Thermoelectric Condensate Production and a Feasibility Assessment of Its Reuse for Indoor Plant Irrigation

This study evaluated the feasibility of a small-scale system for recovering moisture from indoor air and reusing the recovered water for indoor plant irrigation. A condensate production system comprising a thermoelectric module, cooling plate, and heat sink was developed and integrated into a plant pot. By lowering the cooling surface temperature to the dew point or below, the system condensed and collected moisture from the surrounding air. During the plant cultivation experiment, 66 paired observations of dew point temperature and condensate production were obtained, with a mean condensate production of 35.38 ± 18.44 mL day−1. Physicochemical water-quality analysis was conducted to characterize the collected condensate. To assess its suitability for irrigation, a cultivation trial was conducted using Humata tyermannii, Hedera helix, and Hoya carnosa ‘Exotica Hort’. After Holm correction for multiple comparisons, most growth parameters did not differ significantly between the condensate and tap water treatments, whereas root fresh weight was significantly higher in the condensate treatment for H. tyermannii and H. helix. A supplemental energy test conducted in 2026 showed an overall specific energy consumption of 23.27 kWh L−1 under the tested conditions, indicating that energy efficiency remains an important limitation of the current experimental system. These findings support the feasibility of condensate reuse for indoor plant irrigation under the tested conditions and provide baseline data for the development of a proof-of-concept model for circular water use in small indoor green spaces. However, improvements in energy efficiency and further long-term water-quality evaluation are required for practical application.