ANDATORY CERTIFICATION OF SOLAR THERMAL SYSTEMS IN BRAZIL

EFFECTS OF THE NEW TEST METHOD IN THE EFFICIENCY RATING OF COLLECTORS

Abstract

Certification of solar thermal systems will be mandatory in Brazil after July 2014. This implies new management efforts and technical products requirements. For solar collectors, it will be adopted a new efficiency test method and the efficiency index calculation procedure will change as well. This will bring significant changes in the way of expressing the efficiency and in the rating of the collector efficiency class. This classifies the collector from A to E according to efficiency and has particular relevance to the national solar thermal industry. This work discusses the regulatory transition and conducts an experimental study using IPT solar simulator to test three types of flat plate solar collectors according both to the new method (NBR 15747) and to the current method (ASHRAE-93). Results showed an average rise of 5.6 kWh/m².month in the efficiency index (PMEe) used to classify the collectors and an average rise of 4.4% in the collectors average efficiency, from the current to the new rule. As the efficiency class boundaries determined by Inmetro also increased, the collectors tested maintained their current classes, but the relative position within the classes changed. In the transition, the minimum efficiency index levels growth is greater for the lower classes than for the high classes (3.3 and 11.3 kWh/m².month for A and E classes, respectively), although PMEe determined experimentally showed similar growth regardless of the current efficiency level. This may impose more difficulties to less efficient products and can also cause improvements in the classification for current well classified products. Finally, the work highlighted the incidence angle modifier as a critical point for the final result. It was shown that although its effect was reduced in the mandatory program, this parameter still remains significant for the analysis.