First Full Month of Solar

As April ends, I can now assess the results of our first full month of having solar power. Specifically, I was very interested to see if my projections for solar production were even close. If you remember, I wrote this blog entry back in October 2009 as I was trying to determine how big a system to get, what sort of output I could expect and what my savings would be. I created this Google Docs spreadsheet to help with all these calculations.

For the month of April, the spreadsheet predicted for the 3.68kW system we got, production of 513 kWH (this actually comes from the PVWatt tool mentioned in the spreadsheet). It didn't look like we'd get there as the 27th and 28th were overcast and rainy days, but the last 2 days of April turned in the highest production so far. Actual production came in at 538 kWH. Based on this, it looks like the analysis I did in the spreadsheet turned out very accurate and as a result, I'm very pleased with our purchase so far.

Dog Sitters: Don't Shortchange Customers With Automated Homes

We recently went on vacation for a few days and had a dog sitter/walker take care of our dog while we were gone. We had the sitter visit our dog during the day to walk, play with, feed and clean up after him. We chose the duration of the visits and were billed accordingly. To get to our dog, the sitter had to open the side gate, which of course, is monitored and logged by our system. I used that information to gauge when a visit started and when it ended. Our security cameras, which are recorded, could also provide an extra confirmation if needed.

Unfortunately, the results are not good. There was not a single visit where the sitter stayed for the duration we paid.

Visit #1: 18% short
Visit #2: 50% short!
Visit #3: 33% short
Visit #4: 26% short
Visit #5: 23% short
Visit #6: 28% short

Overall, we were billed for 28% more than the actual number of minutes. My wife and I were stunned by how the sitter consistently shortchanged our pooch and not just by a couple minutes. For example, a 30 minute visit was really only 15 minutes and a 1 hour visit was cut short by 20 minutes. All those 5 star reviews on Yelp must have been written by friends or completely clueless people (AKA normal people without automation systems).

Our dog is a very important part of our family, and it bothers us more that he was shortchanged on attention than us being ripped off. Needless to say, rather than confront the sitter, we are going to cut our losses and find a new service (and put up a review on Yelp). This brings up the question, is it really possible to find a sitter who actually stays for the agreed upon durations? You are really at the whim of the sitter's honesty and it seems really easy to cheat. How do you guarantee you get what you pay for?

Overcast Day Has Greater Solar Intensity???

It seems counter-intuitive, yet on a cloudless, sunny day, our panels peaked at a lower electricity output than on a day with overcast. In fact, on the cloudy day, our panels maxed out the inverter, causing it to clip. See the graph below where I combined the charts of 2 different days.



The red line shows the nice production curve on a cloudless day, but the green line shows the output on a cloudy day. The green line maxed out earlier in the day and even later in the day than the red line.

The sunlight hitting earth must be reflecting back up to the sky, but the overcast is causing it to reflect back down again. This results in more solar energy hitting the panels. I would assume that the glass over the panels is like this as well - allowing the sunlight to pass, and some light that reflects off the panels would get reflected back to the panels by the glass.

Waiting for the Axe to Fall

It's been a quiet several weeks. There have been rampant rumors at work that the company is planning on shuttering my group. It's something that we've been expecting at work for the last 3-6 months, but as quarter end nears, it's possible that it may be right around the corner. So I've been a little preoccupied to do any HA stuff other than mindlessly monitoring the production of our solar panels. According to the latest rumors, the axe was to fall last Friday, but upper management had to delay it since they're waiting for our group to finish up some work before they'd be comfortable canning us all. As I sit here contemplating impending joblessness, I wonder what my next career move will be. I'm an ASIC design and verification engineer, but I'm burnt out on it and a change of career may be in the cards. I've got an unused MBA, some .NET programming skills and experience with AJAX, PHP and MySQL, so I have some options to explore. In the meantime, feel free to donate! ;).

xPLBattWatch - A Battery Charge Monitor

This is the first release of xPLBattWatch. This app is used to monitor the battery level and charge status of a laptop. It issues sensor.basic messages based on changes in the charge level and status. It may be a little rough, but I thought I'd throw this out there and let you play with it. More details and download here.

Solar Array Powered Up and Some Graphs

The installer powered on the solar array on Tuesday after the inspection. After he left, I installed current sensors for the solar breakers and ran those along Cat-5 back to the ECM-1240. I was debugging the charting and got it pretty much sorted out by Wednesday night. Here's the first few RRDTool graphs from Thursday.


You can see it generated nearly 21 kWH yesterday. I'm really happy with that as we typically use 22-25 kWH/day. I didn't expect to get that much production in March. Does this mean the assumptions I made in my Solar Spreadsheet may have been a little pessimistic? There's still a lot of rain & overcast in March (of which we're seeing today), so it will probably average out. We'll have to wait for April to get a good full month to compare.


With a southeast facing roof, you can see we catch the morning sun very early. The array woke up around 6:22AM and peaked around 11AM. Once the sun passed over the top of the roof around noon, production started to drop and around 2PM it started to decline rapidly. By then, it produced about 80% of the total for the day. I wish I had room on the west facing roof to catch the afternoon sun, but it would only fit maybe 4 panels - good for another 1kW. Maybe when we get an EV ;) Production stopped almost exactly at 6PM. You can see some of the spikes in production as the sun was behind some clouds.


This is just a net usage graph. Solar production for the day caught up to our daily usage by noon. Between 3-4PM, production fell below our usage and about 9PM, all our credits were used up. For yesterday, we basically paid the utility for electricity for the 3 hours from 9PM-12AM. Pretty cool.

xPLWebControl Released

I released an xPL interface for CAI's WebControl. The app communicates with the WebControl via its web interface since it has no other means of control. You can read more about it and download it here.

New Toy: CAI WebControl and Random Updates

So I finally broke down a bought a WebControl device. It's a network enabled IO device that's been discussed heavily at CT and HS message boards. I got it from this seller on eBay. I'm surprised it actually powers on. It was shipped in a USPS Flat Rate Priority envelope. The device itself was in a small bubble pack pouch - just a single layer of bubble pack to protect the sharp corners of the device's components. The corners of the ethernet jack poked through the bubble pack, puncturing the envelope in several places. For $8.71 in shipping, is it too much to ask for 2 or 3 layers of bubble pack????

Anyway, I powered it on, assigned it a static IP address and new login info, but didn't get much further than that. I hope to test out the digital IO and 1-Wire interface this weekend before I'll believe it's undamaged. I have no idea what I'm going to use it for. I am planning on building an xPL app to interface to it, but I'm not in any big hurry. Still feeling a bit burned out on HA.

It's been 10 days since the solar installation was completed and I haven't heard from the city about inspections nor has the utility swapped out my meter. It was frustrating waiting nearly 4 months from signing the contract to the installation (due to weather & backlog), but this is even more frustrating because I just want to flip the switch!

This week I did update xPLTweet and Jab2Twit to use OAUTH for Twitter authentication. That way there's no stored username & password and has the added benefit of my apps showing up as sources for tweets :)

Solar Panels Installed!

Here is this final product - a Sunny Boy inverter and 16 230W Sharp panels. Installation took only 1 1/2 days. It's all ready to go, just waiting on the utility to swap out the meter and for the city inspector.

ChromeOS on Acer Aspire Netbook

Just tried out this build of ChromeOS. It boots fast, but doesn't work well with my netbook. The trackpad barely tracks and the tap to click trackpad feature doesn't work. ChromeOS really is just the web, but I need Remote Desktop to access my servers. I see no reason why ChromeOS can't have an RDP client - my Nokia N800 does. I liked Jolicloud on the netbook better, as it's really more of an OS than ChromeOS.

New NAS

I just bought a DLink DNS-321 NAS. I'm hoping to use this for SageTV recordings, which are currently stored on the media server. I want to do this since I hibernate the SageTV server a lot, but would like the recordings available.

I'm going to be evaluating whether or not I can dump 4 HDHomerun streams to it while playing from 2 HD200s. I'm guessing no, but it's going to be an interesting experiment. While I was copying the existing recordings over, the maximum bandwidth I was able to achieve was 100 Mbps over gigabit links. An existing 1 hour HD recording took 5.5 GB, so that's about 12.5 Mbps. Four streams would be half of the maximum bandwidth I've seen and that doesn't include playback. If it doesn't work out, I play on using it for backups.

Dog Feeder Demo

There was a recent thread on Cocoontech about pet related automation and this is a rehash of my post there about our automated pet feeder. Here's a snippet from a screencast I did that demo'd some parts of our HA system. This clip shows the automated dog feeder and how it's controlled from our GUI, including calling our dog over using TTS and watching the result via a camera popup. (The TTS audio is dubbed in for effect - it's what was pushed out of the garage MP3 player to the backyard speakers.)