EVALUATING THE PERFORMANCE O F SOLAR TOBACCO BARN Engr Amad Ullah Khan. Engr Saira Bano. Dr Saner Noor, Dr Imran. Department Of Chemical Engineering, University of Engineering and Technology, Peshawar. Correspondence Author: imran. ahmad@rrwfuel edu.pk Abstract: The equipment we have fabricated has many advantages by saving a large amount of the fuels but it still have some difficulties. By removing these defects from the equipment we can increase its efficiency as well as the workability of the equipment. We have performed two experiments on our equipments to get the cured product from it. In the first experiment we use the solar energy only while in second experiment we use the dual fuel system that consist on solar as main fuel while the coal is used as the secondary fuel at night time or in cloudy weather. From these experiments the conclusions we have taken havebeen discussed in the previous chapter. But in order to improve its efficiency and workability we have some suggestions and conclusions that will increase the working efficiency and energy conservations up to a great amount. This not only save the money buy saving wood but also help inagreat deal in stoppingthedeforestationinPakistanplus also will be help in reduction of global warming. Keywords: Tobacco Barn, Solar Energy, Performance, Conventional Solar Cells

1. Introduction

and heating.

The problem was brought to the Department of Chemical engineering by the Chairman, Major (Retd) Sahibzada Khalid, Chairman, Pakistan Tobbaco Board,In which they wished to help the common grower of tobacco.

Solar collectors trap the sun's rays to produce heat. Most solar collectors are boxes, frames, or rooms that contain these parts: • •

2. Objective The Solar tobacco Curing barn was designed to reduce the deforestation that take place in Pakistan. Every year million of trees are cut just for curing of tobacco. Which not only contribute in Global Warming but also increases the Production cost. Moreover in wood curing barns the Quality of tobacco is divided in several grades effecting the net profit of the farmers. This problem is almost solved by the solar curing barn, which gives consistent quality of Agrade tobacco. 3. Solar Heating The sun gives us energy in two forms: light and heat. For many years, people have been using the sun's energy to make their homes brighter and warmer. Today, we use special Equipment and specially designed homes to capture solar energy for lighting

NFC-IEFR Journal of Engineering & Scientific Research

• •

Clear covers that let in solar energy; Dark surfaces inside, called absorber plates, that soaks up heat; Insulation materials to prevent heat from escaping; and Vents or pipes that carry the heated air or liquid from inside the collector to where it can be used.

Many clear material scan be used as covers for solar collectors, but glass is the most. The sun gives us energy in two forms: light and heat. For many years, people have been using the sun's energy to make their homes brighter and warmer. Today, we use special Equipment and specially designed homes to capture solar energy for lighting and heating. Solar collectors come in many shapes and sizes. A home that uses a room or another part of the building as a solar collector is called a passive solar home. In many cases, passive solar homes use rooms called sunspaces to capture solar energy directly. A



Evaluating the Performance of Solar Tobacco Barn

sunspace can be either a room that faces south or a small structure attached to the south side of a house. Sunspaces have a large amount of glass and large areas of dark stone or concrete walls and floors. These materials make up the thermal mass, which absorbs heat. Vents placed against the back wall of a sunspace allow heated air to move naturally into nearby rooms. At the same time, cooler air from nearby rooms can move into the sunspaces. (Walker, August 1994) Metal frame

Vert5 o' 5 , i p e

s

Fig. 1: Solar Panel (Walker, August 1994)

Flat-plate collectors look like large, flat boxes with glass covers and dark-colored metal plates inside that absorb heat. Flat-plate collectors are usually placed on roofs of houses where no trees or tall buildings will block the sun's rays. Air or a liquid, such as water, flows through flat-plate collectors and is warmed by the heat stored in the absorber plates. The air or water heated inside the solar collectors then and oil shrink, these fuels become more expensive. I f more people began using solar heating systems, fossil fuels such as oil and gas would become less expensive and last longer. Burning natural gas and oil in our heating systems also causes air pollution. Even electric water and space heaters cause air pollution indirectly, because coal and natural gas are burned to produce electricity in large power plants. So i f more people used solar energy to heat the air and water in their homes, our environment would be cleaner. (Walker, August 1994)

used a solar thermal collector box (a device that absorbs sunlight to collect heat) to cook food during an expedition to Africa. Today, people use the sun's energy for lots of things. (Leik.C, July 1994) Solar energy is truly the new wave of the future. Though the use of solar power has been around for many years, the need and demand for it is growing steadily every day as the need for conserving the most popular energy reserves are being stressed more and more. We are simply using too much electrical energy and doing so in a way that is harming our environment. As a result, we are forcing the need to seek out alternative, non-harmful means of energy, thus, the increase in solar energy use and technological advancements of it. Solar energy is becoming more popular being used in everything from watches to building infrastructures. Solar energy is even being used to fuel automobiles and will most assuredly be a large part of the energy we will use going into the future. There are many advancements currently being made on the solar energy technology that is already working, advancements that w i l l allow solar driven technologies to run even longer on solar energy than everbefore. (Leik.C, July 1994). Solar energy is free, and its supplies are unlimited. Using solar energy produces no air or water pollution but does have some indirect impacts on the environment. For example, manufacturing the photovoltaic cells used to convert sunlight into electricity consumes silicon and produces some waste products. In addition, large solar thermal farms can also harm desert ecosystems i f not properly managed. Thermal insulation limits the collector's thermal loss and increases its efficiency. The thickness of the mineral wool insulation is between 2 and 6 cm depending on the model (Graven, Nov 18,2007). 5. Types of Solar Curing Tobacco Barns. a) b)

4. Solar Tobacco Barn The sun has produced energy for billions of years. Solar energy is the sun's rays (solar radiation) that reach the earth. Solar energy can be converted into other forms of energy, such as heat and electricity. In the 1830s, the British astronomer John Herschel NFC-IEFR Journal of Engineering & Scientific Research

Natural Convection Solar curing tobacco barn. Force Circulation Solar curing Tobacco Barn. A brief discussion on the above types of Solar Curing Tobacco Barns is given below.

5.1 Natural Convection Solar curing tobacco barn. Natural convection Solar Curing Tobacco Barn is the most suitable among its types as the power consumption requirement is negligible in it. The



Evaluating the Performance of Solar Tobacco Barn

aeration in side the solar Curing barn of this type is accomplished naturally but the area requirement for the Pilot Plant is more depending on the availability of the land. As Pakistan is facing energy crisis giving it the benefits of utilization of this type. The Solar Collector is installed according to the solar angle of that area at the bottom of the wall opposite to North side of the location. Natural Circulation Solar Tobacco barn can save more than 70% of the Production cost as compared with the Convectional Wood Curing Tobacco Barn. The experimental data shown in this conference is based on Natural Convection Solar Tobacco Barn as the proto type it is designed by the Department of Chemical Engineering, University of Engineering and Technology, Peshawar.

compared to convectional Wood Curing tobacco barn.

Fig. 3: Forced Circulation Solar Curing Barn (Walker, August 1994)

6. Design of the Equipment. From the literature survey about the tobacco barn and that of the solar system we design a new type of the solar tobacco barn in which we keep in mind the requirements of solar system and that of the tobacco Curing requirements in which Temperature and humidity is the key factor. As the system is purely based on solar system so we will stress on the absorption of solar energy. For solar absorption we have two types of material used for solar absorption.

Real Image o f Solar Barn

Design Parameters

• •

Fig. 2: Natural Convection Solar Curing Tobacco Barn.

5.2 Force Circulation Solar Curing Tobacco Barn. Force circulation Tobacco barn requires a little of Power Consumption as compared with the Natural Convection Tobacco barn as the collector is installed on the top of Solar Curing Tobacco barn. Force Circulation Tobacco Barns is to be constructed in those areas where the land is limited. As the hot air loses its density thus accumulate at the top inside the Force Circulation Solar Curing Tobacco Barn. This circulation requires ducts and Fans to circulate the hot air in side the Force Circulation solar Curing Tobacco Barn thus increases the production cost as compared with Natural Circulation Solar Curing tobacco barn. On the Request of Chairman, Major (Retd) Sahibzada Khalid we constructed the Pilot Plant in Khan Gari, Mardan at the Tobacco Research institute of Pakistan Tobbaco board. The Force Circulation Tobbaco Barn gives 50% of Saving as N F C - I E F R Journal of Engineering & Scientific Research

Solar absorber. Black body absorption through the glass refractor.

We will explain both of the above mentioned systems for solar energy. 7. Solar Absorbers. In solar absorption we use a flatter surface used for solar absorption from the sun. The flat surface absorbs the solar energy and uses it for the space heating. In our project our main objective is the space heating up to the required temperature. For solar absorber we have found two types of the solar absorbers that absorb most of the solar energy from the sun. These materials are, • • •



Tinox Material Schwartz Chrome Black body

Evaluating the Performance of Solar Tobacco Barn

These materials have the maximum absorption capacity. Now we are going to discuss both of the materials. 7.1 Tinox The multi-layer structure of the Tinox energy coatings is Designed to serve as a highly selective absorber surface, which is optimized to transform nearly all incoming solar radiation into heat and to prevent the heat generated from being lost as infrared radiation as in the case of a black coating. Over 90% of the incoming solar radiation energy can be used as heat. The Tinox energy coatings are available on copper and aluminum substrates.

due to the surface clearance. It can absorb 95% of the total sun rays and allow emitting 15% of the total absorbed heat of the sun. Athin bonding layer serves as an adhesion layer and diffusion barrier. In the complex absorber layer the solar radiation is being transformed into heat. Additionally an antireflection and protective layer made of quartz glass is deposited on the absorber layer. (Tinox industry, 2007)

80% Fig. 5: BlackChrome SolarAbsorber (Tinox industry, 2007)

90% Fig. 4: Tinox Solar Absorber Surface (Tinoxindustry, 2007)

In order to ensure a low emission in the far infrared Wavelength, the aluminum substrate carries an additional reflective layer for that wavelength range, not necessary on copper. Athin bonding layer serves as an adhesion layer and diffusion barrier. In the complex absorber layer the solar radiation is being transformed into heat. Additionally an antireflection and protective layer made of quartz glass is deposited on the absorber layer. (Tinox industry, 2007). 7.2 Schwartz Chrome This is also an absorbing material used instead of the Tinox material which less efficient then that of the Tinox but of higher efficiency then that of the black body. 5% of the total solar energy is reflected back N F C - I E F R Journal of Engineering & Scientific Research

But both the above absorbers are very costly and unavailable in Pakistan, these material can be imported from other countries. Both products perform excellent thermal characteristics and durability and are subject to an ongoing product development and an optimization program. The high adhesion of the absorbing layers, allows bending to a small radius without cracking or adhesion loss. The underside of Tinox products is pure copper, ideal for joining technologies and with copper's natural resistance to corrosion. (Tinox industry, 2007) Discussing the above solar absorber we designed another solar system that have the absorption capacity a little less than that of the Tinox and Schwartz Chrome but that can fulfill our requirements up to more extent. It will be a fix system designed keeping in view the requirements of the farmer at the location of farmhouses. (Tinox industry, 2007) 7.3 Black Body Absorption through the Glass Refractor: In this type of solar absorber the whole absorption is

Evaluating the Performance of Solar Tobacco Barn

done through the black body. The solar rays are refracted through the glass plate. The inside shell of the system is painted black color. The whole design of our system is discussed below, 8. Absorption of the black body Black body absorbs heat from the sun up to 95% from which 5% of the solar heat is reflected back to the atmosphere. The absorbed 95% heat remain in the system but the system emit about 45% of the total absorbed heat to the atmosphere and 50% Of the heat remain inside the system which is used for the space heating. The fig shows the whole detail of the black body absorber.

9.1 Walls Structure The walls are composed of two metal sheets of tin. Both of the sheets are separated from each other by giving an air gape as insulation. In order to include the air gape first we select the material of construction for the wall. 9.2 Side Walls The material that we have used for the wall construction is made of tin sheet. Each wall is composed of two sheets of 3 ft (0.914m) cube that are separated by 1.25in (33mm) cubical pipe. Both the sheets are welded on both sides of the cubic pipe. The welding is done and then using the grinder for finishing of the welding. We have three walls of this that are the following; • • •

Left side wall Right side wall Bottom surface

All the walls have the same gapes and sides dimensions. All the three walls are connected to each other and the third wall has different dimensions and angles. The wall structure of the above mentioned walls are given below;

50%

3ft Or 0.914m

Fig. 6: Black Body SolarAbsorber (Tinox industry, 2007)

Based on the above black body radiation absorption capacity and space heating capability we have designed a tobacco barn that will operate on solar energy instead of the fuel which will provide more and more heat and will save the cost o fuel. 9. Design of the Solar Tobacco Barn Our suggested designed is based on a lab scale equipment which is a small scale unit of dimensions 3 * 3 ft cube and the back side height is 5 ft and the width is 3 ft.

Fig. 7: Side wall

9.3 Backside wall All the dimensions and angles will be explained gradually as they are discussed at their position.

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The back side wall has also the same gape in between the two tin sheets by inserting the 1.25in square pipe and the bottom side of the wall is 3ft while the other

Evaluating the Performance of Solar Tobacco Barn

is 5 ft. the upper 3ft area is cut o each of the 6in in order to give the tilt angels to the glass surface of absorption. The angels are of 14° and 76°. (Pidwirny, M.2006)

just mount the solar collector flush against the roof surface. The added trouble of adjusting the collector to a precise angle is not warranted as it will not result in a great improvement in efficiency.

The angels that are taken from the height of the 3ft where these angels are specified according to the international standards for solar system. The dimensions that are selected are for the construction of the laboratory scale solar equipment. The over all dimensions are given on the next page with the labels.

Generally in the summer heating will not be required, in contrast cooling is. Unfortunately, at present solar cooling for domestic applications is not yet economically viable, so what to do with the additional heat? I f you have a swimming pool or spa, the excess heat can be used to supplement heating. Turning off the pump and letting the collector stagnate is not ideal as high pressure and temps, and large volumes of vented steam may result. I f you do not have an additional means of using the excess heat, then adjusting the angle of the collector can help to reduce summer heat output. As can be seen by the diagram above, the sun is low in the sky during the winter and high in the summer. Solar smart house designs will take advantage of this by having big North or South (depending on your location) facing windows allowing maximum absorption of winter sun, with large eves or veranda to block out the summer sun.

(a) Schematic O f The Back Wall

(b) Actual View

Fig. 8: Back Side Wall

9.4 Solar Absorption Surface In the front the inclination is given according to the international solar absorber angle. The glass surface used for the solar absorption was about 8mm. this glass surface used was in front wall front inclination and side tilts surfaces to absorb more and more solar rays from sun. The angles used were according to t hollowing statement; "Naturally we want the collector to receive the maximum amount of sunlight each day and throughout the year. As a general rule i f you are in the Northern Hemisphere then the collector should face south and i f you are in the Southern Hemisphere then the collector should face north. The angle at which you mount the collector should roughly correspond to the latitude of your location." (Booth B Hall, 27¬ 28th May 2009) You do not have to be too careful about mounting the collector at the exact angle suggested. I f your roof angle is within 10°+/- of your desired angle you can NFC-IEFR Journal of Engineering & Scientific Research

By increasing the vertical angle of the collector by about 20° more the location's latitude (i.e.60° instead of 40°), greater winter performance will be experienced. This is because the collector is "facing" the sun (perpendicular - longitudinal angle). Due to the higher location of the sun in the sky during the summer, the collector will be around 40° from perpendicular and as such heat output will be reduced as the collector is not fully "facing" the sun. This simple solution alone can reduce peak summer output considerably, thus reducing problems associated with excessive summer heat production. South

Dec

JUIIQ

North

Dec,

1

«

J

Fig. 9: Deciding the Direction and Angle of Installation

Evaluating the Performance of Solar Tobacco Barn

In Peshawar the latitude of the sun is about 34.8°which have been implemented in this design to absorb more n more solar rays. In the tilt side due to less area the specified angles were not given because of fewer surfaces and are. But the frontal inclination angle of absorber is given according to the standard. The front wall is also made of the glass to increase the absorbing area for the solar. For the absorption of maximum solar rays the total area of absorption is about 1.98m . Due to this great are for the absorption of the solar heat from the sun to provide heat to more and more area. The total black body absorption area is 3.9 m . For the absorption we have provided the glass which will keep the inside environment of the system from the adverse effect of the out side environment. The glass wall will also reflect the solar rays to the base of the barn to absorb more and more heat from the sun to heat the inner area and make it favorable for the curing of tobacco by producing the temperature up to the required value. 2

n2 is index of refraction of air nl2 is relative index of refraction of glass and air. Here the denser medium is the glass and the rare medium is the air. The incident ray enter to the denser medium from the rare medium and refracted from the denser medium to the rare medium. During this entrance and refraction of the rays the net change in the path of the solar ray will b zero and the out put value will be the same as it is coming from the sun (Dock.R, 1968).

2

9.5 Glass Surface The glass surface we are using having the thickness of about 8mm and have the refractive index of about 1.78. The glass having this much high thickness has been adopted on two bases; • •

To be safe form breaking To give high refractive index

Due to its great thickness it is very hard and provides a protective shield to the inner environment of the system. In the refraction of the solar system Refraction is bending of a light beam as it passes from one material into another. Generally: when light passes from a medium (material) of higher density to the one of lower it bends off the normal (the perpendicular to the surface it strikes) and when it passes from medium of lower density into the one of higher it bends to the normal. The incoming ray is called incident ray and the angle it makes with the normal is called the angle of incidence. Ray after bending is called refracted ray and the angle it makes with the normal is called the angle of refraction. _nl_

sin(r)

-

n2

_

n

1

m

9

i

Where: i is the angle of incidence. n l is index of refraction of glass N F C - I E F R Journal of Engineering & Scientific Research

(a) Refraction through Glass

(b) Actual View

Fig. 10: Glass Medium

9.6 Internal Piping System The piping system has been adopted for the use of secondary fuel system that is the passage of the hot gases from produced from the burning of fuel (coal). The need of using the secondary fuel has been felt in case of less absorption from the sun due to cloudy weather or at the night time when the temperature drop is high due to great loss from the walls the loss of heat to surrounding then we use the secondary fuel system. We use the secondary fuel system for the process to achieve the required temperature. The pipe selected for the system has the diameter of about 0.07m and the material of construction of the pipe is tin sheet. The total length of the pipe that have been circulated inside the barn is about 7.93m by giving it two turns to emit more and more heat from the gases that are produced by burning of coal and a suction fan has been installed on the top of the chimney to suck the hot gases by its induced draft effect of the fan.

Evaluating the Performance of Solar Tobacco Barn

INDUCED DRAUGHT FAN

Fig. 11: Hot Gases Circulation Pipe

The pipe inside the system has also been painted black on its outer surface in order to absorb much solar energy inside the system. The hot gases pipe has been provided the support from all sides to avoid any potential damage caused by high temperature of the gases or by the solar system. At the inlet of the pipe the coal is burned in a mud pot above which it is dumped by the tin sheet to avoid the escape of ht gases from the burning coal and all the gases produced are sucked through the pipe and passed in order to emit more heat to the inside system environment. The chimney has been built a little high in order to exhaust the gases at a high position to avoid its harmful effect on human and pollution production from these gases. The inlet and exit gas pipes are made on the forcing of the gases by using the induced draught an at the outlet chimney of the pipe. The inlet and outlet pipe structure are given as below.

Fig. 12: Exhaust Chimney /Fig. 13: Pipe inside the System

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Fig. 14: Gas Pipe Inlet and Exhaust

The over all heat transfer calculation for the tin pipe was not done because of the complexity of these calculations. The heat transfer coefficient of the tin sheet that have been calculated which have the value of h = 23 88.6 j / m .K. (Gary Powers and Matt Cline, March 24,2000) 2

9.7 Exhaust Fans The exhaust fan is used for the removal of moisture content from the inside system and also used as a temperature stabilizer for the inner system. It controls the humidity level inside the system by constantly removing the moisture from the system. This moisture has been produced by the evaporation of the moisture from leaves. The increase in moisture content also effect the curing rate of the leaves. In black body absorption the temperature of the inside system temperature some time exceed the required limit of the curing for that purpose we also use the exhaust fan to control these parameters. The exhaust fan has been installed in the centre of the glass wall at the front wall and provided the necessary electric connection for the operation The above discussed fan was used for the inside temperature and humidity control. Another exhaust fan that is used as an induced draught fan working for the suction of hot gases from the coal burning at the end of the piping system that is used as a secondary fuel system..

Evaluating the Performance of Solar Tobacco Barn

GLASS WALL

a) Actual View

(b) Schematic View

Fig. 15: Exhaustfan

This fan is also an exhaust fan but the operation is different from above. The shape is like below given;

these wet bulb and dry bulb temperature values we can find humidity, enthalpy, relative humidity, specific volume, humid ratio etc by using the software of psychometric chart calculator. Beside these we have also installed two thermometers to find the solar absorption rate and also the heat transfer from the coal pipe to the environment outside of the system. The total numbers of thermometer are about six, here four thermometers are used inside and two thermometers are used outside.

Fig. 17: Measuring Devices inside the Systt Fig. 16: Exhaust Fan as Induced Draft Fan

9.8Measurements Devices In this system he temperature measurement and the humidity measurement are very important terms. Because we are controlling our process based on these parameters. The process of curing consists of several stages, in each stage the temperature and humidity are changing gradually. For this purpose we need two sets of two devices; • •

Thermometer Hygrometer

The outside thermometers are attached on back side of the barn showing the dry and wet bulb temperature of the environment. 9.9 Leaf Racks

But we did not use the hygrometer. Instead of hygrometer we use two types of temperature measurement the one is dry bulb temperature while the other one was the wet bulb temperature. In dry bulb temperature the measurement was the common thermometer measurement. In wet bulb temperature the bulb of the thermometer was wrapped with a soaked cotton plug and the measurement of temperature by that thermometer is called the wet bulb temperature. In the whole process the dry and wet bulb temperature measurement was done inside the system and outside of the system to find the difference of the system with the environment. From N F C - I E F R Journal of Engineering & Scientific Research

The inside thermometer arrangement is such that two are hanged with the pipe showing the wet bulb and dry bulb temperature of the system, one is attached on the pipe surface for pipe heat transfer and the fourth one is attached with the side wall to show us the heat transfer from solar absorption of the black body.

(

Inside the system for charging the tobacco leaf we have also made two racks each of them have the length of about 0.95m and having five points to hang the tobacco leaf for curing. The racks are consisting on holes on one tin strip and nails on the other tin strip. Both the strips are gathered with the help of the moving joints that can rotate through a certain fix point. At the end of one strip a nut is welded while on the other end a hole is cord, which is acting to be the nut is inserted and on the other side a bolt is fixed in the threads of the nut. Each of the rack can hang 10¬ 15 leaves in it. In our system two of the racks can be accommodated and in experimental stage we hanged about 20 leaves in it. The racks are as follows;

Evaluating the Performance of Solar Tobacco Barn

^

J

10.1 Curing Process

1

• • • • • (a) Actual Racks

(b) Schematic of the Leaf Racks

Fig. 18: Leaf Racks

9.10 Calculation Software For the calculation of the humidity, enthalpy, relative humidity, sp.volume, humidity ratio we need software that give us the calculation from the psychrometric chart. For this purpose we have software that we have downloaded from the internet named as Psycalc98 that is used for the calculation of the above values from the psychrometric chart. For this software we need only two parameter that are wet and dry bulb temperature. The calculations through this software give the different values that are mentioned in the chapter # 04. 9.11 Wheels As our designed system is experimental equipment and we have designed it on a lab scale unit so we have installed wheels to move it from one place to the other. Four wheels are installed at the four corners of the barn to support and move it. All the above discussion was about the designing and fabrication of the solar tobacco barn that have the standard angles and specification of the dimension is mentioned along with their structure photograph. After the fabrication the next step is the experimental work on the fabricated barn to get the analytical work done over the system to find its workability and effectiveness for the lab scale unit as well as for the large scale implementation for the saving of a large amount o the useful fuel. 10. Experimental Work Before starting the experimental first we have to know about the stages of the curing process. There are five stages for the curing of tobacco. These stages are as follows; N F C - I E F R Journal of Engineering & Scientific Research

Coloring (yellowing) Wilting Leaf drying (color setting) Stem drying (killing out) Conditioning

These are briefly discussed step by step below; (Devilliar.R, 1981) 10.2 Coloring (Yellowing) (Duration 40-50 hrs) The ripe tobacco leaf is a living biological system, which contain 80-90% water along with numerous biochemical compounds cell tissue etc. During the entire coloring phase, the leaf must remains alive retains high percentage of its initial moisture (over 75%) to permits the necessary chemical changes to occur satisfactory and gives the leave the desired yellow orange color and a mild sweet and less irritating smoke. So the coloring phase must last long enough to give the leaf the desired color and characteristics. It must not be shortened, as a green leaf is harsh, bitter and totally undesired for smoking. We usually start coloring advancing from environment's dry bulb temperature, temperature up to 35-36C in a high humidity (round 85-90% relative humidity). Environment (W.B 1C-2C less than D.B).(Devilliar.R, 1981) 10.3 Wilting (Duration 12-24 hrs) As soon as leaves have turned yellow, the D.B temperature is allowed to raise to about 38-40C. at less humid environment (around 75% relative humidity) so some drying now starts during the final coloring of the few remaining green spot on leaves in the barn. We keep these conditions till, •

•

We get full colored (all the leaf yellow only midrib and veins greenish tinge) and the leaf is welted. By this stage he leaf should be correctly colored and should have last about 25-30% moisture. (Devilliar.R, 1981)

Evaluating the Performance of Solar Tobacco Barn

10.4 Leaf drying (Color Setting) (Duration 30-40 hrs) Leaf drying is the most critical period of the cure and must be well controlled so that it is constant for the best results during the whole stage moisture removal must keep up with temperature increase some biological activity must still continue, to complete the desirable reactions necessary for good quality. This is particularly important mainly in leaf grown under stress conditions because it tends to be higher in starch and therefore will benefit from slow drying. In addition stress tobacco does not appear to release moisture easily and any attempt to dry this type of tobacco too fast affect quality.

• •

through the tobacco Let dry bulb temperature drop below D.B 45C preferably at 40C. Connect your water line to the sprayers and open water valves.

When proper condition is secured stop the fan and let the temperature drop to outside temperature before removing tobacco from the barn. Before starting the experimental work on the barn we have fabricated we run the equipment on empty basis to find some temperature measurement to know the workability and temperature achievement. We have performed three experiments on our solar tobacco barn these experiments are as follows;

It is there for important to ensure that: • • •

Temperature are not increased too rapidly Moisture removal keeps up with temperature increases. Ventilation is not too great in the early stages of drying, particularly in the heavier bodies' middle and upper reaping.

At this stage i f tobacco gets too hot with much water in it will result browning scalding, sponging, and slickness appearance. In order to prevent the above undesirable changes, leaf tissue must dry to a safe level before we raise temperature over 50-55C and proceed to stem drying phase. Thus for safety the wet bulb temperature should never be allowed to exceed 39-40 C until the leaf lamina is dry. We keep leafdrying conditions till all leaves in the barn are dry (onlymidrib still wet). (Devilliar.R, 1981) 10.5 Stem drying (Killing Out) (Duration 30-40 hrs) The only purpose of the stem drying phase is to assure safe tobacco storage by removing the leaf moisture from the midrib as the rest of the leaf is dry by now. The D.B temperature must not advance fast and must not exceed 70-72C to avoid reddening of the leaves, sugar caramelization and weight loss. (Devilliar.R, 1981) 10.6 Conditioning (Duration 4-8 hrs) As soon as the stems are completely dry then; •

Keeps the fan running to circulate the air

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• • •

Empty run experiment on solar energy Tobacco curing by solar energy only Curing by using the solar energy, and coal as secondary fuel

The experimental data obtained from these experiments are as given on the next page. (Devilliar.R, 1981) Efficiency of the equipment can be calculated by the ratio of the temperature inside the equipment with the outside environment temperature.

1

(dry) ill

~

1

(wet) ill

Efficiency = T A

T (dry) out

A

(wet) out

ll.Analysis#l 11.1 Empty Run on Solar Energy The empty run analysis was performed on the equipment in order to check its workability and its temperature achievement. This experiment was started on Thursday 7 May 2009 and was ended on Saturday 9 May 2009 by taking the reading of 48hrs. These reading were taken on keeping an interval of lhr. During this analysis we have measured the wet and dry bulb temperatures inside the equipment as well as of the outside environment. The solar absorption was also measured from the th

th

Evaluating the Performance of Solar Tobacco Barn

surface of the wall and that from the pipe surface thermometer to find that how much solar energy we have got from the sun. After getting these values then we find the values of relative humidity, humidity, specific volume and that of the enthalpy by using the software using that is bases on the psychrometric chart which calculate the above values by psycalc98 software. After calculating the above values different graphs has been drawn from the calculated values as well s the measured values. The data sheet obtained from the experiment is given on the next page;

System % am.

Graph 1: Time Verses Re I.Humidity for system as well as for Environment

Comments: This graph show that the rel. humidity does not change appreciably with temperature because of the absence of the leaves but due to temperature the inside environment is hot so the internal humidity is greater then the outer atmosphere the rise and fall of environment Rel.Humidity due to change in the environment temperature. It remains relatively same for the full experiment.

System Enthilpy

[hrsj

Graph 2: Time Verses Enthalpy for system as well as for Environment

Fig. 19: TestRun oj'Solar Tobacco Barn withoutFeed

N F C - I E F R Journal of Engineering & Scientific Research

Comments: This graph shows that due to rise in humidity their will be an appreciably change will occur in the Enthalpy of the system. The environmental graph shows us about variation of the enthalpy with temperature and change in the Rel.Humidity of the environment that is less then that of the inside environment.

Evaluating the Performance of Solar Tobacco Barn

D.Z

0.15

System

Humid

0.1 Envrprmsnt

ODB

A

ID

2d

32

\

Comments: This graph shows the over all behavior of the rel. humidity with the change in the temperature. It shows that the relative humidity increase relatively at constant temperature but the humidity remain constant with rise in temperature and then the humidity will decrease with decease in temperature at the final step.

d.D

Tin*

Dim 300

Graph 3: Time Verses Humid Ratio for system as well as for Environment

Comments: The graph tells that the humid ratio will increase with increase in the inside temperature and this humid ratio also increase with increase in the humidity and that with the rise in the temperature but will not fall as the rel. humidity fall. This shows the change in the change f the humid ratio with change in the rel. humidity but it is not as high as in the inside system.

Enthalpy 200

10

20

30

40

EC

BO

70

SO

90

T«niperatLire(P6£ C )

Graph 6: Temperature Verses Enthalpyfor system

Comments: The enthalpy of the system will initially rise with temperature appreciably but fall abruptly at constant temperature and the decreasing in temperature.

Humidity R»Uo

(hri) 30

Graph 4: Time Verses Efficiencyfor system

Comments: This graph tells us that the efficiency of the system varies from maximum to minimum due to the sun rise and sun set .and the solar absorption of the system

40

60

60

TO

90 70 T t r i m * r a t ur« (d*g.C) eg SO AO

30 20 10

T*mp*rsture[D«a C)

Graph 5: Temperature VersesRel.Humidityfor system N F C - I E F R Journal of Engineering & Scientific Research

100

Graph 7: Temperature Verses HumidRatiofor system

8Q

Humidity a

90

Comments: The humidity ratio also increase with rise in enthalpy of the inside system. But the over all behavior of the humidity ratio with temperature is as above in the graphs. 100

*K>R»I.

80

TemperetureCDeg C ]

Tim*



Temperature (d*g.C) 80 URll.

EO

Humidity- BO

40 30

- f\

'J

/

f^~^\

)

L

f ~ ^-i

J

\

/

r~~^

i / L f

\ _ y

(

20 10 i 12

i 24

• 36 Tim*

Temparnburs^Deg C)

Graph 12.5: Temperature Verses Rel.Humidityfor system NFC-IEFR Journal of Engineering & Scientific Research

• 4B

i GO

i 72

i 84

• SB

(hrs)

Graph 12.8: Time Verses Temperaturefor system

•

108

i 120

Evaluating the Performance of Solar Tobacco Barn

Comments: This graph shows that the temperature of the inside system will vary by the rise and fall of sun. At day time the absorption will be maximum while at nigh time it will get no absorption. Analysis # 3

The equipment was cleaned and maintained for the new experiment. In this experiment the total amount of fuel used was about 5.5kg for the whole curing process. And the coal process saved the total of 2 kg of coal that is used at the time after the sunset. The data obtained from this experiment are listed on the next page;

11.3 Tobacco Curing Using the Solar Energy as Main Fuel And The Coal as Secondary Fuel In the third experiment the fuel used were the solar energy as the main source of energy and the coal as secondary fuel. When the temperature inside the system was turned to decrease then the coal is used as a secondary fuel to keep the temperature at our required level until we get the solar energy at morning. By using coal as secondary fuel the coal is burned in an open pot and ignited fire and in the above chimney the induced draught fan was turned on to suck the hot gases produced by the burning of coal and circulate them inside the system and to get the required temperature of the system. The leaves were charged inside the system in the racks. In this experiment 15 leaves were charged inside the system and the experiment was started on 25 May 2009 and the experiment ends on 29 May 2009. In this experiment the reading were taken with the interval of the 30minutes and the readings were taken 24 hr a day. th

th

Humidity

12

24

36 Tln

AB

72

BO

B4

86

IBS

T30

" (hrsl

Graph 13.1: Time Verses Rel.Humidityfor system aswellasfor Environment

Comments: This graph shows that the temperature control is achieved so the change in the rel. humidity will change uniformly from star step to the end of the curing process. This graph shows the rel. humidity of the environment. JOO

System MO Enthalpy

200

100

Environment

•I S4

3S T l m

46

BD

72

64

«

108

110

*

Graph 13.2: Time verses Enthalpy of the system as well as for the Environment

Fig. 21: CuredTobacco Leaves

At the end of the experiment the cured tobacco were conditioned for l-2hrs and the cured tobacco leaves were collected as storage sample for the analysis. NFC-IEFR Journal of Engineering & Scientific Research

Comments: This graph shows that the enthalpy will uniformly change with change I the uniform control of the temperature. This graph shows change in the enthalpy of the environment.

H.Ratio (Kg/Kg): 0-0.2

Evaluating the Performance of Solar Tobacco Barn

Comments: This graph shows the change in the rel. humidity with change in the temperature that is uniform and shows a uniform behavior for the curing process. Humid Ratio

12

84

IS

10S

120

(nrs) Graph 13.3: Time verses Humid Ratio for the system as well as for the environment

Comments: This graph shows that the humid ratio is also uniform with uniform curing and change is uniform with the step wise change of the stages of curing. This graph shows the humid ratio of the environment.

Graph 13.6: Temperature verses Enthalpy of the system

Comments: This graph tells us the behavior of the enthalpy which the same as it is for the rel. humidity and that it is uniform for the process of curing.

Humidity Ratio

10

20

30

40

60

SO

70

SO

SO

100

T*m|j*ratur0(Dog C )

Graph 13.4: Time verses Efficiency ofthe system Graph 13.7: Temperature verses Humid Ratio of the system

Comments: This graph tells us that the efficiency will be maintained at above level of 75% because of the solar absorption and in the evening due to the fuel ignition for the curing process. 100 BO

/ J

Comments: This graph shows the change in the humid ratio which shows a uniform behavior of the curing process change in the humid ratio of the process.

/

EO TO Humidity 60 GO

100 90 SO TO T*mp*ratun* (d*s-C) BO

40

GO

30

40

20

30 20

10

10 10

20

30

40

SO

SD

TO

SO

SO

1DO

1Z

T*mptratura(DBQ C)

24

38

48

SO

72

84

SB

108

Time

Graph 13.5: Temperature verses Rel Humidity of the system Graph 13.8: Time verses Temperature of the system N F C - I E F R Journal of Engineering & Scientific Research



120

Evaluating the Performance of Solar Tobacco Barn

Comments: This graph shows that the temperature rise is uniform and step wise curing occurs and the change was uniform

for the stepwise curing, because i f we maintain the inside temperature, then we haven't sufficient heat to maintain the temperature after the sunset.

From all the experiments the data obtained and plotted against different values of temperature and also verses time to identify the difference of each experiment from each other as well as from for the system and for its surrounding.

Using the solar tobacco barn we have save fuel (coal) from 7pm to 10pm i.e. 2 kg/curing.

12. Conclusions

I f we dump our equipment with a shawl then after sunset it can retain the absorbed heat for a longer interval of time and thus much of the heat losses can be controlled.

From the above discussed fabrication and experimental work chapters some defect and advantages are identified in our system. From the analysis of these above experiments we have conclude some features of our fabricated equipment which is discussed as below. We have perform three experiments but the first one was empty run of the equipment and the conclusions are taken from the second and third experiment of the tobacco curing. The two experiments are as follows; 1) . 2) .

Tobacco curing using solar energy as a fuel Tobacco curing using solar energy as main fuel and coal fuel as secondary fuel

When a cloud appears on the sky it greatly affects the solar curing process of our equipment.

In the case of wind the heat losses from the equipment are increased. The graph of the data shows that the rise and fall of the temperature cause the increase and decrease in the rate of curing of the leaves which is affecting the quality as well as the duration of the curing. 12.2 Tobacco Curing Using Solar Energy As Main Fuel and Coal Fuel as Secondary Fuel.

Now these are discussed as below; 12.1 Tobacco Curing Using Solar Energy as a Fuel In the solar system the only fuel used is the solar energy and the curing is done upon the solar absorption. Due to losses of heat at night time the temperature rise and fall causes the damage to the quality of the leaves. The losses are much greater due to the black body radiation, which emits 50% of the absorbed radiations. It retains the heat inside the equipment for four to five hours after the sunset, which saves 2kg/curing of coal for our equipment. Due to rise and fall of temperature the curing duration is increased. We can't maintain the inside temperature required N F C - I E F R Journal of Engineering & Scientific Research

• ^54^~

In case of secondary fuel system, it makes our equipment much more efficient as compared to the only solar one. By using secondary fuel the sulphur content in the atmosphere is increased so by using washed coal we can control the air pollution. By using the secondary fuel the curing duration is decreased. By using the secondary fuel the quality of the cured leaf is improved. By using the secondary fuel the temperature inside the equipment can be maintained. Using the secondary fuel a stepwise curing is done. The use of secondary fuel required strict supervision, in order to prevent any accident. This system uses the fuel from 10pm to 7a.m up to 5.5 kg /curing. The graphs obtained from the experimental observation we have find that the temperature is maintained inside the system and the stepwise curing is done which have improved the quality of the leaves. For the secondary Fuel Special Coal

Evaluating the Performance of Solar Tobacco Barn

Briquettes Plant was designed in the Department of Chemical Engineering, University of Engineering And Technology Peshawar, which gives better handling and Combustion easiness. 12.3 Suggestions and Recommendations The equipment we have fabricated has many advantages by saving a large amount of the fuels but it still have some difficulties. By removing these defects from the equipment we can increase its efficiency as well as the workability of the equipment. We have performed two experiments on our equipments to get the cured product from it. In the first experiment we use the solar energy only while in second experiment we use the dual fuel system that consist on solar as main fuel while the coal is used as the secondary fuel at night time or in cloudy weather. From these experiments the conclusions we have taken have been discussed in the previous chapter. But in order to improve its efficiency and workability we have some suggestions and conclusions that will increase the working efficiency and energy conservations up to a great amount.

convert the solar energy to electrical energy and that energy is used for the electrical system used in the barn like that for the exhaust fans and for the lightening in the barn. The solar cells will be more economical i f we use the Tinox or the Schwartz chrome for the system, it can produce much more electrical energy for the requirements of the barn and for storage also. 13.3 Insulation of the System In our system we have used the air gape as the insulating media which is much efficient insulating material but in place of air there are lots of materials that can be used as insulating material. In order to use the best insulating material we can control the heat losses from the system efficiently. As most of losses are from north side wall which can be reduced by increasing the width of insulation. 13.4 Solar Angles

13. Various Suggestions

In flat solar collectors the main parameter is the solar collector angle. In our designed equipment we have provided the angles on side i f this angle is provided on the other side it will increase the absorptivity of the equipment. Also the tilt angles were not according to the standards because of the less area and small lab scale equipment. But in actual design these changes can make the solar tobacco barn more efficient.

13.1 Increase the Absorptivity

13.5Material of Construction

These suggestions are as given;

Instead of the black we can use the Tinox material as well as the Schwartz chrome that can have the same absorptivity as that of the black body but the only difference is that these material can retain the heat inside the equipment for a very long time interval because the Tinox material emit 5% of the absorbed energy while the Schwartz chrome emit 15% of the absorbed energy from the inside system, by using this material we can avoid the use of the need for the secondary fuel. 13.2 Use of Solar Cells In our designed we have sufficient amount of heat that is not required for the curing process, and we remove that heat by starting exhaust fans to get our required temperature. Instead of removing that heat from the barn we can use the solar cells that will NFC-IEFR Journal of Engineering & Scientific Research

We have constructed our system from the tin sheet because of its lab scale property and to make it moveable. But in actual design i f we construct our barn from the bricks we can make it fixed and the absorptivity will increase and also the insulation problems can be removed because mud is the much effective insulator for heat. Also the cost will be reduced on the equipment. Also we can use the inside secondary fuel pipe to be of that material having the high coefficient of heat transfer to transfer more and more heat from the hot gases to the inside space of the barn.

Evaluating the Performance of Solar Tobacco Barn

13.6Height of the Chimney

References

In the chimney designing i f the height of the chimney is kept high it makes the transfer of more and more heat from the hot gases and also makes the polluting components to be go far away an the life of the living things near the system can be made safe.

[I]

[2] 13.7Design Considerations In designing of the system we have made the absorption of the black body below the glass surface and the glass surface is used for the refraction of the solar rays which will refracted on the black body. In changing the designing of the solar absorber we can keep the black body over the surface which an increase the absorption of the heat from the solar much greater and will not retain the heat.

[3]

[4]

[5]

13.8 Losses Control [6] The losses from the system can be controlled by different method either by dumping the equipment with a thick cloth after sunset or by using the most efficient insulating material for the control of the heat loses. Also the use of low emissive absorber for the solar absorption can make more control over the losses.

[7] [8]

13.9 Dumping Of the Equipment [9] The equipment must be dumped by the thick cloth piece or by specific arrangement to retain the heat inside the system for much longer time that will minimize the use of the secondary fuel. Also dumping of the equipment can protect the losses due to wind or by the rain fall which makes great losses of the heat from the equipment in day time also.

[ 10] [II] [12] [13]

13.10 Thickness ofthe Black Paint The thickness of the black paint in the black body also affects the absorptivity of the equipment. I f the thickness of the paint increases it will intern increased the absorption of the equipment and can minimize the losses by the absorbing surface. Insulation of Floor.

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Akbari, Joseph; Hashem "Historical Overview of Climate Change Science" Intergovernmental Panel on Climate Change Retrieved on 2007-092 9 . . H t t p : / / i p c c wgl .ucar.edu/wgl/Report/AR4WGl_Print_ChO 1 .pd f Alan Ward, Chelsea House, Renewable Energy: A Concise Guide to Green Alternatives, by Jennifer Carless, Walker & Company, Renewable Energy, by Alan Collison, Rain tree Stick-Vaughn. 1999 Anderson, Alfred, International Development Research Centre, Ottawa, Canada inNovember 1998. Http://archive.idrc.ca/library/document/046680/cha p7_e.html. Breen, T. H. Tobacco Culture. Princeton University Press. ISBN 0-691-00596-6. Source on tobacco culture in eighteenth-century Virginia (1985). Http://www. woodweb.com/knowledge_base/Homeb uiltsolarkiln html Bruce Anderson with Michael Riordan the Solar Home Book: Heating, Cooling, and Designing with the Sun, BrickHouse Publishing Company. (2005) Booth.B.Hall. Solar absorbers and their earth geometry arrangements, (27-28th May 2009) www.intersolar.com/absorbers/angles C. Leik Friends of the Thumb Octagon Barn, July 1994 http: //www. thebany ournal. org/round/b arris. html Cindy Echevarria,Seth KnaebefSaKeithia Mason and Professor Gary Powers and Matt Cline Unsteady State Heat Transfer Through Tin, Unsteady-State Heat Transfer: Characterization of Heat Transfer Coefficients and Flow in a Cylindrical Container.3rd edition. March24,2000. Collins WK. and S.N. Hawks. "Principles of FlueCured Tobacco Production" 1st Edition, Devilliar.R, Tobacco curing process and its equipment from ventobacco i n d u s t r y . 1981 www. ventobacco .com Dock. Glass refraction and reflection theory of the day to day use. 3rd edition. 1968 Fred and Gerry for sending March 24, 2008 http://www.builditsolar.com/Projects/SpaceH eating/SolarGarageCollector/FredsCollector. html. Full description and all the details on how to build your own are available in these two articles: The issue of Mother Earth News and The issue of Home Power Magazine. December/January 2006 Gary Frey, Deborah M.. Hydropower as a renewable and sustainable energy resource meeting global energy challenges in a reasonable way. Energy Policy. June 9, 2002. Http ://www.apricus.com/html/solar_collector installationbasics. html Gately, Iain. Tobacco: A Cultural History of How an Exotic Plant Seduced Civilization. Grove Press, 2003. GottsegenJ.J Tobacco: A Study of Its Consumption in the United States, 1940, Graven Flat Solar Colletor for the utilization of the

Evaluating the Performance of Solar Tobacco Barn

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