There is also promise from lowering solar cell costs, more efficient conversion systems for biofuels, and emerging fuel cell technology. Emerging technologies have the greatest promise but, at this time, the highest cost and the least field-testing. Solar energy, biofuels, and hydrogen fuel cells are all complementary to wind energy. Biofuels provide the ability to generate power on demand when the wind energy is not available. Hydrogen fuel cells have the potential to utilize hydrogen formed by electrolysis from a wind turbine when it is producing power in excess of demand.
Solar panels can produce power during hot peak energy days in the summer when the winds are low.
Wind turbines together with fuel cells or biofueled engines and battery banks can provide renewable energy on demand. The technology exists for efficient fully renewable energy systems. The only question then is of cost compared to grid-interconnected conventional energy. Economies of scale will reduce manufacturing costs of renewable technologies significantly. At the same time, escalation in fuel costs will raise the cost of energy for conventional technologies.