As the US continues to add intermittent renewable energy sources such as wind and solar to the mix, maximising the use of stable, reliable and efficient clean energy sources is vital. Hydropower is one of the most reliable sources of renewable energy. 

Idaho National Laboratory (INL) has joined forces with Pacific Northwest National Laboratory (PNNL) and Idaho Power to evaluate the feasibility and advantages of making hydropower more flexible by producing hydrogen at existing hydropower plants.

Integrating hydrogen production with hydropower can enhance grid stability through energy storage, reoxygenate water for downstream environmental improvements and support decarbonising energy production in Idaho. The data, models and analyses developed through this partnership will help determine the viability of hydropower and hydrogen integration, both for Idaho and facilities across the US.

“INL and PNNL will evaluate the coupling of electrolytic hydrogen production technologies with hydropower plants to identify scenarios that could help Idaho Power achieve its goal of providing 100% clean energy by 2045,” says Brett Dumas, Idaho Power’s Director of Environmental Affairs. This approach will help maximise use of the clean energy produced by Idaho Power’s 17 hydroelectric power plants. 

The benefits

Most renewable energy generation technologies face the challenge of varying power output. Hydropower generates power more consistently than other renewable energy sources and adding hydrogen production can increase flexibility to help balance wind and solar generation. This is especially important during hours of peak electricity use. 

Hydrogen storage could benefit the energy grid by storing electricity in the spring, when hydropower is abundant, and making it available during periods of peak demand in the summer. In the spring, melting snowpack increases streamflow used for hydro generation when temperatures are mild and energy demand is relatively low. Harnessing some of that hydropower to run electrolysers for hydrogen generation would preserve some of that energy for the hot summer months when air conditioners and irrigation pumps drive up electricity demand.

Hydrogen produced by using excess electricity from hydropower can be easily converted back into electricity when needed. There are two methods of generating power from hydrogen: fuel cells or combustion turbines fueled either exclusively 1) by hydrogen or 2) a hydrogen and natural gas blend. 

Storing and using hydrogen in times of peak energy demand can help with the transition toward clean energy by reducing the need for supplemental fossil-based power generation from outside the hydropower plant. 

“By capturing the off-peak energy production as hydrogen, the hydrogen can be re-electrified during peak energy demand,” said INL’s Daniel Wendt, principal investigator and researcher on the project. “Storing hydrogen as a fuel could help stabilise the grid and offer a cleaner alternative to fossil-fuel backup power generation. This approach could give electrical system operators greater flexibility to ensure reliable and economical service.”

Addressing depleted oxygen 

Dissolved oxygen in a river is necessary for fish and other aquatic species. The excess oxygen produced as a byproduct of hydrogen generation could also address water quality issues in rivers when reservoirs behind dams may have low levels of dissolved oxygen, particularly during summer and early fall. 

One of the approaches for increasing the dissolved oxygen levels downstream of hydropower plants involves spilling water from the reservoir into the river below. The spilled water cannot be used for electricity generation. INL and PNNL researchers will evaluate the potential of using excess oxygen generated by the hydrogen generation process to increase oxygen levels of water in rivers with hydropower plants. 

“Idaho Power is already seeing positive results from adding oxygen into the water flowing out of Brownlee Dam in Hells Canyon,” Dumas said. 

By using the excess oxygen gathered from the electrolysis process, hydroelectric plants can increase oxygen levels downriver without spilling water from the reservoir or needing to purchase oxygen for dissolved oxygen level mitigation. 

Making it a reality

INL, PNNL and Idaho Power are taking the first step toward realising these benefits by analysing the economic and environmental impacts of integrating hydrogen production with hydropower. The project team will use advanced modelling and analytical tools to explore various deployment scenarios and maximise the benefits of hydropower-based hydrogen production. 

Researchers will evaluate the cost of producing hydrogen using different electrolyser technologies. The calculations will factor in variations in the supply and market pricing of the electrical power produced by various hydroelectric assets. 

The different characteristics of electrolyser technologies, such as energy efficiency, capital cost and their ability to ramp from standby to full hydrogen production, are important factors to consider in selecting the best technology for different hydrogen production and use-case scenarios. The team will consider the costs of hydrogen storage and transporting the hydrogen product to other prospective end-use applications, such as transportation fuel or chemical production.

Finally, the team will investigate dynamic operating strategies that optimise the environmental and economic benefits of a prospective coupled hydropower plant and hydrogen production facility. The team also hopes to satisfy constraints associated with hydropower resource availability, power plant and electrolyser capacities, and the demands associated with different hydrogen use cases. 

“To effectively schedule hydrogen production, advanced modelling and optimisation techniques are required to account for both energy shifting opportunities and oxygen needs subject to both system- and component-level constraints,” said Di Wu, a chief research engineer and the technical lead at PNNL. 

Researchers at INL will use a Department of Energy software tool proven to be effective for techno-economic evaluation of other hydrogen production and usage applications. The tool, Hydrogen Analysis (H2A), can perform screening studies of the most promising electrolysis technologies and hydrogen use cases. H2A allows the user to access all calculations and check intermediate results.

PNNL researchers will build on the results of the screening study to model and optimise the hydrogen production system. Through the Hydrogen Energy Storage Evaluation Tool and data analysis, INL and PNNL researchers will determine how to implement the right set of technologies to achieve the best performance.

“While hydropower and hydrogen both offer immense economic and environmental benefits on their own, combining their use in one application offers new opportunities for enhancing grid stability, improving environmental outcomes and creating a cleaner energy economy,” Wendt said.

This article first appeared in International Water Power magazine.