As wind and solar power make up an increasingly large share of energy production in the U.S., finding ways to store the intermittent energy they create is critical for when the wind isn’t blowing and the sun isn’t shining.
The University of Minnesota is working on a novel way to help solve the storage puzzle for renewable energy: by creating ammonia.
Michael Reese, director of renewable energy at the U’s West Central Research and Outreach Center, said the U has previously turned wind power into ammonia that can be used for fertilizer and even to fuel agricultural equipment.
Now, the research center is asking for money from the federal government and the state Legislature to fund a deeper dive into energy storage, and at least some local lawmakers appear to be interested. Republicans who control the Minnesota Senate included $10 million for the project in a recent budget proposal.
Why ammonia?
Reese said there has been growing interest in using ammonia to reduce dependence on fossil fuels as of late, particularly in agriculture. Ammonia is widely used as nitrogen fertilizer, and it’s typically created with natural gas or, in some cases, coal. About 1 percent of global greenhouse gas emissions are associated with the production of ammonia and nitrogen fertilizer, Reese said.
In 2013, the U built a plant in Morris that can use wind power to create ammonia, which is then used for fertilizer. It was the first of its kind in the world.
But ammonia isn’t just for fertilizer. Ammonia can be stored as a liquid and burned in an engine, a generator or used in a gas turbine. The Morris center has used ammonia to power tractors and is researching ammonia as fuel for drying grain. Ammonia can be also used in a fuel cell, which acts as an alternative to a battery or gas tank in cars, or converted into hydrogen and used in a fuel cell or mixed with traditional natural gas for heating.
This spring, Senate Republicans included $10 million in their budget plan for the ammonia project, funded by fees Xcel Energy pays to store nuclear waste in Minnesota. The money would allow the research center in Morris to use ammonia, made from renewable energy, to fuel gas turbines, portable power generators known as gensets and fuel cells, as well as to research safe ammonia storage.
Reese said the outreach center and the chemical and mechanical engineering departments at the U have also applied for federal grant money to use with partners that include the Research Triangle Institute in North Carolina, ammonia producer Casale, Shell, General Electric and a few utilities such as Xcel Energy.
Ammonia has some advantages over batteries and hydrogen in the energy storage field. Reese said batteries can be expensive on a large scale. Using power to create hydrogen is efficient for short term use, such as capturing wind energy produced at night to meet higher energy demand during the day. Hydrogen, however, is also costly to store and transport. Ammonia is easier and cheaper to transport, and can be converted to hydrogen after transportation.
“Combined with hydrogen, ammonia provides the most efficient way to store renewable energy seasonably over long periods of time,” said Prodromos Daoutidis, a professor and executive officer at the U’s College of Science and Engineering, during a March hearing before the Senate’s Energy and Utilities Finance and Policy Committee.
Reese said they would use federal grant money to work on efficient production of ammonia and hydrogen from wind to make it cheaper to use on a smaller scale near wind farms compared to the current “mega-scale” centralized production using fossil fuels.
There are many potential applications for the technology. It could be used as a power system, by, for example, a farm cooperative. A local rural electric utility might want to accommodate a farm that might need a tremendous amount of energy during a short harvest period, for instance, and generators running on ammonia could supply that power rather than building out infrastructure over thinly populated areas from a central location.
Another use might be lake homes, Reese said. Wind energy is mostly produced at night and can be lower in summer months, when there is high power demand. When people come to their cabins, energy demand spikes when they start up air conditioners, turn on lights and cook. That can be difficult to manage. Ammonia could be a “non-wire” solution to supply power to substations that serve cabins and vehicle charging stations, Reese said.
Seasonal storage will be crucial to creating an energy grid more reliant on renewable energy. And in general, Reese said, ammonia can help bring intermittent wind power from rural areas to more populated regions. “The potential is there for using green ammonia for large scale storage, for grid stabilization” and more, Daoutidis said during the March hearing.
In a letter to the Legislature, Xcel Energy Minnesota president Christopher Clark said the ammonia project “holds great promise” in the energy transition. “While batteries will be a key technology for short-term energy storage, the much longer shortfalls in renewable generation we have recently experienced during polar vortex periods point for the need for economical long-duration storage — for which hydrogen and ammonia are promising options,” Clark wrote. “We believe the research conducted at UMN may lead to significant energy storage solutions, perhaps sooner and at a lower cost than battery storage technology.”
Reese said there’s also interest in using ammonia as fuel for medium-to-large scale transportation such as trains and shipping.
Ammonia comes with downsides. It’s hazardous to inhale and it can burn eyes or skin if released. When combusted, such as in a generator set or a gas turbine, ammonia also emits nitrous oxide (NOx), a potent greenhouse gas that can be worse than carbon emissions for climate change.
Reese said those NOx emissions are serious, but can be mitigated (though at a price). No greenhouse gases are released if ammonia, or hydrogen, is used to power a fuel cell. Ultimately, Reese said the world is moving away from engines and toward fuel cells.
Support at the Legislature
The $10 million proposal is not assured to be approved by the Legislature. Democrats, who have a majority in the state House, have their own slate of proposals for how to spend the Xcel nuclear waste fees, which are deposited in what’s known as the Renewable Development Account.
The House budget plan includes a measure requiring the Public Utilities Commission to calculate the greenhouse gas emissions associated with innovative energy resources including power-to-ammonia, and it includes a bill allowing natural gas utilities to explore using hydrogen from ammonia as fuel if it lowers greenhouse gas emissions.
State Rep. Jamie Long, a Minneapolis DFLer who chairs the House’s Climate and Energy Finance and Policy Committee, said green ammonia is a “really promising and interesting area of research,” and said it could be a good way to replace natural gas systems that are critical to some industrial uses.
Reese said there will be some work in Minneapolis and noted the U is a large power customer for Xcel.
Sen. Torrey Westrom, an Elbow Lake Republican who first sponsored the bill that would give money for the ammonia project, praised the outreach center in Morris as a “real leader” in this renewable energy sector.
But Westrom said the research station is great for refining technology to make it efficient and affordable. This type of renewable energy is “closely connected to agriculture and rural landscapes,” he said. Westrom chairs the Senate’s Agriculture and Rural Development Finance and Policy Committee and also represents a district at the Legislature that includes Morris and the U’s outreach center.
“If we could create that natural fertilizer here, that’s a real win win potentially,” Westrom said. “The mind can grow from there of what kind of opportunities we could have with renewable energy if ammonia could become a more viable source of renewable energy.”
