Let me summarize the situation with the studies by Seifert and Morgan that are being used as the basis of wind industry information and for NYSERDA’s policy on risk to people and property from thrown ice.
1. We do not have true measurements.
2. We do not have true surveillance.
3. We do not have an adequate survey response rate.
4. We do not have risk calculations based on assumptions that are appropriate to the physical properties of ice formed on turbine blades.
5. We do not have publication (10 years after the data was gathered) in a peer review journal, to ensure accuracy and impartiality.
Earlier the calculated theoretical distance that ice could travel given the height and speed of a turbine blade was discussed. Until an actual icing surveillance study is available as an empirical guide we are left having to use this calculated theoretical distance---of one half mile--- as the basis for creating policy designed to protect public safety.
On June 7th the New York State Department of State made a presentation in Delaware County which included a discussion of safety risks from ice throws. Unfortunately the information was misleading, did not use credible sources and factually incorrect. The information concerning sound was even more problematic, and will be discussed in my note on noise at a later date.
The totality of the information presented concerning ice throws and public safety as guidance for planners and town officials was
1. A chart purporting to show the distance traveled by thrown ice. This chart actually concerns stationary turbines, not turbines with blades moving at 150 to 200 mph. The chart which the DOS used (copied from a paper by Seifert ) is titled “Typical result of an ice fall width calculation for a turbine at standstill”.
2. The DOS refers to two “Insurance Testimonials” on the NYSERDA website. These letters are from insurance brokers are in Palm Springs, California and Torrence, California, both desert areas of Southern California not subject to icing.
3. The main source used in the DOS presentation (described in the slide she showed and included in the handout) is a paper from Williams College. She states the “study reports icing in that climate typically 3 to 5 days a year and calculates the risk as acceptable”. A few points about this report will help one understand its scientific quality and how it reflects on the decision to use it as the primary reference in a presentation to government decision makers.
a) The Williams College “study” is not actually a study.
It is a report written by undergraduate students (see page 8) in an environmental course at Williams in support of a local wind turbine project.
b) The Williams paper expresses concern about liability issues (page 22) being caused by injuries from thrown ice striking hikers using a trail near the proposed turbines and suggests moving the trails to avoid injury and liability issues.
c) The nearest residence to the proposed turbines in the project discussed in the Williams students’ paper is over one mile (as discussed in the report’s discussion of noise, page 16-17).
d) The students’ paper cites a report by Schaffner as the source of their statement “Although our turbines would have blade diameters of 80 m (260 ft), ice throw danger from ice throws from any turbine with blade diameters over 40 m (130 ft) is the same.” In fact Schaffner makes no such statement and does not even address the issue of ice throw distance. Rather, Schaffner’s paper is simply a report of a technology (SODAR) designed to sense when ice forms on turbines in remote locations.
e) The only information the Williams students use to form their risk assessment is discussed in my main report----Seifert’s survey which did not use actual measurements to create his data (and presented as 17 points on a chart) and the paper by Morgan work (discussed above) which made a series of calculations that assumed thrown ice would not retain the shape of the turbine blade on which it was formed.
The point of this review is to indicate that the presentation by the NY State Department of State to officials in Delaware County did not give a true sense of the science concerning ice throws in the region, and did not provide adequate information or appropriate guidance for officials interested in protecting public safety.