Renewable wind energy can be used to make ammonia. However, wind-generated ammonia costs about twice that made from a traditional fossil-fuel driven process. To reduce the production cost, we replace the conventional ammonia condensation with a selective absorber containing metal halides, e.g., calcium chloride, operating at near synthesis temperatures. With this reaction-absorption process, ammonia can be synthesized at 20 bar from air, water, and wind-generated electricity, with rates comparable to the conventional process running at 150-300 bar. In our reaction-absorption process, the rate of ammonia synthesis is now controlled not by the chemical reaction but largely by the pump used to recycle the unreacted gases. The results suggest an alternative route to distributed ammonia manufacture which can locally supply nitrogen fertilizer and also a method to capture stranded wind energy as a carbon-neutral liquid fuel.
Bibliographical noteFunding Information:
This work was primarily supported by the U.S. Department of Energy (ARPA-E, USDOE/DE-AR0000804), by the Minnesota Environment and Natural Resources Trust Fund (LCCMR,/ ML 2015, CH 76, SEC 2, SUBD 07A), and by the MnDRIVE initiative of the University of Minnesota (MNT11). Other support came from the Institute for Renewable Energy and the Environment (IREE, RO-0001-12) at the University of Minnesota and by the Dreyfus Foundation. Michael Ho helped with some calculations.
- Energy storage
- Metal halides