Recent passive technologies of greenhouse systems: a review

There are 130 countries producing greenhouse vegetables commercially in 2016 over more than 1.1 million acres. Most of the greenhouses have high operating costs due to the great energy needs. The high heat loss due to the greenhouse envelope material is responsible for the high energy demand in greenhouses. Each area has a specific need which affects their energy requirements and conventional greenhouse technologies tend to have poor U-values. It means that heating energy is the dominant claim with up to 85% of the total greenhouse energy demand in cold climates countries. While in hot climate countries the energy for cooling is more prevalent. This paper presents the latest technological developments available for greenhouses in various countries used to control the microclimate in the greenhouse focusing on passive techniques. It was found that PCM has recently been used to provide heating and cooling in the Mediterranean climate. Moreover, closed greenhouse concept-based system for the northern climate improved the reduction energy demands by 80% with a potential payback of 6 years. Additionally, for most countries double-glazing envelopes frequently proved to be the most powerful to increase the greenhouse performance.