2007-05-28 08:43:09 - The consequence of Peak oil means that we need new thinking as to what will drive the world's economies in the post oil era to come.

In our series of articles addressing the issue of Peak Oil we have looked at some of the implications of the end of cheap oil. Today we switch gear and publish a lengthy set of proposals for building an electric economy which provides greater energy security and sovereignty over the generation and distribution.

The article written by engineer

Anthony Holroyd is designed to spark a lively discussion. There is no one single solution in the quest for a replacement to abundant, cheap oil but an electric economy may go some way to providing a safer, healthier and more prosperous society.

In an economy where fossil fuels are in decline and renewable and nuclear energy sources are assuming increasingly dominant roles, electricity will become increasingly important as an end-use energy source. This implies that as fossil fuels deplete, the basis of our economy will shift from a predominantly chemical to a mostly electrical base.

This would appear inevitable, yet the implications are not at first easy to see. In an energy economy in which primary energy is in the form of electricity, the critical consideration becomes, how do we convert bulk electricity from a wind turbine, nuclear reactor or wave generator, into a form that we can use to fuel our cars, heat our homes and power our factories?

It has been proposed that hydrogen may form a convenient carrier for electricity used for powering vehicles. In this scenario, electricity is used to electrolyse water into hydrogen gas, which is compressed or liquefied into a storable chemical fuel. The compressed or liquid hydrogen can then be distributed to filling stations, in much the same way as ordinary petrol or diesel. The hydrogen will then power fuel cells within vehicles, which will in turn power electric motors, driving the wheels. Protonic membrane fuel cell stacks have an efficiency of up to 50% [1]. This combined with the elegance of a fuel cycle that begins and ends with water and clean renewable electricity, has led many well-meaning environmentalists and technologists (including many politicians and car companies) to advocate hydrogen as the utopian fuel of tomorrow. There is also discussion that hydrogen may offer the possibility of a democratised energy economy, allowing small individually owned renewable energy sources to produce hydrogen that can be stored locally and used to power fuel cells for home electricity, vehicle transport or even home heating. This would supposedly free individual homeowners from reliance on the centrally owned national grid.

Storable energy currency

Hydrogen is often discussed as a storable energy currency, which can be produced from a number of different sources and transported, stored and used, wherever needed. The inherent ideological attractiveness of this type of energy economy to Marxists, Anarchists and anti big-business idealists, goes some way towards explaining why hydrogen has gained so much popularity in a scientific establishment that depends critically upon Marxist controlled media organisations for positive publicity.

Supporting a hydrogen economy has become a sort of green credential for politicians and industry alike, and a company whose shares are waning can gain enormous streetcred by advocating what appears to be a progressive and green future technology. Hydrogen also appeals to car companies for the real reason that it apparently provides a seamless and easy alternative to petroleum. It can be distributed and used within vehicles in a way that would appear analogous to oil based diesel or petrol. The US government has invested hundreds of millions of dollars in the production of hydrogen fuel cell vehicles through the Freedom Car programme [2]. In California, governor Schwarzernegger has unveiled his vision of hydrogen highways, in which hydrogen gradually replaces petrol at filling stations as the bulk vehicle fuel for California, over the next 10 - 20 years [3].

H2 Woe

Unfortunately, this rosy picture of a future hydrogen economy shatters when confronted with energy analysis. In virtually every respect other than ideological convenience, hydrogen is the least attractive of all alternative fuels. Hydrogen is not an energy source, but a synthetic energy carrier, rather like the electrolyte of a battery. Energy must be invested in creating hydrogen and most sustainable energy schemes assume that the energy comes from renewable electricity. Electricity can either be drawn directly from a renewable energy source locally or drawn from the electric grid on a large scale. In order to produce usable hydrogen the energy must go through a number of steps. Firstly, the electricity must be rectified to direct current, a step that usually consumes between 2-3% of the electrical energy [4]. Hydrogen can then be produced by electrolysing water within an electrolysis cell. This process is about 70% efficient [5]. The hydrogen produced at the anode of the electrolysis cell is a diffuse gas and must be either compressed or liquefied in order to be useful as a portable fuel. Compressing the hydrogen to 10,000psi consumes the equivalent of 15% of the energy that it contains [6]. At this pressure, hydrogen will have only one-fifth the energy density of petrol and the pressurised tank required to store it is huge, heavy and costs up to £2000/kg. For these reasons, hydrogen vehicle manufacturers would prefer to use liquid hydrogen, which can be stored in insulated tanks at ambient pressures and is considerably denser than compressed hydrogen. Liquefying hydrogen will consume the equivalent of 30-40% of the energy that it contains [7]. Following liquification, hydrogen must be kept at -253centigrade, to prevent it from boiling into the atmosphere. This is accomplished by keeping hydrogen in insulated containers. Liquid hydrogen tanks for vehicles, have boil-off rates of 3-4% per day. At least 10% of the hydrogen will therefore be lost to boil-off during delivery and storage within the vehicle fuel tank. Finally, hydrogen is burned within a vehicle fuel cell, with an efficiency of 50%. The electric motors powering the wheels of the vehicle are perhaps 90% efficient [8].

When each of these efficiencies is multiplied together, it emerges that only 20% of the original electrical energy reaches the wheels of the vehicle, the other 80% is wasted in the various energy transitions. This is a degree of waste that is difficult to tolerate, especially if the original electricity is sourced from expensive renewable electricity sources. Most of the energy losses involved with the production of hydrogen are rooted in thermodynamics and are therefore essentially unsolvable. Hydrogen therefore suffers from a critical inefficiency problem that renders it unsuitable as a large-scale energy storage mechanism. These energy losses are put into perspective when one realises that 67 large nuclear reactors would be needed to produce sufficient hydrogen just to replace the energy needed to fuel the UK's car fleet. When all road transport is considered, around 100 nuclear reactors would be needed [9]. Other energy storage mechanisms, such as compressed air or a liquid nitrogen economy, suffer from similar large-scale energy losses during manufacture, distribution and end use, that renders them similarly unsuitable as energy carriers or bulk energy storage mechanisms.

Having exhausted the alternatives, it is usually wise to ask ourselves if we have subconsciously constrained our thinking somehow. In this case we have. All of the above processes turn out to be inefficient because they involve converting electricity into intermediary fuels. This is such a familiar way of doing things that most of us tend to assume that we must need some alternative fuel for powering our post-oil vehicles. We have lost sight of the fact that a much easier and more efficient option exists.

The real alternative energy revolution started more than 100 years ago and appears to have gone unnoticed by most alternative energy enthusiasts. Electricity now directly powers most railways in mainland Europe, Japan and increasing numbers of underground trains and tram-systems across the world. The Southeast of England led the world in establishing one of the first modern electric railways as long ago as the 1930s and electric street vehicles, known as trolleys, were the prime means of motorised transport in cities, before widespread introduction of private cars. Rail-based electric transport draws power directly from the grid to power electric motors, using an overhead capable or an electrified third-rail at ground level. Grid transmission in the UK is 93% efficient [10] and electric motors equipped with regenerative breaking are as much as 95% efficient.

The whole system efficiency from power plants to the wheels of the vehicle is therefore almost 90%, nearly five times better than a hydrogen vehicle, even before we begin to think about the reduced weight of an electric vehicle that does not need hydrogen storage tanks or fuel cells. Simply converting urban transport to electricity could eliminate a sizable chunk of our oil use. Bus routes could be converted into tram-routes and as oil prices continue to increase most people who can use public transport for their journeys would probably choose to do so. The problem with this option is that it tends to be constrained to specific routes and times. As usage increases, these will probably expand, but are unlikely to provide the same level of service as private cars.

Outside of busy urban areas such as large cities, public transport cannot provide the level of convenience and flexibility that people are accustomed to.

In order to achieve dramatic reductions in personal oil use, it is necessary to devise efficient methods of powering private cars using electricity. Electric cars began to receive serious attention as a transport alternative, shortly after the first oil crisis of the 1970s. All-electric vehicles such as the G-Wiz are appearing in increasing numbers within cities and hybrid-electric petrol cars are now a familiar technology across the world. Yet all of these vehicles suffer from the ultimate limitation that they require batteries to store electricity between charging. This reduces the mains to end use efficiency of electric vehicles to perhaps 50-60% [11]. Whilst this remains a lot better than hydrogen, it falls far short of the dramatic efficiency achieved by vehicles that are powered directly from grid electricity.

Electric batteries are also heavy and suffer from low power density. They wear out after 3 years of continuous charging and discharging and require replacement. The weight of electric batteries also limits the range of electric vehicles to between 40 and 100 miles between charging. The high end of this range depends upon ultra-expensive lithium polymer batteries. Most commercially available electric vehicles still rely upon lead-acid batteries, given that these are cheaper and it is easier to compensate for the low power density by reducing chassis weight, rather than buying more expensive batteries. For all of these reasons, electric cars tend to be just as expensive as ordinary petrol or diesel cars even at present high fuel prices and the short range and lack of easily available charging points makes them undesirable. Rising fuel prices will eventually tip the balance in favour of battery electric vehicles, in spite of their limitations.

Electrified Roads

Electric transport becomes overwhelmingly desirable only if it becomes possible to power vehicles directly from the grid, eliminating or reducing the need for stored energy within the vehicle. This is how all of the electric rail transport works around the world. No one would attempt to power trains or trams using batteries. These vehicles draw power directly from the grid using overhead cables or conductor rails. Could a similar technology work for road vehicles as well? This was the logical question that was asked by researchers at the University of California in the early 1980s. The US Department of Transport funded research into roadway electrification for over ten years, finally bringing the project to a close in 1993, at the end of a sustained period of low oil prices.

In principle, an electric road would work in one of two ways. The first and principally the easiest method would be to embed a steel rail, similar to the third rail used on railways, into a recess within the road surface. The rail would be electrified with direct current and an insulated sleeve would prevent the rail from earthing-out in wet weather. The vehicle would pick up power from a sliding contact or conducting wheel, making contact with the top of the live rail. The circuit would be completed by earthing through a conducting road surface, probably ordinary tarmac with aluminium fibres and graphite embedded within it. This method has the clear advantage of being very cheap, rapid and easy to engineer and put into place. It is also highly efficient, with only very slight energy losses due to arcs and earthing. One obvious disadvantage with having an electrified contact at ground level is the danger that it poses to pedestrians or animals that cross the road and inadvertently come into contact with it.

This danger could potentially be minimised by recessing the rail into a slot within the road and fencing off sections of main road. The voltage of the rail would be limited to perhaps 100 volts in order to minimise leakage and this would also make most electrocutions survivable.

The second method of roadway electrification would rely upon a set of inductance coils embedded within the road. Vehicles would carry pickup coils, a few inches above the road surface and would be powered by induced current within the coils. Power would be transferred to the vehicle by oscillating magnetic fields. This would eliminate all danger of electrocution to pedestrians or wildlife crossing the road. The California researchers found that inductive power coupling was possible for road vehicles, but power losses tended to reduce the mains-to-wheel efficiency of the process to 60% (not much better than battery vehicles). The inductance coil mounted on the car was heavy and cumbersome and the inductance roads produced an unpleasant ‘hiss' during wet weather. The inductance coils embedded within the road were also very expensive and greatly increased the cost of the system [11].

Installing an electrified road system based upon embedded live rails would allow electric vehicles to achieve essentially infinite range between recharging. A conductive transfer system would also allow electric vehicles to dramatically reduce their weight. If it were assumed that all main roads were electrified, an electric vehicle would only need sufficient battery power to carry it to the nearest main road. Once on the main road, a car would receive all of its motive power from mains electricity. Direct conductive transfer also allows very high mains-to-wheel energy efficiency, with up to 90% of the electric power produced at the power plant reaching the wheels of the vehicle. An electric road system would therefore allow us to continue using Britain's existing transportation system in more or less its present form, powering our vehicles with mains electricity instead of oil.

How much electricity would be needed? In 2006, UK transportation consumed approximately 600TWh of energy, over 90% of which was oil-based [12]. Some 80% of UK transport energy is consumed in road transport [13]. If it is assumed that the average efficiency of petrol/diesel engines used to power transport is 20%, then the actual motive work required to power road transport was 96TWh. If present transportation were powered by electric vehicles drawing power directly from the mains through a live rail embedded within the road, the efficiency of the system could be as high as 90%. However, all cars would require at least some battery power, as it is unlikely to be practical or safe to electrify minor roads. A good average figure might be 80% efficiency, for a battery/live rail powered road vehicle. This would imply that all of Britain's road transport in 2006 could have been powered by 120TWh of electricity, had an appropriate system been put in place. This is the amount of electric energy provided annually by 12 nuclear reactors, equivalent to just 30% of Britain's existing electricity production. This is a far more realistic proposition than the 100 additional nuclear reactors that would be required to power a road transport system powered by liquid hydrogen.

We can also surmise that electricity is also the most likely source of mechanical power for agriculture in the post oil era. It is easy to imagine arrangements in which fields are ploughed, sowed and harvested using equipment powered by electricity drawn directly from the mains. A tractor could be powered in this way by means of a cable drum, which unwinds and retracts cable as the vehicle traverses the field. Each field would have a power socket elevated on a pole at one corner. An electric tractor would travel by battery power to the appropriate start point and would connect its cable drum into the power socket, thereon drawing all power directly from the mains. Harvested grains would be dried using heat provided by electric heat pumps and resistance heaters and would be refrigerated using electricity. Transport to food processors and customers would take place using a combination of battery electric power on minor roads, transport on live roads and bulk transport on electrified railways.

In reality, the electricity that is used to power an electric transportation system is likely to come from a huge variety of sources. Electricity can be produced from virtually any energy source and allows ultimate flexibility in our base energy supply. The electricity powering a car via a live rail system could come from a wind turbine in the North Sea, a nuclear power plant in Suffolk, or a coal burning power plant in Kent. In the future it may come from a satellite gathering solar energy in space, or a fusion reactor or wave energy converter. During the 1973 oil crisis, a relatively minor drop in the availability of oil, wreaked havoc on entire economies and pushed the western world into a recession that lasted almost a decade.

Oil is an energy dense fossil fuel and can only be obtained efficiently from a very small number of sources. After 2020, much of the world's conventional oil will be derived from a handful of nations in the Middle East, with only minor contributions from tar sands and non-OPEC sources [8]. When oil production peaks and enters its decline phase, it will be necessary to redesign entire transport systems and even entire cities in order to adjust to a world in which transport fuels are less available. This contrasts sharply with electricity, which can be produced efficiently from a range of energy sources. A diverse electricity economy, based upon native renewable, nuclear and storable low-grade fossil fuel sources, offers the ultimate energy security advantage. If an energy source is cut off or begins to deplete, it is a relatively simple matter to construct new power plants based upon alternative energy sources and continue using the same electrically powered vehicles, cities, industries and transport systems as were being used previously. Energy efficiency, technical practicality and the need for secure energy sources, all strongly suggest that electric will become the dominant end-use energy source for the 21st century and beyond.

The Correct use for Coal and Bio-fuels

As the peak in global oil production moves closer day by day, many policy makers and technologists worldwide are turning to coal and biomass as options for the production of synthetic liquid fuels capable of powering conventional vehicles. As an endnote to this article, we will examine two scenarios:

1. The use of alternative fossil fuels for the production of synthetic diesel or petrol for road transport.
2. The use of alternative fossil fuels as electricity fuels powering electric road transport.

In both cases, the end use is mechanical work produced at the wheels of a road vehicle. But the energy pathways, by which fossil fuel derived energy reaches the wheels of the vehicle, are different.

Scenario 1: Production of Synthetic Fuels from Coal or Biomass
Coal, tar sands, kerogen and biomass can all be used to produce synthetic fuels, chemically similar to petrol and diesel.

In this scenario, fossil fuels must be mined, or for biomass, grown and harvested, and transported to a chemical plant, where they are converted into synthetic fuels through the Fischer-Tropsch process. Through this process, the base fuel is partially oxidised into a mixture of hydrogen and carbon monoxide, which are then chemically recombined to form hydrocarbons similar to those found in petrol and diesel. The condensed liquids can them be refined into synthetic fuels and burned in vehicle engines in much the same way as ordinary petrol or diesel. This process was undertaken in Germany during WW2 and continues in South Africa, where it was developed during the apartheid trade boycotts.

The mining and transporting of fossil fuels and biomass, is likely to consume up to 10% of their energy content. The Fischer-Tropsch process is 51% efficient in the conversion of base fuel into final synthetic liquid. Distributing the fuel to various outlets can be assumed to consume perhaps 5% of the total energy content of the fuel. Internal combustion engines provide an average efficiency of 20%.

The total mine-to-wheel efficiency can be calculated by multiplying these efficiencies:

Efficiency = 0.9 x 0.51 x 0.95 x 0.2 = 8.7%

Scenario 2: Production of Electricity from Coal or Biomass

At present, some three-quarters of the world's coal production, is used to produce electricity. Biomass can also be used in this way, either through pulverising the fuel and burning it in a boiler or through gasification within combined cycle gas turbine plant. Other fossil fuels such as kerogen or tar sands could presumably be used in the same way. In this scenario, coal or biomass would be mined or harvested and transported to a power plant. Here they would be pulverised and fed into the gasification chamber of a combined cycle gas turbine plant or into the boiler of a supercritical power plant. The electricity produced would then be transmitted by the grid to electrified railways and roads across the country or used to charge battery electric vehicles.

Again, we can assume that the mining and transporting of fuel to the power plant consumes 10% of the energy contained within the fuel. Combined cycle gasification power plants have thermodynamic efficiencies of up to 60% and advanced ultra critical plants can achieve 48% [14], so an average figure of 50% efficiency would appear achievable in modern coal power plants.

Transmission of electric power to end-users consumes 7.4% of all electrical energy in the UK [13]. If it were assumed that the final end use is a mains-electrified road system, such as the one discussed earlier, the end use efficiency of the electric vehicles would be approximately 80%.

The total mine-to-wheel efficiency can therefore be calculated by multiplying these efficiencies:

Efficiency = 0.9 x 0.5 x 0.93 x 0.8 = 33.5%

Conclusions

The above examples show that it would be extraordinarily wasteful and expensive to attempt to replace declining oil production with synthetic fuels derived from coal or biomass. This should also be viewed in the context that the price of all fossil fuels, including coal, is likely to increase progressively following peak oil. In so far as we continue to use fossil fuels as energy sources, in all scenarios they produce far more thermodynamic work if used as electricity fuels. This has strong implications for a future BNP energy policy.