In many areas of the United States, installing a wind or solar farm is now cheaper than simply buying fuel for an existing fossil fuel-based generator. And that is dramatically changing the US electricity market and requiring many people to update previous forecasts. This motivated a group of researchers to take a fresh look at the costs and challenges of bringing the entire United States to carbon neutrality.
In building an energy market model for the entire United States, researchers explored what it will take to get the country to a point where its energy use had no net emissions in 2050 – and they even looked at a scenario where emissions are negative. They found that, as expected, costs drop dramatically – to less than 1% of GDP, even before counting the costs avoided by preventing the worst impacts of climate change. And, as an added bonus, we would pay less for our energy.
But the modeling also suggests that this end result will have some rather unusual features; we will need carbon capture, but it will not be attached to power plants, for example.
Model all things
Decent models of the energy economy of the future are complex. They typically involve dividing the grid by region and simulating typical demand using historical data, often scaled to represent increased demand. They will then try to meet this demand using different energy sources, subject to a set of restrictions applied. So, in this case, one of the restrictions would obviously be to limit carbon emissions. The model then iterates over possible ways to meet demand and restrictions in the most economical way possible, identifying an optimal solution.
In this case, the researchers set up a series of eight scenarios with different restrictions. This includes things like continuing current trends in the future, a scenario where fossil fuel prices are low and one that simply identifies the cheapest carbon neutral path. Other variations include a fully renewable network and high levels of efficiency technology, another in which the land dedicated to energy production is restricted and another in which the United States is able to achieve negative net emissions.
The United States uses fossil fuels for many things besides electricity generation, and switching them to emission-free options is also part of the model. This includes things like switching vehicles and heating for electrical options and changing industrial processes wherever possible. Carbon capture is deployed as needed to achieve emissions targets.
One of the things that is immediately apparent when operating the business-as-usual model is how much is already changing thanks to the price drops in wind and solar energy. In this scenario, carbon emissions will fall by 22%, largely due to the shift in the use of coal. It is worth knowing, as any proposals from a target in this area can be dismissed as irrelevant. Another thing that is clear is that decarbonizing the energy system does not mean that the United States will eliminate greenhouse gas emissions. Carbonless greenhouse gases will still provide the equivalent of 500 metric megatons of carbon dioxide.
Efficiency and beyond
One of the things that the survey made clear is that efficiency will be absolutely necessary to achieve emissions targets. In 2050, the increase in population and GDP should boost energy demand in the absence of efficiency. But in order to achieve carbon neutrality, we will have to keep energy use approximately equal to our current levels. Some efficiency will occur simply because electric vehicles and heating systems are inherently more efficient. But it is clear that we will need a little more than that, as the research team estimates that energy use per capita is expected to decrease by 40% over the next 30 years to achieve carbon neutrality.
Although energy use may remain stable, the increase in electrification of homes and vehicles will mean that we will need significant increases in generation capacity. The typical scenario would involve about 3.2 terawatts of new capacity, almost all of it in the form of wind and solar energy.
The good news is that doing this is relatively inexpensive. The researchers estimate that the net cost of transformation will be a total of $ 145 billion by 2050, which results in less than half a percent of GDP that year. This figure includes the biggest savings on electric heating and vehicles, which makes up for some of its costs. But it does not include reduced costs of climate change or lower health care costs due to reduced use of fossil fuel. These savings will be substantial and will almost certainly go far beyond offsetting the cost.
Due to the reduced cost of renewable generation, the authors project that we will also spend less on electricity in general.
The most expensive scenarios increase the cost to about 1% of GDP in 2050. Notably, going for negative net emissions is not the most expensive; instead, limiting land use reduces the amount of renewable energy that could be deployed, increasing costs.
Part of the reason it is so cheap is because reaching the goal does not require replacing viable hardware. Everything that needs to be taken out of service, from coal generators to gas hot water heaters, has a finite useful life. The researchers calculate that simply replacing everything with renewables or high-efficiency electrical versions will manage the transition in sufficient time.
Not what you would expect
Many assume a carbon neutral network assuming that periods of low solar and wind production will be smoothed out with gas generators using carbon capture and storage. But this analysis suggests that any remaining gas plants will simply not work often enough to provide an economic justification for carbon capture hardware. Similar things are true with batteries; periods in which demand exceeds capacity are expected to be so rare that it makes no economic sense to build so many batteries to serve them.
Instead, gas plants will simply dump their carbon emissions into the sky. This turns out to be carbon neutral because we will still need some liquid fuels for things like air travel, and we will do this with carbon taken out of the atmosphere, combined with hydrogen produced from water during periods of excess renewable supply. The researchers estimate that we would need 3,500 terawatts just to produce enough hydrogen – about the same amount of electricity that we currently produce.
“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 decarbonized electrical system … The drop in the cost of variable renewable energy in recent years, however, the situation has definitely changed. “
Scenarios with additional restrictions also produce some strange results. The only scenario in which nuclear energy makes economic sense is one in which land use is limited. This also drives more offshore wind energy and depends on carbon-capture fossil fuel plants. It is not surprising that this is the most expensive situation that the researchers analyzed. Carbon capture, together with the improved use of biomass for power generation, also stands out in a scenario where the switch to vehicles and appliances is delayed.
Becoming fully renewable requires much higher levels of carbon capture to ensure that fuel needs can be met without any fossil fuels. And becoming negative on the network involves a variety of carbon capture and biofuels, with substantial 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 meet a trajectory of 1 ° C / 350 ppm,” they write, “is substantially less than estimates for less ambitious 80% scenarios until 2050 a few years ago.” It also provides clarity about what has been an uncertain future. “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 decarbonized electrical system,” they note. “The fall in the cost of variable renewable energy in recent years, however, has definitely changed the situation.”
Now, even if we start with a deep decarbonization, we will be investing in the future. It will cost money to get there, but we will have lower energy costs in the future if we pay the price upfront – as well as improved health and a more stable climate.
There are, however, significant obstacles to getting there beyond simple economics. The emission-free future will involve installing about 160 GW of wind and solar energy per year in less than two decades; 2021 will see us installing only 15 GW. And the move to electric vehicles and appliances needs to start now – anything that breaks must be replaced with an electric version, which doesn’t seem to be happening.
But if this analysis is valid, there are good reasons to think that it is worth starting.
AGU Advances, 2021. DOI: 10.1029 / 2020AV000284 (About DOIs).