Passive Solar Water Heater Oast

I'm looking into building a passive solar water heater to help keep the shop mildly warmer in the winter so I only have to wear one layer and not two when I'm out brewing or working on random projects. I had the thought the other day "How difficult would it be to build a passive solar water heater system into an oast?"

I was wondering if anybody else out there had the same thought or even tried it and how well it worked if they did. I'm thinking it could be easy as building and extra loop in the water heater system and run the coils in between the fan and the hops.

It might be difficult to control temperature though as the water heats up. Any thoughts?

Just so people know what a passive solar water heater is - You make a few coils of piping in a box with a clear top. Paint everything on the inside black to absorb the sun's rays and point it towards the sun. You can run the coils to a tank to store the heated water for later use. There are other ways to do this of course instead of coils you can put a tank there to heat up. Either way the idea is you use the sun to heat up water and run it through a piping system to give off heat or to send hot water to a sink or bathroom.

http://en.wikipedia.org/wiki/Solar_water_heating

Long story short, you can do it without a problem but the question is why would you want to?

The big boys use heat to raise air temp thus lowering the relative humidity of the air so it can absorb more moisture faster. This is needed if you are trying to dry several acres of hops overnight.

You don't need to do this. You have all the time in the world...sort of. Take your time and keep the temperatures low. Above 140F, your alpha acids start to break down. Above 100F, most of your oils (aromas) are evaporating. Heck, some of the oils start at 79F, so keep the temperature low keeps more of those oils in place and will give you a better hop for brewing. The problem is that it will take MUCH longer to dry...days, probably.

Yeah I just thought it would be an interesting concept. I didn't really plan on doing more than just drawing it up. I was just wondering if someone else out there had poked around with it.

GVH Dan, is one of the pro's/guru's around here. I'd consider what he says. I can't remember where I was, but I'm pretty sure I've seen someone advertise that their hops are dried with low or no heat. So you see, for the small guy, it's actually a selling point!