Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.
The efficiency and cost of renewable solar and wind power systems using intermittent resources could significantly be improved by developing low cost, high efficiency and more sustainable energy storage systems. A comparison study between energy storage options is presented in this paper. The energy storage options include: (1) electro chemical storage: lead acid, Li-ions, Nickel-Cadmium, Nickel metal hydride, Sodium Sulfur, and vanadium flow batteries; (2) electro-magnetic energy storage: super capacitors and super conducting magnetic energy storage; (3) hydrogen storage: onboard systems and utility scale; (4) mechanical storage: compressed air, flywheel, pumped hydro, spring (composite and metal), and (5) thermal energy storage. The resource intensities and operational parameters of the energy storage options are compared in this study. The main objective is to review the various types of storage techniques and their characteristics and to determine the most appropriate technique for solar and wind energy applications: energy storage system with suitable discharge time, lowest resource intensities, best operation performance and lowest cost. Based on the results obtained in this study, super capacitors, super conducting magnetic, and flywheel energy storage systems could be a good option for solar and wind applications: they offer fast discharging/charging times, greater performance (high specific power, high cycle efficiency, high cycle life and they) and are very attractive with respect to the operating costs.