pv systems and farm design
TRANSCRIPT
PV Systems and Farm Design
M. A. Alam
Electrical and Computer Engineering
Purdue University
West Lafayette, IN USA
1
Theory and Practice of Solar Cells: A Cell to System Perspective
33
Outline
1) Configurations of PV systems
2) Principles of fixed tilt farm design
3) Calculation of yearly energy yield
4) Conclusions
M. A. Alam, PV Lecture Notes
Collection of
independent
2-level PV
nm
p-n junction solar cellCell
ModulePanel
Rooftop
PVSolar farm
nm-πm cm-m km
Fabrication,
Device physics,
Manufacturing
Reliability, LCOE
Course outline: A multiscale problem
M. A. Alam, PV Lecture Notes
4
Cells, modules, panel
CC
Charge
controller
Battery/
storage
Inverter
AC
source/
grid
Distribution
panel
System Integration: Sysmbols
M. A. Alam, PV Lecture Notes
6
Stand-alone PV systems
Simple
Low cost
Calculators
Irrigation
More expensive
Off-grid
Many home PV
Variety of electronicsM. A. Alam, PV Lecture Notes
7
Solar homes: Grid-connected PV
Hybrid:
Multiple sources
Both AC/DC loads
PV connected to
Power-grid
M. A. Alam, PV Lecture Notes
8
Community PV: Microgrid and Solar Farms
M. A. Alam, PV Lecture Notes
9
Power
optimizer
Aside: Inverter configurations
Central Micro String Micro with
Power-optimizerM. A. Alam, PV Lecture Notes
10
1212
Outline
1) Configurations of PV systems
2) Principles of fixed tilt farm design
3) Calculation of yearly energy yield
4) Conclusions
M. A. Alam, PV Lecture Notes
0
100
200
300
4001300
1350
1400
1450
J F M A M J J A S O N DMonth
ly
(kW
-hr/m
2)
πΌ 0(W
/m2)
Extra-
terrestrial
Monthly GHI
πΌ0(ππ) = πΌ0(1 + Ξ cos 2π ππ /π·)
Ξ = 2(π maxβ π min)/π
Sunlight varies with seasons
13
How to tilt a solar module (i.e. determine π½)
πΌπ½ππ§
πΌπππ = πΌπ sin πΌ + π½ = πΌπ cos(ππ§ β π½)
πΌπ
M. A. Alam, PV Lecture Notes 14
ππ§ varies throughout the year
πΏ = 23.450 sin2π π β 80
365
πΌ
ππ§πΏ
πΌ(π) = 90 β πΏ Β± πΏ(π)
ππ§(π) = πΏ β πΏ(π)
North
South
ππ§,π€ = πΏ + 23.45
ππ§,π = πΏ β 23.45
Ξ΄ β‘ Sun declination angle
March 21st (Vernal
Equinox)β‘ 80 days
An empirical rule for tilt
ππ§(π) = πΏ β πΏ(π)
ππ§,π€ = πΏ + 23.45
ππ§,π = πΏ β 23.45
π½ = πΏ β 10
π½ = 0.69πΏ + 3.7
π½π = ππ§,π π½π€ = ππ§,π€
Optimize integral over daily
intensity and solar angle for given π½
Summer intensity is higher:
Two tilt, summer/winter:
π½
16
Example: How to tilt a module
π½ = πΏ β 10 30.27 3.50 21.23
π½ = 0.69πΏ + 3.6 31.79 12.92 24. 83
π½π = ππ§,π
Lafayette Madras Shanghai
40.27π 13.5 π 31.23 π
π½π€ = ππ§,π€ 63.72
16.82
36.95
β9.95
54.68
7.78
17
18
Tilt angle, Electrical vs. mechanical, Air vs. water cleaning
Aside: Cleaning considerations
M. A. Alam, PV Lecture Notes
Three components of irradiance
19
πΌπ = πΌπππ + πΌππππ + πΌπππππ = πΌπΊπ»πΌ/πΌ0cos(ππ)
Standalone yield: Direct light
πΌπ½ππ§
πΌπππ = πΌπ sin πΌ + π½ = πΌπ cos ππ§ β π½
πΌπ = πΌπππ + πΌππππ + πΌπππ
πΌπ
M. A. Alam, PV Lecture Notes 20
Stand-alone yield: diffuse component
π½
πΌππππ =πΌπ2ΰΆ±π½
π
sin π ππ =πΌπ 1 + cos π½
2
πΌπ = πΌπππ + πΌππππ + πΌπππ
πΌπ
π½
πΌπ
21M. A. Alam, PV Lecture Notes
Stand-alone yield: albedo
π½
πΌπ = πΌπππ + πΌππππ + πΌπππβ
ππΉ =π1 + π2 β π3 + π4
2β
π1
π2
π3
π4
ππΉ =β + π β (0 + π 2 + β2 + 2π β cos π½)
2β
ππΉ =1
21 + π β 1 + π2 + 2π cos π½ β (1 β cos π½)/2
π = Ξ€π β β β
π
β
πΌπππ = πΌπΊπ»πΌ π π΄ ππΉ
M. A. Alam, PV Lecture Notes 22
Stand-alone module: Energy yield
πΌπ½ππ§
πΌπππ = πΌπ cos(ππ§ β π½)
πΌπ
πΌππππ =πΌπ 1 + cos π½
2
πΌπππ = πΌπΊπ»πΌ π π΄(1 β cos π½)/2
πΌπ = πΌπππ + πΌππππ + πΌπππ
23M. A. Alam, PV Lecture Notes
Summer zenith: πππ Winter zenith: πππ€
πππ πππ€
ββπ¦
βπ₯πππ€
ππ
π
π½
Row spacing in Lafayette, IN
SBR β‘ ππ /βπ¦ = tan 90 β πΌ = tan ππ§π€,π
π/β = cos(π½) + sin(π½) tan ππ§π€,π
SBR β‘ ππ /βπ¦ = tan 90 β 18.14 =3.05
M. A. Alam, PV Lecture Notes 27
Farm yield per unit area: direct beam
πΌπ½ππ§
πΌπππ = πΌπ sin πΌ + π½ β/π = πΌπ cos ππ§ β π½ Γ β/π
πΌπ = πΌπππ + πΌππππ + πΌπππ
πΌπ
π
β
M. A. Alam, PV Lecture Notes 30
Farm yield: diffused energy collection
π½
πΌπ = πΌπππ + πΌππππ + πΌπππ
πΌπ
πΌ + π½
πΌπ
πΌ
πΌππππ(π) =π
βΓπΌπ2ΰΆ±π½+πΌ(π)
π
sin π ππ =π
βΓπΌπ 1 + cos(πΌ +π½ )
2
M. A. Alam, PV Lecture Notes 31
3333
Outline
1) Configurations of PV systems
2) Principles of fixed tilt farm design
3) Calculation of yearly energy yield
4) Conclusions
M. A. Alam, PV Lecture Notes
Variety of Solar Farms
M. A. Alam, PV Lecture Notes 34
-80 -60 -40 -20 0 20 40 60 800
20
40
60
80
-80 -60 -40 -20 0 20 40 60 800
1
2
3
4
-80 -60 -40 -20 0 20 40 60 800
12345
period
Row spacing
Northern hemisphere,
South facing panels
Southern hemisphere,
North facing panels
Latitude (deg.)
SBR
(m)
Pan
el tilt (
deg.
)
Yearly Yield (kW-hr/m2)
Monofacial solar farms
M. A. Alam, PV Lecture Notes
35
W
Albedo contribution to Monofacial Farms
β’ π π΄ = 0.2β’ 1-2 % gain in YY
β’ 1-2o increase in optimum tilt angle
β’ < 1% reduction in LCOE*
M. A. Alam, PV Lecture Notes
36
(c) (d)
1 2
(e) (f)
π
βπ
0 1 2 30.1
0.2
0.3
0.4
0.5
p/h
Daily
Energ
y/farm
are
a
(kW
-hr/
m2)
(g) (h)
π = 0
π = 0.5β
(a)(i)
(a)(ii)
0
20
40
Impro
vem
ent,
%0.4 0.45 0.5 0.55 0.6 0.65
80
100
120
140
160
Annual mean-clearness indexA
nnual Y
ield
(kW
-hr/
m2)
Monofacial
(10% soiling loss)
Latitude 40 N
GvBF vs. mono
GvBF vs. vBF-1
-180-120-60
060
120180
Longitude
(b)
W
Ground-sculpted bifacial farms
M. A. Alam, PV Lecture Notes
39
Land-cost inclusive optimization
40
(a) = 0 = 15(b) (c) = 100
M. A. Alam, PV Lecture Notes
4141
Conclusions
PV design must be understood in a system context.
Given the weather information, it is relatively easy to
calculate the energy yield for stand-alone modules as
well as solar farms.
The increasing cost of land and wide-spread PV
deployment are encouraging the PV industry to
explore novel technologies (e.g. bifacial PV) and farm
topologies (e.g. floating solar).
An end-to-end cost-benefit analysis is essential to
create a farm that is ideally suited to a location. M. A. Alam, PV Lecture Notes
Self-study Quiz
Which direction does 90 degrees Azimuth indicate?
Names the light-components one must sum to calculate the
energy yield.
What is the cross-string method? Why do we need this
technique?
How does the albedo light collection by a module in a farm
compare to that of an stand-alone module?
What type of solar benefit the most from ground-sculpting?
When should one use floating solar farms compared to
normally tilted solar farms?
42
M. A. Alam, PV Lecture Notes