ABSTRACT

1. As the dependence on fossil fuels for energy source contributes to higher food production costs, ensuring food security for small farmers has become crucial. Current food production practices are deemed unsustainable with their excessive use of energy accompanied by increased emission of greenhouse gases with the attendant global warming effects. It is thus imperative to develop and integrate new technologies to reduce production costs with minimal environmental impact. On poultry farms energy demands are high especially during the first six weeks when the one-week-old chicken require supplementary heat to maintain their body temperatures. Brooders fuelled by electricity, gas or diesel usually provide this heat, which are energy intensive and not quite environmentally friendly. In this research study, a solar-based localized convective brooding unit is designed to heat a prototype poultry house in Beqaa, Lebanon while meeting thermal comfort criteria as stated by ASHRAE and ASABE. The localized convective unit required only 33% energy input when compared to conventional non-localized systems. When integrated to the solar system utilizing parabolic concentrators coupled with water storage, the unit covered 72% of the load by solar energy for eight pens with 100 birds living in each during a winter flock operation. When compared to the existing electric thermal lamps system, it saved 87% on energy costs for the same flock. Considering averaged performance for the remaining heating flocks, fall and spring, the system would pay back in around 5 years. 1Department of Mechanical Engineering, American University of Beirut 2Department of Nutrition and Food Sciences, American University of Beirut ABSTRACT OBJECTIVE The proposed system is constituted mainly of two circuits. The solar side circuit which is composed of a parabolic solar collector with a thermal storage tank, a shell-and-tube heat exchanger and a constant speed circulating pump. The parabolic solar collector concentrates solar radiation in order to heat the circulating antifreeze solution in an insulated pipe placed at the focal point of the collector, which is used in turn to exchange heat with the water inside a thermal storage tank. The second circuit is composed of the localized heating units with circulating pumps. To attain the required temperatures for the chicken, a localized convective heating unit will be placed in each pen that allows for heat exchanging between hot water coming from the storage tank and the air surrounding the chicken. The overall system formulations are described in the following sections. Solar Collectors For the water in the collector, the amount of the heat gained will be assessed using the theory of Hottel and Whillieras that is presented by Duffie and Beckman, Duffie and Beckman [6]. FRis the heat removal factor, Ulis the overall heat transfer loss coefficient, Ti is the temperature of water entering the collector and Ta is the ambient air temperature. Storage Tank The storage tank will be modeled as well mixed, that is all the water in the tak will be at the same temperature. So an energy balance where the heat exchanger is placed inside the tank will be given by: Vis the volume of the water tank, Ls is the removed heat load from the tank, Qu is the corrected effective useful gain for the heat exchanger effectiveness and Ts is the temperature of water inside the tank. The useful heat energy from the solar concentrator can now be defined as: Localized Convective Heating Units The heat exchanger placed inside each localized unit is a simple fan coil heat exchanger. Its heat transfer equation is given by: Conventional Heat Load Calculation To study the energy efficiency of localizing the heating units, the heat load for the conventional ceiling mounted unit will first be computed using the heat loss equation: However, the heat generated by the chicken must be subtracted from the obtained load to account for a positive load on the space. RESULTS AND DISCUSSION CONCLUSION This paper presents a solar heating system for a poultry farm at AUB’s AREC. The study helps in investigating the energy reduction in providing the heating requirements for chicken broilers when utilizing a solar-based localized heating system, and its accompanied reduction in the production costs. The system was simulated and evaluated in the different stages of the brooding period, and in different climatic conditions. The simulation results revealed a 67% reduction in the heating load when the heating units were localized rather than mounted on the ceiling of the pen. On the other hand, upon integrating the localized convective unit to a solar concentrator system coupled with storage, it was found that the design saved 87% on energy consumption for a 6-week winter flock when compared to existing heating system based on thermal lamps. REFERENCES [1] Okonkwo, W., & Akubuo, C. (2007). Trombe Wall System for Poultry Brooding. 6 (2). [2] Flood, C., Brewer, R., Koon, J., & Dunn, J. (1981). Solar Heating of Poultry Houses: 2. An Analysis of Solar Heating Systems. Poultry Science , 60, 1381-1385. [3] Purswell, J. L., & Lott, B. D. (2007). Heating Poultry Houses with an Attic Ventilation . American Society of Agricultural and Biological Engineers. [4] Darwish, A. H. (2003). Analysis and Assessment of the Poultry Sector in Lebanon. Ministry of Agriculture/Food and Agriculture. [5] Ghaddar, N. (1999). Weather Data Summary For The Year 1998. American University of Beirut. [6] Duffie, J. A., & Beckman, W. A. (1982). Solar Engineering of Thermal Processes. John Wiley & Sons. ACKNOWLEDGEMENT This research project is funded by the Munib and Angela Masri Institute of Energy and Natural Resources. Table 1. Weekly Profile of Load Covered by Solar Energy The proposed research will consider lowering the energy consumption and operational costs for supplying the heating requirements for chicken in a poultry house in rural Lebanon by integrating a solar-based localized heating system. Energy Performance and Economic Analysis By performing the energy performance analysis of the proposed system and the existing one, it was found that the current system costs 575$ per a complete brooding cycle, however, the proposed system costs only 75$ per cycle. This accounts for a 87% of energy savings in the solar-based localized heating system as compared to the use of electrical lamps. On the other hand, a payback period analysis was established in order to study the cost-effectiveness of the system, and it was shown to be 5.3 years. This is considered a good range as the lifetime of this system is around 20 years so we will have around 15 years of net savings. Moreover, this only includes a decentralized system that serves only 8 out of the 44 pens. Solar Energy Operated Brooder to Improve Food Security of Small-holder Poultry Farmers in Rural Lebanon NUMERICAL SUMILATION In order to perform the comparison between the localized convective heating system with a ceiling mounted one, numerical simulations using Airpak, a computational fluid dynamics (CFD) software, are executed. Furthermore, the heating load required for the brooding cycle is assessed for a 4-pen module. The 4-pen arrangement covers all possible cases for the pen: pen with two external walls, pen with one external wall and interior pen. As the chicken have weekly changing environmental conditions/requirements, the model calculations are simplified to calculating solutions for one typical day for every week and 6 representative temperatures per day are taken as the average temperature for every 4 hours. This would sum into a total of 36 cases to solve for. To model the whole system, a MATLAB code simulated the solar concentrator's performance, the thermal storage tanks' profile and the heating coil conditions. However, based on conventional heating load calculation method for non-localized heating, the energy required to heat the pen is equivalent to 1252W. So a preliminary conclusion can be drawn here that localizing the heating saved 67% of the load. In other words, the system utilized only 33% when compared to conventional systems. In order to verify this result for the rest of 35 runs based on the 6 week-representing days with 6 temperatures per day, we used the value of 33% as a first energy input trial for the convective unit. Figure 1 and 2 show the flow and temperature contours results of the performed simulation. CASE STUDY This research considers a poultry house that exists at the Agricultural Research and Education Center (AREC) at the American University of Beirut in the Beqaa Valley, East Lebanon. The house includes 44 pens, each of 8.9 m2 area and hosts 100 chicken. Presently, electrical lamps provide the temperatures required for the chicken brooding. A diesel boiler is also used in fall and winter periods to aid the lamps in heating during the first two weeks of brooding. For the poultry house in AREC, four flocks are carried out each year. The birds are placed for 42 days under the brooder before they become fully developed and ready to be delivered to the market. The winter flock will be considered in study as it requires highest heating loads. RESULTS AND DISCUSSION Localized Heating Units To attain the objective of examining the energy efficiency of the localized heating units, the heating load of the simulated module for the localized unit case is compared to the load required for the conventional system using equations 5 and 6. For an outdoor ambient temperature of 3.1℃ in the first week of brooding, the energy required by the localized unit for 1 pen is found to be 412W. Fig 1. Temperature Contours at Horizontal Cut for 4-Pen Module Fig 2. Velocity Contours at Vertical Cut for 4-Pen Module (Facing External Wall) Full Simulation Running the MATLAB code that simulated the whole system allows for probing the efficiency of utilizing solar energy in the heating system. Noting that the study is performed on 16 pens out of 44, each solar system covers half of the selected pens, that is 8 pens. The results for the six weeks that make up the full brooding flock in terms of solar load coverage were gathered and analyzed. It was found that the solar energy covered 72% of the total load for the full week. For the first week where we have the peak heating load, lowest solar coverage is recorded at 44%. This percentage increased for every week until it reached 100% for weeks 4, 5 and 6. Table 1 shows the load covered by the solar energy during the 6 weeks of the cycle. We can conclude that although the solar system did not cater for the total load for all the weeks, yet it satisfied 100% of the load during 50 % of the time. So, we have the last 3 weeks with zero auxiliary heater operation. Moreover, it can be conclude that sizing the system in order to cater for 100% of the load all the time would make it oversized for other weeks and might not be cost-effective. Omar Mogharbel1, Kamel Ghali1 ,Nesreene Ghaddar1 and Mohamad G. Abiad2 METHODOLOGY