Report on Accelerated OPD Test TIGI collector Grand Summary

Transcription

1 Oberseestrasse 1, CH 864 Rapperswil TIGI LTD. 12 Modi'in St. IL Petah Tikva Report on Accelerated OPD Test TIGI collector Grand Summary Introduction To check the durability of the TIGI collector with the OPD device a sample collector was exposed in stagnation and retested for performance several times on the SPF roof and in the SPF solar simulator. In this time different aspects were investigated such as: - Is the OPD function affected after some time of operation? - Is there a problem with accumulation of humidity? - How does the thermal performance change with time? - Is there a problem with the visual appearance (outgassing, fogging, etc)? Brief Test History : Indoor Reference measurement, as received (X255/1) : Collector filled with Argon & Indoor Performance Test (X256/1) : No action : Outdoor Exposure fixed south/45 Elevation (X256/1) : Indoor Simulator Performance Retest (X268/1) : Refill Argon and Retest (X268/1) : Outdoor Exposure fixed south/45 Elevation (X268/1) incl. gaps: 1xOPD Cycles indoor (X274/1) : Indoor Simulator Performance Test (X274/2) : Tracked stagnation, approx. one year (X274/1) : Indoor Simulator Performance Retest after Recalibration (X335/2) The numbers in brackets are SPF internal Test codes. Page 1 of 15 pages

2 Oberseestrasse 1, CH 864 Rapperswil Figure 1 The collector during the initial performance measurement (Reference) on the SPF indoor test rig. On the following pages the individual test sequences and performance retests are described together with some results and interpretations. General remark on the analysis of the performance measurements The standard second order model given by the EN12975 or ISO986 is only partly applicable for the performance analysis of the TIGI collector. For the mathematical description and data analysis a modified switching model was therefore developed. In this model the data analysis for temperatures below the OPD kick-in is the standard model. For the temperature ranges where the overheating protection device is activated the modified model given below applies. All the performance measurements were analysed using this model. In this description it is assumed that in first order approximation the OPD heat losses are depending on the difference between the mean absorber temperature (T m ) and the ambient temperature (T amb ). The absorber temperature is assumed as average between Inlet (T in ) and Outlet (T out ) temperature. The formulas used for the analysis of the performance measurements are given in Annex A. Using this model to analyse the measured data, results in the standard set of parameters (η, a 1, a 2 ). Furthermore, two additional parameters A and B describing the heat losses when the OPD is active are determined. All the parameters are related to an assumed aperture area of 1.766m 2. The switching temperature T Switch is set to 1 C. For all graphs showing the performance also the average irradiance G (in W/m2) is indicated. Page 2 of 15 pages

3 Oberseestrasse 1, CH 864 Rapperswil : Indoor Reference measurement, as received (X255/1) The thermal performance was measured on the collector as received without any pre-treatment. This measurement is the reference measurement for all the following tests..9.8 X255/1.7.6 Efficiency Measured Data Switching Model Fit Standard Model Tm* Test results Eta.7838 G 18.2 a A a2.727 B Figure 2 Reference measurement. Collector measured as received. Page 3 of 15 pages

4 Oberseestrasse 1, CH 864 Rapperswil : Collector filled with Argon & Indoor Performance Test (X256/1) After the first initial measurement the collector was flushed/filled with Argon and sealed again. The performance test shows that Eta remains unchanged where at higher temperatures the performance increase compared to the previous measurement is evident. The OPD is not affected by the Argon filling..9.8 X256/1.7.6 Efficiency Measured Data.1 Switching Model Fit Standard Model.2.4 Tm* Test results Eta.7839 G 17.6 a A a B -.21 Figure 3 Collector filled with Argon : Outdoor Exposure fixed south/45 Elevation (X256/1) Figure 4 The collector was exposed in stagnation for about 1.5 months from In this period the collector was exposed to approximately the irradiance dose for the ling time exposure test as required by the then valid EN Page 4 of 15 pages

5 Oberseestrasse 1, CH 864 Rapperswil : Indoor Simulator Performance Retest (X268/1) After the first outdoor exposure sequence the collector was installed on the simulator again for checking the performance. The performance drop for higher temperatures is evident. The most obvious explanation would be the loss of Argon as Eta is still the same..9.8 X268/1 ("as is").7.6 Efficiency Measured Data Switching Model Fit Standard Model Tm* Test results Eta.784 G a A a B -.24 Figure 5 Collector performance after first outdoor stagnation exposure. Page 5 of 15 pages

6 Oberseestrasse 1, CH 864 Rapperswil : Refill Argon and Retest (X268/1) The collector was refilled with Argon to make sure that the drop in performance is not caused by any material deterioration inside the collector The result shows that by refilling with Argon the previous performance is reestablished. We assume that the first filling of Argon by SPF maybe was not sufficient..9.8 X268/1 (after Argon Refill).7.6 Efficiency Measured Data Switching Model Fit Standard Model Tm* Test results Eta.7861 G a A a B -.25 Figure 6 Collector performance after Argon refill Observations and remarks: At the time of the experiment it was important to proof that the OPD is working also under long and hard exposure conditions. For this reason the collector was then exposed again outdoors in stagnation. Page 6 of 15 pages

7 Oberseestrasse 1, CH 864 Rapperswil : Outdoor Exposure fixed south/45 Elevation (X268/1) incl. gaps: 1xOPD Cycles indoor (X274/1) The collector was further exposed outdoor in stagnation to stress the OPD under stagnation conditions. To simulate more real operating conditions the collector was then installed on the indoor test rig and connected to the hot fluid loop. The inlet temperature was alternated between approximately 7 C and 12 C with irradiation levels of about 1 W/m 2, to simulate real operating conditions that require the OPD protection. In this way more than 1 OPD cycles (kick-in and kick-out) were initiated. Figure 7: Temperature sensor attached to the inlet of the condensator Figure 8: Collector on the test rig during a scan of the irradiation Temperature C T in T ex T OPD 7:12: 8:24: 9:36: 1:48: 12:: 13:12: Figure 9: OPD cycles Page 7 of 15 pages

8 Oberseestrasse 1, CH 864 Rapperswil : Indoor Simulator Performance Re-Test (X274/2) After the 1 OPD cycles test the collector performance was measured under exactly the same conditions as the initial reference measurements again.9.8 X278/1 = X274/2.7.6 Efficiency Measured Data Switching Model Fit Standard Model Tm* Test results Eta.7825 G a A a B Figure 1: Collector performance retest after at exposure and 1 enforced OPD cycles Page 8 of 15 pages

9 Oberseestrasse 1, CH 864 Rapperswil : Tracked stagnation, approx. one year (X274/1) The collector was installed on a solar tracker without fluid loop and in stagnation. A temperature sensor was inserted into one of the connectors to monitor the absorber temperature. A second sensor was attached to the OPD. Figure 11: Colletcor installed on the solar tracker on the SPF test roof Figure 12: Top: Temperatuire sensor inserted into connector. Bottom: Temperature sensor attached to the OPD. Figure 13 and Figure 14 below show typical data for a sunny day and for a partly cloudy day. On the sunny day the OPD kicks in in eth morning and prevents from overheating during the whole day. On a partly cloudy day the OPD is controlling the collector temperature over the whole day by kicking-in several times per day. Figure 15and Figure 16 below show the analysis of the exposure with respect to the new ISO986 standard for climate class A and B respectively. The analysis shows that the collector has undergone a multiple of the required stagnation conditions. Page 9 of 15 pages

10 Oberseestrasse 1, CH 864 Rapperswil 12 1 YM T8 Absorber Irradiation W/m :: 8:: 1:: 12:: 14:: 16:: 18:: 2:: 22:: 2 Figure 13: Irradiation and temperatures on a sunny day. TheOPD kicks in only in the morning and remains active over the whole day YM T8 Absorber Irradiation W/m :: 8:: 1:: 12:: 14:: 16:: 18:: 2:: 22:: 2 Figure 14: Irradiation and temperatures on a partly cloudy. TheOPD kicks in several times on the same day to prevent from overheating. Page 1 of 15 pages

11 Oberseestrasse 1, CH 864 Rapperswil [ C] or [MJ/m2] Exposure Evaluation ISO986:213, Climate Class A "Very Sunny" Daily Irradiance [MJ/m2] Temperature [ C] Summed Irradiance [MJ/m2] [MJ/m2] [ C] Exposure Evaluation ISO986:213, Climate Class A "Very Sunny" Temperature [ C] Average Irradiance [W/m2] Hours [W/m2] or [h] 4 2 Figure 15: Analyzing the outdoor exposure under ISO986:213 Climate Class A Very Sunny, the collector has undergone 397 Days of outdoor exposure (Class A requirement: 3) MJ/m 2 total irradiance Energy (Class A requirement: 6 MJ/m 2 ) h of Exposure representing conditions >1 W/m 2 and T amb >2 C (Class A requirement: 3 h) Page 11 of 15 pages

12 Oberseestrasse 1, CH 864 Rapperswil [ C] or [MJ/m2] Exposure Evaluation ISO986:213, Climate Class B "Sunny" Daily Irradiance [MJ/m2] Temperature [ C] Summed Irradiance [MJ/m2] [MJ/m2] [ C] Exposure Evaluation ISO986:213, Climate Class B "Sunny" Temperature [ C] Average Irradiance [W/m2] Hours [W/m2] or [h] Figure 16: Analyzing the outdoor exposure under ISO986:213 Climate Class B Sunny, the collector has undergone 397 Days of outdoor exposure (Class B requirement: 3) MJ/m 2 total irradiance Energy (Class B requirement: 54 MJ/m 2 ) h of Exposure representing conditions >9 W/m 2 and Tamb>15 C (Class B requirement: 3 h) Page 12 of 15 pages

13 Oberseestrasse 1, CH 864 Rapperswil : Indoor Simulator Performance Retest (after Recalibration X335/2) After the one year exposure the collector was installed again on the indoor test rig to check again the performance of the collector..9.8 X335/2.7.6 Efficiency Measured Data Switching Model Fit Standard Model Tm* Test results Eta.774 G 1.7 a A a B -.21 Figure 17: Collector performance retest after the one year outdoor exposure in stagnation. Page 13 of 15 pages

14 Oberseestrasse 1, CH 864 Rapperswil Figure 18 Collector installed on the simulator for the final performance measurement. Summary After more than one year of testing including several periods of outdoor stagnation, forced OPD kick-ins and several performance tests, it is evident that - The OPD still works perfectly. - The Eta is about 1% reduced compared to the previous test. This reduction is close to the measuring uncertainty. However, even a 1% decrease would be a brilliant result for a collector after one year in stagnation. - The loss coefficient are similar to the previous measurement, hence the collector still must be filled with Argon. - Last but not least: The collector still looks good as at the beginning: No signs of outgassing and no signs of accumulation of humidity. Based on the experience with other collectors these are good indicators that the collector and the OPD will work as expected, also for a much more prolonged time of operation. Dr. A. Bohren Head of SPF Testing Institut für Solartechnik SPF Rapperswil, Page 14 of 15 pages

15 Oberseestrasse 1, CH 864 Rapperswil ANNEX A Formulas used for the analysis of the performance measurements Page 15 of 15 pages