Recent advances in net-zero energy greenhouses and adapted thermal energy storage systems

In agricultural greenhouses, employment of energy-saving strategies along with alternative energy sources has been identified as a potential solution to address the intensive energy consumption of these cultivation facilities. This study investigates the integration of renewable energy technologies, including solar thermal, solar photovoltaic (PV) and photovoltaic-thermal (PVT), geothermal, and biomass with greenhouse cultivation systems as net-Zero Energy Greenhouses (nZEGs). Solar energy is the most abundant renewable energy source that has been successfully used to provide thermal and electrical power requirements of greenhouses. The use of geothermal heat in greenhouses will save primary energy sources (more than 20%) and reduce operating costs. Utilizing solid biomass not only provides heating and cooling demands of greenhouses but also can supply their CO2 requirements. In terms of energy storage, the use of Sensible Thermal Energy Storage (STES) can cause a 3–5 °C increase in the inside air temperature while resulting in almost 28 kWh/m2 energy saving per area of the greenhouse. Phase Change Materials (PCMs) are extensively used in TES systems and provide high thermal efficiencies and reduce energy consumption (around 30–40%) with the main drawbacks of low thermal conductivity, associated environmental concerns, and high costs.