Hukseflux SR30 Solar Measurement In Cold Climates Instructions

Hukseflux SR30 Solar Measurement In Cold Climates

SR30: Solar measurement in cold climates

• Heated SR30 performs as well as externally ventilated pyranometers
• The U.S. National Oceanic and Atmospheric Administration (NOAA) has conducted the De-Icing Comparison Experiment (D-ICE) for radiometers at their Barrow, Alaska Observatory.
• Hukseflux has supplied several instruments for this experiment, including an SR30*. A preliminary analysis by Hukseflux of the publicly available data confirms that SR30 is an excellent alternative to traditional, externally ventilated pyranometers, even in the extremely frosty Alaskan winter! SR30 provides similar performance at a lower cost, has lower power consumption, and has lower maintenance requirements.

Introduction

• Accurate measurement of solar irradiance with a pyranometer in cold climates is challenging. Figure 2 shows a typical problem in freezing conditions: ice accumulated on the dome surface scatters the incoming sunlight and renders the measured data unreliable.
• We call this a reduction in “data availability”. Dew, frost, rime, and snow all harm data availability.
• Moreover, the extent of these effects can not always be estimated reliably from the data, possibly contaminating the data without you even knowing (shown in Figure 1). It is therefore important to use the right instrument in such harsh conditions.
• Figure 1 Data availability in cold climates is negatively impacted by various factors. In this example, we examine a single rime event on a clear sky day in the Netherlands. SR30 is compared to two traditional Kipp & Zonen CMP11 pyranometers: one is unventilated and unheated while the other is externally ventilated and heated. On such a clear sky day, one expects a cosine-like curve such as the SR30 shows.
• Although the deviation of the unventilated pyranometer curve might be filtered out by data quality control, the deviation of the ventilated pyranometer curve cannot be filtered out reliably, contaminating the data without you even knowing.
• Data taken on 4 DEC 2016, courtesy of KNMI.
• Figure 2 A typical problem in freezing conditions: ice accumulation on the dome surface of a traditional pyranometer reduces data availability. SR30 in front is heated.
• The SR30 is Hukseflux’s response to these issues. In this white paper, we will use data provided by an independent cold climate test to confirm that the SR30 is an excellent alternative to the traditional solution with externally ventilated pyranometers.
• In addition, we will highlight several of SR30’s distinct advantages.
• The use of an instrument by NOAA in the D-ICE experiment does not constitute an approval or endorsement. Data used by Hukseflux are taken from NOAA as published on the NOAA website, which is part of the public domain.
• The conclusions in this report represent the opinion of Hukseflux only.
• Find out more about D-ICE on the NOAA website: https://www.esrl.noaa.gov/psd/arctic/d-ice/

The problems with external ventilation

• External heating and ventilation, the traditional solution to operating a pyranometer in cold climates, has several drawbacks. First, the purchase of an external ventilation unit and the accompanying extra maintenance introduce additional costs.
• Second, power consumption is higher and the fan may freeze or get stuck. Finally, the application of external heating can lead to offsets for thermal sensors like pyranometers.

SR30, the first heated pyranometer

• Hukseflux SR30 provides a next-level solution to pyranometer operation in cold climates. Internal Recirculating Ventilation and Heating (RVHTM) technology (Figure 3) provides the advantages of external heating without the drawbacks. Heated air is ventilated between the inner and outer dome of the sensor, raising the sensor temperature evenly. This prevents ice accumulation while reducing thermal offsets caused by a dome-sensor temperature difference.
• Also, because the heated air is recirculated, the required heating power is much lower: 2 W versus a typical 10 W for external ventilation. This combination makes SR30 a very attractive and versatile sensor for operation in cold environments.
• Figure 3 SR30 is equipped with Recirculating Ventilation and Heating (RVHTM) technology.
• It enables uniform heating of the sensor while reducing thermal offsets.

Case in point: D-ICE

• To compare the performance of pyranometers in cold climates, the U.S. National Oceanic and Atmospheric Administration (NOAA) has conducted the De-Icing Comparison Experiment (D-ICE) at their Barrow, Alaska Observatory.

• Located more than 500 km north of the polar circle, this is an ideal testing ground for equipment in harsh, arctic conditions (see Table 1 for climate data).
  Hukseflux has supplied a heated SR30 for this experiment, to be tested alongside several traditional, externally ventilated pyranometers.

• SR30’s performance has, in our opinion, been remarkable, as the following data will show.

Table 1 Climate data for Barrow, Alaska.

avg. low -29.1 °C

warmest month| July avg. high 8.3 °C
temperature extremes during D-ICE (SEP 2017 – APR 2018)| 9.5 °C

-38.4 °C

| 3 SEP 2017

28 FEB 2018

• Figure 4 SR30 is battling the elements in Barrow, Alaska: the dome remains ice-free. Note that the neighboring, completely ice-free sensors are heated with ten times more heating power.
• Picture taken on 27 JAN 2018 (temperature -30 °C), courtesy of NOAA.

Data availability

• With sub-freezing daily highs on roughly two-thirds of the days per year, ice accumulation is a real problem in Barrow, Alaska.
• Regularly taken camera images, such as Figure 4, show that SR30 is holding its own in this environment: ice and snow accumulation only happen on the harshest of days, when the externally ventilated sensors also suffer from the same.
• Figure 5 illustrates irradiance totals as measured by SR30 and four traditional, Class A (secondary standard), externally ventilated pyranometers.
• Here, we see that SR30 is on par with competitor models in terms of measurement performance as well.
• Figure 5 Irradiance totals for a representative month in Spring 2018 in Barrow, Alaska. The measured totals of SR30 are compared to four traditional Kipp & Zonen externally ventilated pyranometers: one digital SMP22 and three analog CM11s.
• Due to the sensor positioning, various shadows from surrounding structures are cast on the sensors in the early mornings and late evenings. Therefore, for a fair comparison, we have opted to calculate totals only during a six-hour window around solar noon.
• Hukseflux’ SR30’s performance is comparable to the four externally ventilated pyranometers. On a few days, SR30 performs even better than the digital Kipp & Zonen pyranometer, which suffers from lensing due to ice accumulation on the dome (as verified using camera images). Data courtesy of NOAA.

Thermal offsets

• SR30’s careful design focuses on a uniform sensor temperature and low thermal offsets.
• This is also reflected in the D-ICE data. We have compared nighttime offsets of SR30, referenced to net longwave radiation as measured by a pyrometer, to the offsets of Class A, externally ventilated Kipp & Zonen CMP22.
• The results, illustrated in Figure 6, show a very low “zero-offset a” (offset at -200 W/m2 of longwave thermal exchange), longwave sensitivity, and static offset (at 0 W/m2 of longwave radiation).
• This makes SR30 a very accurate measurement instrument, even under extreme conditions.
• b) Nighttime offsets for an analog Kipp & Zonen CMP22 pyranometer, externally ventilated and heated.
• c) Fitted thermal offset parameters.

• Figure 6 Comparison of nighttime thermal offsets of SR30 (a) and an analog, externally ventilated and heated Kipp & Zonen CMP22 (b), referenced to net longwave irradiance as measured by a pyrometer.
• Data was collected during the D-ICE campaign in Barrow, Alaska over approximately 8 months (SEP 2017 – APR 2018).
• Longwave sensitivity, static offset, and “zero-offset a” are calculated from a linear fit on the data (c). SR30’s design with a focus on low thermal offset is paying off: SR30´s offsets are lower than the externally ventilated CMP22. Data courtesy of NOAA.

Conclusion: an excellent alternative

• Results from the De-Icing Comparison Experiment show that.
• SR30’s icing and measurement performance is comparable to externally ventilated pyranometers; and
• SR30 has low thermal offsets
• In addition, power consumption, maintenance needs, and costs are reduced.
• This combination makes SR30 an excellent alternative to traditional, externally ventilated pyranometers!

Final D-ICE Report

• Cox, C., Morris, S. M., et al The De-Icing Comparison Experiment (D-ICE): a study of broadband radiometric measurements under icing conditions in the Arctic
• European Geosciences Union, 2021

See also

• SR30 brochure
• View our complete product range of solar radiation sensors

Worldwide support

• Hukseflux has support available around the globe, with local representatives in:
• EU
• USA
• India
• Brazil
• China
• Japan
• SEA (Singapore and Australia)

About Hukseflux

• Hukseflux is the leading expert in the measurement of energy transfer. We design and manufacture sensors and measuring systems that support the energy transition.
• We are market leaders in solar radiation and heat flux measurement. Customers are served through our headquarters in the Netherlands, and locally owned representative sales offices in the USA, Brazil, India, China, Southeast Asia, and Japan.
• Would you like more information? E-mail us at: info@hukseflux.com
• Copyright by Hukseflux. Version 2403. We reserve the right to change specifications without prior notice.
• For Hukseflux Thermal Sensors go to www.hukseflux.com or e-mail us: at info@hukseflux.com

Documents / Resources

| Hukseflux SR30 Solar Measurement In Cold Climates [pdf] Instructions
SR30, SR30 Solar Measurement In Cold Climates, Solar Measurement In Cold Climates, Measurement In Cold Climates, In Cold Climates, Cold Climates, Climates
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