2.2.6 Other Energy Storage Technologies

Pumped storage projects at the preliminary permit stage are considered speculative and, as of the time of this writing, none of these concepts have advanced beyond this phase.

Based on both their early stage of development and smaller project sizes, it is Black Canyon’s estimation that no pumped storage projects are currently proposed in Wyoming with an equivalent or superior level of viability as that represented by the Project.

Battery Energy Storage Systems (BESS) are increasing, primarily in the form of lithiumion batteries paired with PV solar. The cost of batteries has fallen significantly over the past several years, and costs are forecasted to continue to decline. Stand-alone battery projects are being constructed at the scale of hundreds of MW, and projects of 1 gigawatt have been proposed. These systems generally have storage durations of 2 to 4 hours.

Like pumped storage projects, BESS represent dispatchable capacity that helps to integrate carbon-free renewable resources and will thus see significant deployment across the market. Compared with pumped storage, BESS have the advantage of shorter development times, modularity, and flexibility of location. However, BESS have disadvantages compared to as the Project:

• Higher cost at longer durations of storage (duration will be increasingly important as renewable energy penetration increases); • Significantly shorter useful life (10 to 20 years, depending on cycling); • Degradation of storage capacity and efficiency through use (resulting in a higher fixed operations and maintenance [O&M] cost for augmentation); • Environmental impacts from mining of battery materials and the lack of methods for recycling spent battery cells; • Future supply risks associated with competition for materials (lithium and other materials) and policy considerations (e.g., reliance on raw materials and manufacturing in China). Evidence of this risk is seen in recent industry studies showing a slowdown in battery price decline due to rising commodity prices and reduced production; and • An inability to supply inertia to the grid.

Exhibit D includes an analysis of (Estimated Annual Value of Project Power) using lithiumion as a benchmark for comparison to illustrate how and why the Project represents a lower long-term long-duration cost of storage than utility-scale batteries when viewed through the energy or megawatt hours (MWh) lens.

New battery technologies, hydrogen-based systems, and mechanical systems (rail energy storage and systems that lift and lower concrete blocks) are at the demonstration or research and development stage and do not represent commercially available alternatives to the Project.

Compressed air energy storage (CAES) is the only other long-duration energy storage technology with an established track record, but this technology requires very specific and rare geology. The CAES technology available today requires the combustion of natural