Direct: Ammonia is currently used on a large scale in fertilizer, as a precursor for nitrogenous compounds and as a cleaning agent. Although the energy content is lower than that of fossil fuels, ammonia can be used as a fuel in converted diesel generators, or even in large solid oxide fuel cells (SOFC). Furthermore, gaseous ammonia can be burnt in gas turbines, similar to natural gas.
Indirect: Ammonia, a hydrogen carrier, can be cracked to release the hydrogen kept within. This allows the use of hydrogen in all its applications.
It would take 10 times the amount of energy to liquify hydrogen as opposed to converting it to ammonia. The temperature needed to keep hydrogen liquid is far lower (-252°C) than it is to keep ammonia liquid (-33°C), thus increasing storage costs. Because of the density difference, there is more hydrogen present in 1 litre of liquid ammonia (in terms of weight), than in 1 litre of liquid hydrogen. Additionally, as one of the oldest chemicals to be produced on a commercial scale, ammonia Infrastructure (physical and regulatory) for transport, handling and storage on a large scale has already been developed.
For long distances, large ships/tankers carrying ammonia are most efficient. Ships using ammonia as a fuel (which are already being built) while transporting it will not impact the carbon footprint of the ammonia production.
We do not yet have exact figures, but since the cost improvements are so large, they will be without a doubt cost efficient. In our example systems, the cost reductions range between 10-25% of the original CAPEX, which is significantly more than our price estimates for DCPV storage. Further cost reductions can be achieved by structurally integrating DCPV storage, saving material use and CAPEX. For each project there is a specific amount of DCPV storage that maximizes efficiency and minimizes costs per ton ammonia.
Wind power: Chili, Argentina, West-coast Australia, New Zealand, Morocco, Somalia, Namibia, South-Africa, Norway, Ireland, Greenland, Iceland, Japan, Taiwan
Solar power: Chili, Argentina, Peru, Namibia, South Africa, Australia, Oman, Saudi-Arabia
Some of the countries we have listed have sufficient water resources. In countries poor of (fresh) water, desalinated sea water can be used; the energy consumption for this process is only 5-6 kWh/m³.
There are many green ammonia projects being put into place. Most of these, however, are additions to existing grid-connected plants; since the grid is balanced (with grey energy sources), they do not encounter variable electricity supply. Additionally, most projects to date only partly decarbonize their hydrogen supply (+10%). These projects are good for advancing electrolyser development and solving implementation challenges, but they are only possible in industrialized locations and do not solve the main issue at hand.
Energy needs to be stored somewhere in the supply chain. Storing electricity in batteries before using it to create hydrogen is therefore logical to consider. While batteries have the advantage of being placed earlier in the supply chain, the issues with their use are simple: size, cost and materials. To buffer the electricity needed to produce 150 tons of hydrogen on-demand, a capacity of +-10GWh would be needed. The world’s largest batteries being constructed today are only 2.5 GWh, and are significantly more expensive than our DCPV’s. Additionally, the environmental impact of the raw materials needed for these batteries must not be underestimated.
There are many ways in which hydrogen can be stored. Compressed hydrogen storage tanks are the only option suitable for flexible day-to-day operation; others are too slow or costly.
Storage of gaseous hydrogen is well-documented, but generally contains several major flaws; storage density (space) and steel embrittlement and permeation. When delivering hydrogen via tube trailer for example, only 500kg of H2 can be carried in a 13m trailer. A single truckload would only last 15-30 minutes of production! If this same steel trailer would sit for a week, almost all of the hydrogen would have permeated through the steel.
These issues are solved through DCPV’s; storage is structural for optimal use of space, and the two-layered design minimizes embrittlement and permeation. DCPV’s keep the advantages of compressed gas storage; low energy loss, cheaper materials and fast loading/unloading.