Design and Implementation of a PV-Integrated Solar Dryer Based on Internet of Things and Date Fruit Quality Monitoring and Control

quality of the three most popular date fruit varieties and determine the most e ﬀ ective drying method, with an algorithm that operates the system automatically for optimal performance and high-quality products. The automatic solar dryer (ASD) signi ﬁ cantly a ﬀ ects the ﬁ nal moisture content and color characteristics and reaches the equilibrium moisture content (EMC) at a faster rate for dried date samples compared to the OSD. The drying rate of ASD was 29.03% (Sakkoti), 31.04% (Malkabi), and 25.49% (Gondaila) higher than OSD. Also, the dried date fruit samples reached EMC on the ASD after 8 days for both Malkabi and Gondaila and 9 days for Sakkoti, while it took 14 to 15 days on OSD. The maximum open circuit voltage V oc , short circuit current I sc , and output power P output were 41.70 V, 8.84A, and 365.09W, respectively. All values of total color change ( Δ E ∗ ) after open-air drying of dry date varieties were higher than solar drying for both drying systems. This study can be then more helpful for producers of dried foods.


Introduction
Egypt occupies first place in the world in the production of dry date fruit, with an annual production volume of over 1.65 million tons [1].Immediately after harvest, dates contain a high percentage of moisture, which must be properly disposed of in order to maintain chemical composition and natural properties and also for long-term storage [2].One of the best methods for the preservation of agricultural products is drying [3].According to [3,4], date fruit must be completely dried to the required moisture content (MC) in order to maintain their quality while being handled and stored.The most common method of date fruit drying throughout history has been open sun drying (OSD) where the date fruits are dried in the open air.This method presents a risk due to many contaminated resources from sand-laden winds, rain, animals, harmful insects, dust, and soil.The OSD process is difficult because air temperature and relative humidity of air cannot be controlled daily, and it also takes too long [5][6][7].So, the open-air drying method typically fails to meet the necessary quality standards, and the items cannot be sold on the global market [8].
Unlike an OSD, solar drying (SD) helps to control hot airflow and both temperature and relative humidity of the air inside the drying chamber and therefore achieves a better quality of dried products.Also, the dried product is protected from outside environment and extraneous factors such as attacks of rodents and insects.Since SD occurs in an enclosed drying chamber, it is not only faster than OSD but also costs less than industrial drying [9] and improves the product quality after the drying process as well, such as color or nutrients [10].There are also many modern systems that can be used for drying such as ultrasound-assisted osmotic dehydration (UAOD) [11], infrared dryer systems (IDS) [3], and heat pump dryers (HPD) [12,13].In terms of addressing issues with drying time, efficiency and cost, and contamination, SD technology is currently the most effective and practical food drying technology [14].Thus, the OSD (traditional drying) technology should be replaced with SD [15][16][17][18].
Solar dryers are classified into three types, namely, direct solar dryers (DSD), indirect solar dryers (ISD), and hybrid solar dryers (HSD) [2,19].But regarding the mode of operation, solar-driven dryers are further classified into two groups, namely, natural convection solar dryers (NCSD) and forced convection solar dryers (FCSD), which employ passive and active modes, respectively [2,[20][21][22].In order to have a continuous and suitable hot airflow rate, FCSD has been introduced.This SD requires a fan to force hot air through the drying chamber.In contrast to NCSD, being the more expensive construction, the forced conversion dryers are dependent on electrical or other sources of energy.Hence, the energy costs have to be compensated with a reduction in drying time, higher drying capacity, reduction of mass losses, and better quality of the product [23].
Using a sustainable energy source is the primary advantage of SD since it eliminates the need for electricity or the burning of fossil fuels.Solar energy is also abundant, nonpolluting, and nonmonopolistic [24,25].Replacing renewable energy sources with traditional fuels can result in significant energy savings and a consequent decrease in the emission of greenhouse gases (warm gases) like CO 2 , which contribute to global warming and climate change [26,27].Several researchers have created, tested, and assessed many designs of SD so far.The majority of designs are regionspecific since the solar intensity varies depending on the experiment location.SD is most efficient in tropical regions.
Reference [28] designed a passive flat plate collector solar dryer (FPC-SD) for agricultural products and evaluated its performance.The difference between the dryer inlet and ambient temperature was recorded for certain days and was 24.6 °C.The FPC-SD achieved 36.36%sav-ing in drying time against OSD.Reference [27] designed and analyzed an SD for the midlatitude region for apple drying and reported a reduction in its moisture content from 86% to 8.12% (wet basis) within 9 hours and 20 minutes at an average irradiance of 534.45 W/m 2 .The overall dryer efficiency was estimated to be 17.89%.Reference [29] analyzed the performance of a hybrid indirect passive (HIP) solar dryer and conventional active-mode solar photovoltaic and electric dryer with an auxiliary thermal backup system against the OSD method for drying fruits.The fruit drying duration for the SPE, HIP, and OSD methods was 10 h, 18 h, and 30 h, respectively.The drying efficiency of the improved HIP dryer was comparable to the SPE dryer and was 18% higher than the OSD method.Reference [30] designed and fabricated a direct natural convection solar dryer for tapioca (Manihot esculenta) drying and reported a reduction in its moisture content from 79 to 10% on a wet basis at ambient conditions (32 °C, 74% relative humidity).Reference [31] evaluated the performance of wooden and pyramid shape DSD for potato (S. tuberosum) drying which reduced overall drying time by 2-3 h when compared with OSD.Reference [32] developed a prototype direct mode natural convection mud-type SD for drying maize.The moisture content was observed to reduce from 29 to 12% on a wet basis.The dryer achieved 55% saving in drying time against open sun drying.The drying efficiency of the dryer and OSD method was found to be 45.6% and 22.7%, respectively.Reference [15] developed an indirect solar tunnel dryer for the dehydration of various agriculture products with the capability of reducing moisture content from 93.35 to 11.50% on a wet basis.The drying time was observed to decrease by 26.9% in comparison to OSD.
The advancement of computer, control, and sensor technology has made it possible to create a smart dryer for certain items.Such a technique can be cost-effective in monitoring and identifying a wide variety of food quality attributes that change throughout the course of the drying process by controlling the drying conditions and producing high-quality goods.Electrostatic sensor technology and drying environment management systems are two significant subcategories of smart drying technology [33].
The current study is aimed at (1) designing and implementing an experimental validation of a developed solar dryer based on IoT technology and integrated with a PV model.It considers date fruit quality monitoring and controlling of the three most popular date fruit varieties in Aswan, Egypt (2) identifying some of the physical characteristics of tested date samples to create the best technology so as to process them in the future In order to achieve the objectives of the research, a set of electronic circuits has been designed to obtain a selfoperating dryer.One of the electronic circuits senses the dry temperature and relative humidity of the air outside 2 International Journal of Energy Research and inside the dryer.Another electronic circuit measures the intensity of light.Also, there is an algorithm that controls the speed of airflow, as well as turning on/off the fan circulating air through the dryer.

Materials and Methods
This current study was carried out on the most popular date fruit varieties (Sakkoti, Malkabi, and Gondaila) cultivated in Aswan, Egypt, as shown in Figure 1.All experiments related to the drying process and determining some physiomechanical properties and color characteristics of three date varieties under test were carried out at the Faculty of Agricultural and Natural Resources (FANR), Aswan University, Aswan, Egypt (latitude and longitude of 24 °5′ 20.1768 ″ N and 32 °53 ′ 59.3880 ″ E, respectively).Six kilograms of dates for each variety was collected in October 2022.Prior to the measurements, the date fruit samples were collected from Aswan City.The date fruit samples were stored immediately after harvesting in polyethylene bags at 4 °C.
2.1.Physical and Mechanical Properties.At the FANR, laboratories of food science and soil physics, all experiments were conducted over the course of three days at an ambient air temperature range of 30 to 32 °C.All physiomechanical properties were estimated for fresh date fruit.
2.1.1.Axial Dimensions.With the aid of Vernier calipers that read 0.01 mm, the main dimensions were measured regarding length, width, and thickness.The average length was determined by the longest dimensions in the longitudinal direction.Among the majority of dates, 100 date fruits are randomly chosen, and their triaxial measurements are measured.It reports the average value of 100 observations, according to [34].
2.1.4.Surface Area (S).Using Equation ( 4), the surface area of a fresh date fruit was calculated by analogy with a sphere of a certain geometric average diameter, according to [34].
2.1.5.True Density (ρ t ).Equation ( 5) is used for the calculation of the fresh date fruit density (g/cm 3 ) [37,38]: 2.1.6.Bulk Density.Using the mass and volume (Equation ( 6)) as reported by [31,39], bulk density (g/cm 3 ) was calculated by filling an empty glass container with the fresh date that was poured from a fixed height, having the volume and mass predetermined, and weighing: 2.1.7.Porosity (ε).The ratio of the variations in fresh date fruit and bulk density to the fruit density value was used to calculate porosity using Equation (7) as stated by [31,40]: 2.1.8.Repose Angle.The repose angle is the angle at which the fresh date fruit will rest in a pile relative to the horizontal plane.The usual circular platform method was used to determine the date fruit's repose angle.The height of the cone was measured using a stainless-steel scale, and the repose angle was determined using this formula.The repose angle was calculated using Equation ( 8) as stated by [41]. 3 International Journal of Energy Research 2.2.The Needed Calculations for an ASD.The size and dimensions of the ASD were determined depending on the solar collector area needed for each kilogram of fresh date fruit to be dried.The peak temperature inside the drying room (chamber) is important for reducing the MC on the fresh date fruit to a safe level for storage and handling as well as for preserving the maximum functional properties and nutritive values.

Tilt Angle (λ).
Using Equation ( 9) as stated by [42], the SC's tilt angle was determined at latitude 24 °5′ 20.1768 ″ N.However, an inclination angle of 20 °was adjusted during the design to avoid the excessive height of the dryer and to facilitate the follow-up of the drying process.λ = 2 66 °+θ 9 2.2.2.Amount of Moisture (M w ).Equation (10), which was employed by [43], was used to determine the MC that needed to be removed from the fresh date fruit samples.
. Quantity of Heat.The quantity of heat needed for raising the temperature of the fresh date samples to the hot air temperature inside the drying room (Q 1 (J)) was calculated based on Equation (4) according to [44].
Also, Equation ( 12) is used to calculate the amount of heat needed to evaporate the MC of the fresh date fruit (Q 2 (J)) according to [45]: Equation ( 13) was used to determine the total heat (Q T (J)) required for drying the fresh date fruit samples as reported by [45]: 2.3.Dryer System Construction and Materials.The ASD that was developed was constructed from many parts that are environmentally friendly and available in local markets.It consists of the following parts: (1) a solar collector, (2) a drying room and trays, (3) an automatic controller, (4) a PV model, and ( 5) a measuring unit, as shown in Figures 2 and 3.The description of ASD can be summarized as follows: 2.3.1.Solar Collector (SC).The SC frame was manufactured of angle steel (L) 3 * 3 cm with 300 cm length and 100 cm width, as shown in Figure 4; the surface of the solar absorber was made of galvanized corrugated sheets with a thickness of 1.0 mm, and it was painted a matte black color in order to increase the percentage of absorbed sun rays.Thermal insulation was made of sawdust between the absorbent surface and the main frame to reduce the quantity of heat loss.
A permeable glass cover with a thickness of 3.0 mm was used to allow the largest possible amount of sunlight to pass through and fall on the absorbent plate.The distance between the absorbent plate and the glass cover is 15 cm.The SC is oriented in a north-south direction at an inclination angle of 20 °with the horizontal.The ASD was manufactured from two separate parts, the SC and the drying room, to facilitate transportation, installation, maintenance, repair, etc., as they are installed with us using temporary connections (such as bolts and nuts).There is also an AC exhaust fan at the upper point of the drying room.

Drying Room and Trays.
According to Figure 4, the drying room's primary structure was constructed from 3 0 * 3 0 cm square metal bars that were 100 cm in length, 45 cm in width, and 98 cm in height.All sides of the SC were covered with two layers of galvanized sheet, each 1.00 mm thick, with a layer of sawdust between them to reduce heat loss through the sides.The chimney fan creates a disturbance in the air inside the drying room, so it draws atmospheric air to pass through the SC and then into the drying room from the bottom, passes through the drying trays, and then is exited from the top through the chimney fan.The drying room is designed to accommodate nine trays   The air circulation was done automatically by using an automatic controller to maximize the drying rate at the available conditions, where the control circuit has been programmed to turn off the chimney fan when the air temperature inside the drying room is ≤20 °C, and thus, the dryer works by an NCS as a result of the air temperature difference; also, when the air temperature inside the drying room is ≥20 °C, the chimney fan will turn on automatically and suction the hot air from the SC to the drying room, passing through the dates and drying trays, and exit the air to the outside, and thus, the dryer operates with an FCS, as shown in Figure 6.
In addition, the controller has been programmed to stop the chimney fan in case the solar radiation is ≤100 W/m 2 and at night, which leads to the date samples not being moistened again and the chimney fan being restarted again in case the solar radiation is ≥100 W/m 2 or the temperature of the air entering the drying room is ≥20 °C.Accordingly, we find that the dryer operates automatically without any human action, which leads to raising the drying efficiency and reducing the time required for the drying process.
Also, the chimney fan operated at different airflow rates (3.12 and 4.96 m 3 /min), as reported by [46], uses an AC voltage regulator device (dimmer) that was used for controlling the AC suction fan flow rate.The chimney fan operates at an airflow rate of 3.12 m 3 /min when the air temperature entering the drying room is ≤40 °C and at an airflow rate of 4.96 m 3 /min when it is 40 ≥ °C.2.3.5.Measuring Unit.As indicated in Figures 7 and 8, different positions will be used to measure temperature and humidity on the ASD.The upper point of the drying room (chimney) will also be used to measure airspeed (air flow rate).A DHT-22 sensor integrated with the Arduino Uno board will be used for measuring both air temperature and humidity; after that, the collected data will be processed by a microcontroller and transferred to a laptop or smartphone through Bluetooth (HC-05).

Open Sun Drying (OSD).
As shown in Figure 11, fresh date samples of three date varieties (Sakkoti, Gondaila, and Malkabi) were dried using an OSD (open air).The process of drying dates was carried out in both the OSD and the    2.5.Performance Analysis of the Developed ASD.Understanding and calculating ASD efficiency can be done by analyzing their performance.Based on the partial pressure of water vapor in the air inside the ASD and the date fruit, the basis for evaluating ASDs is the amount of moisture that is eliminated from the date fruit.We will reach an equilibrium condition known as EMC if we circulate a stream of air through a sample for a long enough period of time.This condition depends on the air temperature, air relative humidity, and the characteristics of the date fruit to be dried, as stated by [27].The following factors were used to evaluate ASD's performance: 2.5.1.Drying Rate (R d ).The quantity of moisture removed from the dried date fruit to achieve the appropriate MC within a specific period was known as the drying rate.By measuring the MC of random samples of date fruit at the end of each day and calculating the time needed for drying, it was possible to calculate the percentage of remaining solids.It was calculated using Equation ( 14), as developed by [43].
2.5.2.Thermal Balance for Photovoltaic (PV) System.The energy consumed by the AC suction fan is used as an output source of energy in the calculation of the efficiency of a PV model, according to [47], as shown in According to [48], the fill factor may be defined as the ratio of the maximum output power of the PV panel (P max ) to the output power mentioned in Equation (15).

FF =
P max V oc × I sc 16 2.5.3.SC Efficiency.The efficiency is the ratio of the input power and output power of the SC.It was estimated according to Equations ( 17)-( 19) [46,49,50].
Ins coll t dt 17  International Journal of Energy Research Energy output from the SC (E input coll (J)) is given As mentioned above, the SC efficiency (η coll ) was calculated based on 2.5.4.Color Characteristics.Using a colorimeter (model: CR-410, Konica Minolta Sensing Americas, Inc., USA) and the International Commission on Illumination (ICI) color coordinates L * , a * , and b * (10 °observer at D65 illuminant), the color values of fresh and dried dates were measured.In L * , a * , and b * , color space is said to be the optimum color space for quantification in foods with curved surfaces, according to [51][52][53].

Results and Discussion
All characteristics were assessed with fresh date fruits with a constant MC.The initial MC of the different date fruit varieties for Sakkoti, Gondaila, and Malkabi was 17.64, 15.68, and 14.89%, respectively, on a dry basis.
3.1.Physiomechanical Characteristics.The dimensions of the date fruit are very essential physical parameters for drying, preservation, and processing (postharvesting technology).Also, it is very important to collect data to design and create novel smart machines, as stated by [56].This data can be used in the design and modification of different machine elements.These could be helpful in determining how many date fruits should be picked at once and the fruit's natural rest position and shape [34,57].The average physiomecha-nical characteristics of three fresh date varieties (Sakkoti, Gondaila, and Malkabi) are presented in Table 1.
According to the tabulated results in the following table, the highest percentages of fruit flesh (pulp) were from the cultivars Gondaila and Malkabi (90.24% and 88.75%, respectively).It was also found that the highest value for the length of the date fruit was in the Malkabi and Sakkoti cultivars (5.36 and 5.26 cm, respectively), while the lowest value was in the Gondaila cultivar.On the other hand, it was found that the lowest value of date fruit diameter (2.2 cm) and the highest number of date fruits per kilogram (89 fruits/ kg) were in the Sakkoti cultivar.
As shown in Table 1, the sphericity index (φ) values for the different types of dried date fruits ranged between 0.53 and 0.59.The sphericity index is a very critical parameter in designing and manufacturing date fruit handling machines.It averages that the outer shape of the date fruit ranges from ovoid to cylindrical [36].In Gondaila, Sakkoti, and Malkabi cultivars, the average values of porosity were 22.34, 23.81, and 26.93%, respectively.Date fruit porosity is a very critical parameter for the estimation of airflow resistance throughout the drying process as well as for storage analysis and study [31,40].Also, we found that the highest value of geometric average diameter, surface area, and repose angle was recorded with the Malkabi cultivar, as shown in Table 1.

Performance Analysis of ASD.
Using the abovementioned methodologies, an ASD was developed, constructed, and evaluated for drying three different cultivars of date fruit.Date samples were spread over three trays, one tray for each date variety.After that, the trays were placed in the dryer.All weather parameters (such as air temperature, relative humidity, wind speed, and intensity of solar radiation) were measured using the weather station of the (FANR).It was found through the data of the weather station that the lowest and highest values of solar radiation International Journal of Energy Research intensity during the test period were 685 and 860 W/m 2 , respectively.The of solar radiation intensity during the first day was from 7 a.m. to 4 as shown in Figure 12.
Figure 13 displays the daily air temperatures and relative humidity from 7 a.m. to 4 p.m., where it found slight differences between them during the test period.
There was a gradual increase in the ambient air temperature outside the ASD, which led to an increase in the temperature of the absorbent plate and thus an increase in the temperature of the air entering the drying room.The temperature of the air leaving the drying room decreased after passing through the date fruit.
The primary (final) values of the MC of the three Aswan dry date varieties that were dried inside the ASD were 17.64% (5.86%), 14.89% (4.41%), and 15.68% (5.73%) for date fruit varieties Sakkoti, Malkabi, and Gondaila, respectively, as illustrated in Figure 14.The initial (final) MC values of the three date fruit varieties that were dried in OSD were 17.64% (6.06%), 14.89% (5.56%), and 15.68% (6.58%) for date fruit varieties Sakkoti, Malkabi, and Gondaila, respectively (Figure 14).The dried date fruit samples had reached EMC on the ASD after 8 days for both Malkabi and Gondaila and 9 days for Sakkoti, while it took 14 to 15 days for OSD.
Figure 15 shows the relation between drying time and drying rate, where it was found that the relation between them is not linear and there is a decrease in the drying rate according to the drying time.The drying rate was highest at the beginning of drying and decreased at a decreasing rate until it ended with a zero value, as the maximum value of MC for different date fruit samples inside both drying systems was lost at the beginning of the drying process.These results were in agreement with [28,58,59].The drying rate of ASD was 29.03% (Sakkoti), 31.04%(Malkabi), and 25.49% (Gondaila) higher than OSD.
The maximum efficiency for the photovoltaic panel was 26.28%, which could be attributed to the solar radiation intensity that fell on the photovoltaic panel over the course  10 International Journal of Energy Research of the experiment.Also, we found that the maximum V oc , I sc , and P output were V, 8.84, and 365.09W, respectively, and the resulting data are shown in Figures 16 and The results shown in Figure 18 are based on the SC's thermal analysis, which takes into consideration the experiment's daytime weather and solar radiation intensity.
The energy input (E in ) to the ASD represents the energy that is gained from the sun's rays.Therefore, it depends directly on the solar radiation intensity falling on the SC during the day, and therefore, it is minimum in the morning at 32.27% at 7.00 am and increases gradually until it reaches the peak value at noon at 1.00 pm of 72.76% and then decreases gradually until it reaches the lowest value again at sunset at 4.00 pm of 59.1%.The output energy (E in ) depends directly on the energy entering the SC and the energy loss (E loss ) in the different parts of the SC.We find from Figure 17 that both the output and input energy curves have almost the same trend, and the differences represent      2, which illustrated that hue angle (H) values for the dried date fruit samples were higher than fresh samples for both drying systems, where hue angle (H) decreased from 49.03 (for fresh dates) to 40.78 (for open-air drying) and 39.91 (for an ASD), demonstrating a very significant shift from red to yellow color.Increases in parameter (a * ) showed a similar pattern to changes in chroma (C * ), which determines color intensity (higher values denote a more vivid color).Also, it was found that all values of total color change (ΔE * ) after open-air drying of dry date varieties were higher than solar drying for both drying systems; these results come in agreement with [13,[60][61][62].Furthermore, to prove the current work impact, a comparison of ASD with previously published works in the same field is provided in Table 3.

Conclusion
There are many challenges facing the process of drying dates in Aswan Governorate, Egypt.Large quantities of dates are harvested during the harvest season.Some dates are consumed fresh, which is a small amount compared to the volume of local production, while others resort to farmers drying them to sell them throughout the year, especially in the month of Ramadan.Surface drying in the open air is the most common method, due to the lack of SD technology.Ordinary farmers do not know how to deal with SDs; thus, the current study is aimed at developing an automatic solar dryer that works with IoT technology to be used in drying dates.Comparative tests were carried out between ASD and the OSD to dry the most famous date varieties grown in the Aswan region (Sakkoti, Malkabi, and Gondaila) to optimize the efficiency and effectiveness of the developed dryer.The results showed a significant increase in air temperature and a decrease in MC inside the drying room compared to the atmospheric air outside the dryer.The primary performance results of the ASD and OSD to the final MC values of the three dry date varieties that were dried inside the developed solar dryer were 5.86%, 4.41%, and 5.73% and 6.06%, 5.56%, and 6.58% for dry date varieties Sakkoti, Malkabi, and Gondaila, respectively.The final MC of the different date fruit samples dried with the ASD was less than that dried with the traditional method, and the consumed time to reach the EMC was reduced by about 50%.Also, the total color change (ΔE * ) of dried date fruit by OSD was higher than solar drying with the developed dryer.
The following are the future research directions: (1) Using an early sensor system to predict the drying time so as not to overdry and reduce drying costs (2) Drying under vacuum using solar drying systems (3) Developing a system to rotate the dried product inside the drying room to increase the uniformity of hot air distribution (4) Using nanotechnology in the manufacture of solar dryers

Nomenclature
V oc : Open circuit voltage (V) I sc : Short circuit current (A) P output : Output power (W) S: Surface area (cm 2 ) D: Arithmetic average diameter (cm) a: Average length (cm) b: Average width (cm) c: Average thickness (cm) D g : Geometric average diameter (cm) M a : Fresh date mass in atmospheric air (g) M w : Water density (g/cm 3 ) M: Mass of fresh date fruit (g) V: Volume of the empty glass container (cm ΔT: D i fference in temperature (K) η coll : Solar intensity efficiency (%) ρ a : Air density (kg/m 3 ) Δα * , Δb * , ΔL * : Changes in redness, yellowness, and lightness, after the drying process.

Abbreviations
PV: Photovoltaic IoT: Internet of things OSD: Open sun drying ASD: Automatic solar dryer EMC: Equilibrium moisture content MC: Moisture content SD: Solar drying UAOD: Ultrasound-assisted osmotic dehydration IDS: Infrared dryer system HPD: Heat pump dryer DSD: Direct solar dryer ISD: Indirect solar dryer HSD: Hybrid solar dryer NCSD: Natural convection solar dryer FCSD: Forced convection solar dryer FPC-SD: Flat plate collector solar dryer FANR: Faculty of agricultural and natural resources SC: Solar collector.

Figure 2 :
Figure 2: The main parts of the ASD (front view).

4
International Journal of Energy Research with a separation distance of 11 cm.The dimensions of each tray are 95 cm in length and 45 cm in width.During the test, 2.5 kg of each date variety was loaded on a separate tray.2.3.3.Automatic Controller.The ASD circuit shown in Figure 5 consists of the following parts: PV model, battery charger, battery, 2-channel relay model, Arduino Uno (ATmega328P), light intensity sensor (light-dependent resistors (5528 LDR) (5 mm)), laptop or smartphone, weather sensor (the SparkFun BME280 Atmospheric Sensor), and AC suction fan.

Figure 4 :
Figure 4: The main dimensions of the ASD (Dim. in cm).

Figure 3 :Figure 5 :Figure 6 :
Figure 3: The main parts of the ASD (back view).

2. 4 .
Experimental Set-Up (Experimental Parameters) 2.4.1.Solar Drying.For performance testing, the developed ASD was set up outside on the roof of the (FANR), as illustrated in Figures 9 and 10 . The ASD was used to dry date fruit samples.The drying process began on October 15, 2022, and continued for 9 to 10 days.
e t a ir fr o m d r y in g c h a m b e r (T 3 ) A b s o r b e r c o r r u g a te d s h e e t (T 2 ) G la s s o f s o la r c o ll e c to r (T 1 ) A m b ie n t a ir ( T 4 ) In le t a ir to d r y in g c h a m b e

Figure 7 :
Figure 7: DHT-22 sensors integrated with an Arduino Uno and Bluetooth unit for measuring temperature and humidity.

Figure 8 :
Figure 8: Location of the DHT-22 sensor on the ASD.

Figure 12 :
Figure 12: Variation in wind speed and intensity of solar radiation on the first day of the drying process (15 October 2022).

Figure 15 :
Figure 15: Effect of drying systems on drying rate.

Figure 16 :Figure 17 :Figure 18 :
Figure 16: Photovoltaic panel output current and voltage depending upon the time of day.

Table 1 :
Physical and mechanical properties.

Table 2 :
Color measurements of the different date fruit varieties.

Table 3 :
Comparison of the ASD with previously published SD. loss ).As well, the SC efficiency depends directly on weather conditions and is inversely proportional to the energy loss (E loss ).3.3.Color Analysis.Both drying processes generally resulted in a decrease in L * , a * , and b * values.The results are shown in Table Stand for the tones between yellowness (+) and blueness (-) a * * and b * * : Value of a * and b * after the drying process.