Design and Fabrication of Solar Powered Mobile Cold Room Group Members Shikongo JT Haraseb Benade Pinzi F.L Student No 218037228 NOVEMBER 18, 2022 Table of Contents ABSTRACT................................................................................................................................................ 2 EXECUTIVE SUMMARY ............................................................................................................................ 3 INTRODUCTION ....................................................................................................................................... 3 AIM AND OBJECTIVE ............................................................................................................................... 3 METHODOLOGY ...................................................................................................................................... 4 Selection of charge controller ................................................................................................................. 4 Design Flow Chart ................................................................................................................................... 5 Block Diagram ......................................................................................................................................... 6 Design Procedures .................................................................................................................................. 6 DESIGN .................................................................................................................................................... 6 Determination of Project Values ............................................................................................................ 7 Load requirement ................................................................................................................................... 8 Sizing of the main control switch ............................................................................................................ 8 Selection of charge controller ................................................................................................................. 9 CONSTRUCTION ...................................................................................................................................... 9 RESULTS ................................................................................................................................................ 11 CONCLUSION......................................................................................................................................... 15 PROBLEMS JUSTIFICATION.................................................................................................................... 16 REFERENCES .......................................................................................................................................... 16 FIGURE 1: CONDENSER AND EVAPORATOR ASSEMBLY......................................................................................................... 2 FIGURE 2: 3 DOOR UNDER DOOR FRIDGE .......................................................................................................................... 3 FIGURE 3: DESIGN FLOWCHART...................................................................................................................................... 5 FIGURE 4: BLOCK DIAGRAM OF THE SOLAR POWERED COLD ROOM ...................................................................................... 6 FIGURE 5: SCHEMATIC DIAGRAM OF ALL COMPONENTS ...................................................................................................... 7 FIGURE 6: DIRECT COMPRESSOR VALUES ......................................................................................................................... 7 FIGURE 7: CHARGE CONTROLLER .................................................................................................................................... 9 FIGURE 8: COLD ROOM PUT TO THE TEST ....................................................................................................................... 10 ABSTRACT A refrigeration system that makes use of solar power is The Design and Fabrication of Solar Powered Mobile Cold Room. It was started due to the country's rural areas' erratic power supply and the lack of a grid supply in some places where it was required. The following parts make up the mobile cold: D.C. compressor (Danfoss BD92K), solar battery (12V, 200AH), solar panel (12V, 600W), charge controller (40A, 12V), 500L compartment. The solar panel supplies the energy instead of the national grid or a generator system. The solar panel that gathers sun energy is part of the solar-powered mobile cold room. Solar energy from the panels is transformed into electrical energy and stored in the battery. The power for the cold room is normally provided by the solar panel, but when the output power of the solar panel is lower, the battery provides the extra power. The battery is recharged when excess amount of power is produced by the solar panels. The output supply of the batteries and the solar panel is DC with voltage of about 12V. A microcontroller was used to show the freezer's internal temperature and protect the compressor by turning it off for 60 seconds whenever the door is opened. The battery and solar panel are connected by a charge controller, which controls the voltage from the solar panel for charging the battery. When there is no sunshine or just weak sunlight, the battery supply is used to power the D.C compressor of the cool chamber. When the battery is fully charged, the device can operate for 18 hours without sunshine; it also has a large storage capacity of 1926 litters and a longer operating period than earlier solar refrigerators. Figure 1: Condenser and Evaporator Assembly EXECUTIVE SUMMARY This fabrication was carried out to further enhance the global knowledge of using renewable energy resources which in turn reduce the challenges faced in the preservation of perishable food items, drinks, harvest, and beverages for a long period before they are finally consumed by the end users. However, the cold room will be built on a (cart) and will be accommodated with the batteries and every other accessory needed. INTRODUCTION To close the gap in the availability of perishable food products, cold drinks, and beverages in rural areas, a shift toward the utilization of renewable energy resources became imperative. Given that food and other perishable things decay at room temperature, this design and manufacture were intended to close the gap between socioeconomic circumstances and unreliable supplies of perishable food items, drinks, and beverages in remote areas. The tools of daily life include refrigerators. Uninterrupted power should be supplied to refrigerators to maintain cooling service. Figure 2: 3 door under door fridge retrieved from https://www.bar-fridges-australia.com.au/ Photovoltaic (PV) systems are especially well suited for distant sites since they offer a reliable, independent electrical power source right at the point of usage. Because of this, rural areas are increasingly using PV solar energy for refrigeration (Mehmet, 2011). Due to its smaller compressor, a refrigerator or freezer powered by photovoltaic (PV) technology has a lower cooling capacity than a standard machine. Due to limited resources and expensive storage costs, using energy efficiently in solar or other renewable energy-powered systems is more important than in other systems (Ekren, 2011). AIM AND OBJECTIVE The aim of this project is to design and fabricate a Solar Powered Mobile Cold Room The following are the objectives of this fabrication; To use renewable energy sources to eliminate the use of fossil fuel and electricity to power the cold room To Bridge the gap of non-availability of cold drinks in Rural Areas. To extend the shelf life of perishable food items and post-harvest in off-grid areas. METHODOLOGY In designing and fabricating a micro-controller-based solar mobile cold room, there are many guides involved in the design. This guide provides the information to correctly select the compressor, batteries, solar array, wiring, blower (cooling fan), limiting resistors, metal sheet, aluminium sheet, and many others. The method adopted in this study is purely experimental. The device was designed using mathematical analysis and was converted into an experiment by following the design results obtained in procuring the needed materials for the design. Principle Applied Procedures used in this project work and they are: 1. Freezer volume (constructed i.e., 1.926L) 2. Load requirement Determination of backup size Batteries stores direct current electrical energy for later use (Washington State University Extension, 2009). The stored energy is later used at night in the absence of sunlight. The formula below was used to calculate the backup size 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑠𝑖𝑧𝑒 (𝑇𝑜𝑡𝑎𝑙 𝑊𝑎𝑡𝑡 − ℎ𝑜𝑢𝑟𝑠 𝑝𝑒𝑟 𝑑𝑎𝑦 𝑢𝑠𝑒𝑑 𝑏𝑦 𝑎𝑝𝑝𝑙𝑖𝑎𝑛𝑐𝑒𝑠 × 𝐷𝑎𝑦𝑠 𝑜𝑓 𝑎𝑢𝑡𝑜𝑛𝑜𝑚𝑦) = (𝐿𝐸𝑂𝑁𝐼𝐶𝑆, 2013) (0.8 × 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑣𝑜𝑙𝑡𝑎𝑔𝑒) Note that; days of autonomy are the number of days that you need the system to operate when there is no power produced by PV panels to get the required Ampere-hour capacity of a deep-cycle battery. Similarly, 0.8 is for the depth of the battery discharge (compressors.danfoss.com). Determination of PV size a photovoltaic system is an array of components designed to supply usable electric power for a variety of purposes. When light shines on the cell it creates an electric field across the layers. The stronger the sunshine, the more electricity is produced (Al Qdah, 2015). This is used to charge the battery. Stated in equation 5, is the formula used to calculate the Total Wp of PV panel capacity; Total Wp of PV panel capacity = Total PV energy needed / 3.43 (Wp) (5) So that; Number of PV panel needed = Total Wp of PV panel capacity/selected rating (measured in modules) (LEONICS, 2013) (6) Where: WP = watt peak of the panel Selection of charge controller The Solar Charge Controller or solar charge regulator is basically a voltage and/or current regulator to keep batteries from overcharging (Akinola, 2010). It basically regulates the output voltage and outputs current coming from the solar panels before going directly to the battery assembly. The solar charge controller regulates this 21-volt output of the panel down to what the battery needs at the time, also as per the requirement of the mobile cold room compressor at that period of time. This voltage varies from about 10.5 volts to 14.6 volts, depending on the state of charge of the battery and the surrounding temperature at that given point of time. Secondarily, it also provides protection against Overvoltage surges which would enhance the project’s controllability. It also prevents complete draining (deep discharging) by discharging only to 70-80% of its total capacity, thus enhancing the operating life of the batteries and providing a good payback option (Akinola, 2010). The size of the charge controller used in this project was calculated using the formula Solar controller rating = No of strings x Isc of the panel x 1.3 (7) Where: Isc = short circuit current of PV array Design Flow Chart This section shows the sequence of operation of the flow chat in figure 1 START INITIALIZING DISPLAY ON LCD WANT TO ENTER A NEW TEMPERATURE YES DOES BUTTON PRESS BEFORE 10 SECONDS NO DO FINAL SETTING CONFIGURATION YES IF SET TEMPERATURE VALUE IS REACH ENTER NEW TEMPERATURE OFF THE COLD ROOM NO COLD ROOM IS OPEN Figure 3: Design Flowchart Block Diagram The microcontroller based solar powered freezer consist of eight stages and these stages are shown in figure 4. SOLAR PANEL CHARGE CONTROLLER BATTERY MICROCONTROLLER CONTROL UNIT COLD ROOM FAN Figure 4: Block Diagram of the Solar Powered Cold Room Design Procedures The design procedures were broken down into the following steps: 1. 2. 3. 4. 5. 6. 7. Selection of Compressor Metal sheet Aluminium sheet Determination of total load Duration of Operation (Battery Selection) Selection of Panel Programming of the microcontroller The above-listed parameters were used to determine the efficiency of the refrigerator required and consequently the amount of energy needed to power the system. DESIGN The adopted design principle for this project is that of a systematic approach to the design; it entails the selection of appropriate components workable circuit biasing, the selection of components to be used based on their operational characteristics, and the utilization of the right materials for the construction and perfect finishing. Schematic Diagram of the work Figure 5 shows the schematic diagram of the project which entails the layout of each component. Figure 5: Schematic Diagram of all Components Listed (figure. 5) are the components from the schematic diagram as used in this work. 1. 2. 3. 4. 5. 6. 7. 8. Solar Panel (12V/600W) Charge controller(12V/40A) Solar Battery(12V/200AH) Fuse Main switch Light emitting diode (LED) 12VDC fan DC Compressor (BD92K) Determination of Project Values Using Schematic Diagram 1. Selection of direct current compressor Table .1 Direct Current compressors with their input and output power (compressors.danfoss.com). Figure 6: Direct Compressor Values From Figure 6, the power of the selected compressor is found to be 100W, as seen in the shaded portion. P=100W Load requirement In calculating the total load in this project work, equation 1 was adopted. PT = PC + PF + PMCP (equation1) Recall that Pc = 100W PF = 4.8W in that case, PT = 100 + 4.8 + 6 = 110.8W Or by using equation 2; Total load = total load required x period of usage (Wh/day) (equation 2) 110.8W x 12 = 1329.6Wh/day So that, the total PV energy needed = total load x 1.3 (Wh/day) (equation 3) 1329.6Wh/day x 1.3 = 1728.48Wh/day Sizing of the main control switch Since the total load power has been calculated using equation 3.1 and the result obtained is found to be 110.8W, joules’ law can be applied and that is, P = IV P = 110.8, V =12, Therefore I Switch = 110.8/12 = 9.23A. In this project, the switch used was that of 15A, which is capable of handling the required load current. Determination of backup size Recall that equation 4 is suitable for the battery selection 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑠𝑖𝑧𝑒 = (𝑇𝑜𝑡𝑎𝑙 𝑊𝑎𝑡𝑡 − ℎ𝑜𝑢𝑟𝑠 𝑝𝑒𝑟 𝑑𝑎𝑦 𝑢𝑠𝑒𝑑 𝑏𝑦 𝑎𝑝𝑝𝑙𝑖𝑎𝑛𝑐𝑒𝑠 × 𝐷𝑎𝑦𝑠 𝑜𝑓 𝑎𝑢𝑡𝑜𝑛𝑜𝑚𝑦) (0.8 × 𝑛𝑜𝑚𝑖𝑛𝑎𝑙 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑣𝑜𝑙𝑡𝑎𝑔𝑒) 𝐵𝑎𝑡𝑡𝑒𝑟𝑦 𝑠𝑖𝑧𝑒 = (110.8 × 18ℎ𝑜𝑢𝑟𝑠 × 1) = 208𝐴𝐻 (0.8 × 12) The nearest available battery in the market is 200AH, therefore, a 2 x 100AH battery was used Determination of PV size Recall that equation 5 is appropriate for PV selection Total Wp of PV panel capacity = Total PV energy needed / 3.43 (Wp) (equation 5) But in equation 3, Total PV energy needed = 1728.48Wh/day Therefore, Total Wp of PV panel capacity = 1728.48Wh/3.43 = 503.93Wp, Similarly, Number of PV panel needed will be calculated thus; Number of PV panel needed = Total Wp of PV panel capacity/selected rating (equation 6) = 503.93/150 = 3.359 modules Actual requirement = 4 modules Here, charging time is assumed to be 8hrs = 200 8 = 25: Therefore, a 4 X 150W/6.5A solar panel was used to charge the battery effectively for the chosen time Selection of charge controller Recall that in selecting the charge controller rating, the number of strings and the panel short-circuit current must be known; as such equation 7 was used Solar controller rating = No of strings x Isc of the panel x 1.3 = 4x6.5x1.3 = 33.8A Therefore, a 12/40A charge controller was selected for this project work. Circuit Diagram the circuit diagram for micro controller based solar based cold room system is shown in figure 4. Figure 7: Charge Controller CONSTRUCTION The building of the microcontroller-based solar-powered mobile cool room began with the creation of a 500-liter cold chamber (figures 5–13) made of mild steel and aluminum, with an approximate volume of 498750cm3 (V = w x b x h cm3). A 12V D.C compressor, model number BD92K, was chosen, and R600a was pumped into it. The cold room was powered by a 12V/200AH solar battery, and each piece of the building was put together to create an unified unit. Using bolts and nuts, the chosen DC compressor was attached and securely tightened. The compressor's discharge low suction line (pipe) and the condenser pipe coils positioned at the back of the cold air intake were joined by welding. Figure 8: Cold Room put to the test RESULTS At the end of the fabrication, a functional mobile Solar Cold Room having the wall capacity of 1926L with about 17.3 hours of cooling when fully loaded was fabricated. Project name: 3 Door Under bar Fridge Coolselector2 version: Printed: 5.1.2. Database: 91 Preferences used: All applications Sunday, 20 November 2022 Refrigerant: R134a Evaporating dew point temperature: -5.0 °C Ambient temperature: 33.0 °C Evaporating pressure: 243400 Pa Sub cooling: 3.0 °C Useful superheat: 6.5 °C 0 °C Additional superheat: 0 °C Additional sub cooling: Altitude: 0 m Return temperature: Rating conditions: 1.5 °C Required capacity: gas cooling Custom 268 W Match percentage (127.9%) is higher than maximum 110%). Model OP-MCGC006FRA04G Code number 114X0203 Compressor model FR6GX Product range Optima™ Product version A04 Refrigerant R134a Cooling [W] 343 COP [W/W] 1.67 cooling Total power [W] 205 Total current [A] 1.241 Frequency [Hz] 50 Power supply 220 - 240 V 1 ph. Tc [°C] 43.5 Figure 9: Refrigerant R134a properties Cold room 1 - Liquid line Operating conditions (synchronized across application) Refrigerant: R134a Mass flow in 0.002391 kg/s line: Evaporating temperature: -5.0 °C Evaporating pressure: 243400 Pa Useful superheat: 6.5 °C Additional 0 °C superheat: Discharge temperature: 65.6 °C System and line: Dry - Liquid line Line total Pressure drop Saturation temperature drop 870400 Pa 48.5 °C Cooling capacity: 343 W Heating capacity: 451 W Condensing temperature: 43.5 °C Condensing pressure: 1114000 Pa Sub-cooling: 3.0 °C Additional sub-cooling: 0 °C Pipe. Piping: Copper pipe DIN-EN 6 Length Angle 1.00 0 m Deg Pressure drop Saturation temperature drop Velocity, in Connection 151.6 Pa 0.0 0.17 OK °C m/s 95.78 Pa 0.0 °C 0.17 Open Ok m/s EVR. Solenoid valve: EVR 3 v2 Pressure drop Saturation drop Velocity, in Valve state Connection Figure 10: Liquid Line temperature Figure 11: Suction Line Cold room 1 - Suction line Operating conditions (synchronized across application) Refrigerant: R134a Cooling capacity: 343 W Mass flow in line: 0.002391 kg/s Heating capacity: 451 W Evaporating temperature: -5.0 °C Condensing temperature: 43.5 °C Evaporating pressure: 243400 Pa Condensing pressure: 1114000 Pa Useful superheat: 6.5 °C Sub cooling: 3.0 °C Additional superheat: 0 °C Additional cooling: 0 °C Discharge temperature: 65.6 °C System line: and Dry - Suction line Line total Pressure drop 95.92 Pa Saturation temperature drop 0.0 °C Pipe. Piping: Copper pipe DIN-EN 12 Length 1.00 m Angle 0 deg Pressure drop 95.92 Pa Saturation temperature drop 0.0 °C Velocity, in 2.60 m/s Connection OK sub Cold room 1 - Cold room details Evaporator conditions Cooling capacity: Dew point temperature: Air inlet temperature: Mean temperature difference: Estimated fan power: Estimated defrost power: 343 -5.0 5.0 10.0 28 215.6 Calculated cold room load: Transmission: 93 W Infiltration: 52 W Ice on evaporator: 2W Goods total: 59 W Goods, cooling: 59 W Goods, respiration: 0W Light: 5W People: 28 W Fans: 28 W Other: 0W Defrost: 1W Total: 268 W Cold room details: Room conditions: Temperature: 5.0 °C Relative humidity: 80.0 % Operating hours: 17.3 h Inner dimensions: Length: 1.07 m Width: 1.20 m Height: 1.51 m Goods: Type: Mixed products Quantity per day: 217.2 kg Inlet temperature: 10.0 °C Air exchange (infiltration): Figure 12: Evaporator Conditions W °C °C °C W W Temperature: 32.0 °C Relative humidity: 32.7 % Door openings: Regular Air exchange rate: 35.9 Heat transfer: Panel thickness: 0.0750 m Temperature of surroundings: 32.0 °C Temperature below floor: 15.0 °C Floor is insulated: Yes Additional loads: Lights: 40 W Fans: 28 W People: 2.0 h/day Other: 0W Defrost: Defrost type: Natural Defrosts per day: 4.0 Defrosts time: 30 CONCLUSION A conventional prototype DC Cold Room was designed, and mounted in the cart. This project bridged the gaps of availability of cold drinks and the eradication of food spoilage as a result of non-constant/inadequate in rural areas. Figure 14: Fixing of the Evaporator after first padding fabricated, the nonperishable power supply Figure 13: Mounting of the microcontroller and the charge controller PROBLEMS JUSTIFICATION The device can be used for the storage of food items, drinks, beverages, and vaccines. Mobile Solar Cold Room is ideally suited for countries, places, and remote areas where electrical power is epileptic or not easily available. It promises to be in high demand by those whose businesses are centred on perishable food items, beverages and drinks, and primary health centres. It also bridges the gaps of non-availabilities of perishable food items, drinks, and beverages in rural areas. References • Al Qdah, K. (. (2015, October 24). Performance of Solar- Powered Air Conditioning System under AlMadinah AlMunawwarah Climatic Conditions. Smart Grid and Renewable Energy. Retrieved from http://dx.doi.org/10.4236/sgre.2015.67018 Ekren O., Y. A. (2011). Experimental Performance Evaluation Of A PvPowered Refrigeration System. Electronics And Electrical EngineeringIss 1392 , 1215. Ewert, M. K. (1998). Experimental Evaluation of a Solar PV Refrigerator with Thermoelectric, Stirling and Vapor Compression Heat Pumps. Proceedings of Solar , 98. Retrieved from http://solar.nmsu.edu/pub Mehmet, A. A. (2011). International Journal Of Physical Sciences. Experimental Study Of A MultiPurpose Pv-Refrigerator System, 6(4), 746-757 . Refrigeration, F. L. (2017, January 15). Ice Maker Machines, Commercial Refrigeration & HVAC. Retrieved from Cold Rooms, Freezer Rooms, Blast Freezers, Island Freezers, Under Bar Fridges: http://freezelogic.co.za/commercial-refrigeration-repairs-installation-service/ Stoecker, W. F. (2010). Refrigeration and Air Conditioning Publisher McGraw . Refrigeration and Air Conditioning Publisher , 212-216. 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