidies to limit vegetable oil production. Without the subsidies on each, vegetable oil is quite competitive with fossil oil.