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Using Wind Tunnels for Calibration: Costs and Benefits
by Ildikó Dobi* and Gábor Kis-Kovács**

Background

The World Meteorological Organization (WMO) organized a Workshop on Assessment of Socioeconomic Benefits of Weather, Climate and Water Services, which was held in September 2008, in Sofia. [1] Ildiko Dobi represented Hungary and enjoyed the possibilities of improving her knowledge related to the basic economical issues of national meteorological services (NMSs).

The workshop was similar to a university course: participants attended interesting lectures all day and were asked to prepare materials and preliminary studies. This paper is a summary of a case study based on manuscripts [2] prepared by Gabor Kis-Kovács in 2002.

It is well known that professional weather observation and forecasting is the basic activity of all NMSs. The WMO prepares and upgrades guidelines regularly to recommend best practices to produce unified, accurate data measurement for data exchange from all over the world. [3]

To measure wind speed and direction, a wind vane and cup or propeller anemometers are usually installed at a height of 10 meters. Regular inspections are advisable for anemometers, because changes in sensor characteristics can degrade wind data quality as a result of physical damage, dust, or corrosion. Fully reliable calibration of anemometers is only possible in a wind tunnel.

But uninterrupted measurement is very expensive, not only because of the cost of a good quality instrument, but also because of the expenses of maintaining and running the meteorological network, including telecommunication aspects. A wind tunnel is an expensive investment, and therefore a cost-benefit study is a practical tool for decision making as most European NMSs are partly financed by the government, and the remaining budget must be earned from commercial activities.

The Hungarian Meteorological Service (HMS) has more than 100 years of experience measuring wind. The surface network is based on nearly 100 automated stations that include a Vaisala WAA 15 A electric cap and propeller anemometer and a WAV 15 A wind vane. In 2002, HMS fulfilled the requirement of the ISO 9001:2000 quality assurance system. Regular calibrations of wind speed and direction tools were critical for receiving the certificate on regular executed audit and thus it was determined to investigate the acquisition of a wind tunnel. The president of the institute instructed an economic analyst to prepare a study on the estimated cost and expected benefits.

Demands for Wind Measurements

First, regular calibration of hundred anemometers running in our network had to be solved according to the medium-term strategic plan of the HMS. Second, at the same time the first grid connected wind generator in Hungary was installed and an increasing demand on preliminary wind measurement for wind energy studies was expected. Another critical application for wind measurements is dispersion modeling of potential nuclear pollution. Hungary has a nuclear power plant in Paks not far from the capital and wind data are essential inputs for its nuclear alarm system.
In the early stages, the plan was to negotiate with the Slovakian Hydrometeorological Institute about the possibility of purchasing their calibration data. It was rejected because of the high estimated cost, potential technical difficulties at customs, and other risk factors.

Costs
The wind tunnel cost about $185,000 including delivery, installation, testing, insurance, and training, in addition to minor costs for remodeling the building to accommodate the size of the equipment. Maintenance costs of the wind tunnel were estimated at $4,000/year requiring 0.2 persons/year. According to the study, one month could be sufficient to calibrate all the anemometers running in the HMS network, assuming yearly calibration by six checking, or calibration by six different wind speeds.

Benefits
There were some expected indirect benefits from the wind tunnel investment. The equipment was the first wind tunnel in Hungary that was suitable for calibration. For the first time, the laboratory could provide calibration services for the full range of meteorological instruments beyond those required for wind measurements. It is evident that increasing data reliability produces better products, e.g., more precise weather forecasts. Additional capacity beyond the needs for anemometer calibration also made it possible to undertake commercial activities for partner institutions and enterprises.

Without these calibration tools, incorrect data could have harmful effects on the nation’s economy and decrease the perception of the meterological service as a reliable institute. These benefits haven’t been quantified. However, around $6000 income is expected from anemometer calibration for other institutions.

Consequences
The wind tunnel, shown in Figure 1, was installed in 2002. Based on the suggestion of the preliminary economic study, the analysis was repeated in a year. Working capacity was somewhat overestimated. The first year and a half year had many more technical problems than expected. But the wind tunnel proved to be ideal for calibrating the HMS anemometers because it was easy, fast, and accurate. Since then, there has been increasing demand on the use of the wind tunnel for calibrations. The benefit cost study concluded that it was worth it to accredit the laboratory, and with better marketing, calibration could be a profitable activity.

*Ildikó Dobi (dobi.i@met.hu) is the head of the International Relation Division for the Hungarian Meteorological Service.

**Gábor Kis-Kovács (kiskovacs.g@met.hu) is the head of the Green House Gas Inventory Division for the Hungarian Meteorological Service.

References

[1] http://www.sip.ucar.edu/news/pdf/WSW_October_2008.pdf
[2] Gábor Kis-Kovács: Analysis of wind-tunel investment (manuscript in hungarian, May 2002)
[3] http://www.wmo.int/pages/prog/www/IMOP/publications/CIMO-Guide/CIMO_Guide-7th_Edition-2006.html

Figure Information :

Figure 1: The HMS wind tunnel, installed in 2002 (Photo courtesy of Ildikó Dobi)