This pool collector is a different slant on pool collector design, and may have some unique benefits for some people.
In a nutshell, the collector consists of large diameter supply and return manifolds that are connected by closely space half inch PVC pipe risers. The manifolds supply water to the risers, which pick up the solar heat and deliver it to the pool.
The half inch PVC risers are attached to the PVC manifolds by drilling and taping a half inch NPT pipe thread in the manifold for each PVC riser pipe. Then male threaded to PVC adapter fittings are used to attach the half inch PVC to the manifolds. This is a nice, simple, reliable and inexpensive way to make the collector. Since the collector is custom made, it can be built to fit the roof space available. The riser runs can be made quite long, allowing one large collector to be used instead of several smaller one.
The standard mat style pool heating collectors may be a better choice if they are readily available where you are and can be fit into the space you have. Matt came up with this design because he was in a country where the mat style collectors were not available at a reasonable price, and this design proved to be a good alternative. The cost may end up being more or less than the mat collectors depending on where you are and how big the collectors are.
The pdf that Matt provides has a great deal of good detail on the design and build for the collector and provides plenty of detailed instruction for people who have not worked with PVC before.