Since the energy label in Portugal is based on an evaluation of primary energy, equipments for ambient heating, ambient cooling and production of domestic hot water have, besides the envelope and the climate, a critical influence in the result. In order to analyse the influence of the equipments, several scenarios were considered, as listed in Table 4.
Table 2 : Main characteristics of case-studies (as in the base-cases)
At present (summer 2008) approximately 430 different types of solar collectors and nearly 40 factory made systems are Solar Keymark certified. It is expected that two third of all solar thermal collectors sold in Europe are already qualified with a Solar Keymark /6/. A large number of the tests required for awarding the Solar Keymark were carried out at the Test and Research Centre for Solar Thermal Systems (TZS) located at the Institute for Thermodynamics and Thermal Engineering (ITW), University of Stuttgart.
6.1 Future development of Solar Keymark Certification Solar collectors
An assessment of the thermal performance of solar collectors directly on the basis of the efficiency parameters is not appropriate...Read More
The concentrator optics of the LFC consists of the mirror field of elastically bent primary mirrors having a focal length – depending on the actual collector – of several meter, and a secondary concentrator. Figure 4 shows schematically the configuration of a single tube collector. The primary mirrors may have different focal lengths and therefore different curvature radii. Radiometric flux density measurements at the aperture of the secondary concentrator may reveal the optical efficiency of the mirror field for a certain sun position. An alternative method we used for characterizing the incident flux is the photometric evaluation of the focal line on a calibrated white target at the receiver aperture...Read More
A. C. de Keizer, K. Vajen and U. Jordan
Kassel University, Institute of Thermal Engineering, 34125 Kassel, Germany, www. solar. uni-kassel. de
Corresponding Author, solar@uni-kassel. de
Continuous monitoring and failure detection during the life time of a solar thermal system is important to detect occurring failures as quick as possible. Therefore, several methods have been developed during the last decades. However, so far application is mainly limited to research and demonstration projects. In this paper several failure detection methods are described and compared with a partial multi-criteria analysis.
Up to now monitoring approaches have primarily been applied with data analysis by an expert, but without an automatic analysis of the data through the method...Read More
The components and measurement devices of an air-collector testing loop are more voluminous than for water-collectors. This simple fact causes additional difficulties when a solar collector testing loop is installed in a indoor laboratory and also for the conditions of outdoor measurements. In order to achieve the desired flexibility for testing indoor, outdoor and on systems installed in the field we followed the concept to install each component of the testing loop on its own carriage with wheels.
Figure 4: Some of the components of the solar air collector testing loop: one of two gas turbine volume flow meters, one of two ventilators, electric control cabinet and data acquisition, water-to-air heat exchanger...
There are obvious advantages that the instrument based on PXI technology possesses a high speed, a small size and easy expansion, so the hardware structure will use PXI bus technology and relevant products based on the PXI bus. The system concludes PXI-1042 chassis, PXI-8186 Controller, PXI – 6221 multifunction data acquisition card, PXI-4351 high-precision temperature and voltage logger, PXI-6513 digital I/O card, and SC-2345 signal conditioning modules.
Fig. 3 shows the physical structure. PXI-1042 as chassis has 8 slots to comply with PXI and CompactPCI specifications with universal AC power supply. PXI-8186 as embedded controller can greatly improve the system scalability and integration...Read More
H. Kerskes*, B. Mette, H. Drtick, H. Mtiller-Steinhagen
Institute for Thermodynamics and Thermal Engineering (ITW),
University of Stuttgart, Pfaffenwaldring 6, 70550 Stuttgart, Germany
Corresponding Author: kerskes@itw. uni-stuttgart. de
System tests according to the EN 12976 test procedures are a basis for factory made Solar Keymark system certification. To obtain the Solar Keymark certificate, each system configuration of a solar domestic hot water system (DHW) has to be tested by an accredited testing laboratory. As companies often offer a product line of their solar DHW systems, it is desirable to have a calculation tool that is able to predict the thermal performance of the whole product line without the need to test each of the system configurations...Read More
The collector was tested according to both steady state test (EN 12975-2;section 6.1) and dynamic test (EN 12975-2; section 6.3) methods. The corresponding characteristic parameters are presented in Table 1.
Table 1. Efficiency curve parameters after steady-state test results
Incidence angle modifier (IAM) values obtained, after both test methodologies, for longitudinal and transversal incidences are presented in Table 2.
Table 2. Steady-state and dynamic test results for transversal and longitudinal incidence angle modifier values