Inclusivity of thermal performance parameters for evaluation of solar cookers and the necessity of uniformity in the appraisal using generalized test procedure for different designs

Solar cookers play a vital role in decentralized energy solutions. Therefore, their appropriate rating is essential. The present work reviews and emphasizes the usefulness of thermal performance parameters (TPPs) for assessing solar cookers, such as box type, parabolic dish, panel type, Fresnel lens-based, and their hybrids. Although the TPPs are extensively used for testing solar cookers, several research studies depicted ambiguities, non-uniformities, and inconsistencies in their use. Interestingly, Cooker Opto-Thermal Ratio (COR) is one of the most generalized and, hence, useful TPP for the optical and thermal performance evaluation and rating/grading of multiple designs of solar cookers. In view of non-uniformities and inconsistencies found in determining TPPs, current work provides crucial insights into the existing TPPs, including COR, corresponding test standards/protocols, and quantification of test load(s) for solar cookers. Also, this work justifies the appropriate use of the different TPPs for solar cookers, and the usefulness and robustness of COR determined using linear regression fit of experimental data and derivate COR-dependent objective parameters. Finally, it includes insightful information for researchers, designers, and manufacturers on the future research pathways based on COR and corresponding test procedure and provide useful visions to avoid its deceptive, inconsistent, and inappropriate use.