Solar Heat Collectors? (non PV)

Started by Thoughts-from-Jules, January 05, 2010, 04:54:13 AM

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Thoughts-from-Jules

So I have always planned to try to incorperate some passive solar elements to our future home.  Wouldn't you know it the land we are considering has amazing views in every direction BUT the south, so I hate to add all the glass towards the south that is the least favorable view!!  So I was thinking about solar heat collectors like found here http://www.builditsolar.com/Projects/SpaceHeating/solar_barn_project.htm  or here is a little more classy version http://www.yoursolarhome.com/solarsheat.com/solarsheat/index.html

Anyway I wondered if anyone else has tried these methods?  I think maybe I'd like the automated ones that automatically close the vents when it reaches a cooler temp at night would be good, I don't want to be having to worry about closing vents and remembering open them again etc.  This is just for supplemental heat in addition to a fireplace or woodstove and while we are gone I was hoping it might keep it above 50 degrees without having to run the backup furnace.;)

We are still very much in the planning stages, which I enjoy very much.  Trying out different ideas, floorplans and trouble shooting.  So give me your thoughts on these sort of solar heaters.

I just can't see myself spending all that money on glass to a view I don't love, when there is an amazing view on the other two sides of the house!  Nope can't do it! 

I might try working up a greenhouse/solarium version though...where you build a narrow greenhouse on that side (we were going to build a detached greenhouse anyway down the road).

I can tell this forum is going to be alot of fun!  I love the atmosphere here!
Julie~        "The Future Comes One Day at a time."

Mike 870

I haven't tried any of those methods, but I will say,  I am on a fiarly steep north facing hill, and I still have excellent solar exposure in the winter.  My great views are to the north and west too.   You may still be able to catch some good gain with some single pane south facing glass, and catch some great views with double pane low e etc. to the North and West.  My home is conventional and I didn't build it, but after living in it, I'm convinced almost any site can be overcome with sound design.


Squirl

It looks like you picked out solar hot air collectors.  They are one of the many solar heating options.  They are similar to passive solar.  I have lived in passive solar homes myself, but never with solar air heaters.  They have their advantages and disadvantages.  The advantage is you can live with less windows for less heat loss at night and have more insulated square footage.  They are also the lowest cost of probably all methods. The disadvantage is the sunlight does not directly strike thermal mass heating it up.  It instead heats the air then the air heats the thermal mass in the house.  This is less efficient and I would assume lead to higher daytime temperatures and lower nighttime temperatures.

Active solar closed water systems are probably the most constant and efficient, but also most expensive. 
http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

Thoughts-from-Jules

I was thinking about the thermal mass situation too knowing I was going to be losing out on some benefits there.  I might have to rethink the greenhouse part where the greenhouse protion is your solar heat collector etc.  I was thinking that since we really only wanted one fireplace and or woodstove unit that either we'd try to do the optional ducting with the fireplace (I've seen where they have kits for certain fireplaces) to other rooms or upstairs......basically I don't want to be packing wood upstairs to a second woodstove etc.  So my idea was to use the solar heat collectors that vented the hot air to the upstairs low on the exterior wall like a heat register.  Or maybe someone could tell me how well heat from downstairs stove/fireplace will travel up the stairwell?  Might not be something I really have to worry about?

Anyone ever seen the following design idea?  I like the theory but I am not sure how well it really would work since I haven't seen many homes that use it....and most of the example homes are from the 80's.  Not sure how much more it would cost to do the changes he talks about.  http://www.youtube.com/watch?v=lzGaLw__kdk&feature=channel http://www.youtube.com/watch?v=zCu03k_Ke5o

Also what is the cheapest solution for backup heating?  We will likely have propane delivered, an electricity available.

I think having warm floors would be great with a soalar radiant heat system, but I really don't like the idea of a bunch of waterlines in the floors either.  Too many times of having to dig up Grandpa's concrete floors when the boiler system leaked!  I know now days the materials are better but I just don't see us doing it due to expense.  ;(

In our current home which is 1350 sq ft we use a wood stove 80% of the time and we have a gas furnace under the house that is pretty efficient and we like it.  We also have AC and Heatpump (although we never wired in the heatpump part for the thermostat).  We probably won't be doing central air conditioning in our new home due to the higher elevation and breezy ridge we should be able to manage.

Julie
Julie~        "The Future Comes One Day at a time."

John Raabe

It is always nice when the views and the solar exposure are in the same direction :D :D :D. Then you can use passive solar techniques such as mentioned in the Youtube video. My own solar sunroom house (Solar Saltbox plan) uses good insulation, thermal mass and a sunroom to the south.

However, you also want to adjust your solar expectations to the realities of your specific site and climate. I have a booklet on these simple solar techniques in the Sunkit. Not all solar techniques work the same everywhere and a lot of money can be spent on things that won't work as well as expected, especially if you are in a northern latitude with cloudy winters.

Finally, you can often have south facing windows up high in a backwards facing clerestory design. This can bring light and warmth into a house that faces the "wrong" direction.
None of us are as smart as all of us.


Squirl

There are a lot of questions there.  For woodstoves. One in the basement or downstairs can heat the floor above it well.  I have seen people install removable panels or grates into the floors to aid in this, although not always necessary.  Heat rises, and if you have well insulated walls and floor, there isn't a lot of other places for it to go.

I like your ideas.  I assume by all these questions you intend to have a second floor.  Your reservations about heated flooring are a valid concern.  People use regular old radiators too.

Cheapest solution?  Well that can get complicated. Commodity prices can change from year to year.  This definitely falls under the "it depends" answer category.

BTW, Fireplaces are really beautiful and really bad for energy consumption.  I recommend a wood stove.

pagan

I'm interested in the PAHS design, but I don't think I'll be able to build underground or even earth bermed because my land is mostly ledge. My thoughts lately have been about storing as much heat through the summer to use in the winter. What do you all think about using the evacuated tubes to circulate hot water or glycol through a massive heat storage medium like water or sand that's in a super insulated container? Do you think it would be possible to store enough heat through the summer to last through the winter?

John Raabe

#7
Seasonal storage is a captivating idea that has not proved cost effective in all but the best solar climates. (You can do a forum search on "seasonal storage" for an earlier discussion.)  In the NE, and most mid-latitude climates, it would not be a viable consideration unless you wanted to drop $10-15k on an experiment. (Hint: In the north, you would have to heavily insulate the area where you will store the heat - when you calculate your yearly heat storage needs you will likely make that a heavily insulated concrete cistern with water as the storage medium).

Upgraded insulation with a deep well ground source heat pump would likely be much more cost effective. It actually does use long term seasonal solar storage as a heat source. ;)

PS - Please let me know if anybody has found a link to a system that uses uninsulated soil as a "seasonal" thermal storage medium and the house was built in cold northern soil and NOT the desert SW where you are quite far south (high sun for a longer part of the day) and you have 300+ days of high heat content sunlight. Hopefully such a system has been documented and not have just anecdotal stories from the designer or enthusiastic new owners.

PPS - I spent several years trying to perfect another captivating solar strategy: double wall "Envelope Houses" Note the date of this article - that was when I was designing them. Ultimately there were safety issues (fire code) and the construction costs didn't really justify the thermal savings in northern climates like the Pacific NW. However, most owners loved the light and the indoor/outdoor sunroom space.


Solar Envelope house at the head of Lake Chelan, Stehekin, WA
None of us are as smart as all of us.