Journal: Applied Thermal Engineering
Author: Jeong-hwa Cho, In-bok Lee, Eun-seok Lee
Abstract
This study investigated a combined low-capacity heat pump and geothermal heat storage system for energy conservation
and enhanced thermal output in greenhouse heating during the cold season. The geothermal system comprised
a vertical double-pipe aluminum heat exchanger, selected for its high thermal conductivity, and a subsurface thermal storage unit comprising a concrete-encased rock bed. Air circulated through these structures facilitated heat exchange with the ground, enabling both heat storage and extraction based on temperature differentials. A low-capacity domestic air-to-water heat pump provided supplementary heating during winter, while the geothermal system operated independently during seasonal transitions for subtropical citrus cultiva- tion. Thermal performance was evaluated by monitoring air temperatures at strategic points along the airflow path under varying external weather conditions. This allowed for the assessment of individual component effi- ciency and analysis of energy utilization and losses within the system. Results indicated that the geothermal system preheated nighttime air by 2.4 ℃. Subsequently, the heat exchanger of the heat pump increased the air temperature by approximately 18 ℃, followed by an additional 1 ℃ increase from the bedrock. Notably, auxiliary heating from the heat pump was primarily required during the coldest winter periods, demonstrating the feasibility of using a small-capacity unit with substantial reductions in fuel consumption and emissions.
Keywords: Energy savings Heat storage Heat pump Geothermal Greenhouse Porous rock bed
Download Link: https://www.sciencedirect.com/science/article/pii/S1359431125015716