Measurement investigation on the feasibility of shallow geothermal energy for heating and cooling applied in agricultural greenhouses of Shouguang City: Ground temperature profiles and geothermal potential

The use of electrical energy for heating and cooling systems to control the temperature in greenhouses will lead to high production and product costs. To solve this problem, shallow geothermal energy as a local source of energy could be applied. In this study, a measurement model, the distribution profiles of temperature, and a preliminary assessment of the geothermal potential in the shallow zone at depths of 0.1 m to 3.6 m in Shouguang City, Shandong Province, eastern China were presented. The measurement results showed that the annual average temperature at depths of 0.1–3.6 m ranged from 13.1 °C to 17.6 °C. Preliminary assessment results of the geothermal potential showed that the daily average temperature difference between the air and at depths of 1.5–3.6 m was mainly from 10 °C to 25 °C during the winter months and between −15 °C and −5 °C during the summer months. Therefore, the heating systems could operate during January, February, November, and December. In May, June, and July, the cooling systems could be applied. Moreover, the measurement model gave good stability results, and it could be used in combination with the monitoring of the groundwater table, a survey of the thermal conductivity of the soil, climate change studies, which helps reduce unnecessary time and costs.