LIST OF SUBMITTED ABSTRACTS
During overcast and/or rainy or snowy days the IPC-XII Symposium will be held. All participants are encouraged to give presentations
at the symposium. The purpose of this symposium is to exchange experience and to
share and build knowledge .
Session 1: Irradiance Networks
Monitoring and Data Archival of India Meteorological Department’s Radiation Network in real time
(Anjit Anjan, IMD)
Central Radiation Lab, Pune of IMD is running a network of 45 radiation stations. Multiple radiation sensors are installed at network stations for measurement of different parameters.
At all these stations, measurement of global solar radiation, terrestrial,UV-A is being carried out while at a few selected stations other parameters like diffuse, direct, and UV-B
are also measured. Data loggers have been introduced at all stations. The primary objective of the observational programme is to have an understanding of basic physical processes
involved in the conversion of the Sun's radiant energy into atmospheric motions as also into chemical and biochemical energy. The observations made at national network of radiation
stations are useful in the assessment of solar energy potential in different parts of the country.
GPRS modems have been introduced to the Radiation Network and average data at an interval of 10 minutes are available in website
(www.imd.gov.in ). IMD relied heavily on accurate solar radiation data for their research. Their real-time solar radiation data was available at every 10 minutes. Historical
datasets of solar radiation are a key element in designing solar power systems and energy efficient buildings; however finding accurate multi-year data near the design site has
always proved challenging. There are only 45 sites in the India providing research-quality observations of solar radiation. The automation in Radiation network saves both time and
manpower for monitoring and data archival of Radiation network.
Solar Resource Assessment Network of India
(Prasun Kumar Das et al., NIWE)
To assist project activities of India’s Jawaharlal Nehru National Solar Mission by providing bankable and investment grade solar data, National Institute of Wind Energy (NIWE),
Chennai has successfully set up the world’s largest network of automatic ground monitoring of solar radiation and meteorological parameters across India under Solar Radiation Resource
Assesssemnt (SRRA) project initiated by Ministry of New and Renewable Energy (MNRE), Government of India. High end equipments of international standard are used to measure
Global Horizontal Irradiance (GHI), Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DHI) alongwith meteorological parameters in 117 stations to develop a database
of reliable and accurate solar raditation data. One minute average real time data with sampling rate of one second can be accessed at Central Receiving Station at NIWE, Chennai.
Deutsche Gesellschaft fur Internationale Zusammenarbeit (GIZ) is assisting NIWE in the development of quality control mechanism and data processing to generate high quality
investment grade data. To maintain the quality of sensors, a calibration system has been developed at NIWE, Chennai. On analysis, variation of sensitivity of solar sensors
over the years has been found to be very less. The paper highlights the role of standards of calibration, practice of quality and regular maintenance, field issues and best
practices for quality assurance in a large real time network of SRRA stations in India.
SOLAR RADIATION AND ACTIVITIES IN ARGENTINA
(Gerardo Carbajal Benitez et al., SMN)
The National Meteorological Service through the Global Atmospheric Watch (GAW) programme has a network of five solar radiation measuring points and four points in joint agreement with
another institution (CITEDEF). The distribution is located in such a way that it covers the whole country.
The components that are currently measured are global and scattered radiation
with the Secondary Pyrheliometres CM11 Kipp & Zonen. Only at Ushuaia the PHP EPPLEY are used. The other four points, which are part of the agreement, only measure global radiation with the
CM21 Kipp & Zonen Pyrheliometres.
Within the framework of the solar radiation measuring activities there are the local calibration campaigns through the Comparison against the EPPLEY
Model HF30112 Pyrheliometre. During the said Comparison twelve pyranometres and one TMI Pyrheliometre were compared in the Summer 2014/2015. The norms which have been used were the norms
ISO 9059, 9846, and 9848.
Another key activity held in the city of Buenos Aires is the course “Introduction to the Solar Radiation” which prepares and trains the operators of the
instruments through a general knowledge of what is solar radiation and maintenance of the sensors (cleaning, replacement of the silica gel, etc). Participation of the Regional
Workshop “Traceability in the Solar Radiation” organized by the Industrial Technology National Institute (INTI). In this regard, the IRAM National Norms are being used in the
indoor and outdoor calibrations.
Finally, an article entitled “Preliminary Study in the Solar Radiation Tendencies in Buenos Aires, 1941-2010” has been submitted at the Meteorological
Congress of Argentina (CONGREMET XI-2012). Its publication is currently under way and a journal is being looked for to present this paper.
Solar radiation monitoring in Slovakia
(Anna Pribullova, SHMI)
Measurements of solar radiation characteristics have long tradition in Slovakia. Monitoring of sunshine duration by different types of heliographs have been performed since 1893
at astronomical and meteorological observatory Hurbanovo. In 40-ty years of the last century, global solar radiation measurements began using Gunn-Bellani radiometer. Network of
stations with regular measurements of sunshine duration and global radiation was established after IGY. First four stations with program targeted to measurement of solar radiation
(global, diffuse, PAR, UV) were established by the Slovak Hydrometeorological Institute 35 years ago. Measurements were set to the WRR radiation scale. Monitoring of total ozone and spectral
ultraviolet radiation by the Brewer spectrophotometer begun in 1993 at upper-air station Poprad-Gánovce where was established National center for measurements of solar radiation (ARC)
in 2007. Program of the ARC Poprad-Gánovce was broadened of measurements of direct radiation, radiative balance, albedo, aerosol and its vertical distribution in 2014 and has been
continuously under development.
Solar radiation measurement networks in Taiwan
(Sheng-Hsiang Wang, CWB Taiwan)
In the presentation, I will give an overview on the solar radiation measurements activities/networks in Taiwan. The Central Weather Bureau (CWB) initialed the automatic solar
irradiance measurements since 1970’s. Starting from 1980’s, they use (replaced with) Epply PSP pyranometer for 17 metrological stations and continue operate to present. The UV-B
measurements (total 34 stations) is operated by Taiwan Environmental Protection Administration and CWB since 2002. The calibration procedures for those networks will be discussed.
Recently, Lulin Atmospheric Background Station (LABS) located at Mt. Lulin in central Taiwan was established to monitor the atmospheric compositions and radiation in the lower free
troposphere of Ease Asia since 2006. Our radiation measurement suite, including Cimel sun-photometry, MFRSR, broad-band SW/LW/UV/PAR radiometers, and sky imager, has been operated
based on NASA/AERONET, NOAA/GMD, and WMO/GWO protocols. The Lulin site is planning to join the BSRN next year.
Radiation measurements in Estonia
(Kristjan Nurmela and Ain Kallis, Estonian Environment Agency)
Actinometric network in Estonia consists of:
eight stations, measuring global radiation,
five stations, measuring UVB radiation,
13 stations, measuring sunshine duration.
Longer time series of radiation measurements have been obtained from Tartu-Tõravere (since 1950) and Tiirikoja near Lake Peipsi (since 1956).
Tartu-Tõravere Station became a BSRN candidate in 1993, since 1999 it has operated as a BSRN station. It belongs to the Estonian Environment Agency (former Estonian Meteorological and
Hydrological Institute).
Radiation sensors at Toravere:
direct irradiance (PMO6 absolute radiometer, pyrheliometers AT-50, NIP)
global, diffuse, reflected irradiance (CM-21)
net radiation (GB-1)
downward (Kipp & Zonen CGR 4) and upward (Eppley PIR) longwave irradiance
UVA, UVB, UV erythemal radiation (CUV3, CUVB1, UV-SET)
photosynthetically active radiation, global and direct (LI-COR 190SA)
total ozone measurements (MICROTOPS II)
Data are submitted to the BSRN archive up to 31.08.2014.
New instruments:
spectral radiometer PFR
pyrgeometer CGR4 with CVF4 ventilation unit
and sun tracker 2AP.
Towards Verified DNI Maps for Southern Africa
(Anro le Roux, GeoSun)
GHI measurements are relatively common in die world and have also being readily available in South Africa. DNI measurements, on the other hand, are not as common but have
increased in the last five years. Initially, only one station (BSRN) started to measure DNI at De Aar (central South Africa), but stopped in 2005. DNI was also measured on
the east coast of South Africa, but developers were more interested in the north-western side of the country, which has a higher annual DNI. A GIZ sponsored project was
awarded to the Center of Renewable and Sustainable Energy Studies (CRSES) at the University of Stellenbosch (US), to commission various DNI measuring stations. USAID
also sponsored DNI measuring stations, with one in Botswana, and another prospective station in Namibia. GeoSUN Africa was subcontracted to install and maintain these
stations, as well as process the ground measured data for verified solar mapping purposes. GeoModel Solar was subcontracted to create
a ground-truthed DNI satellite map of South Africa, using the DNI data measured at these stations. Station data and a verified DNI map of South Africa are publicly released.
In addition to the stations near South Africa, the World Bank funded multiple DNI measuring stations that are being installed in Zambia, Malawi, and prospectively Tanzania.
Solar radiation measurement network in Chile
(A. Pino, R. Escobar, C. Cortés, M. Salgado, Fraunhofer Chile)
The experience of the PUC/DICTUC/FCR-CSET team in solar energy resource assessment for Chile is reported. Chile is endowed with an exceptional solar potential, however until the
year 2008 a public and reliable solar database was not available. Since 2010 the PUC/DICTUC team has deployed a ground stations network in order to validate the Chile-SR model
results (satellite-derived irradiance estimations), supported by the Chilean Science and Technology Development Fund. Currently the data acquired by the ground stations is used for
research purposes and contracts with the industry.
The Austrian radiation monitoring network ARAD
(M. Olefs, D.J. Baumgartner, F. Obleitner, C. Bichler, U. Foelsche, H. Pietsch, H.E. Rieder, P. Weihs, F. Geyer, T. Haiden, W. Schöner, ZAMG)
The Austrian RADiation monitoring network (ARAD) has been established to advance the national climate monitoring and to support satellite retrieval,
atmospheric modelling and solar energy techniques development. Measurements cover the downwelling solar and thermal infrared radiation using instruments according to Baseline
Surface Radiation Network (BSRN) standards. A unique feature of ARAD is its vertical dimension of five stations, covering an air column between about 200 m a.s.l (Vienna) and 3100 m a.s.l.
(BSRN site Sonnblick). The presentation outlines the aims and scopes of ARAD, its measurement and calibration standards, methods, strategies and station locations. ARAD network operation
uses innovative data processing for quality assurance and quality control using, manual and automated control algorithms. A combined uncertainty estimate for the broadband shortwave
radiation fluxes at all five ARAD stations is shown as well as some typical application examples demonstrating the added-value of the measured data.
Solar resource assessment in Mexico
(David Riveros-Rosas, UNAM)
A mid 70's of last century, first attempts were initiated in order to know the Solar Climatology in Mexico. For this, were used data since heliographs and Actinographs, until the use
of models applied to satellite images. Each of these attempts has able to present a great improvement over the previous one, but the lack of data makes impossible the assessment of each model.
Currently you can find on the Internet a number of maps and databases describing spatially and temporally the solar distribution, but there is no reliable information on surface to
evaluate any result. Actually, there are several solarimetric networks in the country; one of them corresponds to an automatic network of atmospheric monitoring stations (EMAS) from
The National Weather Service (SMN). The database of EMAS were recently analyzed and the results were used to assess the results of CSR model and SUNY model over the national territory.
This year, a new reference solarimetric network in collaboration with NREL is being installed for accurate assessment of solar resource models in all the country.
The irradiance observation network of German Weather Service
(R. Becker, K. Behrens, W. Riecke, J. Trentmann, DWD)
Introduction of the irradiance network and filterradiometry - current state, applications, future plans.
Solar radiation measurement in China
(Lei Ding, Yun Yang, Wei Chong, CMA)
National radiation network in China and radiometer calibration will be talked in the presentation. There're three radiation networks in China. The national radiation network
was established since 1957,including 98 stations with second class radiometers. GAW stations and national baseline radiation stations has high quality instruments and facilities.
Radiometer calibration in China are also introduced. National standard group traced to WSG directly since 2000. National pyrheliometer comparison (NPC)are held once every two years to
transfer the WRR to 7 provicial agencies of meteorological metrology.
Session 2: Instrumentation – New Developments
Storytelling with Markus :)
(Markus Suter, PMOD/WRC)
Some highlights of my recently published PhD-thesis will be presented. This will include the performance of the new Digital Absolute Radiometer (DARA) that has been operated since the last IPC. The (DARA) serves as a prototype for upcoming space based experiments on board NORSAT-I and PROBA-III satellites.
DARA has been extensively characterised. Its measurements are traceable to SI-base units with an uncertainty in the order of 0.02%. DARA has also been compared to existing reference standards for (solar-) irradiance. I will dicuss the difference between the WRR and the SI-base units, these measurements have been significantly improved with DARA.
New developments in reduction of zero offsets in pyranometers and pyrheliometers
(Kees van den Bos, Hukseflux Thermal Sensors)
Radiometers have zero offsets. These are caused by temperature differences between the windows/domes and the detector, and form a significant source of measurement uncertainty.
Zero offsets for secondary standard pyranometers, during daytime in the order of 10 W/m2 , play a role in measurement and also in calibration. By applying new instrument design, we expect daytime zero offsets to remain limited and no longer to be the major contributor to the measurement uncertainty that they used to be. Offset reduction is expected to lead to more accurate measurement results, especially when measuring diffuse solar radiation.
Traditional ways to reduce offsets are forced ventilation and sensor design. During calibration the effects of zero offsets may be compensated for.
New developments in pyranometer design have resulted in significant offset reduction. The use of a sapphire outer dome on pyranometers ensures very good thermal coupling between outer dome and body. Extensive research has been carried out to test the offset of this new pyranometer design. We show test results of both in- and outdoor experiments and comparisons.
We also present results of independent research on pyranometer offsets by outdoor capping experiments carried out recently by Universidad de Extremadura.
Zero offsets in pyrheliometers are reduced by thermally uncoupling the front window. Using this technique pyrheliometer front windows can be heated to improve the data availability. The thermal uncoupling reduces the offset caused by this heating. We present results of comparisons of various pyrheliometer models.
Development of a new Controller for Absolute Cavity for cavity calibration and solar irradiance measurement
(Ajay Singh, Mathew Perry, Campbell Scientific)
In this paper development of a fully automatic controller for absolute cavity radiometer is reported for self-calibration and measurement of solar irradiance using Eppley AHF cavity.
The main component of the controller is a data logger CR6 from Campbell scientific and utilizes some unique features of the logger. The computer program can be developed to make manual,
semi-automatic or fully automatic measurements on given time interval with minimum input required from the user. In this report measurement with Eppley cavity is reported but the controller
can be reconfigured to use any absolute cavity. The resolution and accuracy of the voltage measurement on the CR6 logger easily satisfies the WMO classifications of a pyrheliometer to be
a standard reference.
AirShield soiling reduction technology for Pyrheliometers and Pyranometers
(Joachim Jaus, Black Photon)
In solar irradiation measurements highly accurate optical measurements must be performed in a non-ideal environment with plenty of soling sources such as dust, pollen or aerosols.
These soiling sources add a lot of uncertainty to solar irradiance measurement and require frequent cleaning of the instruments. Condensing humidity adds another layer of uncertainty,
both directly due to its refracting properties as well as because of its function to "cement" dust and dirt onto the detector window surface.
At Black Photon Instruments we have developed the AirShield technology to protect Pyrheliometers, Pyranometers and also absolute cavity instruments from soiling. The system is based on
filtered air that is used as a barrier between the detector window surface and the ambient environment. In the presentation, we are going to show technological details as well as application
experience with the AirShield system.
Pointing accuracy of the new SOLYS Gear Drive and other trackers
(Marc Korevaar, Joop Mes, Kipp & Zonen)
A solar tracker is an essential tool for measuring direct solar radiation with pyrheliometers or absolute cavity radiometers. The sun tracker ability to point these instruments accurately at
the sun enables high quality solar measurements.
For a sun tracker - instrument system the figure of merit is the pointing error, which is defined as the deviation between the solar center and the optical axis.
The talk will be about which factors contribute to the pointing error and uncertainty calculations of a.o. the new SOLYS Gear Drive tracker. Furthermore, the value of active tracking
using a sun sensor is discussed.
The SolarSIM: Low-Cost Spectral Irradiance Meter
(V. Tatsiankou, K. Hinzer, J. E. Haysom, H. Schriemer, R. Beal, COFOVO Energy)
The traditional way of measuring solar spectra involves the use of a field spectroradiometer. However, this approach is rarely used due to its significant cost. A solar spectral irradiance
meter (SolarSIM) was designed as a cost-effective alternative to a field spectroradiometer. The SolarSIM uses low cost silicon photodiodes with rugged bandpass filters to measure the solar
spectral irradiance in narrow wavelength bands. The SolarSIM's software then uses these measurements to resolve the solar spectrum through estimation of the major atmospheric processes,
such as air mass, Rayleigh scattering, aerosol extinction, ozone and water vapour absorptions.
85 years of Traceability to the Pyrheliometric Scale
(Tom Kirk, Eppley Labs)
A brief description of traceable calibrations at The Eppley Laboratory, Inc. from 1930 to 2015.
Smithsonian Pyrheliometric Scale of 1913
International Pyrheliometric Scale of 1956
World Radiation Reference (1979)
Development and positioning of absolute cavity radiometer for controlling uncertainty of indoor calibration of reference PV-device
(Sanekazu IGARI, Kazuhiko Ohkubo, AIST)
Power generation of photovoltaic module is being agreed internationally at IEC, to commonly perform quality evaluation under the standard test conditions (STC) such as spectral distribution,
total irradiance, device temperature, and so on.
Meanwhile, the circumstance to actually realize “STC” in the field is restricted. In Japan, with such reason, we have been trying to develop the indoor calibration method for reference PV
device by solar simulator, and indoor measurement method by reference PV device.
We have been continuously engaged on pursuing sophistication of reference PV device calibration technique. With two purposes mentioned below, we have developed and put a high parallelism
solar simulator which is measureable it’s all irradiance using absolute cavity radiometer into practical use.
Purpose 1: To control significantly the calibration uncertainty of primary reference PV device by solar simulator method which is restricted by calibration uncertainty
of spectral irradiance standard lamp.
Purpose 2: To secure the traceability for WRR scale based on the relationship with amount of global solar radiation which is being used for designing PV power generation system.
At the same time, due to inadequacy of fabrication accuracy for inner optical system as well as non-equivalency of inner cavity and position of solar tracking target of housing,
it is very difficult to make alignment to reproduce regarding the existing absolute cavity radiometer which is not expected to use under the collimated light like solar simulator.
We join the upcoming IPC symposium taking made-in-Japan absolute radiometer, for which such problems were solved, with us in order to perform the final evaluation. Let us speak
about what we are up to and future plans.
The solar precision spectroradiometer PSR
(Julian Gröbner, Natalia Kouremeti, PMOD/WRC)
A new generation of solar spectroradiometers, the Precision Solar Spectroradiometer (PSR), has been developed at PMOD/WRC to eventually replace current filter based sunphotometers.
It is based on a temperature stabilized grating spectroradiometer with a 1024 pixel Hamamatsu diode-array detector operated in a hermetically sealed nitrogen flushed enclosure. The
spectroradiometer is designed to measure the solar spectrum in the 300 to 1020 nm wavelength range with a spectral resolution varying between 1.5 and 5 nm ( full width at half maximum).
The optical bench made of a carbon alloy is optimized to minimize the temperature dependence of solar measurements to less than 0.1%K-1 for ambient temperatures ranging from -20°C to +40 °C.
The temperature dependence of the wavelength to pixel function was measured to be 0.02 nm K-1 using as reference the Fraunhofer structure of the solar spectrum. A novel algorithm has been
developed to convert the non-equidistant spectra to a regular wavelength grid and to a constant resolution over the whole spectrum. The spectral stray-light was determined using tuneable
laser systems at PTB and META. Measured spectra are routinely corrected by applying the stray-light matrix inversion algorithm developed by Zong.
The instruments are absolutely calibrated in the laboratory using reference standards in order to measure direct spectral solar irradiance with an uncertainty of ±3%. Two instruments were
deployed at the Izaña Atmospheric Observatory of AEMET (Tenerife, Canary Islands) in 2014 and 2015 to perform zero airmass extrapolations and to validate the spectral aerosol optical depth
derived from solar spectra, in a wide range of aerosol load, with PFR and CIMEL sunphotometers deployed at this site.
Session 3: Measurement and Calibration Methods
Measuring Broadband IR Irradiance in the Direct Solar Beam
(Ibrahim Reda, NREL)
Solar and atmospheric science radiometers such as pyranometers, pyrheliometers, and
photovoltaic cells are calibrated with traceability to consensus Reference, which is maintained by
Absolute Cavity Radiometers (ACRs). An ACR is an open cavity with no window, and developed to measure
extended broadband spectrum of the terrestrial direct solar beam irradiance, extends beyond the ultraviolet
and infrared bands; i.e. below 0.2 μm and above 50 μm, respectively. On the other hand, the pyranometers
and pyrheliometers were developed to measure broadband shortwave irradiance from approximately 0.3 μm to 3 μm,
while the present photovoltaic cells are limited to the spectral range of approximately 0.3 μm to 1 μm.
The broadband mismatch of ACR versus such radiometers causes discrepancy in radiometers' calibration methods
that has not been discussed or addressed in the solar and atmospheric science literature. Pyrgeometers
are also used for solar and atmospheric science applications and calibrated with traceability to consensus
Reference, yet they are calibrated during nighttime only, because no consensus reference has yet been
established for the daytime longwave irradiance. This poster describes a method to measure the broadband
longwave irradiance in the terrestrial direct solar beam from 3 μm to 50 μm, as a first step that might be
used to help develop calibration methods to address the mismatch between broadband ACR and shortwave
radiometers, and the lack of a daytime reference for pyrgeometers. The described method is used to measure
the irradiance from sunrise to sunset; the irradiance varied from approximately 1 Wm-2 to 16 Wm-2 with an
estimated uncertainty of 1.5 Wm-2 , for a solar zenith angle range from 80° to 16°, respectively.
Results of Baltic Region Pyrheliometer Comparison, BRPC-2012
(Thomas Carlund, SMHI, PMOD/WRC)
In late May 2012 a "sub-regional" pyrheliometer comparison was held at the RRC in Norrköping, Sweden. In parallell to the pyrheliometer comparison also a short pyranometer comparison was carried out.In the pyrheliometer comparison 11 cavity radiometers from 5 countries took part and 10 pyranometers from 7 countris participated in the pyranometer comparison. At the pyrheliometer comparison all instruments agreed within 0.1 % from the mean of the instreuments having a WRR factor from IPC-XI. With one exception, the accumulated global irradiation from the participating pyranometers agreed within 1 % the reference. Further details and results of the comparison will be presented.
Improvement of data availability of pyranometers, pyrheliometers and pyrgeometers
(Dorine van der Vlies, Hukseflux Thermal Sensors)
Traditionally forced ventilation is used to increase data availability. This method involves high maintenance, power consumption ( > 5 W) and induces thermal offsets.
This presentation focuses on new technical developments to increase data availability and maintain measurement accuracy. We focus in particular on quantifying the improvements that are made by internal heating of sensors.
Using various design changes, internal heating can be applied in pyranometers, pyrheliometers and pyrgeometers maintaining their measurement accuracy.
During the period of a month various pyranometer configurations were monitored in an outdoor test facility. Pyranometers with direct heating were compared to pyranometers with forced ventilation and non-heated pyranometers. Data availability is estimated from simultaneous monitoring of the instrument condition with a camera.
This test shows that new instrument design with 1.5 W heating is capable of preventing all deposition of dew. Data availability is similar to that of ventilated instruments.
Data availability improvement of pyrheliometers was also tested. Part of these tests were carried out in association with the BSRN station in Sonnblick, Austria. For pyrheliometers thermally decoupling the front window from the tube creates the possibility to heat the front window which prevents frost deposition.
The effect of small heater power on the data availability of pyrgeometers is also significant.
In many climates direct heating of pyranometers, pyrheliometers and pyrgeometers offers a practical and low-power way to improve data availability. Provided that the instrument is designed for it, it is a good alternative to external ventilation.
Determination of Top of Atmosphere Voltages and AEROSOL Optical Depth with a Yankee Environmental Systems MultiFilter Rotating Shadowband Radiometer
(Frederick M. Denn, NASA Langley/SSAI)
Removing an instrument from it’s normal measurement location has the problems of data loss, possible instrument damage in shipment, and the uncertainties introduced by performing the
calibration in an environment different than the instrument’s normal measurement environment. Keeping the instrument in place avoids these potential problems and allows for a continuous
monitoring of its condition. Here, calibration techniques are investigated and their effects on Aerosol Optical Depth (AOD) are investigated. The in place calibration technique is shown
to produce AOD as good as and often better than removing the instrument and taking it to a high mountain location for calibration.
A MultiFilter Rotating Shadowband Radiometer (MFRSR)
was deployed at the Chesapeake Light Station (CHLT) off the coast of southern Virginia, United States, at Mauna Loa Hawaii (MLO), and at NASA Langley (LaRC).
The LaRC site is at sea level and approximately 70km due west of CHLT. Three month mean values of top of atmosphere voltages (V0s) were determined at CHLT and LaRC, Eight day means were
determined for the MLO data. Multi-year fits to the three-month means were produced, and show a small decline in V0 over time. The MLO derived V0 with their associated uncertainties fall on
these multi-year fit lines.
The three-month mean V0s and separately the MLO derived V0s were then used to determine MFRSR derived AODs. These AODs were then compared to AODs provided by the
Aerosol Robotic Network (AERONET) Cimel Sun photometer. Better AOD agreement between MFRSR and AERONET was found using the three-month in place derived V0 for MFRSR, rather than
the MLO derived V0.
The value of the Solar Constant
(Steven Dewitte, IRMB)
The determination of the absolute value of the TSI - also known as the Solar Constant - is a problem of metrology. Our new best estimate of 1362.9 +/- 0.9 W/m2 at solar minimum is derived
from the revised absolute value measured by the DIARAD/SOVIM instrument on the ISS in 2008. Compared to earlier versions of the DIARAD TSI evaluation we apply a new method for the
determination of the so-called non-equivalence between electrical and optical power. This new evaluation method was validated during a laboratory measurement campaign at the LASP TRF
facility in 2013. During this same campaign we identified an underestimation of the irradiance measured by the LASP TRF cryogenic radiometer, which after elimination of all other possible
causes can only be attributed to an underestimation of the amount of scattering and diffraction occuring around the LASP TRF primary aperture. Since the TIM/SORCE space radiometer has a
similar geometry and TSI evaluation method as the LASP TRF cryogenic radiometer, this suggests that the TIM/SORCE radiometer measures a too low TSI value.Traditionally forced ventilation
is used to increase data availability. This method involves high maintenance, power consumption ( > 5 W) and induces thermal offsets.
Total Solar Irradiance measurements over the last 30 years and reconstruction over the last 300 years
(Steven Dewitte, IRMB)
The quantification of the TSI variability is important to understand whether the sun can have a significant influence on climate change on earth. A carefull analysis of the TSI
space measurements over the last 30 years indicates that within a measurement uncertainty of 0.1 W/m2 decade the long term TSI variation can be fully explained by the 'magnetic ingredients'
of sunspots and facula associated to the 11 year solar activity cycle. Further analysis of the Ca II K index measured from Mount Willson observatory for the last 100 years and of the
revised sunspot time series for the last 300 years indicates that contrary to the long-held paradigm of a 'modern grand solar maximum' we are currently in the minimum of a long term
modulation of the amplitude of the 11 year cycle; this amplitude modulation has a periodicity around 100 year.
Indoor and outdoor evaluation of global irradiance sensors
(A. Driesse, W. Zaaiman, D. Riley, N. Taylor, J. S. Stein, JRC)
Global irradiance sensors supply essential information in the business of planning and operating PV Systems. Errors and uncertainty in irradiance measurements propagate to uncertainty about
performance and profitability. PV Performance Labs initiated the PVSENSOR project in 2014 to more fully characterize commercial irradiance sensors, with the objective of reducing such uncertainties.
In the first phase of indoor testing we tested 21 pairs of instruments using multiple solar simulators (both pulsed & continuous, large area & small), environmental chambers, spectrally
selective and neutral density filters, and corresponding reference instruments. The second phase has all sensors mounted outdoors on a two-axis tracker that is programmed to follow different
trajectories while all sensor outputs are recorded. This paper provides selected results from both tests sets, highlighting differences between sensor categories.
Aerosol Optical Depth Measurements - The 4th Filter Radiometer Comparison
(S. Kazadzis, N. Kouremeti, J. Gröbner, PMOD/WRC)
This is a short presentation about Aerosol Optical depth retrieval. The role of WORCC ar PMOD on Aerosol calibration and a presentation about the ongoing 4th Filter radiometer Comparison
2015 at PMOD WRC.
(Preferable timing for the presentation towards the end of the campaign.)
Session 4: Solar Energy Applications
Towards an energy-based parameter for photovoltaic classification
(Stefan Winter, PTB)
The photovoltaic world market volume is approximately 50 billion Euros per year.
PV devices are sold according to their output power as measured under standard test conditions.
These conditions represent a cloudless sunny day in the middle of the USA, with an artificial and unrealistically
low device temperature. The climate conditions in Europe differ significantly from this and since device efficiency
depends on a combination of device properties and the environmental conditions, the current peak-efficiency metric
leads to inaccurate estimates of the energy generated under real operating conditions. Hence a classification
of PV devices regarding their energy production is urgently needed. The presentation shows the current results
of the Euramet Project "PhotoClass" on the way towards an energy-based parameter for photovoltaic classification.
The precision of solar photovoltaic power measurements doubled
(Willem Zaaiman, JRC)
An analysis carried out by JRC scientists shows that the uncertainty in measurement of power generation from a
photovoltaic (PV) cell can be more than halved, thus bringing an economic benefit to both manufacturers and
investors. With the annual world PV production exceeding 40 GW in 2014 and a market value of over €25bn, this
is good news for customers, utilities, the production industry and future R&D efforts in the field of renewable
energy.
The results have been published in the paper Reduction of uncertainties for photovoltaic reference cells,
released in time for the annual European Photovoltaic Solar Research Conference and Exhibition, held from 14
to 18 September in Hamburg, Germany.
In simple terms photovoltaic solar panels are bought and sold on the basis of their maximum power output.
Manufacturers include a margin on this value to allow for small variations in manufacturing and measurement. The
possibility to tighten this margin (typically few percent) brings an economic benefit to them and to investors. On
the R&D side, reducing uncertainty increases the possibility to clearly identify the impact of new materials and
processes. For these measurements both industry and the photovoltaics research community rely on a calibration
chain ultimately traceable to the SI (Système International d'Unités) irradiance scale. For instance the JRC has
traditionally calibrated its primary reference devices against the instrument group maintained at the world
radiometric centre (WRC) in Davos, Switzerland.
Recent updates to the world radiometric reference values to take account of improved instrumentation prompted
scientists at the JRC’s European Solar Test Installation (ESTI) labs to re-analyse the data of their five
primary reference cells (highly stable crystalline silicon devices). Using a rigorous analysis of the
uncertainties resulted in the more accurate assignment of calibration values. The uncertainty of 0.23% is a
factor of two below that of any single method. The unique ESTI reference cell set made this possible, drawing
from its 20 years of calibration history, well controlled maintenance and regular stability checks, as well as
collaboration with the world leading solar reference laboratories in Japan, USA and Europe.
The results open the way to cheaper and faster calibration of secondary reference devices for industry and
research to the same level or even lower uncertainty.
Reduction of uncertainties for photovoltaic reference cells
(Willem Zaaiman, JRC)
This paper presents the latest implementation of the ESTI reference cell set at the European solar test installation.
The set consists of five photovoltaic reference cells used to measure solar irradiance. Each cell has been calibrated
multiple times by primary methods. The stability of the set has been maintained and monitored over a long time period
(up to 20 years). Taken together this allowed a rigorous determination of the assigned calibration value for each
cell based on the weighted average, together with its uncertainty. This has led to unprecedented low uncertainties
of 0.23% (k = 2), which are at least a factor of two smaller than achievable with any single primary calibration.
Using these cells for calibrating secondary reference cells with a dedicated set-up leads to uncertainties for these
secondary calibrated cells which is of the same order as the best primary calibration methods.
ESTI CPV measurement campaign
(Germana 32, JRC)
Concentrator Photovoltaic at the European Solar Test Installation: preliminary results of the characterization of two prototype CPV modules according to the draft standard IEC62670-3.