by Willem Post
Editor’s Note: this is a copy of a letter sent to the Vermont Public Service Board in support of Vermont Yankee
New England annual average grid prices are about 5 c/kWh, nearly unchanged for the past 3 years.
Hydro-Quebec hydro energy is available at about 6 c/kWh. It is STEADY, CO2-free, available 24/7/365, rain or shine, windy or not windy.
Vermont Yankee’s nuclear energy is available at about 6 c/kWh. It is STEADY, CO2-free, available 24/7/365, rain or shine, windy or not windy.
Heavily-subsidized, state and federal, Lowell Mountain wind energy is available at about 10 c/kWh. Its cost would be 15 c/kWh unsubsidized. GMP will roll its extra cost into already-stressed households and businesses. It is variable and intermittent and require gas turbines to ramp down with wind energy surges and ramp up with wind energy ebbs. The requires extra fuel/kWh and emits extra CO2/kWh. At greater annual wind energy percentages on the grid, the extras mostly offset what wind energy was meant to reduce, i.e., wind energy is NOT a viable CO2 reduction technology and it acts as a disturber of the grid. See below URLs which have had about 10,000 views till now.
DISPATCH AND CAPACITY VALUE, VARIABILITY AND INTERMITTENCY OF WIND ENERGY
Wind energy is significantly different from conventional gas, coal, nuclear and hydro energy. Conventional generators, such as coal, gas and nuclear, are available for service 24/7/365, except during scheduled and unscheduled outages, i.e., reliable, staffed, fueled and controllable. Some are base-loaded or load-following, others can be put in service, i.e., dispatched, on short notice, whereas the “fuel” of wind turbines is a product of weather-dependent, variable wind speeds, i.e., its supply is unpredictable, unreliable and uncontrollable, and therefore, it has zero-dispatch value to a grid operator. Wind energy DISPLACES conventional energy on the grid, but in an inefficient manner. Wind energy does not REPLACE conventional energy.
Real-time wind speed prediction has become more accurate in recent years. It gives a grid operator a few hours notice regarding ESTIMATES of wind speed changes, which will give him time to more efficiently order the starting or stopping of OCGTs and CCGTs to maintain adequate spinning and ramping capacity at all times. This extra “juggling” of generators just to accommodate wind energy is less efficient, i.e., consumes extra fuel/kWh and emits extra CO2/kWh, than without wind energy. http://theenergycollective.com/willem-post/89476/wind-energy-co2-emissions-are-overstated
A grid operator needs to have available an adequate mix of generating capacity to serve peak demands for long-term planning purposes. The mix varies from grid to grid. Wind turbine systems have a capacity value in this mix.
Example: For summer peak capacity planning, ERCOT, the operator of the Texas grid, counts 8.7 percent of the Texas wind turbine rated capacity as dependable capacity at peak demand, in accordance with ERCOT’s stakeholder-adopted methodology. According to ERCOT, the capacity value is a statistical concept created for generator planning purposes. It is based on multiyear averages of wind energy generation at key peak demand periods. http://www.ercot.com/news/press_releases/show/381
ERCOT’s capacity planning value of 8.7% does not mean the ENERGY of 8.7% of wind turbine rated capacity would be available at any specified “time-ahead” period. Because of the randomness of wind speeds, no one can accurately predict available wind energy at any future time. Hence, it’s not available “on-demand”, i.e., not dispatchable.
Because wind energy increases by the cube of the wind speed, any change in wind speed creates significant surges and ebbs of wind energy. If such energy were fed into the grid, it would create chaos.
Thus, wind energy cannot stand on its own, has no value on its own, is completely useless, unless the grid has an adequate capacity of quick-ramping gas turbines and/or hydro plants that are required to inefficiently operate at part-load to be able to ramp up when wind energy ebbs and ramp down when it surges, which happens at least 100 times per day, to maintain grid frequency and voltage within required limits. If a grid does not have adequate capacity of such ramping plants, it either must acquire it, or connect to grids that do have it and do not need it for their own variable wind and solar energy.
During periods of high wind energy generation, many grids, such as of Germany, the Bonneville Power Authority, Texas, Colorado, Germany, Spain, etc., do not have a sufficient capacity of such quick-ramping generators. As annual wind energy percents on the grids increase, the grid operators are unable to balance the wind energy and need totransfer it to neighboring grids for balancing, if possible, and/or implement curtailments, which upsets wind turbine owners, because subsidy payments may be at risk; in the US, the production tax credit, PTC, is 2.2 cent per kWh produced.
Example: German wind power output peaked at about 12,000 MW on July 24, 2011, four days later the peak was 315 MW. Germany’s wind turbines are located mostly in Northern Germany which lacks adequate transmission facilities to Southern Germany, where the unpredictable, excess wind energy is likely not needed, because it usually occurs at night when demands are minimal. http://en.wikipedia.org/wiki/Wind_power_in_Germany
Wind energy usually is minimal during summer (almost non-existent in New England), moderate during spring and fall, and maximal during winter. Almost all the time, it is maximal at night.
In the US Great Plains, with good/excellent wind conditions most of the year, about 10-15 percent of the hours of a year wind energy is near zero, because wind speeds are insufficient (less than 7.5 mph) to turn the rotors, or too great for safety. During these hours, wind turbines draw self-use (parasitic) energy FROM the grid, and also during hours with slowly turning rotors when self-use energy exceeds the generated energy. Rotors are often kept turning with grid energy to prevent the rotor shaft from “taking a set”, or to not disappoint visiting lay public, including legislators, etc.
New England, with good wind conditions only on 2,000-ft or higher ridge lines, about 30 percent of the hours of the year near-zero wind energy is produced, because wind speeds are insufficient, or too great for safety, as would be the case during windy weather fronts or tropical storms, such as Sandy, passing over the ridge lines. About 60% of the wind energy is produced during about 30% of the hours of the year, mostly at night, and mostly during winter.
Offshore, New England wind energy production is technically feasible, but its subsidized energy cost would be at least 20 c/kWh, 2 times ridge line energy cost, excluding wind energy integration costs of at least 1.0 c/kWh. This compares with New England annual average grid prices of about 5 c/kWh, unchanged for the past 3 years.
The capital costs of a utility-scale offshore project is about $4,200,000/MW, of which about 35% is for the capital cost of new transmission systems to connect the offshore wind turbines to each other and to shore. The capital cost of reinforcing the onshore grid and the capital cost of the balancing plants, etc., are not included. See URLs.
This compares with $2,500,000/MW for ridge line projects, such as on Lowell Mountain, Vermont.
WIND ENERGY REPLACING CONVENTIONAL UNITS?
The above indicates there are many hours during a year when little or no wind and solar energy is generated. Therefore, almost all conventional generator units would still need to be kept in good operating condition, AND staffed 24/7/365, AND fueled to serve the daily demand when wind and solar energy is insufficient.
Without economically-viable, utility-scale energy storage systems, wind turbines and solar systems cannot replace any conventional units. All the units that would be needed WITHOUT the existence of wind turbines and solar systems, would also be needed WITH the existence of those systems.
Some of the conventional units would have less energy production with wind and solar energy on the grid, thereby adversely affecting their economics, which is further worsened due to increasingly inefficient start/stop, part-load and part-load-ramping operations, all of which requires extra fuel consumption/kWh and emits extra CO2 emissions/kWh. At greater annual wind energy percent on the grid, say 4%, the extras significantly offset what wind energy was meant to reduce. http://www.europeanenergyreview.eu/site/pagina.php? email@example.com&id_mailing=312&toegang=950a4152c2b4aa3ad78bdd6b366cc179&id=3865.
Willem Post, BSME New Jersey Institute of Technology, MSME Rensselaer Polytechnic Institute, MBA, University of Connecticut. P.E. Connecticut. Consulting Engineer and Project Manager. Performed feasibility studies, wrote master plans, evaluated and performed designs for incineration systems, air pollution control systems, utility and industrial power plants, and integrated energy systems for campus-style building complexes. Currently specializing in energy efficiency of buildings and building systems.