The document provides an overview of solar energy, including its current status and future trends. It discusses how solar energy capacity has grown exponentially in recent decades. While most solar cells are currently made from silicon wafers, which require significant energy to produce, new thin-film technologies under development could reduce material and energy needs. The document also examines challenges like energy storage and grid integration given solar's variability, and how combining solar with wind can help address these issues. In conclusion, it emphasizes solar energy's immense potential to provide clean energy at localized costs competitive with fossil fuels.

1. #UNIT FESTIVAL 2016
Berlin, Saturday 16 April
Klaus Jäger
Helmholtz-Zentrum Berlin
Solar energy
current status and future trends
Sunset in Æerøskøbing, Denmark
© 2015 by Klaus Jäger

3. We live in a remarkable age, driven by fossil fuels.
Figure adapted from a figure by Wim Sinke, ECN, The Netherlands 3
-2000 0 2000 4000 6000
Useoffossilfuels
Year
we, now

4. Almost all energy consumed by mankind
originates from the Sun.
Movie: A solar eruption on November 16, 2012; taken from www.nasa.gov 4
solar
94.0%
geothermal
0.2%
nuclear
5.8%

5. Fossil fuels account for about 86% of the
consumed energy originating from the Sun.
Data for 2013, IEA 2015 Key World Energy Statistics 5

6. Consuming fossil fuels is like using a battery,
which we cannot recharge!
6Data for 2013, IEA 2015 Key World Energy Statistics

7. GHI(kWh/m2/day)
7
6
5
4
3
2
1
90°
60°
30°
0°
-30°
-60°
-90°
150°120°90°60°30°0°-30°-60°-90°-120°-150°-180°
We receive from the Sun about 10 000 times the
total human power consumption.
Data: https://eosweb.larc.nasa.gov/cgi-bin/sse/sse.cgi?skip@larc.nasa.gov 7

8. Small areas are sufficient to supply
all humankind with electricity.
Area required for electricity supply. Diplomarbeit Nadine May, TU Braunschweig in collaboration with DLR (2005) 8

9. Photovoltaic (PV) solar cells can convert light
directly into electricity.
9Picture: Tomas van Dijk, TU Delta, www.delta.tudelft.nl (2011)

10. Where are we now?

11. 11
GlobalinstalledPVcapacityinGWIt took until 2010, to install the first 40 GW
of photovoltaic (PV) modules.
2010
Source: BP, Statistical Review of World Energy; IRENA Renewable Capacity Statistics 2016
Graphic: Alexander Franke, @al_f on Twitter

12. 12
GlobalinstalledPVcapacityinGWBy the end of 2012, more than 100 GW
had been installed.
2012
Source: BP, Statistical Review of World Energy; IRENA Renewable Capacity Statistics 2016
Graphic: Alexander Franke, @al_f on Twitter

13. 13
Source: BP, Statistical Review of World Energy; IRENA Renewable Capacity Statistics 2016
Graphic: Alexander Franke, @al_f on Twitter
GlobalinstalledPVcapacityinGWNow, more than 40 GW are installed every year!
2015

14. 14
Source: BP, Statistical Review of World Energy; IRENA Renewable Capacity Statistics 2016
Graphic: Alexander Franke, @al_f on Twitter
GlobalinstalledPVcapacityinGWNow, more than 40 GW are installed every year!
Between 1997
and 2015 the
average annual
growth was 43%!

15. 15
Photovoltaics has the largest growth rate of non-
fossil electricity generation technologies!
Cu
pe
Solar
1980 1990 2000 2010 2020
0.1
1
Effectiveinstalledcapacity(GW)
1980 1990 2000 2010 2020
0.1
1
10
100
1000
Solar (CF
=0.15)
Wind (CF
=0.30)
Nuclear (CF
=0.90)
Hydro (CF
=0.40)
(b)
Figure: A. Smets, K. Jäger, et al.,“Solar Energy”(UIT Cambridge, 2016)
CF … capacity factor

16. 16
In 2015, more than 7% of electricity was generated
by PV in Germany, Greece, and Italy.
Figure: 2015 Snapshot of Global Photovoltaic Markets - IEA PVPS

17. 17
The levelized cost of solar electricity in
Germany is already now competitive.
Figure: Levelized Cost of Electricity Renewable Energy Technologies Study, Fraunhofer ISE (November 2013)

18. How do solar cells work?

19. Solar cells can convert light directly into
electricity using the photovoltaic effect.
absorber
Inspired by Würfel, Physics of Solar Cells (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005) 19

20. A photon leads to the generation of
an electron and a hole in the absorber.
electronhole
generationabsorber
Inspired by Würfel, Physics of Solar Cells (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005) 20

21. Electrons and holes will travel
around until they recombine.
21
recombination
Inspired by Würfel, Physics of Solar Cells (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)

22. Semi-permeable membranes allow to separate
electrons from holes before they recombine.
22
separation
semipermeable membran
(permeable for electrons only)
semi-permeable membrane
(permeabel for holes only)
Inspired by Würfel, Physics of Solar Cells (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)

23. The energy stored in the electron-hole pairs can
be used to drive an electric circuit.
23
extraction
Inspired by Würfel, Physics of Solar Cells (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2005)

24. of Ch
lateri
grani
ern C
geous
HRE
with
extra
Th
alread
cal pr
years
and r
most
tains
Th its
comp
ate da
that c
Conc
now
For large scale application, the solar cells must
be made from abundant materials.
24U.S. Geological Survey, USGS Fact Sheet 087-02 (2002)

25. of Ch
lateri
grani
ern C
geous
HRE
with
extra
Th
alread
cal pr
years
and r
most
tains
Th its
comp
ate da
that c
Conc
now
Silicon solar cells fulfil this requirement.
25U.S. Geological Survey, USGS Fact Sheet 087-02 (2002)

26. More than 90% of all solar cells are made from
silicon wafers.
26
≈200μm
front contact
(metal grid)
serial connections
(to the back contact
of the next cell)
n+
-type emitter
p+
-type layer
antireflective
coating
p-type wafer
back contact
Figure: A. Smets, K. Jäger, et al.,“Solar Energy”(UIT Cambridge, 2016)

27. The efficiency record achieved with silicon solar
cells is 25.6%.
27http://news.panasonic.com/global/press/data/2014/04/en140410-4/en140410-4.html
M. A. Green et al., Prog. Photovolt: Res. Appl. 23, 1 (2015)

28. Making silicon wafers requires much energy.
SiO2
+2C
CO
Si+3HCl
H2
+HSiCl3
HSiCl3
H2
, Clcarbon
quartzite metallurgical
silicon powder
H2
HCl
arc furnace chemical reactor distillation
HSiCl3
chemical vapour
deposition
polysiliconCzochralski processfloat zone
process
silicon
ingot
sawing
silicon wafers
Siemens process
Figure: A. Smets, K. Jäger, et al.,“Solar Energy”(UIT Cambridge, 2016) 28

29. During sawing, about 50% of the material is lost.
SiO2
+2C
CO
Si+3HCl
H2
+HSiCl3
HSiCl3
H2
, Clcarbon
quartzite metallurgical
silicon powder
H2
HCl
arc furnace chemical reactor distillation
HSiCl3
chemical vapour
deposition
polysiliconCzochralski processfloat zone
process
silicon
ingot
sawing
silicon wafers
Siemens process
29Figure: A. Smets, K. Jäger, et al.,“Solar Energy”(UIT Cambridge, 2016)

30. Here in Berlin, we develop a technology with
much less material and energy consumption.
30
interlayer
High-quality crystallised silicon
glass
energy source
low-quality nanocrystalline silicon
J. Dore et al., IEEE Journal of Photovoltaics 4, 33 (2014)

31. Here in Berlin, we develop a technology with
much less material and energy consumption.
31J. Dore et al., IEEE Journal of Photovoltaics 4, 33 (2014)

32. The achieved material quality is similar to wafer-
based multicrystalline silicon.
32J. Dore et al., IEEE Journal of Photovoltaics 4, 33 (2014)

33. The current record of our thin-film cells is a power
conversion efficiency of 12.1%.
33
Voc 649 mV
Jsc 27.3 mA/cm2
FF 68.4 %
η 12.1 %
c-Si thickness ~10 µm
T. Frijnts et al., Sol. Energy Mater. Sol. Cells 143, 457 (2015)
O. Gabriel et al., Prog. Photovolt: Res. Appl (2015)

34. The solar spectrum up to the silicon bandgap
contains 44 mA/cm2. Hence, only 62% of the
available light are utilised in the thin cells.
34
Voc 649 mV
Jsc 27.3 mA/cm2
FF 68.4 %
η 12.1 %
c-Si thickness ~10 µm
T. Frijnts et al., Sol. Energy Mater. Sol. Cells 143, 457 (2015)
O. Gabriel et al., Prog. Photovolt: Res. Appl (2015)

35. Light management has to be used to increase
absorption via manipulating the light path.
35Preidel et al., J. Appl. Phys. 117, 225306 (2015).

36. Many other solar cell materials and concepts
were tested in the last decades.
36Figure: en.wikipedia.org, Sarah Kurtz and Keith Emery, NREL, 9 March 2016 (Public Domain)

37. Perovskite-based solar cells developed remarkably
in recent years.
37Figure: en.wikipedia.org, Sarah Kurtz and Keith Emery, NREL, 9 March 2016 (Public Domain)
22.1%
Perovskite cells

38. Perovskites are interesting hybrid materials
consisting of organic and inorganic components.
38M.A. Green et al., Nature Photonics 8, 506 (2014)
Figure: A. Smets, K. Jäger, et al.,“Solar Energy”(UIT Cambridge, 2016)
front glass
FTO
Au or Ag
perovskite
(b)
HTM
compact TiO2
(a)
A B X
Cations:
A: e.g. CH3NH3+
B: usually Pb
Anion:
X: mostly I

39. Perovskites are interesting hybrid materials
consisting of organic and inorganic components.
39M.A. Green et al., Nature Photonics 8, 506 (2014)
Figure: A. Smets, K. Jäger, et al.,“Solar Energy”(UIT Cambridge, 2016)
front glass
FTO
Au or Ag
perovskite
(b)
HTM
compact TiO2
(a)
A B X
But, perovskite cells
currently only
survive a short time.

40. What are the major challenges?

41. In 2013, only 18% of the energy was consumed
as electricity.
Data for 2013, IEA 2015 Key World Energy Statistics 41

42. Especially, transport is heavily dependent oil.
Data for 2013, IEA 2015 Key World Energy Statistics 42

43. Especially, transport is heavily dependent oil.
Data for 2013, IEA 2015 Key World Energy Statistics 43
How can we make
the other sectors
renewable?

44. Transport can be made more sustainable by
electric driving.
Picture: teslamotors.com 44

45. Pictures: Left: K. Jäger; Right: Sandia National Laboratory, US Government (Public Domain)
Solar heat can be used directly or to drive
an electric power plant.
solar collectors for warm water
concentrated solar power for electricity
45

46. Solar and wind electricity
production is very variable, the
sun is not shining during the night!
46

47. Combining wind and solar energy can decrease
the required amount of storage significantly.
T. W. Tröndle, PhD thesis (Universität Heidelberg, 2014)
0
5
10
15
20
100/0 90/10 80/20 70/30 60/40 50/50 40/60 30/70 20/80 10/90 0/100
Storagecapacityin%ofannualenergydemand
Installed power ratio of wind and PV in %
Mean
80% security
90% security
95% security
99% security
99.9% security
99.99% security EUROPE
47

48. 0 20 40 60 80 100
Excess capacity in %
100W / 0S
90W / 10S
80W / 20S
70W / 30S
60W / 40S
50W / 50S
40W / 60S
30W / 70S
20W / 80S
10W / 90S
0W / 100SInstalledpowerratioofwindandPVin%
0
2
4
6
8
10
12
14
16
18
Storagecapacityin%
ofannualelectricitydemand
With 60% excess capacity the amount of required
storage capacity reduces to 0.19% or 16.6 h.
T. W. Tröndle, PhD thesis (Universität Heidelberg, 2014)
EUROPE
48

49. Conclusions
•The potential of solar energy is immense.
•Installed capacities have been growing with about
43% each year.
•The localized cost of solar electricity in Germany is 10
ct/kWh.
•Almost all solar cells are made from silicon wafers.
•Perovskites are an interesting upcoming material.
49

50. New book on solar
energy
Written by 5 authors from
Delft University of
Technology
Available for free online
as Apple iBook and for
Amazon Kindle.
Paperback version
available online.
50

51. Figure: Ron Tandberg 51

52. Contact: k.jaeger@erlenrain.at
52