Oja: Sunshine in bottles

Energy storage is a very essential focus of the green revolution. With some 174,000 terawatts of power received from the sun continually it is calculated that the atmosphere, oceans, and landmass absorb some 3 850 000 exajoules or 3.85 X 10²⁴ joules. That’s more heat in six months than will ever be obtained from all the hydrocarbons, coal, oil, gas, and uranium stocks combined. It is a massive supply that locally, diminishes under cloud, at night, and is severely limited as seasonal changes occur.

When it comes to solar or wind generated electricity, the battery is the lead construct for storage options. Thermal energy storage currently is largely done with concentrated solar power systems, like Pratt &Whitney Rocketdyne’s CSP Tower, used to heat salts; or by the harnessing of exothermic chemical reactions, such as what is under development at the Swiss Federal Laboratories for Material Testing and Research, where they use sodium hydroxide as the storage medium.

The problem with CSP systems is adaptability and mobility, with exothermal is the dedicated equipment and chemicals required to collect the stored heat. Reliable heat storage should allow for not only space heating, but electrical generation, just imagine if you could bottle sunshine, add a catalyst and receive the warmth of stored energy from some clear day past.

The power of the molecular bond is the focus of some Swedish researches at the Chalmers University of Technology in Gothenburg. There, they have developed a system that is known as the MOlecular Solar Thermal or MOST storage system. As head researcher Kasper Moth-Poulsen explains it, molecules called isomers form bonds between the same atoms of specific

elements. With the addition of heat, the double bonds between two atoms can be realigned to form single bonds with different atoms in the same molecule and in the process, form a different material. In this particular study they use a hydrocarbon, identified as norbornadiene, and expose it to light. This forms a new molecule called quadricyclane, which when exposed to a catalyst, or its base temperature is altered will release the stored heat, effectively reversing the process.

Their latest system generated heat at a 1.1% efficiency using the common elements of carbon, hydrogen, and nitrogen.

The crux of the equation is the number of times this heating cycle can be utilized. So far they have been able to run over 140 cycles without loss of efficiency. When used in conjunction with solar water heating panel arrays, this new system is able to convert more than 80% of the incoming sunlight for around the clock use.

The research shows promise as since 2013 they have been able to develop systems that have increased the efficiency 100 fold, from the original 0.01% produced by their first discovery, to now generate temperatures of over 100 ̊C. Note the use of commonly available elements, versus ruthenium, the rare metal that first lead them into this research. Who knows, down the road we may be able to collect sunshine in bottles.

Lorne Oja is an energy consultant and power engineer. He can be reached at lorne@solartechnical.ca.


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