While running the reforming component required a significant portion of energy from the grid, adding a solar thermal component to the reformer was found to be a more efficient way to capture solar energy—thereby reducing the energy needed from the grid—than adding a photovoltaic cell array of the same size. Domestic implementation of solar thermal reforming, in conjunction with a hydrogen fuel cell, presents a possible way to reduce GHG emissions; the emissions per unit of power from the reforming process are less than those generated by conventional power production.
Solar steam reforming of bioethanol offers a sustainable way to domestically produce hydrogen for use in a hydrogen fuel cell. However, the intermittency of solar energy within a given day prevents the solar reformer from operating at full efficiency, affecting the rate of hydrogen production. A study in Japan found that even with the intermittency of available solar energy a domestic hydrogen reformer—running on a combination of solar and electrical power—operated at above 40% for both cloudy and sunny days. The GHGs emitted during the reformers’ operation were found to be 19% lower than conventional commercial power generation. Furthermore, the percent utilization of solar energy by the 2 m2 collecting area of solar reformer was superior to that of photovoltaic cells.— Tim Fine
Shin’ya, O., 2009 Hydrogen production characteristics of a bioethanol solar reforming system with solar isolation fluctuations. International Journal of Hydrogen Energy 34, 5347–5356.
Shin’ya Obara at the Kitami Institute of Technology’s Department of Electrical and Electronic Engineering studied the efficiency of a domestic bioethanol reformer used in conjunction with a hydrogen fuel cell. Two solar collectors measuring 1 m2 were used to collect the solar energy for vaporizing the bioethanol feedstock and operating the solar reformer. Gaps between the solar energy available and the energy required for reforming were met with power from the grid. The results were obtained using the meteorological data from March 1 and August 23, 2007.
The uneven heating of the catalyst in the solar reformer leads to a drop in the efficiency of the reactor, as it prevents the decomposition reaction from reaching completion. Consequently, the changes in solar energy available due to cloud coverage can have a significant effect on the efficiency of a solar reformer. The study looked at the theoretical operating results of both a cloudy and sunny day in Sapporo, Japan by using the meteorological data from March 1 and August 23 of 2007. The reforming component operated with an efficiency of 47% on the cloudy day, March 1, and 42% on the sunny day, August 23. While efficiency of the reactor was lower for the sunny day, the longer daylight hours—there were nearly 2 more hours of sunlight on the 23rd—meant that the reactor produced 17g hydrogen and 0.5 kWh more than it did on the cloudy day—the 1st. Considered as a fraction of the power demand for each day, the reactor produced 21.4% and 25.3% of the energy required to run the reactor for March 1 and August 23rd respectively.