The current 15 Terawatts (TW) of energy that we consume on Earth includes around 12-13 TW derived from oil, gas and coal. It will take a very robust mix of various renewables to replace 13 TW; in fact, to replace around half (6 TW) of fossil fuels by 2040, we would need to replace the 6 TW as well as provide an additional 16 TW of energy from other sources to keep pace with global energy demand. So 22 TW is required in order to halve the amount of carbon emissions from today, in addition to the approximately 2.5 TW of renewables that currently exist. So the magic number of total renewables would need to equal 24.5 TW.
If we look at all of the existing and potential renewable production, we can come up with an estimate of the amount of renewable energy product we could have by 2040. Please keep in mind that current production is estimated, and hopefully conservatively, so that actual production should be at or slightly above these estimates:
1. Hydroelectric: Assuming current capacity of 1 TW (it’s actually a little less), it could be possible to see 2 TW by 2040 with hydroelectric dams; that is an optimistic forecast, as many of the best dam locations in developed nations are in use. However, there are other forms of hydroelectricity, including micro-hydro, tidal power and osmotic power, and while generally unknown today, they should see some growth over the next few decades. For the purposes of increasing the total hydroelectric energy, however, these other technologies may not provide too much of an increase by 2040. It would be best to assume that these additional methods only serve to increase the probability of total hydro production reaching 2 TW.
2. Geothermal: power from within the Earth currently provides around 10 GW of electricity and 28 GW of heating, which equals 0.038 TW in total. Geothermal has much potential in many areas of the world, including British Columbia, where it’s possible for geothermal electricity to be generated. Even areas that may not have efficient electricity production can use geothermal for direct heating. In theory, almost all space heating and cooling on Earth (around 1.5 TW) could be provided by geothermal and passive solar, but it is unlikely that every home on the planet will be equipped with a geothermal heat pump and optimized for solar heating by 2040. It is more realistic to assume strong growth in geothermal to a level where we could see a total of 1 TW, including electricity.
3. Biomass: Ignoring the fact that not all Biomass energy production is sustainable, the current production of approximately 250 GW could increase due mainly to biofuels derived from agricultural waste products or algae (as opposed to ethanol from corn and other food crops, which is more of a fad than a solution). I can optimistically imagine an increase to 1.5 TW by 2040, as there is abundant potential in mature economies for biofuel production.
4. Wind: We currently have over 120 GW of wind worldwide, and we are seeing major growth of wind capacity in various countries, including Canada. However, wind has a very large divide between peak capacity (high winds) and actual capacity, as sometimes the wind isn’t providing enough force to create a measurable amount of energy. The “uptime” of wind can be estimated at 40% by wind optimists and at 1% by its critics. In my opinion, wind is an excellent companion to solar, but still requires an additional backup for the rare times when there is no wind or sun. However, improvements in battery technology (including plug-in hybrid cars) could help to make the 40% capacity a more reliable figure; in addition, efficiency will probably be improved somewhat by innovation. So our current 50 GW of actual capacity (0.05 TW) could possibly expand to as high as a full TW by 2040.
5. Solar: Along with geothermal and wind, solar has far larger potential than is currently being employed. It is estimated that 120,000 TW of solar energy is available for use, and while it’s impractical to capture all solar energy that visits the planet, a miniscule percentage could be harnessed to meet all of our current needs, as long as reliable methods of storing the energy can be employed (battery technologies). Solar energy, including solar space heating and solar water heating, amounts to around 120 GW (0.12 TW). The capital costs of solar are declining due to mass production and innovation, and I expect that solar installations will increase over the coming years, and will be given a boost by the coming commercial availability of plug-in hybrid automobiles. Plug-in hybrids function not only as automobiles; they are also mobile batteries for storing excess energy. It will be possible to charge a battery using renewables such as solar or wind when there is abundant energy being produced, and the battery could then be connected to a home electrical grid to provide power. It is possible in my opinion that solar could increase to 5 TW of actual capacity (versus peak capacity), which is the figure that is most important when looking to replace baseload fossil fuel generation.
If we combine these totals, we see that my total projection for worldwide renewable energy production to equal 10.5 TW by 2040. On its own, this would be a good start to replacing fossil fuel production at 2009 levels, but it cannot also accommodate the projected growth in worldwide energy usage.
Many environmentalists hope that better efficiency in energy generation and consumption will cut back the growth in energy usage, but I believe that it is not realistic to expect growth to be curtailed by more than several terawatts. It’s not impossible that cap and trade programs or carbon/consumption taxes in G20 countries can allow efficiency gains to result in a decrease in energy usage (defying Jevons Paradox), but we cannot and should not expect less developed nations to stop any economic growth that outpaces gains in the efficiency of their current energy resources. In truth, we can’t really expect that G20 nations would be able to slow economic growth to such levels even if there was consensus to do so.
Assuming that the global population will be at or around 9 billion by 2040, freezing power consumption to current levels would require every person on Earth to cut their energy usage by a quarter in order to accommodate the newcomers. Of course, this is more likely than the idea of freezing the global population at 6.8 billion, but is still very difficult to imagine. Realistically, I can imagine the 14 TW shortfall being reduced through conservation and purposeful consumption restrictions to 10 TW; a ten terawatt shortfall is about as optimistic as I can be.
If we can cover this shortfall of 10 TW, we’ll see the maximum carbon dioxide threshold reach between 450 and 500 ppm by 2040, at which point we will need to immediately begin removing greenhouse gases from the atmosphere to minimize the damage as much as possible. A threshold of 350 ppm is currently recommended by many activists and scientists as our ultimate goal. Barring any unexpected and amazing technological breakthrough in energy production, I don’t think it’s possible to avoid reaching 450-500 ppm (note: carbon dioxide isn’t the only greenhouse gas, so 450 ppm CO2 can mean different things based on other gases as well as some cooling effects such as aerosols).
The damage done by the carbon emissions that have already occurred can only be reversed quickly through energy-intensive geoengineering. Geoengineering involves various engineering technologies to mitigate or reverse climate change or remove emitted greenhouse gases, and is an important second step after alternatives to fossil fuels have been developed and deployed. The ideal geoengineering methods are any that remove greenhouse gases from the atmosphere; methods to reduce the amount of sunlight (and heat) reaching the Earth will not solve other greenhouse gas emissions problems, such as ocean acidification. However, devices such as artificial carbon-removing trees and scrubbing towers may take too long to reverse temperatures on their own, so concepts such as cloud-seeding and even deflecting sunlight could help to accelerate a decrease in warming.
It’s very important to note that the energy- and capital-intensive nature of geoengineering makes the notion of using it without reducing fossil fuel usage unrealistic; the additional fossil fuels required to power geoengineering would in all likelihood add more emissions than the geoengineering would be able to remove or mitigate, making the whole strategy pointless. While it’s expected that fusion power will be available in the second half of the 21st century (the running joke is that it’s fifty years away today, and that it will still be fifty years away fifty years from now), there are no absolute guarantees that this technology will ever be ready for commercial use, and continued growth of greenhouse gas emissions may result in catastrophic changes in climate before fusion-powered geoengineering can come online.
To make up the shortfall in energy production involved in halving fossil fuel usage by 2040, there are four options available (that I know of):
1. Heavier investment in renewables: a worldwide campaign to equip all buildings on Earth with solar panels and geothermal heat pumps, and to place wind farms and next-generation hydro next to every city is possible, but it’s difficult to see how a strategy can be agreed upon when there isn’t even consensus on the sheer impossibility of conservation and our current renewable energy growth rates removing the need for fossil fuels anytime soon. Until such time as we can expect to see our world leaders telling us that we could be 10 TW short of survival, I don’t expect an even larger growth in renewables than I’m predicting above.
2. Continued use of fossil fuels using on-site sequestration of emissions: sequestration is a movement that is gaining momentum in the two largest coal-burning nations, the United States and China. However, even if “clean coal” can replace the thousands of coal plants in these two countries, it does not solve other environmental issues with marginal oil extraction (including tar sands) and coal mining; in addition, sequestration will reduce the efficiency of existing fossil fuel power plants and has a negative effect on air quality; lastly, we will still eventually run out of fossil fuels. China has already started to work at replacing its most inefficient coal plants with gas-fired plants and cleaner coal plants; the first coal plant in China to sequester its emissions is planned for operation in 2011.
3. Space-based solar power: if launch costs to Low Earth Orbit (LEO) could be reduced to $2,500/kg (and that looks to be possible by 2025) and the increased cost of fossil fuel energy (due to consumption taxes and not just demand) can rise to a high enough level, it would be possible to assemble solar arrays in Low Earth Orbit. The assembled satellites would either be left in LEO (smaller antennas) or thrust outwards to Geostationary Orbit (less redundancy required) to transmit power to terrestrial receiving stations using microwaves. While there are no amazing new technologies required (aside from the advanced composites used in the next generation of launch vehicles, which are already being developed), the economics and risks of this venture make it a challenge to achieve within a 30-year timeframe. Ten Terawatts of solar power would weigh approximately 10 million tons, which would require 150 yet-to-be-developed 150-tonnes-to-LEO heavy-lift launch vehicles launching approximately 475 times each (twice a month for twenty years). In addition, there would either need to be additional propulsion to bring the solar array to geostationary orbit, or more satellites for 100% uptime in LEO, as well as the large receivers on Earth that may need to be as large as 5km in diameter.
4. Nuclear Fission: Fusion may be commercially available by 2040 if we’re lucky, but fission is here today. There are environmental costs to uranium mining, and there are definite concerns about safety and nuclear proliferation, but I don’t believe these outweigh the benefit of revisiting nuclear power. The biggest threat to good ideas is fundamentalism on either side, and the “no nukes ever” argument could affect more than global energy production: nuclear power is an essential part of space exploration and exploitation. Ironically, nuclear fission may be the key to accessing extra-terrestrial sources of fusion fuel and space-based solar power that will eventually make our current nuclear power plants obsolete. In the short term, newer designs involving passive safety, along with the addition of light water reactor sustainability for existing plants could result in an increase in nuclear power both through construction and the life extension of existing plants. Because it takes around ten years for a new nuclear power plant to go from planning to operation, it would take serious devotion and effort to expand the current global nuclear capacity of under a terawatt to three or four TW. To reach 10TW with nuclear alone, we’d need around 10,000 new nuclear reactors, which is 500 per year over twenty years.
So which of these options is the best choice for humanity? I believe the answer is all of them. To find that missing 10 TW of energy, we will need more than just one strategy; if one of these options succeeds, it will get us closer to our goal, but won’t be enough to get us all of the way in a reasonable timeframe. If two out of four, or perhaps three out of four succeed, we will finally see emissions drop to a manageable level; only then can we start looking at step two, reducing the greenhouse gases that have already been released.
I am all in favour of reduce, reuse, recycle, and the idea of planting trees and investing in cleaner fuels; a strong spirit of conservation can save us terawatts of energy. But emotional environmentalism isn’t enough on its own to conquer our current energy crisis; we need to start looking at our energy crisis in absolute terms, including both the required energy and the costs of construction and operation. This involves not being sucked into the arguments of the zero-growthers or people who obsess over a climate change conspiracy, which will result in more arguing and no progress. No matter your view on just how much warming there is, or how much of it is due to human activity, we are still left on a planet with finite fossil fuels and a population that will continue to expand in numbers and in energy consumption. A revolution in energy is required for the future progress for humanity, and we’re running out of time.