We’ve been spending a lot of time on cutting edge solar thermal power projects this week, and here’s yet another new twist: a fuel cell that incorporates solar thermal energy, enabling it to use woody biomass, algae, and even chicken waste for energy input instead of relying on hydrogen gas.
The non-hydrogen angle is significant because although hydrogen is the current gold standard for fuel cells, hydrogen gas is expensive and energy-intensive to produce.
The Solar Power Fuel Cell
There are a number of promising pathways to solar power fuel cells (here and here for example), but the new solar thermal development, a research project at the Georgia Institute of Technology, approaches the problem from a fresh angle.
With a potential market that includes developing economies, the Georgia Tech team set out looking for a low cost, low energy fuel cell that can be scaled down into small units, in addition to its application for large-scale projects.
The idea of using biomass to run a fuel cell is nothing new. The problem is that to break down the carbon bonds in natural polymers you need a catalyst. That currently involves expensive precious metals, typically platinum (although that is beginning to change, for example here).
One workaround is the development of microbial fuel cells, but the current state of technology provides for limited application and low power output (that’s probably going to change, too).
The Secret Sauce For Low Cost Fuel Cells
The key mechanism for the new fuel cell is POM, a polyoxometalate catalyst (polyoxometalate refers to transition metals). POM is both a photochemical and a thermochemical catalyst, so when it is mixed in a solution with ground-up biomass and exposed to sunlight or heat, it goes to work like this:
The POM oxidizes the biomass under photo or thermal irradiation, and delivers the charges from the biomass to the fuel cell’s anode. The electrons are then transported to the cathode, where they are finally oxidized by oxygen through an external circuit to produce electricity.
As for safety (always a consideration with fuel cells), the POM-biomass mixture is inert at room temperature, until exposed to light or heat.
So far, the research team has demonstrated that the POM catalyst can be re-used without requiring retreatment, which helps to cut costs.
Another cost-cutting factor is the durability of POM compared to more expensive metal catalysts, which can be “poisoned” by impurities in biomass.
Aside from solar-enabled power in the form of direct sunlight or stored solar thermal energy, the POM fuel cell could run on waste heat from other processes, helping to create a cost-effective, integrated system.
Don’t expect to stash a supply of wood chips in the trunk of your fuel cell EV any time soon, but according to Georgia Tech professor Yulin Deng, there is a potential for POM-biomass fuel cells to achieve output parity with methanol fuel cells.
About That Methanol…
While we’re on the subject, let’s point out that using methanol (aka natural gas) is hardly a sustainable solution, but that’s only if you’re talking about methanol from fossil sources. Currently in the works are renewable natural gas sources including landfills and livestock operations.
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