Propane Vs. Solar

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] A GOOD, well-maintained, evaporative cooler can give you seventy-degree air on even really hot days. The trick is to MOVE AIR, and have very low humidity. CFM is a very important number in the equation, and the other consideration is being able to open the house to vent hot air without letting scum in that will rob and kill you, so this has to be designed in from the outset. Does anyone remember the old hotels that were AIR COOLED? The hallways were the suction so the transoms above the doors to the hotel rooms could be opened to let hot room air go into the hallways and then be replaced by cool night air entering through the open window. That was pre-air conditioning, and it was a BIG selling point to attract guests. As cities developed, the evapotranspiration from the trees that were planted caused the humidity to rise and that made it more difficult to cool with just night air and also reduced the effectiveness of evaporative coolers. [img]/forums/images/icons/tongue.gif[/img]

[lliefveld]

We looked into evaporative cooling (i.e. swamp cooler), and our neighbor has one. For the most part, we don't have a lot of humidity, but the problem is that when it gets hot... that's when it seems to be humid... and there's nothing worse than being hot AND humid <g>. I've recently read about cooling tubes, and that does interest me, but the ones I've read about need to be pretty deep in the ground, and I'm sure we'd have to blast in order to do that. The topsoil is about 6 feet deep - then granite. Some is decomposed granite that's really good for our road, but a lot of it isn't.

[lliefveld]

Oh, I just love those old hotels. The first one I saw like that had been converted into housing for unwed mothers, and I was helping out doing some 'fix-it' work with the company I work for. At first, I couldn't figure out what these 'windows' in the hallways were for, with a door on them. I opened the door and they opened into an air shaft. It didn't take long to figure out it was for air circulation and cooling. I always thought that was a really great idea.

[Bird]

Weren't "attic fans" pretty popular years ago? Just a big exhaust fan, usually in a hallway, to pull the air up into the attic, and of course that pulled air in through open windows. We never had one ourselves, but the ones I saw seemed like a good idea.

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Anywhere you have a good day/night temperature differential you can use the "air cooling" approach for next to nothing invested in terms of electric power. If, however; as "Veld" has pointed out; some hot spellls are often accompanied by higher-than-average humidity, then you need to go searching for another alternative. THE BIG PROBLEM IS.......in order to make an air coil "sweat" and do a good job of removing humidity, you need to be in the fifty-five to sixty degree range. To get that cold, you need a bonafide chiller and that means refrigeration; which circles us back to the "ice pack" system. [img]/forums/images/icons/crazy.gif[/img]

[Bird]

</font><blockquote><font class="small">In reply to:</font><hr />
Anywhere you have a good day/night temperature differential you can use the "air cooling"

[/ QUOTE ]

I agree, or anywhere that you have no choice. [img]/forums/images/icons/frown.gif[/img] When I was a kid, we had nothing but opening windows. In fact, sometimes in the summer, we moved beds out into the yard to get out of the heat in the house. In my later teens, we had a big evaporative cooler in the living room but that was the only room and it was always shut off at night. I was 19 the first time I ever lived or worked where there was any kind of air-conditioning.

[Pat]

Dave, If the RH is high enough I don't care if you power the cooler with a supersonic wind tunnel you won't appreciably cool the air.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[Pat]

Loretta, If you try cool tubes don't use aluminum. Do slope them away from the house, Do plumb them to permit filing them with a bacteriastat and then draining. This can be as simple as a valve or plug at the inlet end and access to the hoiuse end where you can pour in bleach solution or your choice of sanitizer and then flush with clear water. This will stop spore problems from stuff growing in the tubes, shoiuld it happen.

The other methoids I alluded to using cooling towers all rely on evaporation so NEVER MIND!

If your periods of heat and humidity result in sultry nights then yoiu have my sympathy. If the nights are still cool the whole hoiuse fan and lots of thermal mass will help a lot. An undersized refrigeration system that runs all the time and barely controls the temp is about as good a dehumidifier as is available with standard techniques.

If you want to go a bit higher tech and get better dehumidification with seriously lowered energy input requirements then look into "heat pipes." These have been productized and made into retrofit kits for refridgeratioin "A" coils or can be purchased pre installed in packaged "A" coil units. The technology isn't particularly cheap but works very well and has virtually no impact on your energy consumption while SIGNIFICANTLY increasing dehumidifiatioin.

If you sufficiently reduce the relative humidity you don't need to lower the actual temp all that much to be comfortable.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[SLOBuds]

Well, quite a bit has gone on here since my last visit ... on the post AND on our energy strategy.

We finally have enough data to analyze with a degree of accuracy. The base heat loading of the new house is established, and we have mechanicals understood enough so that we can estimate use of an all-electric solution vs. a propane gas solution.

California still has incentives here and there which help with the financials. In our case an all-electric house, with sufficient solar photovoltaics to 100% cover our electric utilization, pays for the entire system within 7-10 years. Afterwards there is an additional 10-15 years of service life for the equipment when it starts all over again.

So we basically have to decide whether we are planning to live in the house for 10 years. Of course there are other things we think about such as the 'goodness' of doing this (in our opinions, at least). And the going-in cost is dramatically more which is also a consideration.

The inflation rate of energy costs is an unknown. But we are willing to bet that the RATE will increase. Possibly the incentives will increase as well.

The cheapest way to reduce energy costs in a new house is through BUILDING a good house (eg insulation, etc), and conservation. We have gone as far as we can with those items.

Within a couple of weeks I will have soft copies of our analysis. Send me pm at mjp /at/ slobuds /dot/ com if you would like to get a copy.

The cooling topics above don't apply to us. Our base performance on the new house will yield interior temperatures of high-70s, on exterior temperatures of 115-120 degrees. We can only achieve that because of insulation (straw bale), high-quality windows, south-facing orientation, overhangs, and most importantly a COOL night every night which is always low-60s regardless of the daytime temperatures. Whole house fans will be used to expel hot air each night.

We are happy with the way the house has turned out from an engineering perspective. We wanted to try to achieve zero ducting and it has worked out that way exactly. But only because of our kindly Mother Nature for the most part.

Here is the floor plan of our house:

Petersen/Pilj Floor Plan

Exterior elevations:

Petersen/Pilj Exterior Elevations #1

More exterior elevations:

Petersen/Pilj Exterior Elevations #2

An excellent string!

Thanks,
Martin Petersen

[Pat]

Martin, Great stuff, man. You are dong good. That is the "instant response." I'll study on the info when I get a chance.

One thing... as "Columbo" oft intoned... Over time there is a tendency to "inadvertantly modify" the engineering.

For example: One of the great benefits you have is cool nights that allow you to flush out heat and precool storage masses. Slabs, masonry walls and other heat storage masses inside the structure are good things for your performance. Guard against the proliferation and encroachment of throw rugs and such over ceramic tile or wall coverings like tapestry as the R value will prevent the desired action with the thermal mass.

I designed and built a, dare I say it, terrific sun porch for my mom. She loves it, practically lives in it. her plants love it. It has never gone below freezing in 5 winters. After 2 years she wanted a carpet on the floor. I talked her out of it, barely. It would have destroyed the function. It would have overheated on a sunny day and gotten colder, most likely below freezing on a cold night. As it is when it is sunny with 50F days and 28-34F overnight low it is 80-82 in the early afternoon and drops as low as 60's overnight in the sun room.

With a carpet it wouild get hotter in the day (you'd have to open several windows) and then get colder at night since the slab would not have stored much energy. As it is she keeps a minimum of one window open a couple inches ALL THE TIME.

Later,

[img]/forums/images/icons/smile.gif[/img] [img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img] [img]/forums/images/icons/smile.gif[/img]