The International Center for Biosaline Agriculture(ICBA) is an international, non-profit agricultural research center established in 1999 through the visionary leadership of the Islamic Development Bank (IsDB), the Organization of the Petroleum Exporting Countries (OPEC) Fund, the Arab Fund for Economic and Social Development (AFESD), and the Government of the United Arab Emirates (UAE). ICBA is a unique applied agricultural research center in the world that is focused on marginal areas where an estimated 1.7 billion people live. It identifies, tests and introduces resource-efficient, climate-smart crops and technologies that are best suited to different regions affected by salinity, water scarcity and drought. Through its work, ICBA helps to improve food security and livelihoods for some of the poorest rural communities around the world. ICBA is an equal opportunity employer and appoints qualified staff regardless of race, creed, color, age, gender, religion or national origin. We demonstrate our commitment to each member of our team through a competitive benefits package designed to assist our employees to cover their needs and the needs of their immediate family members.
Introduction
Looking for a consultant specialized in the modeling and optimization of fan and pad cooling systems for greenhouses using saltwater. The consultant will be responsible for developing a comprehensive model and optimizing the performance of a fan and pad cooling system in a greenhouse setting. The system incorporates the use of pozzolan bricks with different porosities and thicknesses for enhanced cooling efficiency.
Background
Growing crops in arid regions in greenhouses require active cooling to maintain the required temperature range for most crop production. The most widely used method for greenhouse cooling in these regions is evaporative cooling. Evaporative cooling is sometimes called nature’s way of cooling because crop transpiration is a natural form of this type of cooling. Pad and fan is the most popular type of evaporative cooling. This system cools and humidifies inlet air. The air is cooled at the location of the wet pad. Fans pull the cooled air through the greenhouse (negative pressure). The system relies on well-maintained fans and a well permeable pad not blocked by salt.
Cellulose pads are the current industry standard in evaporative cooling technology. These plasticized cardboard pads offer a very high surface area per unit volume and are easy to wet because of their natural wicking properties (Munters). The cooling efficiency of cellulose pads depends on the thickness of the pad and the air velocity through the pad. The pressure drop in the pad is also depends on the thickness of the pad and the velocity of the air (Munters). However, a disadvantage of cellulose pads is that they clog and loose efficiency over time, therefore they must be replaced every few years.
Evaporative cooling is estimated to contribute as much as 55 -90% of the total freshwater use of crops grown in greenhouses (Lefers et al., 2016). At ICBA greenhouse, the total freshwater footprint from cooling ranges from 43% in winter production period to 78% in summer production period (Hirich and Choukr-Allah, 2018). A possible alternative is to replace the fresh water used in evaporative cooling with either sea or brackish water. However, the use of a high salinity water source carries with it the risk of salt precipitation during the evaporative cooling process, leading to clogging of the evaporative media. The clogging of the evaporative media reduces the size of the porous media which leads to a shorter air/wetted media contact time, reducing the efficiency of the evaporative cooling and increasing the expected output temperature (Lefers et al., 2018). In addition, the clogging medium will in time require replacement, placing additional financial and time burden on the grower.
As a result of this clogging risk, most growers use fresh water to cool their greenhouses even though brackish water is readily available. Most of these growers produce their own fresh water using small-scale desalination plants to desalinate the brackish water, increasing their overall energy consumption and hence decreasing their competitiveness (Lefers et al., 2018).
Hence, in order to address concerns regarding the use of fresh water and the potential clogging of cellulose pads in evaporative cooling media, and to enable the utilization of brackish and/or sea water in greenhouse environments, a cost-effective and innovative cooling system was developed and tested (Al-Madhoun, 2016) (Figure 2). This novel system incorporates the use of porous pozzolan bricks, which are made from abundant pozzolan volcanic rock and are commonly utilized as an additive in Portland cement. These bricks offer numerous advantages, including superior resistance to salts, an extended lifespan compared to cellulose pads, and reduced maintenance requirements.
While the pozzolan cooling system has been previously tested and yielded satisfactory results, there is a need to further enhance the performance and efficiency of these systems by exploring variations in the porosity and thickness of the pad wall. The consultant will be responsible for developing a simulation model that accurately captures the behavior of such a system and optimizing its performance.
- Literature Review: Conduct an extensive review of existing literature, research, and best practices related to improved cooling efficiency of the fan and pad cooling systems in greenhouses.
- Model Development: Develop a comprehensive mathematical model that simulates the behavior of a fan and pad cooling system incorporating pozzolan bricks with different porosities and thicknesses. The model should accurately represent the heat and mass transfer processes, airflow dynamics, and overall system performance.
- Model Validation: Compare the model's predictions with real-world measurements conducted in the greenhouse and make necessary adjustments to improve accuracy.
- Optimization Strategies: Identify and propose optimization strategies to enhance the performance and energy efficiency of the fan and pad cooling system. Explore various scenarios, including operating parameters, and brick configurations, to determine the optimal setup for maximum cooling effectiveness.
- Reporting and Recommendations: Prepare a detailed report summarizing the findings, methodology, and recommendations based on the model development, validation, and optimization process. Clearly present the results, highlighting the benefits and limitations of the proposed strategies.
Deliverables
The consultant will be expected to provide the following deliverables:
- Literature review report summarizing the key findings and recommendations.
- Comprehensive mathematical model of the fan and pad cooling system incorporating pozzolan bricks, including all relevant equations and assumptions.
- Validation report showcasing the accuracy of the developed model through comparison with experimental data.
- Optimization report outlining the proposed strategies and their potential impact on system performance, energy efficiency, and crop productivity.
- Final report consolidating all the deliverables, summarizing the project's objectives, methodology, findings, and recommendations in a clear and concise manner.
a. Extensive knowledge and experience in greenhouse cooling systems, including fan and pad systems.
b. Proficiency in mathematical modeling and simulation techniques related to heat and mass transfer, fluid dynamics, and system optimization.
c. Familiarity with advanced materials used in greenhouse cooling, specifically pozzolan bricks, and their impact on cooling effectiveness.
d. Strong analytical and problem-solving skills, with the ability to interpret and analyze complex data sets.
e. Excellent communication and report writing skills to effectively convey technical concepts and recommendations to stakeholders.
Proposal Submission
Interested consultants should submit a detailed proposal outlining their approach, methodology, relevant experience, and a breakdown of costs associated with the project.
