Solar Greenhouse Dryer Research Articles

Experimental and simulated investigations of the performance of the solar greenhouse dryer for drying cassumunar ginger (Zingiber cassumunar Roxb.)

This paper presents experimental performance of the greenhouse solar dryer for drying of cassumunar ginger (Plai). The dryer consists of a parabolic roof structure covered with polycarbonate plates on a concrete floor. The base of the dryer is a concrete floor with an area of 9×12.4 m2. Nine DC fans powered by three 50-W PV module were used to ventilate the dryer. The dryer was installed at Sa Kaeo province (13.49°N, 102.21°E), east of Thailand. To investigate the experimental performances, 300 kg of cassumunar ginger was dried in the solar greenhouse dryer. The drying air temperature varied from 30 °C to 55 °C during drying. The drying time in the solar greenhouse dryer was 1 day to dry cassumunar ginger from an initial moisture content of 90% (wb) to a final moisture content of 10% (wb), whereas it required 1 day of natural sun drying under similar conditions to reach a moisture content of 40% (wb). A system of partial differential equations describing heat and moisture transfer during drying of cassumunar ginger in the solar greenhouse dryer was developed and solved numerically using the finite difference method. Good agreement was found between experimental and simulated moisture contents.

Environmental and economic analysis of hybrid greenhouse solar dryer: A Review

Zero hunger is one of the goals out of 17 sustainable development goal set by United Nations for 2030. As the population is growing at a rapid rate so the demand of food will also increase. Solar dryers are considered as the sustainable solutions for conserving the food for longer duration. The enviro-economic analysis becomes necessary to check the impact of developed dryer on environment and its economic viability. This review article focuses on the environmental and economic analysis of hybrid greenhouse solar dryers. The dryers although operates using the solar energy but still in case of hybrid dryers some other devices are also used which emits CO2 and other non-environmental friendly gases during their use or disposal. The impact of a solar dryer on the environment is very low but still, it is necessary to check the impact. The economy is another factor that is kept in mind while developing the dryers. It is observed that the cost of dryer and its impact on environment increases with the increase in floor area of dryer. The hybrid dryers are usually costly due to use of various additional devices but gives better performance than passive and active dryers. The payback time of hybrid dryers are almost same as active dryers that is about 1-2 years, thus hybrid dryers can be developed commercially to get more profit. The parameters which are considered during environmental and economic analysis are discussed in the paper. The paper presents a way to carry out the environmental and economic analysis of hybrid dryers.

Analysis of recent developments in greenhouse dryer on various parameters- a review

In today’s world, the main focus is to reduce the dependency on fossil fuels for fulfilling the increasing energy demand. Burning of fossil fuels leads to emission of greenhouse gases that pollute the environment. Renewable energy sources such as wind energy, solar energy, etc. are sources of clean energy. Solar energy is present abundantly in most parts of the world and it can be utilized as prime source to meet the energy demand. Drying of various products such as fruits, crops, etc. requires energy in form of heat for removal of the moisture content to a certain limit so that the product can be preserved for longer period of time. Traditionally open sun drying is used for drying purpose but it has various shortcomings such as poor quality of dried product, large open space requirement, longer drying time, etc. To overcome these issues of open sun drying, a large variety of solar greenhouse dryer has been introduced. The main objective of this paper is to analyze the recent developments in greenhouse dryer keeping in mind the performance, economic and environmental aspects. The study in this review paper reveals the various advancements and their impact on the performance of greenhouse dryer. This review paper will help in addressing research gaps on critical areas of greenhouse dryer.

Experimental and CFD investigation of six shapes of solar greenhouse dryer in no load conditions to identify the ideal shape of dryer

Solar energy plays a vital role in improving the shelf of the agricultural product through drying, solar greenhouse drying is more optimal than using an open air drying, in this study selecting a ideal shape of greenhouse dryer among the other shapes is investigated. Six shapes of solar greenhouse dryers are designed in such a way that each dryer maintains the same volume of 30 ft3. The six shapes are Parabola, Quonset, Modified Quonset, Pyramid, Igloo and tropical. The inside temperature of greenhouse dryer is in the following order from maximum to minimum, Quonset, Tropical, Pyramid, Parabola, Modified Quonset and igloo during summer season. Quonset is capable of generating 64% more temperature when compared to atmosphere, whereas tropical generates 57%, pyramid generates 56%, parabola and modified Quonset generates 55% and igloo generates 53% more temperature when compared to atmosphere temperature during summer. Quonset shape generates 7% more temperature when compared to its rival tropical shape during summer and 5% more temperature during winter. The ideal shape of the solar greenhouse dryer is Quonset Shape, it generates a maximum of 72 DegC in summer and 66 DegC in winter.

Solar drying in the vineyard: a sustainable technology for the recovery of nutrients from winery organic waste.

The present study describes a pilot-scale experimental validation of a forced-convection greenhouse solar dryer, combined with a biofilter, for controlled atmospheric emissions. This set-up was applied to the dewatering of sewage sludge from a biological plant that treated process wastewater in a commercial Mediterranean winery. Experiments were performed after the harvest, from September onwards, during the peak generation of sludge. The average drying rate during the first 10 days of operation ranged from 1.17 to 2.24 kg m-2 d-1, depending on the measurement method, during which the water content of the sludge was reduced from 90% down to 67%. Biofiltration was quite inefficient against greenhouse gases (methane and dinitrous oxide), and direct emissions during the drying process were on average 57 g CO2-eq m-2 d-1. Ammonia and volatile organic compounds were removed with average efficiencies of 71% and 35%, but ammonia losses through volatilization represented less than 2% of the initial nitrogen content. The sludge was dried further during November, to the lowest possible water content of 14%. Both the intermediate and final sludge dried materials were characterized for their agronomical value as organic fertilizers.

Effect of drying temperature and drying method on drying rate and bioactive compounds in cassumunar ginger (Zingiber montanum)

In this study, influences of drying of cassumunar ginger (Zingiber montanum) slices using a hot air dryer at 40, 50, 60, 70, and 80 °C, a large-scale greenhouse solar dryer, and sun drying on drying kinetics, color, bioactive compounds, and antioxidant capacities were investigated. The Page model was adequate for describing the drying kinetics and increasing of the temperature accelerated the drying rate, therefore the drying time at 80 °C was shortest (1.5 h). The hot air drying effectively preserved curcumin content and color of the dried products. Drying at higher temperatures, however, resulted in losses of essential oil yield. In contrast, solar and sun drying significantly degraded curcumin and therefore adversely affected the color of dried products. Although, all conditions of drying resulted in volatile oil losses of 18–36 %, different drying conditions did not affect the obtained oil compositions. In addition, it was found that the dried sample from the hot air dryer and the greenhouse solar dryer exhibited slightly higher antioxidant capacities than those from sun drying.

Performance of a large-scale greenhouse solar dryer integrated with phase change material thermal storage system for drying of chili

ABSTRACT Large-scale greenhouse solar dryers have been used for drying various products and this type of dryer is usually equipped with LPG burner as auxiliary heater, which creates more operating cost. To overcome this problem, phase change material (PCM) thermal storage was proposed to substitute for the LPG burner. In this work, the performance of a large-scale greenhouse solar dryer integrated with a PCM as a latent heat storage for drying of chili was investigated. Experimental studies were conducted to compare the performance of this dryer with that of another large-scale greenhouse solar dryer without the PCM thermal storage and open sun drying. Chili with an initial moisture content of 74.7% (w.b.) was dried to a final moisture content of 10.0% (w.b.) in 2.5 days, 3.5 days, and 11 days using the solar dryer integrated with the PCM thermal storage, the solar dryer without the PCM thermal storage and the open sun drying, respectively. The performance of the solar dryer integrated with the PCM thermal storage was also evaluated using exergy analysis. The exergy efficiency of the drying room of the solar dryer integrated with the PCM thermal storage and the solar dryer without the PCM thermal storage for drying of chili was found to be 13.1% and 11.4%, respectively and the thermal storage helps to dry chili during adverse weather conditions. The results of exergy analysis implied that the exergy losses from the dryer with the PCM should be reduced.

Experimental conditions to identify the ideal shape of dryer investigation of six shapes of solar greenhouse dryer in no load

Solar energy plays a vital role in improving the shelf of the agricultural product through drying, solar greenhouse drying is more optimal than using an open air drying, in this study selecting a ideal shape of greenhouse dryer among the other shapes is investigated. Six shapes of solar greenhouse dryers are designed in such a way that each dryer maintains the same volume of 30 ft3. The six shapes are Parabola, Quonset, Modified Quonset, Pyramid, Igloo and tropical. The inside temperature of greenhouse dryer is in the following order from maximum to minimum, Quonset, Tropical, Pyramid, Parabola, Modified Quonset and igloo during summer season. Quonset is capable of generating 64% more temperature when compared to atmosphere, whereas tropical generates 57%, pyramid generates 56%, parabola and modified Quonset generates 55% and igloo generates 53% more temperature when compared to atmosphere temperature during summer. Quonset shape generates 7% more temperature when compared to its rival tropical shape during summer and 5% more temperature during winter. The ideal shape of the solar greenhouse dryer is Quonset Shape, it generates a maximum of 72 DegC in summer and 66 DegC in winter.

Thermal performance of the photovoltaic–ventilated mixed mode greenhouse solar dryer with automatic closed loop control for Ganoderma drying

The results of the thermal performance of the photovoltaic-ventilated mixed-mode greenhouse solar dryer have been investigated. A mixed-mode greenhouse solar dryer with automatic closed-loop control is used in the drying process. For the same solar radiation, four drying conditions have been conducted and compared with the open-sun traditional drying. It is found that the drying curves show only the falling rate period. The drying rate of the Ganoderma inside the greenhouse solar dryer is higher than that from the open sun traditional drying. The ventilated frequency and drying temperature have a significant effect on the evaporating moisture of the Ganoderma, which more favorable for drying, especially method II. The results obtained from this study can be used to design the system dryer practically shorten the drying time of the Ganoderma.

Numerical study of the greenhouse solar drying of olive mill wastewater under different conditions

The aim of this work is to develop thermal modeling of the olive mill wastewater drying process in a greenhouse solar dryer. A configuration was thus proposed and simulated using the commercial software COMSOL Multiphysics in order to solve the conservation equations governing our problem. The resulting simulations are used to evaluate the temperature, velocity, and vapor mass fraction distributions after hours of sunshine and to provide a quantification of the drying process. The influence of the greenhouse effect on the drying kinetics is highlighted by comparing to open sun-drying results. The effect of some greenhouse geometric characteristics and external meteorological conditions are studied.

Experimental Investigation of PCM Assisted Greenhouse Solar Dryer for Hibiscus Leaves

Experimental Investigation of PCM Assisted Greenhouse Solar Dryer for Hibiscus Leaves - written by Purusothaman M , Valarmathi T N , Matta Eswar Yadav published on 2020/03/07 download full article with reference data and citations

COSTS AND BENEFITS OF USING PARABOLIC GREENHOUSE SOLAR DRYERS FOR DRIED HERB PRODUCTS IN THAILAND

: Parabolic greenhouse solar dryers have been developed to overcome product quality and postharvest loss problems. It uses solar energy, a renewable source of energy. Due to their high investment costs, economic feasibility and the potential of carbon dioxide (CO2) mitigation were investigated. Owners and managers of 17 enterprises, producing several varieties of herb products, investing in different sizes of solar dryers and using various traditional drying methods before investing in solar dryers, were interviewed in depth to create a data set. The net present value (NPV), internal rate of return (IRR), payback period and CO2 mitigation were evaluated. The enterprises with annual production capacities higher than 1,200 kg or the annual revenues higher than solar dryer investment costs tended to have positive NPV indicating that the investments were attractive. Most enterprises showing CO2 mitigation higher than 130 tCO2e over 15 years had positive NPV. The annual production capacity, annual revenue and the amount of CO2 mitigation could be used to assess investing in greenhouse solar dryers.

A Comprehensive Review on Greenhouse Drying Technology

Drying is one of the most important unit operations for food preservation and storage. It is a energy intensive process and with the increase in the price and demand of electricity, renewable energy (solar) is proving its worth. Greenhouse dryers are low cost, easily constructible and can be utilised for invariably majority of agricultural commodities. The above attributes accounts for its high popularity in the Indian sub continents and Africa. An attempt has been made to generate a comprehensive review on the application, advances in construction, modelling, simulation and economics of the solar greenhouse dryers.

Drying kinetics of turmeric rhizomes and mathematical modeling

Drying kinetics of turmeric rhizomes (finger and mother rhizomes) was investigated by two drying methods namely direct sun drying and solar greenhouse drying with two different drying surfaces (black sheet over mud floor and directly on mud floor). The temperature and RH of ambient air and the air inside the solar greenhouse dryer varied from 31 to 47 oC and 55 to 16% respectively and 36.5 to 57 oC and 53 to 14%, respectively during the study period. The moisture content of boiled finger and mother rhizomes was 567 and 257% (db), respectively. Drying rate of turmeric rhizomes was higher (26.15 g of water/h/100 g of bone dry materials) in solar greenhouse dryer than the direct sun drying (23.64 g of water/h/100 g of bone dry materials). Among the drying surfaces, black sheet over mud floor recorded higher drying rate. Drying time of black sheet covered solar greenhouse dried turmeric finger and mother rhizomes were recorded about 52 and 68 h, respectively and reached an equilibrium moisture content of 7.39 and 10.95% (db), respectively. Six thin layer drying models namely Lewis, Page, Modified Page, Henderson-Pabis, Diffusion approximation and Two-term exponential were tested to identify the most appropriate model to describe drying kinetics of turmeric rhizomes. It was found that among the six drying models, Diffusion approximation and Page models are the best models to describe the drying characteristics of turmeric rhizomes.

Study of air movement and temperature distribution in a greenhouse used as a dryer

Sun drying is the oldest way to preserve but also to valorize and store surplus agricultural production. Nowadays, several types of dryers have been developed, but the solar greenhouse dryer is an ideal solution in our tropical countries because of its implicit and higher load capacity. The greenhouse climate depends on several factors, namely the outdoor climatic conditions (air temperature, wind speed, radiation, etc.) but also on the type of materials used to cover the greenhouse. The study was carried out on a parabolic greenhouse covered by a polyethylene film with a concrete base (absorber) which in turn is placed on the ground and will be tested under the climatic conditions of Dakar, Senegal. It is in this context of sustainable development that this work is carried out. The goal is to determine the distribution of temperatures and wind speeds in the greenhouse. The simulation was carried out using the three-dimensional computer fluid dynamics software (CFD). The turbulence method (k-ε) was used and to solve the radiation transfer equation (RTE) we introduce the discrete ordered method DO. We also add the “Solar Load Model” which gives the position of the sun and its radiations in relation to the layout of the greenhouse according to the date and time of the simulation. The simulation is carried out in a closed greenhouse and the results found can be used to improve the design and control of the greenhouse climate. Air temperatures and velocities simulation give an average of 325.95 K and 0.114 m/s respectively.

Development of the greenhouse solar dryer for germinated parboiled Thunya-Sirin glutinous rice dried

The objective of this work was to describe the development of greenhouse solar dryer for germinated parboiled Thunya-Sirin glutinous riced ried. Parameters studied were germinated parboiled Thunya-Sirin glutinous rice, drying temperatures at 40°C. The drying process was carried out until the final moisture content was below 8 % (dry basis, d.b.). The moisture ratio, the color difference (ΔE) and physical propertiesof the product were determined. The results revealed that the greenhouse solar dryer showed the drying time for 5 hr. The greenhouse solar dryer maintains color and nutrients of rice, this technique better prices, higher affordability level, better payback power of farmers. Therefore, drying germinated parboiled Thunya-Siring lutinous rice using greenhouse solar dryer is more suitable than unsanitary.

Performance Evaluation of a Solar Greenhouse Dryer at Different Bed Conditions Under Passive Mode

Greenhouse drying shows a significant role in the bulk level of drying. In the present setup, a greenhouse dryer operating under natural convection mode was designed and fabricated. The sensible heat storage concept was applied to the bed of the drying chamber. Four different beds, namely, gravel bed, ground bed, concrete bed, and black painted gravel bed was being selected for the comparative heat transfer analyses of the proposed setup. The maximum heat gain takes place at the black painted gravel bed conditions, i.e., 53%, while for concrete bed, gravel bed, and ground bed, it is 33%, 49%, and 29%, respectively. Hence, black painted gravel bed condition is strongly recommended for maximum heat storage. The proposed setup was used for drying of tomato flakes in black painted gravel bed condition. It has been found that the moisture content in the tomato flakes has been removed from 96% to 9.10% in 13 h. The average drying efficiency of the proposed greenhouse dryer is found to be 23.49%. The comparative analysis of the performance evaluation has been done with other investigators, and it was found that the drying rate of the proposed setup shows superior performance as compared with others. The design of the proposed greenhouse setup with black painted gravel bed condition is strongly recommended for small-scale industries and farmers.

A comparative study of drying kinetics and quality of Indian red chilli in solar hybrid greenhouse drying and open sun drying

Abstract This work reports efficient drying behavior of Indian red chilli dried in controlled greenhouse dryer under solar radiation in tropical summer conditions. A comparative study has been carried out on drying kinetics, the quality of red chilli in solar hybrid greenhouse dryer and open sun. Desirable moisture content (%) was achieved with rapid drying rate in active drying (18.67% in 9 h) compared to passive drying (24.24% in 12 h) and open sun (24.24% in 24 h) drying conditions. Further, FTIR analysis identified the presence of functional groups (Capsaicinoids and dihydrocapsaicinoids) of red chilli dried in solar hybrid greenhouse dryer.

Experimental study of a new mixed mode solar greenhouse drying system with and without thermal energy storage for pepper

Thermal energy storage is a great interest for solar dryer as the availability of solar resource is intermittent. In this paper, we present an experimental work on a new mixed mode solar greenhouse drying system with and without thermal energy storage unit by Phase Change Materiel (PCM). In fact, The experiments were carried out simultaneously and the focus area is to investigate the effect of paraffin wax as a PCM on drying efficiency of red pepper. The drying system consists of two solar greenhouses, a storage unit and two identical solar air heaters. The experimental results show that air temperature inside solar greenhouse with PCM is higher than other driers by about 7,5 °C during all night period. The relative humidity in the drying chamber with PCM is lower by about 18,6% than the ambient relative humidity after sunset. The moisture content has an effective reduction of 95% in 30 h for dryer with PCM, whereas it took 55 h in dryer without PCM and 75 h in open sun. Ten thin-layer mathematical models were fitted to the drying data to select a suitable drying equation. The Midili et al. and the Two-term were found to be the best models respectively, in solar greenhouse with PCM, for both solar greenhouse without PCM and open sun dryer. The use of PCM in solar greenhouse dryer was found to be a promising alternative to enhance the drying process efficiency.

Hybrid Greenhouse Dryer for Paddy

A forced convection greenhouse dryer was developed and used for drying of freshly harvested paddy. The solar greenhouse dryer of size 4.47 × 2.13 m with 2.59 m central height was constructed and covered with 6 mm polycarbonates sheet. Photovoltaic power driven direct current fans were used to provide forced ventilation. Freshly harvested paddy was dried at 50, 100 and 150 mm bed thickness in the hybrid greenhouse dryer and open sun drying during kharif and rabi seasons of 2016. The kharif harvested paddy was dried from 25.3 % to 12.0 % (w.b.) moisture content at 100 mm bed thickness within 21 h, 28 h of drying in the hybrid greenhouse dryer and open sun drying, respectively. Highest drying rates were 1.54 kg.h-1 and 1.35 kg.h-1 in greenhouse dryer and open sun drying, respectively. During rabi season, paddy was dried from 22.8 % to 12.0 % (w.b.) moisture content within 19 h and 25 h with highest drying rates of 1.65 kg.h-1 and 0.97 kg.h-1, respectively, in the hybrid greenhouse dryer and open sun drying. Thermal efficiency of the greenhouse dryer was 28.15 % and 22.15 %, and pickup efficiency was 15.49 % and 14.88 % during kharif and rabi seasons, respectively.