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Northeast Passage

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Northeast_Passage

The Northeast Passage (abbreviated as NEP; Russian: Северо-Восточный проход, romanized: Severo-Vostochnyy prokhod, Norwegian: Nordøstpassasjen) is the shipping route between the Atlantic and Pacific Oceans, along the Arctic coasts of Norway and Russia. The western route through the islands of Canada is accordingly called the Northwest Passage (NWP).

The NEP traverses (from west to east) the Barents Sea, Kara Sea, Laptev Sea, East Siberian Sea, and Chukchi Sea, and it includes the Northern Sea Route (NSR). The Northern Sea Route is a portion of the NEP. It is defined in Russian law and does not include the Barents Sea and therefore does not reach the Atlantic Ocean. However, since the NSR has a significant overlap over the majority of the NEP, the NSR term is often used to refer to the entirety of the Northeast Passage. This practice injects confusion in understanding the specifics of both navigational procedures and jurisdiction.

The Northeast Passage is one of several Arctic maritime routes, the others being the Northwest Passage (going through the Canadian Arctic Archipelago and the coast of Alaska) and the Transpolar Route (going across the North Pole).

The first confirmed complete passage, from west to east, was made by the Finland-Swedish explorer Adolf Erik Nordenskiöld, with the Swedish ship Vega 1878–79 backed by the royal funding of king Oscar II of Sweden. Nordenskiöld was forced to winter just a few days' sailing distance from the Bering Strait, due to pack ice.

History

11th to 17th centuries

The motivation to navigate the Northeast passage was initially economic. In Russia, the idea of a possible seaway connecting the Atlantic and the Pacific Oceans was first proposed by the diplomat Gerasimov in 1525. However, Russian settlers and traders on the coast of the White Sea, the Pomors, had been exploring parts of the route as early as the 11th century. Grigory Istoma wrote about his 1496 voyage along the passage, which was later published by Sigismund von Herberstein and influenced the planning of future expeditions.

During a sail across the Barents Sea in search of the Northeast Passage in 1553, English explorer Hugh Willoughby thought he saw islands to the north, and islands called Willoughby's Land were shown on maps published by Plancius and Mercator in the 1590s, and they continued to appear on maps by Jan Janssonius and Willem Blaeu into the 1640s.

By the 17th century, traders had established a continuous sea route from Arkhangelsk to the Yamal Peninsula, where they portaged to the Gulf of Ob. This route, known as the Mangazeya seaway, after its eastern terminus, the trade depot of Mangazeya, was an early precursor to the Northern Sea Route.

East of the Yamal, the route north of the Taimyr Peninsula proved impossible or impractical. East of the Taimyr, from the 1630s, Russians began to sail the Arctic coast from the mouth of the Lena River to a point beyond the mouth of the Kolyma River. Both Vitus Bering (in 1728) and James Cook (in 1778) entered the Bering Strait from the south and sailed some distance northwest, but from 1648 (Semyon Dezhnev) to 1879 (Adolf Erik Nordenskiöld) no one is recorded as having sailed eastward between the Kolyma and Bering Strait.

The western parts of the passage were explored by northern European countries such as England, the Netherlands, Denmark, and Norway, looking for an alternative seaway to China and India; had it proved practicable, such a seaway would have had enormous economic and military importance. Although these expeditions failed, new coasts and islands were discovered. The most notable was the 1596 expedition led by Dutch navigator Willem Barentsz, who discovered Spitsbergen and Bear Island, and rounded the north end of Novaya Zemlya.

Fearing English and Dutch penetration into Siberia, Russia closed the Mangazeya seaway in 1619. Pomor activity in Northern Asia declined and most Arctic exploration in the 17th century was carried out by Siberian Cossacks, sailing from one river mouth to another in their Arctic-worthy kochs. In 1648, the most famous of these expeditions, led by Fedot Alekseev and Semyon Dezhnev, sailed east from the mouth of the Kolyma River to the Pacific Ocean, and rounded the Chukchi Peninsula, thus proving that no land connection existed between Asia and North America.

18th and 19th centuries

Eighty years after Dezhnev, in 1728, another Russian explorer, Danish-born Vitus Bering on Svyatoy Gavriil (Saint Gabriel) made a similar voyage in reverse, starting in Kamchatka and going north to the passage that now bears his name; the Bering Strait. It was Bering who named the Diomede Islands, which Dezhnev had vaguely mentioned.

Bering's explorations of 1725–30 were part of a larger scheme of Peter the Great, known as the Great Northern Expedition.

The Second Kamchatka Expedition took place in 1735–42, with two ships, Svyatoy Pyotr (Saint Peter) and Svyatoy Pavel (Saint Paul), the latter commanded by Bering's deputy in the first expedition, Captain Aleksey Chirikov. During the Second Expedition Bering became the first Westerner to sight the coast of northwestern North America, and Chirikov was the first Westerner to land there (a storm had separated the two ships earlier). On his return leg, Bering discovered the Aleutian Islands but fell ill, and Svyatoy Pyotr had to take shelter on an island off Kamchatka, where Bering died (Bering Island).

Independent of Bering and Chirikov, other Russian Imperial Navy parties took part in the Second Great Northern Expedition. One of these, led by Semyon Chelyuskin, in May 1742 reached Cape Chelyuskin, the northernmost point of both the Northeast Passage and the Eurasian continent.

Later expeditions to explore the Northeast Passage took place in the 1760s (Vasiliy Chichagov), 1785–95 (Joseph Billings and Gavril Sarychev), the 1820s and 1830s (Baron Ferdinand Petrovich Wrangel, Pyotr Fyodorovich Anjou, Count Fyodor Litke and others). The possibility of navigating the length of the passage was proven by the mid-19th century.

However, it was only in 1878-79 that Fenno-Swedish explorer Adolf Erik Nordenskiöld (born in Finland but exiled to Sweden many years before the expedition) made the first complete passage of the Northeast Passage, leading the Vega expedition from west to east. The ship's captain on this expedition was Lieutenant Louis Palander of the Swedish Royal Navy.

One year before Nordenskiöld's voyage, commercial exploitation of a section of the route started with the so-called Kara expeditions, exporting Siberian agricultural produce via the Kara Sea. Of 122 convoys between 1877 and 1919 only 75 succeeded, transporting as little as 55 tons of cargo. From 1911 the Kolyma River steamboats ran from Vladivostok to the Kolyma once a year.

In 1912, two Russian expeditions set out; Captain Georgy Brusilov and the Brusilov Expedition in the Santa Anna, and Captain Alexander Kuchin with Vladimir Rusanov in the Gerkules (Hercules); each with a woman on board. Both expeditions were hastily arranged, and both disappeared. The German Arctic Expedition of 1912, led by Herbert Schröder-Stranz, ended disastrously with only 7 of 15 crew members surviving the preliminary expedition to Nordaustlandet.

In 1913 Jonas Lied organized a successful expedition through the Kara Sea to the Yenisei. Explorer and scientist Fridtjof Nansen and Siberian industrialist Stephan Vostrotin were prominent passengers. Lied had founded The Siberian company with the purpose of exporting and importing goods through the great Siberian rivers and the Kara Sea. The 1913 trip is recorded in Nansen's Through Siberia.

In 1915, a Russian expedition led by Boris Vilkitskiy made the passage from east to west with the icebreakers Taymyr and Vaygach.

Nordenskiöld, Nansen, Amundsen, DeLong, Makarov and others also led expeditions, mainly for scientific and cartographic purposes.

After the Russian Revolution

The introduction of radio, steamboats, and icebreakers made running the Northern Sea Route viable. After the Russian Revolution of 1917, the Soviet Union was isolated from the western powers, which made it imperative to use this route. Besides being the shortest seaway between the western and far eastern USSR, it was the only one that lay completely inside Soviet internal waters and did not impinge on waters of opposing countries.

In 1932, a Soviet expedition on the icebreaker A. Sibiryakov led by Professor Otto Yulievich Schmidt was the first to sail all the way from Arkhangelsk to the Bering Strait in the same summer without wintering en route. After trial runs in 1933 and 1934, the Northern Sea Route was officially defined and open and commercial exploitation began in 1935. The next year, part of the Baltic Fleet made the passage to the Pacific where armed conflict with Japan was looming.

A special governing body Glavsevmorput (Chief Directorate of the Northern Sea Route) was set up in 1932, with Otto Schmidt as its director. It supervised navigation and built Arctic ports.

During the early part of World War II, the Soviets allowed the German auxiliary cruiser Komet to use the Northern Sea Route in the summer of 1940 to evade the British Royal Navy and break out into the Pacific Ocean. Komet was escorted by Soviet icebreakers during her journey. After the start of the Soviet-German War, the Soviets transferred several destroyers from the Pacific Fleet to the Northern Fleet via the Arctic. The Soviets also used the Northern Sea Route to transfer materials from the Soviet Far East to European Russia, and the Germans launched Operation Wunderland to interdict this traffic.

A convoy of seven brand-new merchant vessels (900 DWT to 5500 DWT) built for the People's Republic of China but sailing under the Polish flag from Gdynia, reached the port of Pevek (via the Kara, Vilkitsky, Dmitry Laptev and Sannikov Straits), two days of navigation before the Bering Strait in 1956.

In July 1965, USCGC Northwind (WAGB-282), commanded by Captain Kingdrel N. Ayers USCG, conducted an oceanographic survey between Greenland, Iceland, and Scotland and was the first western vessel to operate in the Kara Sea of the Soviet Union, for which she received the Coast Guard Unit Commendation with Operational Distinguishing Device. The real (then-classified) mission of Northwind was to attempt a transit of the "Northeast Passage". The effort was not successful due to diplomatic reasons and caused an international incident between the U.S.S.R. and U.S.A.

After the Soviet Union

After the Soviet Union dissolved in the early 1990s, commercial navigation in the Siberian Arctic went into decline. Regular shipping is found only from Murmansk to Dudinka in the west and between Vladivostok and Pevek in the east. Ports between Dudinka and Pevek see virtually no shipping. Logashkino and Nordvik were abandoned and are now ghost towns.

Renewed interest led to several demonstration voyages in 1997 including the passage of the Finnish product tanker Uikku.

A January 2013 Reuters News report on expanding Russian arctic natural gas shipments to Asia, stated that while shipping traffic on the NSR surged in 2012 to around 1 million tons of various kinds of cargoes, "it pales by comparison with the 1987 peak of 6.6 million tons." It also reported that the Finnish crude oil tanker Uikku was the first non-Russian energy vessel to brave the NSR in 1997.

Now the NSR is developing rapidly. In 2021 85 ships with around 2.75m tons of cargo made their way along the NSR, only 12 of which were under the Russian flag.

Northern Sea Route

A similar route to the NEP is the Northern Sea Route (NSR). The NSR is a shipping route that administratively begins at the boundary between the Barents and Kara Seas (the Kara Strait) and ends in the Bering Strait (Cape Dezhnev). The length of the Northern Sea Route from the Kara Gates to Provideniya Bay is about 5600 km. The distance from St. Petersburg to Vladivostok through the NSR is over 14 thousand km (for comparison, the same distance through the Suez Canal is over 23 thousand km). The Northern Sea Route serves the Arctic ports and major rivers of Siberia by importing fuel, equipment, food and exporting timber and minerals. The Suez or Panama Canal are the alternatives to the Northern Sea Route. However, if the distance from the port of Murmansk (Russia) to the port of Yokohama (Japan) through the Suez Canal is 12,840 nautical miles, the same itinerary along the Northern Sea Route equals only 5,770 nautical miles.

Therefore, the NEP encompasses all the East Arctic seas, and the NSR all the seas except the Barents Sea. Since the NSR constitutes the majority of the NEP, sometimes the term NSR has been used to refer to the entirety of the NEP.

Governance

The governance of the NEP has developed considerably in the late 20th and early 21st centuries. The main sources of governance are the United Nations Convention on the Law of the Sea (UNCLOS), the Arctic Council (AC), the International Maritime Organization (IMO), and the domestic legislation of the Russian Federation. In combination, they cover territorial claims, economic exploitation, technical shipping requirements, environmental protection, and search and rescue responsibilities.

For example, Rosatom assumes the possibility and functions of the NSR. Rosatom is a state corporation that organizes the navigation of vessels in the waters of the NSR in accordance with the Merchant Shipping Code, manages a fleet of powerful nuclear icebreakers, ensures the safety and uninterrupted operation of navigation, provides port services for gas tankers in case of unfavorable weather conditions. Rosatom also provides navigation and hydrographic support in the waters of the Northern Sea Route, develops the infrastructure of sea harbors, and manages the state property of these ports. For this purpose, the Directorate of the Northern Sea Route was formed, that now manages three subordinate organizations "Atomflot" (ROSATOMFLOT), "Hydrographic Enterprise" and "ChukotAtomEnergo".

Recently, the "Main Directorate of the Northern Sea Route" ("Glavsevmorput") was established on the basis of the Naval Operations Headquarters of FSUE “Atomflot”. The main purpose of the creation of the Glavsevmorput is to organize the navigation of vessels in the waters of the Northern Sea Route. Glavsevmorput Federal State Budgetary Institution solves the following tasks: ensuring the organization of icebreaking vessels taking into account the hydrometeorological, ice, and navigation conditions in the waters of the NSR; vessels navigation in the waters of the NSR; issuance, suspension, renewal, and termination of permits for sailing vessels in the waters of the NSR. To solve these tasks, the department arranges icebreaker fleet vessels in the waters of the NSR, monitors the traffic in the NSR water area, provides information on hydrometeorological, ice, and navigation conditions, and processes information from vessels located in the NSR water area. Rosatom is a Legacy Member of the Arctic Economic Council, that’s why all the operations are aimed to establish economic well-being, environmental neutrality, and human capital development.

Pacific-Atlantic distances

The Northeast Passage is a shorter route to connect Northeast Asia with Western Europe, compared to the existing routes through the Suez Canal, the Panama Canal, or around the Cape of Good Hope. The table below shows the sailing distances between the major East Asia sea ports, and Rotterdam in Europe (these distances assume no route diversions owing to ice conditions).

Sailing distances between Asia and Europe through the NEP (in nautical miles)
	To Rotterdam, via:
From	Cape of Good Hope	Suez Canal	NEP	Difference between Suez and NEP
Yokohama, Japan	14,448	11,133	7,010	37%
Busan, South Korea	14,084	10,744	7,667	29%
Shanghai, China	13,796	10,557	8,046	24%
Hong Kong, China	13,014	9,701	8,594	11%
Ho Chi Minh City, Vietnam	12,258	8,887	9,428	−6%

Commercial value

A usable Northern Sea Route between northern Europe and North Pacific ports would cut time at sea (and resultant fuel consumption) by more than half. For the corporate players in bulk shipping of relative low-value raw materials, cost savings for fuel may appear as a driver to explore the Northern Sea Route for commercial transits, and not necessarily reduced lead time. The Northern Sea Route allows economies of scale compared to coastal route alternatives, with vessel draught and beam limitation. Environmental demands faced by the maritime shipping industry may emerge as a driver for developing the Northern Sea Route. Increased awareness of environmental benefits and costs for both the Northern Sea Route and Suez routes will probably be important factors in this respect.

In 2011, four ships sailed the length of the Northern Sea Route and Northeast Passage, from the Atlantic to Pacific Oceans. In 2012, 46 ships sailed the NSR.

In August 2012, Russian media reported that 85% of vessels transiting the Northern Sea Route in 2011 were carrying gas or oil, and 80% were high-capacity tankers.

As the Northern Sea Route is a strategically important transport artery, it can already be called economically profitable in comparison, for example, with the Suez Canal due to a number of reasons:

Fuel savings due to reduced distance;
The shorter distance reduces the cost of staff labor and chartering vessels;
The Northern Sea Route does not charge payments for the passage (unlike, for example, the Suez Canal);
There are no queues (unlike, for example, the Suez Canal);
There is no risk of a pirate attack.

Environmental concerns

In September 2012, Inuit Circumpolar Conference Chair Jimmy Stotts was reported as saying there is concern that increased shipping could adversely affect indigenous hunting of marine mammals. Also concerning is the lack of infrastructure on the Western Alaska coast to deal with a spill or a wrecked vessel.

However, a polar opinion also does exist. The Northern Sea route is considerably shorter than the existing sea routes from Asia to Europe, which makes it more ecological due to less consumption of CO₂. A usable Northern Sea Route between northern Europe and North Pacific ports would cut time at sea (and, accordingly, fuel consumption) by more than half. For the corporate players in bulk shipping of relative low-value raw materials, cost savings for fuel may appear as a driver to explore the Northern Sea Route for commercial transits, and not necessarily reduced lead time. The Northern Sea Route allows economies of scale compared to coastal route alternatives, with vessel draught and beam limitation. Environmental demands faced by the maritime shipping industry may emerge as a driver for developing the Northern Sea Route. With the NSR each year becoming more navigable for commercial shipping nations such as China may be inclined to change their traditional shipping routes from the Suez Cannel to the NSR. This could triple or even quadruple the NSR's shipping tonnage.

According to the Fourth IMO GHG Study 2020, sea cargo transportation is responsible for 2.9% of global emissions. More than that, in the next 20 years the trading maritime volume is expected to double, which may cause even worse consequences for the environment. Now marine transport produces about 1 gigaton of carbon dioxide (CO₂) emissions per year and has been struggling for many years to reduce its environmental impact. For example, the International Maritime Organization (IMO) has obliged sea carriers to reduce CO₂ emissions by 50% by 2050. It may seem very realistic, but achieving this result may become a tough challenge. Firstly, marine transport generates 14% of all transport emissions, and, secondly, effective techniques that could replace marine engines powered by fossil fuels do not exist yet. Due to its shorter length, navigation on the NSR contributes to reducing the carbon footprint of maritime transport thus contributing to the achievement of the Paris Agreement goals.

Ice conditions

Unlike the similar latitudes in Alaska and Canada (along the Northwest Passage), parts of the NEP remain ice-free year-round. This is mostly the case of the Barents Sea, by the northern coast of Norway and Northwestern coast of Russia. The Barents sea is affected by the currents of warm water from the Gulf Stream, feeding into the North Atlantic.

Other parts of the NEP (mostly the NSR part), freeze in winter and partially melt in the summer months, especially along the coasts. Since the early 2000s the summer melting has been stronger, and the winter freezing has been weaker, opening the waters to the possibility of more non-ice breaking ships taking advantage of the route for longer periods of time.

Ice-free ports

Only one Russian seaport in the Barents Sea along the officially defined Northern Sea Route (which begins at the Kara Gates Strait) is ice-free year-round, Murmansk on the Kola Peninsula. Other Arctic ports are generally usable from July to October, or, such as Dudinka, are served by nuclear-powered icebreakers. Beyond the Bering Strait, the end of the Northern Sea Route, and south along Russia's Pacific seaboard Petropavlovsk in Kamchatka, Vanino, Nakhodka, and Vladivostok are accessible year-round.

The development of the icebreaking fleet is the most important condition for constant navigation in Arctic waters. Since 2008, the structure of Rosatom includes the Russian nuclear icebreaker fleet, which is the largest in the world with a container ship, four service vessels and seven nuclear-powered icebreakers (“Yamal”, "50 Let Pobedy", "Taymyr", "Vaygach", "Arctic", "Siberia" and Ural). The last three are the latest universal icebreakers of the 22220 project, and the world's only transport vessel with the Sevmorput nuclear power plant in operation.

Transit shipping activity

Due to its harsh climatic conditions and the low population density, the NEP has had relatively little activity. The NSR portion of the NEP experienced its highest levels of activity during the Soviet era. The NSR greatly developed as a heavily subsidized domestic route, with traffic peaking in 1987 with 6.58 million tons of cargo carried by 331 ships over 1306 voyages. With the end of the Soviet Union and its subsidies, the NSR traffic collapsed to 1.5–2 M tons of cargo.

Since the early 2000s, the thickness and area extent of the Arctic sea ice has experienced significant reduction, compared to the recorded averages. This has led to an increase in transit shipping. In 2011, four ships sailed the entire length of the NEP, 46 in 2012, and 19 in 2013. The number of trips is still very small compared to the thousands of ships each year through the Suez Canal. Mainstream container shipping is expected to continue to overwhelmingly use the Suez route, while niche activities like bulk shipping is expected to grow, driven by the mining industries of the Arctic.

Nevertheless, the cargo traffic is steadily growing every year. The research shows that the NSR-SCR combined shipping scheme can be more competitive than the use of the Suez Canal Route only. If the shipping company provides sufficient loading on the NSR, uses a reliable ice-class vessel for navigation and the price of crude oil is high, the economic advantage of the NSR-SCR combined shipping scheme is obvious. Ice thickness directly affects the shipping cost. Now, when the Arctic ice is slowly melting due to weather conditions, the cost of icebreaking service is expected to reduce. Also, vessels of some ice classes can sail on the NSR independently. That is why the NSR icebreaker escort fee may be several times lower than the SCR toll.

State Corporation Rosatom assumes the possibility and functions of the NSR and ensures the safety of navigation on the high technological level. Besides organizing the navigation along the NSR and the icebreaking services with the world's only nuclear icebreaker fleet, Rosatom is planning to implement the Arctic Ice Regime Shipping System (AIRSS) methodology. This system will represent a digital space that will provide various services to cargo carriers, shipowners, captains, insurers, and other participants in the logistics market on the NSR. In particular, it involves issuing permits for the passage of vessels, monitoring, dispatching, and managing the work of the fleet. The single digital platform will collect information from all the available sources, for example, hydrometeorological data, the location of ships and icebreakers, port congestion. As a result, users will receive an advanced "ice navigator" that will allow to plot a precise route in view of the changing ice conditions of the NSR. In other words, the study of Sibul et al. proposed a path-finding algorithm for the NSR strategic assessment. It uses real weather as input and find the optimal shipping route.

Ice-free navigation

The term "ice free" generally refers to the absence of fast ice, i.e. continuously frozen surface ice sheet cover. Under common usage "ice free" does not mean that there is no Arctic sea ice. "Ice free" regions can contain broken ice cover of varying density, often still requiring appropriately strengthened hulls or icebreaker support for safe passage.

French sailor Eric Brossier made the first passage by sailboat in only one season in the summer of 2002. He returned to Europe the following summer through the Northwest Passage.

The same year Arved Fuchs and its crew sailed the Northeast Passage with the Dagmar Aaen.

The Northern Sea Route was opened by receding ice in 2005 but was closed by 2007. The amount of polar ice had receded to 2005 levels in August 2008. In late August 2008, it was reported that images from the NASA Aqua satellite had revealed that the last ice blockage of the Northern Sea Route in the Laptev Sea had melted. This would have been the first time since satellite records began that both the Northwest Passage and Northern Sea Route had been open simultaneously. However, other scientists suggested that the satellite images may have been misread and that the sea route was not yet passable.

In 2009, the Bremen-based Beluga Group claimed they were the first Western company to attempt to cross the Northern Sea Route for shipping without assistance from icebreakers, cutting 4000 nautical miles off the journey between Ulsan, Korea and Rotterdam. The voyage was widely covered and sometimes incorrectly said to be the first time that non-Russian ships made the transit. In 1997, a Finnish oil tanker, Uikku, sailed the length of the Northern Sea Route from Murmansk to the Bering Strait, becoming the first Western ship to complete the voyage.

However, the new (2008) ice-strengthened heavy lift vessels Beluga Fraternity and Beluga Foresight commenced an East-to-West passage of the Northern Sea Route in August 2009 as part of a small convoy escorted by the Russian nuclear icebreaker NS 50 Let Pobedy, westward through the Bering, Sannikov, and Vilkitskiy Straits. The two vessels embarked Russian ice pilots for the voyage to the western Siberian port of Novyy, in the Yamburg region in the delta of the Ob River. The ships arrived at Novyy on 7 September, discharged their cargo to barges and departed on 12 September, bound for the Kara Gates and Rotterdam. They were the first non-Russian commercial vessels to complete this journey, but not without Russian assistance. The captain of the Beluga Foresight, Valeriy Durov, described the achievement as "...great news for our industry." The president of Beluga Shipping claimed the voyage saved each vessel about 300,000 euros, compared to the normal Korea-to-Rotterdam route by way of the Suez Canal. The company did not disclose how much they paid for the escort service and the Russian pilots. An 18 September 2009 press release stated that the company was planning for six vessels to make Arctic deliveries in 2010. It is not clear that this plan was followed up on.

In 2009, the first two international commercial cargo vessels traveled north of Russia between Europe and Asia. In 2011, 18 ships made the now mostly ice-free transit. During 2011, 34 ships made the transit up from a total of 6 ships in 2010. In 2012, 46 commercial ships made the transit. Petroleum products constituted the largest cargo group. In 2013 71 commercial ships made the transit.

On 28 July 2009, the sailing yacht RX II (36-foot length), with expedition leader Trond Aasvoll and crew Hans Fredrik Haukland and Finn Andreassen left Vardø in Norway on a quest to circumnavigate the North Pole. The northern sea route proved ice free and the three Norwegians sailed into the Bering Strait on 24 September. But Russian bureaucracy managed to do what the arctic waters didn't – to stop their effort to sail around in one season. The boat over-wintered in Nome, and finished the trip through the Northwest passage the following summer.

Also in 2009, Ola Skinnarmo and his crew sailed the Northeast Passage aboard Explorer of Sweden, becoming the second Swedish sailboat to transit the Northeast Passage, after Adolf Erik Nordenskiöld.

In September 2010, two yachts circumnavigated the Arctic: Børge Ousland's team aboard The Northern Passage, and Sergei Murzayev's team in the Peter I. These were the first recorded instances of the circumnavigation of the Arctic by sailing yachts in one season.

The largest ship as of 2011 is the 117,000 tonne SCF Baltica loaded with natural-gas condensate.

In 2012, the 288-metre (945 ft) LNG carrier Ob River became the first ship of its kind to transit the Northern Sea Route. The vessel completed the westbound voyage in ballast in only six days and planned to sail back to Asia in November with a full load of liquified natural gas. The growth in traffic has been startling. 46 ships sailed the entire length from Europe to East Asia during 2012. By July 2013, the administrators of the Northern Sea Route had granted permission to 204 ships to sail during the season. By that time, Arctic sea ice had declined substantial especially on the Atlantic side of the Arctic. "On July 15 extent came within 540,000 square kilometers (208,000 square miles) of that seen in 2012 on the same date... (Compared to the 1981 to 2010 average, ice extent on July 15, 2013 was 1.06 million square kilometers (409,000 square miles) below average.)" (Summer 2012 Arctic sea ice volume reached a record low.)

During early September 2013 the Russian battlecruiser Petr Velikiy led a flotilla of Russian navy ships with icebreaker support along the Northern Sea Route to the New Siberian Islands. About 400 ships were expected to transit the Russian portion of the route during the 2013 season, up from about 40 during 2012.

On 15 September 2015, the Chinese trimaran Qingdao China set a speed record by sailing from Murmansk to the Bering Strait in 13 days.

On 3 October 2019 Nanni Acquarone became the first Italian skipper with the Italian cutter Best Explorer to sail both Northwest Passage in 2012 and Northeast Passage with a sailboat clockwise. Best Explorer started 1 June 2012 from Tromsø (Norway) sailing the Northwest Passage (first Italian boat and Italian skipper) and after several years of sailing in the Pacific got the permission to follow the Northeast Passage without assistance and without a Russian on board with a crew of 5, including Salvatore Magri who sailed the Northwest Passage with Nanni. In 2019 Best Explorer left Petropavlovsk Kamchatski on 3 August and crossed the Bering Strait on 19 August reaching Murmansk on 22 September.

Commemoration

In 2007, Finland issued a €10 Adolf Erik Nordenskiöld and Northeast Passage commemorative coin to celebrate the 175th anniversary of Nordenskiöld's birth and his discovery of the northern sea route. The obverse features an abstract portrait of Nordenskiöld at the helm of his ship. The reverse is dominated by a pattern resembling the labyrinth formed by adjacent ice floes. The coin is one of the Europa Coins 2007 series, which celebrates European achievements in history.

Monday, August 18, 2025

Thermal energy storage

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Thermal_energy_storage

Thermal energy storage (TES) is the storage of thermal energy for later reuse. Employing widely different technologies, it allows surplus thermal energy to be stored for hours, days, or months. Scale both of storage and use vary from small to large – from individual processes to district, town, or region. Usage examples are the balancing of energy demand between daytime and nighttime, storing summer heat for winter heating, or winter cold for summer cooling (Seasonal thermal energy storage). Storage media include water or ice-slush tanks, masses of native earth or bedrock accessed with heat exchangers by means of boreholes, deep aquifers contained between impermeable strata; shallow, lined pits filled with gravel and water and insulated at the top, as well as eutectic solutions and phase-change materials.

Other sources of thermal energy for storage include heat or cold produced with heat pumps from off-peak, lower cost electric power, a practice called peak shaving; heat from combined heat and power (CHP) power plants; heat produced by renewable electrical energy that exceeds grid demand and waste heat from industrial processes. Heat storage, both seasonal and short term, is considered an important means for cheaply balancing high shares of variable renewable electricity production and integration of electricity and heating sectors in energy systems almost or completely fed by renewable energy.

Categories

The kinds of thermal energy storage can be divided into three separate categories: sensible heat, latent heat, and thermo-chemical heat storage. Each of these has different advantages and disadvantages that determine their applications.

Sensible heat storage

Sensible heat storage (SHS) is the most straightforward method. It simply means the temperature of some medium is either increased or decreased. This type of storage is the most commercially available out of the three; other techniques are less developed.

The materials are generally inexpensive and safe. One of the cheapest, most commonly used options is a water tank, but materials such as molten salts or metals can be heated to higher temperatures and therefore offer a higher storage capacity. Energy can also be stored underground (UTES), either in an underground tank or in some kind of heat-transfer fluid (HTF) flowing through a system of pipes, either placed vertically in U-shapes (boreholes) or horizontally in trenches. Yet another system is known as a packed-bed (or pebble-bed) storage unit, in which some fluid, usually air, flows through a bed of loosely packed material (usually rock, pebbles or ceramic brick) to add or extract heat.

A disadvantage of SHS is its dependence on the properties of the storage medium. Storage capacities are limited by the specific heat capacity of the storage material, and the system needs to be properly designed to ensure energy extraction at a constant temperature.

Heat storage in tanks, ponds or rock caverns

A steam accumulator consists of an insulated steel pressure tank containing hot water and steam under pressure. As a heat storage device, it is used to mediate heat production by a variable or steady source from a variable demand for heat. Steam accumulators may take on a significance for energy storage in solar thermal energy projects.

Water has one of the highest thermal capacities at 4.2 kJ/(kg⋅K). Large stores, mostly hot water storage tanks, are widely used in Nordic countries to store heat for several days, to decouple heat and power production and to help meet peak demands. Some towns use insulated ponds heated by solar power as a heat source for district heating pumps. Intersessional storage in caverns has been investigated and appears to be economical and plays a significant role in heating in Finland. Energy producer Helen Oy estimates an 11.6 GWh capacity and 120 MW thermal output for its 260,000 m³ water cistern under Mustikkamaa (fully charged or discharged in 4 days at capacity), operating from 2021 to offset days of peak production/demand; while the 300,000 m³ rock caverns 50 m under sea level in Kruunuvuorenranta (near Laajasalo) were designated in 2018 to store heat in summer from warm seawater and release it in winter for district heating. In 2024, it was announced that the municipal energy supplier of Vantaa had commissioned an underground heat storage facility of over 1,100,000 cubic metres (39,000,000 cu ft) in size and 90 GWh in capacity to be built, expected to be operational in 2028.

Molten salt technology

The sensible heat of molten salt is also used for storing solar energy at a high temperature, termed molten-salt technology or molten salt energy storage (MSES). Molten salts can be employed as a thermal energy storage method to retain thermal energy. Presently, this is a commercially used technology to store the heat collected by concentrated solar power (e.g., from a solar tower or solar trough). The heat can later be converted into superheated steam to power conventional steam turbines and generate electricity at a later time. It was demonstrated in the Solar Two project from 1995 to 1999. Estimates in 2006 predicted an annual efficiency of 99%, a reference to the energy retained by storing heat before turning it into electricity, versus converting heat directly into electricity. Various eutectic mixtures of different salts are used (e.g., sodium nitrate, potassium nitrate and calcium nitrate). Experience with such systems exists in non-solar applications in the chemical and metals industries as a heat-transport fluid.

The salt melts at 131 °C (268 °F). It is kept liquid at 288 °C (550 °F) in an insulated "cold" storage tank. The liquid salt is pumped through panels in a solar collector where the focused sun heats it to 566 °C (1,051 °F). It is then sent to a hot storage tank. With proper insulation of the tank the thermal energy can be usefully stored for up to a week. When electricity is needed, the hot molten salt is pumped to a conventional steam-generator to produce superheated steam for driving a conventional turbine/generator set as used in a coal, oil, or nuclear power plant. A 100-megawatt turbine would need a tank of about 9.1 metres (30 ft) tall and 24 metres (79 ft) in diameter to drive it for four hours by this design.

A single tank with a divider plate to separate cold and hot molten salt is under development. It is more economical by achieving 100% more heat storage per unit volume over the dual tanks system as the molten-salt storage tank is costly due to its complicated construction. phase-change material (PCMs) are also used in molten-salt energy storage, while research on obtaining shape-stabilized PCMs using high porosity matrices is ongoing.

Most solar thermal power plants use this thermal energy storage concept. The Solana Generating Station in the U.S. can store 6 hours worth of generating capacity in molten salt. During the summer of 2013 the Gemasolar Thermosolar solar power-tower/molten-salt plant in Spain achieved a first by continuously producing electricity 24 hours per day for 36 days. The Cerro Dominador Solar Thermal Plant, inaugurated in June 2021, has 17.5 hours of heat storage.

Hot silicon technology

Solid or molten silicon offers much higher storage temperatures than salts with consequent greater capacity and efficiency. It is being researched as a possible more energy efficient storage technology. Silicon is able to store more than 1 MWh of energy per cubic meter at 1400 °C. An additional advantage is the relative abundance of silicon when compared to the salts used for the same purpose.

Molten aluminum

Another medium that can store thermal energy is molten (recycled) aluminum. This technology was developed by the Swedish company Azelio. The material is heated to 600 °C. When needed, the energy is transported to a Stirling engine using a heat-transfer fluid.

Heat storage using oils

Using oils as sensible heat storage materials is an effective approach for storing thermal energy, particularly in medium- to high-temperature applications. Different types of oils are used based on the temperature range and the specific requirements of the thermal energy storage system: mineral oils, synthetic oils are more recently, vegetable oils are gaining interest because they are renewable and biodegradable. Numerious criteria are used to select an oil for a particular application: high energy storage capacity and specific heat capacity, high thermal conductivity, high chemical and physical stability, low coefficient of expansion, low cost, availability, low corrosion and compatibility with compounds materials, limited environmental issues, etc. Regarding the selection of a low-cost or cost-effective thermal oil, it is important to consider not only the acquisition or purchase cost, but also the operating and replacement costs or even final disposal costs. An oil that is initially more expensive may prove to be more cost-effective in the long run if it offers higher thermal stability, thereby reducing the frequency of replacement.

Heat storage in hot rocks or concrete

Rock, sand and concrete has a heat capacity about one third of water's. On the other hand, concrete can be heated to much higher temperatures (1200 °C) by for example electrical heating and therefore has a much higher overall volumetric capacity. Thus in the example below, an insulated cube of about 2.8 m³ would appear to provide sufficient storage for a single house to meet 50% of heating demand. This could, in principle, be used to store surplus wind or solar heat due to the ability of electrical heating to reach high temperatures. At the neighborhood level, the Wiggenhausen-Süd solar development at Friedrichshafen in southern Germany has received international attention. This features a 12,000 m³ (420,000 cu ft) reinforced concrete thermal store linked to 4,300 m² (46,000 sq ft) of solar collectors, which will supply the 570 houses with around 50% of their heating and hot water. Siemens-Gamesa built a 130 MWh thermal storage near Hamburg with 750 °C in basalt and 1.5 MW electric output. A similar system was scheduled for Sorø, Denmark, with 41–58% of the stored 18 MWh heat returned for the town's district heating, and 30–41% returned as electricity, but not retained.

“Brick toaster” is a recently (August 2022) announced innovative heat reservoir operating at up to 1,500 °C (2,732 °F) that its maker, Titan Cement/Rondo claims should be able cut global CO
₂ output by 15% over 15 years.

Research into using sintered bauxite proppants as the thermal store, heating them up to 1000 °C. This material was tested against plasma-sprayed alumina and mullite, alumina fiber reinforced/alumina matrix and mullite fiber reinforced/mullite ceramic matrix composites. These four materials were considered because of their usefulness as solar receivers, transport tubes and storage tanks.

Latent heat storage

Because latent heat storage (LHS) is associated with a phase transition, the general term for the associated media is Phase-Change Material (PCM). During these transitions, heat can be added or extracted without affecting the material's temperature, giving it an advantage over SHS-technologies. Storage capacities are often higher as well.

There are a multitude of PCMs available, including but not limited to salts, polymers, gels, paraffin waxes, metal alloys and semiconductor-metal alloys, each with different properties. This allows for a more target-oriented system design. As the process is isothermal at the PCM's melting point, the material can be picked to have the desired temperature range. Desirable qualities include high latent heat and thermal conductivity. Furthermore, the storage unit can be more compact if volume changes during the phase transition are small.

PCMs are further subdivided into organic, inorganic and eutectic materials. Compared to organic PCMs, inorganic materials are less flammable, cheaper and more widely available. They also have higher storage capacity and thermal conductivity. Organic PCMs, on the other hand, are less corrosive and not as prone to phase-separation. Eutectic materials, as they are mixtures, are more easily adjusted to obtain specific properties, but have low latent and specific heat capacities.

Another important factor in LHS is the encapsulation of the PCM. Some materials are more prone to erosion and leakage than others. The system must be carefully designed in order to avoid unnecessary loss of heat.

Miscibility gap alloy technology

Miscibility gap alloys rely on the phase change of a metallic material (see: latent heat) to store thermal energy.

Rather than pumping the liquid metal between tanks as in a molten-salt system, the metal is encapsulated in another metallic material that it cannot alloy with (immiscible). Depending on the two materials selected (the phase changing material and the encapsulating material) storage densities can be between 0.2 and 2 MJ/L.

A working fluid, typically water or steam, is used to transfer the heat into and out of the system. Thermal conductivity of miscibility gap alloys is often higher (up to 400 W/(m⋅K)) than competing technologies which means quicker "charge" and "discharge" of the thermal storage is possible. The technology has not yet been implemented on a large scale.

Ice-based technology

Several applications are being developed where ice is produced during off-peak periods and used for cooling at a later time. For example, air conditioning can be provided more economically by using low-cost electricity at night to freeze water into ice, then using the cooling capacity of ice in the afternoon to reduce the electricity needed to handle air conditioning demands. Thermal energy storage using ice makes use of the large heat of fusion of water. Historically, ice was transported from mountains to cities for use as a coolant. One metric ton of water (= one cubic meter) can store 334 million joules (MJ) or 317,000 BTUs (93 kWh). A relatively small storage facility can hold enough ice to cool a large building for a day or a week.

In addition to using ice in direct cooling applications, it is also being used in heat pump-based heating systems. In these applications, the phase change energy provides a very significant layer of thermal capacity that is near the bottom range of temperature that water source heat pumps can operate in. This allows the system to ride out the heaviest heating load conditions and extends the timeframe by which the source energy elements can contribute heat back into the system.

Cryogenic energy storage

Cryogenic energy storage uses liquification of air or nitrogen as an energy store.

A pilot cryogenic energy system that uses liquid air as the energy store, and low-grade waste heat to drive the thermal re-expansion of the air, operated at a power station in Slough, UK in 2010.

Thermo-chemical heat storage

Thermo-chemical heat storage (TCS) involves some kind of reversible exotherm/endotherm chemical reaction with thermo-chemical materials (TCM) . Depending on the reactants, this method can allow for an even higher storage capacity than LHS.

In one type of TCS, heat is applied to decompose certain molecules. The reaction products are then separated, and mixed again when required, resulting in a release of energy. Some examples are the decomposition of potassium oxide (over a range of 300–800 °C, with a heat decomposition of 2.1 MJ/kg), lead oxide (300–350 °C, 0.26 MJ/kg) and calcium hydroxide (above 450 °C, where the reaction rates can be increased by adding zinc or aluminum). The photochemical decomposition of nitrosyl chloride can also be used and, since it needs photons to occur, works especially well when paired with solar energy.

Adsorption (or Sorption) solar heating and storage

Adsorption processes also fall into this category. It can be used to not only store thermal energy, but also control air humidity. Zeolites (microporous crystalline alumina-silicates) and silica gels are well suited for this purpose. In hot, humid environments, this technology is often used in combination with lithium chloride to cool water.

The low cost ($200/ton) and high cycle rate (2,000×) of synthetic zeolites such as Linde 13X with water adsorbate has garnered much academic and commercial interest recently for use for thermal energy storage (TES), specifically of low-grade solar and waste heat. Several pilot projects have been funded in the EU from 2000 to the present (2020). The basic concept is to store solar thermal energy as chemical latent energy in the zeolite. Typically, hot dry air from flat plate solar collectors is made to flow through a bed of zeolite such that any water adsorbate present is driven off. Storage can be diurnal, weekly, monthly, or even seasonal depending on the volume of the zeolite and the area of the solar thermal panels. When heat is called for during the night, or sunless hours, or winter, humidified air flows through the zeolite. As the humidity is adsorbed by the zeolite, heat is released to the air and subsequently to the building space. This form of TES, with specific use of zeolites, was first taught by Guerra in 1978. Advantages over molten salts and other high temperature TES include that (1) the temperature required is only the stagnation temperature typical of a solar flat plate thermal collector, and (2) as long as the zeolite is kept dry, the energy is stored indefinitely. Because of the low temperature, and because the energy is stored as latent heat of adsorption, thus eliminating the insulation requirements of a molten salt storage system, costs are significantly lower.

Salt hydrate technology

One example of an experimental storage system based on chemical reaction energy is the salt hydrate technology. The system uses the reaction energy created when salts are hydrated or dehydrated. It works by storing heat in a container containing 50% sodium hydroxide (NaOH) solution. Heat (e.g. from using a solar collector) is stored by evaporating the water in an endothermic reaction. When water is added again, heat is released in an exothermic reaction at 50 °C (120 °F). Current systems operate at 60% efficiency. The system is especially advantageous for seasonal thermal energy storage, because the dried salt can be stored at room temperature for prolonged times, without energy loss. The containers with the dehydrated salt can even be transported to a different location. The system has a higher energy density than heat stored in water and the capacity of the system can be designed to store energy from a few months to years.

In 2013 the Dutch technology developer TNO presented the results of the MERITS project to store heat in a salt container. The heat, which can be derived from a solar collector on a rooftop, expels the water contained in the salt. When the water is added again, the heat is released, with almost no energy losses. A container with a few cubic meters of salt could store enough of this thermochemical energy to heat a house throughout the winter. In a temperate climate like that of the Netherlands, an average low-energy household requires about 6.7 GJ/winter. To store this energy in water (at a temperature difference of 70 °C), 23 m³ insulated water storage would be needed, exceeding the storage abilities of most households. Using salt hydrate technology with a storage density of about 1 GJ/m³, 4–8 m³ could be sufficient.

As of 2016, researchers in several countries are conducting experiments to determine the best type of salt, or salt mixture. Low pressure within the container seems favorable for the energy transport. Especially promising are organic salts, so called ionic liquids. Compared to lithium halide-based sorbents they are less problematic in terms of limited global resources and compared to most other halides and sodium hydroxide (NaOH) they are less corrosive and not negatively affected by CO₂ contaminations.

However, a recent meta-analysis on studies of thermochemical heat storage suggests that salt hydrates offer very low potential for thermochemical heat storage, that absorption processes have prohibitive performance for long-term heat storage, and that thermochemical storage may not be suitable for long-term solar heat storage in buildings.

Molecular bonds

Storing energy in molecular bonds is being investigated. Energy densities equivalent to lithium-ion batteries have been achieved. This has been done by a DSPEC (dys-sensitized photoelectrosythesis cell). This is a cell that can store energy that has been acquired by solar panels during the day for night-time (or even later) use. It is designed by taking an indication from, well known, natural photosynthesis.

The DSPEC generates hydrogen fuel by making use of the acquired solar energy to split water molecules into its elements. As the result of this split, the hydrogen is isolated and the oxygen is released into the air. This sounds easier than it actually is. Four electrons of the water molecules need to be separated and transported elsewhere. Another difficult part is the process of merging the two separate hydrogen molecules.

The DSPEC consists of two components: a molecule and a nanoparticle. The molecule is called a chromophore-catalyst assembly which absorbs sunlight and kick starts the catalyst. This catalyst separates the electrons and the water molecules. The nanoparticles are assembled into a thin layer and a single nanoparticle has many chromophore-catalyst on it. The function of this thin layer of nanoparticles is to transfer away the electrons which are separated from the water. This thin layer of nanoparticles is coated by a layer of titanium dioxide. With this coating, the electrons that come free can be transferred more quickly so that hydrogen could be made. This coating is, again, coated with a protective coating that strengthens the connection between the chromophore-catalyst and the nanoparticle.

Using this method, the solar energy acquired from the solar panels is converted into fuel (hydrogen) without releasing the so-called greenhouse gasses. This fuel can be stored into a fuel cell and, at a later time, used to generate electricity.

Molecular Solar Thermal System (MOST)

Another promising way to store solar energy for electricity and heat production is a so-called molecular solar thermal system (MOST). With this approach a molecule is converted by photoisomerization into a higher-energy isomer. Photoisomerization is a process in which one (cis trans) isomer is converted into another by light (solar energy). This isomer is capable of storing the solar energy until the energy is released by a heat trigger or catalyst (then, the isomer is converted into its original isomer). A promising candidate for such a MOST is Norbornadiene (NBD). This is because there is a high energy difference between the NBD and the quadricyclane (QC) photoisomer. This energy difference is approximately 96 kJ/mol. It is also known that for such systems, the donor-acceptor substitutions provide an effective means for red shifting the longest-wavelength absorption. This improves the solar spectrum match.

A crucial challenge for a useful MOST system is to acquire a satisfactory high energy storage density (if possible, higher than 300 kJ/kg). Another challenge of a MOST system is that light can be harvested in the visible region. The functionalization of the NBD with the donor and acceptor units is used to adjust this absorption maxima. However, this positive effect on the solar absorption is compensated by a higher molecular weight. This implies a lower energy density. This positive effect on the solar absorption has another downside. Namely, that the energy storage time is lowered when the absorption is redshifted. A possible solution to overcome this anti-correlation between the energy density and the red shifting is to couple one chromophore unit to several photo switches. In this case, it is advantageous to form so called dimers or trimers. The NBD share a common donor and/or acceptor.

Kasper Moth-Poulsen and his team tried to engineer the stability of the high energy photo isomer by having two electronically coupled photo switches with separate barriers for thermal conversion. By doing so, a blue shift occurred after the first isomerization (NBD-NBD to QC-NBD). This led to a higher energy of isomerization of the second switching event (QC-NBD to QC-QC). Another advantage of this system, by sharing a donor, is that the molecular weight per norbornadiene unit is reduced. This leads to an increase of the energy density.

Eventually, this system could reach a quantum yield of photoconversion up 94% per NBD unit. A quantum yield is a measure of the efficiency of photon emission. With this system the measured energy densities reached up to 559 kJ/kg (exceeding the target of 300 kJ/kg). So, the potential of the molecular photo switches is enormous—not only for solar thermal energy storage but for other applications as well.

In 2022, researchers reported combining the MOST with a chip-sized thermoelectric generator to generate electricity from it. The system can reportedly store solar energy for up to 18 years and may be an option for renewable energy storage.

Thermal battery

A thermal energy battery is a physical structure used for the purpose of storing and releasing thermal energy. Such a thermal battery (a.k.a. TBat) allows energy available at one time to be temporarily stored and then released at another time. The basic principles involved in a thermal battery occur at the atomic level of matter, with energy being added to or taken from either a solid mass or a liquid volume which causes the substance's temperature to change. Some thermal batteries also involve causing a substance to transition thermally through a phase transition which causes even more energy to be stored and released due to the delta enthalpy of fusion or delta enthalpy of vaporization.

Thermal batteries are very common, and include such familiar items as a hot water bottle. Early examples of thermal batteries include stone and mud cook stoves, rocks placed in fires, and kilns. While stoves and kilns are ovens, they are also thermal storage systems that depend on heat being retained for an extended period of time. Thermal energy storage systems can also be installed in domestic situations with heat batteries and thermal stores being amongst the most common types of energy storage systems installed at homes in the UK.

Types of thermal batteries

Thermal batteries generally fall into 4 categories with different forms and applications, although fundamentally all are for the storage and retrieval of thermal energy. They also differ in method and density of heat storage.

Phase change thermal battery

Phase change materials used for thermal storage are capable of storing and releasing significant thermal capacity at the temperature that they change phase. These materials are chosen based on specific applications because there is a wide range of temperatures that may be useful in different applications and a wide range of materials that change phase at different temperatures. These materials include salts and waxes that are specifically engineered for the applications they serve. In addition to manufactured materials, water is a phase change material. The latent heat of water is 334 joules/gram. The phase change of water occurs at 0 °C (32 °F).

Some applications use the thermal capacity of water or ice as cold storage; others use it as heat storage. It can serve either application; ice can be melted to store heat then refrozen to warm an environment. The advantage of using a phase change in this way is that a given mass of material can absorb a large quantity of energy without its temperature changing. Hence a thermal battery that uses a phase change can be made lighter, or more energy can be put into it without raising the internal temperature unacceptably.

Encapsulated thermal battery

An encapsulated thermal battery is physically similar to a phase change thermal battery in that it is a confined amount of physical material which is thermally heated or cooled to store or extract energy. However, in a non-phase change encapsulated thermal battery, the temperature of the substance is changed without inducing a phase change. Since a phase change is not needed many more materials are available for use in an encapsulated thermal battery. One of the key properties of an encapsulated thermal battery is its volumetric heat capacity (VHC), also termed volume-specific heat capacity. Several substances are used for these thermal batteries, for example water, concrete, and wet or dry sand.

An example of an encapsulated thermal battery is a residential water heater with a storage tank.This thermal battery is usually slowly charged over a period of about 30–60 minutes for rapid use when needed (e.g., 10–15 minutes). Many utilities, understanding the "thermal battery" nature of water heaters, have begun using them to absorb excess renewable energy power when available for later use by the homeowner. According to the above-cited article, "net savings to the electricity system as a whole could be $200 per year per heater — some of which may be passed on to its owner".

A district heating storage using sand or stone operates in Pornainen in Finland, where a 1 MW / 100 MWh heat storage (using 2,000 tons of soapstone waste) is charged by surplus electricity, and can serve the area's heating demand for a week. It follows research with a prototype 0.1 MW / 8 MWh sand battery that was built in 2022 to store renewable solar and wind power as heat, for later use as district heating, and possible later power generation. In Canada, single building thermal storage also stores renewable solar and wind power as heat, for later use as space or water heating for the building in which it's installed. It differs from the system in Finland by being compact, using low pressure pumped fluids, and can only heat one building rather than several. It can take in waste heat from alternate sources such as computer server rooms or compost heaps and store it for later distribution.

Ground heat exchange thermal battery

Thermal battery
Component type	Energy
Working principle	Thermodynamics
Inventor	Heat pumps, as used by the GHEX depicted above, were invented in the 1940s by Robert C. Webber.
First produced	Heat pumps were first produced in the 1970s.

A ground heat exchanger (GHEX) is an area of the earth that is utilized as a seasonal/annual cycle thermal battery. These thermal batteries are areas of the earth into which pipes have been placed in order to transfer thermal energy. Energy is added to the GHEX by running a higher temperature fluid through the pipes and thus raising the temperature of the local earth. Energy can also be taken from the GHEX by running a lower-temperature fluid through those same pipes.

GHEX are usually implemented in two forms. The picture above depicts what is known as a "horizontal" GHEX where trenching is used to place an amount of pipe in a closed loop in the ground. They are also formed by drilling boreholes into the ground, either vertically or horizontally, and then the pipes are inserted in the form of a closed-loop with a "u-bend" fitting on the far end of the loop.

Heat energy can be added to or removed from a GHEX at any point in time. However, they are most often used as a Seasonal thermal energy storage operating on an annual cycle where energy is extracted from a building during the summer season to cool a building and added to the GHEX. Then that same energy is later extracted from the GHEX in the winter season to heat the building. This annual cycle of energy addition and subtraction is highly predictable based on energy modelling of the building served. A thermal battery used in this mode is a renewable energy source as the energy extracted in the winter will be restored to the GHEX the next summer in a continually repeating cycle. This type is solar powered because it is the heat from the sun in the summer that is removed from a building and stored in the ground for use in the next winter season for heating. There are two main methods of Thermal Response Testing that are used to characterize the thermal conductivity and Thermal Capacity/Diffusivity of GHEX Thermal Batteries—Log-Time 1-Dimensional Curve Fit and newly released Advanced Thermal Response Testing.

A good example of the Annual Cycle nature of a GHEX Thermal Battery can be seen in the ASHRAE Building study. As seen there in the 'Ground Loop and Ambient Air temperatures by date' graphic (Figure 2–7), one can easily see the annual cycle sinusoidal shape of the ground temperature as heat is seasonally extracted from the ground in winter and rejected to the ground in summer, creating a ground "thermal charge" in one season that is not uncharged and driven the other direction from neutral until a later season. Other more advanced examples of Ground-based Thermal Batteries utilizing intentional well-bore thermal patterns are currently in research and early use.

Molten-salt batteries

In the defense industry primary molten-salt batteries are termed "thermal batteries". They are non-rechargeable electrical batteries using a low-melting eutectic mixture of ionic metal salts (sodium, potassium and lithium chlorides, bromides, etc.) as the electrolyte, manufactured with the salts in solid form. As long as the salts remain solid, the battery has a long shelf life of up to 50 years. Once activated (usually by a pyrotechnic heat source) and the electrolyte melts, it is very reliable with a high energy and power density. They are extensively used for military applications such as small to large guided missiles, and nuclear weapons.

Other thermal batteries

There are other items that have historically been termed "thermal batteries", such as energy-storage heat packs that skiers use for keeping hands and feet warm (see hand warmer). These contain iron powder moist with oxygen-free salt water which rapidly corrodes over a period of hours, releasing heat, when exposed to air. Instant cold packs absorb heat by a non-chemical phase-change such as by absorbing the endothermic heat of solution of certain compounds.

The one common principle of these other thermal batteries is that the reaction involved is not reversible. Thus, these batteries are not used for storing and retrieving heat energy.

Electric thermal storage

Storage heaters are commonplace in European homes with time-of-use metering (traditionally using cheaper electricity at nighttime). They consist of high-density ceramic bricks or feolite blocks heated to a high temperature with electricity and may or may not have good insulation and controls to release heat over a number of hours. Some advice not to use them in areas with young children or where there is an increased risk of fires due to poor housekeeping, both due to the high temperatures involved.

With the rise of wind and solar power (and other renewable energies) providing an ever increasing share of energy input into the electricity grids in some countries, the use of larger scale electric energy storage is being explored by several commercial companies. Ideally, the utilisation of surplus renewable energy is transformed into high temperature high grade heat in highly insulated heat stores, for release later when needed. An emerging technology is the use of vacuum super insulated (VSI) heat stores. The use of electricity to generate heat, and not say direct heat from solar thermal collectors, means that very high temperatures can be realised, potentially allowing for inter seasonal heat transfer—storing high grade heat in summer from surplus photovoltaics generation into heat stored for the following winter with relatively minimal standing losses.

Solar energy storage

Solar energy is an application of thermal energy storage. Most practical solar thermal storage systems provide storage from a few hours to a day's worth of energy. However, a growing number of facilities use seasonal thermal energy storage (STES), enabling solar energy to be stored in summer to heat space during winter. In 2017 Drake Landing Solar Community in Alberta, Canada, achieved a year-round 97% solar heating fraction, a world record made possible by incorporating STES.

The combined use of latent heat and sensible heat are possible with high temperature solar thermal input. Various eutectic metal mixtures, such as aluminum and silicon (AlSi
₁₂) offer a high melting point suited to efficient steam generation, while high alumina cement-based materials offer good storage capabilities.

Pumped-heat electricity storage

In pumped-heat electricity storage (PHES), a reversible heat-pump system is used to store energy as a temperature difference between two heat stores.

Isentropic

Isentropic systems involve two insulated containers filled, for example, with crushed rock or gravel: a hot vessel storing thermal energy at high temperature/pressure, and a cold vessel storing thermal energy at low temperature/pressure. The vessels are connected at top and bottom by pipes and the whole system is filled with an inert gas such as argon.

While charging, the system can use off-peak electricity to work as a heat pump. One prototype used argon at ambient temperature and pressure from the top of the cold store is compressed adiabatically, to a pressure of, for example, 12 bar, heating it to around 500 °C (900 °F). The compressed gas is transferred to the top of the hot vessel where it percolates down through the gravel, transferring heat to the rock and cooling to ambient temperature. The cooled, but still pressurized, gas emerging at the bottom of the vessel is then adiabatically expanded to 1 bar, which lowers its temperature to −150 °C. The cold gas is then passed up through the cold vessel where it cools the rock while warming to its initial condition.

The energy is recovered as electricity by reversing the cycle. The hot gas from the hot vessel is expanded to drive a generator and then supplied to the cold store. The cooled gas retrieved from the bottom of the cold store is compressed which heats the gas to ambient temperature. The gas is then transferred to the bottom of the hot vessel to be reheated.

The compression and expansion processes are provided by a specially designed reciprocating machine using sliding valves. Surplus heat generated by inefficiencies in the process is shed to the environment through heat exchangers during the discharging cycle.

The developer claimed that a round trip efficiency of 72–80% was achievable. This compares to >80% achievable with pumped hydro energy storage.

Another proposed system uses turbomachinery and is capable of operating at much higher power levels. Use of phase change material as heat storage material could enhance performance.

Octet rule

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Octet_rule

The bonding in carbon dioxide (CO₂): all atoms are surrounded by 8 electrons, fulfilling the **octet rule**.

The octet rule is a chemical rule of thumb that reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens, although more generally the rule is applicable for the s-block and p-block of the periodic table. Other rules exist for other elements, such as the duplet rule for hydrogen and helium, and the 18-electron rule for transition metals.

The valence electrons in molecules like carbon dioxide (CO₂) can be visualized using a Lewis electron dot diagram. In covalent bonds, electrons shared between two atoms are counted toward the octet of both atoms. In carbon dioxide each oxygen shares four electrons with the central carbon, two (shown in red) from the oxygen itself and two (shown in black) from the carbon. All four of these electrons are counted in both the carbon octet and the oxygen octet, so that both atoms are considered to obey the octet rule.

Example: sodium chloride (NaCl)

The octet rule is simplest in the case of ionic bonding between two atoms, one a metal of low electronegativity and the other a nonmetal of high electronegativity. For example, sodium metal and chlorine gas combine to form sodium chloride, a crystal lattice composed of alternating sodium and chlorine nuclei. Electron density inside this lattice forms clumps at the atomic scale, as follows.

An isolated chlorine atom (Cl) has two and eight electrons in its first and second electron shells, located near the nucleus. However, it has only seven electrons in the third and outermost electron shell. One additional electron would completely fill the outer electron shell with eight electrons, a situation the octet rule commends. Indeed, adding an electron to the produce the chloride ion (Cl⁻) releases 3.62 eV of energy. Conversely, another surplus electron cannot fit in the same shell, instead beginning the fourth electron shell around the nucleus. Thus the octet rule proscribes formation of a hypothetical Cl²⁻ ion, and indeed the latter has only been observed as a plasma under extreme conditions.

A sodium atom (Na) has a single electron in its outermost electron shell, the first and second shells again being full with two and eight electrons respectively. The octet rule favors removal of this outermost electron to form the Na⁺ ion, which has the exact same electron configuration as Cl⁻. Indeed, sodium is observed to transfer one electron to chlorine during the formation of sodium chloride, such that the resulting lattice is best considered as a periodic array of Na⁺ and Cl⁻ ions.

To remove the outermost Na electron and return to an "octet-approved" state requires a small amount of energy: 5.14 eV. This energy is provided from the 3.62 eV released during chloride formation, and the electrostatic attraction between positively-charged Na⁺ and negatively-charged Cl⁻ ions, which releases a 8.12 eV lattice energy. By contrast, any further electrons removed from Na would reside in the deeper second electron shell, and produce an octet-violating Na²⁺ ion. Consequently, the second ionization energy required for the next removal is much larger – 47.28 eV – and the corresponding ion is only observed under extreme conditions.

History

In 1864, the English chemist John Newlands classified the sixty-two known elements into eight groups, based on their physical properties.

In the late 19th century, it was known that coordination compounds (formerly called "molecular compounds") were formed by the combination of atoms or molecules in such a manner that the valencies of the atoms involved apparently became satisfied. In 1893, Alfred Werner showed that the number of atoms or groups associated with a central atom (the "coordination number") is often 4 or 6; other coordination numbers up to a maximum of 8 were known, but less frequent. In 1904, Richard Abegg was one of the first to extend the concept of coordination number to a concept of valence in which he distinguished atoms as electron donors or acceptors, leading to positive and negative valence states that greatly resemble the modern concept of oxidation states. Abegg noted that the difference between the maximum positive and negative valences of an element under his model is frequently eight. In 1916, Gilbert N. Lewis referred to this insight as Abegg's rule and used it to help formulate his cubical atom model and the "rule of eight", which began to distinguish between valence and valence electrons. In 1919, Irving Langmuir refined these concepts further and renamed them the "cubical octet atom" and "octet theory". The "octet theory" evolved into what is now known as the "octet rule".

Walther Kossel and Gilbert N. Lewis saw that noble gases did not have the tendency of taking part in chemical reactions under ordinary conditions. On the basis of this observation, they concluded that atoms of noble gases are stable and on the basis of this conclusion they proposed a theory of valency known as "electronic theory of valency" in 1916:

During the formation of a chemical bond, atoms combine together by gaining, losing or sharing electrons in such a way that they acquire nearest noble gas configuration.

Explanation in quantum theory

The quantum theory of the atom explains the eight electrons as a closed shell with an s²p⁶ electron configuration. A closed-shell configuration is one in which low-lying energy levels are full and higher energy levels are empty. For example, the neon atom ground state has a full n = 2 shell (2s²2p⁶) and an empty n = 3 shell. According to the octet rule, the atoms immediately before and after neon in the periodic table (i.e. C, N, O, F, Na, Mg and Al), tend to attain a similar configuration by gaining, losing, or sharing electrons.

The argon atom has an analogous 3s²3p⁶ configuration. There is also an empty 3d level, but it is at considerably higher energy than 3s and 3p (unlike in the hydrogen atom), so that 3s²3p⁶ is still considered a closed shell for chemical purposes. The atoms immediately before and after argon tend to attain this configuration in compounds. There are, however, some hypervalent molecules in which the 3d level may play a part in the bonding, although this is controversial (see below).

For helium there is no 1p level according to the quantum theory, so that 1s² is a closed shell with no p electrons. The atoms before and after helium (H and Li) follow a duet rule and tend to have the same 1s² configuration as helium.

Exceptions

Many reactive intermediates do not obey the octet rule. Most are unstable, although some can be isolated.

Typically, octet rule violations occur in either low-dimensional coordination geometries or in radical species. Although hypervalent molecules are commonly taught to violate the octet rule, ab initio calculations show that almost all known examples obey the octet rule. The compounds form many fractional bonds through resonance (see § Hypervalent molecules below).

Low-dimensional geometries

In the trigonal planar coordination geometry, one p orbital points out of the bonding plane, and can only overlap with nearby atomic orbitals in a π bond. If that p orbital would be empty in an isolated atom, it may be filled through an intramolecular dative bond, as with aminoboranes. However, in some cases (e.g. boron trichloride and various boranes, triphenylmethanium), no nearby filled orbital can profitably overlap with the empty p orbital. In such cases, the orbital remains empty, and the compound obeys a "sextet rule". Likewise, linear compounds, such as dimethylzinc, have two p orbitals perpendicular to the bonding axis, and may obey a "quartet rule". In either case, the empty unshielded orbitals tend to attract adducts.

Radicals

Radicals satisfy the octet rule in one spin orientation, with four spin-up electrons in the valence shell, and almost satisfy it in the opposite spin orientation. Thus, for example, the methyl radical (CH₃), which has an unpaired electron in a non-bonding orbital on the carbon atom and no electron of opposite spin in the same orbital. Another example is the radical chlorine monoxide (ClO^•) which is involved in ozone depletion.

Stable radicals tend to adopt states in which the unpaired electron can delocalize through resonance. In such cases, the octet rule can be restored through the formalism of a 1- or 3-electron bond.

Species such as carbenes can be interpreted two different ways, depending on their spin state. Triplet carbenes are best thought of as two radicals localized on the same atom, and obey the octet rule in those radicals' shared spin-up orientation. Singlet carbenes tend to adopt a planar configuration, and are best thought of as obeying the planar sextet rule.

Hypervalent molecules

Main-group elements in the third and later rows of the periodic table can form hypercoordinate or hypervalent molecules in which the central main-group atom is bonded to more than four other atoms, such as phosphorus pentafluoride, PF₅, and sulfur hexafluoride, SF₆. For example, in PF₅, if it is supposed that there are five true covalent bonds in which five distinct electron pairs are shared, then the phosphorus would be surrounded by 10 valence electrons in violation of the octet rule. In the early days of quantum mechanics, Pauling proposed that third-row atoms can form five bonds by using one s, three p and one d orbitals, or six bonds by using one s, three p and two d orbitals. To form five bonds, the one s, three p and one d orbitals combine to form five sp³d hybrid orbitals which each share an electron pair with a halogen atom, for a total of 10 shared electrons, two more than the octet rule predicts. Similarly to form six bonds, the six sp³d² hybrid orbitals form six bonds with 12 shared electrons. In this model the availability of empty d orbitals is used to explain the fact that third-row atoms such as phosphorus and sulfur can form more than four covalent bonds, whereas second-row atoms such as nitrogen and oxygen are strictly limited by the octet rule.

However other models describe the bonding using only s and p orbitals in agreement with the octet rule. A valence bond description of PF₅ uses resonance between different PF₄⁺ F⁻ structures, so that each F is bonded by a covalent bond in four structures and an ionic bond in one structure. Each resonance structure has eight valence electrons on P. A molecular orbital theory description considers the highest occupied molecular orbital to be a non-bonding orbital localized on the five fluorine atoms, in addition to four occupied bonding orbitals, so again there are only eight valence electrons on the phosphorus. The validity of the octet rule for hypervalent molecules is further supported by ab initio molecular orbital calculations, which show that the contribution of d functions to the bonding orbitals is small.

Nevertheless, for historical reasons, structures implying more than eight electrons around elements like P, S, Se, or I are still common in textbooks and research articles. In spite of the unimportance of d shell expansion in chemical bonding, this practice allows structures to be shown without using a large number of formal charges or using partial bonds and is recommended by the IUPAC as a convenient formalism in preference to depictions that better reflect the bonding. On the other hand, showing more than eight electrons around Be, B, C, N, O, or F (or more than two around H, He, or Li) is considered an error by most authorities. In particular, instead of pentavalent N, tetravalent N⁺ is written (e. g. not H−O−N(=O)=O but H−O−N⁺(=O)−O⁻).

Other rules

The octet rule is only applicable to main-group elements. Other elements follow other electron counting rules as their valence electron configurations are different from main-group elements. These other rules are shown below:

Element type	First shell	p-block (Main group)	d-block (Transition metal)
Electron counting rules	Duet/Duplet rule	Octet rule	18-electron rule
Full valence configuration	s²	s²p⁶	d¹⁰s²p⁶

The duet rule or duplet rule of the first shell applies to H, He and Li—the noble gas helium has two electrons in its outer shell, which is very stable. (Since there is no 1p subshell, 1s is followed immediately by 2s, and thus shell 1 can only have at most 2 valence electrons). Hydrogen only needs one additional electron to attain this stable configuration, while lithium needs to lose one.
For transition metals, molecules tend to obey the 18-electron rule which corresponds to the utilization of valence d, s and p orbitals to form bonding and non-bonding orbitals. However, unlike the octet rule for main-group elements, transition metals do not strictly obey the 18-electron rule and the valence electron count can vary between 12 and 18.

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