Mohammed Safiuddin and Robert Finton, Contributors
February 19, 2014 | 10 Comments
Instant delivery of electrical power from multitudes of inter-connected plants to a multitude of loads is figuratively and literally a "high wire balancing act." When a light switch is turned ON, the set of electrons required to flow through the filament of the bulb must be instantaneously balanced by an equal set of electrons produced at a generator. Similarly, when electrons are produced by a generator, they must either flow into a load or into a storage device connected somewhere to that grid. With such a complicated system, "The Interconnect" supplying power to millions of people is indeed a marvel of technology. But unlike natural gas, petroleum and nuclear materials, alternating current [AC] electricity is not a commodity.
Electrical energy, except in the electrostatic form, neither exists in nature nor can it be utilized directly. It is a means to transport energy found in fossil fuels, nuclear materials, flowing waters, blowing winds and solar rays to homes, buildings and factories. That is, AC electrical energy is a transportation medium and not a commodity in itself. Over the last one hundred years, the world has adopted electrical conductors as the means to guide the flow of electrons. It is an alternative to trucks, trains, and hydraulic or pneumatic pipes. Transmission lines resemble highways, with electrons replacing petroleum trucks or natural gas pipes. And just as fluids and gases flow from higher pressure to lower pressure, electricity flows from a higher potential at one end of a wire to lower potential at the other. However, unlike pressure in fluid and gas pipes, electric potential can be reversed instantaneously.
So as highways and rail lines need to be upgraded to keep up with ever changing populations, power grids should also be enhanced continually. And as the world tries to address its environmental challenges via wind and solar, a globalized grid structure [GREG] must be created through a carefully designed HVDC network.
Integration and Storage
GREG will require hundreds of long distance transmission lines, including undersea cables. HVDC has been shown to be the technology of choice for distances greater than 600km due to superior voltage quality, loss reduction and better power flow control.
In addition, to guarantee load balancing, energy storage facilities must be constructed at select points within the network. Existing storage technologies include pumped hydro, fuel cell, compressed air, batteries, superconductors, supercapacitors and flywheels. A centralized strategy places megaplants at optimal locations, allowing resource-sharing and economies of scale without relying on a parallel market (such as in hydrogen).
Installing energy storage is dependent on geography and geology. All available storage methods will be employed where appropriate (e.g. compressed air where there is a naturally occurring canyon). Hydroelectric power plants will need only to modify their dispatch schedules in order to serve a storage function. And pure pumped hydro storage plants, despite their high cost, offer massive potential in terms of energy retained. For areas with scarce water, modularized fuel cell megaplants can be placed at optimal locations, dependent on land-use rights and topology.
With greater extent of integration among global intermittent sources, the energy storage requirement will be lessened. University at Buffalo’s 2009 Wind Power Study, which places hypothetical 3MW turbines at select locations during an arbitrary sample month, offers an indication of the reduced storage requirement.
When operating separately, China, Russia and Scandinavia would have to store 6.4% of all wind energy generated. Together, the three regions need to store 3.9 percent, a reduction of 2.5 percent or 5.6 MWh/turbine-month.
For any extent of grid integration, an all-renewables grid will still require some amount of energy storage. Suppose, for example, that in the near future 20TW of renewable power capacity has been installed worldwide. At 20% average capacity, a 3% storage requirement suggests 900 million MWh deliverable monthly.
As the world’s nations continue implementing their own bottom-up strategies for transition to renewable energy, a centralized, top-down regulation and approval process must emerge to bind them together. While each nation will be responsible for funding its infrastructure, wealthier countries will need to support power industry reform in less well-off regions. Researchers in both industry and at universities must also come together across political bounds, combining the best elements of long-term energy planning into a unified global vision.
First presented at BIT’s 3rd New Energy Forum in Xian China, September 2013: Read the original text.
Dr. Mohammed Safiuddin is Research Professor Emeritus at the State University of New York at Buffalo and President of STS International, an engineering consulting firm in Amherst, NY.
Robert Finton is a Ph.D. candidate in electrical power systems at the State University of New York at Buffalo.