The wind is an inexhaustible source of energy. But the full potential of wind cannot be developed unless engineers understand the problem they are solving. A brilliant engineer will come up with a brilliant solution, but if the solution is for the wrong problem—that would be a wasted opportunity.
Wind engineers are doing a brilliant job developing solutions that have vastly improved the performance of wind turbines and the generators connected directly to the turbines; as well as in understanding the behavior and availability of wind resources. But it is time for Engineers to turn their creative efforts toward solving the problem of wind energy’s intermittency.
Wind technology faces three major challenges:
- Cost — manufacturing, shipping and installing wind turbines will require a large up front capital investment, but after the initial investment is made, the wind is free.
- Transmission of power to the consumer — the electricity produced by a wind turbine needs to be connected to the electric power grid (transmission lines, etc.) before the electricity can be delivered to homes and businesses, but the best locations for capturing wind power are not always conveniently located near population areas. Construction of new roads and transmission lines in remote areas will cost more than the wind turbines. A massive federal public works project on the scale of the U.S. Interstate highway system is needed to provide renewable energy generators with the transmission access required to deliver renewable electricity to the nation.
- Energy storage — the electric power grid requires a steady, predefined voltage. Wind is not steady or predictable. However, if the wind’s energy can be captured and stored, then the electric grid can draw from the stored energy to generate a steady flow of electricity when needed. The best way to store wind energy is to use the electricity produced by the wind turbine to pump water uphill to a reservoir and then use the water pressure in the reservoir to produce conventional hydroelectric power when needed. Another way to store the wind’s energy is to use the power generated by the wind turbine to run an air compressor and then store the compressed air. The compressed air is then used to drive a conventional gas turbine (providing over 50% of the gas turbines power), which generates a steady, predefined voltage for the electric grid. Other types of energy storage are possible, such as hydrogen gas, flywheel and battery storage.
Power is blowing in the wind, and harnessing that power can bring clean renewable electricity to homes and businesses across America. But the trouble is also blowing in the wind. Grid-connected wind energy today is little more than a scene on a Hollywood movie set—a story that people want to believe, and the producers hope to make money from.
People see electricity flowing and they say, “Look it is real.” …their imagination has been captured, very much like the effect intended by the perfect camera angle scene on a movie set—it LOOKS REAL because it is a real set, made of real material, but there is nothing behind the set, where the camera angle has hidden the true nature and purpose of the set.
Wind energy performs poorly if it is used in a way that cannot exploit its full potential—wind energy performs poorly when connected directly to the electric grid.
Yes the wind electricity is real; the engineer’s solution has worked just like it was supposed to for the problem that the engineer was given to solve—renewable wind-generated electricity on the grid—problem solved!
Wait. Was that really the problem? Obviously, it was part of the problem, but was that the whole problem? Let’s step back and look at the bigger picture. What was the purpose in the first place? Was there a shortage of electricity? Was the grid going dead?
Some areas of the power grid have experienced brownouts and blackouts, but we were told that the grid failures were caused by overloading the transmission lines — demand exceeded the maximum load for the wires — in other words, a lack of transmission capacity, not a lack of electric power. And, yes we are told that more electric power plants are needed as demand increases. But will grid-connected wind provide reliable “always available” electricity to fill the need for future electricity supply?
Recently, we have been told that wind-generated electricity will free us from oil dependence. But that can’t be true, because our nation’s electric power companies do not rely on oil to generate electricity, and we don’t use electricity to fuel our cars.
Then why do we want wind-generated electricity on the grid?
For one reason only: to replace coal as the source of fuel for electric power generation.
America has more coal than the Middle East has oil. Coal generates 50% of America’s electricity today and produces over 30% of America’s carbon dioxide emissions. There is no shortage of coal within the next 100 years. Replacing coal-generated electricity is an environmental issue; we are not running out of coal. Coal plants release mercury and other pollutants into the atmosphere, along with massive quantities of carbon dioxide.
Wind energy does not produce air pollution.
The Hollywood drama surrounding the politics of wind energy is focused on carbon dioxide and global warming. It is a fascinating drama, but it is not about energy independence.
Wind energy will reduce carbon dioxide emissions, but only if the wind really does REPLACE coal-generated electricity. And that may not happen.
The electric grid is designed to provide and support “always on always available electricity on demand.” Think about it—that is an amazing technological accomplishment. But it comes with a catch; you can’t have it both ways. You can’t expect the grid to support intermittent sources of electricity like wind, and at the same time continue to provide you with a constant dependable source of electricity. What is the grid to do when the wind stops blowing or fails to start blowing when you want your electricity?
Is there a solution? Yes, energy storage, but that would cost money — a major investment in new infrastructure for energy storage and transmission. Wind energy advocates like to quote the “cost of wind-generated electricity” without including the capital cost of constructing transmission lines (or transmission power losses over long distances) and the cost of energy storage. When such costs are included, the real cost of the wind exceeds the real cost of nuclear energy. So then, if eliminating carbon dioxide is the goal, why not build more nuclear power plants? (Hint: Nuclear energy is an abomination unto the earth goddess Gaia).
Unfortunately, there exists a ready-made Hollywood type of solution, a short-cut that allows wind engineers to skip the important energy storage step and connect their wind-generated electricity directly to the grid (if and when transmission lines are available). This “short-cut” takes advantage of a feature of the grid that is intended for entirely different use. By tweaking the grid system to exploit this feature wind investors can make money and the electric company can comply with the politician’s demand to use wind, but it will not REPLACE coal electricity or the carbon dioxide released into the atmosphere by the coal generators.
This feature of the grid, which will allow intermittent electricity to be connected and distributed without interrupting the grid, exists for the purpose of handling varying demands throughout the day. Electricity demand increases and decreases over a 24 hour period, kind of like rush hour traffic. There are predictable periods during the day when demand increases dramatically, called peak periods. At night, after most people are asleep, the grid is subjected to the lowest demand.
The utility companies will often use small generators to quickly add electricity during the peak period as needed, and wind would work well as a substitute for these small generators if the wind was predictable, but it isn’t.
A significant percentage of the available electric power throughout the day is called “baseload” power. Much of the baseload power is produced by large coal (and nuclear) powered generators. Baseload power is the minimum amount of power that a utility company makes available to its customers. This minimum is calculated to ensure that enough spare capacity is available at all times. When demand is lower than the spare capacity, the unused electricity is simply unused. But it is still generated; coal is still burned—the electricity is available whether it is used or not. Without this “wasted” spare electricity, we would too often be left in the dark, or without TV, refrigerators, and computers… and microwave ovens and air conditioners, washer and dryer… on and on, Americans love their electric appliances.
A good analogy of how the grid operators (along with utility generators) ensure that enough electricity is always available is found in the example of an “all you can eat” buffet restaurant (or any restaurant). How do restaurant owners plan for unpredictable customer demand? The restaurant simply plans to throw away a predetermined percentage of food. When was the last time you went to a restaurant that was out of food? The left-over fresh food is not kept to be served the next day—it would not be fresh. The cost of the food served and the food thrown away is averaged into the price charged to the hungry customers who visit the restaurant at varying times throughout the day, with the highest volume of customers coming to eat during the normal mealtime hours.
The customers of electric utility companies are paying for the “spare available electricity” whether it is used or not, just like restaurant customers pay for the perfectly good food that winds up in the dumpster behind the restaurant every night. If however, the restaurant has an unexpectedly busy night, less food goes into the dumpster and more profits into the Restaurant’s bank account. The Electric Utility companies also make more profit during higher than expected demand. Profits and losses are averaged over the month—the rate that customers are charged is determined by the projected average cost of electricity.
Along come the politicians, demanding that utility companies buy electricity generated from wind. The utility companies explain to anyone who will listen that this isn’t going to work. The environmental groups put on the pressure, and the politicians agree to pay the utility companies to take the wind energy. The Utility companies say, OK we’ll take your money, and they set up their systems to replace coal-generated electricity with wind-generated electricity (when the wind blows), and throw away the coal-generated electricity, in the same way, they “throw-away” the unused spare electricity that is available for unpredictable demand.
What! What do you mean throw away the coal-generated electricity? Wouldn’t that mean carbon dioxide was still produced? Yes, that is exactly what it means. Well, then why not turn off the coal generator while the wind is blowing? Hmmm, have you ever seen a coal plant’s steam turbine generator? They are huge, and they require massive boilers and giant furnaces. Think of it like trying to stop a train that is moving at 100 miles per hour. How long do you think it took to get the train up to that speed? Large steam turbines can take over ten hours to warm up. You can’t stop the train on short notice, and you can’t turn the giant coal-powered turbine generators off and on at short notice either. The size and speed of the generators is one reason why the cost of electricity is as low as it is. The small generators that can be turned on and off quickly cost much more per kilowatt-hour, it is simply a matter of economies of scale.
When the wind-generated electricity enters the grid, the grid operator redirects an equal portion of coal-generated electricity off the grid (in other words, the coal-generated electricity is “thrown away” like “unused” spare electricity) — and the coal keeps on burning and the carbon dioxide keeps pumping out the smokestack.
With the wind connected directly to the system, green electricity is flowing on the grid; but the wind has not really reduced the total carbon dioxide produced by coal-powered generators.
It’s a good article, generally, and it makes some points that need to be better understood by the public. But I think it overstates the problems with grid integration of wind power somewhat — at least for low levels of wind penetration.
In particular, it seems to suggest that when wind farms are supplying power to the grid, coal-fired plants that could otherwise have supplied the power continue to operate, with the now excess power simply dumped into resistor banks. The first part is usually true, in that most coal-fired plants are designed and operated as baseload plants and rarely shut down. However, dumping power into resistor banks is an emergency measure that is hardly ever required. When it is required, it’s invariably due to sudden loss of load due to a tripped circuit. As far as I know, it’s never been needed as a result of a surge in power delivery from a wind farm.
The reason that baseload coal-fired plants don’t need to shut down (or dump power) is that they never account for 100% of supply to the grid. There is almost always a buffer of other generators in operation that can be shut down before it becomes necessary to touch the baseload plants. Those other generators are normally gas combustion turbines or diesel generator sets that aren’t much bothered by cycling. These are units with lower capital costs and higher fuel costs than the baseload plants, and it’s the fuel savings in these plants that are used in figuring the economic returns of wind farms. In fact, studies of wind power often include not just the direct cost of fuel saved, but the indirect savings from lowered fuel consumption on the price of fuel to all other users. Depending on the elasticity coefficients employed in the pricing models, wind power can look like a very good social economic investment.
Another caveat about coal-fired power plants is that they need not be designed strictly as baseload plants. It’s really just the boilers that are damaged by thermal cycling. It’s possible—and maybe even standard, at least in newer plants—to have one boiler supplying several individual turbines. Plant output can be quickly reduced by shutting off steam to one turbine, without shutting down the boiler. In areas supplied by this type of load-following coal plant, it’s harder to justify wind farms in strictly economic terms, because the fuel displaced by wind is cheap coal, rather than relatively expensive natural gas or diesel.
Despite the above, the general thrust of the article is valid. As the level of wind power penetration increases, the problem of maintaining sufficient levels of dispatchable power for backup intensifies. At some point, it does indeed become necessary to deploy energy storage units—or other forms of dispatchable sources and loads—to deal with the irregular wind supply.
—Roger Arnold October 30, 2008
Spinning Reserve-Fossil Fuel Based Generating Plants:
1. Coal Based:
Typically, there are two scenarios of a Coal-Based unit supposed to be on a spinning reserve. One, the unit is on turning gear. Other, the unit is on rated speed ready for synchronization. When the unit is on turning gear, the variable cost or the fuel cost is nil. But when a unit is on rated RPM, say 3000, for 50 Hz Machines, it is incurring fuel cost as well as substantial auxiliary loads. In the true definition of spinning, the unit should be hooked with transmission within 10 minutes. A unit on turning gear would take more than an hour to be ready for delivering power, while the one on rated RPM would be synchronized within 10 minutes. But I have yet to see any Regulator giving the benefit of fuel cost for the unit that is spinning. As far as I know, there is no separate account for the costs that are incurred during spinning. Plant Owners have to account for these in the overall operating expenses, which is not reflecting the actual specific fuel consumption and the fuel cost per kWh delivered.
2. Gas Based CCGT:
The unit can be on Turning gear. Or it can be on FSNL(Full Speed No-Load). From turning gear it would take more than 90 minutes, while from FSNL it can be synchronized only in open cycle mode within 10 minutes. So, truthfully, a CCGT can not contribute to the spinning reserve. Only a simple cycle unit can.