In many parts of the United States, installing a wind or solar farm is now cheaper than buying fuel for an existing fossil-fuel generator. And that is drastically changing the US electricity market and requires many people to update past forecasts. That motivated a group of researchers to rethink the costs and challenges of getting the entire US carbon neutral.
By building a US-wide energy market model, the researchers explored what it would take to get the country to the point where energy use had zero net emissions by 2050 – and even looked at a scenario where emissions is negative. They found that, as you might expect, costs drop dramatically – to less than 1 percent of GDP, even before factoring in the costs avoided by preventing the worst impacts of climate change. And as an added bonus, we would pay less for our power.
But the modeling also suggests that this end result will have some rather unusual features; we need carbon capture, but it won’t be connected to power plants, for example.
Model all things
Decent models of the future energy economy are complex. They usually involve splitting the grid by region and simulating typical demand using historical data, often scaled to reflect increased demand. They will then try to meet that demand using different energy sources, subject to a range of applied constraints. So in this case, one of the limitations would of course be to limit carbon emissions. The model then repeats possible ways to meet both demand and constraints in the most economical way and identifies an optimal solution.
In this case, the researchers set up a series of eight scenarios with different limitations. These include things like continuation of current trends into the future, a scenario where fossil fuel prices are low, and a scenario that simply identifies the cheapest carbon neutral road. Other variations include a fully renewable network and a high level of efficient technology, another where the land used for energy production is limited, and one where the United States manages to achieve negative net emissions.
The US uses fossil fuels for many things beyond electrical generation, and shifting this to zero-emission options is also part of the model. This includes things such as switching vehicles and heating to electrical options and adjusting industrial processes where possible. Carbon capture is used where necessary to achieve the emission targets.
One of the things that is immediately apparent when running the business-as-usual model is how much is already changing thanks to the price drops in wind and solar. In this scenario, CO2 emissions will decrease by 22 percent, largely due to the displacement of the use of coal. It’s worth knowing as any proposal for a target in that area could be rejected as irrelevant. Another thing that is clear is that decarbonising the energy system does not mean that the US will eliminate greenhouse gas emissions. The non-carbon greenhouse gases will still provide the equivalent of 500 megatons of carbon dioxide.
Efficiency and more
One of the things the research has made clear is that efficiency is imperative to meet emissions targets. By 2050, rising population and GDP should stimulate energy demand for lack of efficiency. But in order to achieve carbon neutrality, we will have to keep energy consumption roughly at the current level. Some efficiency will occur simply because electric vehicles and heating systems are inherently more efficient. But it’s clear we need a lot more, as the research team estimates that per capita energy consumption will need to fall by about 40 percent over the next 30 years to achieve carbon neutrality.
While energy consumption can be sustained, the increased electrification of homes and vehicles will mean that we will have to significantly increase production capacity. In the typical scenario, about 3.2 terawatts of new power would be involved, almost everything in the form of wind and solar energy.
The good news is that this is relatively inexpensive. The researchers estimate that the net cost of the transformation will total $ 145 billion by 2050, representing less than half a percent of GDP that year. That figure includes increased savings from electric heating and vehicles, which offset some of their costs. But it does not include lower costs due to climate change or lower health care expenditures due to reduced fossil fuel use. These savings will be significant and will almost certainly go far beyond just offsetting the costs.
Due to the lower costs of renewable generation, the authors predict that we will also generally spend less on electricity.
The most expensive scenarios increase the costs to about 1 percent of the 2050 GDP. In particular, net negative emissions are not the most expensive; instead, limiting land use reduces the amount of renewable energy that can be used, increasing costs.
Part of the reason it’s so cheap is because reaching the mark doesn’t require a replacement of viable hardware. Everything that needs to be taken out of service, from coal-fired generators to gas-fired water heaters, has a finite life. The researchers calculate that simply replacing everything with renewables or high-efficiency electrical versions will make the transition on time.
Not what you would expect
Many adopt a carbon neutral network, assuming that periods of low solar and wind production will be offset with gas generators that use carbon capture and storage. But this analysis suggests that the remaining gas-fired power plants simply won’t run often enough to provide an economic justification for the carbon capture hardware. Similar things are true with batteries; the periods when demand exceeds capacity are expected to be so rare that it does not make economic sense to build so many batteries to cover them.
Instead, gas-fired power plants will simply dump their CO2 emissions into the air. This will eventually become carbon neutral because we will still need some liquid fuels for things like air travel, and we will make it with carbon taken from the atmosphere, combined with hydrogen produced from water during periods of excessive renewable supply. The researchers estimate that we need 3,500 terawatts to make enough hydrogen – roughly the same amount of electricity we currently make.
“Until recently it was unclear whether variable renewable energy, nuclear or fossil fuel with carbon capture and storage would become the main form of generation in a decarbonised electricity system … The decrease in the cost of variable renewable energy in recent years, however, the situation has definitely changed. “
The scenarios with additional constraints also yield some strange results. The only scenario where nuclear energy makes economic sense is the scenario where land use is limited. This also drives more offshore wind and depends on fossil fuel power plants with carbon capture. Not surprisingly, this turns out to be the most expensive situation the researchers looked at. Carbon capture, along with improved use of biomass for energy, also plays a prominent role in a scenario where the shift to electric vehicles and appliances is slowed.
Going fully renewable actually forces much higher levels of carbon capture to ensure that fuel needs can be met without fossil fuels. And going net negative involves a variety of carbon capture and biofuels, with significant land use as a result of the latter.
Everything has changed
To some extent, the researchers themselves seem somewhat surprised by how much has changed in recent years. “The net cost of deep decarbonization, even to reach a 1 ° C / 350 ppm trajectory,” they write, “is significantly lower than estimates for less ambitious scenarios of 80 percent by 2050 a few years ago.” It also clarifies what an uncertain future has been. “Until recently, it was unclear whether variable renewable energy, nuclear or fossil fuel with carbon capture and storage would become the main form of generation in a decarbonised electricity system,” they note. “However, the fall in the cost of variable renewable energy in recent years has definitely changed the situation.”
Even if we go for deep decarbonisation, we will invest in the future. It costs money to get there, but we will have lower energy costs in the future if we pay the price up front – as well as better health and a more stable climate.
However, there are significant hurdles to getting there beyond simple economics. In the zero-emission future, we will install about 160 GW of wind and solar per year in less than two decades; In 2021 we will install only 15 GW. And the move to electric vehicles and appliances has to start now – anything that breaks has to be replaced with an electric version, which doesn’t seem to be happening.
But if this analysis is correct, there are good reasons to think it is worth getting started.
AGU Advances, 2021. DOI: 10.1029 / 2020AV000284 (About DOIs).