Massive Energy Storage Design for Renewable Electricity Generation Systems

It is widely recognized that a major concern with the installation of renewable energy systems is the fact that wind and solar sources are non-dispatchable. That is, the power produced from renewable systems is dependent on environmental conditions and is likely uncorrelated with the power demand from load centers. In contrast, fossil based sources typically have the ability to track demand, but depending on the technology possess limits with respect to response time (coal plants are slow, combined cycle turbines are faster and simple cycle turbines are fastest). Thus, many have advocated the use of massive energy storage systems to capture energy produced from renewable sources and then dispatch as load centers demand. An additional concern is the fact that renewable sources tend to be located far from the load centers (again in contrast to most fossil sources which are typically placed near demand). This issue is compounded by the fact that due to efficiency concerns the only viable energy storage systems is the pumped hydro-electric system, which in most cases must be located far from load centers. This combination of spatial and temporal mismatch with load center demand has caused many to worry about the stability of the electric power grid. Clearly, wide swings in power throughput over great distances will cause the weakest parts of the grid to fail.

To address both the spatial and temporal issues surrounding renewable power generation we have developed a scheme aimed at analyzing the capabilities of a regional power generation and distribution system. In particular, the scheme proposes a supervisory control law aimed at utilizing a mix of renewable and fossil sources along with energy storage systems to meet power load demands. This proposed control law takes into consideration not only the power output capacity of each source but also the rate at which power output can change (coal plants being slow and turbines being fast) as well as the storage capacity and efficiency losses associated with the pumped hydro system. In addition, the proposed scheme incorporates the maximum and minimum throughput limits on the distribution lines.