Wind, hydro or nuclear? How to get 100% clean electricity

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The United States gets about 40% of its electricity from carbon-free sources, including renewables and nuclear, and researchers have a pretty good idea of ​​how to cost-effectively reach about 90%.

But those last 10%? It is expensive and there is little agreement on how to do it.

A new article in the journal Joule identifies six approaches to achieving this last 10%, including the use of wind and solar power, the development of nuclear energy and the development of long-term energy storage using hydrogen.

It’s not a one-size-fits-all path, said Trieu Mai, lead author of the paper and senior energy researcher for the National Renewable Energy Laboratory in Golden, Colorado.

“A 100% carbon-free power system will require a portfolio of resources,” he said. “But humility is needed to accept that we don’t know what the optimal combination will be to solve the last 10%.”

The most important point, he said, is that researchers and industry must do the work now to determine which technologies are most viable in order to meet the goal, set by the Biden administration, of achieve net zero emissions in the electricity sector by 2035.

Here are the six options in the document, along with what I consider their pros and cons:

• Wind and solar power with short-term energy storage and extension of interstate power lines. Advantages: Low costs and the technology is already available. Cons: To be available 24 hours a day, wind and solar must work alongside energy storage systems, so it is a flat rate. Additionally, the country will need a major expansion of interstate power lines to provide wind and solar power, a costly and politically strained prospect. And, the growth of wind and solar requires a lot of open land, which has led to local-level conflict in communities that don’t want to host the projects.
• Other renewables, including geothermal, hydropower and biomass. Advantages: The technologies are already available and can operate 24 hours a day. Disadvantages: Relatively high costs. Geothermal has limitations as to where it can be built. Hydroelectricity is vulnerable to falling water levels, and the construction of new hydroelectric plants could pose a danger to ecosystems. Biomass, which includes power plants that burn wood, is controversial due to loss of trees and disagreement over whether it should be considered a carbon-free energy source.
• Nuclear, alongside fossil fuels and carbon capture. Benefits: Nuclear is an essential part of today’s carbon-free electricity mix, showing how the technology could be used in a future grid. Fossil fuel power plants, if they could be equipped with carbon capture technology, are well suited to provide peak power. Both can operate 24 hours a day. Cons: Nuclear is expensive and has a lot of baggage in terms of security issues. As for carbon capture, the technology has not been successfully deployed at scale and has been dismissed by some analysts as too expensive and inefficient. (The NREL report puts these two resources in the same category due to some common characteristics, including 24/7 capability, high upfront costs, and average operational costs.)
• Long-term energy storage thanks to hydrogen. Pros: The idea is that energy companies would use renewable energy to produce hydrogen from water, and then the hydrogen could be stored in vast caverns. During periods of high electricity demand, hydrogen could be released and burned to power a gas turbine or fuel cell. If this could be done cheaply and stocked in sufficient quantities, this is an opportunity to replicate the role of natural gas-fired power plants in the current grid. Cons: Of the six approaches discussed here, this one is perhaps the furthest from being market-ready, so talking about its pros and cons involves a lot of speculation.
• Removal of carbon dioxide. Benefits: This covers a variety of approaches to removing carbon from the environment, including direct air capture and planting trees. Although this is not a major part of reducing emissions in the electricity sector, it could be essential in other sectors, such as heavy industry, which are more difficult to decarbonise. Cons: Some carbon removal technologies are expensive compared to other options and it is not clear that they would work at the scale needed.
• Reduced electricity demand. Advantages: Low costs. As proponents of energy conservation like to say, it’s much cheaper to conserve a kilowatt-hour than to produce one. Disadvantages: Energy-saving measures, which include a range of programs and technologies, can be complicated to implement and require buy-in from decision-makers and consumers.

The “bottom 10%” challenge is nothing new. What is new is the need to serve the last 10% with carbon-free resources.

In the current grid, more than a third of the country’s power plant capacity is needed to meet about the remaining 10% of demand, according to the NREL document. This means that there are hundreds of power stations that sit idle most of the time, but are a critical resource to ensure there is enough electricity to meet demand on the hottest days and coldest of the year.

Much of this “peak power” is provided by natural gas-fired power plants, which can rise and fall in the short term. But these factories will have to close or find a way to store their emissions in a carbon-free network.

The document is diplomatic because it addresses some of the most controversial debates in the energy world.

A growing segment of energy researchers claim that the electrical system can run on 100% renewable energy, which would mean that renewables and energy storage would provide the remaining 10%. This approach sees no good reason to build new nuclear power plants or use carbon capture systems on fossil fuel power plants, citing high costs and various other concerns.

At the same time, a large group of energy researchers say nuclear and carbon capture are key to achieving carbon-free electricity. This party has doubts about the ability of renewable sources to meet all needs, citing concerns about land availability and the intermittent nature of wind and solar. They note that wind and solar are not a low-cost option given the amounts of storage and power line capacity needed to make these resources reliable to meet peak demand.

Mai acknowledged the strong feelings surrounding some of these issues.

“We just want people to recognize that in every option there are tradeoffs,” he said. “We recognize the degree of uncertainty with all of these technologies, and we need to put that on the table.”

Furthermore, he pointed out that the document asks a specific question about meeting the last 10% of electricity demand, and that there is a separate, and equally important, question about the right mix of resources to reach 90%. carbon-free electricity. .

To reach 90%, roughly double the current share, Mai believes wind, solar and battery power storage will play a major role, along with additional interstate power lines.

It is therefore possible to say that the country should have a lot more renewable energy than it has today, and also to say that the question remains open as to whether wind and solar are well suited for provide the remaining 10%.

In all of this, there is something encouraging: researchers and energy companies have figured out how to begin the transition to 100% carbon-free electricity, and they have a pretty good idea of ​​what the intermediate steps will look like. Now they’re starting to dig deep into how this journey to a zero-carbon grid might end.