Thread: Electronics O/T

Hi Rod,

Without a circuit of what's inside the epoxy block it's pretty hard to be sure what's in there.

But, you can make some guesses..

That unit is a switched mode dc dc converter, which means there will be diodes on the secondary side to rectify the high frequency to get dc out... so I doubt that you would get peltier generated voltages feeding back to the panel...

I'd put the schottky diodes in series with the solar panel anyway, if you've already got them.

As far as a test goes, you could put a amp meter in series with the panel when it's dark and see if any current is feeding back.

Regards
Ray

Started the cooler today. The peltiers are sandwiched between two water cooling jackets. The second photo shows the top clamps before they were cut to size.

Hot on top and outlets facing the back, cold on the bottom and outlets to the front. Polystyrene will cover the cold side of the plate.

The pocketing keeps everything lined up as there are three peltiers per section and a bit awkward to line up without the pockets.

looking good , dont forget the heat transfer paste , can you swap the heat around so you can easily get a temp probe on the surface of the cold , to stop it freezing over ?, just my thoughts

Hi Ken,
This is just a trial fit and I am connecting the plumbing first so I don't move things while I work the hoses on. I'll use heat paste as you suggest.

I was thinking about drilling a hole in the bottom plate and siliconing a probe in each bay. I have cheap thermometers $5.00 each that seem to work well and if the air con works I can go with a temp probe and some electronics to control it.
I will be running each block independant as I think cycling the coolant through the four blocks in series will definately ice it up.

Lots to go and fingers crossed it works.

Oh yeah my last post with all the machining of the plates brought it back to a CNC post.

Hi Rod,

Looking good, the heatsinks are coming up nicely.

I'm wondering what you have in mind for the control system?

Regards
Ray

Thanks Ray,
It has been a fun project.

At this stage I haven't anything planned for a control system. I would like to see it work before I take the next step.

I am running the solar panels through a 12 volt regulator and apart from switches and fuses that's all I will be fitting up to start it off. The switches will enable reverse polarity so I can test the heating side which might be my start up test due to the slow rate of finishing this.

I finished plumbing the heatsinks and assembled the peltiers on the plate. Hot is to the back side of the plumbing and cold to the front. Tested the plumbing for quite a while and no leaks.

Might get some testing done with the solar panels next to see how good it chills the water..

Well its a failure.
The best I can get is 22 degrees on a 34 degree day. As you can see from the photos it is jury rigged and not insulated however I am just recycling the coolant through 20 litre buckets and not drawing off cold to cool the house. I had expected a lot better result than I have got so will scrap the project and go to my fallback position and hook the solars panels up to an inverter and grid connect. I will get credits for those days you don't need an air conditioner running and the house air conditioning will be offset a little by the solar input.

At least I have scratched the itch and learnt a little along the way.

12 , 130 watt peltiers should get that bucket ice cold in 1/2 an hour ?

??/ too much wattage for the solar panels and you have a voltage drop ?

12x 130 watts is 1560watts , try using 1/2 of them

Hi Ken,
I think I am right for power as the panels are 80 watt and 100 watt and the peltiers are 65 watt and 95 watt - matched to the panels.
I just went out there and the temperature is saying 20 degrees now and 50 on the hot side but it does feel icy cold to touch. The thermometers may be reading high as I have the probes in plastic bags floating on the water.

whats the part number of the pelter's

!2706 and 12705

Just did some bench testing with the peltier. While they can get down to very low temperatures once something draws it away the temperature rises quickly. In the test I did the heatsink was at 10 degrees but put a 60mm fan across the heatsink and it rises to 22 degrees very quick and doesn't make it up at all.

This concurs with my larger coolant test today and it looks like they have little capacity for recovery. Probably ideally suited to an esky or closed insulated container but not much good for distributing over an open area.

Now if you want heat these things are very efficient and produce much more heat than cold.

That's a shame rod as I thought you were on a winner. I think your analysis is correct in that these peltiers are just not efficient enough for the input you put into them. If the differential was higher, by increasing the power into them you could probably have overcome the rise in temp due to the fan.

As I mentioned to you while I visited, I want to store some of my electricity in batteries (fork lift ones) and try to make a 3kw system from a 48v battery bank. The inverter is my problem $$$$. I just think the government or power companies will screw those people over in years to come who have connected back to the grid.