Batteries for efficient energy recovery from wastewater
Abstract/Contents
- Abstract
- Wastewater treatment is an energy intensive process, consuming ~ 3% of U.S. electricity production. This is despite the fact that considerable energy in wastewater is potentially recoverable. This energy includes the chemical energy in reduced organics and nitrogen, and, at coastal treatment plants, the energy of the salinity-gradient between wastewater effluent and seawater. This thesis focuses on development of two battery technologies, the "mixing entropy battery" (MEB) and the "microbial battery" (MB), to enable efficient recovery of energy from salinity gradients and the organics in wastewater, respectively. In initial studies, the MEB is evaluated with wastewater effluent as the source of freshwater and different operational parameters are investigated. The MEB flushed with wastewater effluent achieved an energy recovery efficiency comparable to that of a MEB with river water flushes. With 12 cells in series, an energy recovery efficiency of 68% was achieved. Two operational trade-offs were identified: (1) energy recovery efficiency and capital investment, and (2) power output and energy recovery efficiency. In follow-up studies, new electrode materials are evaluated for the MEB. Prussian Blue (PB) and polypyrrole (PPy) were employed as the cationic electrode and the anionic electrode, respectively. Both materials are low cost ($1/kg for PB and $3/kg for PPy) and showed desirable electrochemical properties, including redox reactivity with Na+ or Cl-, rapid potential response to the salinity change, excellent cycling performance, and stability in aqueous environments. These novel electrode materials also enabled another significant breakthrough. Because the potential range of the PB electrode and the PPy electrode are similar, the MEB can be operated without the charge step. The charge-free MEB requires no additional energy investment and produces energy during both wastewater effluent and seawater flushes. The voltage efficiency of the charge-free MEB was similar to that of the original MEB that required a charge step and used inferior electrode materials (89.5% and 97.6% voltage ratio). Moreover, the MEB was stable for 50 cycles with less than 7% loss in energy production. In a set of final experiments, use of PB is evaluated in a MB as a low-cost cathode material to replace Ag/Ag2O. Regeneration of the PB electrode was straightforward and required no energy input. By exposing the PB electrode in air for 100 min, 80% of the original capacity was restored. The process was rapid; the PB electrode discharged in a MB for 8 min after exposing in air for only 5 min. The energy recovery efficiency of the MB with a PB cathode was comparable to that of the original MB with Ag/Ag2O cathode (18% to 33%, depending upon operating conditions) with stable power output for 20 cycles.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Ye, Meng |
|---|---|
| Associated with | Stanford University, Department of Civil and Environmental Engineering. |
| Primary advisor | Criddle, Craig |
| Thesis advisor | Criddle, Craig |
| Thesis advisor | Cui, Yi, 1976- |
| Thesis advisor | Kitanidis, P. K. (Peter K.) |
| Advisor | Cui, Yi, 1976- |
| Advisor | Kitanidis, P. K. (Peter K.) |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Meng Ye. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Meng Ye
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...