Progress 09/15/06 to 08/31/11
OUTPUTS: Carbon dioxide (CO2)is an important attractant for a variety of insects. Sources of CO2 are few and often cumbersome, specifically for field work Our research was dedicated at developing another CO2 generation technology, aimed at being more user-friendly. The selected approach, electrochemical stripping of CO2 from carboxylated organic acids, was attempted on formic and oxalic acid, with emphasis on oxalic acid, a solid, easy to store and transport. Practical implementation of the concept required the development of electrolyzers capable of generating up to 15 liters/hour of CO2, a rate generally accepted for mosquito trapping. Success was, in large part, predicated on an electrochemical process that would be stable and not yield undesirable by-products. It further required establishing correlations between electrolyzer voltages, currents and operating temperatures. Since the process requires a power source, we investigated the usefulness of a variety of sources, ranging from primary and secondary batteries to AC/DC converters to regulated power supplies and ultimately photovoltaic solar panels. The scope of the project was extended to include small CO2 generators (less than 1 liter/hour) and large systems (over 60 liters/hour). The results of this work were published/patented and discussed, on a selected basis, with potential users involved in gas processing, vector-control and insect (mosquito, bed bugs) management. Documentation for public release was prepared and the technology will be presented at the Fbruary 2012 AMCA (Am. Mosquito Control Assoc.) meeting in Austin, Texas. PARTICIPANTS: H. Maget, PI, was instrumental in developing electrolyzer and systems concepts. M. Johansson was active in implementation of these concepts. J. Goldberg and R. Houk participated in developing the systems electronics for the solar PV panel-operated system. TARGET AUDIENCES: By expanding the scope of the project to include miniature and large CO2 generators, the targeted audiences include: gas processors providing on-site CO2, entomologists involved in insect trapping (mosquito and others) and the military interested in field deployment of CO2 sources, simplifying materiel logistics. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
We were able to demonstrate that oxalic acid (OA) is a suitable source of CO2 and that its electrochemical break-down results in the production of pure CO2 without residual products. In essence, OA is equivalent to dry ice without the issue of sublimation. The process starts below 1.0 volt, compatible with the use of commercial batteries. The decomposition rates are substantial, exceeding 2 liter of CO2/hr-cm2 of electrolyzer area. Single cells and multi-cell stacks, generating from 20-300 cc CO2/minute, are used to demonstrate the versatility of the technology. Simultaneously we have developed an electrolyzer refill consisting of OA bricks with a toroidal geometry allowing the electrolyzer to be located within the doughnut hole, thereby allowing for instantaneous start-up. An accrued benefit of this technology is the electronic control of the CO2 generation rate. A simple dial allows for rate changes, including programming its changes. The modular electrolyzer operates from wall power or batteries or solar panels. A photovoltaic solar panel-operated field systems was assembled and demonstrated to operate steadily including absence of sunlight during two consecutive days. This technology, a departure from conventional CO2 sources, offers entomologists a simple, effective means to incorporate the generator into mosquito (or other insects)trapping systems.
- Maget,H.J.R. 2006, On-site Generation of Carbon Dioxide", Gases and Technology, July/August 2006: 16-19
Progress 09/15/07 to 09/14/08
OUTPUTS: An experimental portable solar-photovoltaic powered CO2 generator was designed, assembled and shipped to CMAVE, ARS, USDA,Gainesville, Florida, on May 9, 2008, for mosquito trapping field tests. The system consists of three key sub-assemblies: the solar panel, the electronic control box and the CO2 generator bucket.The Kyocera 50 watts solar panel is mounted on a 3-foot high metal frame fitted with casters. The panel can be tilted from a zero-angle (for shipment) to about 45 degrees; a compass is attached to the frame. The control sub-system holds a SLA Xtender PVX-490T 12 volts battery with a rated storage capacity of approximately 54 A-hrs, a solar energy conditioning unit (Steca Model PR 1010) and the load current control unit specifically designed for interface with the CO2 generator. The load control unit is fitted with a digital LCD display that indicates the load current, i.e. the rate of CO2 production. A manually adjustable knob allows for CO2 generation rate settings of zero (off) and five identical incremental rates from 6 to 30 L/hr. All extraneous metering equipment (valves, flowmeters, etc.) is not required by these types of systems. The CO2 generator sub-system consists of a sealed bucket holding the electrochemical stack and a supply of oxalic acid "briques" adequate for a month of operation of the generator at an average rate of 12 L/hr of CO2. The bucket is completely sealed except for two protruding terminals which are polarity insensitive. The system, as shipped, is ready to operate. It requires only the addition of a pint of water before start-up. Results of the mosquito trapping field tests by CMAVE/ARS are not available at this time. PARTICIPANTS: USDA's ARS Dr. Daniel Kline participated in this project as a resource for system development. He will, during the latter part of 2008, conduct mosquito trapping field tests by attaching trapping hardware to the solar-powered CO2 generator. A manual entitled "Portable solar powered CO2 generator. Experimental Unit Instructions Manual" has been provided to Dr. Kline. TARGET AUDIENCES: The targeted audiences are mainly mosquito monitoring individuals, institutions or agencies interested in replacing CO2 tanks, or dry ice, or propane tanks, currently used as a source of CO2. Additionally, DoD would have an interest since solid oxalic acid, replacing heavy storage tanks, would offer considerable logistics advantages for use in U.S. and overseas facilities. Eventually, on-site, on-demand, generators of CO2 will also have other commercial applications. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
The system was tested at Med-e-Cell's facility in San Diego prior to shipment. The system was operated at the discrete rates of 6, 12, 18, 24 and 30 L/hr, i.e. in excess of the targeted 12 L/hr. To avoid excessive depletion of the battery it is preferred to hold battery discharge to 50% of its state of charge, although deeper occasional discharges are acceptable. At rates of 12 L/hr or less, the duration of operation without recharge (days of cloudiness)can be from 2 to 4 days. At higher rates the solar panel needs to be recharged daily, or the Steca needs to be set on a timing function rather than on dusk-to-dawn operation. Although mosquito trapping takes place, generally, from sunset to sunrise, the system can be tested during daytime. The bucket holding the electrochemical CO2 generator can be pressurized to about 5 psi. A pressure release valve will kick in at 10 psi. At that pressure the bucket will start deforming and the seals probably fail. The generator voltage can be monitored by using a voltmeter or data logger at its terminals. The voltages that have been observed are less than 12 volts under any operating conditions, except at 30 L/hr at cold start. This will not affect the generator. If voltages exceed 15 volts the generator will automatically shut-down. It is re-started by pushing a re-set button.The system is easy to operate. It will function without attention for durations set by the availability of the oxalic acid source.
- No publications reported this period
Progress 09/15/06 to 09/14/07
OUTPUTS: A solar-photovoltaic powered electrolysis system was developed by Med-e-Cell. The system consists of two solar panels, an electronic control unit for the transfer of solar energy to a battery, an electronic control module controlling the current output to the electrolyzer and the electrochemical CO2 generator. Although the targeted CO2 generation rate was 12 L/hr (0.05 lb/hr), the generator has been designed to generate up to 30 L/hr (0.12 lb/hr). Extending the capacity has also resulted in the need for larger solar panels. The targeted daily duration of operation, during nightime, of the generator is 10 hrs, while the solar panels collects energy during daytime. A novel process has been developed to produce solid oxalic acid "briques" weighing about 2 kgs. Assembling four such briques into the electrolyzer will allow autonomous operation for about one month, provided adequate solar energy can be harvested to sustain operation. The electrolyzer stack, the key component,
consists of 10 cells, series-assembled. A current load of 1.32 amps is adequate to achieve the nominal CO2 generation rate. The projected area of the unit is 6cm by 7 cm, the height is 3.5 cm. The unit has been designed to be compatible with a conventional 12 volts lead acid battery. Solar panel size and number have been selected to provide the necessary power to the battery even after a sustained period of cloudiness. Two 50 watts Kyocera panels have been selected.They are mounted on top of a pole facing south at a tilt angle of 30 degrees, specific to San Diego. The electronic controls consist of a Steca PR 1010 unit available commercially and a load controller based on Linear Technology model LTC378 Buck-boost controller, configured as a constant current source. At this time it seems that the system will achieve most goals and targets established at the start of the project. The system has been shown to Dr. D. Kline (USDA-ARS Fly and Mosquito Unit); a similar unit will be provided
to him the summer of 2008 for field studies in Gainesville, FL. time
PARTICIPANTS: Metrionix, a small business, has participated in the development of electronics for the system. Jack Goldberg, President of the company, has considerable experience in the design of digital electronics and some experience in electrochemical engineering. USDA's ARS Dr. Daniel Kline participates to this project as a resource for the design of the system as applicable to mosquito monitoring and later , next summer, will conduct the field tests.
TARGET AUDIENCES: The targeted audiences are mainly mosquito monitoring individuals, institutions or agencies interested in replacing CO2 tanks, or dry ice, or propane tanks currently in use as a source of CO2. Additionally, DoD would have an interest since solid oxalic acid, replacing heavy tanks, would offer considerable logistics advantages for use in U.S. and overseas facilties. Eventually, on-site, on-demand, generation of CO2 will also have other commercial applications.
System experimentation, using "dummy" loads rather than the electrolyzer have shown that one single 50 watts panel will be adequate to operate the generator at the nominal targeted rate of 12L/hr for period of up to 10-12 hours per night. That performance can be sustained even after two days of continuous cloudiness. For extended cloudiness periods the sytem will be progressively derated to protect the 55 A-hr storage battery. Larger batteries will allow to sustain operation for longer durations of cloudiness. When both panels are in use, the generation rate of CO2 of 30 L/hr is sustainable for similar conditions. However a larger battery will be required. Tests of the electrolyzer have shown that even at 3.3 amps (needed to achieve 30 L/hr) the voltage level is still below 12 volts. That result points to the systems capability to operate in a wide dynamic range of CO2 generation rates. Currently the load control unit can be operated at discrete, manually controlled,
rates of 0, 12, 18, 24 and 30 L/hr. The next generation of load controller is planned to be a digital unit with additional features including programmable time cycles and variable generation rate cycles. The significance of this work and results will be confirmed if the field tests show, conclusively, performance comparable to that of conventional CO2 sources.
- "On-site Generation of Carbon Dioxide", H. Maget, Gases aand Technology, July/August 2006, pp. 16-19