Full-scale field evaluation of a net zero energy greenhouse concept integrating electrified heating, envelope improvements, and on-site photovoltaics

To address climate change and the transition to a low-carbon society, greenhouse horticulture must improve energy performance, as greenhouse facilities are energy-intensive systems requiring environmental control for crop cultivation. In particular, winter heating relies heavily on fossil-fuel-based systems, making improvements in efficiency and fuel switching critical challenges for greenhouse decarbonisation. This study presents the first full-scale parallel experimental comparison between a conventional greenhouse and a greenhouse designed according to the Net Zero Energy Greenhouse (ZEG) concept in Japan, operated under identical structural and climatic conditions. Here, ZEG refers to a greenhouse design that reduces primary energy consumption through electrification, improved efficiency, and renewable energy integration, drawing on the evaluation framework used for zero energy buildings (ZEB). The study evaluates a ZEG-type greenhouse equipped with a groundwater-source heat pump, double-layer thermal curtains, and an on-site photovoltaic system. Measurements were conducted during the heating season and compared with a conventional greenhouse under commercial strawberry cultivation conditions. Results show that integrating groundwater-source heat pumps and enhanced thermal insulation reduced primary energy consumption for heating by 58% and CO 2 emissions by 68% relative to the reference greenhouse, while maintaining comparable cultivation conditions. In addition, on-site photovoltaic generation supplied renewable electricity equivalent to 25% of the heating-related primary energy demand of the ZEG-type greenhouse. Furthermore, heating energy costs were reduced by 76%. These results provide field-based evidence supporting the use of integrated electrified heating, improved envelope performance, and on-site renewable generation as practical strategies for reducing energy use and CO 2 emissions in greenhouse systems.