Solar/battery powering


  • Hero Member

    Hello,

    Following my desastrous experiment of a battery powered sensor, I am searching for a way to have an outdoor sensor that would last a bit.

    From what I have as option (but there must be more since we have a hardware category !):

    • Li-On 3.7 V batteries
    • LiPo 3.7 V batteries
    • solar pannels

    I have seen some kitts such as the Seedstudio Stalker which includes board, battery, waterproof box and an arduino and xbee radio for €50.

    Another kit has a solar pannel and a 2300mAh battery, but also many cheap solar pannels, some that can fit in the project box on this site.

    I will try some BRC 18650 Battery 5000mAh 3.7v, but I would need advice on how using a solar pannel with batteries...

    Thanks in advance for your ideas,




  • Banned

    *From what I have as option (but there must be more since we have a hardware category !):

    Li-On 3.7 V batteries
    LiPo 3.7 V batteries
    solar pannels
    I have seen some kitts such as the Seedstudio Stalker which includes board, battery, waterproof box and an arduino and xbee radio for €50.

    Another kit has a solar pannel and a 2300mAh battery, but also many cheap solar pannels, some that can fit in the project box on this site.

    I will try some BRC 18650 Battery 5000mAh 3.7v, but I would need advice on how using a solar pannel with batteries...

    Thanks in advance for your ideas,*
    So what did you choose epierre



  • @david-d Andreas Spiess made a nice video for this, I think this is a good place to start:
    Cheap and simple Solar Power for our small Projects (ESP32, ESP8266, Arduino) – 14:11
    — Andreas Spiess


  • Hero Member

    Often the hard part is either 1. the moisture proofing required to prevent corrosion or 2. finding a solar panel/cell that doesn't degrade under outdoor UV. Even a lot of commercial products rapidly fail for one or the other reason. Cheap solar devices from China generally have both problems in the same product. Often epoxy encased cells will quickly brown and eventually become nearly opaque, greatly reducing the light harvest or failing altogether.



  • @NeverDie I have seen all those things you mention as well as temperature related dry joints on panels. You get what you pay for generally and panels suited to winter temps below -10C and summer temps above +30C with rain, wind vibrations and UV degredation are expensive..... I always avoid the epoxy ones and have found better alternatives for 'window' use. I power a roller blind from one and it's been urnning without a hitch for 7 weeks now, but I know in the winter even a 10W oanel will not be enough.... I guess that for low power sensors it is an attrative option, but as you said, make sure it is 'tropicalised'!


  • Hero Member

    @skywatch I think maybe sealing the solar cell up against glass may be the only way to avoid uv degradation. I tried various clear spray coatings for uv protection, but after summer exposure they still all degraded to various degrees, even though some of them continue to work. Genuine glass is just a whole lot thicker, and it's obviously what professional solar panels use. Unfortunately, the cost of doing all these things correctly exceeds the cost of the solar cell itself. However, better to know that going into it than discover it after the fact.



  • @NeverDie The other thing to remember when putting anything over a solar cell or panel is that they do not rely solely on vivible light to function. Many will give power from IR waves on cloudy days and some will increase power with UV light. So best to get the data for the panel (or try different materials under controlled artificial conditions).
    Another consideration is that sealing against glass will increas panel temperature as the heat is trapped. This will increase internal resistance of the cell and reduce power output. My panels are all 10W or less and work best on cold winter days with bright sky and sunshine.... I have not yet tried flexible panels to see if they are more robust against temperature variations, but would like to try one at some point.


  • Hero Member

    @skywatch said in Solar/battery powering:

    Another consideration is that sealing against glass will increas panel temperature as the heat is trapped. This will increase internal resistance of the cell and reduce power output. My panels are all 10W or less and work best on cold winter days with bright sky and sunshine.... I have not yet tried flexible panels to see if they are more robust against temperature variations, but would like to try one at some point.

    That's a really interesting point. I wonder why on commercial products we don't see any kind of heatsinks mounted beneath the cells to help wick away the heat? Maybe it's just cheaper to compensate by putting the heatsink cost into a bigger solar panel without heatsinks? That seems to be the logic behind why we don't see much solar tracking: it's cheaper to simply put the money into bigger solar panels.



  • @NeverDie

    I wonder why on commercial products we don't see any kind of heatsinks mounted beneath the cells to help wick away the heat?

    Heat rises so they would probably not make a lot of difference except in the huge increase in weight on the roof timbers.

    But yes - I always wondered why they didn't water cool the panels and use that hot water for the house hot water system or swimming pool. I suppose that would increase production and installation costs and complexity significantly as well as add more points of failure.



  • @skywatch said in Solar/battery powering:

    But yes - I always wondered why they didn't water cool the panels and use that hot water for the house hot water system or swimming pool. I suppose that would increase production and installation costs and complexity significantly as well as add more points of failure.

    In fact, theres some few companies offering "hybrid panels", see e.g. https://www.todoensolar.com/300w-ecovolt-hybrid-solar-panel or https://dualsun.com/en/product/hybrid-panel-spring/ (don't have experience with neither of them).
    Imo complexity isn't that much higher than with "conventional" solar panels for heating systems (liquid based, as known for much longer than the use of electrical PV systems in private environments). It's just the PV aspect added, which itself isn't highly complex, too. In fact, one needs bigger water (or other liquid) tanks to store the "conventionally harvested" part or the solar energy. If you don't already have this part of the installation up and running, the question is, if this makes sense at all or if just using electrical energy to heat (much less) (heating) water is more cost efficient.
    (But this isn't really MySensors related, as 300+W will in most cases not be necessary to drive one or some more nodes...)



  • @rejoe2 Thanks - i did not know about those. I still think that in Northern areas where frost and snow are common it is more of a risk, but it doesn't matter much as I do not consider going down that path!



  • @skywatch It really might depend, how "northern" the respective area is, but at least here in Germany, the used liquids imo are well tested and don't cause much trouble also in (rare) frost or snow conditions.
    (@all: Sorry for one more OT comment).



  • @rejoe2 Anti-freeze.



  • @zboblamont said in Solar/battery powering:

    @rejoe2 Anti-freeze.

    But then the hot water would not be suitable to shower/cleaning/pool etc and you then have to go to a heat exchange tank, somewhere to put it and insulate it and pipe to it. I am sure is can be done, but the fact that it is not 'standard' hints at it being costlly or impractical or both.

    @rejoe2 Agreed! - But it's not OT as you could mysensors the hell out of such an installation!



  • @skywatch said in Solar/battery powering:

    @zboblamont said in Solar/battery powering:

    @rejoe2 Anti-freeze.

    But then the hot water would not be suitable to shower/cleaning/pool etc and you then have to go to a heat exchange tank, somewhere to put it and insulate it and pipe to it. I am sure is can be done, but the fact that it is not 'standard' hints at it being costlly or impractical or both.

    In fact, imo it's highly recommended to use a seperate circle for the "transport medium" (typically: antifreeze liquid)! Otherwise you will at some point in time get problems with corrosion or deposited dirt particles if media would be continuously renewed. Dependent on the needed amounts of (potable) warm water, it might even be a good idea to have three circles (medium for panel, heating water, potable water). But tanks, heat exchangers and so on (including steering electronics 😁) are (relatively inexpensive) standard components - at least here in Germany. So imo technical complexity isn't a thing to worry about too much. But as already mentionned: I really doubt, if you will have a financial benefit out of such an installation, if you have to built it from scratch nowerdays. Additionally: have a close look, how big the need for hot water really is - in most cases, e.g. 5m² panel size for a family of 4 persons should be enough for hot water supply in middle Europe (+300l tank volume). As soon as heating is involved, you'll need much higher tank volumes - with no benefit in summer, but not sufficient capacity on roof top or tank volume in winter times?

    @rejoe2 Agreed! - But it's not OT as you could mysensors the hell out of such an installation!

    Indeed, buiding one's own MySensors-based controller for such a hybrid heating ecosystem would be right on topic - but not in this thread here...
    Fyi:

    • One of my very first things to get done with MySensors had been around my (gas based) central heating system;
    • we have some tubes installed that would allow medium transport from roof to cellar. But to be honest, atm. I'm not willing to invest in tanks etc.; it's just not cost efficient, even if I would do a lot of the installation work myself....

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