The world is so fixated on fossil fuels today, that success in the post-fossil-fuel world will probably involve turning the whole energy economy on its head, from fossil fuel combustion being centre stage to an orientation on electricity production.
- primary energy sources were 90% combustion (33% petroleum, 27% coal, 21% natural gas, 9% other combustion incl. fossil peat, firewood, and waste biomass). The non-combustion balance was 6% nuclear, 3% hydro and 1% other.
- 20% of the primary energy supply was used for transportation, almost all of that being from petroleum. 33% of the primary energy supply was consumed to make electricity available as a secondary energy form, with the electrical output being equal to about 13% of the primary energy supply.
- electricity demand variation was met mostly by peaking fossil thermal (and to a lesser extent hydro) generating plants. Peaking nuclear plants and electrical energy storage played only minor roles.
Where do we go from here? Here are some additional facts to consider:
- For the needs of the transportation sector, there is no good replacement for liquid hydrocarbon fuels, and probably never will be. Because of basic limitations imposed by physics and chemisty, neither electric batteries nor hydrogen can equal liquid fuels as an energy storage medium in this portion of the economy. Hydrogen as a fuel will probably never make it into the mainstream at all. Electricity can be used where you don’t need to store it (as in subways, streetcars, and commuter rail) or where you only need to store a modest amount of power (as in short-range electric commuter vehicles).
- The world cannot grow enough biofuels to meet its demand for liquid fuel, not even for the portion used by the transportation sector. All known fuel crops except algae have yields far too low to do the job. Tremendous successes with algae are unlikely given the daunting challenges: the demand for water the algal fuel industry would involve, and the problem of interspecies algal contamination killing yields. Most of all, the biofuel industry involves the removal of arable land from food production when the world’s population is already underfed but still rising.
- Remaining for consideration as currently known non-fossil primary energy sources are: nuclear, hydro, wind, solar, and geothermal. Some of these have more than one specific form. There are many different kinds of nuclear fission reactors, and maybe fusion will someday provide a positive energy balance too. Wind turbines come in different styles as well. Hydro dams on rivers are conceptually different from tidal or ocean-current hydro stations. Solar photovoltaic technology is different from solar thermal. “Geothermal” systems may either tap solar energy (if the evaporator coils are buried in shallow trenches) or residual heat of the earth (if the evaporator coils are buried in deep shafts).
It is unlikely that in the post-fossil-fuel future, any one of these energy resources will become the sole primary energy source. It is wiser to maintain a degree of technology diversity. More than likely, we will use all of them in a proportion that reflects their relative cost and suitability for a given purpose given the state of the technology at the time. One aspect of the situation that seems problematic at first is that none of these technologies can do the duty of handling the peak loads on the world’s electricity grids. Only hydro is suitable, but the global supply of this resource is inadequate for the task.
The solution would seem to be to build out electrical generating capacity in all these forms, and find a different way of dealing with peak loads. Here’s a key idea: Given that the need for liquid fuels will persist even after the fossil fuels are gone, particularly for the transportation sector, it follows that these liquid fuels will need to be manufactured synfuels. In turn, that fuel production will require massive amounts of electricity. The solution is not electricity storage, nor is it to make the electricity generating plants track peak demand. Instead, the idea should be to make the synfuel production plants’ electricity consumption track against peak demand. Thus during moments of peak demand or moments of low supply from resources such as wind and solar, the synfuel plants would reduce their consumption of electricity and output of fuel, giving up the electricity to other users. The synfuel plants would soak up all the extra electricity when more is available than needed by other users.
Here is a possible post-fossil-fuel scenario:
- primary sources will be 90% electricity from principally nuclear, but also hydro, wind, solar PV, & solar thermal turbine sources. The 10% non-electricity balance will include biomass & biofuel combustion, and geothermal resources
- requirements for heat will be met by solar, geothermal, and electric heat, and only rarely by combustion
- over 50% of the primary energy (electricity) will be consumed to make available about 20% of the primary energy as synfuels.
- electricity demand variation will be met by increasing and decreasing the instantaneous synfuel production, not by peaking nuclear, wind, or photovoltaic plants. The world can store months’ and even years’ worth of liquid fuel, and synfuel plants will be designed to rapidly absorb any changes in electricity availability, so adjustments in electricity production can be made at a slow pace (which suits nukes just fine).
- energy prices will be higher in real terms than today, prompting greater efforts at conservation. Per capita energy use will probably decline in wealthy countries relative to 2009 consumption, but it will probably increase in most countries that were poor in 2009, due to rising prosperity. Absolute energy consumption will decline in the wealthy countries due to better efficiencies and declining populations, but will increase in the formerly poor countries because of rising prosperity and rising populations.
In many ways this future represents a reversal from current practice, from combustion-first to electricity-first, but it should be managable. What the future mix of primary electric generating capacity might be will depend on the relative merits of the relevant technologies. We shall therefore examine nuclear reactors and the supply of uranium, also solar technologies, geothermal, and wind.