|The Naked Truth about Windfarms, Wind Energy, and CO2 Emissions.
|WINDPOWER IS COSTLY, UNRELIABLE, AND NEEDS TO BE BACKED UP.
|Responding to Issues Raised during a Conversation about Wind Energy With a Senior State Legislator - by Glenn Schleede
Recently, a local government official met with a senior state legislator to discuss concerns about proposals to install wind turbines in the local government official’s county. The state official made claims about the potential for wind energy that seemed incorrect. It seems possible that the local and state officials were “talking past each other.” However, this paper has been prepared to help illuminate some of areas of potential misunderstanding and to address specifically some of the claims made by the state legislator.
Part A: Concepts and Definitions
First, it seems desirable to get some terms and concepts straight. You may want to skip over some of these and then refer back if necessary -- either now or for future discussions.
1. Generating capacity. The generating capacity of a generating unit is measured in kilowatts (kW) or megawatts (MW). Generating “capacity” refers to the maximum amount of electricity output at any given instant.
2. Generation. Generation refers to the electricity output of a generating unit over some period of time and that output is measured in kilowatt-hours (kWh) or megawatt-hours (MWh).
3. Capacity factor. A generating unit’s capacity factor is a percentage determined by dividing the output (in kWh) by the capacity (in kW) times the hours in a period. For example, a 1,500 kW generating unit that produced 9,198,000 kWh during a year had a capacity factor of 70% (i.e., 1,500 kW capacity x 8760 hours per year x .70 = 9,198,000 kWh).
4. Types of generating units. Generating units come in many types, usually described by their technology and energy source. The most common types now in use include the following:
a. Steam-electric. A turbine-generator is driven by steam and the steam is produced by either coal, residual oil, natural gas or nuclear energy (or possibly by wood or “biomass”). These units tend to have high capital costs. On a Btu basis, the cost of coal tends to be lowest, residual oil next and natural gas highest.
b. Hydroelectric. Waterpower drives a turbine-generator.
c. Simple cycle combustion turbine (CT). A turbine (hooked to a generator) is driven by hot gasses produced from natural gas or distillate oil. These are referred to as simple-cycle turbine generating units. (The same basic principle as an aircraft jet engine.) Capital costs tend to be low and fuel costs – natural gas or distillate oil – high. Efficiency tends to be low.
d. Combined cycle (CC). These incorporate one or more simple cycle combustion turbines (CT) configured with a heat-recovery boiler that permits capturing the hot exhaust gasses from the CTs and using them to heat water to produce steam that is used to drive a steam-turbine. Thus, electricity is produced by both the generators powered by the CTs and the steam turbine. (Fuel costs – natural gas or distillate oil -- tend to be high but efficiency is also high. In fact, these are the most efficient units now commercially available.)
e. Internal combustion (IC). These are relatively small units using the rough equivalent of an automobile or truck engine to produce the power to spin a small turbine-generator.
f. Wind turbines. These use wind driven blades to produce electricity from a turbine-generator. (Note: Wind turbines have low “incremental” costs but high “fixed” costs. See definitions in paragraph A. 8., below.)
5. Generating unit efficiency. A generating unit’s efficiency (commonly called “heat rate”) is determined by dividing the value of the energy input in Btu (British thermal units) by the kilowatt-hours of output. (This doesn’t apply to hydro or wind-powered units.)
6. Electricity demand or “load.” The amount of electricity demanded by customers varies by minute, hour of the day, day of the week and season -- as lights, air conditioners and other appliances are turned on or off, machines started up or shut down, etc. Electricity demand or load at any instant is measured in kW (or MW). In many areas of the US, demand or load tends to be lowest on cool weekend nights and highest on hot weekday afternoons when most people are working and most machines and air conditioners are running.
7. Balancing electricity system supply and demand. Electricity must be produced as it is used by electric customers (“demand”) because electricity can’t be stored in any significant amounts. Generating units that are on line must be “ramped up” (output increased) or “ramped down” (output decreased) as demand changes. If demand drops significantly some unit(s) will be taken “off line” or if demand increases, other units may have to be brought on line.
The grid (called a control area) to which customers and generating units are connected must be kept in balance constantly (supply-demand, voltage, frequency, load on transmission lines, etc.). This task that is accomplished by the grid managers (controllers) in part by automatic controls, in part by computer controls and in part by manual controls.
8. Types of service in which generating units are employed. There are three general types of service and the way that various types of units are employed is determined largely by:
· The incremental cost of running the unit (i.e., the costs incurred over and above those “fixed” or “sunk” costs – such as the capital cost of the unit -- that would be incurred whether or not the unit is running. Incremental costs consist primarily of fuel cost.
· The time it takes to get the unit running and producing electricity that is synchronized with the electric system to which it is connected. For example:
· A hydro unit can be started up or increased in capacity very quickly.
· A combustion turbine (and the combustion turbine elements of a combined-cycle unit) can be started up and brought on line in roughly 15-30 minutes.
· A steam electric unit requires several hours to heat up the unit and bring it on line.
a. Base load. Recognizing the above, the generating units used in “base load” service are usually, first, hydro units (because they have very low incremental costs and their output is highly controllable); second, nuclear units; third, coal-fired units; and fourth, oil or gas-fired steam electric units. In some cases, natural gas-fired combined cycle units are run in base load service because their high efficiency tends to hold down the incremental fuel costs even though that fuel is almost always more expensive than coal. Units run in “base load” service may have capacity factors in the 75% to 90% range.
b. Intermediate load. Intermediate load refers to the electricity demand that builds up during the day and which requires bringing additional generating units into service. Combined cycle units may be run to serve “intermediate” load (if not already employed in base load) because they can be brought on line or taken off line faster than steam electric units and they are more efficient than simple-cycle CTs. Older, less efficient steam-electric units are also often run in intermediate load because they have higher incremental costs than newer, more efficient steam-electric units but lower incremental costs than CTs. Intermediate load units may have capacity factors in, roughly, the 10% to 70% range.
c. Peak load. Units in peak load service (when electricity demand is highest – such as hot weekday afternoons when many air conditioners are running) tend to be the simple-cycle combustion turbines (CTs) and, when necessary, the internal combustion units that run on distillate oil or, sometimes, natural gas. The incremental cost of running these units is high because of relatively high fuel costs and low efficiency (or high “heat rate”; i.e., the Btu required to produce a kWh of electricity). These units may have capacity factors in the 2% to 5% range.
9. Dispatch Order. The order with which units of all types are brought on line (producing electricity for the grid) or taken off line is referred to as “dispatch order.” As indicated, dispatch order is heavily influenced by incremental costs and time required to start up a unit and bring it on line. However, in the restructured electric industry, the actual dispatch order may also be affected by contract terms or bid prices.
10. Dispatchable and Non-dispatchable Units.
a. Dispatchable units. Generating units that can be brought on line or taken off line and whose electric output while on line can be controlled (i.e., increased or decreased) as necessary to keep electricity supply in balance with demand (or to adjust frequency, voltage, load on particular transmission lines) are referred to as “dispatchable” units. As long as they are available (i.e., not out of service for maintenance, repair or overhaul), all the units discussed above EXCEPT wind turbines are generally “dispatchable” units.
b. Non-dispatchable units. Units that are not readily available when needed or whose output level is not subject to the grid managers’ control – such as wind turbines when the wind is not blowing within the right speed ranges or because the output varies as wind speed changes – are “non-dispatchable” units.
Solar photovoltaic units are considered non-dispatchable because they are dependent on availability of sunshine. Solar thermal units (which are quite uncommon) may be “dispatchable” to the extent that they have storage capability.
Fossil fueled units run in a co-generating mode (i.e., their steam or “waste” heat is used for some specific purpose (e.g., heat for a manufacturing process or for central heating for buildings) may be considered “non-dispatchable” if the steam or waste heat is essential. Also, some generating units that have high start up costs or cannot withstand frequent starting up and shutting down may be considered ”non-dispatchable” or “must run” units.
Part B: Specific Issues Raised during the Conversation between the Local Official and the State Legislator
1. The “Intermittence” and Non-dispatchability of wind turbines is a critical point to your discussion. Wind turbines produce electricity only when the wind is blowing within a certain speed range. For example, according to the manufacturer, a 1.5 MW GE wind turbine (Model 1.5S):
· Begins to produce electricity when wind speed reaches 4 meters per second (8.948 miles per hour),
· Achieves full rated output when the wind speed reaches 14 m/s (31.317 miles per hour), and
· Cuts out when wind speed (5 second gust) reaches 25 m/s (55.923 miles per hour)
-- regardless of the electricity demanded by customers at the time. In fact, wind tends to be strongest at night and during winter months when – in most of the US – electricity demand tends to be lowest.
Thus, the electricity output is intermittent, highly variable, and largely uncontrollable AND unpredictable.
The practical implication of these characteristics of electricity from wind turbines is that some other generating unit(s) must be immediately available to serve in a “back up” or “balancing” role; i.e., increase output when the wind turbine output decreases and vice versa.
The generating units serving this “back up” or “balancing” role must be either:
· On line and running at less than peak capacity and efficiency or
· In a “spinning reserve” mode (i.e., running and synchronized with the grid but not putting electricity into the grid.
2. Low capacity factors. Some wind turbines seem to be achieving annual “capacity factors” in the range of 30% to 35% range but many have lower capacity factors – with the older units in the 10% to 15% range. Also, as indicated above, that output is highly variable and largely uncontrollable and unpredictable.
3. Quality of “wind resources.” The output achieved by a wind turbine is highly dependent on the speed and density of wind at the height of the turbine blades. US DOE laboratories and other contractors have collected wind data and published maps showing “classes” of wind at various locations. The accuracy of these maps varies widely. Some are based on actual, recent measurements, at turbine blade heights, made by accurate instruments. Others are based on old data collected for other purposes and on extrapolations. Some extrapolations appear to be made from data collected at lower heights and only in the windiest, winter months.
Some states where wind turbines are being proposed have poor “wind resources.” For example, “wind resource” maps currently available for Michigan suggest that some of the state is in “Class 2”; i.e., 4.4 to 5.1 meters per second (9.8 – 11.5 miles per hour) at a height of 33 ft. and 5.6 to 6.4 m/s (12.5 to 14.3 miles per hour) at a height of 164 feet. The maps also show that parts of the state along the lakes and a portion of northern Michigan are in “Class 3. (Chart showing wind class specifications can be found at http://rredc.nrel.gov/wind/pubs/atlas/tables/1-1T.html
Data obtained by Energy Ventures Analysis (EVA) of Arlington, VA, from Traverse City Light & Power indicates that the City’s 600-kW wind turbine produced 5,108,871 kWh of electricity during its lifetime from June 1996 through October 2002 for a lifetime capacity factor of 15.1%, which suggests the wind resources do not meet the criteria for “Class 3.” Data on actual electricity output for the wind turbines on Mackinaw Island, MI, which began service in late 2000, are not yet publicly available but the capacity factor appears to be about 18%.
4. Implications for reliability. The practical implication of the characteristics of wind turbines is that:
a. They detract from rather than add to system reliability. That is, some “dispatchable” unit must be immediately available to provide backup service.
b. They have very little if any “capacity value.” That is, they can be counted on to serve electricity demand only when high and peak electricity demand happens to coincide with the availability and speed of the wind.
c. The true “value” of the electricity is low. Unlike “dispatchable” units, their electricity often is not available when needed most.
5. Implications for cost. The true cost of electricity from wind turbines and “wind farms” is not limited to the cost at the point where it reaches a grid transmission line. Instead, the full, true cost of the electricity also includes:
· The cost of providing “back up” generating capacity.
· The higher cost of providing transmission capacity – because of the intermittence, variability, unpredictability and uncontrollability of the output.
· The higher cost of grid (control area) management and control.
Note: These three cost elements vary widely depending on a variety of circumstances including but not limited to the amount of electricity produced by wind turbines, location of the “wind farm,” type and energy source for the unit(s) providing back up service, and nature of electric load. Hydro generation tends to provide the lowest cost backup service because of its excellent load-following capability (assuming other factors – such as river flow -- affecting hydro output permit).
6. Wind turbines cannot be counted on to serve base load. This should be obvious from all the forgoing. For example, generating units must be dispatchable to be counted on to serve base electricity load (i.e., electricity demand).
7. Output for wind turbines is unlikely to keep intermediate or peak load units from starting up and would not displace the fuel required for other generating units on a kWh per kWh basis. As indicated above, other generating units must be immediately available – running at less than peak efficiency or in spinning reserve – to “back up” the wind turbines. They are using fuel, in fact more Btu per kWh when running in these modes than when running at full efficiency.
8. Output from wind turbines does not displace emissions from fossil-fueled units. Because some generating units must be immediately available and running at less than full efficiency or in spinning reserve, they will be giving off emissions if they are fossil-fueled units. The emissions may be somewhat lower but would not be displaced on the basis of a kWh of wind generation for a kWh of fossil-fueled generation.
9. Output from wind turbines is quite unlikely to displace output from coal-fired units. Any output from other units that is displaced is most likely to be from the “marginal” unit(s) operating at the time or the unit(s) determined to best serve the wind turbine “back-up” or “balancing” role. These are most likely to be the unit(s) providing automatic generation control (i.e., ramping output up or down to keep frequency and voltage in balance). Hydropower and turbine-based units are likely to be the best candidates because of their rapid response.
10. Whether the true cost of the output from wind turbines is less than the true cost of the output that IS displaced cannot be determined easily or from the fact available. Answering this question would depend on determining:
a. The full, true costs of the wind generation – including all the costs of backup generation, transmission and grid management.
b. The amount and true cost of the electricity generation that is ACTUALLY displaced.
c. The cost of subsidies which – as explained elsewhere – are substantial and can easily exceed $0.05 per kWh in the earlier years of a “wind farm” operation. Subsidy costs are even higher in states that provide additional tax breaks and subsidies for wind energy.
As indicated earlier, the amounts covered by paragraphs a. and b., above, vary widely. Several studies are underway to determine the costs and other implications of integrating electricity from wind in electric grids (e.g., in Electric Reliability Council of Texas – ERCOT; in California, Oregon and Washington and one in response to the Utility Wind Interest Group – UWIG covering Xcel in Minnesota and Bonneville Power in the Pacific Northwest). Also, consultant Eric Hirst has written two papers on the subject.
If the true costs (i.e., as described in a. and b., above) are in fact lower for wind, then there should be no need to continue federal and state subsidies for wind energy.
11. Transmission of electricity from wind turbines. One additional consideration is particularly important when assessing the potential role of wind energy; i.e., the inefficient use of transmission capacity that serves wind turbines.
a. Intermittence, volatility, unpredictability and uncontrollability. Electricity is produced by wind turbines only when the wind is blowing within the right speed ranges. The variations by wind speed are identified for one model of turbine in paragraph B. 1, above. This means that 1.5 MW of transmission capacity must always be available for each such turbine but, on average, that capacity will be used less than 30% of the time.
b. Transmission line losses. Electricity is lost as it moves over transmission lines. In general, the greater the distance, the greater the losses. Because “wind farms” are most likely to be located in remote locations because of their adverse impact on environmental, ecological, scenic and property values, the “line losses” tend to result in a significant economic penalty.
(Because of the inefficient use of transmission and resulting impact on the full, true cost of electricity from wind energy, the wind industry is working hard to shift the costs of transmission to electric customers – and away from “wind farm” owners.
12. “Green Energy” Programs. Utilities in many states have, either voluntarily or to comply with a statute or regulation, adopted programs that permit customers to elect to pay a premium price for electricity generated from a “renewable” source. The definition of “renewable” varies among states and among utilities offering the programs. To again use Michigan as an example, one large utility, CMS, permits customers to purchase “green” electricity by paying an extra $0.032 per kWh. CMS apparently has indicted that it might purchase wind energy with total capacity up to 50 MW for its voluntary program. This program probably accounts for much of the current interest in building “wind farms” in Michigan. However, according to EVA, very few customers have signed up to pay the premium prices – with the total accounting for about 8/1000 of 1% of CMS electricity sales.
US Energy Information Administration (EIA) data (Renewable Energy Annual 2001, Table C6) shows that Michigan does have other renewable energy sources. During 2001, Michigan obtained 4% of its electricity from “renewable” sources – about 2/3rd of which is from hydropower and 1/3rd from wood, wood wastes, municipal solid waste, and landfill gas. However, some renewable energy advocates do not consider all such sources as acceptably “renewable.”
Many of the utilities that have established such programs almost certainly have established them because they are required to do so or in an attempt to project a favorable “environmental image.” Very few premium priced “green” energy programs have significant participation. Almost certainly, few of the programs provide enough revenue to cover both the cost of the electricity and the cost of administering the program. The remaining, unrecovered costs are passed along to all electric customers.
Energy Market & Policy Analysis, Inc.
Reston, Virginia 20195-1875, USA
More wind turbines cause chaos
Windfarms and CO2 Savings - Debunking the Global Warming scare.
For more articles on windfarms, use the website search button, writing: "windfarms"
ESPAÑOL: ir a www.google.com pinchar "herramientas del idioma" y seguir las instrucciones.
In addition, you may want to look at several pages in the following report that is available at http://www.seab.energy.gov/publications/esrfinal.pdf.
It''''s a report by the Secretary of Energy''''s Advisory Board (SEAB) called "Maintaining Reliability in a Competitive U.S. Electricity Industry." It discusses the nature of electric systems and may be easier to understand than the explanations provided above. In particular, I suggest that you read the following pages:
a. Background chapter, pages 5-10 (because of all the title page and introductory material, these will show up on your screen a pages 27 -32).
b. Also in the same chapter, pages 13 -14 (which will show up as pages 35 and 36); i.e., the section labeled "Time Scales."
c. In Appendix D, all of page 85 (which shows up as page 107). This one page will show you all the different kinds of "reserves" that are needed to keep an electricity system stable and in balance, and adjust to unplanned changes (including unexpected loss of generating units or adjusting to intermittent generating sources such as wind).
d. You may also want to look at the glossary that begins on page 43 (showing up as 65), particularly the definitions of spinning and operating reserves. However, page 85, referenced above is a much more refined description.
Once you read these few pages, I believe you will see quite intuitively (a) the need for various kinds of backup generating capacity and (b) the kind of challenges that are presented to grid managers by intermittent and volatile electricity output from wind turbines.
por: Mark Duchamp (10/07/2003)
Glenn SchleedePresidentEnergy Market & Policy Analysis, Inc.Reston, Virginia 20195-1875, USA