First month of solar

July 28th, 2010
First month solar

First month graph of solar power

The solar array was turned on for real 30 days ago; in that time, it’s produced 389 kWh of energy, which covered 96% of our usage for the month.  I’m pretty pleased with this! As compared to household use, it was:

  • 389 kWh gross production, of which
  • 230 kWh net was pushed out to the grid (meaning 389-230=159 kWh were used directly), and
  • 245 kWh net was drawn from the grid

So, we used a mere 15kWh more than we made.  I blame it on my niece’s baking in the electric oven ;)   (and the need to run the dehumidifier a few days; it was very rainy).  404kWh for the month was actually a fair bit higher than the last several months; the other big hitter was running the fans a lot due to the heat.

In terms of daily output, we saw:

  • Peak power output of 2185W (I think this is due to a 199W limit on each microinverter)
  • Maximum daily energy – 18kWh (on the first day of operation!)
  • Minimum daily energy – 5kWh
  • Average daily energy – 13kWh

What I really miss now, though, is the whole-house energy monitoring that I had; we climbed in usage last month, and I can point to some causes, but I’m flying blind now.  I’ll have to break down and buy a Ted 5000 if I don’t manage to put together my own monitor with CTs soon.

Solar Monitoring

July 3rd, 2010

Solar Monitor ScreenshotWhile the Enphase Enlighten monitoring site is pretty swanky, it’s slow to load and extremely flash-heavy.  It has the advantage of being able to do per-panel monitoring, event log monitoring, etc, but I was hoping for something a little more lightweight.  Enter pachube.com.  Let’s build out the internet of things….

The Envoy system monitor for the Enphase inverters has very basic output monitoring abilities; it shows you current power, and daily, weekly, and lifetime energy production.  So, we can screen-scrape this and upload it to pachube, then do what we like with the data.

I have this script on a 5-minute* 10-minute cron job to get the data.  The Envoy doesn’t seem to update faster than 5 minutes, and it’s such a gutless wonder, doing it any more often than that brings it to its knees, and it stops updating the main site!  If you have problems, you may want to reduce the updates to 15m or more.

To use the script, first get a Pachube API key, and set  up a new Pachube feed.  Add 4 datastreams, for instantaneous power, daily production, weekly production, and lifetime production, in that order.  Edit the script to add your envoy hostname/IP, your API key, and your feed ID.  Then put the script on a 5-minute cron job.  You’ll start seeing the data on a Pachube feed page like this.  Then you can use some of the apps highlighted on apps.pachube.com to create widgets as in the image above, as seen on this page.  You can even get an iPhone app to monitor the data, or create an OSX dashboard widget from the HTML objects!

*Edit: Don’t set the cron job to be more frequent than 10 minutes.  I’ve had trouble with the Enovy unit bogging down and not reporting to Enlighten if you hit it more than every 10 minutes (!)

At last: Solar is running

June 28th, 2010

solar-meters

I got the meters installed today.  It took about 2 minutes of work, after 2 weeks of wait.

The meter on the left is the “production” meter which measures how much power the panels have made over their lifetime, period.  It’s so the utility knows what they got for their rebate money.  (Oddly, it’s the exact same Centron C1SC meter I had previously, for usage measurements!)  The meter on the right is the net meter.  Today it’s running backwards, even though it’s cloudy, because the house is pretty much at base load.

All that’s left is the anti-islanding inspection*, but my installer tells me the utility is OK with having them on prior, so we’re up and running!  On a cloudy day, of course.

I don’t yet have the official Enlighten URL for the array, but my homebrew monitoring is here on pachube.com.

*And one concern about the physical install of the panels & cables, which might possibly require removal and re-fastening of the panels, which would just be awful at this point.

Edit: The official monitoring site is now active.

Waiting is the hardest part.

June 22nd, 2010

Ugh, solar work has been done for over 2 weeks now, and I’m still waiting for some 3rd-party utility subcontractor in a van to come plug a meter into the socket so that it will actually do something.  Bureaucracy sucks.

Solar is all up.

June 4th, 2010
11 x 230W Siliken Panels, Enphase Microinverters

11 x 230W Siliken Panels, Enphase Microinverters

Well, it’s all up and connected; just need a couple inspections and some new meters.  And a little more work in the panel… I’ll have to do a writeup of the whole process at some point.  All in all, it went pretty well I think.

Solar Starts!

June 1st, 2010
Rails for Solar PV

Rails for Solar PV

Subcontractors showed up today to put on the standoffs & rails for the solar.  Picture above is about half done… they’ve apparently done this “once before” so I sure as *#$@ hope they measured twice and cut drilled once on my brand-new roof!

sandeen.net now thinks it’s a laptop

May 20th, 2010

dual_laptop_drives

One of the legs of the main mirror of this box was starting to throw SMART errrors, and that makes me nervous, even when I can remap the sectors.  So when life gives you lemons, make lemonade!  I replaced the main root mirror with a couple new drives – 7200RPM seagate 250G laptop drives, on sale from newegg, the pair $90 with free shipping.

And now, the box uses only 41W, down from 51W.  That’ll save 7 kWh/month, 88kWh/year.  Not bad!  (though far from paying for themselves).  The 2 old drives are still there, waiting to be spun up when somebody wants to listen to the music on them.

OPOWER!

May 16th, 2010

So, Xcel Energy was sending out fliers from OPOWER on a trial basis, trying to make peer pressure work to convince people to reduce their energy usage by comparing them to neighbors in similar homes.  OPOWER claims fantastic results from this, by simply making people aware of their usage and how it compares to others.

Sadly, it seems that this approach does not work for many conservatives.

Anyway, both my brother-in-law and my neighbor got the flier; I did not.  My brother in law went so far as to “feel really bad about it” and then put it in the circular file.  My neighbor filed his away for “later.”  Failures?  I dunno.

Anyway, the interesting thing is that there was a URL on the flier I saw, for the Xcel/OPOWER site at http://xcelenergy.opower.com and it turns out that you don’t have to be randomly selected to be able to sign up for online access.  It’s not exactly the same information as was on the flier, but it’s still interesting.  And, you can even get daily usage over a week, which is something I’ve been wishing they’d provide since forever…. Aside from that, it’s the usual pap about “seal up household leaks” and “buy a programmable thermostat.”

What’s up with the Intel Atom?

May 3rd, 2010

So I was all fired up to lower the power consumption of sandeen.net, the humble server upon which you read this blog.  (And thank you for that, by the way.  You can count yourselves among the 3 finest people on the internet.)

I decided to swap out the old AMD Athlon for an Intel Atom – you know, that low-power, lower-performance wonder-chip from Intel.  I ordered a Gigabyte GA-D510UD from newegg.com, for $90… it looked interesting because it had 4 SATA ports built-in, which should suffice for any amount of storage that I’d likely have connected directly to it.

sandeen.net draws about 51W, which is really not too bad considering there are 2 active drives in it (a mirror) and one sleeping drive that gets backups occasionally.  It’s a AMD Athlon(tm) 64 Processor 3400+ in an old Compaq SR1710NX that I got cheap 5 years ago or so, and updated the cpu, memory, drives, etc…  These new low-power Atoms must be really great then, right?

So it gets here Friday, and I’m all excited… I take down the server, plug it in, and well, first off RHEL5 was not happy with it, bringing the drives up as /dev/hda, /dev/hdb… (remember those?), and and after a bit of fiddling to get the config right I decide to just put things back as they were, and play with the board offline.  Before doing so, I check the kill-a-watt… hm, still 51W.  Odd.  Hopefully a newer distro will do some magic power stuff and make it all better.  It’s an atom right?  Low power and all?

So I put the RHEL6 beta on it, and get it all fired up, and re-check … hm, nope, still 36W or so with a single drive, subtract out that 8W, the board is pulling around 27W.  This is not the low power I’d hoped for!  So I start digging – oh look, the chip doesn’t support any P-states, and only 2 C-states:

Cn                Avg residency   P-states (frequencies)
C0 (cpu running)        ( 0.3%)     1.67 Ghz   100.0%
polling           0.0ms ( 0.0%)
C1              137.5ms (99.7%)

And sure enough, checking the Intel docs, only the chips designed for mobile use have the nice power features.

In short, the shiny new low-power Atom sure appears to use just as much power as my 5-year-old run of the mill AMD Athlon64 (in a low P-state, granted).  Sure, at full-tilt maybe it’s using less, but it runs at full-tilt all the time and my Athlon is able to throttle back almost all the time.

I’ll eat the restocking & shipping and send this thing back to newegg, bitterly disappointed.

I have higher hopes for swapping out the hard drives (one leg of the mirror is dying) to WD Caviar Green drives – I can save about 8kWh/month with those if the specs are accurate.  :)

Cheap DIY Solar at $0.09/watt

April 18th, 2010

clothesline

There are a lot of silly DIY solar scams out there, but here’s the real deal.

Consider:

  • An average electric dryer run uses about 3.3 kWh of electricty
  • An average home might run 150 dryer loads per year
  • This equates to roughly 500 kWh per year for drying clothes

Let’s say you wanted to “go green” for your laundry drying needs by “going solar.”  How much solar PV would it take to dry this much laundry?  According to the PV Watts website,  a 500W (0.5 kW) PV system would yield about 612 kWh in a year here in Minnesota.  That’s a bit more than the dryer is taking, but panels are commonly 230W these days, so let’s round down to a 460W system, and say it’d net somewhere around 500 kWh in very round numbers.

Hm, or you could just not use your dryer, and hang your clothes outside!  How much might that save vs a solar setup?

Ok, you can’t hang up clothes in a Minnesota winter.  So let’s cut the potential in half – 250kWh/year of clothesdrying in the summer, and this would take about a 230W solar array to compensate.  Let’s say $8/watt for a solar install – really, for a small job like this it’d be more, but again, round numbers – this leads to about $2000 for a panel, inverter,  installation, and hookup.

Or – you could spend about $20 on a couple of retractable clotheslines, and have the same net effect, plus the zen-like serenity attained by taking a little time out to do a simple task like this outdoors.  $20 for the equivalent utility of 230W of solar … at $0.09 per watt!

(This really is a fine example of why any good solar installer will tell you to do everything you can to conserve first – it’s much, much cheaper!)