In the summer of 1988, scientist James Hansentestified到国会that carbon dioxide from burning fossil fuels was dangerously warming the planet. Scientific meetings were held, voluminous reports were written, and national pledges were made, but because fossil fuels were comparatively cheap, little concrete action was taken to reduce carbon emissions.

Then, beginning around 2009, first wind turbines and then solar photovoltaic panels decreased enough in cost to become competitive in electricity markets. More installations resulted in more “学习曲线” cost reductions—the decrease in cost with every doubling of deployment. Since 2009, the prices of wind and solar power have decreased by an astonishing 72% and 90%, respectively, and they are now thecheapest electricity sourcesalthough some challenges still exist.

With the planet facing increasingly intense heat waves, drought, wildfires and storms, a path to tackle the climate crisis became clear: Transition the electric grid to carbon-free wind and solar and convert most other fossil fuel users in transportation, buildings, and industry to electricity.

The U.S. is headed in that direction.早期预测建议世界刚刚在2021年签署了可再生电力增长的创纪录的一年，之后record 33,500 megawattsof solar and wind electricity installed in the U.S. in 2020, according to BloombergNEF data. Evenfaster growth is expectedahead, especially given the Biden administration’s plans to tap高价值海上风力资源. But will it befast enough?

The Biden administration’s goal is to have acarbon-emissions-free grid by 2035. One recent study found that the U.S. will need tonearly triple its 2020 growth ratefor the grid to be 80% powered by clean energy by 2030. (As difficult as that may sound, China reportedly installed 120,000 megawatts of wind and solar in 2020.)

The foundation of this transition is a dramatic change in the electric grid itself.

Scaling up wind and solar

Hailed as thegreatest invention of the 20th century, our now-aging grid was based on fundamental concepts that made sense at the time it was developed. The original foundation was a combination of “base load” coal plants that operated 24 hours a day and large-scale hydropower.

从1958年开始，这些被核电站增强，核电站已经过几乎不断运营，以偿还其大资本投资。与煤炭和核电，太阳能和风是可变的;只有在太阳和风可用时，它们只能提供电力。

Converting to a 21st-century grid that is increasingly based on variable resources requires a completely new way of thinking. New sources of flexibility—the ability to keep supply and demand in balance over all time scales—are essential to enable this transition.

There are basically three ways to accommodate the variability of wind and solar energy: use storage, deploy generation in a coordinated fashion across a wide area of the country along with more transmission, and manage electricity demand to better match the supply. These are all sources of flexibility.

Storage is now largely being provided by lithium-ion batteries.Their costs have plummeted, andnew storage technologiesare being developed.

Expanded transmission is especially valuable. When the Northeast is experiencing peak electric demand in the early evening, there is still sun in the West. And, with more transmission, the large wind resources in the center of the country cansend electricity toward both coasts. Transmission studies have shown thatstronger interconnections among the country’s three power gridsare highly beneficial.

Making buildings more efficient and controlling their demand can also play a big role in cleaning up the grid.建筑物use 74% of U.S. electricity. Interconnected devices and equipment with smart meters can reduce and reshape a building’s power use.

Innovations that make 100% clean power possible

Many analysts believe the U.S. can cost-effectively and reliably operate a power gridwith 80% to 90% clean electricity,但人类最后不会10%到20%tably more challenging. While short-duration storage, lasting four hours or less, is becoming ubiquitous, we will likely need to provide power during some periods when wind and solar resources are at low levels (what the Germans call dunkelflaute, or “dark doldrums”). An expanded national transmission network will help, but some amount of long-duration storage will likely be needed.

Numerous options are being explored, includingalternative battery technologiesand green hydrogen.

Flow batteriesare among the promising approaches that we are working on at theRenewable and Sustainable Energy Instituteat the University of Colorado. In a typical design, liquid electrolyte flows between two storage tanks separated by a membrane. The tanks can be scaled up in size corresponding to the desired storage duration.

Green hydrogenis a potential storage option for very long durations. It is produced by splitting water molecules with an electrolyzer powered by renewable electricity. The hydrogen can be stored underground (or in above-ground tanks) and either burned in combustion turbines or converted back to electricity in fuel cells. Green hydrogen is currently very expensive but is expected to become more affordable as thecost of electrolyzers decreases.

此外，新的业务，市场设计和电网运营商模型正在出现。Community solar gardens, for example, allow homeowners to purchase locally produced solar electricity even if their own roofs are not suitable for solar panels.微电网are another business model becoming common on campuses and complexes that produce electricity locally and can continue to operate if the grid goes down. Clean microgrids are powered by renewable energy and batteries.

Innovative market designs includetime-of-use ratesthat encourage electricity use, such as for charging electric vehicles, when renewable electricity is plentiful.Expanded balancing area coordination了阿n variable solar and wind resources from a wide region to provide a smoother overall supply. Improved grid operations include高级风险和太阳能预测to minimize wasted power and reduce the need for costly standby reserves.Dynamic line ratingallows grid operators to transmit more electricity through existing lines when favorable weather conditions permit.

Across the economy, greater attention to energy efficiency can enable power sector transformation, minimizing costs, and improving reliability.

Nuclear power is also essentially carbon-free, and keeping existing nuclear plants running can make the transition to renewables easier. However, new nuclear plants in the U.S. are very expensive to build, have long construction times and may prove too costly to operate in a manner that would help firm variable solar and wind.

在我们看来，气候变化的紧迫性要求全力以赴解决它。拥有2035个排放目标是重要的，但排放量减少了美国。达到这一目标至关重要。第1号需要是最小化将二氧化碳和其他温室气体添加到大气中。世界已经拥有将电网获得80％至90％的碳无碳的工具，技术专家正在探索广泛的有希望的选择，以实现持续10％至20％。

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Charles F. Kutscher is a fellow and senior research associate at the Renewable & Sustainable Energy Institute, University of Colorado Boulder. Jeffrey Logan is associate director of energy policy and analysis at the Institute. This postoriginally appeared at The Conversation.