Solar-powered jet fuel (and diesel, and...)

Sounds kind of backwards, I suppose, but there is in fact research happening on creating jet fuel, and other liquid fuels, using solar energy. One of the big advantages of liquid fuels like gasoline, diesel, or jet fuel is the large amount of energy contained in a small mass—much more energy per gram than batteries. Just recently, in fact, one such research group announced that they had produced a jar of jet fuel, starting from sunlight and CO₂.

Taking out the quotes and the hyperbole about revolutionizing anything, what they've done is still pretty neat: turned CO₂, the low energy end state of carbon-based fuel combustion, back into usable fuel.

Because CO₂ is the low energy end state, to get it back into a high energy form such as kerosene (jet fuel) or diesel, a whole lot of energy has to be put into it. In this case, the energy is solar.

Well, the energy is intended to be solar.

Oily algae

Algae, as well as other biologically sourced feed stocks, has been the subject of a lot of research in oil production, for what should be obvious reasons. There are several things about using some bio-sources that concern me, however. Using food cropland to grow corn or soy intended for conversion to fuel, for one, resulting in less food production (and contributing to higher food prices).

The bio-sources that don't bother me in this way are things like manure or other waste to bio-fuel. Even wood waste and scrap paper can be turned into either oil or syngas (which can be turned into oil, among other things).

But, an interesting comment in a recent press release about oil from algae caught my eye: "byproduct stream of material containing phosphorus that can be recycled to grow more algae."

Chilly chemical properties

Because it's the middle of winter here in Canada, I think today is a good day to talk about refrigeration.

Just kidding. Actually it's because the ISS had to replace a piece of its refrigeration system last week, and I thought that was a good excuse to talk about refrigeration.

Most modern refrigeration involves the chemical property \(\Delta H_{vap}\), or enthalpy (heat) of vaporization. Every substance has a heat of vaporization, and the amount of heat energy required to vaporize a substance is independent of what temperature the substance boils at. To choose a rather extreme contrast, water boils at 100C while lead boils at 1750C, but water requires 539cal/g to convert from liquid to gas while lead only needs 208cal/g, less than half that required by water. This amount of heat does not account for how much is required to get to the boiling point, and if you remember your high school chemistry, the temperature does not change with the additional heat input while it changes from liquid to gas.

The basic principle in use here is that when a substance evaporates, it draws heat energy from its surroundings (or the more familiar form: when you add heat to a substance, it will evaporate), and when a substance condenses, it releases heat energy back to its surroundings. Put an insulated barrier between these two sides of the process, and you have refrigerators, freezers, and air conditioners which get colder "inside" and warmer "outside".

Folded Solar

Solar electrical is pretty exciting right now, I must say. After my previous post on some of the cool stuff coming up in photovoltaics I let it slide for a while and chased other cool news, but this new thing from late December really caught my attention.

I mean, solar panel stickers? Which you can apply to fabric or paper, bend them, and have them still work?

The researchers say that this technique isn't only good for solar panels but also possibly for electronic circuits, transistors, and even LCDs as well. Maybe you really could have a solar powered, electronically active jacket, including flexible display, one day. Imagine, a self-powered jacket that could show you a map of where you are, among other things.

They tested the solar panels to a bend radius of 7mm without any damage. I don't know if it would handle a crease (if on paper) very well, or crumpled-clothes type bends. From the paper, it doesn't look like they tested its bending abilities to failure.

Where to put the carbon?

You may have seen a few articles lately about a nuisance of a chemical called carbon dioxide, namely, that it's the waste product of a number of very common chemical reactions and doesn't itself react with much (other than plants, but that reaction isn't fast or extensive enough to keep up with our current production rate) meaning it accumulates in the environment.

So, we're trying to make sure less of it gets into the environment. One class of methods which you may have heard of is carbon capture and sequestration, where after production it's captured, compressed, and often pumped deep underground—sometimes into retired oil wells, sometimes into the deep ocean, or many other places.

Before it can be stored, however, it has to be captured. Scrubbing can be highly effective at removing CO₂ from smokestacks and other concentrated sources, traditionally with amine solutions. Then there was a new discovery about the CO₂ absorption of polyethylenimine, which was what caused me to start researching this post.

One of the issues with a reaction that is very effective at grabbing a chemical out of the air is making it let go again. Most of the chemicals that are good at grabbing CO₂ are too expensive to use only once. Polyethylenimine is of great interest because it releases the CO₂ easily by heating it up, which can let the CO₂ be collected in concentrated form for use elsewhere.

Solar Technology - The Next Generation

It wasn't so long ago that photovoltaic solar panels were expensive, hard—and dirty!—to produce, inefficient sources of very expensive power.

In the last little while, however, a flurry of advances have improved on all of those problems. So many announcements have come out lately that I've delayed this post repeatedly due to the sheer quantity of new information. But that's not going to stop, so I'll post what I have now, and I may post again later.

For a super-quick summary of first-generation photovoltaic power, the panels were made of silicon using a process that involves toxic chemicals and high temperatures, were very fragile, expensive, and had a low efficiency and limited lifespan.

But now they're becoming cheap, tough, flexible, easy to make, and remarkably efficient and durable.

Weird water

Water, despite the fact that it's incredibly common, is actually a pretty strange compound. Some of its stranger properties make it particularly useful for life, such as the way it switches from getting denser as it gets colder (normal) to getting less dense as it gets colder (not normal) below 4^oC.

A recently discovered and even more recently characterized weirdness of water is that on the nano scale and on hydrophobic surfaces, water spontaneously flows in instead of being expelled the way one would expect based on the usual reaction of water to hydrophobic materials: (blue in the image below)

Airplane-induced snow

An airplane made that hole.

Not by just flying through it and swirling the visible cloud out of the way, that makes a different pattern which doesn't last nearly as long.

It turns out that in certain conditions, airplanes can actually induce rain or snow in a localized region of a cloud, and the precipitation is what clears the hole - the water droplets that make up the cloud fall because of the airplane.

Platinum and power

One of the classes I took in university was on electrochemistry and fuel cells. It was very interesting, but was also a reality check on the hype of hydrogen fuel cells vs. the reality. One item in particular that stood out for me was that the catalyst required for efficient, low temperature hydrogen fuel cell operation was platinum. While platinum isn't the most expensive metal out there, gold having passed it in price not too long ago, it's way up there. As I recall, the raw platinum required to make a fuel cell cost a significant fraction of the cost of a normal car, and that was before they processed it into a useful catalyst. Since then, they've improved the structure here and there and reduced the amount of platinum required bit by bit, but it's still a lot.

Not long ago, however, some researchers in Finland figured out a way to reduce the amount of platinum by more than half.