Solar resource assessment luis martin

• 1. Luis Martn PomaresIrSOLaVCalle Santiago Grisolia n2, 28760 Tres Cantos (Madrid)[email protected] / www.solarexplorer.info

2. Introduction Solar resources evaluation is a necessary first step for thestudy of any energy system. The objective is the determination of the solar radiationcollected in a specific site, for its use in a specific solartechnology. As inputs, it is necessary to have information related to thesource and to the technology. The methodologies can be classified as: classical evaluation(from measurements), and evaluation from satellite images. 3. Procedure proposedTime seriesHourly, monthlyWhat do I need? Global, DNIMapsFor what: Report, modelingNoSatellite information Measurements?Any other approachYesOk?Solar resource knowledge 4. Solar radiation characteristics Solar energy reaches the earth ina discontinuous form, showingcycles or periods: Daily cycle: accounts for 50% ofthe total availability of daily hours. Another effect of the daily cycle isthe modulation of the receivedenergy throughout the day. Seasonal cycle: modulation of thereceived energy throughout theyear. 5. Solar constant and solar geometry Is the amount of solar energy incident in 1 m2 of surface perpendicularly exposed to the solar rays and placed at 1 AU of distance. Changes slightly with time, but can be considered as constant Ion = 1367 W/m2.(WRC).Solar geometry is well knownWe can estimate with high accuracy the solar irradiation at the topof the atmosphere at every moment and every place 6. Interaction of solar radiation withthe atmosphereRadiation at the top of atmosphere Absorption (ca. 1%)Ozone...... Rayleigh scattering and absorption (ca. 15%)Air molecules..Scatter and Absorption (ca. 15%, max. 100%)Aerosol...... Clouds...Reflection, Scatter, Absorption (max. 100%) Water Vapor....Absorption (ca. 15%)Direct normal irradiance at ground 7. Solar Geometry The position of the Sun can be calculated suingthe following trigonometric equations:ZENITH Cenital angle (z) or itsSOLTRAYECTORIA SOLAR complementary solar angle ()(+) MAANA W 1(-) ESTEzzz cos sin sincos coscos - SN0 + Azimutal angle ():PROYECCION DE LA 1TRAYECTORIA SOLARsin cos sin / sin zE 8. Solar radiation componentsRADIATION REFLECTED BY CLOUDSGROUND ALBEDO ABSORPTIONSCATTERINGDIRECT NORMAL RADIATIONDIFUSE RADIATION 9. Ley of BeerIn I 0 e( k L) I 0 e(m)I0 TInIn d I 0 e( k L) dISC emClear sky models or transmitance models BnI CS (TRToTgTwTa0.013) YangC Bn ICS exp[ 0.8662 TLAM 2 mp R ] ESRA 10. The concept of optical massAproximation to plane-parallel 1 m cos Karsten equation1.253 1m (sin 0.15( 3.885) ) 11. Air mass: variability 35 30 25 Masa relativa de aire 20 15 10 5 04 6 8 10 12 14 16 18 20 12. Sensibility of ESRA model to TLInfluence of TLINKE and altitude above sea level on DNI for clear skyDia juliano=200, z=500, Lat=37 N Long=-2 ETL=4, dia juliano=200, Lat=37 N Long=-2 E 12001000TL=2 z=0 mTL=4 900 z=500 m 1000 TL=6 z=1000 m 800 700 800DNI (Wh m-2) 600DNI (Wh m-2) 600 500 400 400 300 200 200 100 0 00 2 46 81012 14 1618 20 22 24 0 51015 2025 HoraHora 13. Components and non-dimensioanl indexesComponents of solar radiation in horizontal surfaceIGIB cos IDClear sky or transparency indexIG ktI0Difuse radiation fractionID kdIGBeam radiation transmitanceIB kbI0 14. Estimation of beam solar radaition Correlations to estimate difuse radiation fractionG (1 kd ) Ib 1.0 0.09ktkt0.22 sen( )kd 0.9511 1.1604kt0.165 kt 0.84.388kt 2 16.638kt 3 12.336kt 4 0.22 kt 0.8 Correlations to estimate beam transmitance Ib kb I okb0.002 0.059kt0.994kt 2 5.205kt 3 15.307kt 4 10.627kt 5 15. Measuring Solar Radiation:Pyrheliometers EKO MS-54 Measures direct beam irradiance Typically used for calibration transfersMiddleton DN5 Normally defined with an opening angle of 5 If used in conjunction with pyranometers, the opticalflat protecting entrance should match the opticalmaterial of the pyranometer domes Relatively easy to characterize 4 major manufacturers: EKO Instruments (Japan) Eppley Instruments (USA) Kipp & Zonen (Netherlands) Middleton Solar [Carter Scott Design] (Australia) Normally mounted on passive or active solartracking systems 16. Measuring Solar Radiation: PyranometersTilted Irradiance Most pyranometers use a thermopile as means of converting solar irradiance into an electrical signal. Silicon cell pyranometers are also available, but are not recommended by WMO. Advantage of the thermopile is that it is spectrally neutral across the entire solar spectrum (domes may have spectral dependencies). Disadvantage is that the output is temperature dependent and the instruments must create a cold junction. 17. Measuring Solar Radiation: Silicon Pyranometers Instruments spectral response is non-linear and does not match solar spectrum. General calibrations are through comparison with pyranometers, therefore thereare spectral mismatch problems. LiCor is the primary instrument manufacturer and recognizes these problems:The spectral response of the LI-200 does not include the entire solar spectrum,so it must be used in the same lighting conditions as those under which it wascalibrated.Pyranometer sensors are calibratedagainst an Eppley Precision SpectralPyranometer (PSP) under natural daylightconditions. Typical error under theseconditions is 5%. (LiCor)Similar problems arise when usingsensors calibrated in one climate regimeand used in a different regime. 18. Rotating Shadowband Radiometer RSR2 LI-COR Terrestrial Radiation Sensors Irradiance Inc. (www.irradiance.com) LI-200 Pyranometer is a silicon photodiodecalibrated from LI-COR 5% RSR2 Head unit includes a moving shadowbandthat momentarily casts a shadow over a LI-200pyranometer Motor controller contains circuit to control theexact movement of shadowband LI-200 Pyranometer Correction provided by Algorithm Measurement:Global Horizontal Irradiance Diffuse Horizontal Irradiance Calculation: Direct Normal Irradiance RSR2 HeadunitRSR2 Motor Controller 19. Measuring Solar Radiation:Typical BSRN-like stations 20. Measurement recomendations Know exactly what temporal reference of the masurementsyou are using (TSV, GMT, Local etc) Register with enough temporal resolution, almost 10 minutesto register the dinamic of cloud transients. Follow BSRN recomendation for maintenance of instruments.Cleaning every day radiometers, calibrate once per year eachinstrument, Secure the relation G=B cos + D. Some solar trackers haveembeded this filter in its program to activetes realtime alarmswhen measurement is worng. 21. Meteorological Satellite population 22. Satellite classificationAccording to the type of orbit :Polar satellites: placed in polarorbits, modifying its perspectiveand distance to the earth. Theresolutions of these satellites arearound 1m to 1km.Geostationary satellites: placed in the geostationary orbit that is, the place in the space where the earths attraction force is null. It is an unique circumference where all the geostationary satellites are situated in order to cover the whole earths surface. The resolutions of these satellites are higher in the sub satellite point on the equator, and go decreasing in all directions. 23. Meteosat Satellite coverageMeteosat PrimeMeteosat East Spatial resolution 2.5 km at sub satellite, eg. About 3x4 km in Europe Temporal resolution 1h. Current Coverage: Meteosat Prime up to 1991-2005,Meteosat East 1999 - 2006 24. Solar radiation derived from satellite imagesSatellite to irradiance: general procedure Meteosat Goes - Mtsat 60, 30 or 15 images in the visible position assessement geometric corrections pixels averaging model to obtain global irradiance 25. AOD (Aerosol Optical Depth estimations)Estimations from MODIS (Moderate Resolution Imagingspectroradiometer) on NASAs Terra satellitehttp://earthobservatory.nasa.gov/AOD and water vapor vertical content estimations from satellite 26. Radiometric Databases Baseline Surface Radiation Network (BSRN) 27. Radiometric Databases Baseline Surface Radiation Network (BSRN) World radiation data centre (WRDC) Meteonorm 28. SSERadiometric Databases: SSE from NASAhttp://eosweb.larc.nasa.gov/sse / Surface Meteorology and Solar Energy (SSE) Datasets And Web interface Monthly data Free upon registrationGrowing over the last 7 years to nearly 14,000 1x1 (120x120users, nearly 6.4 million hits and 1.25 milliondata downloads km) resolution 29. Solar radiation derived from satellite imagesSWERA ProjectThe SWERA project provides easy access to high quality renewable energy resource informationand data to users all around the world. Its goal is to help facilitate renewable energy policy andinvestment by making high quality information freely available to key user groups. SWERAproducts include Geographic Information Systems (GIS) and time series data 30. Comercial data from satellite Irsolav Solemi (DLR) 3Tier Solargis . 31. Some measurements in India 32. Some measurements in India 33. Some measurements in India 34. IrSOLaV activities Ciemat promoted a spin-off company for solar resourcecharacterization services (www.irsolav.com). Thus IrSOLaVinteracts with the industry needs and supply data andconsulting services on solar resource and also collaborateswith Ciemat in R&D. IrSOLaV and Ciemat develops R&D programs in the solarresource field and collaborates with international scientificgroups (DLR, NREL, NASA, JRC, CENER, Universities)through European projects (COST project) or other initiatives(Task 46 SHC/IEA) Within Spain IrSOLaV and CIEMAT collaborates withuniversities (UAL, UJA, UPN) and support the industry throughagreements for doing specific research on solar resourceknowledge (forecasting, model improvements, atmosphericphysics, etc) 35. THANKS FOR YOUR ATTENTION !