“…rainy and a low of 2 …” kshhht “…climatologists meeting established a treaty that should further reduce CO2 exhausts by 20% over the next decade…” shh “…and here is their new song fresh from the producer…” kshhhh “…unprecedented flooding for this time of the year…”
“Daaaa, could you please stop tweaking around on MY radio? And could you please drive a bit faster, I wanna bake something for ma before she returns.” She liked radios, something that none of her friends had. They tended to call them relics, which made her like them even more.
With a smile the driver replied “Your radio? Last time I checked, I was driving. And besides, I think we should all follow the recent events that are attributed to human-induced climate changes.”
10 year old Laura gave him the usual you-speak-grown-up-and-I-want-to-listen-to-some-music stare but had learned to not counter his climate comments. The climate. She was cold to the bone, having just come back form the swimming pool trudging through the snow-muck for what appeared to her as ages until reaching their family car. She wouldn’t mind a two degree increase in temperature, who would? Last time she mentioned that, however, a long explanation about flooding, polar ice melting, the disruption of some water current in the Atlantic, pressure changes on the earth’s surface and thus resulting earthquakes and tsunamis that struck with increased frequentness and ferocity had followed. True, there were the recent vids scintillating through the webnews with parts of San Francisco having been displaced by up to 100 metres and talk about it having been avoidable if the polar ice caps were still existing. But then, that city was far away and she sure as hell didn’t feel any tremors in the earth. And according to her geographical sense, the earth’s polar caps were not exactly in San Francisco. She saw no way that some snow melt could be related to all of that. It had turned out time and again that most grown-ups, however, did think like that these days. She decided to distract her old man so that she might get another shot at the radio.
“But, dad, we already drive around in this…” she almost said coffin again, a term impressed on her by her friends for the absolute lack of noise in the vehicle’s interior, “magic machine”. We are already doing something for the environment. Her friends’ elder siblings sometimes boasted with having repaired a real 20th century petrol car sporting the “real combustion sound”. Sure, it made a lot of awful noise but those machines also reeked far worse than any of her failed food preparation experiments – experiments that had triggered the automatic sprinklers at home. Twice already.
Her comment certainly drew another smile from him, he liked the view of children on the world. “Ah, this magic machine runs on fuel cells, that’s why our motor doesn’t make any noise at all. No combustion, no explosion, and an electric motor with a noise level below the wind on our LCD windscreen.”
“Yes, you explained it to me already.”
“But can you remember?”
“Aehhh…” Too late, she realised that she should have used her well-trained convincing of course. Looking longingly at the radio she sighed in anticipation. At least this time, she found herself looking at some small vids called upon the screens by her father. She liked his drawings. The sensible, comprehensible ones, at least.
“Take a look at those vids” he said smiling even more about that answer. She realised with agitation that he had switched to a semi-autopilot mode to turn around with his seat slowing their speed even further, and decreasing her chance for the radio. But for the moment she was nicely distracted.
“The best comparison to fuel cells can be made with batteries. Batteries produce electricity by chemical reactions. In contrary to such systems, fuel cells depend on gases. They use hydrogen as a fuel. ”
Upon these words, a three-dimensional picture of two globes encircling each other appeared on the screen. She had heard about atoms, but no matter how much she had searched, she found herself unable to see these globes with her own eyes and thus doubted they existed at all. She had learned not to mention that, though. She might still see some atoms one day. She had missed the next part of the explanation reflecting on atoms and was only pulled back into reality by the appearance of two different globes and some mentioning of oxygen as the gas on the other side.
“As for utilising hydrogen, vans like ours are usually referred to as hydrogen cars. In their early stages, most people believed we would just burn hydrogen instead of petrol, but the hydrogen is split electrochemically into two protons (a hydrogen atom bereft of its electrons) at the anode. An anode is one of the two electrodes of the cell. In this car, we have a Polymer Electrolyte Membrane fuel cell, the hydrogen is transported through the polymeric electrolyte. It then reappears at the other electrode, the cathode, to combine with oxygen ions (O2-) and forms water, the only waste product. That’s what makes this technology so great, we create mobile electricity using hydrogen and air and produce water. That’s why our car doesn’t stink on the rear side.”
“But what about Sundeep? They refuel vodka in their car”. She always found this explanation of her school friend a bit strange.
Chuckling, he answered “I guess that they might have tried vodka for the fun of it, though what the reformer says to that I’m not sure.” Laura did not know anyone called Reformer and ventured “Who is the reformer”, drawing a louder chuckle form her father. Parents. They always found the strangest things funny.
“A reformer is a machine that converts liquid carbohydrate fuels, for example vodka or more likely methanol and ethanol, into hydrogen. This has the advantage of using liquid fuels that have a large energy per weight density and can be transported and stored easily. Those vehicles, however, need to carry around the weight of that instrument and produce the same stinking exhaust fumes as good old petrol cars – though only about 1% of yonder.”
Yonder. Sometimes he used funny words that she could in turn utilise in school and pretend to know their meaning. But just as she thought she had understood that their car was the best in the world, something she had always know of course, her genitor continued.
“Mind you, the reformers only move some of the dirt back into towns where humankind tried to expel it from after a twentyfold increase in lung cancer in cities across the globe two decades back.” Not that the problem had even been remotely tackled by the banning of all petrol driven mobiles in cities – the occurrence levels merely stabilised. And significant increase in illness was not even the main cause for the ban, but taxpayer demands for an entirely different kind of alleviation derived from the fact that a barrel of crude oil had stepped past the “magical” barrier of $2000US at that time. He never really figured what was magical about it, but the positive change in the city streets was as prominent as in all bars and restaurants after the ban of cigarettes back in the grey past. Well, his grey past at least. “In fact, the production of hydrogen for our car produces just as many waste gases, but it does so concentrated in the green energy centres that have sprung up alongside most of the surrounding water streams where water is split into its components, hydrogen and oxygen, by utilising the energy of the flowing water with small turbines without having to block the stream with a dam.”
Laura was not entirely sure whether that was a good thing, but seeing that their car allowed at least the other kids she knew from school to breath better in their city agglomeration made her feel good. She was drawn again to the two cell drawings in front of her.
“So, what is different between these two cells?”
“Ah, yes. PEMs, as polymer-based fuel cells are usually referred to, operate around the temperature that water boils, 100°C. The electrolyte that conducts the protons is subject to drying and thus cannot be heated far above that temperature. As the name suggests, the electrolyte is a polymer membrane, a thin sheet of plastic if you will it that can conduct protons via an electrical current. As I mentioned before, they flow from the anode to the cathode while the electricity, two electrons per hydrogen atom, travels through an external circuit. At the cathode, the protons recombine with hydrogen ions to form water, the circuit is closed. In the case of our car, the electricity propels an electric motor. Early critics thought these cars were merely larger and slower wheelchairs not knowing that the torque of electric motors, probably best described as accelerating force of a car, exceeds that of any combustion engine by leagues.
“The other cell that you can see are called SOFC, as they are rock solid, or rather ceramic solid and nowadays operate at 500°C. They are entirely made from ceramics and a steady progress in research and development decreased that operating temperature from 1000°C. These high temperatures need materials like certain ceramics that are stable for a long time at these temperatures.”
1000 degrees centigrade, not even the oven at home could go that high, Laura was most impressed by that number. “Is that as hot as on the sun?” she ventured and drew another smile from her begetter.
“Not quite”, he continued, “but too hot to be managed by any fuel cell systems on earth for an elongated period of time. The reduction in temperature allows for certain metals to be used, significantly decreasing costs and increasing the system lifetime. Additionally, electrochemical cells have a higher voltage at lower temperatures.” He avoided any explanation of Nernst, Volta, Maxwell and the likes to support that statement. If these names and their respective ideas ever caught the interest of someone, they certainly did not at that age. Ah, blessed youth.
“In contrast to the PEMs, oxygen atoms from the air are split at the cathode and transported through the electrolyte. As these ions are significantly larger than protons, they need much higher temperatures to be able to move through an otherwise dense ceramic electrolyte. The oxygen ions travel in the opposite direction as the protons in PEMs, forming water at the anode. Other than that, the remaining reactions are exactly the same.
“These high temperature cells can be used in cogeneration where the excess heat of the fuel cell is used to both power a steam turbine and to heat water. This process is called, not too surprisingly, combined heat and power, and is applied in most decentralised residential appliances that are in place in houses. In fact, in our basement, the “fridge without a door” as you put it so nicely, is one of those high temperature fuel cells and the waste heat is used to heat the water for our house. It is not connected to a turbine, though, as it is too small for that. In winter, we use a converter to produce hydrogen from methanol stored in a tank under our basement, but for the rest of the year, the sun does all the work for us, producing hydrogen that we need directly with the solar panels on our roof. It simply electrolyses the water.”
She still remembered last autumn when golf ball sized hail had destroyed most of their glittering roof decoration and the house was ice cold. Everybody was happy for the ancient fireplace that was usually a mere decoration. It had gotten warm again after a visit of a huge truck that had filled the tank under their basement with alcohol. They usually had that truck coming later in the year, something explained to her by her father to be connected to less sunlight in winter and snow on the roof. Only now did it dawn on her that this might be the same alcohol her friend used in his car. Interesting.
“Are there other fuel cells?” she asked after having finished her internal reflections.
“Sure,” was the succinct but nonetheless amiable reply, “there are many, all working at different operation conditions, temperatures and materials. I can show you more about them at home, if you’re still interested, as we’re almost there.” His seat turned and he steered to a halt in their street. Almost home? She realised in not-too-unpleasant-a-shock that the ride had been much shorter than anticipated and very enjoyable. Not that all her talks with her scientist-dad were as easy or enjoyable, but sometimes she could almost see atoms with her own eyes listening to his explanations.
She immediately planned to try to coax her oven into baking at 1000°C, just to see what happens with her bakery. Maybe she could even find a new way to produce energy by that…