Science Interviews


Tue, 23rd Feb 2016

Harvesting waste energy

Peter Cowley

Listen Now    Download as mp3 from the show Could The Internet Die?

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 itís been done for many years.  I mean winding back a watch, which goes back 6-700 years, youíre actually winding it up from energy from your hand, which is to do with food producing energy, which is then stored in a spring.  Iíve actually got two watches on for some strange reason today.  Iíve got one that winds automatically, which is a Swiss one, which is very nice oneÖ

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

Peter - There is something that rotates and the springs built up so, basically, it runs overnight.  So when Iíve 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 - itís 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 - Thereís something called smart pavement slabs thatís 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 itís generating energy?

Peter - Correct.  It only generates a few milliwatt hours, so it wonít generate very much unless youíve 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 canít always come from solar power, it canít come from because you have to change those.  So actually, collecting energy from vibrations, collecting energy from movement, collecting energy from temperature variations.  Thereís work also thatís been mentioned in BBC site quite recently was to with pacemakers have batteries, batteries need changing unless you charge them externally, but thereís an awful lot going on in the body with temperature changes and movement so why canít you actually just take the energy from that.  And somebody tried it on pigís heart actually - just the movement of the heart will generate five times more than you need on a pacemaker

Kit - StuartÖ

Stuart - Yes thatís really interesting.  Thereís 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 thatís 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 canít you just by having two things at different temperatures?

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


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