[OpenTRV-dev] Thermoelectric power for TRVs?

[Damon Hart-Davis]

Thanks for doing the calcs.

It might be of interest as a battery-life extender, I agree, though at what cost and fiddle factor for end users?!

Anyhow, maybe if you want to develop the idea a little further we could put something on the wiki at least to more fully explore the idea, since you're not the first person to bring it up.

Potentially a small PV panel might also help in some circumstances to 'harvest' a little ambient energy: I put together a nightlight that only needs charging about once every 6 months and I think that the little panel I have in there (a few cm^2) helps a *little* but is not enough.  And for a TRV down the back of a sofa, it would be worse.

So I think that we should assume that neither Seebeck nor PV will be in the next round of OpenTRV designs, but it would be fun as a thought experiment to see how much help they might be in a realistic deployment.  (And of course we could monitor the energy-harvesters' outputs as part of the overall environmental sensing, eg even for occupancy!)

Rgds

Damon



On 28 Mar 2013, at 11:41, Thomas Hood wrote:

> On Thu, Mar 28, 2013 at 11:27 AM, Damon Hart-Davis <EMAIL ADDRESS HIDDEN> wrote:
>> My feeling is, that if there is a big enough gradient to extract
>> energy from then we're doing the heating wrong.
> 
> You can generate electricity from the difference between body
> temperature and ambient temperature. Not much, but still. :)
> 
> /me gets out an envelope and does some calcs.  My furnace supplies
> water at 75°C (factory default setting). Micropelt's datasheet for the
> TE-CORE/RF includes a table of "output power and battery equivalent".
> At a continuous 𝜟T of 35°C the board produces annually as much energy
> as 6 AA batteries.
> 
> Now, given that a radiator valve isn't always fully open (especially
> during the summer) this is clearly not enough power. And since a
> particular radiator could be cold all the time, this power source
> can't possibly suffice on its own. But it's significant enough to be
> interesting. The power output scales with the area of the thermal
> generator element and the element in the TE-CORE/RF is only 1,5cm².
> 
> Anyway, the idea is just that this is a technology of possible
> significance for the project.
> -- 
> Thomas
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