Test procedure

With exception of the thermal performance, the solar domestic hot water systems and the solar combisystems were tested according to the same procedures.

3.1 Thermal performance

The solar domestic hot water systems were tested on the basis of EN 12976-2 “Thermal solar systems and components — factory made systems — test methods” according to the DST method (Dynamic System Testing). In addition a separate collector test was carried out and the most important parameters of the store were determined from enhanced DST — measurements with sensors in the collector loop in order to enable a component based system simulation with TRNSYS.

The solar combisystems were tested on the basis of EN 12977-2 “Thermal solar systems and components — custom built systems — test methods” according to the CTSS method
(Component Testing — System Simulation). The parameters of the most important components (collector, store, controller) determined in this way and the hydraulic configuration of the individual systems were transferred into the simulation program TRNSYS.

For the determination of the “usable hot water volume” an additional test sequence on the store was performed according to the “DFS hot water comfort test” /3/.

The energy yield of the thermal solar systems was determined by means of system simulations for the boundary conditions described in chapter 2 on the basis of the system or component parameters, respectively, that were determined during the test.

For the calculation of the fractional energy savings, the energy saved by the thermal solar system was compared with the energy demand of a conventional (none solar) system. The system efficiency is determined by relating the energy saving of the solar thermal system to the available solar radiation. Hence the system efficiency is an indicator how effective the solar energy is used.

For the assessment of the thermal performance, the fractional energy savings, the system efficiency, the usable hot water volume, and for combisystems additionally the space heating buffer volume, are taken into consideration. The assessment concept was intentionally designed in a way that the typical design parameters such as collector area, store volume, usable hot water volume and, if existing, the space heating buffer volume did not affect the results as long as they are varied within sensible limits. Due to this approach the thermal performance of the system is primarily affected by the performance of the different components and their interaction within the complete system.