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A Patsari cookstove, nicknamed the Schatzari was built at the Schatz Energy Research Center (SERC) laboratory on May 27, 2010. The purpose of this Appropredia page is to describe the construction process of the Patsari, with a particular focus on the modifications and deviations that were made from the document, “Estufa Patsari; Manual de Construccion (EPMC).” This page is intended to serve as an amendment to the construction manual that was published by the Grupo Interdisciplinario de Tecnologîa Rural Apropiada (GIRA), and should not be considered a stand-alone document. The construction process marks the beginning of a collaboration between GIRA and SERC. The goal is to use the stove as a tool to develop research projects aimed at investigating the relationship between stove combustion design parameters and emissions of black carbon (BC). BC is a major contributor to global warming and accelerated glacial melt. Furthermore, emission of BC inside the home is a public health concern because of its role in causing chronic and acute respiratory diseases in groups that experience significant exposure, particularly in the Global South. This will add to the scientific knowledge base of biomass cookstoves, as they relate to local and global scale emissions inventories of BC and co-pollutants. Past studies have shown that the Patsari’s combustion chamber design increases combustion efficiency, reduces emissions of BC and other particulate matter, and decreases consumption of fuel wood.
GIRA members leading the construction process were Omar Masera, Victor Berrueta, and Ilse Ruiz Mercado. SERC members assisting in the construction process were Greg Chapman, Tirian Mink, and Ruben Garcia. The stove was completed and briefly tested on May 28, 2010. The latest version (as of 5/27/10) of the EPMC was followed closely. Any deviations from the manual were made to accommodate the difference between materials procured in Arcata versus Mexico, as well as to accommodate future stove testing. The primary modifications were the addition of air supply lines into the combustion chamber, as well as ducts for the insertion of thermocouples into various locations inside the stove.
Pre-construction Preparation Work
As specified in the EPMC, a heavy-duty metal table (130cm x 99cm x 78.5cm) capable of supporting several hundreds pounds was procured to serve as a stove base. The table was sanded and cleaned to eliminate rust.
A mold was built from plywood to ensure proper exterior stove dimensions. The mold dimensions (107cm x 70cm x 29cm) were slightly larger than specified in the EPMC, as advised by the GIRA team.
Since local bricks were slightly smaller than that normally used, a brick configuration was designed to fit the mold with the smaller bricks. This required cutting bricks and dry fitting them in the mold through a trial and error process until proper stove dimension were achieved. Since local sand was courser than that normally used, a sieve was built to filter out small rocks (approximately > 1/8" wide).
Bricks were arranged inside the mold and photographed to preserve the exact brick configuration during the brick laying process. It should be noted that the exterior dimensions of the stove are not important so long as the stove can accommodate the combustion chamber interior dimensions of 36cm x 22cm x 12cm, and the cooking surfaces.
|standard red bricks||20.5cm x 9.5cm x 6.2cm||55-60|
|yellow fire bricks||23.4cm x 11.9cm x 3.2cm||8-10|
|Sakrete Types S Masonry Mortar||60-pound bag||2|
|fine sand||5-gallon bucket||2|
|H.C. Mortar Clay (A Superior Clay Product)||50-pound bag||1|
|½“ Hardibacker fireboard||3’x 5’ sheet||1|
|metal chimney tubes||4” diam x 90 cm||3|
The following tools and materials were manufactured in Mexico and brought by the GIRA team:
|metal chimney base (with two rectangular inlets for secondary burners and one circular outlet for chimney)||9 cm diam., 5cm x 8cm||1|
|metal secondary burner mold||See picture||1|
|Novaceramic Vintex brick/ with interior holes||105cm x 70cm x 27cm / 8cm x 8cm x 6cm||1|
|primary burner, 14 gauge steel||54 cm diam||1|
|secondary burners, 14 gauge steel||28 cm diam||2|
Overview of construction process
Day 1: On Wednesday May 26, 2010, members of GIRA arrived at SERC to take part in a planning session for the following day’s stove construction process. GIRA members observed that due to regional differences in clay, sand, and mortar, sample clay mixtures should be made to determine the optimal mixture. To determine this, different ratios of clay, sand, and mortar were made. The following day, the samples were observed and it was determined the most suitable ratio was 1 part clay, 2 parts sand, and 2 parts mortar (1:2:2).
Day 2: On Thursday May 27, 2010, members of GIRA and SERC built the Patsari cook stove.
Day 3: On Friday May 28, 2010, the chimney was installed and the stove was demonstrated by preparing a batch of quesadillas.
Step-by-step construction process
To minimize conductive heat loss to the metal table, and to assure good adhesion of bricks, a sheet of ½” Hardibacker was laid on the table as a base for the stove to be built. The sheet was scored, cut and centered on the tabletop. The wood mold was centered on the fireboard, prior to beginning stove construction. Bricklaying was started inside the front left-corner of the wood mold.
A half-bucket of mortar was mixed with enough tap water to make a thick, workable, non-runny mixture for brick laying. Subsequent batches of mortar were made in a similar fashion as needed. Mortar was placed on the bottom of each brick making up the bottom-most layer, to bind the stove bottom to the fireboard. Mortar was placed on every side of each brick that butts up to another brick
Bricks were laid in the following sequence with careful attention focused on maintaining combustion chamber dimensions of 36cm x 22cm x 12cm,
- Outer-bottom course, including bottom course of combustion chamber (Note: three fire bricks were used as the bottom layer of the combustion chamber and the first course of combustion chamber bricks started from the Hardibacker (not on the fire brick))
- Outer-middle course, including middle course of combustion chamber (Note: a non-mortared brick should be placed under the combustion chamber opening, to serve as a support for the middle course, until dry.)
- Outer-top course, not including top course of combustion chamber bricks; the third course of combustion chamber bricks were added after the addition of gravel below.
The Novaceramic Vintex brick was cut in equal halves and positioned in the gravel to serve as support structures for the channels that connect the primary combustion chamber to the secondary burners. For accurate positioning, the primary (larger) burner was momentarily placed on top of the combustion chamber and the secondary burner mold placed close to the chimney inlets (see EPMC for details)
To create the stove’s top clay layer, one bucket of filtered sand, one bucket of mortar, and a half-bucket of mortar clay (2:2:1 ratio) were thoroughly dry-mixed with a shovel on a large sheet of plywood. Tap water was slowly added and mixed in until a sticky and non-runny clay like consistency was reached. The GIRA team indicated that the ideal consistency for the mixture can be described as “chewing gum.”
The clay mixture was carefully added to the back half of the stove only, until the top of the third brick course was reached (After construction was completed, GIRA members observed that the mixture was crumbling and it was speculated that this was due to too much sand and too little clay. This should be accounted for in future construction of Patsaris in the US)
Outside of the burner boundary, clay was added to the top of the final brick course. Inside the burner boundary, a 2 to 3 cm layer of clay was added from the top of combustion chamber brick course. The objective in building up the clay above the combustion chamber was to create a 2 cm vertical gap below the bottom of the burner