The Ammonia Economy
There has been a lot of discussion about "the hydrogen economy" as an alternative to fossil fuels. Some people think it is an alternative energy source, while it is just a transmission medium, and not, in my opinion, a very good one.
The great advantage is that it burns cleanly to produce only water.This is outweighed by the numerous disadvantages. Energy density is low, it would take three times as much hydrogen through a pipeline as natural gas to transmit the same amount of energy. Moreover hydrogen makes normal pipeline steel brittle, and although in theory it works in internal combustion engines, the same embrittlement problem occurs. Liquefaction is horribly difficult (the lightest element of all only liquifies below -200deg C) and although it can be stored in metal hydrides, a hydride fuel tank would weigh a lot and have limited capacity. Hydrogen is highly explosive
There is however an alternative. Ammonia is easily made from nitrogen and hydrogen with an iron catalyst by the Haber-Bosch process and widely used to make fertilisers. It is easily liquefied (-33deg C, a higher temperature than natural gas) and easily and safely transported, by tanker, ship or pipeline - there are already extensive ammonia pipelines in the US to serve agriculture. It does not burn in air at atmospheric pressure, but will do so readily with air under compression, in either an internal combustion engine or a gas turbine (including jet engines). In fact it is a better fuel than petrol(gasoline) with an octane rating of 130 and delivering 10-20% more power than petrol. It burns cleanly to water and nitrogen, the latter accounting for three quarters of the atmosphere anyway. Surprisingly, it produces less nitrogen oxide emissions than petrol or diesel.
There are two disadvantages. While engine power is enhanced, fuel consumption by weight is two to three times higher. The biggest problem is that it is poisonous in moderately high concentrations. It dissipates rapidly in air, however, and has been safely used and transported on farms across the world for years, and its distinctive smell is very strong long before the concentration reaches dangerous levels. We also forget how used we have become to the dangers of petrol and natural gas: our cars are flying bombs travelling at up to 100mph, while ammonia does not burn in open air.
It is also quite cheap. Currently the bulk price for ammonia in dry liquid form is $250-300/metric ton, sharply up on two years ago as over 80% of the costs of production are from natural gas, which is used to make the hydrogen. Taking into account enhanced power from engines and lower miles per gallon, the cost in petrol equivalent terms is around $3 per US gallon, very much the same as US gasoline prices today (actual ammonia costs are two and half times lower).
Current hydrogen production uses natural gas, but there is interesting potential with solar thermal power. Such high temperatures can be generated with solar power that hydrogen can be produced thermochemically, several catalytic reactions being available to assist this (sulpur-iodine, calcium-bromine). If costs of solar thermal power generation can be halved - should be possible with scale, experience, and mass production, then the cost of generating the hydrogen becomes comprable to present day costs from natural gas cracking. The hydrogen then feeds an adjoining ammonia plant. The intermittent nature of solar power does not matter for liquid fuel production, unlike electricity production
The other point is that nearly all the costs of solar thermal are capital costs, and depreciated plants after 15-20 years would be very low cost, compared to today and still more so compared to post-peak oil. Apart from some of the hydrogen cracking catalysis (still in the lab) everything else in the process is either proven or low tech. Above all it is a feasible way to fuel existing land, sea and air engines. The great greeen panaceas of fuel cells and high performance batteries have been so long in development and with so little success that one remains dubious. It is the only way I can think of, to provide carbon-free flight.
Whaat is needed to replace oil for transport? About 15-20sq.kms of hot desert land near the sea (to get the water for hydrogen - sea water will do)for the energy equivalent of one large electric power station, which is not excessive. Southern Spain, Morocco, large parts of the Middle East; Southern California, northern Mexico; western Australia, eastern India (Thar desert); S.W. Africa, northern Chile - there is a long list.
The great advantage is that it burns cleanly to produce only water.This is outweighed by the numerous disadvantages. Energy density is low, it would take three times as much hydrogen through a pipeline as natural gas to transmit the same amount of energy. Moreover hydrogen makes normal pipeline steel brittle, and although in theory it works in internal combustion engines, the same embrittlement problem occurs. Liquefaction is horribly difficult (the lightest element of all only liquifies below -200deg C) and although it can be stored in metal hydrides, a hydride fuel tank would weigh a lot and have limited capacity. Hydrogen is highly explosive
There is however an alternative. Ammonia is easily made from nitrogen and hydrogen with an iron catalyst by the Haber-Bosch process and widely used to make fertilisers. It is easily liquefied (-33deg C, a higher temperature than natural gas) and easily and safely transported, by tanker, ship or pipeline - there are already extensive ammonia pipelines in the US to serve agriculture. It does not burn in air at atmospheric pressure, but will do so readily with air under compression, in either an internal combustion engine or a gas turbine (including jet engines). In fact it is a better fuel than petrol(gasoline) with an octane rating of 130 and delivering 10-20% more power than petrol. It burns cleanly to water and nitrogen, the latter accounting for three quarters of the atmosphere anyway. Surprisingly, it produces less nitrogen oxide emissions than petrol or diesel.
There are two disadvantages. While engine power is enhanced, fuel consumption by weight is two to three times higher. The biggest problem is that it is poisonous in moderately high concentrations. It dissipates rapidly in air, however, and has been safely used and transported on farms across the world for years, and its distinctive smell is very strong long before the concentration reaches dangerous levels. We also forget how used we have become to the dangers of petrol and natural gas: our cars are flying bombs travelling at up to 100mph, while ammonia does not burn in open air.
It is also quite cheap. Currently the bulk price for ammonia in dry liquid form is $250-300/metric ton, sharply up on two years ago as over 80% of the costs of production are from natural gas, which is used to make the hydrogen. Taking into account enhanced power from engines and lower miles per gallon, the cost in petrol equivalent terms is around $3 per US gallon, very much the same as US gasoline prices today (actual ammonia costs are two and half times lower).
Current hydrogen production uses natural gas, but there is interesting potential with solar thermal power. Such high temperatures can be generated with solar power that hydrogen can be produced thermochemically, several catalytic reactions being available to assist this (sulpur-iodine, calcium-bromine). If costs of solar thermal power generation can be halved - should be possible with scale, experience, and mass production, then the cost of generating the hydrogen becomes comprable to present day costs from natural gas cracking. The hydrogen then feeds an adjoining ammonia plant. The intermittent nature of solar power does not matter for liquid fuel production, unlike electricity production
The other point is that nearly all the costs of solar thermal are capital costs, and depreciated plants after 15-20 years would be very low cost, compared to today and still more so compared to post-peak oil. Apart from some of the hydrogen cracking catalysis (still in the lab) everything else in the process is either proven or low tech. Above all it is a feasible way to fuel existing land, sea and air engines. The great greeen panaceas of fuel cells and high performance batteries have been so long in development and with so little success that one remains dubious. It is the only way I can think of, to provide carbon-free flight.
Whaat is needed to replace oil for transport? About 15-20sq.kms of hot desert land near the sea (to get the water for hydrogen - sea water will do)for the energy equivalent of one large electric power station, which is not excessive. Southern Spain, Morocco, large parts of the Middle East; Southern California, northern Mexico; western Australia, eastern India (Thar desert); S.W. Africa, northern Chile - there is a long list.
Labels: Energy, Environment
posted by Total Issues at 11:26 pm
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