Re-think

The winter is approaching, its getting cold, and the particle panels are on my mind again.  Yesterday's glue's discovery got me thinking.  I've certainly encountered a number of problems over the last year or so.  There are so many variables at play it can be a little discouraging.  I've been in this position before with some of my other projects, but eventually time and experience wins out and a combination is found that works.  My hope is that this blog post will put forward a design that solves the many constraints I am faced with.  I have everything I need or it is available from a local distributor. 

Particles

I have a bunch of the 60um silicon carbonate particles as well as 40um wire mesh.   I have been worried that the silicon carbonate particles will wear the panel out from the inside, as they are abrasive.  Some readers have been very helpful in pointing out alternate particles, from glass to carbon to plastic.  The particle panels concept should work for particles that are lighter then water so long as the water flow is reversed.  This has some advantages and some disadvantages.  Right now it would be a pain, as the plumbing gets much more complicated if I want to operate as a drain-back system.  The particles would presumably be softer (perhaps plastic), making them not as abrasive.  I looked into polypropylene micro-spheres and the cost was pretty high, much more then I would like.  Floating particles are still on the table, but i'm going to continue with heavier-then-water particles.  In fact, i'm going to continue with what I started with: silicon carbonate.

Plastic

My first prototype was with polycarbonate (PC) because I could get it from a local distributor.  Not long after I discovered that PC degrades in the presence of hot water (hydrolysis).  This was obviously horrible news for a solar heater.  I then though I found the solution with polypropylene, but I could not get clear panels.  They were "milky", which I really do not like.  Polypropylene is also hard to glue and welding the manifold on the end is very difficult.  I then looked at acrylic, which seems good. However, getting the panels is a pain as I do not have a local distributor.  Acrylic is also very brittle. 

The only problem with PC is the water degradation.  This is a big problem, but perhaps I have a solution.  In previous posts I discussed the idea of circulating oil through the panel.  The idea is that a small amount of oil is put in the tank.  This oil is circulated into the panels and should stick to the inside walls.  Since oil is hydrophobic it should stick to the plastic panels.  My thinking here was to repair any damage that occurred from abrasive particle wear, but now I'm thinking it could also solve the hydrolysis problem.  If there is a protective layer of oil between the water and the plastic...should that not help tremendously in the panels ability to fight off hydrolysis?  I think it will.

My concern now is that the oil layer will trap particles, causing them to stick to the inside wall.  This may or may not happen.  If it does, its a big problem.  If it does not, then I may have my solution.  There is also a problem of what oil I use.  And just because i'm circulating an oil with the water does not mean it will stick to the inside of the panel. I may need to "pre-coat" the inside with oil to insure that a layer of oil exists to catch the oil droplets as they pass by. 

I think this strategy may pan out.  It allows me to use materials which are available commonly available and inexpensive, which is very important if this is to work.  If I could get all this working, then its possible kits could be sold that would allow home owners to build their own panels, saving the cost of the labor and allowing them to heat their homes for years for a few hundred bucks.  Thats what keeps me going.  One day it will all come together!