SES of this kind were to become the main European renewable energy.
The project lasted about 10 years, and then was abandoned by the founding groups, Since the reality of the European green energy industry turned out to be completely different and more prosaic – Chinese photovoltaics and terrestrial wind power generation located in Europe itself, and the idea of pulling the energy routes through Libya and Syria is too optimistic.
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The planned power lines in the desertec: three main directions with a capacity of 3×10 gigawatts (in the picture one of the weaker versions with 3х5) and several submarine cables.
However, powerful power lines arose in the desertec project not accidentally (it’s funny, by the way, that the area of the land under the power line in the project was more than the area under the SES) – this is one of the key technologies that can allow renewable energy generation grow to an overwhelming proportion, and vice versa: in the absence of energy transfer technology for long distances in Uh, quite possibly, are doomed to no more than a share of 30-40% in the European energy sector.
The mutual synergy of transcontinental transmission lines and RES is quite clearly visible on models (for example, in the giant LUT model and also in the model of Vyacheslav Laktyushin): the unification of many wind-generated regions separated by 1-2-3 thousand kilometers from each other destroys the mutual correlation of the level generating (common dangerous failures) and aligns amount of energy supplied to the system. The only question is, at what cost and with what losses may transfer energy to such a distance. The answer depends on different technologies, which are essentially three today: transmission by alternating current, constant and by superconducting wire. Although this division is a bit wrong (the superconductor can be with alternating and direct current), but from a system point of view it is legitimate.
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Not quite typical picture in the energy industry of Russia at the time of writing the article, but usually the flows between the regions do not exceed 1-2 GW.
However, the appearance of the power systems of the 70s-80s did not require powerful and long-distance power lines – the power station was more often more convenient to move to consumers, and the only exception was the then RES-hydrogeneration.
The hydroelectric power plants, specifically the Brazilian Itaipu hydroelectric project in the mid-1980s, led to the emergence of a new champion in the transmission of electricity, much and far – a direct-current line. The power of the Brazilian link is 2x 3150 MW with a voltage of + -600 kV for a distance of 800 km, the project is implemented by ABB. Such capacities are still on the verge of an accessible AC transmission line, however more losses paid off the project with conversion to direct current.
Itaipu HPP with a capacity of 14 GW – In the world for the capacity of hydroelectric power stations. Some of the generated energy is transmitted via the HVDC link to the São Paulo and Rio de Jainiro area.
Unlike AC power lines, the power transmission lines are free from inductive and capacitive losses (ie losses through a parasitic capacitive And inductive coupling of the conductor to the surrounding ground and water), and was originally actively used mainly when connecting to the general power system of large islands with submarine cables, where the AC line loss to water could reach 50-60% of the power. In addition, the transmission line with the same voltage level and wire cross section is capable of transmitting 15% more power over two wires than an AC power line in three. The problems with insulation in the power line of the PT are simpler – in fact, on an alternating current, the maximum amplitude of the voltage is 1.41 times greater than the current amplitude, according to which power is considered. Finally, the transmission line of the PT does not require synchronization of the generators on both sides, and thus eliminates many problems associated with the synchronization of remote areas.
And constant (DC) current. Comparison a little advertising, because With the same current (say 4000 A), the 800 kV alternating current transmission line will have a capacity of 5.5 GW versus 6.4 GW at the power line, although with twice the loss. With the same losses, the power will actually be 2 times different.
Calculation of losses for various power transmission lines that were supposed to be used in the Desertec project.
Of course, there are also disadvantages, and substantial. First, the DC current in the AC system requires rectification on one side and “curvature” (ie, the generation of a synchronous sine) on the other. When it comes to many gigawatts and hundreds of kilovolts – it’s performed by a very nontrivial (and very beautiful!) Equipment that costs hundreds of millions of dollars. In addition, before the beginning of 2010, the PTL transmission lines could only be of the point-to-point type, since there were no adequate switches for such voltages and DC power, and therefore, in the presence of many consumers, it was impossible to cut one of them with a short circuit – Only to extinguish the entire system. So the main use of high-power transmission lines PT – connection of two power districts, which were needed large flows. Literally just a few years ago, ABB (one of the three leaders in the creation of HVDC equipment) managed to create a “hybrid” thyristor-mechanical switch (similar in ideas to the ITER switch), which is capable of such work, and now the first high- Multibot “North-East Angra in India.
The ABB hybrid switch is not expressive enough (and not very light-shocked), but there megapafosnoe Hindu video on assembling a mechanical switch for voltage 1200 kV
Nevertheless, the technology of PT power engineering developed and became cheaper (largely due to the development of power semiconductors), and the appearance of gigawatts of RES-generation was quite ready to begin connecting remote powerful hydroelectric power stations and wind farms to Consumers. Especially many such projects have been implemented in recent years in China and India.
However, the thought goes further. In many models, the capacity of PT-transmission lines for energy transmission is used to equalize RES-variability, which is the most important factor in the implementation of 100% RES in large power systems. Moreover, this approach is already being put into practice: one can cite an example of a 1.4-gigawatt Germany-Norway link designed to compensate for the variability of German wind power generation by Norwegian PSPs and HPPs and the 500 megawatt Australia-Tasmania link needed to maintain the Tasmanian energy system (mainly operating at HPPs)
The great merit in the distribution of HVDC belongs to the same progress in the cables (since often HVDC are marine projects ), which for the past 15 years Brokers There was an available voltage class from 400 to 620 kV
However, the further spread is hampered by the high cost of transmission lines of similar caliber (for example, the world’s largest power transmission line Xinjiang-Anhui 10 GW per 3000 km will cost the Chinese about 5 billion dollars), and the underdevelopment of renewable energy-generating equivalent areas, ie The absence of comparable large consumers (for example, Europe or China) at a distance of 3-5 thousand km.
Including about 30% of the cost of power lines The PT lines are such converter stations.
However, if the transmission line technology appears simultaneously and cheaper and with less losses (which determine the maximum reasonable length?). For example, a transmission line with a superconducting cable.
An example of a real superconducting cable for the AMPACITY project. In the center of the formers with liquid nitrogen, there are 3 phases of the superconducting wire from tapes with a high-temperature superconductor separated by insulation, outside the copper screen, another channel with liquid nitrogen surrounded by a multilayer screen-vacuum thermal insulation inside the vacuum cavity, and outside – a protective polymer shell
Of course, the first projects of superconducting power lines and their economic calculations did not appear today or yesterday, but even in the early 1960s immediately after the discovery of “industrial” superconductors for the main ve intermetallic niobium. However, for classical networks without RES, there were no such SPs for power lines – both in terms of the reasonable power and cost of such transmission lines, and the point of view of the amount of development needed to put them into practice.
The superconducting cable line project from 1966 – 100 GW per 1000 km, with an explicit underestimation of the cost of the cryogenic part and voltage converters
] The economy of the superconducting line is determined, in fact, by two things: the cost of the superconducting cable and the energy losses for cooling. The original idea of using niobium intermetallides has stumbled on the high cost of cooling with liquid helium: the internal “cold” electrical assembly should be kept in a vacuum (which is not so difficult) and additionally surrounded with a cooled liquid nitrogen shield, otherwise the thermal flow at 4.2K will surpass the reasonable capacity of the refrigerators. This “sandwich” plus the presence of two expensive cooling systems at one time buried interest in the SP-LEP.
The return to the idea occurred with the discovery of high-temperature conductors and “medium-temperature” magnesium diboride MgB2. Cooling at a temperature of 20 Kelvin (K) for diboride or at 70 K (with 70 K – the temperature of liquid nitrogen – is widely mastered, and the cost of such refrigerant is low) for HTSC looks interesting. At the same time, the first superconductor is fundamentally cheaper today than the ones manufactured by methods of the semiconductor industry of HTSC tapes.
Three single-phase superconducting cables (and inputs to the cryogenic part in the rear Plan) of the LIPA project in the US, each with a current of 2400 A and a voltage of 138 kV, with a total capacity of 574 MW.
The specific figures for today look like this: HTSC has a conductor cost of 300-400 dollars for KA * m (i.e., a meter of conductor holding a kiloampere) for liquid nitrogen and $ 100-130 for 20 K, magnesium diboride at a temperature of 20 K has a cost of 2-10 $ for kA * m (the price is not fixed, like technology), titanium niobate – about $ 1 for kA * m, but already for a temperature of 4.2 K. For comparison , Aluminum wires of power transmission lines cost about $ 5-7 for kA * m, copper ones for 20.
The actual thermal losses of the AMPACITY cable are 1 km long and Capacity ~ 40 MW. In terms of the capacity of the cryocooler and the circulation pump, the power required to operate the cable is about 35 kW, or less than 0.1% of the transmitted power.
Of course, the JV cable is a complex evacuated product , Which can be laid only underground, adds additional costs, however, where the land under the power line is worth considerable money (for example, in cities), the power lines are already beginning to appear, even so, in the form of pilot projects. Basically, these are cables from HTSC (as the most developed ones), to low and medium voltage (from 10 to 66 kV), with currents from 3 to 20 kA. Such a scheme minimizes the number of intermediate elements associated with the increase in voltage in the main (transformers, switches, etc.) The most ambitious and already implemented power cable project is the LIPA project: three 650 m long cables designed to transmit a three-phase current of 574 MVA, Which is comparable to the overhead power line at 330 kV. The commissioning of the most powerful HTSC cable line today took place on June 28, 2008.
An interesting project AMPACITY implemented in Essen, Germany. The medium voltage cable (10 kV with a current of 2300 A with a capacity of 40 MVA) with an integrated superconducting current limiter (it is an actively developing interesting technology that allows to “naturally” disconnect the cable in the event of short-circuit overloads) is installed inside the city building. The launch was made in April 2014. This cable will be the prototype for the remaining projects planned in Germany for the replacement of 110 kV power transmission line cables with superconducting 10 kV cables.
AMPACITY cable is comparable to that of ordinary high-voltage cables.
Experimental projects with different superconductors for different current and voltage values are even greater, including several performed in our country, for example, testing an experimental 30-meter cable with Superconductor MgB2, cooling Given by liquid water. The cable for constant current in 3500 A and voltage of 50 kV created by VNIIKP is interesting by the “hybrid scheme”, where hydrogen cooling is simultaneously a promising method of hydrogen transportation within the framework of the idea of ”hydrogen energy”.
However, let’s return to RES. Modeling of LUT was aimed at creating 100% renewable generation on a continental scale, with the cost of electricity being less than $ 100 per MWh. The peculiarity of the model is in the resulting flows of dozens of gigawatts between European countries. Such power is almost impossible to transmit except for the DC power transmission line.
The LUT simulation data for the UK requires the export of electricity reaching up to 70 GW, with today’s links Islands in 3.5 GW and expansion of this value to 10 GW in the foreseeable future.
And similar projects exist. For example, Carlo Rubbia, familiar to us on the reactor with the accelerator driver MYRRHA, is promoting projects based on the world’s only manufacturer of magnesium diboride strands – as planned, a cryostat with a diameter of 40 cm (although it is already quite difficult for transportation and laying on the ground diameter ) Accommodates 2 cables with a current of 20 kA and a voltage of + -250 kV, i.e. With a total power of 10 GW, and in this cryostat it is possible to place 4 conductors = 20 GW, already close to that required by the LUT model, and, in contrast to conventional high-voltage direct current lines, there is still a large margin for increasing power. The capacity for refrigeration and hydrogen pumping will be ~ 10 megawatts per 100 km, or 300 MW for 3000 km – about three times less than for the most advanced high-voltage direct-current lines.
Rubbia’s proposal for a 10-gigawatt cable power line. Such a giant pipe size for liquid hydrogen is needed in order to reduce the hydraulic resistance and be able to put intermediate cryostats not more than 100 km. There is also a problem with maintaining a vacuum on such a pipe (a distributed ionic vacuum pump is not the wisest solution here, IMHO)
If further increase the dimensions of the cryostat to values typical for gas pipelines (1200 mm) and lay Inside 6-8 conductors at 20 kA and 620 kV (the maximum voltage currently used for cables), then the capacity of such a “pipe” will be already 100 GW, which exceeds the power transmitted by the gas and oil pipelines themselves (the most powerful of which transmit the equivalent of 85 GW thermal). The main problem may be connecting such a backbone to existing networks, but the fact that the technology itself is almost available.
It’s interesting to estimate the cost of such a line.
The building part will obviously dominate. Например, прокладка 800 км 4 HVDC кабелей в немецком проекте Sudlink обойдется в ~8-10 миллиардов евро (это известно, поскольку проект подорожал с 5 до 15 миллиардов после перехода с воздушной линии на кабель). Стоимость прокладки в 10-12 млн евро за км примерно в 4-4,5 раза выше, чем средняя стоимость прокладки газопроводов, судя по этому исследованию.
В принципе, ничего не мешает применять подобную технику для прокладки сверхмощных линий электропередач, впрочем, основные сложности тут видны в оконечных станциях и подключению к имеющимся сетям
Если взять что-то среднее между газом и кабелями (т.е. 6-8 млн евро за км), то стоимость сверхпроводника скорее всего потеряется в стоимости строительства: для 100- игаваттной линии стоимость СП составит ~0,6 млн долларов на 1 км, если взять СП стоимость 2$ за кА*м.
Вырисовывается интересная дилемма: СП “мегамагистрали” оказываются в несколько раз дороже газовых магистралей при сопоставимой мощности (напомню, что это все в будущем. Сегодня ситуация еще хуже — нужно окупить НИОКР на СП-ЛЭП), и именно поэтому строятся газопроводы, но не СП-ЛЭП. Однако по мере роста ВИЭ эта технология может стать привлекательной и получить бурное развитие. Уже сегодня проект Sudlink, возможно выполнялся бы в виде СП-кабеля, если бы технология была бы готова.
Что ж, будем следить за развитием этой отрасли.
P.S. Спасибо Виталию Сергеевичу Высоцкому за помощь с реальными цифрами стоимости сверхпроводников и дополнительными материалами!
