Maybe my perceptions are incorrect on this point, but my sense is that a lot of people believe that the US economy is making strong progress toward clean non-carbon energy, driven by increases in solar and wind power. I don’t see it that way. My own reading of the evidence is that the solar/wind presence in the US energy sector is barely getting underway, with some high hurdles to come.
For an overview, here’s a figure showing the US energy sector from the the US Energy Information Administration website. The left-hand categories show the primary sources of energy. Electricity is not a “primary” source, because it needs to be generated from the primary sources, but instead is a method for transmitting energy. Thus, the electricity sector in shown in the bottom center. The main sectors of energy use are on the right.
Some thoughts from this figure:
1) In 2025, after several decades of discussion of risks of climate change and the need to reduce carbon emissions, fossil fuels are 81% of US primary energy. Petroleum is by far the largest primary source for transportation. Natural gas is the single largest primary source for industrial, residential, and commercial use, as well as for generating electricity.
2) In the “renewables” sources of energy, which is 9% of the total, only about one-third of that is solar and wind–call it 3% of total US energy production. About 60% of renewables are “biomass,” including wood and the corn that goes into ethanol, with the rest being mostly hydroelectric (that is, dams).
3) Nuclear power as a primary energy source is about equal to the entire renewables sector, which means that it is about three times the size of solar and wind combined.
4) Within the electricity sector, 59% of the energy that goes into the sector is lost within the system itself, including “line losses” as electricity is transmitted and other factors involved in balancing the electricity grid. The figure shows that total energy flowing into the electricity sector is 33.5 quadrillion BTUs, while the amount flowing out is 13.8 quadrillion BTUs. Thus, about 35% of all primary energy flows into the electricity sector, but electricity accounts for only 18% of actual end-sector energy use. If the goal is to increase production of electricity to replace fossil fuels–say, electric cars to replace gasoline-fueled cars, or electric heating and cooling to replace natural gas–it will be necessary to generate more than twice as much electricity to replace the energy content of the fossil fuel source, to make up for electricity lost within the system. This holds true for increased production of nuclear energy and hydroelectric power as well, which feed into the electrical grid.
I’m not making an argument here about whether greater electrification of the US energy sector is good or bad, or the health costs of conventional polllution from burning fossil fuels, or the risks of climate change. This is an argument about numeracy.
If the US economy was to run primarily (say, more than half) on electricity from solar and wind, these energy sources need to rise by an enormous multiple. Solar/wind are currently 3% of US primary energy, so multiplying them twenty-fold would be 60% of current US primary energy. But remember that the electricity system for transmitting energy has losses in its operation, so to replace energy from fossil fuel use, we would need to (say) double solar/wind energy output again. It’s also necessary to “overbuild” capacity for solar/wind, so that when it’s dark and/or the wind isn’t blowing, energy can be stored for later use; for example, in the battery of an electric vehicle. We also seem to be entering a period when demand for electricity is rising due to developments in information technology, which means electricity production from solar/wind would need to rise still farther.
It seems foolhardy to put an ultimate number on how much solar/wind would need to expand if they are to become the predominant energy source for the US economy. But expanding by a multiple of 20 would be the extreme low end–which is what I have in mind when I say that if the vision for the future of US energy is to be predominantly solar/wind, the current levels of these energy sources are barely a beginning.
Of course, generating the additional electricity is only the first step. Remember that electricity is only about 18% of final energy use, so substantially greater electrification of the economy will requires a dramatic increase in the size and scope of the electrical grid–and it currently takes about a decade to build high-voltage interstate transmission lines, about half of which is spent on regulatory permissions. In addition, certain geographic locations work much better for solar and wind than others. Thus, this isn’t just a matter of expanding capacity of existing electricity lines, but of building additional transmission lines in new places. A US energy sector that relied heavily on intermittent sources of power like solar and wind would also need to build out city-scale battery storage capacity.
The growth of solar and wind power in size and efficiency has been a remarkable event in the US energy sector in the last two decades, such that they have come to play a cost-effective role in the electricity grid in many locations. (It seems worth noting that the withdrawal of existing subsidies for solar and wind power generation would truly demonstrate their cost-effectiveness.) But the numbers tell me that renewables as a group (counting hydroelectric) are about 11% of electricity input from primary sources; like all electricity, less than half of that input to the electricity sector reaches end-use sectors; and electricity itself only accounts for 18% of total US energy consumption.
Solar and wind power have a role to play in the US energy future. But taking seriously the numbers on sources and end-uses of energy, along with the role of the electricity sector, suggests that it will not be a predominant role any time soon.
