by Emil Morhardt
If there’s a need for electricity, but there aren’t any power lines nearby, the approach of choice today, in sunny climes, is photovoltaic (PV) panels connected to batteries. But the total amount of electricity that can be stored is then dependent on the number batteries, and if a relatively large amount of storage is needed, this could be prohibitively expensive, heavy, and not very portable. With the advent of hydrogen fuel cells small enough to fit into an automobile and operational at low temperatures, perhaps a fully self-contained electrical generation system could be based on PV panels electrolyzing water to make hydrogen gas, which could then be stored in low-pressure tanks in amounts as large as needed. That’s what Cabezas et al. (2014) decided to experiment with.
The impetus was that in their country, Argentina, there is much need for off-the-grid electricity in isolated communities, military outposts, and mountain huts. The authors put together the system shown above using commercially available components and their own electrolyzer (in which the electricity from the PV panels splits water into hydrogen and oxygen gas) and fuel cell stack (which recombines the hydrogen and oxygen to produce electricity). The gases were stored at a pressure only slightly higher than atmospheric pressure, ruling out the need for expensive compressors or high-pressure tanks.
The whole system was light-weight, easily transportable, and inexpensive, and seems to be a good candidate for development into a unified module that could be purchased off-the-shelf for off-the-grid needs.
The authors suggest that their system has the advantage of not incurring the energy losses involved in charging and discharging batteries but they did not do an analysis that directly compared the cost or efficiency of their system to a reasonable battery storage alternative.
Cabezas MD, et al., Hydrogen energy vector: Demonstration pilot plant with minimal peripheral equipment, International Journal of Hydrogen Energy (2014), http://dx.doi.org/10.1016/j.ijhydene.2014.09.040