Net-Zero Emissions for a Dollar a Day

Reaching carbon neutrality by the middle of the century will require a lot more solar and wind capacity as well as new transmission lines, but it can be done at a net cost of about $1 per person per day, a new report claims.

Zero net emissions by 2050 will hold the rise in global warming to 1.5 degrees Celsius and prevent the most damaging effects of climate change, according to the Intergovernmental Panel on Climate Change. There are a number of ways to reach that goal, the report finds, but they typically include several common strategies: higher energy efficiency, cleaner energy, a wider adoption of electric technologies, and some carbon capture.

Researchers from the Lawrence Berkeley National Laboratory, the University of San Francisco, and the consulting firm Evolved Energy Research collaborated on the study.

In announcing the findings, the Berkeley Lab said the study was the first detailed, peer-reviewed roadmap for reaching carbon neutrality that involved making a detailed model of the entire U.S. energy and industrial system. The approach allowed researchers to see numerous ways of reaching carbon neutrality that had not been apparent in the past.

The report, published earlier this year in the journal AGU Advances, said the various pathways to carbon neutrality all could meet projected U.S. energy needs at a cost of between 0.2-1.2% of Gross Domestic Product. The plans did not call for exotic new technologies or the premature mothballing of the existing power infrastructure. Instead, the plans relied on only “commercial or near-commercial technologies.”

“No one is asking consumers to switch out their brand-new car for an electric vehicle,” said Margaret Torn, Berkeley Lab senior scientist and one of the lead authors of the study, in a written statement. “The point is that efficient, low-carbon technologies need to be used when it comes time to replace the current equipment.”

Pathways to carbon neutrality varied. The cheapest approaches were based on at least 80% wind and solar electricity while a 100% renewable energy system was possible but would cost more and require more dedicated land.

“In the next decade,” the report says, “the actions required for all pathways were similar: expand renewable capacity 3.5 fold, retire coal, maintain existing gas-generating capacity, and increase electric vehicle and heat pump sales to more than 50% of market share.”

The cost estimate of $1 day per person is “significantly” less than estimates of a few years ago because of recent advances in energy technology.

Berkeley Lab boiled down the report’s key recommendations to these eight steps that would be needed by 2030:

  • Increase solar and wind generating capacity to 500 gigawatts (GW), 3.5 times what it is now.
  • Eliminate coal from most electricity generation.
  • Keep the current natural gas−generating capacity for reliability.
  • Increase sales of zero-emission vehicles to 50% of the total.
  • Increase the sales share of heat pumps for heating and cooling buildings to 50% of the total.
  • Adopt strict efficiency goals for all new buildings and appliances.
  • Invest in R&D for carbon capture and sequestration as well as carbon-neutral fuels.
  • Build new transmission lines for electricity and new pipelines for carbon dioxide and hydrogen gas.

Many means to the same end

In all, researchers modeled eight different scenarios to learn how variables such as land use, energy costs, and consumer preferences would affect the outcome. These models were compared to a business-as-usual approach to energy, called the “reference” scenario. The cheapest path to carbon neutrality, called the “central” scenario, would see a reduction in C02 emissions of 84% below 2020 levels by 2050. Other models studied the impact of limiting the amount of land available for solar and wind, delayed consumer adoption of electric devices, lower consumer demand for energy, and using renewable sources for 100% of all primary energy.

One interesting conclusion was that gas-fired power plants should not be retired too quickly. The reason, researchers said, is that gas generation can balance out prolonged periods of high electrical demand and low output from renewable sources. On windy days, when demand was low, solar and wind produced excess electricity, which could be used in a variety of ways. No gas generation would be needed. But on days without much wind and lots of demand, gas plants would have to be brought online.

Just how much output from gas would be needed depends on the length of time that renewable output was low and demand on the system remained high.

“Energy storage was not competitive in meeting sustained energy deficits because the large quantity of energy needed required a large investment in storage, while the infrequent occurrence of such events resulted in very low storage utilization,” the authors noted. “These results illustrate why proposals for rapid retirement of gas-fired capacity are ill advised.”

While batteries weren’t economical for balancing demand and output for long stretches of time, they look like a cost-effective way of evening out production and demand over the course of a day.

Neither the cost nor the reliability of renewable-energy systems looks to be the biggest challenge, the study found. That’s likely to be scale and speed of building out the energy infrastructure. In the “central” scenario, wind and solar generation would increase by more than 160 GW per year, and that would jump to 260 GW per year in the scenario of 100% renewable primary energy. By comparison, today’s output is 150 GW.

To move that electricity around the country, researchers envisioned an increase in interregional transmission capacity of 168% for the central scenario, and up to 217% in other models. Most of that would be between the rich wind-generating areas of the Midwest, Southeast, and Mid-Atlantic.

In all, researchers said that reaching net-zero and net-negative carbon emissions in the energy and industry sectors by midcentury can be pulled off at low net cost:

“Recent declines in solar, wind, and vehicle battery prices have made decarbonizing the U.S. economy increasingly affordable on its own terms, without counting the economic benefits of avoided climate change and air pollution,” the study says. “The net cost of deep decarbonization, even to meet a 1°C/350 ppm trajectory, is substantially lower than estimates for less ambitious 80% by 2050 scenarios a few years ago. Even with decarbonization, future energy costs as a share of GDP are expected to be lower than today’s.”

Scott Gibson is a contributing writer at Green Building Advisor and Fine Homebuilding magazine.

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