[OpenTRV-dev] Thermoelectric power for TRVs?

[Philip Canavan]

None of the TRVs I've looked at use a spring, relying instead on the gearbox and motor to act as a passive break on the pin actuator. As below, I'm not sure there's enough standardisation or energy saving to justify the increased design and manufacturing costs. I suspect you'd get better returns from improved gearing or tweaks to the software\wireless protocol (but I won't try to prove that!).

Thomas Hood <EMAIL ADDRESS HIDDEN> wrote:

On Thu, Mar 28, 2013 at 2:27 PM, Stuart Poulton <EMAIL ADDRESS HIDDEN> wrote:
> On 28 Mar 2013, at 12:19, Thomas Hood wrote:
>> On Thu, Mar 28, 2013 at 12:56 PM, Jack Kelly <EMAIL ADDRESS HIDDEN> wrote:
>>> The pin on the base of a TRV is spring loaded, isn't it? I wonder if
>>> there's a way to reclaim some of this energy when we release the pin.
>>
>> The radiator valve insert is spring loaded. If the TRV is well
>> designed then it is also spring loaded so as to balance the insert
>> spring; then the actuator only needs to overcome friction plus I
>> suppose some dynamic hydraulic pressure. Is this not how the motorized
>> TRVs are actually constructed?
>
> I don't believe there is a spring, I'll try to deconstruct my TRV
> over the weekend. It simply relies on the gearing to prevent the
> pin from returning.

Hmm, well I suppose you can only include a spring if you know what the
minimum possible tension on an insert spring is, otherwise the TRV
spring will hold the valve closed. And perhaps you don't know that
because there are so many makes and models of inserts.

In any case, a spring efficiently implements the idea of storing
energy delivered by the insert pin and returning it later when needed.
If the spring pushes with 10N and the travel is 3mm then the energy
stored is 30mJ. Maybe that isn't enough to warrant building in a
spring. An AA battery stores about 10⁴ J.
-- 
Thomas
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