Even as a young and naïve high-school student, sustainability has always been of great interest to me. During my senior year of high school, I competed in my school’s science fair. I utilized an extensive set of complicated gadgets and devices to determine whether or not hydroelectric power was a viable candidate in my hometown. Just for reference, I grew up on the island of Saint Croix in the United States Virgin Islands. However, it was appalling to me to think that not a single person, business, or other entity had thought it wise to invest in hydroelectric power. Based on the results of my experiment, which earned me a free trip to the International Science and Engineering Fair (ISEF) sponsored by Intel, the island of Saint Croix was fully capable of utilizing hydroelectric power to a great degree of success.
This continued interest in hydroelectric power brought me to an article entitled “Water Salination: A Source of Energy.” The concept of salination power is perhaps even more obscure and unprecedented in the United States than hydroelectric power. The basic premise is rather innovative (though I do not fully understand the science behind it, even after reading its description): through the principle of osmosis, mixing freshwater and saltwater at constant temperature releases energy, a process that is reversible with heat.1
This is a pretty exciting concept, because this process is renewable, and also nonpolluting due to the only byproduct being brackish water. The article also claims that, as a resource, salination power is comparable to hydroelectric power in magnitude.1 Obviously salination power cannot be applied in all situations, such as estuarine environments, as the process necessitates the mixture of both fresh and saltwater.1 However, in controlled scenarios, I can imagine this unique energy source can prove to be quite fruitful.
One might wonder: what is the benefit of salination power over solar, hydroelectric, geothermal power, etc.? As long as we are not being mutually exclusive with our choices of renewable energy, not investing in salination power would cause us to miss out on 120 x 109 watts of energy every second, a number that is several times the current U.S. water power consumption, and almost equivalent to the total U.S. hydroelectric potential.1 That is how valuable a source of power that water salination can potentially be.
Of course, there are also several drawbacks that must be considered in the usage of saliantion power. There are a few sources of energy loss that can occur in a practical salination device. The first is that the mixing of saltwater and freshwater represents a reduction in effective osmotic pressure, which lowers our efficiency. Secondly, sediments and solutes that are found in flowing freshwater sources can accumulate within the machine, reducing system efficiency. There is also the fact that the device must work against a hydrostatic pressure gradient. This will limit the pump rate and effective power. Though there are these considerations, I believe that salination power is worth looking into further, and at the very least, an interesting concept for the sustainability-minded.
- Norman, Richard. “Water Salination: A Source of Energy.” Science, New Series, Vol. 186, No. 4161 (1974): pp. 350-352. Web. 26 Sept 2013.
Thesis Research Design Seminar 2013 
Interesting, I wonder why salination isn’t more widely used then? Do you have any idea why? Also, I wonder what the urban design/architectural implications of having a salination plant are. What are sizes of plants that are required? You mentioned that sediments and solutes accumulate, so I wonder what the design implications of that are? If this is an interesting idea in your biophilic explorations, it may be good to start thinking about these questions.