SOLAR RESOURCE 1
Solar resource Radiation from the Sun Atmospheric effects Insolation maps Tracking the Sun PV in urban environment 2
Solar resource Solar resource is immense Human energy use: 4.0x10 14 kwh/year Solar resource on Earth s surface: 5.5x10 17 kwh/year 3
http://en.wikipedia.org/wiki/file:solar_land_area.png Solar resource Solar resource is immense Human energy use: 4.0x10 14 kwh/year Solar resource on Earth s surface: 5.5x10 17 kwh/year Local solar irradiance averaged over three years from 1991 to 1993 (24 hours a day) taking into account the cloud coverage available from weather satellites Solar power systems covering the areas defined by the dark disks could provide more than the world's total primary energy demand (assuming a conversion efficiency of 8%). 4
Solar resource Solar resource is immense Human energy use: 4.0x10 14 kwh/year Solar resource on Earth s surface: 5.5x10 17 kwh/year Solar resource is global and democratic Solar resource is relatively constant but depends on atmospheric effects, including absorption and scattering local variations in the atmosphere, such as water vapour, clouds, and pollution latitude of the location the season of the year and the time of day 5
Solar resource P 0 T 4 2 4 Rsun Total radiative power (Stefan Boltzman) T=5762K Surface area of sun Power radiated per unit area 5.96x10 7 W/m 2 6
Solar resource P 0 T 4 2 4 Rsun Ratio of surface areas of the 2 spheres Solar constant average energy flux incident at the Earth s orbit: 1366 W/m 2 S 4 R 4 D 2 sun 2 P 0 Distance Sun-Earth 7
Solar resource P 0 T 4 2 4 Rsun R sun D avg R Earth 6.96x10 5 km 1.5x10 8 km 6.35x10 3 km Energy incident on Earth Total area of Earth S S R 4 R 4 R 4 D 2 sun 2 2 Earth 2 Earth P 0 S 4 Average energy incident per unit area of surface of Earth: 342 W/m 2 8
Solar resource Earth-Sun motion 23.7 º Polar axis 365 days and 6 hours H S 360 n 2 1 0.033cos 365 H(W/m2) is radiant power density outside the atmosphere; S is solar constant; n is day of the year 9
Solar resource Earth-Sun motion Solar declination: angle between line joining centres of Earth and Sun and the equatorial plane Polar axis 0º +23º 27 10
Solar resource Earth-Sun motion Solar declination: angle between line joining centres of Earth and Sun and the equatorial plane Polar axis 0º +23º 27 Autumnal equinox 11
Solar resource Earth-Sun motion Solar declination: angle between line joining centres of Earth and Sun and the equatorial plane Polar axis 0º +23º 27 Autumnal equinox -23º 27 12
Solar resource Earth-Sun motion Solar declination: angle between line joining centres of Earth and Sun and the equatorial plane Polar axis +23º 27 0º Vernal and automnal equinox -23º 27 13
Solar resource Earth-Sun motion Solar declination: angle between line joining centres of Earth and Sun and the equatorial plane 23.45 284 n sin 2 180 365 Declination in radians; n is the number of the day (Jan 1st 14 = 1)
Solar resource Earth-Sun motion sin a sin sin cos cos sin a sin sin cosy cosa cos 0º y solar azimuth S 0º a solar elevation 90º O N E -90º 15
Solar resource Optimum orientation: facing south (north in the southern hemisphere) Optimum inclination: local latitude but not quite 16
Solar resource Atmospheric effects 17
Solar resource Atmospheric effects on solar radiation at the Earth's surface: a reduction in the power of the solar radiation due to absorption, scattering and reflection in the atmosphere; a change in the spectral content of the solar radiation due to greater absorption or scattering of some wavelengths; the introduction of a diffuse or indirect component into the solar radiation; and local variations in the atmosphere (such as water vapour, clouds and pollution) which have additional effects on the incident power, spectrum and directionality. 18
Solar resource Air Mass is a measure of the reduction in the power of light as it passes through the atmosphere and is absorbed by air and dust AM 1 cos 19
Solar resource 2,5 2,0 Wm -2 nm -1 1,5 1,0 AM0 - Extraterrestrial AM1.5 - Global AM1.5D - Direct 0,5 0,0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Wavelength (nm) 20
Solar resource F photons 2 m s 2,5 Photon flux F [photons/s/m 2 ] Power density H [W/m 2 ] E hc l 1.24 l mm Wm -2 nm -1 2,0 1,5 1,0 0,5 Spectal irradiance F [W/m 2 /mm] is the power density at a given l(mm) H F W F F 2 m mm l W H m dl 0 i 0 2 F F l hc l hc 2 l l 0,0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Wavelength (nm) 21
Solar resource 22
Solar resource 23
Solar resource Insolation: Incoming Solar Radiation Typical units: kwh/m 2 /day Affected by latitude, local weather patterns, Šúri M., Huld T.A., Dunlop E.D. Ossenbrink H.A., 2007. Potential of solar electricity generation in the European Union member states and candidate countries. Solar Energy, 81, 1295 1305, http://re.jrc.ec.europa.eu/pvgis/. 24
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Yearly sum of global irradiation on vertical surface (kwh/m 2 ) period 1981-1990 26
Yearly sum of global irradiation on horizontal surface (kwh/m 2 ) period 1981-1990 27
Yearly sum of global irradiation on optimally-inclined surface (kwh/m 2 ) period 1981-1990 28
Yearly sum of global irradiation on 2-axis tracking surface (kwh/m 2 ) period 1981-1990 29
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Solar resource Coastal areas and higher mountains face wider variations (up to 10%) Winter is much more variable (up to x6) than summer months Šúri M., Huld T., Dunlop E.D., Albuisson M., Lefèvre M., Wald L., 2007. Uncertainties in photovoltaic electricity yield prediction from fluctuation of solar radiation. Proceedings of the 22nd European Photovoltaic Solar Energy Conference, Milano, Italy 3-7.9.2007 32
Solar tracking Compared to PV with modules fixed at optimum angle: Changing inclination twice a year contributes only marginally Comparison of electricity yield from fixed and suntracking PV systems in Europe [JRC, 2008] 33
Solar tracking Comparison of electricity yield from fixed and suntracking PV systems in Europe [JRC, 2008] 34
Solar tracking Comparison of electricity yield from fixed and suntracking PV systems in Europe [JRC, 2008] 35
Solar tracking Compared to PV with modules fixed at optimum angle: Changing inclination twice a year contributes only marginally (2-4%) 1-axis tracking PV with vertical or South-inclined axis generates only 1-4% less than 2-axis tracking system 1-axis tracking PV with horizontal axis oriented E-W typically performs only slightly better than fixed mounting systems Comparison of electricity yield from fixed and suntracking PV systems in Europe [JRC, 2008] 36
kwh/wp/year Solar tracking 2000 1500 1635 1577 1537 1436 1269 1177 1000 An inclined axis tracking system orientated in the northsouth direction is able to closely follow the Sun throughout 500 the year, and have a relatively high acceptance for CPV applications. 0 The vertical 2-axes tracking, NS inclined with Vertical optimum NS inclination, hor EW hor features Fixed a similar performance that an inclined axis tracking system orientated in the north-south direction. Gaspar et al, Exploring One-Axis Tracking Configurations For CPV Application, CPV7, Las Vegas 2011 37
Solar tracking 38
Solar tracking 39
Average sum of blobal irradiation kwh/m2 Average sum of blobal irradiation kwh/m2 200% Solar tracking 150% 100% PVGIS exercise: Lisbon 50% 350 300 Fixed angle 0º Fixed angle 33º Vertical axis 33º 0% Fixed angle 0º Fixed angle 33º Vertical axis 33º Inclined axis 33º 2-axis tracking Inclined axis 33º 250 2-axis tracking 200 150 100 50 0 1 2 3 4 5 6 7 8 9 10 11 12 Month 40
Solar tracking Shadowing effect Ground cover ratio = PV area / total area Inclined tracking 2-axis tracking Horizontal tracking GCR = PV density 1 /GCR E. Narvarte et al, Tracking and Ground Cover Ratio, Prog. Photovolt: Res. Appl. 2008; 16:703 714 41
PV in urban environment Carnaxide (38.43 N, 9.8 W) N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy 42
PV in urban environment N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy 43
PV in urban environment N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy 44
PV in urban environment N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy 45
PV in urban envir http://www.fcsh.unl.pt/e-geo/energiasolar/ 46
PV in urban envir http://www.fcsh.unl.pt/e-geo/energiasolar/ 47
PV in urban envir http://www.lisboaenova.org/pt/cartasolarlisboa 48
PV in urban envir http://www.lisboaenova.org/pt/cartasolarlisboa 49
PV in urban environment Procedure for estimating the PV potential of an urban region using LiDAR data based on the Solar Analyst extension for ArcGIS. PV potential of the 538 buildings to be around 11.5 GWh/year for an installed capacity of 7MW, which corresponds to 48 % of the local electricity demand. For low PV penetration (about 10% of total roof area) the PV potential is well estimated by considering no shade and the local optimum inclination and orientation. For high PV penetration (i.e. covering close to all roof area) the PV potential is well estimated by considering a horizontal surface with the footprint area of the buildings. N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy 50
PV in urban environment 51
kwh/kwp/yr THE ROLE OF BUILDING FACADES 1600 1200 1490 LISBON OSLO 932 800 778 717 708 575 400 391 392 180150 0 Optimum tilt South facing facade East facing facade West facing facade North facing facade 52
THE ROLE OF BUILDING FACADES 40% 20% 20% 14% LISBON OSLO 0% -20% -40% -60% -29% -11% -40% -40% -45% -46% -80% -100% Comparison with horizontal surface Optimum tilt South facing facade East facing facade West facing facade -77% -86% North facing facade 53
THE ROLE OF BUILDING FACADES Solar facades? Typical 4 storey building Roof area: 10x10m 2 = 100m 2 Annual solar PV production on roof: 18.6 MWh/day (with optimum orientation/inclination) 54
THE ROLE OF BUILDING FACADES Solar facades? Typical 4 storey building Roof area: 10x10m 2 = 100m 2 Facades area: 4 facades x 4 storeys x 3m x 10m = 480m 2 Total area: 580m 2 55
THE ROLE OF BUILDING FACADES Solar facades? Typical 4 storey building Roof area: 10x10m 2 = 100m 2 Facades area: 4 facades x 4 storeys x 3m x 10m = 480m 2 Total area: 580m 2 Annual solar PV production on roof and facades: 18.6 + 38.1 = 56.7 MWh/day 56
THE ROLE OF BUILDING FACADES Solar facades? Typical 4 storey building Roof area: 10x10m 2 = 100m 2 Facades area: 4 facades x 4 storeys x 3m x 10m = 480m 2 Total area: 580m 2 Facades can Annual increase solar the PV PV production area dramatically on roof and (x5.8) facades: and, although with 38.1+ less 18.6 than = optimum 56.7 MWh/day inclination/orientation may contribute significantly to the overall production (x3). 57
THE ROLE OF BUILDING FACADES Solar facades 17% decrease in mismatch between supply and demand during sunlight hours (+32% covered area) 58
THE ROLE OF BUILDING FACADES Solar facades 19% decrease in mismatch between supply and demand during sunlight hours (+46% covered area) 59
THE ROLE OF BUILDING FACADES 60
Redweik et al, Solar Energy 97 (2013) 332 341 THE ROLE OF BUILDING FACADES 61
Redweik et al, Solar Energy 97 (2013) 332 341 THE ROLE OF BUILDING FACADES Solar facades 62Redweik et al, Solar Energy 97 (2013) 332 341
PV in urban environment Solar facades 63
THE ROLE OF BUILDING FACADES 64
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PV in urban environment Conclusions Facades can play a relevant role for PV production in the urban environment Lower production for less than optimum orientation/inclination Relatively higher production in winter Relatively higher production during earlier and later hours of the day Mutual shading of buildings needs to be taken into account GIS tools for assessment of solar potential of facades needs further development 67
Next class Further reading M. Šúri,et al, Potential of solar electricity generation in the European Union member states and candidate countries. Solar Energy, 81 (2007) 1295 1305 M. Šúri et al, Uncertainties in photovoltaic electricity yield prediction from fluctuation of solar radiation. Proc. 22nd European Photovoltaic Solar Energy Conference, Milano, Italy 2007 T. Huld et al, Comparison of Potential Solar Electricity Output from Fixed- Inclined and Two-Axis Tracking Photovoltaic Modules in Europe, Prog. Photovolt: Res. Appl. 2008; 16:47 59 E. Narvarte et al, Tracking and Ground Cover Ratio, Prog. Photovolt: Res. Appl. 2008; 16:703 714 68