Best combinations of energy-efficiency measures in greenhouses considering energy consumption, yield, and costs: Comparison between two cold climate cities

Greenhouse agriculture is enjoying a surge in popularity to increase food security and use resources efficiently. Less known is that greenhouses consume enormous amounts of energy for heating and lighting. Energy efficiency is paramount in greenhouse production, but choosing the best measures is challenging and depends on climate and energy tariffs. The novelty of this study is to investigate and compare multiple practices and their cumulative impacts in high-latitude greenhouses from energy, cost, and yield points of view. It focuses on simulating the energy consumption and yields in greenhouses under 31 energy-saving scenarios and in two different locations, Copenhagen (Denmark) and Montreal (Quebec, Canada). Various lighting and energy-saving techniques are explored, including high-pressure sodium (HPS) and light-emitting diode (LED) lighting, canopy interlighting, thermal screens, additional envelope insulation, and a heat harvesting system. Greenhouses in Copenhagen consume more energy due to artificial lighting to compensate for low solar radiation in winter. Energy costs are, on average, 77 % higher than in Montreal, partly due to high energy prices. The best scenario regarding energy operational cost per yield for Montreal is LED toplights with thermal screens and envelope insulation, and for Copenhagen it is LED toplights with thermal screens and a heat harvesting system. However, if growers wanted to implement only one measure, the results showed that LED toplights is the best measure to implement for both locations due to its high energy efficiency and minimal impact on yield. These results provide insight into the best energy efficiency measures tailored to specific locations. • Thermal screens allowed to reduce energy consumption by 17.7 % to 26.5 %. • LED interlights and HPS toplights increased yields by 15.3 to 27.5 %. • Energy cost per kg of yield is significantly lower in Montreal than Copenhagen. • Best strategy to reduce energy cost per kg is the use of LED lighting in both cities. • Best measures vary between cities due to climatic and energy tariff differences.