Aside from cost constraints, perhaps the biggest hurdle facing nations seeking to embrace renewable energy is its unpredictability.

Re solar, the sun goes down.

Plant your biofuels patch and drought could wipe out an entire crop.

And the wind is variable.

Two seemingly constant natural cycles are tidal power and geothermal energy – if either decline, then major potential environmental changes could dwarf all other considerations.

Chile is investigating its geothermal options as an expensive but long-term bet to diversify