REA informed the researchers of the maximum genset power output its distribution grid could accommodate. Additionally, the genset would need to be safe and leak resistant, particularly for applications in residential areas.
REA and GRE have given Northrop and Kane a valuable perspective on the unique power delivery requirements in rural regions, where electric cooperatives typically use trailers to transport gensets over long distances. This information enabled the researchers to adapt their ammonia genset design for rural areas, thereby significantly broadening the potential number of applications for the technology.
Commercialization is close. Northrop and Kane plan to demonstrate their first 250-kW ammonia-fueled genset in 2024. WCROC’s production facility will supply the green ammonia for field tests on REA’s grid.
In the meantime, Northrop and Kane are developing safety measures to prevent ammonia leaks and minimize harmful emissions. While ammonia-powered gensets have no carbon dioxide or particulate emissions, they can emit nitrogen oxides (NOx), nitrous oxide and ammonia. The researchers’ work to date has shown optimizing the ammonia combustion process can reduce NOx emissions to levels comparable to that of a diesel engine. They are working with a catalyst supplier to reduce combustion emissions of NOx, nitrous oxide and ammonia to near zero.
Northrop and Kane expect ammonia gensets to take 30 seconds to 120 seconds to ramp up to full power — like fossil-powered gensets. Ramp-up may be a bit longer when ambient temperatures drop below 0°F (-18°C).
The researchers expect ammonia and fossil gensets to have comparable maintenance costs as well, though ammonia gensets potentially offer some advantages on maintenance. Unlike diesel and gasoline, ammonia fuel does not degrade or produce ash and soot when burned in engines. As a result, oil in the genset is less likely to foul, or become dirty, and can last longer. That said, the researchers have not conducted long-term run experiments on ammonia gensets and concede there is still more to learn about their durability.
According to Kane, a utility would need about 6200 gal (23,470 liters), or 16 tons, of ammonia to run a 250-kW ammonia genset for 100 hours continuously. A semitruck could transport to the genset site nearly double this amount with an 11,500-gal (43,532-liter) tank on a trailer. The truck can refill a genset’s fuel tank while the genset is generating power.
Synergies With Agriculture
The Midwest’s agricultural industry relies heavily on fertilizer made with conventional, fossil-based ammonia. As a result, the region already has extensive, mature infrastructure for safe, reliable ammonia handling, storage and transport. Ammonia safety is important because the material can be corrosive and toxic if inhaled.
For REA, GRE and other Midwest utilities exploring green ammonia applications, intriguing possibilities exist for collaboration with agricultural entities and fertilizer companies on ammonia production, storage, transport and use.
For one, the timing of ammonia use across the utility and agricultural sectors is potentially complementary. REA would need ammonia in the summer for lake country, fall for crop drying and winter for areas with high heating demand — times of the year when farms typically do not use fertilizer. Spring is the peak fertilizer season for farming. What is more, conventional ammonia potentially can be replaced with green ammonia without significantly disrupting agricultural operations.
A team of University of Minnesota researchers have envisioned a system that couples the agricultural and energy sectors by taking advantage of the synergies between them. The system would use renewable energy for several applications across the two sectors:
- Produce ammonia for fertilizer, tractor fuel and crop drying
- Serve local electricity demand
- Export excess power to the grid.
For such a system to work, its design and scheduling would need to be optimized carefully to account for the variability of renewable generation as well as variable power and ammonia demand across hourly and seasonal time scales. The researchers have demonstrated the promise of an optimization approach. The demonstration used a case study in which wind turbines serve demand for ammonia fertilizer and fuel at WCROC’s farm as well as serve electric demand at the adjacent University of Minnesota campus in Morris.
For GRE, green ammonia production offers a potential opportunity to absorb excess wind generation on its transmission grid, balance energy supply and demand, and avoid back-feeding because of high wind penetration. The ammonia can be used to electrify tractors and other fossil-powered agricultural end uses. Meanwhile, agricultural ammonia storage facilities could serve as an electricity sink.
One of REA’s members operates a large ammonia storage facility. If GRE or REA ever need to store energy by producing and storing green ammonia, they could leverage that member’s capabilities rather than having to reinvent the wheel and deploy their own storage facilities.
By taking advantage of these synergies between industries, utilities like GRE and REA have a unique ability to help agricultural producers reduce their carbon emissions. In fact, WCROC research has shown displacing conventional ammonia with green ammonia in fertilizers and crop drying could lower agriculture’s fossil energy consumption by nearly 80%.
Final Thoughts
It has been a worthwhile experience to combine multiple academic research avenues to address a real-world utility challenge. On one hand, REA and GRE have benefited by gaining valuable insights on a zero-carbon solution to a costly problem. On the other hand, the on-the-ground perspectives of REA and GRE have helped University of Minnesota researchers to refine their assumptions and make their investigations less theoretical and more practical.
Advances in ammonia genset applications by REA, GRE and the University of Minnesota can inform utilities across the U.S. — particularly in agricultural regions — in their grid operations and planning. Ammonia’s potential for multifaceted uses could enable utilities to leverage existing fertilizer infrastructure to boost the use of clean energy while solving local grid challenges.
Al Haman ([email protected]) is CEO of Runestone Electric Association (REA), an electric distribution cooperative serving 15,000 accounts in rural Douglas, Pope and Grant counties in west central Minnesota. Prior to joining REA, he was CEO of STAR Energy Services from 1999 to 2020 and an electrical engineer at Otter Tail Power from 1991 to 1999. He is a graduate of North Dakota State University and a registered professional engineer in Minnesota, North Dakota, South Dakota and Wisconsin.
Jeff Haase ([email protected]) is director of member services, distributed energy resources and end use strategy for Great River Energy (GRE). He works with GRE’s member-owners on growth and distributed energy resource strategies related to energy efficiency, electrification, economic development and demand response. He focuses on optimizing GRE’s program offerings and quantifying their benefits to member-owners. He has a BSME degree from the University of Minnesota and is a registered professional engineer.
