Opensource Software for MLR-Modelling of Solar Collectors

A first research version is now in operation of a software package for multiple linear regression (MLR) modeling and analysis of solar collectors according to ideas originating all the way from Walletun et. al. (1986), Perers, (1987 and 1993). The tool has been implemented in the free and open source program R http://www.r-project.org/.

Applications of the software package includes: visual validation, resampling and conversion of data, collector performance testing analysis according to the European Standard EN 12975 (Fischer et al., 2004), statistical validation of results, and the determination of collector incidence angle modifiers without the need of a mathematical function (Perers, 1997).

The paper gives a demonstration with examples of the applications, based on measurements obtained at a test site at DTU in Denmark (Fan et al., 2009). The tested collector is a single glazed large area flat plate collector with selective absorber and teflon anti convection layer. The package is intended to enable fast and reliable validation of data, and provide a united implementation for MLR testing of solar collectors.

This will furthermore make it simple to replicate the calculations by a third party in order to validate the results. Finally more advanced methods can be implemented and easily shared as extensions to the package, for example methods for statistical estimation of the incidence angle modifier with non-linear functions for collectors with more complicated optics.

The overall advantage of this kind of tool and analysis is that it is almost the inverse of simulation. Therefore the model and parameters will be very well validated for application in later use for system simulation, even if the test is no real system test. Also for annual collector performance calculations with a new Excel tool connected to EN 12975 (Kovacs, 2011) this built in validation gives an extra quality assurance.