# Presentation: 700064

## Darfur Cookstoves ProjectFinal Report5/10/06

***Jesse Woo, Charles Kirubi, Susan Amrose, and Teddy Kisch***

**Notes:**
AJG Notes:

In Spring 2006 Semester at UC Berkeley 
Jess Woo: Mechanical Engineering Grad student,   Charles Kirubi: Energy and Resources Grad student (energy emphasis)
Susan Amrose: Physics doctoral student, Teddy Kisch: Environmental Science Undergrad

## Latest Events in Darfur(3/8/06) 30,000 march in Khartoum opposing UN involvement. (3/10/06) UN decides to take over peacekeeping in Darfur.  Firewood patrols one of the heaviest security operations in Darfur (>3000 IDPs gather firewood/week) Fuelwood scarcity becoming unbearable – new challenge from UN officers to find alternative fuel (beyond our scope)

**Notes:**
AJG Note:

Throughout the Semester, student team kept up with detailed news reports on the developments in Darfur.

## Update on Darfur Conflict continued...

- 4/28/06 UN World food program cutting rations *in half* (due to lack of funds).
- 4/30/06 thousands march in Washington D.C., Golden Gate Bridge (we were there!)
- 5/1/06 Latest peace talks fail - deadline extended to Thursday

**Notes:**
Continued.

## Our Goals

*Optimum:*
- Modify the Tara cookstove to make it STABLE (ie., not prone to tip over) during the vigorous stirring of assida in round-bottom traditional pot.
- Modify the Tara cookstove to that it retains HIGH FUEL EFFICIENCY IN WIND as most cooking is done in the open.
**Final design should be *****low cost*****, easy to make in Darfur, and increase relative *****fuel efficiency.****  *
*Minimum: *one of the two above

**Notes:**
AJG Notes:

Each team was asked to define their “optimal” goals and “minimal” goals for the Semester-long effort at the start of the Semester.  They were allowed to fine tune the goals based on their additional research and any outside feedback at the mid-Semester point.  Darfur Cookstoves team did not change any of their goals mid-semester.

## Methods - I

- Brainstorm stove design
- 	 - low cost, no moving parts

- Rejected

- Accepted

**Notes:**
AJG Notes:

The student team read up and learned about stove performance and testing protocols, under my direction.  
We came up with several designs and thought each of them through for ease of manufacture, cost, performance, reliability and failure modes, field conditions etc..  
One of the rejected designs for improved stability is shown on the left.  
Two of the four design changes made to Tara to make the “Berkeley Tara” are shown on the right (stability bars, and wind collar attached to the top of the stove).     

## Methods - II

- Fabricate a model of the stove design

- Assida Pot

- Original

- Mulah pot

- Modified

- Original

- Modified

**Notes:**
AJG Notes:

We took the sizes and shapes of cooking pots for Assida and Mulah as culturally given.  I had seen how the flat bottom aluminum pots distributed to the IDPs by the IRC had been rejected or fallen into disuse in all the households I visited in Kalma and Otash.  Similar findings in North Darfur camps visited by our team in Nov-Dec. 2005.

Given the different size of the two pots, the above photos show the fit of the two pots in the Berkeley Tara stove. 

## Methods II (continued)

- Brackets reduced sink mullah pot inside
- Wind collar added to the top to prevent breeze interfering with heat transfer
- Bottom vents redesigned to reduce impact of breeze on heat transfer

**Notes:**
AJG Notes:

These sketches show three of the four modifications made to standard Tara.

The support brackets on the inside top perimeter of the Tara stove are changed in size to allow the Mulah-pot to sink into the stove -- substantially increasing the fuel efficiency.

The wind collar attached to the stove top provides substantially better performance during Assida making in the presence of 5 to 6 mph wind. (we used a table fan and a calibrated rotating cup anemometer to reliably produce standard wind for replicate tests)

The bottom vents are no longer straight-through holes, but vertical cuts in the metal that are bent to allow air passage tangentially into the stove body.

## Methods - III 

- Electric Range Test to develop mullah protocol
- Gas Stove- can control flames
- Confirm the chemical process while frying onions
- - Test establishes ‘elbow’, the point where the heat has evaporated the water and is dramatically increases temperature

**Notes:**
AJG Notes:

Before any performance testing could proceed, we had to define our own standardized test protocols and confirm that they were accurate and reproducible.  We did that on an electric range for frying onions for Mulah.

 Two of the test results are shown.  Temperatures were sampled at very high frequency with a thermocouple attached to a wooden spoon that stirred, at a fixed rate, the onions during frying.  It was very important to get the right proportion of cut onions and oil for making the Mulah.  Data from the Nov-Dec. 2005 field visit to Darfur camps were invaluable for these details.

Test point was determined to be 120 Celsius, the elbow in the curve above which the temperature rises rapidly because water has evaporated off.

## Methods – IV

- Establish protocol for testing relative efficiency

*Assida:* water boiling test
- Bring to boil, simmer 15 min
*Mulah*: onion frying test
- - Bring onion/oil mix to 120C

- For both tests, compare the wood used for original and modified stoves, with and without a breeze

**Notes:**
AJG Notes:

The photo shows Kirubi, Woo, and Amrose conducting a test in the presence of fan-driven wind.  A rotating cup anemometer is in front of the fan, near the stove.  Its shadow can be seen on the stove, but it is mostly blocked from view by the fan.  Woo is stirring the onions, Amrose is tending the fire.  Kirubi is recording the temperatures.

## On the learning curve...

- Our results were affected by
- Fire tender -- I.e., the cook
- Doubling up - running two stoves at once
- Ambient breeze
- Size and age of chopped onions

**Notes:**
AJG Notes:
The students found that doing all this takes a lot of attention and effort.  They wanted to perform more tests than are reported here.  When they tried to conduct two tests in parallel (to get results more rapidly), they found they failed --- it is hard to take data, tend the fire, and do the cooking per experimental protocols on two stoves at once.  So, some test results had to be discarded.

The students discovered that the person tending the fire affects the results enough that the same person has to tend the fire for a fair comparison.

By “age of chopped onions” the students are referring to another failed time-saving effort.  They chopped and stored onions in bulk in advance of the test.  They found that water from the chopped onions would slowly evaporate and the results with freshly chopped onions would be different from the results with “aged” chopped onions.  Again test results had to be discarded and only freshly chopped onion data are shown.

These lessons required time to learn -- but that is part of the education.  Some of these efforts to speed up the research did not work.

## Onion-frying Test ResultsMulah with modified and unmodified Tara Stove

_**Calculations**_
- Increased fuel savings =
- [W (unmodified) – W (modified)] / W (unmodified)

**Conclusions:**
**40% relative fuelwood savings for Mulah in still air!**
**57% relative fuelwood savings with a breeze!**

**Notes:**
AJG Notes:

Trimming the top horizontal support tabs so that the Mulah pot sinks into the stove improves the fuel efficiency by by about 50% over the standard Tara !!
Larger fuel savings in presence of wind.
In the formula on the right hand side of this slide, W refers to the weight of fuelwood consumed.

## Test Results cont’d: Mulah without wind

- 40.22% relative firewood savings!

**Notes:**
AJG Notes:

Detailed results for Mulah making without wind.

## Test Results cont’d: Mulah Test with wind

- 56.55% relative firewood savings!

**Notes:**
AJG Notes:

Detailed results for Mulah making in presence of wind.  

## Water Boiling Test ResultsAssida with modified and unmodified Tara Stove

| NO WIND |  |
| --- | --- |
| 4/15 | 9.21% |
| 4/18 | 10.09% |
| 4/26 | 5.69% |
| Mean | 8.33% |
| StdDev | 2.33% |

**Conclusions:**
**Minor fuelwood savings in still air (only 8%) - due to poor fit of the large assida pot; hard to fit different pots on one stove top**
**75% fuelwood savings in presence of breeze!**

- 0.00%

- 10.00%

- 20.00%

- 30.00%

- 40.00%

- 50.00%

- 60.00%

- 70.00%

- 80.00%

- 90.00%

- 1

**Test category**

**Fuelwood Savings Relative to **

**original TARA**

- Assida without Wind

- Assida with Wind (6 mph)

**Notes:**
AJG Notes:

The modified stove does not much improve the efficiency further for making Assida (over that of Standard Tara) in our test, when there is no wind (only about a 10% improvement).   However, we find substantial  (75%) improvement in presence of 6 mph wind.

Would have wanted to conduct more tests to get better statistics.  However, as noted earlier, efforts to improve the efficiency of our research were sometimes not successful, and led to having to discard the test results.

## Test Results Summary 

**Our Modifications work!**  Improvements over Standard Tara in plain text; savings over a three-stone fire **in bold text**:
- Mulah
- 40% fuel savings in still air** (~70% savings over a three stone fire)**
- 57% fuelwood savings in a strong breeze** (~80% savings over a three stone fire)**
- Assida
- 8% fuelwood savings in still air** (~55% savings over a three stone fire)**
- 75% fuelwood savings in a strong breeze** (~88% savings over a three stone fire)**

**Notes:**
AJG Notes:

High level summary of the fuel-efficiency part of the work

## Stability? 

- The current stove design lacks stability
- In Dr. Gadgil’s November visit, the pot easily tipped over during cooking unless a second person held it down.

**Notes:**
AJG Notes:

Stability of the stirred pot+stove while making Assida was a problem noted during the field testing in Nov-Dec. 2005.  It was not the pot alone that tended to fall off the stove.  The pot sat firmly in the stove, but the pot+stove combination tended to tip over during the vigorous stirring towards the end phase of Assida making.

## Initial Stability Designs

- Stones to provide stability
- Tripod protruding from wind collar
- Swinging hinges locking the pot in place
- Reinforced cross-bars running through the bottom

**Notes:**
AJG Notes:

These are some of the designs changes we considered and rejected since the revised design had to meet several criteria (cost, simplicity, fewer parts, ease of manufacture, etc.)

## Final Design

-  Stakes attached to stove lock into the ground
-  Stakes positioned so stove cannot be operated without driving them into ground
- Original and modified designs tested with the use of mechanical spring balance
- Results: Stakes make the stove over 10x more stable!

**Notes:**
AJG Notes

The lower picture shows how we tested the stability of the stove+pot combination by exerting a measured lateral force (through a spring balance) on a Assida pot loaded with simulated foodstuff.  The Tara stove and Assida pot toppled with a lateral force of about a 2.25 kg weight pulling horizontally on the pot).  The modified stove with Assida pot, with the stability pegs pushed into the soil, would not topple with a force that was more than 10 times larger.

In fact, the student were unable to topple the Berkeley Tara stove with Assida pot -- as they increased the applied force well beyond 22 kg weight, the Assida pot started slipping off the stove, but the Berkeley Tara stove would still not topple.  So, we feel we have clearly resolved the problem of mechanical instability for the stove+pot combination. 

## Future Work 

**Design stove for mass production locally in Darfur -- June 2006**** **
**Cookstove Dissemination ****CHF: Plan to produce 10,000 stoves this year**
** **
**40,000 in the next year, ultimately 300,000**
**New Funding Sources being explored : Bears Breaking Boundaries, Chancellor’s office, Philanthropic Foundations**
- To donate - go to **http://darfurstoves.lbl.gov**

**Notes:**
AJG Notes:

These are not promises by the student team, this was their impression when they wrote future plans.  We might do better!!