Loading...
8 results
Search Results
Now showing 1 - 8 of 8
- Experimental thermal performance evaluation of different configurations of Copenhagen solar cookerPublication . Apaolaza-Pagoaga, Xabier; Carrillo Andres, Antonio; Ruivo, CelestinoIn this work, four different configurations of Copenhagen solar cookers were tested experimentally at the same time under the same weather conditions. First tests were carried out using pots without water load. Secondly, tests were performed with the equal amount of water in each pot. Thirdly, tests were carried out with different amounts of water for one of the configurations. From the results of the first set of tests, it was found that the performance of one of the configurations depends more significantly on the solar altitude angle than the others. A large number of experiments for each set of tests were conducted covering a wide range of solar altitude angles. A thermal performance analysis based on the ASAE S580.1 standard was performed with the measured data of the second and third sets of tests. The obtained plots with the observation points of each configuration evidence that the linear trend of the standardised power is not universal. The observed trends are very dependent on the solar altitude angle. Thus, the procedure for evaluating standardised power recommended by the standard for cooker performance comparison should be improved.
- On the use of experimental measured data to derive the linear regression usually adopted for determining the performance parameters of a solar cookerPublication . Ruivo, Celestino; Apaolaza-Pagoaga, Xabier; Di Nicola, Giovanni; Carrillo-Andrés, AntonioIn the present work, the results of testing panel and box solar cookers are used to investigate the suitability of using the linear regression for estimation of the performance parameters of a solar cooker. The panel cooker and the box cooker were experimentally tested with glycerine and peanut oil, respectively. An exponential fitting to the plot of measured load temperature versus time is used to derive the linear regression between the instantaneous efficiency and the specific difference of temperature. The linear regression curve is compared with the corresponding experimental curve. Minor deviations are observed in the case of the panel cooker, but only in the middle part of the test. In the case of the box cooker, the deviations are very significant during the whole test. The present work presents the simplified formu-lation associated with the physical problem. It points out the importance of performing further research to develop a more accurate procedure. The determination of parameters based on the linear regression cannot be seen as a universal procedure applicable to all types of cookers. The opto-thermal ratio and the maximum achievable load temperature are overestimated.
- Experimental characterization of the thermal performance of the Haines 2 solar cookerPublication . Apaolaza-Pagoaga, Xabier; Carrillo-Andrés, Antonio; Ruivo, CelestinoThis work presents the most exhaustive experimental characterization of the thermal performance of the Haines 2 solar cooker available to date. Two Haines 2 solar cookers were tested side-by-side in Malaga, Spain, 36.7 N, between May 2021 and December 2021. A novel test procedure using empty pots and a tilted plane with variable inclination gave useful information about the influence of the solar altitude angle on cooker performance, and allowed identification of the best range for each of the two available reflector configurations for this cooker. Some suggestions are given to improve the cooker design for low solar altitude angles. In addition, a large number of water heating tests partly based on the ASAE S580.1 standard protocol were conducted to i) determine the standardised power, ii) examine the influence of the solar altitude angle, and iii) investigate the impact of using partial loads. All these results provide a complete characterization of the performance of this cooker in a wide range of operating conditions of practical interest. It is recommended that future versions of ASAE S580.1 standard consider the influence of both solar altitude angle and partial loads.
- Proposal of a non-linear curve for reporting the performance of solar cookersPublication . Ruivo, Celestino; Apaolaza-Pagoaga, Xabier; Coccia, Gianluca; Carrillo-Andrés, AntonioPerformance parameters of solar cookers have conventionally been determined by assuming a linear trend between the cooker power and the difference between load temperature and ambient air temperature. This approach may not be convenient for some solar cooker designs. In the present work, the suitability of a non-linear regression derived from fitting the measured load temperature to a second order exponential polynomial was investigated and compared with the linear regression. Both regressions were compared with the corresponding experimental curves of a panel cooker and a box cooker. In the case of the panel cooker, the linear trend of the experimental plot was confirmed over a large period of the conducted test. Minor deviations from the experimental data were observed only at the beginning and at the end of the test. On the contrary, in the box solar cooker, significant deviations between the linear regression plot and the experimental points were observed, while smaller deviations were obtained using the non-linear regression. Thus, the proposed method can be seen as a promising approach that should be considered when updating the existing procedures for testing and reporting the performance of solar cookers.
- Experimental determination of the standardised power of a solar funnel cooker for low sun elevationsPublication . Ruivo, Celestino; Carrillo-Andres, Antonio; Apaolaza-Pagoaga, XabierOver the past few decades, many efficient solar cooker designs have evolved. It is important to measure their performance and communicate this information to researchers, manufacturers and users around the world. Funnel type solar cookers are simple, effective and have multiple advantages in practical use, but there is limited experimental data about them in the academic literature. This work provides performance data for a well-known design of funnel cooker. When possible, the experimental protocol was based on the ASAE S580.1 Standard. The following procedures were added to improve the quality and reliability of the measured data: i) two identical funnel cookers were tested simultaneously, side by side, to control for weather variables, ii) a large number of observations were made iii) confidence and prediction intervals were calculated for the main figures of merit iv) cooled water was used to extend the range of valid observations. Tests were conducted in Malaga, Spain, at latitude 36.9 degrees N, between November 2019, and February 2020, a period with low sun elevation. Azimuthal solar tracking was applied. Two different pot lids were compared to investigate their influence on the standardised cooker power obtained. (C) 2021 Elsevier Ltd. All rights reserved.
- New approach for analysing the effect of minor and major solar cooker design changes: influence of height trivet on the power of a funnel cookerPublication . Apaolaza-Pagoaga, Xabier; Carrillo-Andrés, Antonio; Ruivo, CelestinoIn present work, the power values of two funnel cookers were determined by following the standard ASAE S580.1 procedure and also a novel improved approach for better analysing the effect of minor design changes. This new approach is based on experimental side by side tests of the two cookers and it adopts a shorter time interval and a curve fitting based on the LOESS adjustment is adopted for the evaluation of the difference in power values of the different designs tested. The two funnel cookers were tested experimentally with a load ratio of 4 kg m-2. The influence of the height of a trivet, from 0 to 100 mm, on the cooker power was evaluated. The estimated changes in power values due to the design changes were low but not negligible. As example, the power standardised increases 6 W when a height trivet of 25 mm is used respecting cooking operation without trivet. The novel approach is promising because it enables to determine the impact of minor design changes on the power of the cooker. The same analysis is not possible to be performed with the standard ASAE S580.1 procedure due to the uncontrollability of the weather conditions.
- Influence of the aperture area on the performance of a solar funnel cooker operating at high sun elevations using glycerine as loadPublication . Ruivo, Celestino; Apaolaza-Pagoaga, Xabier; Carrillo-Andrés, Antonio; Coccia, GianlucaFive funnel solar cookers have been tested to investigate the influence of the aperture area on their performance. The largest cooker had an aperture area of 0.5 m(2) and it was tested side by side with two other two smaller cookers. Each cooker was tested with the same amount of glycerine. The linear performance curves relating the efficiency with the specific temperature difference was determined. Then, the determined regressions of the cooker opto-thermal ratio and the reference time on the aperture area were used to predict: i) the influence of the solar irradiance and the aperture area on the maximum temperature achieved by the load, ii) the time duration required for achieving load temperature from 65 to 140 degrees C, and iii) the power of the cooker. It was found that for a solar irradiance range of 600-1100 W m (2), the pasteurization temperature can be achieved even by the smallest cooker, and the efficiency of the largest cooker is close to the efficiency of a cooker with optimum aperture area. Moreover, when using the largest cooker, under an irradiance of 1100 W m (2) and ambient temperature 20 degrees C, the load can achieve 180 degrees C, implying that frying is possible.
- Experimental evaluation of the performance of new copenhagen solar cooker configurations as a function of solar altitude anglePublication . Apaolaza-Pagoaga, Xabier; Carrillo-Andrés, Antonio; Jiménez-Navarro, Juan-Pablo; Ruivo, CelestinoThe Copenhagen cooker is a panel-type solar cooker that uses four flexible reflective panels to redirect solar radiation to a cooking vessel. Its concept design allows adjustment of the four panels to create new geometries that can adapt to the solar altitude angle. Originally, three geometrical configurations were presented by its creators. In this work, building upon these originals, new configurations are proposed to improve performances. To quantify performance improvement, experimental tests are performed. First, stagnation tests are carried out to identify the best configuration for different solar altitude angles. Then, the most promising new configurations and the original ones are tested, side-by-side, heating a water load and for different ranges of altitude angle: low (35 degrees), medium (66 degrees) and high (75 degrees). Results show that performance significantly improves. Results across the entire solar altitude angle range help general users to set the most effective configuration based on their specific conditions. Last, our experimental study suggests that tests without load can be a good predictor of the behaviour of solar cookers with load. This qualitative conclusion would allow solar cookers to be tested in shorter periods for all ranges of solar altitude angle, which is of great value for general users.