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Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 1/12
OnOn thethe webweb
Course webpage!http:// solar.fc.ul.pt/PV_course
PV bloghttp://solar-fcul blogspot comhttp://solar-fcul.blogspot.com
Group page: http:// solar.fc.ul.pt
OnOn thethe webweb
Solar Solar resourceresource
Radiation from the Sun Atmospheric effects Insolation maps Tracking the Sun Tracking the Sun
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 2/12
Solar Solar resourceresource Solar resource is immense
◦ Human energy use: 4.0x1014 kWh/year
◦ Solar resource on Earth’s surface: 5.5x1017 kWh/year
Solar Solar resourceresource Solar resource is immense
◦ Human energy use: 4.0x1014 kWh/year
◦ Solar resource on Earth’s surface: 5.5x1017 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
Solar Solar resourceresource
2
4
0 4 sunR
TP
Total radiative power (Stefan Boltzman) T=5762K
Surface area of sun
Power radiated per unit area5.96x107 W/m2
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 3/12
Solar Solar resourceresource
2
4
0 4 sunR
TP
02
2
4
4P
D
RS sun
Ratio of surface areas of the2 spheres
Distance Sun-Earth
Solar constant averageenergy flux incident at theEarth’s orbit: 1366 W/m2
Solar Solar resourceresource
2
4
0 4 sunR
TP
Rsun 6.96x105 km
Davg 1.5x108 km
REarth 6.35x103 km
44 2
2 S
R
RS
Earth
Earth Energy incident on Earth Average energy incident
per unit area of surface ofEarth: 342 W/m2Total area of Earth
02
2
4
4P
D
RS sun
Solar Solar resourceresource Earth-Sun motion
23.7 º
Polar axis
365 days and 6 hours
365
2360cos033.01
n
S
H
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 4/12
Solar Solar resourceresource Earth-Sun motion◦ Solar declination: angle between line joining centres of Earth and Sun and
the equatorial plane
Polar axis
+23º 27’
-23º 27’
0º Vernal andautomnal equinox
Solar Solar resourceresource Earth-Sun motion◦ Solar declination: angle between line joining centres of Earth and Sun and
the equatorial plane
365
2842sin
180
45.23 n
Solar Solar resourceresource Earth-Sun motion
– solar elevation
coscos
sinsinsincos
coscossinsinsin
E
O
S
N
0º– solar azimuth
0º
-90º
90º
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 5/12
Solar Solar resourceresourceAtmospheric effects
Solar Solar resourceresourceAtmospheric 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.
Solar Solar resourceresource Air Mass is a measure of the reduction in the power
of light as it passes through the atmosphere and isabsorbed by air and dust
cos
1AM
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 6/12
Solar Solar resourceresource
1.5
2.0
2.5
AM0 - Extraterrestrial
AM1.5 - Global
0.0
0.5
1.0
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Wm
-2n
m-1
Wavelength (nm)
AM1.5D - Direct
Solar Solar resourceresource
1.5
2.0
2.5 Photon flux [photons/s/m2]
Power density H [W/m2]
Spectal irradiance F [W/m2/m] is the power density at a given(m)
sm
photons2
hW
hc
m
WH
2
m
hcE
24.1
0.0
0.5
1.0
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Wm
-2n
m-1
Wavelength (nm)
00 i
FdFH
22 hc
mm
WF
Solar Solar resourceresource
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 7/12
Solar Solar resourceresource
Solar Solar resourceresource Insolation: Incoming Solar Radiation
Typical units: kWh/m2/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 the2007. 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/
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 8/12
Yearly sum of global irradiation on vertical surface (kWh/m2)period 1981-1990
Yearly sum of global irradiation on horizontal surface (kWh/m2)period 1981-1990
Yearly sum of global irradiation on optimally-inclined surface (kWh/m2)period 1981-1990
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 9/12
Yearly sum of global irradiation on 2-axis tracking surface (kWh/m2)period 1981-1990
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 10/12
Solar Solar resourceresource Coastal areas and higher
mountains face widervariations (up to 10%)
Winter is much more variable (up to x6) than
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
summer months
Solar Solar trackingtrackingCompared 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]
Solar Solar trackingtracking
Comparison of electricity yield from fixed and suntracking PV systems in Europe [JRC, 2008]
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 11/12
Solar Solar trackingtracking
Comparison of electricity yield from fixed and suntracking PV systems in Europe [JRC, 2008]
Solar Solar trackingtrackingCompared 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]
250
300
350
n k
Wh
/m2
Fixed angle 0º
Fixed angle 33º
Vertical axis 33º
Inclined axis 33º
2-axis tracking
0%
50%
100%
150%
200%
Fixed angle 0º
Fixed angle 33º
Vertical axis 33º
Inclined axis 33º
2-axis tracking
Ave
rag
e su
m o
f b
lob
al i
rrad
iati
on
kW
h/m
2
Solar trackingSolar tracking
PVGIS exercise: Lisbon
0
50
100
150
200
1 2 3 4 5 6 7 8 9 10 11 12
Ave
rag
e su
m o
f b
lob
al i
rrad
iati
on
Month
Solar resource, 6/10/2009Energia Solar Fotovoltaica, MC Brito
Mestrado Integrado Engenharia da Energia e do Ambiente, Faculdade Ciências da Universidade de Lisboa, 12/12
Solar Solar trackingtrackingShadowing effect
Ground cover ratio = PV area / total area
Inclinedtracking
2-axis tracking
E. Narvarte et al, Tracking and Ground Cover Ratio, Prog. Photovolt: Res. Appl. 2008; 16:703–714
Horizontal tracking
g