Battery Without Electric Current
Think of the word “battery” and electrical storage comes to mind. The elderly lead acid battery, the much younger and energetic lithium battery and even the dry battery. Military people could also think of a battery of guns. But here, we are talking of a different kind of battery. Photo-thermal Battery stores and resupplies energy but without any electric current. It is not electric but thermochemical.
Will a Photo-thermal Battery run the electric appliances in the kitchen? No! Will it run the TV, the lights, or the HVAC? No! Then what use is it? The fact is even the NiCd will not run these appliances except through an inverter-a device which converts DC to AC. The Photo-thermal Battery stores solar light and gives out heat when required.
So What Use Is It?
Where will this battery be used? The battery will be used where enough sunlight is available but little or no electric power. For example, in remote villages of under developed countries, say in Africa and Asia! There is plenty of sunlight, but electric power is either not available altogether, or available for a few hours per day. Cooking and warming does not need electricity, and the Photo-thermal Battery, when it becomes available, will be an excellent solution for these purposes. Why don’t those people burn firewood? They do, but the developed world does not like the greenhouse gases it produces.
The battery can also be used for mass storage of heat, so that heat can be used by power utilities to generate electricity. Since it will provide heat on demand, almost immediate power generation can be done, meeting the short-term power demand during peak hours and special occasions. Placed onto building structures, it could store sunlight more efficiently than the structures alone, and would thus, help stabilize the temperatures inside the building. On a smaller scale, it would not be wishful thinking to hope that thermal storage clothing could soon become available for use in winters and cold climates.
What Is It?
Photo-thermal Battery is not yet a marketable device. But scientists have for long been working hard to design one because of its great potential. As an end-of-the-year gift (for 2017) to the world, scientists at the University of Massachusetts at Amherst have reported a major step forward towards achieving a photothermal battery having promising energy density comparable the lithium battery, the current favorite. The chemical medium used for storage is molecules placed on a scaffold. The scaffold used earlier was carbon nanotubes which were rigid.
The energy density obtained was about 200 Joules per gram. Scientist believed that a flexible scaffold offered by a polymer may perform better. Indeed, it did, as expected. What was not expected was the energy density beyond their expectations. Surprised and pleased, the scientists repeated experiments with various modifications to see what was responsible for this unexpected achievement. It was found that one of the solvent tetrahydrofuran (THF) they used was arranging the azobenzene molecules in a manner which proved to be most favorable to high energy density storage. It is to be noted that this battery is different from the optically triggerable thermal storage which is also being investigated.
Advantages and Disadvantages
One of the advantages of this polymer battery is that in the process there are no bye-products. That means better efficiency of storage and retrieval. Since the active material is common and cheap, the cost of storage is going to be low. And, of course, at an energy density comparable to the Lithium ion battery which is currently the hot favorite. The storage and retrieval need no wiring and conditioning equipment because there is no electricity involved. The disadvantage is, of course, that at the end of 2017, the photo-thermal battery is still in the lab.