Too often, discussions about energy alternatives resemble a visit to a 1950s world's fair exhibition displaying exhibits of the wonderful technology of the future. Against one wall stand shiny replicas of new green machines – wind turbines, solar panels, fuel cells, hypercars, supergrids – alongside diagrams showing how environmentally benign they are. Against another are arrayed labeled bottles of new “substitutes” for oil, coal and gas – corn-based ethanol, rapeseed-based biodiesel, hydrogen cracked out of water, hydrocarbons extruded by algae.