rethinking solar heating/dwh/hot tubs

jp_2

I have been looking at a system for DHW and a hot tub, realizing in upper, upper Mi, 47 degrees lat, solar space heating is out of reach.

I thought of a simple system that uses the entire east roof as a collector, basically a soaker hose at the ridge and a gutter, a fair weather solar collector but one that's 380 sq ft, at that size who cares if its a little inefficient.

I come to realize the best idea is to put all this together in one package, hot tub, DHW and space heating. let the system decide "who" needs heat. there's no reason to have only DHW if some space heating can be done, get rid of the storage tank all together.

this will use all solar available. when you run short, you run short and the boiler takes over.

Andrew Hagen_2

Evaporation

Evaporation may cancel much of the gains you get from the sun?

Ross_7

JP, Where are you at?

I live in Marquette

hot_rod

For 32F and above

operation? No freeze protection? look at how a pool collector efficiency drops as ambient temperatures drop, i doubt that square footage could overcome that loss to ambient.

Not much heating load above 70F where this type of collector has some merit. So mainly DHW and hot tub/

hr

Andrew Hagen_2

Cooling?

I have only heard of this type of collector being used for cooling at night in the desert.

Roland_18

Solar Roof

I'd be concerned about washing pollutants off the roof and into a hot tub.

jp_2

silly soaker hose

yes, I agree, in and of itself its a silly idea, as a beginning concept for whole roof collectors, its the starting point.

andrew, therefore a quick fix is to use those green house clear panels. they are double wall clear plastic like corrugated cardboard except the 'tunnels' are square and maybe 3/16 x 3/16.

theres a guy in canada that built an entire roof, about 40 x 10 that was all solar collector. I have the article somewhere.

the main idea here is use all all the solar you can, most people are gone all day when their solar DHW sits and waits.
so if the systems is sitting and waiting, dump heat into the house. either way the boiler will have to cover the short comings.

theres no getting around having too much in summer, I have the same problem with my PV panels.

ross I'm in the keweenaw area.

jp_2

collector efficiency

hot rod, I haven;t priced the difference between a flat plate and a pool collector but a piece of lexan across a pool heater might be worth it? boxed in of course.

hot_rod

can it take the heat, Lexan?

this article in HPAC mag shows Siggy's calculation for stagnation temperatures in a no flow condition. Try running them with evac tube specs for an eye opener.

Stick with a tried and true flat panel collector, hard to improve on the simplicity and performance.

Ther is a company selling a solar roof solar collector using aluminum fins on, or under the roof? Condensation needs to be considered.

There was a product called Solar Attic ( I think that was the name)). Basically a hydronic unit heater with a condensate pan below. It pre-heated DHW while blowing heat from the attic, simple enough. A bit more multi purpose than the large whole house, noise maker, attic fan I now have.

hr

jp_2

The Test

easy enough to test hot rod, as with the soaker hose, it will be fun and simple to see what comes out of it!

really not trying to re-invent the flat panel collector, just looking at options for the average house hold that can not afford flat panels let alone e-vacs.

nugs

all this talk of home made collectors brings me back to the 70's........not in a fond sort of way.

What you will end up with is a bunch of stuff, up on your roof that will have cost you maybe a couple hundred bucks and never will it have achieved its intended purpose. Save your money up and invest in some good panels. Buderus makes some very fine flat collectors. So do many other companies.