2C3: Obermeyer Pump Turbine: Cost Effective Pumped Storage Hydropower
July 13, 2022
Equipment and Technology
Obermeyer Pump Turbine: Cost Effective Pumped Storage Hydropower Reversible pump turbines for pumped storage hydropower are generally installed well below tailwater level in a cavern, or shaft, powerhouse to provide sufficient pressure at the inlet to prevent cavitation. Such facilities are expensive and require suitable geology. The Obermeyer pump turbine seeks to reduce powerhouse costs by utilizing a runner with a toroidal flow path that redirects the water approximately 180 degrees. This configuration allows the Obermeyer pump turbine to be mounted at the bottom of a “well” where the water enters and exits the pump turbine from above. This significantly reduces the required civil and concrete work at site. The simple underground structure may be constructed under a wide range of geological conditions. Geological risk is further mitigated by the fact that a limited number of borings can reliably characterize the entire excavation. This simplified storage solution creates large-scale grid storage opportunities with advantages over conventional and ternary-type configurations. Simplified construction and reduced installation costs can tip the scales at sites that were previously infeasible. The relatively small footprint of the Obermeyer pump turbine makes it well suited to being utilized in existing hydropower sites and at dams that are not currently being used for power generation. Pumped storage capability may be added to existing hydro power stations without the need for large shaft or cavern powerhouses that may not be feasible adjacent to an existing dam and powerhouse. Overall costs are particularly attractive at existing hydro sites where the dam, reservoirs, penstocks and switchyards are already in place. One would need to modify the penstock to introduce the Obermeyer pump turbine, but this would be at a fraction of the cost of a new penstock. The Obermeyer pump turbine could be used as a pump only with generation via the existing hydro turbine, or it could be used as a pump turbine which would increase the site generating capacity. As part of the U.S. Department of Energy Water Power Technologies Office’s HydroNEXT initiative, Obermeyer Hydro was awarded $1.18 million to further develop this advanced pumped storage hydro configuration. This effort included a cost analysis of an Obermeyer pump turbine site compared to that of a conventional pump turbine. The results show a 33% reduction in overall installation costs with most of the savings coming from reduced civil costs and underground work. As more solar, wind and nuclear generating facilities are constructed, it will be beneficial to have a greater capacity for electrical power storage. It may be advantageous if the storage solution is similar in size to the facility that is generating the electricity. This allows for less dependence of other grid level activities to provide a consistent, reliable source of electricity. The Obermeyer pump turbine is well suited to provide a pumped storage solution for unit sizes down to 1MW and even lower. With reduced installation costs, this may prove attractive for the operator of a renewable energy site. It is the believed that the reduced cost for installation makes the Obermeyer pump turbine attractive to utilities and power companies that are looking to minimize storage installation costs. The Obermeyer pump turbine may also make pump storage hydro attainable for developing countries. The technology could also be utilized in a modular fashion were one or two units are initially installed at a site. As budget allows and power demands increase, the number of units could be increased without the significant investment in a new cavern, or shaft, powerhouse.