Resource Documents: Colorado (6 items)
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Author: Engineering Dynamics
This draft regulation references many ordinances laws and regulations in effect by many cities and counties in the U. S. and other countries. Also, referenced are technical papers, reports and nationally recognized standards relating to wind turbines. …
Wind Farm Noise Emissions
Noise emission from the site shall not be greater than the dB(A) slow and dB(C) slow, one-hour energy equivalent exceedance levels:
|Exceedance Value – %||Hourly Exceedance Level Turbine Noise|
|dB(A) Slow – Leq||dB(C) Slow – Leq|
Pure tones shall be defined using un-weighted one-third octave level as existing when the one-third octave band levels adjacent to the one-third octave band containing the tone are 5 dB or more less at frequencies greater than 500 Hz. Below 500 Hz, the differences must be 8 dB for center frequencies, 160, 200, 250. For center frequencies of 125 Hz and lower the differences must be 10 dB. If there are pure tones present as described in this section, then the audible noise standard shall be reduced by 5 dB.
Low Frequency Noise or Infrasound Noise
No low frequency noise or infrasound noise from wind turbine operations shall be created which causes the noise level at the project boundary or at a one-mile radius beyond the closest turbine, which ever is greater to exceed the following limits:
|1/3 Octave Band Center Frequency (Hz)||Sound Pressure Level (Leq)|
No impulsive noise from wind turbine operations shall be created which causes the noise level at the project boundary or at a one-mile radius beyond the project boundary or noise setback boundary that exceeds the following limits as measured by either of the two following methods.
- Method 1
A qualification of impulsivity can be obtained from the average of several measurements of the difference between the C-weighted “impulse hold” and maximum C-weighted “slow” sound pressure levels. The difference between the two shall be less than 20 dB.
- Method 2
The impulsive character can also be displayed as a time history of the acoustical signal which has been filtered through an octave band filter set at 31.5 Hz center frequency. The filtered octave band signal shall then be converted to a root-mean-square (RMS) value, slow response, and log converted to dB. The display can be either analogue or digital. The average difference between the maximum and minimum value shall be less than 20 dB when computed as the arithmetic average of 100 differences.
Clear Creek County Planning Department may require seismic (ground vibration) measurements at selected locations, when the site is in operation.
Download original document: “Draft wind turbine noise regulation”
Author: Bentek Energy
- To improve understanding of the electricity markets in Colorado and the Intermountain West
- To understand how wind, coal, and natural gas interact and what that interaction means for future natural gas use in electricity generation
- To help generate productive and informed discussions on how our nation will meet its future energy needs through the integration of various energy resources
- State renewable portfolio standards (RPS) mandate that wind energy be considered a “must take” resource. As such, when wind blows, generation from coal and natural gas must be adjusted to accommodate wind generation. This adjustment, called cycling, is defined as the sudden increase or decrease in generation.
- Most coal plants are not designed to be cycled, and doing so makes their operations inefficient, increasing SO2, NOx and CO2 emissions.
- Contrary to their stated goals, implementation of RPS in Colorado and Texas appear to be adding to the air pollution problem, especially in areas where older plants are cycled more frequently. This is particularly problematic when cycled coal facilities are located near major urban centers.
- Emissions issues related to cycling can be minimized by careful design of the generation mix. Inadequate flexible resources, such as that provided by natural gas, exacerbate the need to cycle coal, resulting in increased emissions. Alternatively, incorporating adequate flexible fuel capacity facilitates the goals of RPS without increasing emissions.
In 2004, Colorado became the 17th state to adopt renewable energy standards when voters passed Amendment 37. Colorado reaffirmed its commitment to wind and solar energy in 2007 when the Legislature passed HB 1281, increasing the requirement for utilities to purchase renewable energy by 100%. Colorado also approved the Climate Action Plan, which relies on renewable energy to play a central role in the state’s strategy of reducing “greenhouse gas emissions by 20% below 2005 levels by 2020″.
Policymakers’ stated hope was that renewable energy would not only be a major tool to reduce carbon emissions, but also, by displacing conventional fuels, would reduce smog and other air pollution, presumably by reducing sulfur dioxide (SO2) and nitrous oxides (NOX), the principal components of ozone and smog.
This report, which examines four years of Public Service Company of Colorado (PSCO) hourly operational history, illustrates how coal cycling, which in part results from wind generation, negates the emission benefits of wind energy. Integrating an intermittent, must take resource, such as wind energy, requires PSCO to cycle its coal and natural gas-fired plants. The incidents of coal cycling have risen markedly with the introduction of 775 MW of wind capacity since 2007.
Coal-fired power plants are designed to run most efficiently at stable rates and are not well-suited to accommodate the load variability imposed by the integration with wind generation. Cycling causes coal-fired power plants to operate less efficiently, and reduces the effectiveness of their environmental control equipment, which together drive up emissions. Paradoxically, using wind energy in such a way that it forces utilities to cycle their coal generation often results in greater SO2, NOX and CO2 emissions than would have occurred if less wind energy were generated and coal generation was not cycled.
An analysis of the Electric Reliability Council of Texas (ERCOT), which also operates under a RPS mandate to utilize wind energy, validates the emissions findings for PSCO. The underlying problem is the same for both PSCO and ERCOT: wind generation frequently cannot be accommodated without forcing coal-fired units to cycle.
Whereas natural gas-fired combustion turbines and combined-cycle facilities are designed to accommodate cycling, coal equipment is not. Coal boilers are designed to be operated as a base load resource – in other words, to operate at a consistent output level all the time. Because gas resources are not fully utilized to offset wind energy produced in PSCO and ERCOT, coal units are being cycled. Emission levels are increasing, not decreasing, at PSCO and ERCOT coal units because the units are being cycled to compensate for wind generation.
The results of this study help explain why PSCO’s coal-fired plants located in the Denver non- attainment area have experienced an increase in SO2, NOX and CO2 over the past few years. Four of the five most frequently cycled coal plants are located in proximity to Denver. The results also suggest that this problem will worsen over time unless more gas generation is utilized to absorb wind generation variability.
There are national implications as well. Congress and the Obama Administration are considering a national RPS. Before such a national standard is implemented, there is a compelling need to better understand how intermittent sources of energy such as wind can be integrated with existing nuclear, coal and natural gas capacity without producing cycling-induced emissions problems.
- The use of wind energy by PSCO has resulted in increased levels of SO2, NOX and CO2 from coal plants in the non-attainment area. Wind-induced coal cycling in ERCOT has resulted in increased SO2 and NOX, with only minimal savings of CO2.
- The mechanism driving increased emissions is the need to cycle coal facilities in order to accommodate wind generation, which is considered a “must take” resource due to the RPS mandates.
- When coal plants are cycled, the heat rate rises, resulting in higher emissions of SO2, NOX and CO2 than would have been the case if the units had not been cycled. This problem can persist for up to 24 hours after cycling the facility, increasing emissions even further.
Effective wind energy requires sufficient flexible natural gas generation in order to avoid cycling coal facilities. Enacting RPS’s that require more than 5-10% of wind energy for electricity generation will significantly add to emissions unless more flexible natural gas generation is utilized. The report recommends:
- Short term. (1-2 years)
Limit the utilization of wind generation to that which can be offset by cycling existing natural gas facilities.
- Long term (Beyond 2012)
Utilities operating under RPS should consider adding significantly more combined cycle and combustion turbine gas plants to their generation mix. Adding more natural gas plants will reduce the need to cycle coal facilities in all but the most extreme situations.
This report was prepared for the Independent Petroleum Association of Mountain States (IPAMS).
Download original document: “How Less Became More”