Nanogeneration camping: A tealight-powered LED lantern

When we go camping we often meet Paul from Fireside. He imports wood-burning stoves and deals with a lot of outdoor stuff, and always has interesting camping tackle. People send him samples that he likes to try out in the field before unleashing them on his customers. A couple of years ago he had a twig burner with a thermocouple that could charge a phone. He seemed to be spending most of the time feeding twigs to the burner, and drinking a lot of tea from the kettle on top. I didn't notice him bringing this bit of tackle the next time we saw him.
This year he had a tea-light LED lamp. Somebody is raving about it here in the Chronicle Herald. That's a Canadian publication so it may be Chronic le Herald and I'm misreading the URL.

It uses a thermocouple to convert the heat from the tea light into electricity, which drives eight LEDs. It certainly is bright. The LEDs are something like 20 times brighter than the candle. The problems with a lot of LED camping lights are that they don't put enough light out, and the light is going in the wrong direction. The Tilly lamp makes a lot of sense if you have to carry around a light source with liquid fuel, but designing LED lights in that shape seems a little strange. On a campsite you don't really want the light shining out in all directions. You often want it pointing down at the table you're eating from, or the surface you're working on. This light is both bright and allows the light to point down towards the table.
And it only uses candles. This is really good because candles are cheap and easy to carry. They don't go off, and it's easy to see how much of them is left, unlike batteries. And of course they are made from fossil fuels. That's not necessarily a good thing. Also, for the weight, size and cost of the lantern, you should be able to get a high-powered battery LED, several rechargeable batteries and a charger for them. You probably have a battery charger anyway. LED technology is still fairly young, and there are still plenty of models with excessively long battery life and inadequate brightness. The good news is that if you leave them on they'll still be shining a couple of days later, but that bad news is that you may not notice. This lantern goes out when the candle burns out.
It provides a wonderful lesson in energy efficiency. Thermocouples have an efficiency of something under 10%. Let's say 5% for easy calculation, so they're turning one twentieth of the heat they use into electricity. Then LEDs, while really efficient compared to other lighting sources, only turn about 10% of the electrical power that reaches them into light. So the combination of the thermocouple and LEDs is only only getting one two-hundredth of the power into light. And this electric light is twenty times brighter than the candle was, so the candle is turning less than a four-thousandth of the energy in the wax into light. A few times less, in fact, since a lot of the heat from the candle is not even going to get to the thermocouple.

So how much better is this than if the fossil fuels, instead of being sent to the candle factory, were sent to a power station, then to your house, and into a rechargeable battery?

Nanogeneration: SolePower charges smartphones by harnessing walking power

While strolling between drinking establishments in Kyoto the other day, Peter suggested his idea for an electricity generator that would convert the energy each time the foot stepped down to the ground into power to charge your phone. A couple of days later he sent a link to a news story of some people doing exactly that.

SolePower charges smartphones by harnessing walking power

They're calling this nanogeneration. "Microgeneration" is used for solar panels on houses. "Micro" literally means a millionth; the typical rating of a nuclear power station is in the order of 5 giga watts--around a million times the 5 kilo watts of solar panels people put on their roofs. Nanogeneration comes a thousand times smaller, generating a few watts. This makes it sound rather insignificant in defusing the timebomb of rampant energy overuse, but we have millions of houses and billions of people so micro- and nanogeneration cannot be ignored in our charting of energy maps for the future.

I had a look at the startup site for SolePower, and by pledging a hundred bucks they'll send you a sole. Once they start manufacturing, I would hope the costs would have been much less than that, but according to the article they are not. A couple of things worry me about the design. It looks like there's only one sole, so your feet are going to be somewhat unbalanced. And most people have more than one pair of shoes. Also, it says it's waterproof, so I wonder how well it will breathe. I also wonder just how far you have to walk to charge a phone, and how regular your walking must be to avoid shortening the battery life. I know batteries can be quite fussy about the way they are charged.

There's definitely a market for something like this among outdoor types and eco gizmo junkies--both relatively wealthy groups! Someone's going to make some money, but I'm not sure how much it will solve the world's energy problems. Looking at nanogeneration in general, the amount of energy and equivalent resources used in manufacturing the generators is likely to far exceed the energy they generate over their lifetime. You would probably be better carrying rechargeable batteries with you.

A more positive way of looking at nanogeneration is in terms of reducing battery anxiety, the curse of this age of portable electronic devices.

More positive still may be raising awareness so that we realise just how much energy we are using and where it could come from.

So how much did your traditional Japanese futon sofa bed cost then?

It's pretty easy costing the parts for the sofa bed. 

The nuts, bolts and screws cost around 1500 yen. The wood cost 4,000 yen. The wheels cost 400 yen.

The guy made a mistake with the washers, charging me 4 yen for a bag of 25, when in fact the cost is 4 yen each. I could have got away with 9 or even 8 mm bolts rather the 10s, which stick out a fair way. This cost more than I saved on the washers.

The labour costs are a little more tricky. I spent at least half an hour getting the wood, and that was after about five trips to DIY shops wandering around looking at parts and scratching my head! 

Then perhaps around eight hours looking at bits of paper and scribbling on them. 

Internet research: two hours. Conservative estimate. Difficult to tell exactly since I was doing it in and among other, more general internet research.

Total design time: ten hours. 

The sawing, drilling and assembly of the nine main parts of the frame took about three hours. I'd bought them in the morning. I was in the shop about an hour, spending far too much time working out which bits of wood to buy so that I could cut all the pieces out of them. They had a cutting service, but only at right angles, so I was going to be on my own for the 73 degree angles of a lot the parts. 

Then there were the fiddly bits, cutting off the corners, trying to plane curves around the edges, then trying sand paper before realising that a rasp was probably the right tool for the job. Make that seven trips to the hardware shop. I had to go anyway because I only got 8 wing nuts the first time.  Actually, perhaps I should have got a spoke shave, or cut the curved parts with a jig saw.

After assembling the frame downstairs, bolting parts together then screwing the slats on top, I had the great idea of unbolting it into two pieces to make it easier to carry upstairs. It was easy unbolting it, but a real challenge to put it back together since the slats had begun to take control of the frame.

Total direct labour around 8 hours. Call it ten to include visits to the shop. So insulting myself with a near minimal wage of 900 yen per hour, the labour cost would be 9,000 yen. Added to the parts, that makes around 15,000. If I include the design costs, it goes up to at least 25,000 yen. 

For readers of this blog, I'll be happy to charge 15,000 yen though. Send in your orders below!

Actually I had to get some tools too. I guess these should be covered somewhat even though I still have them. Well, I dropped one of the new drill bits I got onto the stone tiles and the end broke, but it still works. 

But who's counting? I had a lot of fun and a great sense of satisfaction!

Also there was an opportunity to teach the kids some woodworking basics, which will have been a good thing as long as they never do any woodwork. The kids were sometimes useful, although at their age they spent more time getting in the way than helping, and when they were helping, they took more time in supervision and fixing what they did than they contributed in useful work. It was helpful having them looking at the drill from two different directions to check it was vertical, and they did some useful sanding, getting some of the edges smooth.

On blogging and a triple-figure draft box

This is a kind of meta-blog. Nothing to do with the topic of the blog, but just about the way I write it.

The important thing with blogging, and probably all publishing, is to create constant output. Writing is easy. Anybody can do it. You don't even need to be able to use a pen any more. Publishing is more difficult, and publishing writing that everybody will read is the most difficult.

The internet has made publishing much easier. All you need is a computer with an internet connection, then you can get your words of wisdom out to the masses. Of course they may not read it. You cast your bread upon the water, and it floats for a while, then gets soggy and sinks without trace.

In fact most people will definitely not read it. Even if you're very famous and have the most popular blog in the webiverse, it's still only going to be read by the tiniest fraction of a very small percentage of users. 

Anything that can make it easier to get the writing out of your computer and onto the internet is a great help. The thing that really makes it easier, of course, is having done it. Once you have got stuff out, it's easier to get more stuff out; once you've decided that it's good enough, and you don't really need to check it for the twenty-ninth time to find more mistakes and better ways to rewrite sentences that have ceased to have any meaning. Because of course however many times you look at it, there will always be a way of changing it to make it better. There will always be parts that you can rephrase, words that you can cut to make it more fluid and easier to understand, extra bits of information or commentary that you can add. If Shakespeare was alive today he'd probably still be rewriting his plays. At least after scratching the lid off his coffin.

Mechanically speaking, the biggest improvement in workflow was using Gmail. Now I start writing blog posts as emails. They sit in my drafts box where I revisit them a few times. I send them directly to Blogger, which holds them as drafts. Then I can go into blogger and check for typos and add any photos and formatting before adding labels, scheduling the publishing date, and hitting the publish button. Perhaps there is a way to add photos while it is still an email, and add the meta data such as labels, but I don't know what it is.

This is part of the reason why the number of emails in my drafts box has been heading towards 200. It went over 100 about a year ago. It used to be around 60. I can remember when I tried to keep it below 30. Most of these emails are half-finished or half-started blogs about the house. One of them just says: "Eco cute: Changed back to middle boiler temperature - January 22nd" in the title, with nothing in the message. Obviously a useful bit of information. At least I thought so back in January, 2012. 

I just went through the draft box and in a couple of minutes deleted 15 that are either too late to send or have been waiting so long that they obviously don't need sending. The delete button is a wonderful thing. 

Cool jets of air on a hot summer's day

It's very tempting to believe, when you stand next to an open window and feel the breeze on a hot summers day, that it's cooling you down. It may be cool as you stand there, but if the temperature outside is higher than inside, and you happen to be in a well-insulated, airtight house, and it's likely to be over 30 degrees every day for the next month with a chance of a few nights staying above 25 degrees, then you really don't want the windows open when it gets hotter. 

The heat exchanger in the ventilation system will do a much better job than the windows at keeping it cool. If it's 30 degrees outside and 25 degrees inside, the air coming in through the windows will be at 30 degrees, but the air coming in through the ventilation system will be a little over 25. It may be more humid, but that's another issue. Humidity could make it feel one or two degrees warmer, but not five.

Of course, the air coming in through the window may be cooling you down by helping evaporation and blowing heat away from your body, but even if it is, the heat is going into the house and will be there for you later.

Then there's the effect of air at velocity expanding into the room.

I remember this from the day of the first airtightness test, 9th August, 2011. It was a hot one, 31.6 degrees outside, according to the test report. It was 31.3 inside. The house was still being built then, so the windows were usually closed at night and left open during the day. We now do the opposite.

For the airtighness test, the windows had all been closed. They had fixed a fan to one of the windows, then blew a lot of air out until the pressure dropped about 50 pascals below the pressure outside. Then the fan switched off and the machine started to measure the pressure go up as the air leaked in again, and that was our chance to go around the house searching for places where air was getting in.

You could feel little jets of cold air coming in at the corners of some of the windows. I remember wondering at the time why the air should feel cold when it was hot outside, inside, and presumably in the wall between. Now I realise it was the air expanding. The same amount of heat. Bigger volume. Lower temperature.

So the same thing is probably happening, to a lesser extent, when the window is open and air is rushing in to a large room. But when the air stops moving and settles at the ambient pressure, which is very close to the atmospheric pressure, no coolth has been gained. Or rather no heat has been lost, since "coolth" is neither a word in English nor in science.

It would be nice if this effect could be used in some low tech way, with fresh air outside somehow increased in pressure so that it would come inside at a desirable temperature and pressure, and genuinely cool the house. Something more sophisticated than an open window but less than an air conditioner, which in fact uses the same principle but with a coolant rather than air.

How fans do and do not cool

It's now air conditioner season. We have one at home but it is just in one room and so far we have hardly used it. We have an electric fan, which seems to work. 

There are three ways of looking at how fans work. There's the science-free way, the way with a little science, and the heavy science way. 

The unscientific way of looking at it is that the fan is sending out cold air. The air feels cool, and the fan makes you feel colder so this view has some logic. 

If a little science is applied, it's tempting to think that the fan is not sending out cool air, and that it is simply cooling by helping the moisture on our bodies to evaporate by blowing the air away from next to our skin. This view will, quite correctly, note that fans are not going to make the room cooler, because the fan motor is generating friction and electrical resistance is heating up the coils and there is generally an increase in entropy all round. 

While an air conditioner will cool down the room by pumping heat outside, a fan will, if anything, make the room warmer by bringing in electricity, looking at a closed thermodynamic system. 

But this is ignoring Bernoulli. One way of looking at the Bernoulli effect, recently mentioned on an episode of the BBC's In Our Time talking about the completely irrelevant subject of cosmic rays, is by blowing on your hand. If you open your mouth and breathe, it feels warm. If you purse your lips, it feels cool. The reason it feels cool when you purse your lips is because the air is at a lower temperature. The reason it is at a lower temperature is because it is at a lower pressure. Since temperature relates to the amount of heat, and lower pressure means that the gas is spread out over a larger volume, so the temperature drops. The reason for the pressure drop is that the air is moving faster.

Another way of looking at it is what happens on narrow streets at Matsumoto Bon Bon. This is an annual festival where a few thousand people dance around the streets for three or four hours. Some of the streets are wide dual carriageways and some narrow one-way streets. What usually happens, as the evening goes on and more of the beer carted around behind each group gets drunk, is that the procession ceases to have a uniform density of people, and instead has some very crowded areas where nobody is moving, and some completely empty sections. The narrow streets always become empty, so the dancers have to run along these to catch up with the next group, often having been dancing on the spot before. What is happening is that the narrow street is making people go faster, and because they are going faster there is more space between each person and the density has gone down. Exactly the same thing happens between the atoms in a gas. This, incidentally, is what keeps planes in the air. 

It also means that the air coming out of a fan is actually colder, since it is moving faster and has lower pressure. But unless you keep the whole house at a low pressure, the overall temperature is not going to stay down. The fan will only cool you down if you are standing in front of it. Otherwise, it should be switched off. 

(fan graphic taken from: http://blingee.com/ without permission)