Fossil fuels have ushered in the modern industrial age, but carbon-neutral methods of electricity production are needed for the future. Salinity gradient energy (SGE) is one approach to produce electricity that is based on using two solutions with large differences in salt concentrations. SGE sources include naturally occurring water sources with different salinities, such as: river water and seawater, and salt brines and seawater or river water; or treated used waters (wastewaters) prior to discharge into the ocean and seawater. Many large cities are located in coastal areas, and thus have good access to seawater. Several methods have been technologies have been proposed to capture SGE, called “blue” energy technologies such as reverse electrodialysis (RED), among others listed on the Technologies link.

Solutions with different salinities can also be produced for SGE electricity production, for example by using thermolytic salt solutions and waste heat. At Penn State, we have examined several of these different “red energy” technologies that use waste heat or natural heating/cooling sources. For example, ammonium bicarbonate (AmB) is a salt that can be distilled from water at low temperatures (45 degrees Celcius or higher) to make highly saline solutions and low saline solutions. These can then be used in SGE technologies to make electricity. Another approach recently invented by the Logan group was a thermally regenerative ammonia flow battery (TRAB). Waste heat is used in this process to produce highly concentrated ammonia solutions that can be stored for use when needed to make electricity, making it both an energy conversion process (heat to electricity) and an energy storage device.

Through links on this website you can learn more about the SGE and TRAB technologies through links to descriptions and photographs of systems used for each technology, as well as through power point presentations and videos. For researchers interested in using these systems, we also provide a “make one” page for some of these technologies.

Other renewable energy approaches are also being developed at Penn State based on harvesting organic matter in wastewaters and waste cellulose sources to make electricity or biofuels using microbial fuel cell (MFC) technologies. To find out more about these “green” technologies, visit the Bioenergy or the MFC pages on the Logan homepage.


Prof. Bruce Logan: research areas of bioenergy production using microbial electrochemical technologies, wastewater treatment and bioremediation.  [Logan-CV] [Logan Google scholar]

Prof. Chris Gorski: Environmental chemistry, with emphasis on mineral formation and transformation reactions that affect environmental pollutant fate, and applications in energy production, storage, and recovery. [Gorski Google scholar]

Penn State activities & centers

Bioenergy research (Logan lab): Microbial fuel cell technologies

IEE: Institutes of Energy and the Environmental, research on all aspects of energy and environmental work ongoing at Penn State.

MRL: Materials research: multidisciplinary education and innovations in materials

Huck Institutes: Interdisciplinary life science research and education

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