Energy storage for hybrid remote power systems

Energy storage can be a cost-effective component of hybrid remote power systems. Storage serves the special role of taking advantage of intermittent renewable power sources. Traditionally this role has been played by lead-acid batteries, which have high life-cycle costs and pose special disposal problems. Hydrogen or zinc-air storage technologies can reduce life-cycle costs and environmental impacts. Using projected data for advanced energy storage technologies, LLNL ran an optimization for a hypothetical Arctic community with a reasonable wind resource (average wind speed 8 m/s). These simulations showed the life-cycle annualized cost of the total energy system (electric plus space heating) might be reduced by nearly 40% simply by adding wind power to the diesel system. An additional 20 to 40% of the wind-diesel cost might be saved by adding hydrogen storage or zinc-air fuel cells to the system. Hydrogen produced by electrolysis of water using intermittent, renewable power provides inexpensive long-term energy storage. Conversion back to electricity with fuel cells can be accomplished with available technology. The advantages of a hydrogen electrolysis/fuel cell system include low life-cycle costs for long term storage, no emissions of concern, quiet operation, high reliability with low maintenance, and flexibility to use hydrogen as a direct fuel (heating, transportation). Disadvantages include high capital costs, relatively low electrical turn-around efficiency, and lack of operating experience in utility settings. Zinc-air fuel cells can lower capital and life-cycle costs compared to hydrogen, with most of the same advantages. Like hydrogen systems, zinc-air technology promises a closed system for long-term storage of energy from intermittent sources. The turn around efficiency is expected to exceed 60%, while use of waste heat can potentially increase overall energy efficiency to over 80%