Comment by ianburrell

There aren't enough trees to support industrial civilization. Britain was burning coal before the Industrial Revolution and would have quickly exhausted all land for wood. Wood is useful for other things, buildings and paper would compete with fuel. It is the same problem with turning food crops into fuel.

Solar doesn't require high tech. We use solar panels cause we are good at making circuits. But solar thermal with mirrors should work for lower technology. They wouldn't have the chips for controlling mirrors, but could have some system of central control or just have people move them.