Results — Performance Matrix
The result of the comparison of the failure detection methods against the criteria described in §2.4 is presented in table 4.1. The performance matrix shows the performance of the failure detection method based on the different criteria. A few things need to be clarified before interpreting the table. First of all, it is assumed that without automatic failure detection there is a possibility for checking data with a manual analysis. This can be effective but is costly (dependent on the level of the analysis). This could be (and is partially) applied for all methods. Therefore, the criterion is limited to automatic failure detection. Because a lot of information is qualitative, it is hard to determine how much a method will cost in future application when it is still in the R&D phase. Also the effectiveness of a method may increase based on practical experience. Furthermore, the (literature) publications in general do not provide a very accurate description of effectiveness and accuracy of the method.
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Table 4.1 Performance matrix
? = unclear |
1 IOC: only hardware
2 costs for measurement equipment, including one year monitoring
3 Costs per month for 20 year monitoring and at least 30 monitoring systems sold. The main costs are
expected for maintenance and improvement of software (between € 15 and 50 per month) [11].
4 var = variable, sl = solar loop, - aux = whole system besides auxiliary heating system, bs = buffer
discharging loop (optional for IOC)
The IOC is the first method which could result into the implementation of a monitoring and failure detection method into general use of larger solar thermal systems. It has been tested and is commercially available against a reasonable price, but it does not apply to the whole solar system. Manual monitoring, though more costly, is much easier adapted to extensive variation in hydraulics and systems. The method developed at Kassel University is still in development, but could also provide an automatic monitoring solution for large systems. It includes more sensors and a larger part of the system than the IOC approach, and can therefore also analyse individual components. For very small systems the approach followed in FUKS detects several failures at reasonable additional costs.
However, so far none of the above described approaches takes the auxiliary heating system into account, which is also an important source of errors.
