Some miscellaneous thoughts about CO2 harvesting and other hydrogen energy transporting issues follow.
The arctic and antarctic may be good places to harvest CO2 directly from the atmosphere. Lots of wind in places there, and (seasonally) temperatures almost low enough to condense CO2 directly from the atmosphere. CO2 solidifies at -72.5 deg. C., or -98.5 deg. F. CO2 in this solid dry ice form could be stored in cold storage for use in warmer months. For -56.6 at 5.2 atm. The atmosphere is only 0.05 percent CO2 by weight, 0.03 percent by volume This means about 3300 m^3 has to be passed through a CO2 condenser to obtain a single m^3 of CO2. If the CO2 is to be gassified for pipeline transport then all the cooling/heating can be accomplished mostly by heat exchange, but the process is still expensive due to the volumes involved. An alternative, especially in warm weather, might be to use CO2 solvents or adsorbers (e.g. triethylene glycol, propylene carbonate, Diglycolamine, monoethylamine or diethanolamine) to scrub the CO2 out of the air. Again a large air flow must be sustained, and energy is required to release the CO2 once dissolved or adsorbed. Another approach might be to mine the ocean or ocean floor for carbonaceous material. This would be bad in the sense that the CO2 is already sequestered, but balance could be obtained by fertilizing the ocean with iron in the mined areas in order to increase the rate of carbon sequestration. Recently sequestered carbon obtained by farming is really a renewable resource. Growing carbon rich crops is an angle, but it depletes the soil and requires ammonia based furtilizers, which are also hydrogen products, but products that energy from windmills could readily help produce. There is plenty of nitrogen to be had from the atmosphere, which can be combined with hydrogen to make ammonia. This then points out a possible alternative method of shipping hydrogen. Ammonia (NH3) can be produced at a windfarm and transported by tanker ship to a destination where a nitrogen stripping plant is used to produce the hydrogen. This would get the hydrogen to distant world markets, and would aid in the production of furtilizers there. Once the nitrogen is stripped and returned to the atmosphere, the hydrogen can be piped or used directly for energy production. There is a much higher danger associated with ammonia vs methanol, due to its toxicity, but this can probably safely be managed for tanker ships unloading at the end of long unloading piers. The problem remaining then is the energy cost of nitrogen stripping from the ammonia when hydrogen is needed. Perhaps ammonia can be used to make a useful liquid fuel, like hydrazine, though that would not be a safe choice. Regards, Horace Heffner
