Hello from the Arizona Desert

I've been watching these forums for quite a while, but never had anything substantial to add. Well, I still may not have anything to add, you be the judge. I got into serious home automation a while back when I got an electric bill for over U$400. After I picked myself up off the floor I called the power company to see what the heck that was all about and my adventure began.

Now, I monitor my power usage in real time, have solar heating for the pool, solar water heating. Have displays around the house that tell me how much power I'm using. To be sure I cut power back at the proper time I have a clock synced to the GPS satellite system. I have custom web enabled thermostats for the heat pumps (this is Arizona!). Most of this stuff I built myself. The stuff I didn't build has been modified by your truly to be either more energy efficient or controllable.

The reason I'm showing up now instead of when I started is that I tried using commercial equipment and was very disappointed at customer service, local contractors or the darn company's ability to either answer the phone or return an email. So I spent a couple of years in experimentation and research. I'm not selling anything; to the contrary, I'm totally giving it away.

So, here I am. Go look at my blog draythomp@blogspot (sorry, can't post a link yet). I put things like what hardware pieces I used, where to get them, how to wire them up, actual code I'm running, etc. There are notes on the problems I encountered, a looong explanation of how I got into this and my observations along the way.

Have fun, comments welcome

dave

Looking forward to reading your blog.

http://draythomp.blogspot.com/

Power monitoring is on my to-do list.

Hi Dave,

Welcome to CT! Funny you mention your pool heater system is based on an Arduino. I am in process of doing something very similar (I am skipping the Goldline controller to save money, and just interfacing the probes directly), and was actually considering setting up an Arduino sub forum since others are getting into this as well.

Yes, I have several of the little devices. Two thermostats, a real time wireless power monitor, a cool power display that I put in the wall so I could watch it, the pool controller and a new box that incorporates input from all the others.

If I had known what I know now (we all say that from time to time) I would've saved my money on the Goldline control. Pool heating control is actually pretty easy. Chlorination is more a matter of automatic injection or finding a good generator and valve control is actually really easy. However, I didn't have a clue what I was doing a few years ago.

Well I am all new to this as well, but I do know I didn't want to pay several hundreds of dollars for the controller, which wouldn't even allow me to interface it with my existing home automation setup. What is your favorite TTL->RS232 board? Do you use shifters or the Maxim components? Where do you prefer to buy your arduino components from?

I haven't gone from TTL serial to RS232. Instead, I've been using XBees to communicate. These little radios are pretty slick and have saved me a ton of wiring around the house. Like I show on my web page, I have gone TTL serial to RS485, but only for the one specific purpose. I started out using wifi, but that got too expensive quickly. My favorite place to pick up arduino stuff is Lady Ada's site adafruit.com. However, there are really good deals on ebay from time to time and I frequent Digikey pretty often. For example, a cheap power supply for an arduino is a wall wart designed for the ipad (notice, ipad, not ipod) these things can give you up to 2 amps regulated 5V for less than U$4.00 on ebay. I have five or six of them around the house doing various things. After a little experience with the arduino, you'll feel confident enough to pick up a clone (they're open source) on ebay for less than 20. So, over time the prices drop nicely as you understand what works and what will cause problems.

I'd be interested to hear more about how effective cooling the house down prior to on-peak is at reducing costs and the actual indoor temperature during the day as a result. And also how dependent it is on things like opening and closing doors.

So I only went through the two sections on your homemade thermostat and your overall energy usage/pricing. I'm in an area with smart meters, but we don't have demand pricing - what we have instead is just 3 tiers... If you want to feel a whole lot better about what you're paying in electricity, look at these rates... I'd take your peak billing any day!



Awesome usage though of technology to beat the demand peak - if we had that I'd surely be trying some of these methods.

In my area we have similar temperatures - many days over 110 degrees (people don't realize Sacramento gets that hot - but the temps you see on the news are near the rivers and water; actual measured temps are always at least 5 degrees warmer in the surrounding areas). In my neighborhood specifically, what people are doing is using a whole-house fan at like 6:00AM to use the outside air to cool the house as much as possible, then they seal it up and leave for work with the thermostats set back. Then after the outside temp drops below 75 they open the windows and do it again for a turbo cool - then use the AC set at 78 from there.

Unfortunately in my house, someone is always home, and we like the house at 74 - so we have unpleasant bills.

Once upon a time I had baseline billing, and you're right, it was very hard to keep the bill down. In situations like that you have to use completely different techniques. Here in AZ an awful lot of people don't have natural gas service (I don't) and have to rely on the electrical for everything. I do have a couple of propane tanks to run a stove top and occasionally a fireplace. They cost me about $150 a year to keep filled.

Precooling the house works really well and is TOTALLY dependent on keeping the hot wind from blowing through the house. Just going in and out, unless it's a lot, doesn't seem to bother it much, but get two doors open and it can be an unpleasant afternoon. What I saw last year was: I'd start at noon with a temp of 76 or so and it would rise to 84 by the time I could turn on the AC, there was the occasional rise to just over 90. That happened when I had two doors open and the cool got away. My instantaneous usage at around 7:15 would be 17KW or so to cool the place back down. Of course, the water heater kicked on at that time also, and the kitchen cranked up. I have tile floors on top of concrete so they can suck a lot of heat out of the air if I keep the 45W overhead fans going. People with carpeting don't have that advantage and it does help a lot. Cooling them back down for the next day takes a lot of energy, but at least, it's during the cheap period.

There's a strange advantage I have in this effort, one gets used to the heat. That doesn't mean you want the house at 105, but it does mean that 90 or so doesn't feel bad at all. If you don't keep the house at a constant temperature and allow it to rise to, sort of, follow the weather the higher temps don't hurt so much. The problem with this is when people visit. They freakin' hate the weather! I'm coming into my period of maximum use, we'll see how it goes this year.

How do you power some of the boards? Did you run low voltage wire to the outdoor enclosures, or are your arduino boards solar operated?

You're going to hate this answer.....extension cord with a wall wart at the end of it. I experimented a little bit with a solar-battery arrangement and was totally unhappy with it. The batteries died in a few days because of the heat, the solar cell turned opaque when the cheap plastic gave out in the sun. I WILL get back to this idea, but not until I get some other projects further along. I did the low voltage wire thing and that worked really well until a pack rat decided he needed the wire more than me. Stupid rat dug it up, chewed through it and stole about a foot of the wire. The strange thing is that I have a 110V extension across the yard and it's been there for a couple of years and the rabbits, ground squirrels and rats all leave it alone. The snakes kind of like to lie down along it sometimes. Funny isn't it? Here where the sun could be truly used to help out, the products can't handle it. I'll look into glass covered cells at some point; haven't got a clue about the batteries dying though, that may be a little harder to solve.

Yes, I really do live in the desert. Not in a town in the desert, in the desert. The cactus are blooming too.

Wow, just read your FIRST post in your blog. Wow, demand metering? Sounds pretty bad. I guess at those increases ($60 for $0.10 in electricity) it seems to make sense to just get a HUGE inverter to power the whole house, and even if you don't hook in solar panels, have that whole house inverter pull shore power to charge the battery bank...which is really what powers the house, so you don't get hit with huge surges like that.

--Dan

Demand metering, while it sucks, does offer opportunities to beat the system. I started looking at a battery bank and house size inverter to store power during the off peak periods and then use it during peak. The problem I had with this is that there are no incentives to defray the costs. I'm working from my poor old memory here so I may be way off on the numbers.

If I put in solar, it would cost me about 5 bucks a watt with the government subsidies, around 50 grand installed. If I put in an inverter without subsidies, it would be 7 bucks a watt; 70 grand installed. So it's cheaper to buy the solar cells and forgo the batteries. However, both of them were totally beyond anything I'm willing to pay. I looked into one of those new leases that they have for solar equipment, and though compelling, were based on set systems that they have already set up and they wouldn't give me more than 3.5KW on the roof. While that's a nice number now that my power usage is under better control, I have some reservations about the contracts, quality of the equipment and so forth.

When the plug and play systems get into REAL production.... Those are the systems that have a set of solar cells that terminate in a wall plug and you just plug them in. They look like they will cost about 4K per KW and I just mount them and plug them in. I could easily put one of them up, wait a year to see how it plays out and then get another. I could put them out in the yard and just run some conduit to them if I needed more space.

One idea I had was using one of the plug and play systems to power an item. For example, put one in to power my South heat pump. It pulls a max of 3800W when it's running and it's on a LOT during the heat of the day if I let it. So, a solar array of around 2KW would pay for it, if I kept the peak demand number low enough by never letting my usage exceed what the solar cell provided. I'm currently too inexperienced at this to figure out the variables in doing this. Plus, I would want to ease into something like that a little at a time to be sure I didn't completely screw up on some portion of it.

I haven't given up on solar, just don't want to make the wrong decisions about it, and I hope at least a couple of the things above make a little sense.

If you are willing to do one or two at a time, with the "just plug it in"...
Why not use the Enphase inverters? You get one inverter per 1 or 2 panels. They call them microinverters. They are only grid tied, and in the end as a bottom line it will cost more, but overall, will cost you less due to inflation and stretching the purchase out over time.

You "can" trick the units to run not on the grid, if you can get a high enough quality pure sin inverter. You just have to ensure you can burn up any excess power if you aren't using it (or sell back to the grid and manually move the Enphase units over to an isolated circuit during a power outage).

--Dan

Dan, that's actually a really good idea. I'll take a look at doing something along those lines over the coming months. I saw the Enphase advertising a while back and was intrigued, but life got in the way and I forgot about them. Thanks for pointing them out.