Aluminum Solar Absorbers - Product Details
Details of the product;
* Grade 1100 aluminum; best grade aluminum for heat transfer to (and from) water
* Coil width starts at 8", with a finished width after press work of 6 3/4" ( +/- 1/4")
* Custom lengths from 24" to 34"
* Can be pressed to fit 1/2" tube (copper or PEX), 5/8" PEX, or 3/4" tube (copper or PEX)
* Standard "fit" on absorber yields a 70% tube contact
* Absorbers can be used as heat exchangers as well, for in floor heating
* Orders can be of any quantity, with varied lengths if desired
Photo above: End view of a stack of finished aluminum absorbers
High efficiency Absorber;
Our clamps holding the absorber tightly to the copper.
90% wrap on the left, 70% (standard) wrap on the right
* The absorber can be field modified for a 90% contact area, but requires further steps than we can provide for the price we offer the absorber. This process involves pressing the aluminum in a die "one size over" the one designed for your specific tubing size (Example, using a die for 5/8" PEX for absorber going on 1/2" copper). The pre-pressed absorber is then placed over the actual tubing (or a scrap piece of it), clamped tightly with the "Vise Grip" Clamps, and a rubber mallet is used to "set" the absorber tightly to the tubing by tapping briskly once on each extended "c" area of the clamp. On a 32" absorber, this would require "setting" the absorber with two clamps, twice (8" clamp area, times two clamps, covers 16" of absorber each time). This process is a fair amount of extra work, but the "contact area" of the absorber is increased by 28%.
* The need for an aluminum strip under the absorber is pretty much eliminated with this process, as the tubing will now be raised about 1/8" off your backing material.
* This system works nicely on collectors utilizing 3/4" copper manifolds (upper and lower tubes the risers connect to) with 1/2" copper risers, since the risers will already be raised a bit off the backing material.
* Removing the absorber from the tubing after fitting it at 90% should be done be sliding it off "end-wise", as it fits really tight. Obviously it will be "snapped" over the risers during final assembly. For this reason, when installing "high efficiency absorbers", the clamps are a must to ensure tight fit/contact on final installation. Many builders are doing the final "set" or "forming" to 90% after the absorber is installed as shipped (1/8" oversize at 70% wrap), cutting this down to one step.
F A Q
What do I need to know to order absorber?
You should have figured out your collector design (manifold and riser, serpentine, copper or PEX and tubing size). You should also decide the length of the tubing runs that will be covered with aluminum absorber. Example; If you are doing a standard 4' x 8' panel, standing it up the long way, and using 1/2" copper tubing in a manifold and riser design, you will lose at least 6" of the 8' length of distance for your risers. The loss is from the manifolds on the top and bottom, the framing material (usually 2" x 6"s), and space for the manifolds between the framing material and the manifold. For a panel this size, the absorber length will typically be 90" or less, and we would need to stamp those in three pieces per riser (three 30" absorbers per riser).
How long from when I order it will it be shipped?
We typically process the orders within 24 hours. Any orders filled by 5 PM will ship that evening. The majority of our orders are shipped Fed-Ex Ground or Fed-Ex Home Delivery. Fed-Ex rates are slightly less than UPS, and our damage complaints have disappeared. We've quoted USPS for several orders, but they have not been within the price range we see with Fed-Ex or UPS.
How much will shipping run?
Shipping costs are directly related to several factors. The quantity of product, the box size, and the location of the delivery point from us. Generally small orders (under 75') run from $15 to $20. Orders of 100' to 120' are usually around $25, and orders up near 200' to 250' are around $30 to $35. Obviously, these are rough estimates and orders to California and Maine run a bit more. Box size and delivery location clearly effect the rate.
Do you ship to Canada?
We've shipped several orders to Canada (thanks go to our Canadian customers). There is more shipping costs going across international borders, like customs and brokerage fees. Some, if not all, customers have been hit with a "duty fee", either at the time of delivery, or after the fact. I've been told USPS shipping avoids that, but on orders of any size, the UPS fee has still proven to be the cheapest route.
I've never done this before, any suggestions on collector design?
I get a lot of prospective builders that ask about the attachment method of the absorber, and this ties back to the base collector materials. Many builders have stapled the absorber directly to a backing board. Although most have seen good results, here are my observations and suggestions. To staple, you must be attaching the absorber directly to a backing board. This means the backing board will be a heat sink for the collector, heating up to the temp of the absorber (not good). The other issue, the aluminum will expand and contract from the heat cycles. The staples can (and have by some reports) loosen up, and the direct contact between the absorber and the tubing will be compromised. Finally, if the Styrofoam is attached at the back of the collector, any collector not mounted directly to a wall will have the insulation exposed. Many builders are then adding another sheet of wood to protect this. I say, why not start with a sheet of 3/4" plywood (or OSB) as the back of your panel. Inset the plywood into your frame to protect the vulnerable edge of the laminated sheet from the weather. Once the frame and back are assembled, install a sheet of 1" Styrofoam (or preferably Polyiso for higher temp) against the backing board. Now install your soldered copper tubing grid (or start winding in your serpentine PEX). The absorber can be clamped (we do recommend the clamping action for best contact before securing the absorber over the tubing) and screwed through the insulation and into your backing board. By using the above recommended materials, a 1 5/8" drywall screw is now the perfect length for attaching your absorber, as it's going into a 1 3/4" depth box (will not protrude the back of the panel). Advantages to this design; no loss of heat from the absorber to the material it is touching (insulation). The screws are much stronger at keeping the absorber tight to the tubing. The screw, running through 1" of insulation, has room to "move" with the expansion of the aluminum, and will be resilient enough to keep the aluminum absorber tight to the tubing after many cycles of expansion and contraction.
What should I use for glazing?
A lot of panels are designed around this factor alone. Polycarbonate is pretty reasonable, and available in many different styles. A commonly available (and cheap) option is corrugated polycarbonate, sold in many large building supply stores as a roof material for decks and open air spaces. Flat polycarbonate is a little harder to fine, but a typical glass store should be able to get it for you. If you live in a major metropolitan area, you may have access to a large greenhouse supply store, where twin wall and triple wall are available. We have found shipping on this product to be very cost prohibitive. Basically, anyone selling it needs to be very careful packaging it to avoid damage, and the size of the panels usually mandate they will need to ship by truck.
Should I do Drain Back or Closed Loop?
Each has their advantages, you really need to look at your design goals, your limitations for space, grade (ability to pitch all plumbing downhill), and your existing plumbing you will integrate this system with.
Any last suggestions before I start my own system?
Definitely!!! Read as much as you can. This website is 90% informational and 10% about selling solar absorber. Read through the different projects and get a feel for how these systems are built. Visit Gary's site at www.builditsolar.com and review the many systems built by other DIY'ers. Take the information from here, his site, the solar blogs (Simply Solar, Solar Heat, and Field Lines Water & Heating topics), and find what excites you and works for your application. The evolution of home built hot water solar collectors has come a tremendous distance the last 4 years, in most part from guys like Gary, sharing information and displaying builders systems.
Will you help me with questions or design considerations, even if I don't buy your absorbers?
Absolutely. I am in this much more for the passion of DIY solar than for the sale of a few feet of aluminum. I found the hardest process, and frequently the hurdle, to building your own hot water solar collectors was the stamping out of the absorber. That's why I built the molds and dies for my collector (and several other friends I wanted to see doing solar). I consider my success with solar to not be how much absorber I've sold, but how many new DIY solar collectors may be sitting in the sun tomorrow because builders been convinced they can do it by this website.
What should I do for dissimilar metal corrosion between the absorber and copper tubing?
I usually prime the inside of the aluminum absorber groove. Some builders prime and paint both the tubing and the inside groove of the absorber (see Joes DHW Project). This is to avoid dissimilar metal corrosion, which will happen between copper and aluminum if left to contact in their bare state. Most builders clean the absorbers good with soap and water before installing them, and then a simple "wipe down" with a damp rag is done before priming and painting. For my large array, I used a PPG process, with a PPG cleaner and then wiped with a PPG aluminum prep. Since I had problems with corrosion after the fact (my brazed joints reacted with the aluminum prep), I'm thinking the soap & water method on a glazed panel is probably sufficient, and certainly avoids the problems I had.