Why we need to build a national HVDC electrical grid

The North American electrical grid could be described as the world’s most complex machine. It includes more than 200 000 miles of high-voltage transmission lines, can generate over a million megawatts, and serves all of the contiguous United States, most of Canada, and even a small part of Mexico. The grid is so reliable, that if it goes down in an area for more than a day, it is national news.

We rely on the grid for heating our homes, keeping our food cool, and powering our TVs and computers. For most of us, we can’t do our jobs without electricity. For those reliant on electrically powered medical equipment, a reliable power source is a matter of life and death. Electricity is such a critical component of modern life that we use the phrase “living off the grid” as a sign of extreme separation from society, as in, “The Unabomber lived off the grid in a cabin in Montana.”

Yet the grid is also killing us, silently and slowly. The grid’s number one source of power is the burning of coal, which is also the number one source of greenhouse gas emissions. In addition, coal burning emits a large number of other pollutants, such as mercury (a neurotoxin), sulfur dioxide, nitrous oxides, and particulates. Existing technology could reduce most of those emissions. However, according to data from the US Energy Information Agency, as of 2008 most of the coal-burning plants are 30–50 years old. Do we want to invest in keeping those dinosaurs functioning, or should we just replace them with something that is sustainable into the 22nd century?

One alternative energy source is nuclear power. Nuclear plants can be built anywhere and the fuel brought to them, just like a coal plant. Unfortunately, nuclear power has a number of drawbacks, chief among them negative public perception. The NIMBY (Not In My Back Yard) mindset makes it difficult to build nuclear plants near the cities where the power will be used. Also, nuclear plants are incredibly expensive to build, and the problem of storing the highly radioactive waste remains unresolved.

Another alternative is renewable energy, such as wind and solar. Wind and solar plants are also expensive to build, but they have very low operating costs, do not pollute, and are very unlikely ever to require the evacuation of a city. The main problem with renewable energy sources is that of location: The plant must be built where the energy is—where the wind blows or the Sun shines—and then the electricity produced needs to be transmitted to where the demand is. As can be seen in the maps from the National Renewable Energy Laboratory (NREL), it is windiest in the plains between the Rocky Mountains and the Mississippi River, and sunniest in the Southwest.

Currently, renewable energy projects are not built where the best resources are, but where the transmission lines are. For example, compare Washington State with South Dakota. As of 2010 South Dakota had installed 784 megawatts of wind turbines, compared with Washington’s 2357 MW. Those numbers come from the NREL, which considered only sites where the wind blows often enough for the turbines to be cost-effective and excludes inappropriate areas like cities and wilderness.

That Washington can capture three times as much wind power is shocking when one compares the energy capacity of the two states: South Dakota, the fourth windiest state in the US, has enough windy areas to support 882 000 MW worth of wind turbines, which could generate as much electricity as 410 nuclear plants, or 87% of all the electricity generated in the US in 2009. Those numbers take into consideration that the turbines only produce power when the wind is blowing. South Dakota has made use of less than 0.1% of its wind capacity, however, compared with about 13% for Washington.

The reasons that South Dakota has so few wind farms are that demand for electricity is low there and there are no transmission lines to export the power elsewhere. In contrast, demand is high in Washington, and high-voltage power lines run across the state, most of them built by the federal Bonneville Power Administration to bring hydropower to the population centers. Currently, almost no correlation exists between a region’s potential to develop wind power and the amount of wind power actually developed.

The key is to build a grid that can transmit power long distances efficiently, so that the states with significant renewable resources can export their power to the more populated states. The current grid, which can barely handle the power it currently is expected to transmit, is ill suited to moving vast amounts of electricity from one region to another. Blackouts, brownouts, and price spikes have recently occurred due to the grid being pushed beyond its limits.

Anyone who has driven in rush-hour traffic on the roadways in a major city has experienced a grid being pushed beyond its limit. The North American electrical grid functions much like the US highway system, but instead of cars and trucks, there are electrons carrying electrical energy. Instead of roads, there are cables. Instead of homes and businesses sending forth people and goods, power plants export electricity. To avoid the traffic jams at rush hour, commuters are urged to drive during off-peak hours, much as consumers are urged to run electrical appliances, such as dishwashers and washing machines, at night, when electrical loads are lighter. Like taking the bus or carpooling to cut back on the number of vehicles on the road, people can use more efficient lighting and appliances, which reduces the strain on the grid.

One major difference between automobile traffic and the electrical grid is that grid operators constantly monitor the system. They make sure that at any given moment the amount of energy entering the grid is exactly equal to the amount that is being consumed. If the amount of electricity that is being consumed looks like it will exceed the amount that the grid can supply, the grid operators “shed load” rather than allow gridlock, either by shutting down a few large users, such as an aluminum smelter, or by imposing rolling blackouts, where power is temporarily cut in various areas to avoid a total blackout of the entire power system. Despite those precautions, the system does occasionally suffer an uncontrolled breakdown and a large number of Americans can find themselves without power for days.

Much like the Eisenhower Interstate Highway System improved interstate travel in the US, an overhaul of the national electrical grid could improve the US’s nationwide power delivery system. Prior to about a half century ago, local and state governments built roads to meet local needs. The federal government played little role. With passage of the Federal-Aid Highway Act of 1956, however, the federal government took responsibility for the planning and funding of an interstate road system, which is now the backbone of the US transportation network. Having taken approximately 30 years to build, it must be improved and maintained indefinitely.

From the beginning, renewable energy has driven new technology developments in electricity transmission. In 1896 Nikola Tesla and George Westinghouse built the first “long-distance” system. It relied on alternating current and transformers to transmit electricity to Buffalo, New York, from a hydroelectric generator located at Niagara Falls some 20 miles away. If Tesla and Westinghouse examined today’s high-voltage alternating current (HVAC) system, they would recognize most of its components.

A century ago, when the modern electrical grid system was being built, it was a marvel of modern technology and efficiency. For transmitting power from the outskirts of a city to homes and businesses, it works very well. But for transmitting renewable energy thousands of miles from the windy and sunny states to where most people live and work, the model is inefficient, expensive, and unstable.

High-voltage direct current current

The solution is a national high-voltage direct current (HVDC) system. Compared with the current HVAC system, HVDC is cheaper, stabler, and more efficient when used to move large amounts of power long distances. HVDC has been around for more than a century, but recent improvements in the technology have made it much more competitive with HVAC than it was even 10 years ago.

A new HVDC electrical grid would not replace the current system, however, but rather augment it for long-distance transmission, much the way our interstate freeways augment our local roads and state highways. The electricity that arrives in our homes and offices would travel along the same wires; only it might come from a distant wind farm or solar plant, rather than a nearby coal or nuclear plant. No home appliances or factory equipment would need to be replaced.

Any one of the seven windiest states (Texas, Kansas, Nebraska, South Dakota, Montana, North Dakota, and Iowa) has enough wind power potential to generate at least half of the electricity that was used in the nation in 2009. Furthermore, the needs of the entire US could be met with a 14 000-km² solar power plant (about 4% the size of New Mexico) operating at 11% efficiency (currently available solar panels have at least that efficiency) for seven hours a day.

Though locating a huge number of wind turbines or solar panels in any two states could generate enough energy to power our electrical grid, such a system would not be robust. Even in windy places like Kansas, the wind doesn’t always blow. Nor does the Sun always shine in Arizona. But the wind is almost always blowing somewhere and the Sun is almost always shining somewhere. That’s why geographical diversity is so important.

Also important is source diversity: If the wind isn’t blowing, the Sun will be shining, or the rivers running, or the waves crashing. By getting our power from many different types of renewable sources located across the whole country, the system could operate 24/7, as coal-fueled and nuclear power plants do. For that to work, the whole country needs to be able to share power, so when the renewables in one region aren’t producing, the renewables in another region can compensate.

The current North American electrical grid comprises four regions: east of the Rockies, west of the Rockies, Texas, and Quebec. Due to the nature of how the grids operate, the current AC grid cannot transmit power across those regions. (Significant power is transmitted from hydro projects in Quebec to New York, but that is done using HVDC.) Given that wind power produces disproportionately at night in the eastern region and solar produces entirely during the day mainly in the western region, any system using renewables that is going to provide baseload power—or the minimum required—must operate across the regions. That requires a national HVDC grid.

Like the Interstate Highway System, a national electrical grid will require federal leadership to plan, fund, build, and operate it. The level of risk and investment is too large to expect the market to create it: Building the grid will cost more than $100 billion and take decades. Additionally, the benefits in economic development and greenhouse gas reductions are enormous for the country as a whole, but may not be of any value to a private investor. Although companies such as Clean Line Energy are trying to build HVDC transmission lines, so far the challenges of raising the capital and getting the permits have delayed progress. And even if all of the HVDC lines proposed by the private sector are built, they will not replace the power produced by all of the coal plants that must be retired.

A national HVDC electrical grid is not a panacea but one step in the process of weaning our civilization from its self-destructive addiction to fossil fuels.

Andy Silber is a new product program manager at Cypress Semiconductor Corp. As he recounted in his first Points of View column , his interest in energy policy began in high school and turned to activism in 2001 when Dick Cheney’s Energy Task Force began its work.