Design Optimization of an Ammonia-Based Distributed Sustainable Agricultural Energy System
Over the last few years, world-scale ammonia plants have been built, restarted, and relocated across the US. The last of these mega-projects began operations at Freeport in Texas last month. No more new ammonia plants are currently under construction in the US, and the received industry wisdom is that no more will begin construction. However, project developers and ammonia start-ups did not get this memo. With low natural gas prices persisting, they have not stopped announcing plans to build new plants. The difference is that the next tranche of new ammonia plants breaking ground will not be world-scale but regional-scale, with production capacities of perhaps only one tenth the industry standard. Despite using fossil feedstocks, these plants will set new efficiency and emissions standards for small-scale ammonia plants, and demonstrate novel business models that will profoundly alter the future industry landscape for sustainable ammonia technologies.
A chemicals technology firm in Belgium recently launched its vision for using green ammonia for "energy harvesting." The Dualtower is a new kind of wind turbine, under development by Arranged BVBA, that will use wind power to produce and also store hydrogen and nitrogen. These gases are "harvested" as ammonia, which becomes the energy carrier that allows large-scale renewable energy to be transported economically from remote locations with excellent renewable resources to centers of power consumption. Arranged's Dualtower is ambitious and, perhaps, futuristic but it illustrates three powerful concepts. First, the vast untapped scalability of renewable power. Second, the benefits of using ammonia as an energy carrier, to improve the economics of large-scale, long-distance energy transportation relative to every other low-carbon technology. The third concept is simply that every idea has its time, and now may be the time for ammonia energy. What was once futuristic, now just makes sense.
Last month's NH3 Energy+ conference featured presentations on a great range of novel ammonia synthesis technologies, including improvements to Haber-Bosch, and plasmas, membranes, and redox cycles. But, in a mark of a conference approaching maturity, members of the audience had at least as much to contribute as the presenters. This was the case for electrochemical synthesis technologies: while the presentations included updates from an influential industry-academia-government collaboration, led by Nel Hydrogen's US subsidiary, the audience members represented, among others, the new electrochemical ammonia synthesis research lab at Massachusetts Institute of Technology (MIT), and a team from Monash University in Australia. The very next week, Monash published its latest results, reporting an electrochemical process that synthesized ammonia with 60% faradaic efficiency, an unprecedented rate of current conversion at ambient pressure and temperature.
At the recent NH3 Energy+ Topical Conference, Grigorii Soloveichik described the future of ammonia synthesis technologies as a two-way choice: Improvement of Haber-Bosch or Electrochemical Synthesis. Two such Haber-Bosch improvement projects, which received ARPA-E-funding under Soloveichik's program direction, also presented papers at the conference. They each take different approaches to the same problem: how to adapt the high-pressure, high-temperature, constant-state Haber-Bosch process to small-scale, intermittent renewable power inputs. One uses adsorption, the other uses absorption, but both remove ammonia from the synthesis loop, avoiding one of Haber-Bosch's major limiting factors: separation of the product ammonia.
During our NH3 Energy+ Topical Conference, hosted within AIChE's Annual Meeting earlier this month, an entire day of presentations was devoted to new technologies to make industrial ammonia production more sustainable. One speaker perfectly articulated the broad investment drivers, technology trends, and recent R&D achievements in this area: the US Department of Energy's ARPA-E Program Director, Grigorii Soloveichik, who posed this question regarding the future of ammonia production: "Improvement of Haber-Bosch Process or Electrochemical Synthesis?"