Solar panels can pretty easily produce way over 100°, like 1000°. All you need is a nichrome wire. 1000° sand has about 3× as much energy as 100° water by mas

Solar panels can pretty easily produce way over 100°, like 1000°. All you need is a nichrome wire. 1000° sand has about 3× as much energy as 100° water by mass, about 7× by volume. Water is cheaper but harder to contain.