Financial considerations of using pumped hydroelectric storage to increase the penetration of wind and solar generation

Renewable power production is both variable and difficult to forecast accurately. These traits can make its integration into an electric grid problematic. But because its "fuel" is free, it makes economic sense to utilize renewable energy whenever it is available. When a power grid is unable to accommodate low marginal cost renewable energy due to a generator fleet that lacks sufficient flexibility, the energy is usually wasted and dispatchable fossil fuel generators are utilized instead. However, if a pumped hydroelectric storage (PHS, see the glossary for definitions of select terms) facility is used to time shift the renewable power production, the energy is transformed into a dispatchable resource. Because of this dispatchability, the power can be sold as "firm" generation which typically gets a higher price on the wholesale electricity market. This paper will address the financial aspects of using PHS to firm and time shift the inherently variable wind and solar power generation in the Mid-Atlantic States. The benefits that a PHS facility can offer to renewable power generators are many, but the biggest drawback to doing so is the high capital cost of PHS. In order to study the revenue streams of both PHS facilities and renewable power generators a computer model with one minute granularity was constructed. Electricity demand, power prices and wind power production were obtained from PJM's website for the year 2010. The NREL program PVWatts v.1 was used to generate the simulated solar power production which was combined with the PJM data and used as input to the model. Currently, various PHS configurations are being tested in order to determine their effects on the profits of the PHS facility and the profits of renewable generators. Preliminary results show that the relationship between PHS owners and renewable power generators could be beneficial for both parties. The extents of the financial benefits are largely determined by the dynamics of the applicable wholesale electricity market, the accuracy of the power production forecast for renewable generators, the power capacity, the energy capacity and the round trip efficiency of the PHS facility.