PV SYSTEMS: APPLICATIONS · Solar tracking Compared to PV with modules fixed at optimum angle: Changing inclination twice a year contributes only marginally (2-4%) 1-axis tracking

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: 4.0x1014 kWh/year

◦ Solar resource on Earth’s surface: 5.5x1017 kWh/year

3

Solar resource




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%).

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

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Solar resource




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

2

4

04 sunR

TP

Total radiative power (Stefan Boltzman) T=5762K

Surface area of sun

Power radiated per unit area

5.96x107 W/m2

6

Solar resource

2

4

04 sunR

TP

02

2

4

4P

D

RS sun

Ratio of surface areas of the 2

spheres

Distance Sun-Earth

Solar constant average energy

flux incident at the Earth’s orbit:

1366 W/m2

7

Solar resource

2

4

04 sunR

TP

Rsun 6.96x105 km

Davg 1.5x108 km

REarth 6.35x103 km

44 2

2S

R

RS

Earth

Earth

Energy incident on EarthAverage energy incident per

unit area of surface of Earth:

342 W/m2Total area of Earth

02

2

4

4P

D

RS sun

8

Solar resource

Earth-Sun motion

23.7 º

365 days and 6 hours

Polar axis

365

2360cos033.01

n

S

H

H(W/m2) is radiant power density outside the atmosphere; S is solar constant; n is day of the year9

Earth-Sun motion◦ Solar declination: angle between line joining centres of Earth and Sun and the

equatorial plane

Solar resource

Polar axis

+23º 27’0º

10

Solar resource

Polar axis

+23º 27’0º

Autumnal equinox


equatorial plane

11

Solar resource

Polar axis

+23º 27’0º

Autumnal equinox


equatorial plane

-23º 27’

12


equatorial plane

Solar resource

Polar axis

+23º 27’0º Vernal and

automnal equinox

-23º 27’

13

Solar resource


equatorial plane

365

2842sin

180

45.23 n

Declination in radians; n is the number of the day (Jan 1st = 1)14

Solar resource

Earth-Sun motion

E

O

S

N

a – solar elevation

0ºy – solar azimuth

0º

-90º

90º

a

ay

a

coscos

sinsinsincos

coscossinsinsin

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

cos

1AM

19

Solar resource

0,0

0,5

1,0

1,5

2,0

2,5

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wm

-2n

m-1

Wavelength (nm)

AM0 - Extraterrestrial

AM1.5 - Global

AM1.5D - Direct

20

Solar resource

0,0

0,5

1,0

1,5

2,0

2,5

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Wm

-2n

m-1

Wavelength (nm)

Photon flux F [photons/s/m2]

Power density H [W/m2]

Spectal irradiance F [W/m2/mm] is

the power density at a given

l(mm)

sm

photons2

F

00 i

FdFH llll

22 lm

hc

mm

WF F

l

hc

m

WH F

2

m

hcE

mll

24.1

21

Solar resource

22

Solar resource

23

Solar resource

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 the European

Union member states and candidate countries. Solar

Energy, 81, 1295–1305, http://re.jrc.ec.europa.eu/pvgis/.

24

25

Yearly sum of global irradiation on vertical surface (kWh/m2)

period 1981-1990

26

Yearly sum of global irradiation on horizontal surface (kWh/m2)

period 1981-1990

27

Yearly sum of global irradiation on optimally-inclined surface (kWh/m2)

period 1981-1990

28

Yearly sum of global irradiation on 2-axis tracking surface (kWh/m2)

period 1981-1990

29

30

31

Solar resource

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

Coastal areas and higher

mountains face wider

variations (up to 10%)

Winter is much more

variable (up to x6) than

summer months

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


Solar tracking


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


16351577 1537

1436

12691177

0

500

1000

1500

2000

2-axes NS inclined Vertical NS hor EW hor Fixed

kW

h/W

p/y

ea

rSolar tracking

Gaspar et al, Exploring One-Axis Tracking Configurations For CPV Application, CPV7, Las Vegas 2011

•An inclined axis tracking system orientated in the north-

south direction is able to closely follow the Sun throughout

the year, and have a relatively high acceptance for CPV

applications.

•The vertical tracking, with optimum inclination, features a

similar performance that an inclined axis tracking system

orientated in the north-south direction.

37

Solar tracking

38

Solar tracking

39

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12

Avera

ge s

um

of

blo

bal

irra

dia

tio

n k

Wh

/m2

Month

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

Avera

ge s

um

of

blo

bal

irra

dia

tio

n

kW

h/m

2

Solar tracking

PVGIS exercise: Lisbon

40

Solar tracking

Shadowing effect

Ground cover ratio = PV area / total area

E. Narvarte et al, Tracking and Ground Cover Ratio, Prog. Photovolt: Res. Appl. 2008; 16:703–714

Horizontal

tracking

Inclined

tracking

2-axis

tracking

GCR = PV density

1 /GCR

41


N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy

Carnaxide (38.43° N, 9.8 W)

42


N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy 43





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


N. Gomes et al, PV potential in urban environment using LIDAR data, 2010, Solar Energy

• 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.

50


51

THE ROLE OF BUILDING FACADES

1490

932

717 708

180

778

575

391 392

150

0

400

800

1200

1600

Optimum tilt South facing

facade

East facing

facade

West facing

facade

North facing

facade

kW

h/k

Wp

/yr

LISBON

OSLO

52


14%

-29%

-45% -46%

-86%

20%

-11%

-40% -40%

-77%

-100%

-80%

-60%

-40%

-20%

0%

20%

40%

Optimum tilt South facing

facade

East facing

facade

West facing

facade

North facing

facade

LISBON

OSLO

Comparison with

horizontal surface

53


Solar facades?

Typical 4 storey building

Roof area:

10x10m2 = 100m2

Annual solar PV production on roof:

18.6 MWh/day

(with optimum orientation/inclination)

54

Solar facades?


Roof area:

10x10m2 = 100m2

Facades area:

4 facades

x 4 storeys

x 3m

x 10m = 480m2

Total area:

580m2


55

Solar facades?


Roof area:

10x10m2 = 100m2

Facades area:

4 facades

x 4 storeys

x 3m

x 10m = 480m2

Total area:

580m2

Annual solar PV production on roof and facades:

18.6 + 38.1 = 56.7 MWh/day


56

Solar facades?


Roof area:

10x10m2 = 100m2

Facades area:

4 facades

x 4 storeys

x 3m

x 10m = 480m2

Total area:

580m2

Annual solar PV production on roof and facades:

38.1+ 18.6 = 56.7 MWh/day

Facades can increase the PV area dramatically (x5.8) and,

although with less than optimum inclination/orientation may

contribute significantly to the overall production (x3).


57

17% decrease in mismatch between supply and demand during sunlight

hours (+32% covered area)

Solar facades


58

19% decrease in mismatch between supply and demand during sunlight

hours (+46% covered area)

Solar facades


59


60


Redw

eik

et

al, S

ola

r Energ

y97 (

2013)

332–341

61

Solar facades


Redw

eik

et

al, S

ola

r Energ

y97 (

2013)

332–341

Redw

eik

et

al, S

ola

r Energ

y97 (

2013)

332–341

62


Solar facades

63


64

65

66


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 readingM. 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

Documents

PV SYSTEMS: APPLICATIONS · Solar tracking Compared to PV with modules fixed at optimum angle: Changing inclination twice a year contributes only marginally (2-4%) 1-axis tracking