Green Energy

Just as a superb meal requires the right ingredients prepared expertly, the production of better green fuel alternatives requires combining the right materials and methods. Recently, a team of researchers from China and the U.K. have found new ways to optimize the recipe for the production of solar fuels. Their findings have been published in two articles, one in the journal Applied Surface Science, and the other in Optical Materials. Hydrogen is a zero-emission energy source that can be produced from water using solar energy and offers great potential in helping to mitigate the climate crisis. The process of producing hydrogen from water is called “water splitting” because it breaks water into its two elements, hydrogen and oxygen. Water splitting requires a semiconductor photocatalyst, a substance or compound that absorbs sunlight and then uses its energy for the splitting process. However, semiconductor photocatalysts for water splitting vary in their efficiency. By using novel combinations of methods and materials to create new types of photocatalysts, the researchers have improved the efficiency of hydrogen production. Dr. Graham Dawson, who led the studies at Xi’an Jiaotong-Liverpool University, explains, “By adding materials such as gold or boron nitrate to our photocatalysts using particular mixing methods, we can increase the amount of light that is absorbed. “The more light that is absorbed, the more suitable energy there is for water splitting, and so hydrogen production is increased,” he says. Finding the perfect recipe Modifying the materials commonly used as photocatalysts helps to overcome their limitations, says the first author of the article in Applied Surface Science, Yanan Zhao. One of the most widely used materials is titanium dioxide. “Titanium dioxide can harness energy directly from the sun with negligible pollution and shows great potential in the development of solar-related technologies,” she says. “However, it can only be activated by UV light, which accounts for only 7% of sunlight. It cannot absorb the energy of visible light,” explains Zhao, who received her master’s degree in chemistry from XJTLU and was awarded a full scholarship to pursue her Ph.D. at the University of North Dakota. The researchers found that adding boron nitride to a form of titanium dioxide produced a photocatalyst that can absorb the energy of more wavelengths than UV light. Boron nitride, a compound of boron and nitrogen, has good electrical conductivity and can withstand temperatures of up to 2,000°C. Zhao explains the process: “To prepare the composite photocatalytic material, we combined boron nitride with titanate nanotubes, which are tube-like structures with dimensions measured in nanometers—one nanometer is one-billionth of a meter. “By optimizing the ratio of boron nitride to titanate nanotubes and using chemical processes to combine the compounds, we produced a very stable composite photocatalyst. It can absorb light from a wider range of wavelengths and produce more hydrogen compared to traditional physical mixing methods.” A gold rush In the second study, published in Optical Materials, Dr. Dawson’s team found an additional option for improving photocatalytic efficiency in water splitting. They covered the surfaces of specific types of photocatalytic structures with a specific size of gold nanoparticles thereby increasing the amount of light they could absorb. Shiqi Zhao, this study’s first author, explains, “The structure of the photocatalytic material used is very important. In this study, we used two forms of photocatalytic nanostructures—nanosheets and nanotubes. We coated them with differently sized gold particles to see which combination produced the highest amount of hydrogen from water. “Our results showed that the nanosheets modified with small, uniform gold particles had the best photocatalytic performance out of the materials we tested. These gold-coated nanostructures showed approximately 36 times more photocatalytic hydrogen production performance than unmodified nanotubes,” he continues. “This provides a new understanding of how semiconductor photocatalytic materials can be modified with gold nanoparticles and has valuable applications in the fields of photocatalytic hydrogen production, solar cells and optical sensors.”

The U.S. electric grid faces simultaneous, evolving pressures. Demand for power from the grid is increasing as people adopt electric cars and building energy is transitioned from gas to electricity. At the same time, climate change is driving more extreme weather. Events like the 2020 heat wave that led to rolling blackouts in California are relatively infrequent, but they are happening more often—and utilities need to be ready for them.

New research points to a flexible, cost-effective option for backup power when trouble strikes: batteries aboard trains. A study from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) finds that rail-based mobile energy storage is a feasible way to ensure reliability during exceptional events.

Previous research has shown that, in theory, rail-based energy storage could play a role in meeting the country’s daily electricity needs. Berkeley Lab researchers wanted to take this idea further to see whether rail-borne batteries could cost-effectively provide backup power for extreme events—and whether the scenario was feasible on the existing U.S. rail network.

“There’s a lot of uncertainty around when extreme supply shortfalls are going to happen, where they will happen, and how extreme they may be,” said Jill Moraski, a graduate student at the University of California Berkeley, a researcher at Berkeley Lab, and the paper’s lead author. “We found that the U.S. rail network has the capacity to bring energy where it’s needed when these events happen, and that it can cost less than building new infrastructure.”

The paper, “Leveraging rail-based mobile energy storage to increase grid reliability in the face of climate uncertainty,” was published recently in the journal Nature Energy.

A ready resource in freight rail

The idea for the study came to Amol Phadke, a Berkeley Lab staff scientist and co-author of the study, while he was watching a long freight train trundle past at a railway crossing. He began counting the cars and tallied over 100 on that single train.

“A thought then struck me—how many batteries could such a massive train carry? If those were used for emergency backup power, how significant would their contribution be?” Phadke writes in a briefing on the study. “A quick, back-of-the-envelope calculation revealed an astounding capacity, potentially sufficient to provide power to every household in Berkeley for a few days.”

To meet electricity demand and build capacity for backup power, the U.S. is building long-distance transmission lines and installing stationary banks of batteries.

“While both of these resources are necessary, we wanted to explore additional, complementary technologies,” said Natalie Popovich, a Berkeley Lab research scientist and co-author of the study. “We have trains that can carry a gigawatt-hour of battery storage, but no one has thought in a cohesive way about how we can couple this resource with the electric grid.”

The U.S. rail network is the largest in the world, covering nearly 140,000 miles (220,000 kilometers). The study looked at historical freight rail flows, costs, and scheduling constraints to see whether railroads could be summoned to transport batteries for high-impact events, given that grid operators typically have at least a few days’ notice, and sometimes up to a week, when extreme weather is coming.

The analysis found that mobile energy storage could travel between major power markets along existing rail lines within a week without disrupting freight schedules.

What about stationary options?

The researchers compared the cost of deploying batteries on rail for low-frequency events with the investment costs of stationary energy storage and transmission lines. In cases where the trains need to cover distances of about 250 miles (400 kilometers) or shorter—roughly equivalent to a trip from L.A. to Las Vegas—rail-based energy storage could make more sense cost-wise than building stationary battery banks to fill supply gaps that happen during less than 1% of the year’s total hours.

At those shorter distances, transmission lines remain cost-effective compared to batteries on rail if they are used frequently. When the travel distance grows to more than 930 miles (1,500 kilometers)—say, a trip from Phoenix to Austin—rail becomes cheaper than transmission lines for low-frequency events. This third option could save the power sector upwards of 60% of the total cost of a new transmission line or 30% of the total cost of stationary battery storage, the study concludes.

The study points to New York State, with its robust freight capacity and current transmission constraints between upstate clean energy generation and downstate load centers, as an example of where rail-based mobile energy storage could work well. In other cases, it may make sense for multiple states to share the additional capacity from a rail-based battery bank.

“This is not necessarily a resource that needs to be in one region,” Moraski said. “It can operate similar to an insurance policy, where you spread the coverage across risks for a wide geographic region.”

A train of thought worth following

Regulatory and infrastructure hurdles exist, the authors note. The U.S. lacks adequate interconnections to take power off the train and essentially plug it into the grid. And current electricity markets have no framework for approving, pricing, and regulating a mobile energy asset the way they do for conventional power plants. Policies would need to be revised, and efforts to deploy the storage would need to capitalize on existing interconnections where possible, such as retiring coal plants, which have existing rail lines and interconnection rights.

The researchers see further opportunities to quantify the benefits of rail-based mobile energy storage beyond the scope of the current study, taking into account larger territories, a decarbonized grid, and future climate conditions. They emphasize that extending energy storage across the rail network is not a replacement for important infrastructure such as transmission lines, but could be an important complement.

“Our paper gives a top-level overview of how rail-based mobile energy storage could benefit today’s grid, in today’s climate,” Moraski said. “As we look toward a future with more electrification, more fluctuating renewable energy, and more frequent extreme events, the case for adding rail-based energy storage to the mix may become even stronger.”

Smoke from Canada’s wildfires is preventing solar panels from catching sunlight, and solar power generation in the northeast United States is tumbling by more than 50% as a result.

ISO New England, the operator of the grid, said on Thursday that “In recent days, smoke from wildfires in Canada has traveled to New England, significantly lowering production from solar resources in the region compared to what ISO New England would expect absent the smoke.”
Solar power generation in New England was 56% below last week during times of peak demand this week, according to the operator quoted by Bloomberg.

Solar power accounts for around 3% of electricity generation in New England, with natural gas and nuclear the biggest sources with 52% and 26% share, respectively.

The smoke from the Canadian wildfires has also lowered actual temperatures in New England compared to what weather models are forecasting. This leads to lower demand on the regional grid, as there is less need for things like air conditioning, ISO New England said.

“Because these smoky conditions are unprecedented in the region, there is little, if any, historical information to rely on, creating further complications in generating accurate forecasts,” the grid operator added.

The plunge in solar power generation combined with the lower temperatures as a result of the smoke makes forecasting demand for the grid challenging, according to ISO New England.
“Despite these complications in forecasting, ISO New England continues to manage the regional grid under normal operating conditions, and does not anticipate this changing,” it noted.

New York ISO said that smoke from Canada’s wildfires, which is blocking sunlight, resulted in a combined reduction in peak solar energy production of 1,466 MW for June 6-7, for a two-day total peak production of 4,405 MW.

In the area serviced by PJM Interconnection, from North Carolina to Illinois, solar power generation this week has been 25% below last week’s average solar output levels.

Both Uber and Lyft ride-hailing services have pledged to fully electrify their vehicle fleets by 2030 in the United States.

The move would eliminate tailpipe pollution while shifting emissions to the power plants that provide electricity to charge EV batteries, likely resulting in a significant drop in overall emissions of climate-warming greenhouse gases.

Good news all around, right? Hold on.

A new study from researchers at the University of Michigan and Carnegie Mellon University estimates that the overall benefits to society of switching ride-hailing vehicles from gasoline to electric would be very modest—on average, a 3% gain per trip when other “costs on society” are factored in.

Those societal costs include increased traffic congestion, collision risk and noise due to Uber and Lyft drivers traveling to and from fast-charging stations, according to the study published online in the journal Environmental Science & Technology.

“Our simulation showed that electric vehicles drive greater distances without a passenger than do gasoline vehicles, since EVs have to travel to chargers more often than gasoline vehicles have to refuel,” said study senior author Parth Vaishnav, assistant professor at U-M’s School for Environment and Sustainability.

“Furthermore, fast chargers are not as ubiquitous as gas stations, which means EVs have to travel farther each time they refuel than gasoline vehicles.”

In their simulation, the researchers used a new high-resolution model called AgentX with real-world Uber and Lyft trip data collected in the Chicago area from 2019 to 2022. Chicago is one of the largest ride-hailing markets in the country, and the number of daily trips averaged roughly 300,000 prior to the COVID-19 pandemic.

The researchers modeled more than a million Uber and Lyft trips taken on weekdays, weekends and during different seasons. They included trips taken before the pandemic started, as well as trips during the period after the widespread rollout of vaccines.

A set of standard economic tools was used to express costs to society in terms of dollars. Though the study results are specific to Chicago, the findings likely apply more broadly, according to the researchers.

The study found that:

• Electrification of Chicago’s ride-hailing fleets would reduce lifetime greenhouse gas emissions by 40%-45% when compared to gasoline-powered vehicles. The reduction is largely due to the greater efficiency of electric vehicles.
• Health impacts from local air pollution would increase an estimated 6%-11% per trip, on average, due to higher concentrations of local pollutants (such as sulfur dioxide, nitrogen oxides and particulate matter) from fossil fuel-burning power plants.
• Extra driving to and from charging stations would increase traffic-related harms to society (congestion, crash risk and noise) by 2%-3% per trip.
• Overall, full electrification of ride-hailing would reduce total harms to society by about 3% per trip.

A 3% reduction in costs to society translates to about $1.5 million per year in savings for the city of Chicago. To put that number in context, ride-hailing is estimated to generate $4 million to $5 million in revenues per day in Chicago.

“It may seem counterintuitive that overall costs to society fall so little, even though greenhouse gas emissions are substantially reduced by the switch to EVs,” said study lead author Aniruddh Mohan, formerly a doctoral student under Vaishnav at Carnegie Mellon and now a postdoctoral fellow at Princeton University.

“But on a per-mile basis, greenhouse gas emissions are a very small part of the total costs imposed on society by these vehicles. The costs are dominated by traffic externalities—congestion, crash risk and noise—which are directly correlated with vehicle distance traveled. And vehicle distance traveled will increase with electrification.”

About 80% of the total costs to society result from traffic-related factors, while 20% are due to emissions, according to the study.

The assessment includes the cradle-to-grave costs to society of building, operating and disposing of EVs and gasoline-powered vehicles. Those lifetime costs include battery manufacturing, gasoline refining and vehicle construction.

For EVs, the researchers looked at battery size and how it affects vehicle impacts. Making smaller battery packs requires less energy and leads to lighter vehicles, both of which might lead to greenhouse gas emissions savings.

To their surprise, smaller battery packs did not help. A smaller battery pack meant that EV drivers visited chargers more often, and those additional miles canceled emissions gains from using a smaller battery pack, according to the study.

“Overall, our findings made it very clear that a large part of the damage that cars cause is unrelated to their air emissions and is therefore unlikely to be eliminated by electrification,” Vaishnav said.

“Electrification is a small win for society. A bigger win would be to dramatically reduce our dependence on cars. Policies that decrease vehicle distance traveled through investments in public transit and infrastructure for biking and walking, or that reduce crash risk by improved vehicle safety, are critical.”

Gas-insulated equipment (GIE) that utilizes the most potent greenhouse gas sulfur hexafluoride (SF6) as insulation and arc-quenching medium has been widely used in the power industry. Seeking eco-friendly insulating gas with advanced performance for next-generation SF6-free GIE is significant for the “net-zero” goal and sustainable development.

A research team led by Xiaoxing Zhang of Hubei University of Technology in China and scientists from Wuhan University, Southeast University, North China Electric Power University, Université de Toulouse, Xi’an University of Technology, Schneider Electric and South China University of Technology recently summarized the advances in eco-friendly gas insulating medium for next-generation SF6-free equipment. The review report was published in the journal iEnergy as the cover article on March 31, 2023.

An overview of the SF6-based GIE, the emission and reduction policies of SF6 were introduced firstly to clarify the necessity of seeking eco-friendly insulating gas.

“SF6 is one of the most potent greenhouse gases with a global warming potential of 25200 and an atmospheric lifetime of 3200 years. The power industry accounts for 80% of the SF6 consumption, which value reaches over 7000 tons in China. Various countries have established regulations on the use, recovery and treatment of SF6, promoting the development of eco-friendly insulating gas” said Prof. Zhang.

Basic requirements for eco-friendly gas including environmental features, insulation & arc-quenching performance, stability, material compatibility, biosafety were proposed and the main categories containing traditional gas (CO2, N2, air), Perfluorocarbons and Trifluoroiodomethane, Fluorinated-nitrile(C4F7N), Fluorinated-ketones(C5F10O, C6F12O), Hydrofluro-Olefins (HFO-1234ze(E), HFO-1336mzz(E)) were introduced. The molecular design method of eco-friendly gas was also provided.

Recent progress of various eco-friendly insulating gas in terms of dielectric insulation (in terms of AC/DC breakdown, LI breakdown, partial discharge, surface flashover), arc-quenching (in terms of particle compositions, thermodynamic properties, transport coefficients, radiation coefficients, post-arc dielectric breakdown properties), stability and decomposition (in terms of thermal, discharge stability, decomposition mechanism), materials compatibility (in terms of metal, epoxy resin, elastomer, Adsorbent), biosafety (in terms of LC50, target organ toxicity, by-products toxicity) were highlighted.

The latest application of eco-friendly insulating gas in medium-voltage (MV), high-voltage (HV) scenarios as well as relevant maintenance-related technologies were also summarized.

“The C4F7N/CO2, C5F10O/air based gas insulated switchgear, gas insulated transmission line, ring main units, etc. have been developed by GE, ABB since 2016. The other fluorinated-free technology roadmap using technical air combined with vacuum interruption also have been focused,” said Prof. Zhang.

Although substantial efforts have been made in the field, several significant challenges remain that call for more solutions to achieve the next-generation SF6-free GIE in the future. The improvement of stability, interruption capacity, material compatibility is highly desired. The SF6 control and recycling, insulation coordination, scientific management of PFAS, etc. will hopefully steer the development of eco-friendly insulating gas and GIE.

Policymakers seeking to make the U.S. electric grid less reliant on fossil fuels have long looked north to Canada and its abundant surplus of hydropower, advocating for new transmission lines to bring more of that cheap, clean electricity south.

But with demand for green energy growing north of the border, too, there are new concerns that Canada’s hydro supply isn’t as bottomless as it once seemed.

A study published in May by the Montreal Economic Institute predicted that Quebec, now home to one of the world’s largest hydroelectric systems, will over the next decade fall short of the generating capacity needed to meet increasing demand for power in the province.

Some New England lawmakers are questioning the wisdom of plans to construct new transmission lines across their states, despite Canadian energy giant Hydro-Québec’s insistence it can still meet its energy obligations.

“They have their own energy needs,” Maine state Sen. Nicole Grohoski said of the Canadians. The Democrat said it is “overly optimistic” for policymakers to rely on Canadian hydropower. “There are industrial users up there that are already having issues and they’re not interested in investing in Quebec because they’re worried about power supply.”

Over decades, Hydro-Québec, which is owned by the Province of Quebec, has built a series of hydro-electric facilities, most in the northern reaches of the province. The dams’ construction and the subsequent flooding of areas behind them has drawn protests from indigenous groups and environmentalists on both sides of the border.

But in the process Hydro-Québec has become the largest producer of renewable energy in North America. It produces nearly half of all Canadian hydropower as well as a smaller number of wind and other renewable projects.

The capacity to generate electricity left the utility with extra power to sell in the energy-hungry U.S. There are already a number of transmission lines that carry power from Canada to the United States and more on the drawing board.

A line from the border down Lake Champlain and the Hudson River to New York City is under construction. Authorities in Maine just gave approval to resume construction of a separate line from the border to Massachusetts.

There are also pending proposals for lines to reach southern New England through Vermont and New Hampshire.

Connecticut Gov. Ned Lamont, a Democrat, has been rallying his fellow New England governors to seek federal funding for transmission line projects. The push comes as billions of dollars are available for electric transmission line projects under President Joe Biden’s infrastructure law.

“We’ve got to speed things up when it comes to reliability and reserves and more carbon-free power,” Lamont said.

But Quebec is on its own quest to reduce use of planet-warming fuels. The province is hoping to achieve carbon neutrality by 2050, while demand for hydropower is predicted to grow 14% over the next decade.

“No province now is in a position where they see huge surpluses of electricity that would be available for exports,” said Pierre-Oliver Pineau, an expert on Canadian energy policy and professor at HEC Montréal, the University of Montreal business school.

A bipartisan group of lawmakers from Maine who oppose the proposed 145-mile (233-kilometer) New England Clean Energy Connect transmission line recently asked the governor of Massachusetts to review whether Hydro-Québec can still meet its energy obligations.

They also sent a letter to Quebec Premier François Legault questioning whether there will be enough electricity to power both that line and the Champlain-Hudson Power Express line, which is currently under construction. That line is intended to provide New York City with 20% of its power needs.

The Maine lawmakers said they worry new dams might need to be built, a process that could take years.

“Many people in New England have lived with a myth that Quebec has so much power that it doesn’t know what to do with it all,” the legislators said in a joint statement.

Local news has reported Jean-Hugues Lafleur, Hydro-Québec’s financial officer, said during an analyst call last month that the company could meet the energy demand when it signed the contract in 2018 and that “we still have enough energy to supply the New England region.”

Connecticut’s Department of Energy and Environmental Protection Commissioner Katie Dykes said hydropower is just one piece of the puzzle and that the New England states are also working together to decarbonize the electric system through other means, including offshore wind.

Hydro-Québec, meanwhile, has also expressed interest in transmission lines capable of moving power in both directions. Developers of the proposed 1,000-megawatt transmission line known as New England Clean Power Link, which would run from Quebec to southern New England through Vermont, are working to modify its approval to turn it into a bi-directional line.

“This modification would allow the line to be used as originally intended to move hydropower from Canada to New England, while also allowing the line to move loads such as off-shore wind generation from New England to Canada for storage and later use, which could materially help winter reliability in the region,” said June Tierney, the commissioner of the Vermont Department of Public Service.

Last month, the state of New Hampshire highlighted a new entrant into the northeast transmission mix by announcing plans for a 211-mile, 1,200-megawatt power line that would enter the United States at Canaan, Vermont, and follow a buried route south. If built, the $2 billion proposal would also be a bi-directional line.

“This project is also not dependent solely on hydropower—it would have the ability to deliver other forms of clean energy being generated in Canada—such as wind and solar power—to New England,” said a statement from the utility National Grid, which is proposing the line.

Kerrick Johnson, chief innovation and communication officer for the Vermont Electric Power Cooperative, which manages the state’s electric transmission system, said there’s a transformation underway of the electric production and distribution system across the world and including the Northeastern United States and eastern Canada.

“This is a new chapter in the shared-energy history of North America,” he said.