Solar air heating system

Abstract

The world is hurtling toward two major crises: Serious energy shortages and the acceleration of climate change. The years have witnessed the development of several types of solar air heating systems (SAHS). This chapter aims to present a review of the literature involving improvement methods, design configurations, test methods of thermal performance, and applications of SAHS. Firstly, this chapter makes an introduction to five new SAHS, namely, fin type flat-plate solar air collector (FTSAC), baffle-type vacuum tube solar air collector (VTSAC), novel straight through VTSAC, inserted VTSAC, and traditional straight through VTSAC. Meanwhile, the chapter states the advantages of these five types of SAHS and describes its working principles. The similarities and differences between the designed air collector and other air collectors are presented. In terms of structure and cost, the advantages of the new SAHS designed in this chapter are pointed out, which will provide the direction for the optimization and improvement in the future. Secondly, design and test methods of thermal performance of SAHS system are introduced in this chapter. The design parameters cover the determination of heat load and collector area of SAHS, air flow rate of SAHS, the resistance of SAHS, and the power of the fan. Besides, a test method of thermal performance for SAHS is also presented, which mainly includes its testing procedures, test conditions, test period (steady-state), as well as computation of collector efficiency. Finally, SAHS are widely used for many applications such as drying applications and space heating and cooling of buildings. This chapter reviews selected studies concerning these applications and presents a solar dryer and solar assisted heat pump dryer system (SAHPDS). According to the work conducted to date on solar drying and SAHPDS of fruits and vegetables, it can be concluded that the solar dryers can be adopted to a great extent. The solar drying of agricultural products serves as one of the most important potential applications of solar energy. It has been established that solar drying and SAHPDS of fruits and vegetables is technically feasible and economically viable. Heating and cooling of agricultural greenhouses are the paramount activities to extend its application throughout the year for crop production. In the meantime, SAHS are very popular for space heating applications relying on their simple design and cost. Major disadvantages of SAHS are relatively low thermal efficiency as well as little thermal storage capacity of the system itself.