Civil Engineering Reference
In-Depth Information
family, polycrystalline and amorphous, but also not forgetting the semicon-
ductor PVs that are manufactured from compound materials and the new
and promising third generation developments. This section gives an over-
view of how and why the technology moved from the fi rst to the second
generation, and how it is hoped that the best of both can be used to provide
a third generation that might solve all previously acknowledged issues.
Figure 12.4 outlines the effi ciency levels of some of the fi rst, second and
third generation PVs, recorded in 2010 (Saari, 2010).
The following sections summarize where the technologies are now but
also question how they got to this point and the historical steps that were
taken to arrive at today's technology, before providing a glimpse of where
it could go in the future.
12.4.1 First generation
The fi rst generation had one simple task, with no limitations, which was split
into two steps:
1. Absorb light energy so positive and negative charges can be
generated.
2.
Create a potential difference by separating the positive and negative
charges.
This generation of solar cells is commonly known to have, on the positive
side, high effi ciency, but on the fl ip side it also has a higher cost, to be
expected with any new technology. It is estimated that the maximum theo-
retical effi ciency that these single junction silicon cells could hope to reach
is approximately 33%, limited only by thermodynamics (Shockley and
Queisser, 1961). To date, fi rst generation PVs account for the largest market
25
19
Efficiency (%)
16
12
11
5
Crystalline
silicon
Thin film -
CIGS
Thin film -
CdTe
Thin film -
aSi
Dye
sensitized
Organic PV
12.4
Energy levels achieved by PVs in 2010 (Saari, 2010).
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