Build solar thermal troughs, similar to those built in Egypt in 1910, in the Sahara and other deserts next to the sea. Heat the salt water to steam to power turbines. Two products, electricity and fresh water. Use the fresh water in permaculture in the deserts, plant trees, create microclimates that enable transpiration from the trees to create more fertile areas. Use the electricity to create sustainable cities.
We have the understanding for all of this. I am only describing a replicable von neumann machine.
Clive Durdle's Blog 