The Oklahoma panhandle winds have a bad reputation. In the 1930s, they whipped its over-tilled topsoil up into the billowing black blizzards of the Dust Bowl. The winds drove individuals, Steinbeck’s dispossessed, away from their livelihoods and west, to California.
The panhandle’s steady winds today are a force for creation, not destruction. Wind turbines allow for the generation of electricity at rock-bottom prices. Unfortunately, the local electrical grid does not serve enough individuals to match this potential supply. The towns and cities which could utilize it are far away.
The Oklahoma Wind Electricity Project
Oklahoma’s wind electricity is supposed to be exported. Later this year, lawsuits permitting, work will start on a special cable, 1,100km (700 miles) long, between the panhandle and the western tip of Tennessee, where it will connect with the Tennessee Valley Authority and its 9m electricity customers. The Plains and Eastern Line, as it is to be known, will carry 4,000MW, which almost enough electricity to power Greater London. This will be made possibly by using direct current (DC), rather than the alternating current (AC) that electricity grids typically employ. Additionally, it will run at a higher voltage than such grids use—600,000 volts, rather than 400,000.
This long-distance ultra-high-voltage direct-current (UHVDC) connector will be the first of its kind in the U.S. However, the issue it helps with is pressing everywhere. If necessary, fossil fuels can be carried to power stations far from mines and wells, but where wind, solar and hydroelectric power are generated is not negotiable. And, while fossil fuels can be moved, this is not a desirable choice. In particular, coal is costly to transport. It is ideal to burn it at the pithead and transport the electricity thus generated instead.
The ubiquity rates of AC from the so-called “war of the currents” that accompanied electrification in the 1880s and 1890s. When electricity flows down a line as AC, energy travels as wave. There is no oscillation when it flows as direct current. While both work well, the deciding factor in AC’s favor in the 19th century was the transformer which allows AC voltages to be increased after generation, for more efficient transmission over longish distances, and then decreased again at the other end of the line, to supply customers’ homes and businesses. At the time, direct current had had no such breakthrough.
In the 1920s, one eventually came in the form of the mercury arc valve and AC was entrenched. Even the solid-state thyristor, a cousin of the transistor invented in the 1950s, provided no great benefits over the tens or hundreds of kilometers that power grids tended to span. Some high-voltage DC line were built, such as the the English Channel which links Britain and France. However, these were justified by special circumstances. For example, in the case of the Channel link, running an AC line through water creates electromagnetic interactions that dissipate a lot of power.
The balance of advantage shifts over transcontinental distances. As voltages increase, to push the current further, AC employs (and thus wastes) an ever-increasing amount of energy in the task of squeezing its alternations through the line. Direct current does not have this issue. In addition, long-distance DC electrical lines are cheaper to build. Specifically, the footprint of their pylons is smaller, because each DC cable can carry far more power than an equivalent AC cable. Admittedly, thyristors are not cheap—the thyristor-packed converted stations that raise and lower the voltage of the Plains and Eastern line will cost about $1bn, which is two-fifths of the total bill of the project. However, the ultra-high voltages needed for transcontinental transmission are still best achieved with direct current.
Asian countries are way ahead of America—China in particular. The construction of UHVDC lines is booming there. This boom is driven by geography. Three-quarters of China’s coal is in the far north and northwest of the country. Four-fifths of its hydroelectric power is in the southwest. However, most of the country’s people are in the east, 2,000km or more from these sources of energy.
The utilization of UHVDC in China began in 2010, with the completion of an 800,000-volt line from Xiangjiaba dam, in Yunnan province, to Shanghai. This contains a capacity of 6,400MW (equivalent to the average power consumption of Romania). The Jinping-Sunan line, which was completed in 2013, carries 7,200MW from hydroelectric plants on the Yalong river in Sichuan province to Jiangsu province on the coast. The biggest connector under construction, the Changji-Guquan link, will carry 12,000MW (half the average poewr use of Spain) over 3,400km, from the coal- and wind-rich region of Xinjiang, in the far northwest, to Anhui province in the east. This journey is so long that it requires 1.1m volts to push the current to its destination.
India is following suit with China—though its lines are being built by European and American companies, namely ABB, Siemens and General Electric. Hydroelectric power is carried by the 1,700km Northeast Agra link from Assam to Uttar Pradesh, one of the country’s most densely populated areas. When completed, and operating at peak capacity, it will transmit 6,000MW. At existing levels of demand, that is enough for 90m Indians. The country’s other line, which is also 6,000MW, carries electricity 1,400km from coal-fired power stations near Champa, in Chhattisgarh, to Kurukshetra, in Haryana, passing Delhi on the way.
While valuable, transcontinental links such as those in China, Brazil and India, are not the only use for UHVDC. Electricity does behave quite similar to a fluid—including fanning out through multiple channels if given the chance. This tendency to fan out is another reason it is difficult to corral power over long distances through AC grids—for, being grids, they are made of multiple, interconnected lines. UHVD connectors are usually referred to as supergrids, but they are rarely actual networks. Instead, they tend to be point-to-point links, from which fanning out is impossible. Therefore, some utilities are looking at them to move power over relatively short distances, as well as longer ones.
One such is 50Hertz, operating the grid in northeast Germany. Almost half the power it ships comes from renewable sources, especially wind. While the firm would like to send much of this to Germany’s populous south, and on into Austria, any extra power it puts into its own grid ends up spreading into the neighboring Polish and Czech grids.
This requires new technology—special circuit-breakers to isolate faulty cables and new switch gear—to manage flows of current that are not simply running from A to B. However, if it can be achieved, it would make the use of renewable energy sources much easier. When the wind blows strongly in Germany, but there is little demand for the electricity thus produced (at night, for example), UHVDC lines could send it to Scandinavian hydroelectric plants, to pump water uphill above the turbines. This will store the electricity as potential energy, ready to be released when needed. Similar to sources of renewable energy that are frequently inconveniently located, so, too are the best energy-storage facilities. UHVDC permits generators and stores to be wired together, which creates a network of renewable resources and hydroelectric “batteries”.
This project is reminiscent of a failed European one known as Desertec which had similar goals. However, Desertec began from the top down, with the grand vision of exporting the Sahara’s near-limitless solar power supply to Europe. Ideas today for Asian and European supergrids are driven by the real needs of grid operators.
Such projects—which are transnational as well as transcontinental—carry risks beyond the merely technological. Outsourcing a significant proportion of your electricity generation to a neighbor is to invest huge trust in that neighbor’s political stability and good faith. One reason Desertec failed is the lack of such trust. However, if trust can be established, the benefits would be great. Earth’s wind-blasted and sun-scorched deserts can, if properly wired up, provide humanity with a lot of clean, cheap power. The technology to do so exists, but whether the political will exists is the question.
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