In this work, we demonstrates the role of green ammonia as a renewable energy vector and the importance of innovative production technologies to cope with the intermittencies of the renewable energy supply. With a volumetric energy density more than twice that of compressed hydrogen, ammonia is positioned to become the key factor in enabling the hydrogen economy for medium to long term storage of renewable electricity. However, traditional ammonia production in the Haber-Bosch process is designed to operate with economies of scale and in a steady-state manner – incongruous with distributed and intermittent renewable energy. This talk first examines the potential routes to improving the agility of the conventional Haber-Bosch loop and the effect they have on the economics of producing ammonia from renewable electricity (i.e. solar and wind) as a function of the renewable energy supply characteristics. A novel route to making ammonia through integrating reaction and separation into a single vessel using absorptive separation – thereby removing the need for a recycle loop – is then presented. This process has the benefits of being modular for small-scale applications and fast ramping to follow fluctuations in energy supply. The novel single-vessel process is compared to the conventional Haber-Bosch process in terms of relative economics and application to a potential energy system.
The second part of the talk explores the role of ammonia, hydrogen and batteries (and their combination) to provide the electricity demand of St. John’s College in Cambridge, a residence for ~ 500 scholars in addition to offices, as a case study, where electricity is acquired either from solar, wind, or the grid. Ammonia plays a highly beneficial role in the energy system, but its relative role is dependent on the fraction of energy demand provided by renewables and the characteristics of the renewable energy source. More importantly, the use of agile ammonia production in the single-vessel process shifts the role of ammonia from storage over months if using the conventional Haber-Bosch to storage on as short of a time span as days when the process can ramp quickly.
