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Prototyping of the Improved Cook-Stove and Solar Heater designed by Appropriate Technology Asia |
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Background
Ladhak, a cold desert in northern India in the Himalayan range, experiences
extreme cold conditions for over 8 months in a year. To survive these
conditions, room heating is an essential requirement. Few heater and stoves
are locally available in the area but are not efficiently designed.
Appropriate Technology Asia (ATA) designed solar heater and cook-stoves
based on available material, to be manufactured in Ladhak. The prototyping
of the solar heater and cook-stoves has been carried out by Research and
Development team of Development Alternatives with emphasis on an efficient
production system. In the first phase, based on the design of the
Appropriate Technology Asia (ATA), Development Alternatives has developed
the following two products
| 1. | Solar Hot Water System |
| 2. | Improved Cook-stove |
The main stages of product research and development are explained below:
1. SOLAR HOT WATER SYSTEM
The Solar Hot Water
System is a device in which solar energy is used for heating water. The
device has a ferro-cement parabolic dish of diameter 1430mm and thickness 25
mm in which the inner part is lined by mirror to converge the reflected rays
of sun. An armature has been designed on which the ferro-cement parabolic
dish is positioned to converge the reflected sunlight at the focal point of
the inner parabolic curvature. The container for heating water will be
positioned at the focal point
The parts of the Solar Hot Water System are as follows;
| @ | Dish |
| @ | Armature |
| @ | Stand |
| @ | Ring |
Activity undertaken
Dish
During the
development process of the Dish the steps adopted are as follows:
| Step1
: Drawn the
given curvature on a paper to use as a template.
Step2 : Designed the tool for the production of both the mould and product Step3 :
Rolled the flats based on the template one for the mould and the other
for the product which is 25 mm offset of the Step4 : Developed the tool with the frame stand Step5 : Marked the foundation by positioning the tool for manufacturing of the mould Step6 : Dig the holes, positioned the reinforcement and foundation bolts and cast with cement mix Step7 : Bolted the frame of the tool with the foundation Step8 : Drawn the axes and the circle Step9 : Positioned brick blocks and filled the parabolic dome with cement, sand and aggregate with the help of the tool with moulds profile Step10: Chasing the edge of the mould for the de-moulding the cast dish Step11: Plastered with P.O.P for the smooth surface of the mould Step12: Knitted the reinforcement of the Dish and welded the square bar for positioning the reinforcement at the centre of the thickness of the dish Step13: Filled the de-moulding gap with clay Step14: Cast the dish with cement-sand mix with the help of the tool with products profile leaving a 3" diameter hole at the top Step15: De-moulded the dish after 24hrs. Step16: Cured for 2days with normal wet sack Step17: Covered with plastic sheet and kept the dish up side down by filling with water for self curing. Step18: Designed and developed a gauge for cutting the mirror section for glueing on the inner surface of the dish Step19: Glued the mirror sections of 15 different sections at a row and about 43 rows in a concentric manner on the inner surface of the dish Step20: Cleaned the face of the mirror sections |
mouldArmature and Stand
During the development
process of the Armature the steps adopted are as follows:
Step1
: Parted off
the pipe, angle, flat and round sections as per given design
Step2 : Marking and drilled the holes Step3 : Rolled the flats into bent section and welded Step4 : Welded a round bar on a 200kg plate for inserting the pipe stand for the Base Step5 :
Fixing the Chain |
| Ring During the development process of the Ring the steps adopted are as follows: Step1 : Parted off the round bars as per design Step2 : Rolled the bars as per required parameters Step3 :
Welded the three rolled rings and the other round bars at the outside
surface of the dish at the projected square rods Step2 : Positioned the dish by measuring the focal point through visual checking Step3 : Cleaned the face of the mirrors Step4 : Tested |
Observation and Trial
Comparison data of heating between ATA’s designed
Solar Hot Water System and TARA Solar Cooker which was done at same time and
heating same quantity of water on symmetric vessels are given below:
Test No: 1
Date: 02.02.04
Quantity of Water: 4 lits
Atmospheric temperature: 200C
| S.NO | TIME | TEMPRATURE of WATER | |
| TARA Solar Cooker | ATA’s Solar Hot Water System | ||
| 1. | 11:55 | 220C | 220C |
| 2. | 12:05 | 340C | 340C |
| 3. | 12:15 | 440C | 380C |
| 4. | 12:25 | 540C | 440C |
| 5. | 12:35 | 620C | 480C |
| 6. | 12:45 | 660C | 500C |
| 7. | 12:55 | 720C | 540C |
| 8. | 14:15 | 880C | 680C |
| 9. | 14:30 | 900C | 680C |
Test No: 2
Date: 03.02.04s
Quantity of Water: 4 lits
Atmospheric temperature: 260C
| S.NO | TIME | TEMPRATURE of WATER | |
| TARA Solar Cooker | ATA’s Solar Hot Water System | ||
| 1. | 11:05 | 220C | 220C |
| 2. | 11:15 | 320C | 280C |
| 3. | 11:25 | 400C | 340C |
| 4. | 11:35 | 480C | 400C |
| 5. | 11:45 | 540C | 460C |
| 6. | 11:55 | 600C | 500C |
| 7. | 12:05 | 660C | 550C |
| 8. | 12:15 | 700C | 580C |
Test No: 3
Dated: 03.02.04s
Quantity of Milk: 1 lit
Quantity of Rice: 0.3Kg
Atmospheric temperature: 190C
Cooked dish: Rice pudding in 1.55hrs (11:05 -13.00) which was well cooked
The test report shows
that the performance of TARA Solar Cooker is better than ATA’s Solar Hot
Water System whereas theoretically ATA’s Solar Hot Water System should have
better performance. Theoretically the amount of sunlight concentrated at the
focal point of ATA’s Solar Hot Water System is more than the TARA Solar
Cooker because the diameter of the dish of ATA’s Solar Hot Water System is
1430mm whereas the diameter of TARA Solar Cooker is 1380mm. The difference
in heating efficiency is due to the following:
1. The armature obstructs a good amount of reflected light in ATA’s Solar Hot Water System
2. In ATA’s Solar Hot Water System, 20% surface of the container gets heated whereas in the TARA Solar Cooker , 57.2% surface of the container gets heated.
Recommendation
On the basis of the tests
explained above there is a need to redesign the armature and also the
profile so that more reflected light can be projected on the heating
container.
During the knitting of the reinforcement wires there is a need to develop a
simple fixture to knit the reinforcement wires otherwise poor knitted
reinforcement wires will create problem for the rotating profile making tool
during casting of the dish.
2. IMPROVED COOK-STOVE
-2
The Improved Cook-stove 2
is one of the two cook stoves designed by ATA which is made up of 18SWG
metallic mild steel sheet. It has three openings for cooking and one for the
outlet of burnt gas of the fuel inside the cook-stove through chimney. The
Improved Cook-stove 2 is positioned on a MS angled metallic frame which has
oven space inside it with a fuel feeding door and a air sliding system for
the regulating the air inside the cook-stove.
Followings are the parts of the Improved Cook-stove
2 is as follows;
| @ | Frame |
| @ | Stove Body |
| @ | Stove Top |
| @ | Doors |
| @ | Air-slide |
| @ | Steel Mesh |
Activity undertaken
The list of
activities undertaken during the development of the Improved Cook-stove 2 is
described below:
| Frame During the development process of the Frame 1 (as per given design) the steps adopted are as follows: Step1 : Parted off the MS Angle section 25x25x3mm as per given design Step2 : Removed the Burrs Step3 : Welded the frame as per given design Step4 : Grinded the welding portion and removed the burrs After the development of the stove body from paper we found the stove body was not fitted. Based on that feed-back we have redesigned the frame and also made in such a way which can easily be bolted in place of welding the complete frame. The steps for the development of Frame 2 are as follows: Step1 : Parted off the MS Angle section 25x25x3mm as per the design emerged from the feed-back Step2 : Removed the Burrs Step3 : Sheared the part by chisel for bending Step4 : Designed and developed bending tools for the bending of the edges of the required angle parts Step5 : Marked and drilled the holes for bolting or riveting Step6 : Removed the Burrs Step7 : Assembled the frame by bolting Stove Body Step1 : Marked the Stove carcass layout (both the firm and dotted lines)on a 1mm MS sheet Step2 : Chiseled out the required sheet to make a template Step3 : Marked the layout (both the firm and dotted lines)on a paper based on the template Step4 : Cut the required portion Step5 : Fold the paper sheet as per the dotted lines Step6 : Glued where required After the development of the stove model on paper we have figured out that the small modification is required at the point marked in the drawing enclosed Step7 : Marked the Stove carcass layout (both the firm and dotted lines)on a 1.2mm (18SWG) MS sheet Step8 : Chiseled out the required area from the sheet Step9 : Removed the burrs Step10: Folded the cut sheet as per the dotted lines Step11: Spot welded at required position Step12: Marked and cut the corner insert Step13: Welded inside the stove body where it required Step14: Marked and gas cut the baffle from the 6mm MS sheet Step15: Removed the burrs of the baffle Step16: Drilled the holes and bent as required on baffle Step17: Assembled the body, baffle and frame Stove Top Step1 : Marked and gas cut the Stove Top from the 6mm MS sheet Step2 : Removed the burrs Step3 : Marked and chiseled the Top rim and chimney ring from the 1.2mm MS sheet of width 50mm Step4 : Folded the cut sheet as per the dotted lines Step5 : Positioned the rim on the top plate, drilled and riveted Step6 : Removed the burrs Step7 :
Assembled with the body Step1 : Marked and chiseled the layout of drawer from the 1.2mm MS sheet Step2 : Removed the burrs Step3 : Folded the cut sheet as per the dotted lines Doors Step1 : Marked and chiseled the layout of Doors and locks from the 1.2mm MS sheet Step2 : Removed the burrs Step3 : Marked and drilled holes on the doors sheets Step4 : Welded hinges with the doors and the stove body Step5 : Bent the locking devices Step6 : Bolted and assembled the doors with locking arrangements Air-slide Step1 : Designed and developed a die punch arrangement for the Air slide mechanism Step2 : Marked and chiseled the layout of Air Slide and locks from the 1.2mm MS sheet Step3 : Removed the burrs Step4 : Pressed the sheet for the channel and the door Step5 : Removed the burrs Step6 : Welded the attachment with the Stove Body Step7 : Removed the burrs Steel Mesh Step1 : Marked and chiseled the layout of Steel Mesh Step2 : Positioned it inside the stove Thus the Improved cook stove is completely assembled and ready for testing. |
Observation and Trial
Efficiency testing of improved cook stove 2
| Test -1 | |
| Room temperature | 18˚c |
| Initial temperature of water | 19˚c |
| Boiling temperature of water | 99˚c |
| Weight of fuel taken | 3.0 Kg. |
| Weight of fuel burn | 2.8 Kg. |
| Weights of char remain | 0.132 Kg. |
| Volume of water | 6.0 liter |
| Volume of water after evaporation | 5.8 liter |
| Calorific value of fuel used | 4562 Kcal/Kg. |
| Starting time of the experiment | 4.30 PM |
| Time when temperature reached 99˚c | 4.22 PM |
| Weight of fuel unburned | 0.18 Kg. |
| Time of experiment | 1-Hour |
% Efficiency = (Heat out-put
/ Heat in-put) x 100
Heat Out-put = A + B
Where
A=Sensible Heat and
B= latent Heat
|
Sensible Heat = |
(Boiling temperature of water-Initial temperature of water) x initial volume of water |
| = | (99˚c - 19˚c) x 6.0 |
| = | 80 x 6.0 |
| = | 480 Kcal |
|
Latent Heat = |
(Initial volume of water – final volume of water)s x 540 |
| = | (6.0 – 5.8) x 540 |
| = | 0.2 x 540 |
| = | 108 Kcal |
| Heat Out-put = | 480+108 |
| = | 588 Kcal |
| Heat in-put = | C - D |
| Where C = | Heat value of fuel |
| = | Fuel Burn x Calorific value of fuel |
| = | 2.8 x 4562 |
| = | 12773.6 kcal |
| D = | Heat value of char |
| = | Quantity of char x calorific value of char |
| = | 0.140 x 7100 |
| = | 994 Kca |
| Heat In-put = | 12773.6-994 |
| = | 11779.6 Kcal |
| Efficiency= | (Heat out-put / Heat in-put) x 100 |
| = | (588/11779.6) x 100 |
| = | 4.99% |
| = | 5.00% |
| Test -2 | |
| Room temperature | 14˚c |
| Initial temperature of water | 15˚c |
| Boiling temperature of water | 99˚c |
| Weight of fuel taken | 4.0 Kg |
| Weight of fuel burn | 3.09 Kg |
| Weights of char remain | 0.110 Kg. |
| Volume of water | 6.0 liter |
| Volume of water after evaporation | 5.7 liter |
| Calorific value of fuel used | 4562 Kcal/Kg. |
| Starting time of the experiment | 9.30 AM |
| Time when temperature reached 99˚c | 10.20 AM |
| Weight of fuel unburned | 0.910 Kg. |
| Time of experiment | 1-Hour |
% Efficiency = (Heat
out-put / Heat in-put) x 100
Heat Out-put = A + B
Where
A=Sensible Heat and
B= latent Heat
| Sensible Heat = | (Boiling temperature of water-Initial temperature of water) x initial volume of water |
| = | (99˚c - 15˚c) x 6.0 |
| = | 84 x 6.0 |
| = | 504 Kcal |
| Latent Heat | (Initial volume of water – final volume of water) x 540 |
| = | (6.0 – 5.7) x 540 |
| = | 0.3 x 540 |
| = | 162 Kcal |
| Heat Out-put= | 504 + 162 |
| = | 666 Kcal |
| Heat in-put= | C - D |
| Where C= | Heat value of fuel |
| = | Fuel Burn x Calorific value of fuel |
| = | 3.09 x 4562 |
| = | 14096.5 kcal |
| D= | Heat value of char |
| = | Quantity of char x calorific value of char |
| = | 0.110 x 7100 |
| = | 781Kcal |
| Heat In-put= | 14096.5-781 |
| = | 13315.5 Kcal |
| Efficiency = | (Heat out-put / Heat in-put) x 100 |
|
= = |
(666
/13315.5) x 100 5.00% |
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Recommendation The test result shows that efficiency of the Improved Cook-stove2 is only 5%, which means that the 95% of heat is used in room heating or is lost through chimney. Therefore, the device is a good room heater but not a good cook-stove. To increase the efficiency of cook-stove there is need for an insulating surface beside the fire and decrease the distance between the fire and heating container. The insulating surface can be created by developing a layer of a perforated sheet beside the firing zone by which heat loss can be reduced. During the development of the Improved Cook-stove2, the bending of the sheet at the zone A in the drawing is very complicated. To simplifies the process stove body should be manufactured in three different parts and assembled either by welding or riveting. |
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