The developed application should be able to identify the causes of an error and to offer appropriate assistance to the operator to solve the problem. The knowledge of error sources and causes has to be formalised and must be available for the operator. The definitive application should be user-friendly and easy to be operated by property developers.

2. The solar expert system

The choice of the method

The heuristic and the safe classification is indispensable for the solar expert system. Safe classification means that the characteristics of an error can be clearly identified and that its diagnosis can be considered as safe. A decision tree will be gone through for the safe classification. Its leaves can be either a diagnosis, an excluded diagnosis, a new question class or a leaf with no relevance for this sort of knowledge use.

Implementation

At first, all possible error sources in a solar installation are systematically entered. An error can "creep in" in different ways:

• A component is missing

• A component is wrongly inserted or attached

• A component is wrongly adjusted (operating errors)

• A component is defective

Despite our years of expertise, we are also surprised of the great number of possible error sources. These are represented in figure 1, but it does not include control errors (!) (adjusting errors, attachment errors, feeler errors etc..).