## Tuesday, 10 November 2015

### 60 Minutes On This Bicycle Can Power Your Home For 24 Hours!

Why do people capitalise each letter in a sentence? Well, never mind about that, let's examine the claim.

Here's the claim, "from just one hour of pedaling, a rural household can be supplied with energy for 24 hours." and "access to clean, free energy will enable poverty-stricken communities to not only light their homes but to connect to the internet and get educated".

Well, yes and no. The article makes it sound like you're getting rather a lot, for almost nothing - apart from the cost of building the machine. But let's examine the claim.

A fit human can generate about 50 to 150 watts for an hour, unless you're an exceptional athlete. I doubt if I could keep that up for an hour. But maybe the average poverty-stricken villager is a lot more fit than I am.

If you generate 120 watts in one hour, put it in a battery, and use if over the next 24 hours, then you'll get 5 watts. That's just enough to light one small but efficient light bulb. It's not enough to power the router and computer that you'd need to connect to the internet. There will also be energy losses in the conversion of mechanical energy to electricity, and more losses in the storage and retrieval from the battery. And more losses if you need to convert the voltage from what the battery holds, to what the devices need.

So yes, you can have energy for 24 hours, but it isn't enough energy to be useful.

And secondly, it isn't free. Your motor (human) needs to be supplied with fuel (food). In a poverty-stricken community, that's not a zero cost.

So far, every article I've read has bought into this machine; nobody seems to have done the very simple calculation that shows it isn't as wonderful as it seems.

If something seems to be too good to be true, it usually is. Do the sums; always do the sums.