Harvesting waste energy

All processes give off waste energy and more and more technology is being developed that harnesses that energy in a useful way.
23 February 2016

Interview with 

Peter Cowley


Secondary school science lessons taught us that pretty much all processes give offClock Face waste energy, in our energy hungry world of washing machines, cars and mobile phones this seems like an untapped resource, but maybe not. Energy harvesting uses technology to gather waste energy and put it into something useful, Peter Cowley explains all to Kat Arney...

Peter - It is huge untapped resources as you can imagine and it's been done for many years.  I mean winding back a watch, which goes back 6-700 years, you're actually winding it up from energy from your hand, which is to do with food producing energy, which is then stored in a spring.  I've actually got two watches on for some strange reason today.  I've got one that winds automatically, which is a Swiss one, which is very nice one...

Kat - So when you wiggle your wrist it winds up.  So is there a weight in there or something that's wiggling?

Peter - There is something that rotates and the springs built up so, basically, it runs overnight.  So when I've taken it off it will work for about 24 hours. On my other wrist I have a smartwatch.

Kat - Do you have to plug in your smartwatch overnight then and charge it?

Peter - You do, unfortunately - it's terrible.

Kay - Tell us some examples of how this spare energy: How can it be generated and how can we trap it and harvest it?

Peter - There's something called smart pavement slabs that's been around for some time, which doesn't generate much power, but does actually show the importance of saving energy.

Kat - So this when people step on the pavement it's generating energy?

Peter - Correct.  It only generates a few milliwatt hours, so it won't generate very much unless you've got huge crowds.  There is a lot of work going on, as you know, internet things.  Lots of devices out there.  These sensors need some sort of power; the powers got to come from somewhere, it can't always come from solar power, it can't come from because you have to change those.  So actually, collecting energy from vibrations, collecting energy from movement, collecting energy from temperature variations.  There's work also that's been mentioned in BBC site quite recently was to with pacemakers have batteries, batteries need changing unless you charge them externally, but there's an awful lot going on in the body with temperature changes and movement so why can't you actually just take the energy from that.  And somebody tried it on pig's heart actually - just the movement of the heart will generate five times more than you need on a pacemaker

Kit - Stuart...

Stuart - Yes that's really interesting.  There's a whole field of research called thermoelectrics, which is the idea of can you use materials to directly generate a voltage, to directly generate the power.  And that's actually something we do at the Physics Department at the University of Cambridge is look into those different materials and try and understand, can we convert that into voltage directly from the heat of around they system.

Kat - Because you can generate voltage can't you just by having two things at different temperatures?

Stuart - Yes, that's the thermoelectric effect.  It's just having two things at different temperatures and they will naturally form a voltage in certain materials.


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