Grantee Research Project Results
Final Report: Biofueled Thermoelectric Cookstove
EPA Contract Number: EPD17004Title: Biofueled Thermoelectric Cookstove
Investigators: Leavitt, Frederick A
Small Business: Hi-Z Technology, Inc.
EPA Contact: Richards, April
Phase: I
Project Period: November 1, 2016 through April 30, 2017
Project Amount: $99,999
RFA: Small Business Innovation Research (SBIR) - Phase I (2016) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR)
Description:
The purpose of this project was to design and fabricate a bio-fueled cookstove that is 35% efficient, can produce at least 8 watts of electrical power and is affordable for families living in developing nations. The availability of this stove will allow families to generate electrical power while cooking that can charge cell phones and power LED lights. A clean burning “power stove” eliminates the need for kerosene reducing pulmonary diseases and free electricity for lights and battery charging can reduce cost and improve the quality of life.
Hi-Z Technology developed a small bio-fueled cookstove designed to be used by families in remote locations with little or no access to electric power. The stove was fueled using available bio-matter such as wood, crop residue, other plant matter and animal dung. The stove generates eight to ten watts of electric power which is enough to charge two cell phones and power LED lights for four hours after a typical day of cooking.
The electrical power was generated by directing a portion of the heat produced by the burning fuel through a thermoelectric module. To maintain a temperature difference across the module a portion of the electrical power produced was used to power a fan that directed cooling air across a heat sink fixed to the cold side of the thermoelectric module.
To enhance combustion, some of the cooling air was directed into the combustion zone ensuring sufficient oxygen was present to allow complete combustion of the fuel. In this manner the efficiency of the combustion was maximized allowing for the use of less fuel and essentially eliminated all smoke.
Summary/Accomplishments (Outputs/Outcomes):
Hi-Z successfully met all of their objectives by a) minimizing heat lost, b) maximizing combustion efficiency and c) maximizing heat transfer from the hot exhaust gases into the cooking vessel.
Heat lost from the combustion chamber was minimized in four ways. A cover or door was used to block radiant heat from exiting out the opening where fuel is fed into the combustion chamber, combustion air was fed into the combustion chamber in a way that ensured good mixing while preventing the flame from impinging on the combustion wall surface thereby keeping the combustion walls as cool as possible and finally, insulation was packed around the combustion chamber to reduce conductive and convective heat loss out the combustion chamber walls.
Most of the work performed during this effort was spent determining the best way to introduce air into the combustion to maximize combustion efficiency. This problem was compounded by the fact that the cooling fan was an axial fan. Axial fans can move a lot of air but they can’t build much pressure. Ultimately it was found that the best combustion was obtained with the air introduced just above the fuel with the air directed downwards towards the fuel rather than upwards.
Maximizing heat transfer into the cooking vessel was accomplished in two ways. First, it was determined that the tip of the flame needed to remain inside the combustion chamber. If the flame tip was allowed to extend beyond the combustion chamber and imping onto the cooking vessel then soot would deposit onto the cooking vessel. Since soot consists of unburned carbon, the presence of soot represent lost energy which could have been used to heat the vessel. The buildup of soot also insulates the pot impeding the flow of heat into the vessel.
The second method used to improve heat transfer into the cooking vessel was the use of a “pot skirt”. Without a pot skirt hot exhaust gases contact the bottom of the cooking vessel and then pass out beyond the perimeter of the vessel where the energy contained in the hot gases are lost. A pot skirt fits around the cooking vessel redirecting hot exhaust gases from below the vessel up the sides of the vessel greatly increasing the heat transfer area.
Conclusions:
This project demonstrates that simple, low cost modifications to cookstoves already popular in the targeted market segment can result in a stove that can both achieve a 35% cooking efficiency, burn clean and produce 8-10 watts of electrical power for the stove user.
Commercialization:
The proof of concept stove fabricated under this effort will be used as a guide to modify Greenway Appliance India’s commercially available “Jumbo” stove so that it can produce electrical power. With Hi-Z’s assistance, Greenway hopes to fabricate 100 of these “Power Stoves” for use in a Market Study later this year.
Results from the 100 stove study will be used to improve the power stove design following which a 1,000 stove study will be conducted between April and June 2018. After incorporating the feedback from the 1,000 stove study, the power stove will be introduced into Greenway’s product line. Based on early market studies, Greenway believes that the power stove could quickly represent up to 25% of their sales, which has been increasing by 15% to 20% per year since their inception in December 2010.
SBIR Phase II:
Biofueled Thermoelectric Cookstove | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.