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Lots of Volts
Energy is hot again; is this for real or is it another false start? It’s beginning to look as though maybe this time we are getting serious about alternative sources of energy, particularly wind and solar. Also, years after Chernobyl and Three Mile Island and no new nuclear power plants in the U.S., nuclear power is again being pushed as being a safe alternative. President Obama has proposed billions of dollars be spent on alternate energy sources and on a total overhaul of our power delivery system, the objective being a "smart" grid. I forget the cause; was it a tree falling on a power line? Whatever the cause, the power blackout that extended over several states a couple years ago exposed the fact that there is a serious problem when a relatively minor incident can bring down such an extensive power grid.
If wind and solar energy are introduced in quantities necessary to make a significant dent in our reliance on coal and oil, what happens if the wind doesn’t blow or the sun doesn’t shine? I imagine weather forecasting will play a more important role in power companies’ plans to respond to sudden losses of energy input. Hopefully, they will have sufficient reserve generating capacity that they can bring quickly online should an unexpected sudden lull in windiness occur. This is just one of the reasons we will need a "smarter" electrical power grid than we have now.
I’ve seen many articles on power but found an article by Peter Fairley in the June issue of Discover magazine to be especially informative and understandable. According to the article, Obama’s goal is that a fourth of all our electrical power will be supplied by alternate renewable energy sources by the year 2025. I must admit to being skeptical about any grand program scheduled to be completed years after a politician’s term in office is over. Kennedy’s man on the moon is one of the few such ambitious programs I can recall that actually was achieved within the stated time frame.
At any rate, let’s look at the current state of our power grid and what is needed to handle any large scale power inputs from wind and solar energy. First, where does the wind blow and the sun shine? Our recent prolonged periods of crummy weather here in New Jersey certainly indicate that we won’t be a player in the solar energy game. However, in New Jersey we do have plans for future offshore wind turbine "farms". Offshore locations along both east and west coasts of the U.S and the Great Lakes offer what the article terms "outstanding" potential sources of wind power. However, building and maintaining wind turbines in a marine environment certainly is more challenging than land-based options.
Aside from scattered locations throughout the U.S., the land areas with highest potential for wind energy lie in a broad band of west central states from Texas up to Canada, with regions varying from "fair" to "superb" in wind potential. Solar energy certainly would have more potential in the western desert regions and some southern states. All this means that power companies will have to transport the energy over hundreds or thousands of miles to reach consumers in the most populous regions of the U.S. What we have now is a bunch of power companies interconnected by all those high voltage power lines you see traversing your areas but to transfer large amounts of power over thousands of miles is not a simple matter.
I was surprised to find that all these local systems that exchange power are gathered together in what are just three distinct grids in the U.S., the Eastern, Western and Texas "interconnects". (I’m not sure where Alaska and Hawaii fit into the picture. I’m assuming they’re on their own, power-wise.) According to the Discover article, there are only a handful of "transfer stations" that can move power from one of these three grids to another. It isn’t just a matter of throwing a switch or two and directing the current from one grid to the other. Within each of the three grids, the electricity is AC, alternating current, in which the electrons are moving back and forth at 60 cycles per second.
One problem is that the AC electrons in one grid are not in sync with the electrons in the other grid - you can’t simply feed out-of-sync alternating currents together. To transfer power from one grid to another, the transfer station converts the AC to DC, direct current. In DC, the electrons move in one direction; they don’t jiggle back and forth as in AC. (Your computers and cell phones run on DC.) After the transfer station converts the power to DC, it has to then generate a new stream of AC that is in sync with the receiving grid. Don’t ask me how this is done; I’m a DC person. Anything that moves in waves confuses me.
Whatever, some AC power is used to effect the transformation from AC to DC and some DC power is used to transform the current back to AC in sync. Transferring large amounts of power is not a simple proposition. The article quotes Michael Heyeck of American Electric Power as likening our present system to our overloaded and congested road network of the 1950s before the advent of President Eisenhower’s Interstate Highway System.
What Heyeck and others envision is the power delivery equivalent of the Interstate Highway System. The Interstate power highways would be very high voltage lines that would carry wind power generated, say, in Texas or northern plains states thousands of miles to California or New York. These power super highways would have on/off ramps at selected intervals to feed or pick up power to or from regional grids. At least two approaches for the power super highways are being considered. One is a very high voltage DC (HVDC) approach; the other is a very high voltage AC approach (HVAC). The DC approach is more efficient for very long distance transmission with less resistance to current flow than with AC. The DC super highway would have converter stations analogous to the transfer stations but the converter stations would be hundreds or thousands of miles apart. An HVDC line from James Bay in Quebec has been carrying power to New England over some 920 miles (1480 kilometers) since 1990.
What is "high voltage" today? Let’s go to China, which is already building or using both HVAC and HVDC. China is now building an 800 thousand-volt DC line from one of its huge western power projects to Shanghai. This HVDC line is expected to provide power to 31 million people! China isn’t ignoring HVAC, having just set up HVAC lines with a voltage of merely 1 million volts! The power carrying capacity of a line goes up with the square of the voltage; hence the push to such high voltages.
One concept proposed by power people here in the U.S. is a network of some 19 thousand miles of 765 thousand-volt AC lines crisscrossing the country at an estimated cost of $60 billion dollars. Such a super highway HVAC grid would be laid over existing power grids and appropriate connections made with substations stepping down voltages for local transmission and ultimately down to the 110- or 220-volt levels delivered to individual homes. With such a system in place, power engineers anticipate that 20 percent of our country’s power needs will be satisfied by wind power.
While the more efficient high voltage DC (HVDC) approach is preferred for long haul transmission (DC encounters less resistance to current flow than AC), a disadvantage is the need to convert from AC to DC and back to AC. There are power losses in the conversions and the large scale switches and other power equipment are costly. Chances are the ultimate grid will involve of mix of DC and AC.
But, again, what happens when the wind doesn’t blow? Today’s answer to a dip in power is to bring on online reserve generating or storage capacity. When I worked on batteries for the old Bell System, we prided ourselves that the telephone system worked when the power failed thanks to enough energy stored in batteries to keep the system working until backup generators could be brought up to speed. Some other energy storage options include compressed air, pumping water uphill to be used to generate hydroelectric power when it flows back down, spinning flywheels and, of course, nuclear power as both a backup and continuing power source.
Obviously, it will take a considerable amount of "smarts" to manage such a heavy duty system but the individual consumer or business will also play a role. At the individual consumer level, let’s say you have a plug-in hybrid or battery-powered car. You and the power company are both going to be happier if you charge up your car at night when power demands and cost are both lower. In emergencies, the power company might even want plug-in car owners to help out by feeding some of the energy stored in the car batteries back into the grid. Today, there aren’t enough plug-ins to make a difference. However, in a future green society loaded with millions of GM Volts (am I dreaming?) or equivalent, power fed back into the grid might be enough to save the day (or night).
Such scenarios require a smart grid capable of smoothly blending power of varying types from different sources back into that 60-cycle AC system! The Discover article cites the case of Xcel Energy, an electric utility that has begun to roll out a smart grid for its customers in Boulder, Colorado. Initially, the program involves something relatively simple, yet effective - a smart meter and a customer’s natural tendency to want to save money, a tendency probably magnified in these troubled financial times.
At first, the meters will be in touch with the power company every few seconds reporting the consumer’s current power usage. As data accumulate, the power company will be able to anticipate will be able with some degree of certainty a consumer’s upcoming power consumption. Within a few months, the Boulder consumer will be also be able to access his or her current power usage, as well as information from the power company such as expected power generation by the wind farm feeding alternate energy to the utility. The consumer can then plan on doing laundry or the dishes when the cost of power is lower. Eventually, the smart meter, combined with the Internet and appropriate switches and connections, will allow the power company to monitor and even control the operation of certain electrical devices in the consumer’s home under optimum and lower cost conditions.
The consumer may also be able via the computer to put the house in a vacation power-saving mode whenever the consumer leaves the house. The power company is most interested in situations of peak power demand, when it’s in most danger of suffering an overload and has to be sure there’s have enough generating capacity to meet the demand. For the consumer, it’s also the time when electricity costs the most to use. In a test in the state of Washington, more than a hundred homes were outfitted with smart meters and wireless switches on their water heaters and thermostats. The switches were programmed to turn off power in periods of peak demand and, sure enough, the average peak power consumption by these customers went down by 15 percent.
Thinking about it, I certainly admit to being lax in my own use of power. I have a programmable thermostat but it’s a lot of trouble for an old guy to remember to turn it down (or up in the summer) every time we leave the house. If there was a simple button I could push on my way out to put us in a vacation mode, having a Big Brother smart grid watching over me would be a great idea.
Next column on June 11.
Allen F. Bortrum