Secret Project - Update 1

Here's a very early look at another nerd project I've started working on.  No hints, I'll leave it to your imagination as to what I'm up to.  More to follow in the coming weeks and months.

Air Conditioner Power

In writing yesterday about evaluating the cost effectiveness of our fancy whole-house fan I mentioned that I only had a way of measuring how much air-conditioner run time was saved by using the fan, not the actual dollars and cents difference.  If I knew how much power the air-conditioner used I could make a rough guess on reduction in the energy bill due to the fan use.

Today, I found a way to measure the power and can now fill-in that gap. The number: ~4kW. (You have no idea how long I've wanted to know this number. This made my day.)

This is an astoundingly high number but I don't know how it compares to other air conditioners. Obviously power consumption depends on size; the window units are rated between 1 and 1.5kW. Our air conditioner is old and I bet its efficiency is not that great but I have so little documentation on it that I can't compare it to other more modern units of equivalent size.  Maybe that will be my next bit of research.

Now for some math: Even with a power bill, it can be hard to figure out the $/kWh we all pay.  Let's assume somewhere around $0.1/kWh, a ballpark number that makes the math easy. Using  $0.1/KWh and looking back over this summer's usage of ~8/day, the energy cost just for cooling is $3.20/day; 30 days in a month brings the total to $96/month.

As far as the cost effectiveness of the fan goes, well, there's still a few more complications.  The easiest one to address is the energy consumption of the fan itself.  Looking this up in the manual shows the fan is rated at 292W on high (which we most often use) .  This is a 1:13 energy consumption ratio between the fan and the air-conditioner.  For ballpark analysis purposes, we could probably just consider the energy consumption of the fan as negligible.  Its a bit of a stretch but my work so far has been just as imprecise and I can live with this.

The second issue is very much related to what I discussed yesterday: how many hours over the course of the summer am I using the fan when I would normally be using the air-conditioner?  The results of the experiment I wrote about yesterday show a 25% reduction (using awful experimental techniques) in air-conditioner usage when I use the fan.  Many days of the summer, though,  I can't use the fan at all as the overnight low is still above the indoor temperature.  If I get really committed I might go back through my temperature data and try to make some kind of estimate; that's more work that I want to mess with right now.  For tonight, I'm once again going to table this.

Effectiveness of Whole-House Fan

As I've written before, two years ago we installed a whole-house fan in an attempt to make better use of the sometimes-colder outdoor air to cool the inside of our house.  The fan has been great but I've been wondering if it was a good economical choice.  Would we have been better off just spending the money on air conditioning rather than this fancy fan?

To answer this question I would need to compare how long the air conditioner runs on days when we use it versus days when we don't.  Oh, and the days would have to be identical. Since I don't control the weather, doing a direct comparison is pretty much not going to happen.  The next best strategy is to find days with similar weather, use the fan one day and not the other, and do this a bunch of times to average out all the actual differences in the weather.  This is a better strategy but has two problems:

1. The decision on whether to use the fan or not must be made without knowing the upcoming weather for the day.  Obviously weather forecasts solve this somewhat but it may be hard to decide if the predicted weather for the day is equal enough to the weather in some arbitrary previous day (where I've already collected your data) to make the comparison worthwhile.
2. By definition, there will be days when I could use the fan but choose not to (so I can collect data for the air-conditioner-only case).  I bought this big fancy fan and I don't get to use it? And I'm doing this so that I somewhat scientifically determine if using this big fancy fan I already bought is doing what it should?  

In light of these two complications it became obvious to me that to do this experiment well requires more commitment to good scientific principles than I can bear right now.  Instead, I did the smallest experiment possible: two days that are vaguely similar in weather one using the fan and one not, measuring the amount of time the air conditioner runs on each day.

This graph shows the outdoor temperature on the two days I ran this experiment. The days are far from identical but do have a similar daytime highs and general temperature trends throughout the day.

The measured air-conditioner runs times are as follows: fan + AC: 3.8 hrs, AC only: 5.1 hrs.  That's a time savings of 24% when running only the fan.  The real question is how much money this saves me and for that I need to know how much energy my air-conditioner uses.  I don't have a way of measuring that at the moment but I've got one in the works. For now I'm going to have to be satisfied with run-time.

UPDATE: I've got a partial follow-up where I get an estimate of the air conditioners power consumption.

Memorization

At the beginning of the summer one of the pastor's of my church challenged the congregation as a whole to memorize a particular book of the Bible, James 1.  Memorization is not my strong suit but I am not one to turn down a challenge so I dug in.  Well, at least for the first month or so during which time I got about half way there. During a sleepless night last night a thought came to me: my Mac can convert text into speech and I bet those spoken words could be saved as an audio file.

It can.

Here's the workflow to download if you feel frightened by the idea of building it yourself in Automator.  The file needs to be placed in your ~/Library/Services/ folder, that is, the Library found in your home directory. (If you want to make it available for all users of your computer, just place it in the global library folder /Library/Services/).  If you don't have a Services folder in your library just create one and drop it in.

To use the service just highlight the desired text, go to the menu of that application, select "Services" and then "Text to AAC".  The workflow will create an AAC audio file out of that text and save it in your iTunes folder as a song called "Text to AAC Output". Not only is this a neato demonstration of a built in feature on all Macs, but it has been actually useful in helping me with my memorization.