Performance investigation on soil disinfection with a compound parabolic concentrating solar collector system

Abstract

Soil disinfection is a necessary step in solar greenhouses because of the soil borne diseases and pests caused by the continuous cultivation. However, the traditional physical soil disinfection methods lead to high energy consumption and high carbon emissions, chemical soil disinfection methods cause great soil pollution. Therefore, this study proposed a novel soil disinfection system that can avoid soil pollution and achieve solar-powered physical disinfection of planting soil. The proposed system collects solar energy with the trough compound parabolic concentrating solar collector system. The collected solar heat is continuously delivered by airflow to the heat exchange pipes buried in the soil. As a result, the soil temperature can be raised to the required level for a certain period to suppress the growth of weeds and kill pests and pathogenic bacteria. In this study, the variation trend of soil temperature in the actual greenhouse was measured in the field and compared with the calculation results. After 5 consecutive sunny days of continuous operation of the solar collector system, the maximum soil temperature on the surface, at the depth of 0.15 m and 0.3 m were 59 °C, 48.6 °C, and 43.4 °C, respectively. The duration of soil at a certain temperature can also reflect the disinfection effect, and the longest cumulative hours with the soil temperature at a depth of 0.15 m above 37 °C was 107.27 h. At the same time, the average microbial biomass carbon and the microbial biomass nitrogen decreased by 11.04 % and 8.56 %, respectively. Furthermore, the payback period of the system is 1.97 years and the greenhouse gas emissions can be reduced by about 410.82 kg CO2, 1.33 kg SO2, and 1.16 kg NOx every year. The research results indicate that this novel method of soil disinfection is feasible, which can improve soil temperature and achieve the purpose of soil disinfection. This study can provide a reference for green and low-carbon soil disinfection in solar greenhouses.