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Title:
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Levensduur van Solar Home Systemen : opzet en uitvoering van laboratoriumtests
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Author(s):
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Published by:
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Publication date:
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ECN
Energy in the Built Environment
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1-6-2002
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ECN report number:
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Document type:
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ECN-C--02-007
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ECN publication
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Number of pages:
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Full text:
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74
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Download PDF
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Abstract:
In this work the reliability and lifetime of small domestic stand-alonePV-systems is studied. Previous monitoring studies have already showed
that a large number of the installed solar home systems (SHS) and solar
lanterns is not functioning properly. It is also known that low-quality
products and incorrect sizing are important causes for this, yet little
data is available on the operating conditions and the long-term performance
of SHS. Especially the effect of the system configuration and operating
conditions on battery degradation, which is systematically studied here,
is not clear.
Data from field monitoring and previous test results have been used
to determine the principal factors that cause premature failure of lead-acid
batteries. In order to analyse these factors a laboratory test has been
performed in which 6 different SHS and 2 solar lanterns of the same
type were operated under simulated field conditions. In the SHS three
different automotive batteries and one type of deep-cycle battery were
applied, in combination with three types of charge regulators.
After the test all automotive batteries showed serious degradation,
in contrast with the deep-cycle batteries. One of the automotive batteries
broke down before the end of the test and two others broke down after
the final capacity measurement. In all the cases a defect cell caused
this.
The number of cycles corresponds approximately to a practical use of
9 months for the SHS and 6 months for the solar lanterns.
The battery that failed first was part of a SHS in which a relatively
small battery was directly connected to the simulated module without
the use of a charge regulator. During operation the charging efficiency
was very low and the battery showed excessive water loss.
The test results showed that in most cases a lower battery capacity
due to ageing did not directly lead to reduced energy output. The common
definition for the end-of-life, which is reached when the remaining
capacity is less than 80% of the nominal value, is therefore not a proper
estimate for the practical lifetime.
Often a large battery capacity is chosen to obtain a good utilisation
of the energy from the module and to prevent water loss and corrosion.
However the test results show that a SHS with a smaller battery capacity
combined with a constant voltage charge regulator is likely to perform
well, as large batteries tend to be undercharged.
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