Hartley, Peter and Kenneth B. Medlock III (2014), "The Valley of Death for New Energy Technologies."

It is often claimed that scarce financing prevents promising new energy technologies from attaining commercial viability. We examine this issue using a dynamic intertemporal model of the displacement of fossil fuel energy technologies by non-fossil alternatives. Our model highlights the fact that since capital used to produce energy services from fossil fuels is a sunk cost, it will continue to be used so long as the price of energy covers merely short-run operating costs. Until fossil fuels are abandoned, the price of energy is insufficient to cover even the operating costs of renewable energy production, let alone provide a competitive return on the capital employed. The full long-run costs of renewable energy production are not covered until some time after fossil fuels are abandoned.