Citation: Jemai, N.; Soussi, M.; Chaibi, M.T. Opportunities for Implementing Closed Greenhouse Systems in Arid Climate Conditions. Horticulturae 2022, 8, 1102. https://doi.org/10.3390/ horticulturae8121102 Academic Editor: Xun Li Received: 14 October 2022 Accepted: 16 November 2022 Published: 24 November 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). horticulturae Review Opportunities for Implementing Closed Greenhouse Systems in Arid Climate Conditions Noura Jemai *, Meriem Soussi and Mohamed Thameur Chaibi Agronomic Sciences and Techniques Laboratory (LR16 INRAT 05), National Research Institute for Rural Engineering, Water and Forestry (INRGREF), University of Carthage, Ariana 2049, Tunisia * Correspondence: jemainoura92@gmail.com; Tel.: +216-24-716-463 Abstract: The closed greenhouse is an innovative crop system in the horticulture sector, integrating appropriate climate control equipment and optimized techniques to collect, store, and reuse solar energy for heating and/or cooling the greenhouse. This concept aims to improve the crop yield and quality with energy efficient and water-saving technologies. A specific focus on the opportunities of implementing closed greenhouses under arid climate conditions is detailed in this work. Guidelines for selecting appropriate techniques and design parameters are investigated, aiming for profitable and sustainable greenhouse production. This paper provides an overview of the design aspects of the closed greenhouse and a state of the art of its applications in arid areas. Firstly, the microclimate parameters, including temperature, relative humidity (RH), light intensity, and CO 2 concentration are introduced. Then, an in-depth focus on the effects of these parameters on crop productivity, water, and energy efficiency are thoroughly discussed. Finally, the limitations of closed greenhouse applications are pointed out as opportunities for further research and development in this emerging agriculture field. Keywords: closed greenhouse; arid regions; crop production; water recovery; energy saving 1. Introduction Ensuring food security for an increasing population is becoming an urgent global challenge. This important increase will negatively affect the supply and demand of limited foods, water, and energy resources [1]. To meet the growing demand by 2050, food resources must be increased by 60%, water by 55%, and energy by 80% [2,3]. Agricultural production is affected by global warming, which affects climatic conditions by causing floods, droughts, and storms in different countries [4]. Arid regions are more affected by these changes, since they are characterized by high temperatures and water scarcity [5–7]. These climatic conditions are harmful to plant growth and the long-term viability of genetic resources [8–10]. In fact, extreme temperatures, drought, floods, high winds, and sandstorms damage agricultural systems in arid regions, especially spontaneous vegetation and plants with superficial root systems [5]. Arid and semi-arid regions (Figure 1) cover over 30% of the total world surface and are home to about 20% of the global population [5,11]. In Africa, these regions account for 24% of the total population, in Asia for 23%, the Americas for 17%, Europe for 11%, and Australia for 6% [5]. The climate in desert regions is characterized by a lengthy and hot summer season during which ambient temperatures can approach 45 ◦ C with a very high daily variability, daily global solar radiation reaches 30 MJ m −2 , RH can dip below 10% at noon, and there is rare rainfall with high annual variability. During winter, these regions are characterized by a very high thermal amplitude with a strong variation in temperature between day and night. As a result, heating and cooling systems will be required. These systems are considered to be an important factor in reducing energy consumption [12,13]. For instance, in Tunisia Horticulturae 2022, 8, 1102. https://doi.org/10.3390/horticulturae8121102 https://www.mdpi.com/journal/horticulturae