Energy: How to have a Future Worth Having

By David Archibald

29 September 2023

 

The peak month of world oil production was back in October 2018. Production has declined slightly from then. The first signs that the oil production decline is accelerating are now apparent, with the oil price rising a third from its midyear low. With peak oil now in the rear vision mirror, the decades of declining production are now upon us.

This won’t mean that solar power and wind power become more competitive. Solar and wind facilities are manufactured and installed using energy from coal and oil. In a tight energy market in which different sources of energy are semi-substitutable for each other, the coal price and the natural gas price will rise to the oil price in energy-equivalent terms.

The significance of that for solar power is that it is currently made using power from coal-fired power stations at about $0.05/kWh. Under ideal conditions in the Australian desert, solar panels produce power equivalent to the cost of power from diesel at $0.20/kWh. If you used power from solar panels to produce more solar panels, the cost of the power they produced would be about $1.00/kWh.  Furthermore, solar panels aren’t recycled — they are once-through to landfill. They are not a renewable energy source in any sense. Solar panels are artifacts of a millenarian/apocalyptic/pagan cult in which the adherents signal their virtue by the display of their panels.

The economics of wind farms are slightly better than solar panels, but still well short of what is needed to sustain civilisation. Wind turbines are built to a price, to satisfy availability requirements over a contract. The fact that some of the turbine towers end up bent means that they are designed with only a little margin above failure. The current fad of installing them out at sea, because voters don’t want them anywhere near, simply means higher capital and operating costs and much more expensive electricity.

It is also not a choice between wind and solar on one side and coal on the other. As the oil price rises through US$110 per barrel, coal liquefaction plants become viable to supply the liquid transport fuels we need. At the moment, coal consumption and oil consumption are close to the same level in energy content terms. To fully replace oil production with coal liquefaction as it declines will require a doubling of the coal consumption rate. It follows that the life of our remaining coal reserves will halve.

So deciding between renewables and coal for power generation is a false choice. Because coal isn’t a long-term option. There are babies being born now who will see the end of coal. There is not much point agonising about coal-fired power stations. The better use for coal is producing liquid fuels for transport applications. There is only one source of energy that can replace coal for power generation and that is nuclear. The sooner we replace coal with nuclear for power generation, the longer our coal reserves will last and the higher the standard of living our children will have.

 

Figure 1: Figure 30 from King Hubbert’s 1956 paper Nuclear Energy and the Fossil Fuels showing our civilisational switch from fossil fuels to nuclear. In effect, fossil fuels got civilisation started and U²³⁵ is the match that allowed humanity to light the nuclear fire that will maintain civilisation at a high level until Judgement Day.

 

The cost of making renewable power sources, wind and solar, will go up in tandem with the coal price because they are made with energy from coal. The solar panels and wind turbines we are installing at the moment will be carted off to landfill at the end of their lives and replaced by nuclear power. This is because the cost of nuclear power should remain at about the price it is currently, while the prices of all other forms of energy will go up with the oil price. And there will be no point in using power from nuclear reactors to provide the energy to make solar panels and wind turbines, because the price of the power produced will be at least five times that produced by the nuclear reactors in the first place.

That said, there are three major problems with nuclear power as we currently practice it. Firstly, at a steady power output, seven percent of the energy from a nuclear reactor comes from delayed fission reactions. That will decline within a day to about one percent but it can take months to decline to a level at which the reactor doesn’t need external power for cooling.

To put that into context, the dominant nuclear technology used around the world at the moment is the U²³⁵-burning light water reactor. Back in the 1970s the average size of a nuclear reactor was 300 MW of power generation. What might cause the reactor to fail would be an accident which stopped the coolant water from circulating. Then it would be a race to restart the coolant circulation before the system was overwhelmed by the heat from the delayed fission reactions. If that race is lost, the cooling water boils off and the reactor core heats and starts melting. The mass of molten steel and fuel rods becomes a substance called corium, which can melt through the floor of the reactor chamber. The French nuclear plant builder Areva has, in its current designs, a subfloor below the reactor chamber to catch the corium.

The fuel rods consist of fuel pellets in a zirconium tube. At 1,250°C the zirconium reacts with water to produce hydrogen. The hydrogen accumulates in the top of the reactor chamber until it eventually explodes. All three of the operating reactors at Fukushima in 2011 had a hydrogen explosion.

To mitigate the risk that ultimately comes from the portion of energy produced by delayed fission, reactor designers responded by adding more concrete and steel to contain the potential release of radioactive material from a reactor excursion. This increased the capital cost per MW produced. This in turn prompted a trend to make the reactors much larger, up to the 1,600 MW level, in order to gain economies of scale. And because the volume of a container goes up faster than its surface area, this meant that the bigger reactors are more difficult to cool and thus are inherently more dangerous than the 300 MW ones they replaced.

So to make reactors safer again there is now a trend to what are called small modular reactors, with power outputs in the range of 100 to 300 MW. They will be safer because it will be easier for the reactor core to shed heat. But if too small, the capital cost per MW rises.  There is also the problem of staffing. A fleet of small modular reactors might require three times as many staff as one made up of normally sized reactors.

Delayed fission is the biggest problem with nuclear power and it is a problem that almost nobody is aware of.

The second problem with nuclear power is the production of high level waste. A 1,000 MW reactor will produce three tonnes of high level waste per annum, basically the used fuel rods. A reactor’s fuel rods are changed out every three years or so. By the time the rods are pulled about half the energy produced is from plutonium created from irradiated U²³⁸. The rods are pulled because of radiation damage to the zirconium cladding which could cause the rods to warp and not be able to be extracted. Current practice is to not process the spent fuel rods but to put them in long term storage where they will be a radiological hazard for millions of years, literally. The cost of reproccessing spent fuel rods equates to a uranium price of about US$250/lb while the current spot price is US$44/lb. Our civilisation is kicking the can down the road on reprocessing, requiring a future generation to bear part of the cost of generating power now. This is an unsatisfactory state of affairs.

The third problem with light water reactors is that they are extremely wasteful with the planet’s uranium endowment. Uranium as it comes out of the ground is 99.3% U²³⁸ and 0.7% U²³⁵. To be used in light water reactors, the U²³⁵ is enriched five-fold to 3.5% and 80% of the U²³⁸ is thrown out. Well, some of that U²³⁸ is used to make depleted uranium antitank projectiles, which in battle ends up as uranium oxide spread to the winds. Depleted uranium antitank rounds contain four kilograms of U²³⁸, which would have produced the energy equivalent of 19,000 barrels of oil if processed through a plutonium breeder reactor. And to put that number into context, a car being driven 20,000 km per annum at a fuel consumption rate of 10 km to the litre will burn 34 barrels. So the energy inherent in a depleted uranium antitank round is equivalent to powering a car for 558 years.

Problems two and three can be solved, and need to be solved, by fully developing the plutonium breeder technology. Plutonium breeder reactors operate by irradiating U²³⁸ with high energy (fast) neutrons to produce Pu²³⁹. There have been plutonium breeder reactors that operated happily for decades, all in Russia. France also successfully operated a plutonium breeder reactor, at least until it was shut down as part of a political deal with the French green party.  The best existing Western design for a plutonium breeder reactor is considered to be the GE-Hitachi PRISM reactor. This is set up to reprocesses the fuel onsite using a pyrometallurgical process in a closed fuel cycle.

 

 

Figure 2: GE-Hitachi PRISM reactor cross-section

 

The first problem is also solved because plutonium breeder reactors operate at atmospheric pressure with no water used in the reactor core ready to react with the fuel rods. They are inherently much safer than U²³⁵-burning light water reactors which only use one percent of our uranium endowment. Plutonium breeder reactors will utilise all 100 percent of our uranium endowment and thus will give us 100 times the energy of the technology we are currently using.

Plutonium breeder reactors can produce 30 percent more fuel than they consume. They operate in the fast neutron spectrum and thus need to use sodium as the coolant.

Reactors breeding thorium to U²³³ have an eight percent breeding margin and operate in the thermal (low energy) neutron spectrum. Eight percent is not much margin to play with, the necessary technology is still at the conceptual stage and our civilisation is running out of time. On the other hand there is four times as much thorium as uranium in the Earth’s surface. So if the excess neutrons from plutonium breeding could be applied to getting thorium breeding over the line, this would, in effect, increase the life of our uranium endowment four-fold.

If our civilisation is going to have a future worth having, it will be powered by plutonium breeder reactors. The only alternative to nuclear power is to revert to wood and horses which will result in an 18^th century standard of living. It will be easier to get that nuclear future while we still have some oil and coal to burn. It will be hard to build nuclear reactors if we are using energy from horses. So, the sooner we start down the right path, the safer and happier we will be.

Right now, coal and oil and natural gas make all the things we need, either by providing the energy to make them or the materials they are made from. When the fossil fuels run out, how will power from nuclear reactors be transformed into the physical things we use? The five pillars of civilisation are diesel, cement, steel, plastics and ammonia.

The production of diesel (and petrol and aviation fuels) will use the Bergius process to hydrogenate biomass. The process will start with power from nuclear reactors applied to the electrolysis of water to produce hydrogen. Power at $0.05 per kWh produces hydrogen at $7.00 per kg. In energy content terms, this translates to a diesel price of $2.59 per litre, which is only a little more than what Australians are currently paying at the pump.

The following diagram is from Friedrich Bergius’ speech at his Nobel Prize acceptance in 1931:

 

Figure 3: Mass balance for the Bergius Processs

 

What this figure shows is that the addition of only another 5% by weight of hydrogen converts a near-useless solid fuel into a liquid with a high energy density and ideal handling properties. Only a little smaller than the diesel molecule is heptane, C₇H₁₆, which is the ideal base for a thermobaric bomb.

Coal comes in from the top left and is combined with hydrogen and recycled oil to make it a liquid. The hydrogen is produced by steam reforming of the light ends of the process. If the power from nuclear reactors or even wind turbines was cheap enough then that, via electrolysis, could be the source of the hydrogen with a saving in capital costs and operating complexity.

The conversion takes place at 400°C and 200 bars of pressure. The hydrogen content of diesel is 14% by weight. The hydrogen content of coal can range up to 8%, the level of Latrobe Valley brown coal. From that level it only takes another 6% hydrogen to make diesel. The last experiment in converting coal to diesel in Australia was conducted by the Japanese Government in the Latrobe Valley in 1991. As as result of that research it was calculated that the oil price necessary for commercialisation was then US$40 per barrel; equivalent to US$110 today. Australians are currently paying A$349 per barrel for diesel at the pump, equating to US$230 per barrel. So we are already paying a high enough price to start the coal liquefaction industry.

With the appropriate tax structure, making our own diesel from our own coal is commercial now and would make Australia much safer. And the coal we would use for that would be too low grade to be transported.

When the coal runs out, the feedstock will switch to wood.

While there is currently a lot of enthusiasm for the concept of using hydrogen directly as a transport fuel, the physics and chemistry of hydrogen preclude its adoption to that end. It combines a low energy density, transmission losses and leakage with a wide explosive range. To understand the limitations of hydrogen there is nothing better than the experience of playing with it as a child:

After my experience playing with hydrogen as a kid, I have zero doubt that parking 40-50Kg of compressed hydrogen next to anything you care about, or inside anything you care about, would be the definition of insanity.

That said, hydrogen will be a big part of our energy future. Just a little bit of hydrogen added to a near useless, low-value carbon source turns it into a precious liquid fuel with a high energy density and optimum handling characteristics. The future will be short of carbon because its availability will depend upon how fast biomass can be grown.

Diesel is a hydrogen fuel with over one third of its contained energy coming from the 23 hydrogen atoms in each diesel molecule:

 

Figure 4: Diesel by composition and energy contribution

 

The relative market share of diesel and electric vehicles in the passenger car market will depend upon the cost of growing biomass for the former and cost of power from nuclear reactors for the electric option. Some sectors of the economy, including agriculture, aviation and marine, can’t be electrified. The price they will pay to be supplied will be the first call on the output of the Bergius plants.

It is likely that at some point in the future recycling of all metals will be required, instead of sending them to landfill. Then electric vehicle operators will be paying for their batteries twice — in the making of them, and secondly for dissolving them in acid to recover the metals at the end of their 10 year life. Electric vehicles are expensive now but the owners are yet to pay for the full cost of ownership. Recycling of all metals will certainly be the end of solar panels.

Under optimum growing conditions in Brazil, eucalypt plantations produce 40 cubic metres per hectare per annum, which becomes 20 tonnes of dried wood. This in turn converts to 10 tonnes of lignin, which would yield 10,000 litres of liquid fuel. Assuming in Australian conditions that the yield per hectare is 25 cubic metres per hectare, one hectare would produce 39 barrels per annum of diesel per annum. To supply Australia’s requirement of one million barrels per day would require close to 10 million hectares of plantation forests — about 8% of Australia’s forested area — so it is quite achievable.

The second pillar of civilisation is cement. It is made using 200 kg of coal to produce one tonne of cement. In the post-coal world, energy for cement-making will come from charcoal produced from plantation eucalypts. The yield from wood to charcoal is 35% so Australian annual consumption of nine million tonnes of cement will be made using charcoal from 5.4 million tonnes of wood produced from 200,000 hectares of plantation eucalypts.

To make steel after metallurgical coal runs out, we will likely use electric arc furnaces to provide the power for the reduction of iron ore in a liquid iron bath. As long as there is free carbon in liquid iron, it will reduce carbon dioxide to carbon monoxide which in turn reduces the iron oxides. The heat necessary to drive these reactions will come from the electric arc. In essence this is similar to how aluminium is smelted now.

Plastics, the fourth pillar, are mostly a combination of carbon and hydrogen. Industrial chemists can make every type of plastic using carbon monoxide and hydrogen as the initial starting materials. It will just be more expensive than if you started with a larger molecule first, such as naptha from oil refining.

Ammonia is the fifth pillar of civilisation. Half of the world’s population is alive due to protein that had its source in the energy contained in coal and natural gas. That energy is used to combine nitrogen from the atmosphere with hydrogen from steam reforming of natural gas to produce ammonia. Which in turn is used to make urea and ammonium nitrate fertilisers. The whole process is easily converted to be powered by nuclear reactors. It is the cost of nuclear power in the post-fossil fuel era which will determine to cost of food.

 

David Archibald is the author of The Anticancer Garden in Australia