Environ. Sci. Technol. 2008, 42, 8591–8596
Batteryless, Wireless Sensor Powered by a Sediment Microbial Fuel Cell C O N R A D D O N O V A N , †,‡ A L I M D E W A N , ‡,§ DEUKHYOUN HEO,† AND H A L U K B E Y E N A L * ,‡,§ School of Electrical Engineering and Computer Science, School of Chemical Engineering and Bioengineering, and Center for Environmental, Sediment and Aquatic Research, Washington State University, Pullman, Washington 99164-2710
Received June 25, 2008. Revised manuscript received August 27, 2008. Accepted September 8, 2008.
Sediment microbial fuel cells (SMFCs) are considered to be an alternative renewable power source for remote monitoring. There are two main challenges to using SMFCs as power sources: 1) a SMFC produces a low potential at which most sensor electronics do not operate, and 2) a SMFC cannot provide continuous power, so energy from the SMFC must be stored and then used to repower sensor electronics intermittently. In this study, we developed a SMFC and a power management system (PMS) to power a batteryless, wireless sensor. A SMFC operating with a microbial anode and cathode, located in the Palouse River, Pullman, Washington, U.S.A., was used to demonstrate the utility of the developed system. The designed PMS stored microbial energy and then started powering the wireless sensor when the SMFC potential reached 320 mV. It continued powering until the SMFC potential dropped below 52 mV. The system was repowered when the SMFC potential increased to 320 mV, and this repowering continued as long as microbial reactions continued. We demonstrated that a microbial fuel cell with a microbial anode and cathode can be used as an effective renewable power source for remote monitoring using custom-designed electronics.
Introduction
waters are monitored using wireless sensors, microbial fuel cells can be used to produce energy to power them (3). Several researchers have attempted to demonstrate the possibility of using a sediment microbial fuel cell as the power source for a remote sensor. When a microbial fuel cell is operated in a natural water source such as a river, lake, or sea and derives electrons from microbial reactions on the anode buried under sediment it is called a sediment microbial fuel cell (SMFC) (4-6). Figure 1 shows a SMFC described in many literature studies (7-9) as well as in this study. For a SMFC, the graphite buried under sediments serves as the anode. Microorganisms in the sediment colonizing the anode surface oxidize natural organic chemicals to derive electrons (7, 9). The graphite (8, 9) or stainless steel (10) electrode in the water above the anode serves as a cathode reducing oxygen. If manganese-oxidizing microorganisms are present in the water, they deposit manganese oxides on the cathode surface, increasing the potential toward a more cathodic direction (10-13). The oxidation/reduction cycle of Mn catalyzes oxygen reduction and generates a higher cathodic current (13). There have been many attempts to demonstrate that SMFCs can produce electricity. However, most of them tested SMFCs in marine environments. Reimers et al. (2001) simulated the marine environment in a laboratory and showed that the power produced by microbial fuel cells could be sufficient for oceanographic instruments deployed for long-term monitoring (7). Tender et al. (2002) observed a potential gradient between an anode buried in marine sediment and a cathode in overlying seawater. They deployed two SMFCs in coastal marine environments, in Tuckerton, New Jersey and Yaquina Bay Estuary, Oregon, and showed the possibility of power generation from marine sediment (6). Reimers et al. (2006) showed that a cold seep has the potential to provide more power than neighboring ocean sediments in Monterey Canyon, California (8). These studies demonstrate that microbial fuel cells deployed in natural waters can produce enough energy to operate sensors requiring low power. However, it is worth noting that all these microbial fuel cells produce a maximum cell potential around ∼800 mV and that they have not yet been used to power any electronic device. As an alternative to the studies described above, our group previously used a microbial fuel cell with a microbial cathode
Wireless sensors are attractive in a wide range of applications such as environmental monitoring, oceanographic study, and military tactical surveillance for real-time data acquisition from remote locations (1, 2). In the last few decades, wireless sensor networks and the related electronics have been advanced significantly because of their use in remote monitoring. Despite significant advancement in electronic components, the lifetime of remote wireless sensors is limited by the power source (2). Traditionally, wireless sensors are powered by dry cell batteries (1). The use of dry cell batteries is popular but problematic because of their limited lifetime. In remote locations replacing the batteries is costly, timeconsuming, and impractical. A possible solution to this problem is to produce power where it is needed. When natural * Corresponding author phone: (509) 335-6607; fax: (509) 3354806; e-mail:
[email protected]. Corresponding author address: School of Chemical Engineering and Bioengineering, P.O. Box 642710, Washington State University, Pullman, WA 99164-2710. † School of Electrical Engineering and Computer Science. ‡ School of Chemical Engineering and Bioengineering. § Center for Environmental, Sediment and Aquatic Research. 10.1021/es801763g CCC: $40.75
Published on Web 10/22/2008
2008 American Chemical Society
FIGURE 1. A sediment microbial fuel cell (SMFC) with microbial anode and cathode provides energy for the power management system (PMS). VOL. 42, NO. 22, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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and a sacrificial anode to power a wireless temperature sensor (10). This configuration allowed us to increase the cell potential above 1.2 V to power a sensor with appropriate off-the-shelf electronics. However, when electrons are derived using a microbial anode the cell potentials are always below ∼800 mV, as described in the literature (4, 6, 9, 14). This makes it impossible to power sensors using Shantaram et al. (2005) electronics utilizing microbial anodes. Moreover, the use of sacrificial anodes limits the lifetime of microbial fuel cells as a power source (10). As stated in published literature, it is necessary to use a microbial fuel cell which derives electrons from microbial reactions to power a remote sensor for its lifetime (3, 4). To the best of our knowledge, there has not been a wireless sensor powered directly from a SMFC like that shown in Figure 1. Our goals were 1) to develop a power management system to power a wireless sensor using the SMFC given in Figure 1 and 2) to design a SMFC to test the usefulness of the developed PMS for powering a wireless sensor. However, there were two main challenges to using a SMFC as the power source. 1) Low Potential. A SMFC produces a low potential at which most circuitry does not operate (0-800 mV). Generally, to increase the potential of microbial fuel cells, they can be connected in series (15, 16). However, when SMFCs are connected in series, the overall cell potential does not increase because all the electrodes are immersed in the same electrolyte solution (natural water), forming a short circuit. Practically, the maximum potential can never be increased above the maximum potential a single SMFC can produce, ∼0.8 V. Moreover, this maximum potential does not remain constant when a load is applied: the cell potential decreases to a low value depending on the amount of load (14). As an example, Dumas et al. (2007) observed a maximum of 0.1 V in their marine sediment fuel cell when a load (33Ω) was connected (14). Since low-power electronic devices typically require an input voltage of 0.9 to 1.8 V, it was necessary to increase the low potential (
