Abstract
The likelihood of system failure of small systems is investigated in order to establish the risk associated for the investment into a photovoltaic (PV) system for small domestic applications. This is achieved by reviewing existing literature on PV system failure rates and using these as an input for a statistical PV system yield simulation tool that considers failure and repair. It is typically assumed that these systems do not require any maintenance, but it is shown that this will have near catastrophic impact on the energy production of PV systems. The no maintenance is not a likely scenario, as small systems have to register their generation to achieve a feed-in-tariff. In a later stage, when PV is used for self-consumption only, this may change but in the present market most users are forced to carry out a quarterly check and thus this catastrophic failure is avoided by the need of having to apply for the feed-in-tariff. Minimum maintenance strategies for ensuring profitable system operation are investigated and their cost-effectiveness is discussed. It is shown that the present situation where many systems are neither monitored nor is any maintenance carried out results in a high probability of unsuccessful system operation as failure detection may take a very long time. Successful system operation here is defined as not recovering the financial investment. It would be advisable to carry out at least monthly performance checks as otherwise it is likely to have more than 10% energy lost because of system downtime. This requires, however, availability of irradiance data as otherwise it is not possible to identify whether low yields are due to resource issues or really system yield issues.
Highlights
Photovoltaic (PV) have been growing over the last years in the UK, as well as in other markets
In the context of the common UK operation, where systems are observed only in quarterly intervals, there are very significant risks (>80%) to not have a profitable system operating based on the underlying reliability data
Profitable here is defined as losing more than 5% of the energy that would be produced if there were no reliability issues
Summary
Photovoltaic (PV) have been growing over the last years in the UK, as well as in other markets. This significant increase in installation numbers has resulted in a number of systems not quite achieving predicted performance values as can be seen, for example, in the tail of performance ratios discussed in presentation of [1] This is due to issues in system design including meteorological datasets, installation quality and reliability. The root cause for this is the rapid growth of installations having added a lot of pressure on installers to increase staffing and capacity This rapid increase has resulted in many systems sold by less than ideally qualified staff, as evidenced by the obvious design flaws (as discussed in terms of shaded systems, e.g. in [2]). Profitable operation is defined here as not having a performance loss higher than 5% compared with the predicted output, which is the order of financial return people would expect for their system
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