An article describing a cryogenic, superconducting "SuperGrid" that would simultaneously deliver electrical power and hydrogen fuel is featured in the July issue of Scientific American.com.
The August 14, 2003 power failure that affected 48 million inhabitants of New York, northeastern US and Ontario and an even more extensive blackout that affected 56 million people in Italy and Switzerland a month later--called attention to the susceptibility of our power grids to failure. A more fundamental limitation of our grid is that it is poorly suited to handle the relentless growth in demand for electrical energy and the coming transition away from fossil-fueled power stations and vehicles to cleaner sources of electricity and transportation fuels. The following is but a sampling of the information in the report, which you may want to read, to fully understand the problem and the authors solution.
The authors are part of a growing group of engineers and physicists who have begun developing designs for a new energy delivery system they call the Continental SuperGrid. They envision the SuperGrid evolving gradually alongside the current grid, strengthening its capacity and reliability. Over the course of decades, the SuperGrid would put in place the means to generate and deliver not only plentiful, reliable, inexpensive and "clean" electricity but also hydrogen for energy storage and personal transportation.
Super-Grid links crossing several time zones and weather boundaries would allow power plants to tap excess nighttime capacity to meet the peak electricity needs of distant cities. By smoothing out fluctuations in demand, the low-loss grid could help reduce the need for new generation construction.
The Super-Grid could go a long way, too, toward removing one of the fundamental limitations to the large-scale use of inconstant energy from wind, tides, waves and sunlight.
Engineering studies of the design have concluded that no further fundamental scientific discoveries are needed to realize this vision. Existing nuclear, hydrogen and superconducting technologies, supplemented by selected renewable energy, provide all the technical ingredients required to create a SuperGrid. Mustering the social and national resolve to create it may be a challenge, as will be some of the engineering.
Superconducting lines, which transmit electricity with almost perfect efficiency, would allow distant generators to compensate for local outages. They would allow power plants in different climate regions to bolster those struggling to meet peak demand. And they would allow utilities to construct new generating stations on less controversial sites far from population centers.
SuperGrid connections to these new power plants would provide both a source of hydrogen and a way to distribute it widely, through pipes that surround and cool the superconducting wires. A hydrogen-filled SuperGrid would serve not only as a conduit but also as a vast repository of energy, establishing the buffer needed to enable much more extensive use of wind, solar and other renewable power sources.
One of the goals in designing the SuperGrid has been to ensure that it can accept inputs from a wide variety of generators, from the smallest rooftop solar panel and farmyard wind turbine to the largest assemblage of nuclear reactors. The largest facilities constrain many basic design decisions, however. And the renewables still face tremendous challenges in offering the enormous additional capacity required for the next 20 years.
The concept is built on a foundation of fourth-generation nuclear power. Like all fission generators, however, generation IV units will produce some radioactive waste. So it will be least expensive and easiest politically to build them in "nuclear clusters," far from urban areas. Each cluster could produce on the order of 10 gigawatts.
Remote siting will make it easier to secure the reactors as well as to build them. But a new transmission technology will needed a--a Super-Cable--that can drastically reduce the cost of moving energy over long distances.
Three pilot projects now under way in the U.S. are demonstrating superconducting cables in New York State on Long Island and in Albany and in Columbus, Ohio. These cables use copper oxide-based superconducting tape cooled by liquid nitrogen at 77 kelvins (-196 degrees Celsius). Using liquid hydrogen for coolant would drop the temperature to 20 kelvins, into the superconducting range of new compounds such as magnesium diboride.
The Super-Cable that has been designed includes a pair of DC superconducting wires, one at plus 50,000 volts, the other at minus 50,000 volts, and both carrying 50,000 amps--a current far higher than any conventional wire could sustain. Such a cable could transmit about five gigawatts for several hundred kilometers at nearly zero resistance and line loss. (Today about a tenth of all electrical energy produced by power plants is lost during transmission.)
Because a Super-Cable would use hydrogen as its cryogenic coolant, it would transport energy in chemical as well as electrical form. Next-generation nuclear plants can produce either electricity or hydrogen with almost equal thermal efficiency. So the operators of nuclear clusters could continually adjust the proportions of electricity and "hydricity" that they pump into the Super-Grid to keep up with the electricity demand while maintaining a flow of hydrogen sufficient to keep the wires superconducting.
There is not a circuit-breaker design that can cut off the extraordinary current that would flow over a Super-Cable. That technology will have to evolve. Grid managers may need to develop novel techniques for dealing with the substantial disturbance that loss of such a huge amount of power would cause on the conventional grid. A break in a SuperCable would collapse the surrounding magnetic field, creating a brief but intense voltage spike at the cut point. The cables will need insulation strong enough to contain this spike.
Safely transporting large amounts of hydrogen within the Super-Cable poses another challenge. The petrochemical industry and space programs have extensive experience pumping hydrogen, both gaseous and liquid, over kilometer-scale pipelines. The increasing use of liquefied natural gas will reinforce that technology base further. The explosive potential (energy content per unit mass) of hydrogen is about twice that of the methane in natural gas. But hydrogen leaks more easily and can ignite at lower oxygen concentrations, so the hydrogen distribution and storage infrastructure will need to be airtight. Work on hydrogen tanks for vehicles has already produced coatings that can withstand pressures up to 700 kilograms per square centimeter.
Probably the best way to secure Super-Cables is to run them through tunnels deep underground. Burial could significantly reduce public and political opposition to the construction of new lines. The costs of tunneling are high, but they have been falling as underground construction and microtunneling have made great strides. Recent studies at Fermilab estimated the price of an 800-kilometer-long, three-meter-wide, 150-meter-deep tunnel at less than $1,000 a meter.
I realize that there will be comments urging more conservation, that we don't need hydrogen, and the amount of nuclear energy proposed is excessive and may not be needed at all. 1) I present this information as the viewpoint of three respected scientists as a positive suggestion as to how we might meet our energy needs. 2) I happen to agree with much of what they have said.
Renewables cannot possibly meet our energy needs in a timely manner--but we should continue to push them. The remaining choice is between coal and nuclear. I tend to favor coal with carbon sequestration, but that is more expensive than nuclear, so I see nuclear playing an important role. Generation IV nuclear should be very safe and have somewhat less waste to dispose of and I believe some sort of recycling is the only answer to that--large scale use of nuclear, as called for in this report, should be restrained until recycling is developed and demonstrated.
Conservation will take place when the price of energy is sufficiently high.
I don't think that fuel cell powered cars will be developed in time to meet shortages in liquid fuels, but hydrogen powered ICEs could complement plug-in hybrids and only minor retooling would be required--if only the hydrogen fuel tank problem could be solved. While automotive fuel cells are problematic, stationary fuel cells are already being used, with hundreds of installations in service providing very efficient production of combined heat and power and a number of installations for uninterruptable power supplies and back up power. Their method of distributing the hydrogen is very elegant and probably expensive, but it does accomplish the goal better than most proposals.
Power Grid for the Hydrogen Economy, Paul M. Grant, Chauncey Starr and Thomas J. Overbye, Scientific American.com, July 2006