A next-generation greenhouse design for increasing solar gain in high-latitude regions

• Novel greenhouse design with water tubes realised via a double-walled polymer film. • Solar-harvesting performance in north England examined via ray-tracing simulations. • East-west orientation is preferable to receive more sunlight in winter. • 64% More sunlight is captured in early winter mornings than conventional greenhouses. • Light distributed over a wide angular range – high solar gain when low sun elevation. Greenhouses create microclimates suitable for growing vegetables under less favourable outdoor climatic conditions. In high-latitude regions, greenhouses are used to extend the growing season in winter, when the temperature is low and daylight hours are short for vegetable growth. This work presents the optical design of a novel greenhouse that can increase the amount of sunlight available to plants. The design consists of a double-walled plastic film with tube-like pockets to form the greenhouse roof. Water flowing inside the plastic-film pockets refracts light, allowing sunlight to be captured more efficiently compared with conventional planar sheets when the solar elevation angle remains small (in winter). Ray-tracing simulations are conducted, and the solar-harvesting performance of the water-tube greenhouse design is evaluated in Cheshire, northwest England (latitude: 53.18° N). The simulation results suggest that the water-tube greenhouse is beneficial for extending the growing seasons in Cheshire. For example, the water-tube greenhouse can capture 67% more sunlight in the early morning in winter compared with a conventional polytunnel greenhouse.