"Hybrid" solar panel

[Noitoen]

Hi,

I'm building a campervan and came up with this crazy idea. I'm going to install a 370 W panel on the roof of the van with a MPPT controller charging 3 95 A/hr 12v batteries. The crazy idea is that I want to glue a sheet of 8mm thick corrugated PP to the back of the panel and seal up the top and bottom of the sheet's hollow channels with a "U" profile to run water through the corrugated sheet. A small pump circulates the water of a insulated 40 liter tank under the van. This will be controlled by some temperature sensors to insure that, when the tank's temperature is higher than the panel's, the pump will stop. I'm also thinking about a few turns of copper pipe around the exhaust but that's another story.

What do you guys think?
 

[Scruff]

I think it sounds better in concept than it will work.
Bare in mind it's a high-vibration application and the PV is absorbing or reflecting most of the energy in the light.

I'd throw a ~600W fixed array and a TriStar PWM set to diversion into a colorifier. T the eninge coolant through another coil and you have the option of hydronic through that too (second isolated coil) if you want.

The exhaust can be done with an EGR cooler but it's complete overkill to use that and the engine coolant at the same time and the engine coolant is much easier.

Good luck with it.

PS You forgot to mention a recirculating shower and underfloor heating. 

[Noitoen]

South of Portugal, even in winter the temperature is ok. The heating of the water will mostly be done during the long hours parked in the sun at the beach  . I nice warm shower feels good even in the summer.

[Bruce S]

This type of PV cooling has been written about here before.
Not much else other than thoughts.
Depending on the PVs they are not going to be very good for cooling off the back even though radiant heat could build up while being parked.

Since you'll be parked, it would be easier to simply build a heat grabber style system.

Look (internet search) into the pipe-within-pipe most done for older Mercedes diesel cars (84 and older).
I built this for my 84 300TD so I could use veggie oil, it worked like a charm and near ever had a leak.
These are probably similar to what Scruff is talking about.

Cheers
Bruce S

[DamonHD]

The technology in general is called PV/T (PV/thermal) which may give you a few more things to search for!

Here for example is a company making the stuff, but it is not alone, and the idea is well tested:

https://www.nakedenergy.co.uk/

Basically you have a choice of getting hot water out and less good PV (electrical) performance, or tepid water and better electrical output.

You may already know all this!

Rgds

Damon

[Scruff]

This is what I'm talking about not doing in preference of using the already hydronic & plumbed engine coolant system. (Except with the engine exhaust, not a diesel heater)

The engine is ~60% waste heat unlikely you'll ever need to harness the exhaust and coolant at the same time...I'm still thinking about doing it in a truck having said that. I'll be heating more than a colorifier though.

[Scruff]

I'd go all out photovoltaic and leave the thermodynamic off the roof. Wires are way more forgiving than plumbing.
You can get 12v elements or even dualies for colorifiers.
I can never understand why they come with 230v elements as standard for 12v/24v installations...I suppose because the whole untethered concept of mobile installations is lost on a lottov people.

[electrondady1]

it think it  might be difficult to seal a corrugated polypropylene sheet to what ever you use for end manifolds.  scout around for automotive radiators . air conditioning units.  trans coolers. things of that nature. something wide but narrow so as not to sit too high above the roof of the camper. solar panels only capture 15% of the energy that falls on them  leaving 85% to heat the water.

[Scruff]

I think you're confusing absorption and efficiency there ElectronDady.



If the van moves it'll cool the collector too.

[Noitoen]

Sealing is easy in my opinion. The idea is to plug all the square 8 mm holes with about 20 to 25 mm high temperature silicone then, with a router, cut a shallow 12 mm wide 4 mm deep slot. There is a 15 mm omega shaped white PVC profile that will cover the slot and it is easy to make a threaded connection for the hose. I know it's a crazy idea but I'm sure I will get some usable heat out of the panel.

[Noitoen]

I don' need to modify a air heater if I decide to go this route, there are parking heaters already available that are used in cold countries to preheat the engine water that work on a timer.

[Bruce S]

I'd say go for it!!
Keep us in the information loop. May turn out to be very usable for someone else too.

Cheers (I'm heading over to watch the vid Scruff posted)

Bruce S

[richhagen]

I think that it is interesting to try and capture that part of the thermal radiation that the solar panel can not capture.  I would think that it would only be worthwhile where space was at an absolute premium.  Any cracks in the Tedlar and EVA of a panel would likely be catostrophic due to galvanic corrosion to the panel in such a setup, whereas exposed to air would be much less of an issue.  I would rather build a rack of shelves on the roof where I have a couple or more 'shelves' containing panels that slide out from under the top when my rig was parked, they could do double duty as sun shades or entrance canopy when parked.  In the solar panel array, size matters, and if you can get 4 times the square footage it will help in less than ideal conditions.  I have heard very few people complain of making too much power.  The water heating adds complication and if I were doing it I would try to put it on a portion, say 1/2 or one fourth of the roof on the top shelf with the other part photovoltaic to keep the campers main batteries charged when not in use.  When in use I would have full shelves of solar panels that would slide out to either side to give a lot more power when it is in use and needed.  That way if I had a problem with the solar hot water system it would not impact my electricity generation.  Just my 2 cents, Rich

[Scruff]

I have heard very few people complain of making too much power.

  No such thing!!! 
I apply the same philosophy when stockpiling alcohol.

[Noitoen]

This is a mobile installation and the space on top of the van is limited. Skylights scattered around the roof awning at the side tv and satellite dish are all strategically place leaving a 2000x1000mm space for a 400W mono panel. There is no metal in the water heating setup so no galvanic corrosion dangers. The PP panel will be stuck to the back with a thin coat of glue and 4 wood crossmembers distributed along the back of the panel to reduce vibrations and protecting the the glass on the road. I've decided that the thickness of the corrugated PP panel will be 2,5mm so, the total amount of water in the "heat exchanger" will be around 2.5 liters. The circulation pump is a 12v brushless type of motor capable of 8 liters per minute so, lets see how it goes. If it does't work, All IO have to do is stop the circulation and get another heat source. Maybe a couple of turns of flattened copper pipe wound around a small length of exhaust will add a little heat also, so, can't know for sure unless you try.
These options are so cheap to implement, and if nothing comes from it, at least you learn something.

[Bruce S]

I like your outlook on the learning !!
I've seen a few of the tiny home/ Van life builds .
Once you have the wood up on the roof you may find you have more room if it's needed.

I look forward to reading the progress.

Cheers
Bruce S