More on Ammonia

The Engineer Poet is dismissive of chemical energy transporters for renewable energy, whether hydrogen or ammonia (which after all, is a convenient way of transporting hydrogen). He has a point: direct use of electricity in, for example, fuel cells has much better efficiencies and therefore shouldbe cheaper.

Certainly generating electricity and then producing hydrogen by electrolysis is not on, in efficiency or cost terms. For thermochemical production of hydrogen using S-I or Ca-Br as a catalyst, however, from solar heat or off-peak nuclear, theoretical efficiencies are in the 40-50% range, which compares with electricity generation. These technologies have not yet been developed outside the lab. Why? –because steam cracking of natural gas to make hydrogen (the process used today) is 70-80% efficient, but that produces CO2, and would be pointless for a fuel anyway (just use the natural gas directly)

The key fact however is that there will be a continued need for chemical storage of energy . Most renewables are intermittent and/or a long way from the consumer, given long distance power transmission losses (or not even feasible – Australian solar power sold to China?) Direct distribution and storage of hydrogen is a nightmare. There seems no potential alternative for planes to a chemical fuel, and the elites of the world would rather wreck the world’s climate than give up flying. Yes, oil is a better storage medium than ammonia, but if anyone can come up with a better alternative that does not have those dratted C atoms somewhere in the molecule, please let me know.

Theoretical efficiency isn’t everything, otherwise the internal combustion engine and the steam turbine would be long gone. We have been promised fuel cells and high capacity traction batteries for decades – where are they? The world has got to change its whole energy and transportation within two decades or we are climatically wrecked - the less technological change or technical risk involved, the more likely this is to happen. This path minimises the risk, even if it less than ideally efficient.

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.

Quick thoughts on "alternative" energy costs

I have been doing some research on the issues of costs, scale,sustainability and short term feasibility. Some very quick thoughts, if anyone wants to look further there is plenty on the web. The "benchmark" electricity generation would be costs at an efficient fluidised bed coal fired power station, some where around 3-6 USc/KWh, depending on location, gas fired generally a bit higher (and up to double a year or two ago) but more flexible and suitable for peak power.

Hydro: drowns valleys but otherwise wonderful, cheap but available resources used up long ago.

Biomass: am I alone in thinking this a short term kludge? At best carbon neutral, good farmland will be in short supply in the global greenhouse, and will encourage deforestation. Utilising wastes like woodchips and straw will be more helpful, but this will not solve world energy problem except at the margin

Wind: not so much higher cost than fossil fuel when the wind blows at the right strength, and a rapid advance in turbine technology, but just so unreliable: even if the wind is too strong (over 25 metres/sec) blades have to feathered and power drops. Even in Denmark, a fairly windy place and the biggest per head investor in wind farms, special connections to Scandinavian hydro grid are in place for when the wind does not blow, and capacity utilisation is around 30%, no better than solar. Massacres birds.

Tidal power: limited sites and environmental issues (turbines in tidal estuaries rather than barrages can alleviate some of these). Needs a lot more research. Great potential for the UK, especially Severn estuary

Wave power: lots of potential, but too early to develop. Big inherent problems with storm damage

Solar photovoltaics. Horrible costs, even allowing for a normal halving on "experience curve" as technology matures, still far too high for mass power generation. Exotic cells use rare elements like gallium, those using more common materials (essentially crystalline or amorphous silicon)have an efficiency limit of 10-15% per cent.

Geothermal: limited sites in volcanic areas where underwater superheated reservoirs can be exploited, attractive costs where they are, but even then no truly renewable. Sites are "harvested" in a few decades, and prolonging life by water injection has problems e.g water disappears down fissures, or can even cause earthquakes. Not everyone can live in Iceland. The really interesting development is hot dry rocks. At certain locations (not sure how prevalent, there is test development in Australia and Germany)naturally mildly radioactive granites at up to 5km depth (the limit for commercial drilling technology) are overlain with impermeable rocks and have a temperature gradient of 40deg c/km instead of the normal 30. Inject water down under pressure to fracture the rock, and pump up again at temperatures of around 200 deg C to drive turbines. Far too experimental to be developed, so costs cannot even be estimated yet, but has the potential to be developed quite rapidly

Solar thermal: either a mass array of parabolic reflectors heating up water or another fluid, or hot air from a greenhouse array being conducted up a solar tower where it drives turbines. Works well in desert mid latitudes (20-40degrees of latitude, plenty of that around the world). Operating costs two to three times normal power costs, mainly because unit capital costs so high (plant only used at peak power for 30% of time) and power obviously intermittent. However there is interesting potential to bypass power generation entirely, with much greater efficiencies: temperatures generated are so high that it can be used to split water into hydrogen and oxygen thermochemically.

More about this in a subsequent post, and more about the obvious two medium term solutions, carbon capture at thermal power stations (sequestration) and nuclear

Climate Crisis and Solutions, an Intro

Returning to this moribund blog after more than a year. Why? Firstly climate change had gripped attention worldwide, even to the point of panic. The northern hemisphere has been extremely hot this summer, both in Europe and North America, (36C/97F is not much fun in London when nobody has residential aircon) while Eastern Asia has been even wetter than usual, with extensive flooding. The southern hemisphere winter has been unusually cold, but even this has a catch, as the southern jet stream is unusually far north and the Amazon rain forest is in the grip of a second year of drought.

The usual disclaimer that one year's weird weather is not proof of global warming is wearing a bit thin after yet another very hot year globally, and yet it is not an El Nino year. James Lovelock thinks we are past the point of no return but this lapsed Catholic still retains the conditioned belief that despair is a sin. Anyway as Dr. Pangloss' previous entries show, it is far too early to panic, the latter is only of use if it makes politicians sit up and listen. One has no hope with Bush, but even right wing evangelicals such as Pat Robertson are being converted to the reality of global warming by this summer's heat in the US, illogical and parochial perhaps but very useful. If America's hummer-loving classes start to think again, that just leaves the neo-communists who run China as an obstacle to action, and that is not insuperable. I have certainly been convinced in the past year that it is not a solar cycle, but really is human -caused for all or the most part: the sun's activity this century peaked in 1986, twenty years later it is still getting warmer and warmer!

OK, the debate should be over, but what to do about it? Technology is the key. There have to be carbon-free or carbon-neutral energy sources which are
- competive with fossil fuels on costs, no more than twice existing costs (that is within the level of market price variation of fossil fuels: they have more than doubled in the past three years)
- reliable and sustainable
- scalable enough to provide a lot of power quickly enough to make a difference, within twenty years max
- not too far out on the technological frontier

Another thing which is needed is a suitable energy transmission and storage medium to replace oil products and natural gas. There are problems with both long range electricity transmission and hydrogen, but an alternative (ammonia) looks very promising and can be used directly in internal combustion engines, in fact it is even better than petrol/gasoline.

Will explore all of the above on subsequent posts, but the promising thing is all the above should be achievable.