Hydro rules!

It was one of my favorite subjects when I was specializing in energy technology for my B.Sc. Just my luck to live in a country as flat as it gets!

If you are wondering, the image on the front cover of the book is a Pelton wheel, one of the most efficient turbines. It does require a jet of water (it's an impulse turbine), so it's not really suited for low-head situations, I think. But most modern water tubines can be up to 90% efficient, which is quite high.

You should see if you can find the DVD for the National Geographic channel show "Planet Mechanics", specifically the episode "Lake District Dilemma", where they build a simple water turbine. Maybe you can view it on the NGC website? But in this case, they have about a hundred meters of head to work with, resulting in 10 bars of pressure. That'd run a Pelton wheel all right. Part of this episode is on youtube. Another clip is here. What they were building (not visible in the short youtube fragment) was a crossflow turbine by the way, which is very simple to make, and has a fairly flat efficiency curve over a large range of mass-flow.

You should really read the Wikipedia article on water turbines. For a low-head situation, a Kaplan turbine is most often used, with as little as two feet of head. Unfortunately, unlike a crossflow turbine, a Kaplan turbine isn't easy to DIY.

There is also an EU checklist for small-scale hydro that might interest you.

If you can read German, a very thourough theoretical introduction into the working of flow-machines is "Stroemungsmachinen 1" by Willi Bohl. This is was we used at the Polytechnic. I don't think there is an English translation, though.

Solar developments

There are interesting developments in solar power as well. Some reseachers at Caltech published a paper detailing a 86% efficient solar cell, which is aslo flexible. Of course it'll be years before it is comercially available, but it looks like a real quantum leap forward, if you'l pardon the pun.

Sounds like we found a topic near and dear to your heart. I'll have to check out all of those resources. Thanks for sharing!

I've been hearing things about new solar panels coming down the pipeline for years, but they never seem to reach my price range. I'd heard that the flexible ones were going to be much cheaper soon...still waiting...

Well, thin film solar cells are nowhere near mature yet, AFAICT. There are several competing technologies, each with their own advantages and disadvantages, and there is still a lot of research being done. It might take another decade or so. Nanotech may possibly prove to be an ace in the hole, but that also isn't mature enough yet. But as I see it, electrical energy storage (i.e. batteries) is the bigger problem. The energy density of batteries are kinda pathetic. And I'm not seeing quantum leaps of improvement there yet.

And making something in a lab is one thing, making it work efficiently in a full-scale production environment is something completely different. Been there, done that & got the gray hairs to prove it.

What I would like to see is artficial photosynthesis; creating carbohydrates (preferably something easily used like methanol or ethanol or biodiesel) from water, CO2 and sunlight. That would go a long way towards getting rid of the energy storage problem. Unfortunately at this point we don't even understand how photosynthesis works, so it will take a while. Maybe farms with modified algae or bacteria will be a solution.

Sounds like I'd better not hold my breath.

I like your idea of artificial photosynthesis, or even using algae or bacteria to turn the sun's energy into carbohydrates. (I guess that's really what biofuel is, right?)

Mark and I were talking about how great your energy comments were while we were eating dinner, and we were wondering if you'd have any interest in putting together a lunchtime series for us. The topic could be your choice, but something in the sustainable energy field would be great. Don't feel obliged, but I think you have a lot to share with people (who don't necessarily read comments.)

It would be a pleasure. I cannot promise much wrt delivery times. My time for projects like this is mostly restricted to weekends, and it takes time to do proper research. I do hate delivering shoddy work. (which isn't to say that I don't make my share of mistakes. )

A more philiosophical question is what angle to take? I'd value your (and other commentators) input on this.

If you look at it from a purely economical perspective, alternative energy still seem to be a losing proposition. At least when I last looked at solar panels, the time to make the investment pay for itself is much longer than any realistical lifetime of the components.

Of course, if being on the grid isn't an option because of your location, that changes the equation. But you'd still want the most bang for your buck.

Another angle is total lifecycle analysis. This means looking at all the materials that have gone into producing your alternative energy solution (which is very involved) and check if your solution can generate more energy over its lifetime than has been spent making it.

Environmental concerns are also something to look at. E.g. a lot of solar panel rely on semiconductors, which need a huge and resource consuming plant to produce. Lots of water, nasty chemicals, rare earth metals.

A subject that is dear to my hart is efficiency. If you get your energy from the sun or the wind, should you care about conversion efficiency? (I think you should). A directly connected subject is installation size. Most energy conversion apparatus works most efficient and cost effective when it's large. There are usually fundamental reasons for this. Anne, you've already touched upon this subject by mentioning the folly of using electricity to generate heat.

And what about nuclear power? I know that most alternative/environmentalist/whatchamacallit people are dead-set against it. I think that is rather narrow, and a knee-jerk reaction if you really think it through. Here in the Netherlands, the environmentalist movement used to hand out stickers with the image of a smiling sun with the text "nuclear energy, no thanks". Which is extremely ironic since the sun is the most stupifyingly large nuclear reactor you'll come across within several lightyears! But even fission has its place! Fission of radioactive materials in the earths core has kept the core liquid, and released huge amounts of energy. Without the liquid core our Earth's magnetic field which protects us from high-energy radiation would not exist, and Earth would look more like Mars. If you think it through, essentially all our energy ultimately comes from fusion or fission. E.g. if you use geothermal energy, you're essentially using nuclear fission power! The so-called fossil fuels are nothing more than stored solar energy. How many people would be surprised to learn that?

A disscussion about energy sources versus energy carriers also seems in order. A lot of people do not realize there is a difference. But there is, and it has huge implications.

(I'm just realizing I might have just written the first installment, more or less. I do tend to get carried away when the subject interests me.)

Any thoughts?

Thank you for being willing to write one! Don't be overly concerned about the timeline --- I'm happy to get it whenever it arrives.

I'll let other people chime in here too, but here are the things I'm most interested in:

1. You mention that solar, at least, still doesn't make sense from a cost point of view, which is what I keep coming across when I crunch the numbers too. Do you know if any of the other options (hydro, wind, anything else I'm not thinking of) do actually save you money in the long run? (Since I'm on the grid, I'm most interested in this from an on-grid point of view. But that can include net metering since we have that in Virginia, and many other states do now too, where we can put any extra power into the grid and get paid by the electric company for that. If we didn't have batteries at all and just plugged straight into the grid as our battery, would that make any of the options more fiscally responsible?)

2. All of the options I read about are AC options. What do you think about DC or mechanical energy options? Would it make sense to buy LED lights that can run on DC energy rather than converting to AC and losing efficiency in the process? Are there any obvious things we could hook directly into a turning wheel from hydropower (like grain grinding used to be, but on a smaller scale with appliances we actually use in daily life?)

3. I'm not as interested in nuclear just because I'm thinking of things that can convert to the small scale. But that leads me to two related questions: Which grid-scale electricity generation option do you think is the most environmentally responsible? Are there any small-scale options that use nuclear energy or methods that we don't usually think about to make electricity?

4. I don't know the difference between energy sources and energy carriers, so if that's important, you'd better talk about it.