EV charging station operational in Barrie

US Electricity Generation H1 2018 saw wind and solar gains but hydro declines, as natural gas led the grid mix and coal fell; renewables' share, GWh, emissions, and capacity additions shaped the power sector.

Key Points

It is the H1 2018 US power mix, where natural gas led, coal declined, and wind and solar grew while hydro fell.

✅ Natural gas reached 32% of generation, highest share

✅ Coal fell; renewables roughly tied nuclear at ~20%

✅ Wind and solar up; hydro output down vs 2017

To complement our revival of US electricity capacity reports, here’s a revival of our reports on US electricity generation.

As with the fresh new capacity report, things are not looking too bright when it comes to electricity generation. There’s still a lot of grey — in the bar charts below, in the skies near fossil fuel power plants, and in the human and planetary outlook based on how slowly we are cutting fossil fuel electricity generation.

As you can see in the charts above, wind and solar energy generation increased notably from the first half of 2017 to the first half of 2018, and the EIA expected larger summer solar and wind generation in subsequent months, reinforcing that momentum.

A large positive when it comes to the environment and human health is that coal generation dropped a great deal year over year — by even more than renewables increased, though the EIA later noted an increase in coal-fired generation in a subsequent year, complicating the trend. However, on the down side, natural gas soared as it became the #1 source of electricity generation in the United States (32% of US electricity). Furthermore, coal was still solidly in the #2 position (27% of US electricity). Renewables and nuclear were essentially in a tie at 19.8% of generation, with renewables just a tad above nuclear.

Actually, combined with an increase in nuclear power generation, natural gas electricity production increased so much that the renewable energy share of electricity generation actually dropped in the first half of 2018 versus the first half of 2017, even amid declining electricity use in some periods. It was 19.8% this year and 20% last year.

Again, solar and wind saw a significant growth in its market share, from 9% to 9.9%, but hydro brought the whole category down due to a decrease from 9% to 8%.

The visuals above are probably the best way to examine it all. The H1 2018 chart was still dominated by fossil fuels, which together accounted for approximately 60% of electricity generation, even though by 2021 non-fossil sources supplied about 40% of U.S. electricity, highlighting the longer-term shift. In H1 2017, the figure was 59.7%. Furthermore, if you switch to the “Change H1 2018 vs H1 2017 (GWh)” chart, you can watch a giant grey bar representing natural gas take over the top of the chart. It almost looks like it’s part of the border of the chart. The biggest glimmer of positivity in that chart is seeing the decline in coal at the bottom.

What will the second half of the year bring? Well, the gigantic US electricity generation market shifts slowly, even as monthly figures can swing, as January generation jumped 9.3% year over year according to the EIA, reminding us about volatility. There is so much base capacity, and power plants last so long, that it takes a special kind of magic to create a rapid transition to renewable energy. As you know from reading this quarter’s US renewable energy capacity report, only 43% of new US power capacity in the first half of the year was from renewables. The majority of it was from natural gas. Along with other portions of the calculation, that means that electricity generation from natural gas is likely to increase more than electricity generation from renewables.

Jump into the numbers below and let us know if you have any more thoughts.

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Finland Shadow Fleet Cable Investigation details suspected Russia-linked sabotage of Baltic Sea undersea cables, AIS dark activity, and false-flag tactics threatening critical infrastructure, prompting NATO and EU vigilance against hybrid warfare across Northern Europe.

Key Points

Finland probes suspected sabotage of undersea cables by a Russia-linked vessel using flag of convenience and AIS off.

✅ Undersea cable damage in Baltic Sea sparks security alerts

✅ Suspected shadow fleet ship ran AIS dark under false flag

✅ NATO and EU boost maritime surveillance, critical infrastructure

In December 2024, Finland launched an investigation into a ship allegedly linked to Russia’s “shadow fleet” following a series of incidents involving damage to undersea cables. The investigation has raised significant concerns in Finland and across Europe, as it suggests possible sabotage or other intentional acts related to the disruption of vital communication and energy infrastructure in the Baltic Sea region. This article explores the key details of the investigation, the role of Russia’s shadow fleet, and the broader geopolitical implications of this event.

The "Shadow Fleet" and Its Role

The term “shadow fleet” refers to a collection of ships, often disguised or operating under false flags, that are believed to be part of Russia's covert maritime operations. These vessels are typically used for activities such as smuggling, surveillance, and potentially military operations, mirroring the covert hacker infrastructure documented by researchers in related domains. In recent years, the "shadow fleet" has been under increasing scrutiny due to its involvement in various clandestine actions, especially in regions close to NATO member countries and areas with sensitive infrastructure.

Russia’s "shadow fleet" operates in the shadows of regular international shipping, often difficult to track due to the use of deceptive practices like turning off automatic identification systems (AIS). This makes it difficult for authorities to monitor their movements and assess their true purpose, raising alarm bells when one of these ships is suspected of being involved in damaging vital infrastructure like undersea cables.

The Cable Damage Incident

The investigation was sparked after damage was discovered to an undersea cable in the Baltic Sea, a vital link for communication, data transmission, and energy supply between Finland and other parts of Europe. These undersea cables are crucial for everything from internet connections to energy grid stability, with recent Nordic grid constraints underscoring their importance, and any disruption to them can have serious consequences.

Finnish authorities reported that the damage appeared to be deliberate, raising suspicions of potential sabotage. The timing of the damage coincides with a period of heightened tensions between Russia and the West, particularly following the escalation of the war in Ukraine, with recent strikes on Ukraine's power grid highlighting the stakes, and ongoing geopolitical instability. This has led many to speculate that the damage to the cables could be part of a broader strategy to undermine European security and disrupt critical infrastructure.

Upon further investigation, a vessel that had been in the vicinity at the time of the damage was identified as potentially being part of Russia’s "shadow fleet." The ship had been operating under a false flag and had disabled its AIS system, making it challenging for authorities to track its movements. The vessel’s activities raised red flags, and Finnish authorities are now working closely with international partners to ascertain its involvement in the incident.

Geopolitical Implications

The damage to undersea cables and the suspected involvement of Russia’s "shadow fleet" have broader geopolitical implications, particularly in the context of Europe’s security landscape. Undersea cables are considered critical infrastructure, akin to electric utilities where intrusions into US control rooms have been documented, and any deliberate attack on them could be seen as an act of war or an attempt to destabilize regional security.

In the wake of the investigation, there has been increased concern about the vulnerability of Europe’s energy and communication networks, which are increasingly reliant on these undersea connections, and as the Baltics pursue grid synchronization with the EU to reduce dependencies, policymakers are reassessing resilience measures. The European Union, alongside NATO, has expressed growing alarm over potential threats to this infrastructure, especially as tensions with Russia continue to escalate.

The incident also highlights the growing risks associated with hybrid warfare tactics, which combine conventional military actions with cyberattacks, including the U.S. condemnation of power grid hacking as a cautionary example, sabotage, and disinformation campaigns. The targeting of undersea cables could be part of a broader strategy by Russia to disrupt Europe’s ability to coordinate and respond effectively, particularly in the context of ongoing sanctions and diplomatic pressure.

Furthermore, the suspected involvement of a "shadow fleet" ship raises questions about the transparency and accountability of maritime activities in the region. The use of vessels operating under false flags or without identification systems complicates efforts to monitor and regulate shipping in international waters. This has led to calls for stronger maritime security measures and greater cooperation between European countries to ensure the safety and integrity of critical infrastructure.

Finland’s Response and Ongoing Investigation

In response to the cable damage incident, Finnish authorities have mobilized a comprehensive investigation, seeking to determine the extent of the damage and whether the actions were deliberate or accidental. The Finnish government has called for increased vigilance and cooperation with international partners to identify and address potential threats to undersea infrastructure, drawing on Symantec's Dragonfly research for insights into hostile capabilities.

Finland, which shares a border with Russia and has been increasingly concerned about its security in the wake of Russia's invasion of Ukraine, has ramped up its defense posture. The damage to undersea cables serves as a stark reminder of the vulnerabilities that come with an interconnected global infrastructure, and Finland’s security services are likely to scrutinize the incident as part of their broader defense strategy.

Additionally, the incident is being closely monitored by NATO and the European Union, both of which have emphasized the importance of safeguarding critical infrastructure. As an EU member and NATO partner, Finland’s response to this situation could influence how Europe addresses similar challenges in the future.

The investigation into the damage to undersea cables in the Baltic Sea, allegedly linked to Russia’s "shadow fleet," has significant implications for European security. The use of covert operations, including the deployment of ships under false flags, underscores the growing threats to vital infrastructure in the region. With tensions between Russia and the West continuing to rise, the potential for future incidents targeting critical communication and energy networks is a pressing concern.

As Finland continues its investigation, the incident highlights the need for greater international cooperation and vigilance in safeguarding undersea cables and other critical infrastructure. In a world where hybrid warfare tactics are becoming increasingly common, ensuring the security of these vital connections will be crucial for maintaining stability in Europe. The outcome of this investigation may serve as a crucial case study in the ongoing efforts to protect infrastructure from emerging and unconventional threats.

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UK Nuclear Energy Ten Point Plan outlines support for large reactors, SMRs, and AMRs, funding Sizewell C, hydrogen production, and industrial heat to reach net zero, decarbonize transport and heating, and expand clean electricity capacity.

Key Points

A UK plan backing large, small, and advanced reactors to drive net zero via clean power, hydrogen, and industrial heat.

✅ Funds large plants (e.g., Sizewell C) under value-for-money models

✅ Invests in SMRs for factory-built, modular, lower-cost deployment

✅ Backs AMRs for high-temperature heat, hydrogen, and industry

The UK government has just announced its “Ten Point Plan for a Green Industrial Revolution”, in which it lays out a vision for the future of energy, transport and nature in the UK. As researchers into nuclear energy, my colleagues and I were pleased to see the plan is rather favourable to new nuclear power.

It follows the advice from the UK’s Nuclear Innovation and Research Advisory Board, pledging to pursue large power plants based on current technology, and following that up with financial support for two further waves of reactor technology (“small” and “advanced” modular reactors).

This support is an important part of the plan to reach net-zero emissions by 2050, as in the years to come nuclear power will be crucial to decarbonising not just the electricity supply but the whole of society.

This chart helps illustrate the extent of the challenge faced:

Electricity generation is only responsible for a small percentage of UK emissions. William Bodel. Data: UK Climate Change Committee

Efforts to reduce emissions have so far only partially decarbonised the electricity generation sector. Reaching net zero will require immense effort to also decarbonise heating, transport, as well as shipping and aviation. The plan proposes investment in hydrogen production and electric vehicles to address these three areas – which will require, as advocates of nuclear beyond electricity argue, a lot more energy generation.

Nuclear is well-placed to provide a proportion of this energy. Reaching net zero will be a huge challenge, and industry leaders warn it may be unachievable without nuclear energy. So here’s what the announcement means for the three “waves” of nuclear power.

Who will pay for it?
But first a word on financing. To understand the strategy, it is important to realise that the reason there has been so little new activity in the UK’s nuclear sector since the 1990s is due to difficulty in financing. Nuclear plants are cheap to fuel and operate and last for a long time. In theory, this offsets the enormous upfront capital cost, and results in competitively priced electricity overall.

But ever since the electricity sector was privatised, governments have been averse to spending public money on power plants. This, combined with resulting higher borrowing costs and cheaper alternatives (gas power), has meant that in practice nuclear has been sidelined for two decades. While climate change offers an opportunity for a revival, these financial concerns remain.

Large nuclear
Hinkley Point C is a large nuclear station currently under construction in Somerset, England. The project is well-advanced, with its first reactor installed and due to come online in the middle of this decade. While the plant will provide around 7% of current UK electricity demand, its agreed electricity price is relatively expensive.

Under construction: Hinkley Point C. Ben Birchall/PA

The government’s new plan states: “We are pursuing large-scale new nuclear projects, subject to value-for-money.” This is likely a reference to the proposed Sizewell C in Suffolk, on which a final decision is expected soon. Sizewell C would be a copy of the Hinkley plant – building follow-up identical reactors achieves capital cost reductions, and setbacks at Hinkley Point C have sharpened delivery focus as an alternative funding model will likely be implemented to reduce financing costs.

Other potential nuclear sites such as Wylfa and Moorside (shelved in 2018 and 2019 respectively for financial reasons) are also not mentioned, their futures presumably also covered by the “subject to value-for-money” clause.

Small nuclear
The next generation of nuclear technology, with various designs under development worldwide are smaller, cheaper, safer Small Modular Reactors (SMRs), such as the Rolls Royce “UK SMR”.

Reactors small enough to be manufactured in factories and delivered as modules can be assembled on site in much shorter times than larger designs, which in contrast are constructed mostly on site. In so doing, the capital costs per unit (and therefore borrowing costs) could be significantly lower than current new-builds.

The plan states “up to £215 million” will be made available for SMRs, Phase 2 of which will begin next year, with anticipated delivery of units around a decade from now.

Advanced nuclear
The third proposed wave of nuclear will be the Advanced Modular Reactors (AMRs). These are truly innovative technologies, with a wide range of benefits over present designs and, like the small reactors, they are modular to keep prices down.

Crucially, advanced reactors operate at much higher temperatures – some promise in excess of 750°C compared to around 300°C in current reactors. This is important as that heat can be used in industrial processes which require high temperatures, such as ceramics, which they currently get through electrical heating or by directly burning fossil fuels. If those ceramics factories could instead use heat from AMRs placed nearby, it would reduce CO₂ emissions from industry (see chart above).

High temperatures can also be used to generate hydrogen, which the government’s plan recognises has the potential to replace natural gas in heating and eventually also in pioneering zero-emission vehicles, ships and aircraft. Most hydrogen is produced from natural gas, with the downside of generating CO₂ in the process. A carbon-free alternative involves splitting water using electricity (electrolysis), though this is rather inefficient. More efficient methods which require high temperatures are yet to achieve commercialisation, however if realised, this would make high temperature nuclear particularly useful.

The government is committing “up to £170 million” for AMR research, and specifies a target for a demonstrator plant by the early 2030s. The most promising candidate is likely a High Temperature Gas-cooled Reactor which is possible, if ambitious, over this timescale. The Chinese currently lead the way with this technology, and their version of this reactor concept is expected soon.

In summary, the plan is welcome news for the nuclear sector, even as Europe loses nuclear capacity across the continent. While it lacks some specifics, these may be detailed in the government’s upcoming Energy White Paper. The advice to government has been acknowledged, and the sums of money mentioned throughout are significant enough to really get started on the necessary research and development.

Achieving net zero is a vast undertaking, and recognising that nuclear can make a substantial contribution if properly supported is an important step towards hitting that target.

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Nova Scotia Power Rate Increase Settlement faces UARB scrutiny as regulators weigh electricity rates, fuel costs, storm rider provisions, Bill 212 limits, and Muskrat Falls impacts on ratepayers and affordability for residential and industrial customers.

Key Points

A deal proposing 13.8% electricity hikes for 2023-2024, before the UARB, covering fuel costs, a storm rider, and Bill 212.

✅ UARB review may set different rates than the settlement

✅ Fuel cost prepayment and hedging incentives questioned

✅ Storm rider shifts climate risk onto ratepayers

Nova Scotia Premier Tim Houston is calling on provincial regulators to reject a settlement agreement between Nova Scotia Power and customer groups that would see electricity rates rise by nearly 14% electricity rate hike over the next two years.

"It is our shared responsibility to protect ratepayers and I can't state strongly enough how concerned I am that the agreement before you does not do that," Houston wrote in a letter to the Nova Scotia Utility and Review Board late Monday.

Houston urged the three-member panel to "set the agreement aside and reach its own conclusion on the aforementioned application."

"I do not believe, based on what I know, that the proposed agreement is in the best interest of ratepayers," he said.

The letter does not spell out what his Progressive Conservative government would do if the board accepts the settlement reached last week between Nova Scotia Power and lawyers representing residential, small business and large industrial customer classes.

Other groups also endorsed the deal, although Nova Scotia Power's biggest customer — Port Hawkesbury Paper — did not sign on.

'We're protecting the ratepayers'
Natural Resources Minister Tory Rushton said the province was not part of the negotiations leading up to the settlement.

"As a government or department we had no intel on those conversations that were taking place," he said Tuesday. "So, we saw the information the same as the public did late last week, and right now we're protecting the ratepayers of Nova Scotia, even though the province cannot order Nova Scotia Power to lower rates under current law. We want to make sure that that voice is still heard at the UARB level."

Rushton said he didn't want to presuppose what the UARB will say.

"But I think the premier's been very loud and clear and I believe I have been, too. The ratepayers are at the top of our mind. We have different tools at our [disposal] and we'll certainly do what we can and need to [do] to protect those ratepayers."

The settlement agreement
If approved by regulators, rates would rise by 6.9 per cent in 2023 and 6.9 per cent in 2024 — almost the same amount on the table when hearings before the review board ended in September.

The Houston government later intervened with legislation, known as Bill 212, that capped rates to cover non-fuel costs by 1.8 per cent. It did not cap rates to cover fuel costs or energy efficiency programs.

In a statement announcing the agreement, Nova Scotia Power president Peter Gregg claimed the settlement adhered "to the direction provided by the provincial government through Bill 212."

Consumer advocate Bill Mahody, representing residential customers, told CBC News the proposed 13.8 per cent increase was "a reasonable rate increase given the revenue requirement that was testified to at the hearing."

Settlement 'remarkably' similar to NSP application
The premier disagrees, noting that the settlement and rate application that triggered the rate cap are "remarkably consistent."

He objects to the increased amount of fuel costs rolled into rates next year before the annual true up of actual fuel costs, which are automatically passed on to ratepayers.

"If Nova Scotia Power is effectively paid in advance, what motive do they have to hedge and mitigate the adjustment eventually required," Houston asked in his letter.

He also objected to the inclusion of a storm rider in rates to cover extreme weather, which he said pushed the risk of climate change on to ratepayers.

Premier second-guesses Muskrat Falls approval
Houston also second-guessed the board for approving Nova Scotia Power's participation in the Muskrat Falls hydro project in Labrador.

"The fact that Nova Scotians have paid over $500 million for this project with minimal benefit, and no one has been held accountable, is wrong," he said. "It was this board of the day that approved the contracts and entered the final project into rates."

Ratepayers are committed to paying $1.7 billion for the Maritime Link to bring the green source of electricity into the province, while rate mitigation talks in Newfoundland lack public details for their customers.

Although the Maritime Link was built on time and on budget by an affiliated company, only a fraction of Muskrat Falls hydro has been delivered because of ongoing problems in Newfoundland, including an 18% electricity rate hike deemed unacceptable by the province's consumer advocate.

"I find it remarkable that those contracts did not include different risk sharing mechanisms; they should have had provisions for issues in oversight of project management. Nevertheless, it was approved, and is causing significant harm to ratepayers in the form of increased rates."

Houston notes that because of non-delivery from Muskrat Falls, Nova Scotia Power has been forced to buy much more expensive coal to burn to generate electricity.

Opposition reaction
Opposition parties in Nova Scotia reacted to Houston's letter.

NDP Leader Claudia Chender dismissed it as bluster.

"It exposes his Bill 212 as not really helping Nova Scotians in the way that he said it would," she said. "Nothing in the settlement agreement contravenes that bill. But it seems that he's upset that he's been found out. And so here we are with another intervention in an independent regulatory body."

Liberal Leader Zach Churchill said the government should intervene to help ratepayers directly.

"We just think that it makes more sense to do that directly by supporting ratepayers through heating assistance, lump-sum electricity credits, rebate programs and expanding the eligibility for that or to provide funding directly to ratepayers instead of intervening in the energy market in this way," he said.

The premier's office said that no one was available when asked about an interview on Tuesday.

"The letter speaks for itself," the office responded.

Nova Scotia Power issued a statement Tuesday. It did not directly address Houston's claims.

"The settlement agreement is now with the NS Utility and Review Board," the utility said.

"The UARB process is designed to ensure customers are represented with strong advocates and independent oversight. The UARB will determine whether the settlement results in just and reasonable rates and is in the public interest."

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Geothermal Power Plant Risks include hydrogen sulfide leaks, toxic gases, lava flow hazards, well blowouts, and earthquake-induced releases at sites like PGV and the Geysers, threatening public health, grid reliability, and environmental safety.

Key Points

Geothermal Power Plant Risks include toxic gases, lava impacts, well failures, and induced quakes that threaten health.

✅ Hydrogen sulfide exposure can cause rapid pulmonary edema.

✅ Lava can breach wells, venting toxic gases into communities.

✅ Induced seismicity may disrupt grids near PGV and the Geysers.

If lava reaches Hawaii’s PGV geothermal power plant, it could release of deadly hydrogen sulfide gas. That’s the latest potential danger from the Kilauea volcanic eruption in Hawaii. Residents now fear that lava flow will trigger a meltdown at the Puna Geothermal Venture (PGV) power plant that would release even more toxic gases into the air.

Nobody knows what will happen if lava engulfs the PGV because magma has never engulfed a geothermal power plant, Reuters reported. A geothermal power plant uses steam and gas heated by lava deep in the earth to run turbines that make electricity.

The PGV power plant produces 25% of the power used on Hawaii’s “Big Island.” The plant is considered a source of clean energy because geothermal plants burn no fossil fuels and produce little pollution under normal circumstances, even as nuclear retirements like Three Mile Island reshape low-carbon options.

The Potential Danger from Geothermal Energy

The fear is that the lava would release chemicals used to make electricity at the plant. The PGV has been shut down and authorities moved an estimated 60,000 gallons of flammable liquids away from the facility. They also shut down wells that extract steam and gas used to run the turbines.

Another potential danger is that lava would open the wells and release clouds of toxic gases from them. The wells are typically sealed to prevent the gas from entering the atmosphere.

The most significant threat is hydrogen sulfide, a highly toxic and flammable gas that is colorless. Hydrogen sulfide normally has a rotten egg smell which people might not detect when the air is full of smoke. That means people can breathe hydrogen sulfide in without realizing they have been exposed.

The greatest danger from hydrogen sulfide is pulmonary edema; the accumulation of fluid in the lungs, which causes a person to stop breathing. People have died of pulmonary edema after just a few minutes of exposure to hydrogen sulfide gas. Many victims become unconscious before the gas kills them. Long-term dangers that survivors of pulmonary edema face include brain damage.

Hydrogen sulfide can also cause burns to the skin that are similar to frostbite. Persons exposed to hydrogen sulfide can also suffer from nausea, headaches, severe eye burns, and delirium. Children are more vulnerable to hydrogen sulfide because it is a heavy gas that stays close to the ground.

Geothermal Danger Extends Far Beyond Hawaii

The danger from geothermal energy extends far beyond Hawaii. The world’s largest collection of geothermal power plants is located at the Geysers in California’s Wine Country, and regulatory timelines such as the postponed closure of three Southern California plants can affect planning.

The Geysers field contains 350 steam production wells and 22 power plants in Sonoma, Lake, and Mendocino counties. Disturbingly, the Geysers are located just north of the heavily-populated San Francisco Bay Area and just west of Sacramento, where preemptive electricity shutdowns have been used during extreme fire weather. Problems at the Geysers might lead to significant blackouts because the field supplies around 20% of the green energy used in California.

Another danger from geothermal power is earthquakes because many geothermal power plants inject wastewater into hot rock deep below to produce steam to run turbines, a factor under review as SaskPower explores geothermal in new settings. A geothermal project in Switzerland created Earthquakes by injecting water into the Earth, Zero Hedge reported. A theoretical threat is that quakes caused by injection would cause the release of deadly gases at a geothermal power plant.

The dangers from geothermal power might be much greater than its advocates admit, potentially increasing reliance on natural-gas-based electricity during supply shortfalls.

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UK Hydrogen Storage Caverns enable long-duration, low-carbon electricity balancing, storing surplus wind and solar power as green hydrogen in salt formations to enhance grid reliability, energy security, and net zero resilience by 2035 and 2050.

Key Points

They are salt caverns storing green hydrogen to balance wind and solar, stabilizing a low-carbon UK grid.

✅ Stores surplus wind and solar as green hydrogen in salt caverns

✅ Enables long-duration, low-carbon grid balancing and security

✅ Complements wind and solar; reduces dependence on flexible CCS

The U.K. government must kick-start the construction of large-scale hydrogen storage facilities if it is to meet its pledge that all electricity will come from low-carbon electricity sources by 2035 and reach legally binding net zero targets by 2050, according to a report by the Royal Society.

The report, "Large-scale electricity storage," published Sep. 8, examines a wide variety of ways to store surplus wind and solar generated electricity—including green hydrogen, advanced compressed air energy storage (ACAES), ammonia, and heat—which will be needed when Great Britain's electricity generation is dominated by volatile wind and solar power.

It concludes that large scale electricity storage is essential to mitigate variations in wind and sunshine, particularly long-term variations in the wind, and to keep the nation's lights on. Storing most of the surplus as hydrogen, in salt caverns, would be the cheapest way of doing this.

The report, based on 37 years of weather data, finds that in 2050 up to 100 Terawatt-hours (TWh) of storage will be needed, which would have to be capable of meeting around a quarter of the U.K.'s current annual electricity demand. This would be equivalent to more than 5,000 Dinorwig pumped hydroelectric dams. Storage on this scale, which would require up to 90 clusters of 10 caverns, is not possible with batteries or pumped hydro.

Storage requirements on this scale are not currently foreseen by the government, and the U.K.'s energy transition faces supply delays. Work on constructing these caverns should begin immediately if the government is to have any chance of meeting its net zero targets, the report states.

Sir Chris Llewellyn Smith FRS, lead author of the report, said, "The need for long-term storage has been seriously underestimated. Demand for electricity is expected to double by 2050 with the electrification of heat, transport, and industrial processing, as well as increases in the use of air conditioning, economic growth, and changes in population.

"It will mainly be met by wind and solar generation. They are the cheapest forms of low-carbon electricity generation, but are volatile—wind varies on a decadal timescale, so will have to be complemented by large scale supply from energy storage or other sources."

The only other large-scale low-carbon sources are nuclear power, gas with carbon capture and storage (CCS), and bioenergy without or with CCS (BECCS). While nuclear and gas with CCS are expected to play a role, they are expensive, especially if operated flexibly.

Sir Peter Bruce, vice president of the Royal Society, said, "Ensuring our future electricity supply remains reliable and resilient will be crucial for our future prosperity and well-being. An electricity system with significant wind and solar generation is likely to offer the lowest cost electricity but it is essential to have large-scale energy stores that can be accessed quickly to ensure Great Britain's energy security and sovereignty."

Combining hydrogen with ACAES, or other forms of storage that are more efficient than hydrogen, could lower the average cost of electricity overall, and would lower the required level of wind power and solar supply.

There are currently three hydrogen storage caverns in the U.K., which have been in use since 1972, and the British Geological Survey has identified the geology for ample storage capacity in Cheshire, Wessex and East Yorkshire. Appropriate, novel business models and market structures will be needed to encourage construction of the large number of additional caverns that will be needed, the report says.

Sir Chris observes that, although nuclear, hydro and other sources are likely to play a role, Britain could in principle be powered solely by wind power and solar, supported by hydrogen, and some small-scale storage provided, for example, by batteries, that can respond rapidly and to stabilize the grid. While the cost of electricity would be higher than in the last decade, we anticipate it would be much lower than in 2022, he adds.

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