Developing a fully decarbonized power grid will depend heavily on creative applications of many technologies.
Today’s most common renewable energy technologies — think solar photovoltaics and wind power — should be considered “energy-limited” or “non-firm,” in that they cannot provide energy on demand. Each is based on constraints inherent to the generation resource: whether the sun is shining, whether the wind is blowing and so on.
These technologies are increasingly being adopted as they have become more cost-effective, and they will go a long way toward helping meet ever-higher decarbonization mandates. But they cannot bring us to 100% carbon-free energy alone. In lieu of other forms of dispatchable and load-following, carbon-free power similar to conventional coal and natural gas-fired technologies today, energy storage will be essential to store carbon-free energy and deploy it when demand is there and supply is not.
And that’s where green hydrogen may have a role to play — especially as a hedge against severe weather.
The Storage Duration Factor
The process of producing hydrogen from water through electrolysis takes energy. When carbon-free energy supplies that energy, the result is green hydrogen. It might seem counterintuitive to use renewable power to produce another renewable fuel, but there is logic at work here.
For example, as more solar generation is developed to meet a higher percentage of power demand, eventually one reaches the point at which there is more solar production in a given moment than demand. This outcome is already being seen in regions with significant solar deployment, such as California, during certain times of the year. That excess power needs to be captured for consumption after sundown or when it’s cloudy. In the absence of a storage medium, that power is curtailed, essentially wasting it. But if electrolyzers can be powered by this surplus solar or wind and produce green hydrogen, it becomes possible to store that clean energy as hydrogen fuel and even transport it wherever it may be needed.
At present, lithium-ion battery electric storage systems are becoming more mainstream at utility scale. They provide short-duration storage: typically four hours or less. Another conventional storage technology is pumped hydro, which is typically designed and built for longer duration than batteries: 10-16 hours, give or take. Duration could be longer than that, but a larger reservoir would be necessary, driving up project costs. As a result, there are few pumped hydro facilities in existence that provide storage for much longer than a 24-hour period.
The duration for green hydrogen as a storage product depends on how large the storage facilities are. With a large enough tank or underground storage, hydrogen could be used to produce power for days. In theory, the future could see a system of pipelines that could ship hydrogen (or ammonia, a compound made from nitrogen and hydrogen) to turbines on demand, much like the current natural gas infrastructure.
Exploring the Economics
Green hydrogen is a potential new fuel stream that could go into fuel cells or a combustion turbine, similar to natural gas today. While a small level of hydrogen may be blended with most natural gas-fired combustion turbines today, many manufacturers are moving toward being able to produce power with 100% hydrogen by 2030.
Will it be economical for power production? The jury is still out on how green hydrogen will stack up when compared to other methods to balance supply and demand in a fully decarbonized grid of the future. Many complexities play into calculating a cost for green hydrogen in the current marketplace, but all indications are that natural gas is significantly less expensive. For short-duration carbon-free energy storage needs, utility-scale battery storage is less expensive than hydrogen today and likely in the future.
But there will be an ongoing need for longer-duration forms of storage, particularly to withstand weather events. Winter Storm Uri and its domino effect on the grid in Texas and the Midwest played out over several days in February 2021. Other severe weather events like hurricanes and ice storms can have impacts measured in days and weeks, rather than hours. Resilient power depends upon having a reliable power supply to ride out the interruption. There are not a lot of mature commercial examples of energy storage that are economically viable for that kind of duration. With sufficient storage and delivery infrastructure, hydrogen could have a role to play.
Lighting the Pilot
Few would argue that hydrogen will become competitive with other options for short-duration storage. It has greater potential in addressing longer-duration needs to maintain reliable, resilient power in the face of volatile and unpredictable weather.
There are other use cases for hydrogen today, and those could compete with power generation, altering the economics. Such possibilities should be kept in mind, since they could impact how things play out.
Meanwhile, the Orlando Utilities Commission (OUC) is moving forward with a demonstration project for green hydrogen. Although that project is not intended to develop hydrogen at a large scale, it will help OUC become familiar with the technology in terms of production, storage, transportation and consumption. Seeing how the demonstration project interacts with other resources will help OUC understand the role hydrogen could play as the community, state and nation move toward clean energy objectives.
Modeling storm impacts to a Florida electric utility’s system across thousands of projects helped build the business case for hardening infrastructure to maintain resiliency and provide maximum benefit to customers.