Well, we redid the siding on the house and I am very hesitant to cut a hole in it to reinstall the OASys. Besides, it's probably a good idea to reaffirm my baseline A/C energy usage since we have done some home improvements that might change this.
You may have noticed the cooling summary on the right-hand side, and how 2007 shows significantly less energy usage during the monsoons. What changed? Well, two things. First of all, I was extremely stubborn. Second, we were out of town for the last two weeks of July. This trip combined with my stubborness convinced us to "hold out" the two weeks in early July, knowing we'd be leaving for Wisconsin soon. And when we returned in August, we were refreshed and willing to hold out another couple weeks before succumbing to the discomfort.
This year, my resolve has deteriorated to the level of the average consumer, and we've kept the home quite comfortable by just about anyone's standards. The general rule of thumb is actually extremely accurate: If the average dewpoint approaches 55F, it is time to switch back to A/C. Likewise, once the average dewpoint falls below 55F, it may be time to switch back.
I added a weather meter to the right-side and will be watching this. Once it looks like 55F+ days are over, we will be flipping back to evap. Historically this seems to be around the 2nd week of September. So, perhaps 10 weeks is the average window to avoid evaporative cooling, which leaves about 22 weeks for evap, so it's not all bad... Although a lot of those weeks are mild... We still have June and you'll never take that from me!!!
We were doin' OK until that downpour Thursday night. That was the nail. There is only so much evaporative cooling can do when it is 100 degrees and 40% RH. That being said, it was better than nothing with indoor highs of 78 degrees. However, the dew point was apparently above 70 degrees which was making the refrigerator sweat. Probably not a great idea...
In fact, even multi-stage evaporative cooling alone simply cannot work when it is 100F and 40%RH, as far as I can calculate. The best you could do with a really good series of heat exchangers is reduce the temperature to nearly dew point, with nearly 100% humidity; about 72 degrees. Even if you could cool your home with this supply, the dew point would still be much too high and the humidity would be 80%+.
So, I was thinking, dry the air first. Right? Setup a liquid desiccant system to pull some moisture out of the air first, right? Sounds reasonable. However, to reduce 40% to, say, 25%RH would require extracting about 5 gallons of water per hour. What do you do with desiccant after it absorbs water? You eat it. No. You regenerate it by heating it up. So how much power does it take to evaporate 5 gallons of water in an hour? Only about 10,000 watts, or 3,000 square feet of solar collection.
If you happen to have a ton of waste heat from something, or a spare solar farm, or maybe even a 15,000 gallon tank of liquid dessicant, it might be feasible. I'll be keeping my eye on desiccant systems-- that seems to be the only way to truly have a compressorless air-conditioning system. Otherwise, for the monsoon, vapor compression A/C is here to stay. For the rest of the season, there is evaporation...
