The high hydrogen density of ammonia (NH3) makes it a very promising green energy storage and distribution media. In fact, among practical fuels ammonia has the highest hydrogen density including hydrogen itself in both the cryogenic and compressed forms. Moreover, since the ammonia molecule is free of carbon atoms (unlike many other practical fuels), combustion of ammonia does not result in COx emissions. Ammonia is already a widely produced and used commodity with well established distribution and handling procedures, making the introduction into the commercial sector an easier process.
The combination of high hydrogen density and elimination of carbon emissions make ammonia an attractive candidate for power generation. Among practical fuels, ammonia has the highest hydrogen density including hydrogen itself (see table). The two major disadvantages of ammonia are its low energy density compared to hydrocarbon based fuels and its toxicity. Both of these shortcomings have hindered the development of ammonia as a transportation system fuel especially for small vehicles such as automobiles.
However, the low energy density and toxicity issues are not critical for the use of ammonia in power generation systems. For a power generation system, for which the storage space is readily available, the energy density is not the determining factor for the fuel selection, as the cost per BTU and emission levels are typically the important parameters. With the new energy efficient methods of producing ammonia (on the cost per BTU basis), ammonia produced using renewable energy sources would be competitive with the fossil-based fuels (even at today's relatively low prices). The toxicity issue is also not as critical for power generation systems since the fuel will be handled by professionals following well established handling procedures.
The feasibility of ammonia fuel depends on two factors: 1) development of green and efficient methods of synthesizing ammonia and 2) development of technologies to burn it in power generation plants. The first aspect is currently being addressed by other commercial entities, and ammonia production units based on the Solid State Ammonia Synthesis (SSAS) technology is believed to be commercially available in the near future. Once technologies that can burn ammonia in gas turbine systems have been established, it is believed that the ammonia will become a viable green alternative fuel.
SPG has [BE1] evaluated ammonia as an alternative fuel for gas turbine systems which are widely used in power generation applications. It is believed that the existing gas turbine systems can be converted to burn ammonia instead of liquid fuels or natural gas.
Ammonia is extensively used as a fertilizer, either directly or as a feedstock to other forms of fertilizers. The production of ammonia in the US has been declining, resulting in the import of this strategical commodity from foreign sources. The potential use of ammonia as a fuel will stimulate its production in the United States in larger quantities, thereby significantly reducing its cost (either by the development of new technologies or by economics-of-scales) and reducing the dependency on the foreign sources.
Ammonia as an Enabler for Stranded Renewable Energy Sources:
Stranded Renewable Energy Sources: Most of the renewable energy sources such as solar, geothermal or wind are not accessible by the existing electric grid system.
Extending the grid to remote areas is NOT economical. In most cases extension of the grid system is politically difficult (if not impossible).
Ammonia as an energy carrier has the potential to solve the Stranded Renewable Energy problem.
Using a synthesis method such as SSAS, ammonia can be produced at the stranded site from water and air.
The produced ammonia can be shipped via trucks, railroad or pipelines to the power generation plants to generate electricity.