Computing stuff tied to the physical world

Watts up?

In Hardware on Nov 14, 2012 at 00:01

Ok, so all the solar panels are in place and doing their thing (as much as this season allows, anyway). But seeing that live power usage on my desk all day long kept tempting me to try and optimise the baseline consumption just a tad more…

Previous readings have always hovered around 115 Watts, lately. Since the JeeLabs server + router + internet modem use about 30 W together, that leaves roughly 85 W unaccounted for. Note that this is without fridges, boilers, heat circulation pumps, gas heaters, or other intermittent consumers running. This baseline is what we end up consuming here no matter what – vampire power from devices in “standby” and other basic devices you want to keep running at all times, such as the phone and internet connection.

It’s not excessive, but hey: 100 W day-in-day-out is still over 850 kWh on a yearly basis.

Well, today I managed to get the baseline down waaay further:

DSC 4242

That’s including the JeeLabs server + router + modem. So the rest of the house at JeeLabs is consuming under 40 W. Perfect: I’ve reached my secret goal of a baseline under 50 W!

Here’s how that “idle” power consumption was reduced this far:

  • I turned off an old & forgotten laptop and Ethernet switch, upstairs – whoops!
  • I removed another gigabit Ethernet switch under my desk (more on that later)
  • the 10-year old Mac Mini + EyeTV + satellite dish setup has been dismantled and replaced by a small all-in-one TV drawing 0.5W in standby (the monitor is re-used)
  • I’m switching to DVB-C (i.e. coax-based) reception, available from the internet modem by upgrading to the cheapest triple-play subscription with “analog + digital” channels
  • that means: no settop box, just the internet modem (already on anyway) and a new low-end but modern Sharp 22″ TV / DVB-C / DVD-player / USB-recorder

As it turns out, the Mac Mini (about 10 years old) plus the master-slave AC mains switch controlling everything else were drawing some 20 W – day in day out. Bit silly, and far too much unnecessary technology strung together (though working, most of the time).

The other biggie: no more always-on Ethernet switches, just the WRT320N wireless router in front of the server, with a second wired gigabit connection to my desk. That’s two really fast connections where it matters, everything else uses perfectly-fine WiFi.

The main reason for having an Ethernet switch near my desk was to allow experimenting with JeeNode-based EtherCards, Raspberry Pi’s, and so on. But… 1) that switch was really in the wrong place, it would be far more convenient to have Ethernet in the electronics corner at JeeLabs, and 2) why keep that stuff on all the time, anyway?

So instead, I’m now re-using a spare Airport Express as wireless-to-wired Ethernet extension router. Plug it in, wait a minute for it to settle down, and voilá – instant wired Ethernet anywhere there is an AC mains socket:

DSC 4243

And if I need more connections, I can route everything through that spare Ethernet switch.

It’s not the smallest solution out there, but who cares. Why didn’t I think of all this before?

  1. How can you get a server running on so little power? I have a Linux server running on a core2 computer eating 40-60 watts. Actually, the server “shelf” hosts an AirPort Extreme, the server, a backup WD Wolrd disk array and the service provider DSL modem. All of this, on UPS, consumes 110 watts. Anyway, my baseline is 500-700 watts for the house and office. We burn over 100K watts here during winter, so a few extra watts doesn’t really matter. I calculated that 100 watts, 24 hours a day for a year will cost about $60 CAD. Lucky us… We pay 0.07$ per kilowatt…

    • The Mac Mini draws under 10 W idle (see this post), and hovers around 17 W in actual use (120 G SSD + 500 G 2.5″ HD internal, 2 TB 2.5″ USB HD) – add 5 W for the WRT320N router and 6 W for the fiber modem. No UPS.

      And that’s not even the lowest possible. Here’s an interesting low-power hacking project:

      Amazing cost difference, BTW: 0.07 CAD is 0.05 Euro. In the Netherlands, the price for 1 kWh is 0.21 .. 0.23 Euro (half is “energy tax”, and another 21% VAT).

      The economic incentives to save on energy (and gasoline) are clearly a lot higher in Europe than in North-America. But hey, the world is not only about money: looks like you may have lots of opportunities to reduce your consumption levels!

      Just out of curiosity: what’s your yearly kWh consumption?

    • Electricity use for the last 12 months: 21340 Kilo Watts. This includes all energy costs, since heating is electric, as is hot water. The daily consumption is about 61 Kilo Watts, down from about 80 when I bought the house 7 years ago. We bought new, energy efficient, windows, threw away the old oil furnace, installed more insulation and plugged a lot of small holes (many of which were mice tunnels…)(we live in an old school!). The rest of the economy came from being more efficient. There is still a lot to do on this front. For example, the baseline of 500-700 Watts includes ~250 Watts for computers alone, 24/7.

    • 21340kWh is not very much if heating is included!

      In fact, it is much less then we use in our house (3-5 people, 280m², ~5500kWh electricity and ~32000kWh equivalent natural gas for heating and hot water).

    • Jörg, what’s the conversion factor to use for m3 -> kWh?

    • m³ -> kWh

      roughly 10kWh per m³. Varies between 8 and 11. I always use 10, because this is easier for my old brain.

      the same factor works for 1l ‘heating’ oil.


      sorry Geert! I didn’t see your post until I sent mine….

  2. Despite the inclement weather and low energy prices, Canadian per capita consumption is only ~165% of the same measure in the Netherlands (rather stale 2003 data).

    Try some of the developing nations (Far East at ~20% per capita) Watch out when they can afford to buy and turn on the aircons!

  3. @jcw: according to this leaflet (found by some googling, no idea of the accuracy) it’s about 11 kHw/m^3, found on page 7.

    The website it’s on belongs to a (non-profit?) organisation “[whose] mission is to tackle climate change by accelerating the move to a vibrant low carbon economy that delivers jobs and wealth.” No proof for correctness of the numbers, but at least this conversion factor will likely not be skewed by business interests.

  4. @jbecker Our house is 180m² plus an unfinished basement that is heated to 15C. We are 2 adults so our hot water an lighting will be lower than yours, for sure! We have HUGE windows so during summer, lighting is minimum. We use standard (tungsten) bulbs for light in the winter to recuperate the extra heat (more efficient than CFL… in the winter). Our house is alone in a field/farm with trees in the back. Long wind-run from the front (no neighbour there for more than 1 km!)(vast empty field). We live near Montreal, Canada so our winters are … harsh, but definitely getting milder. Don’t you love global warming?(sic)

  5. @Robert, congratulations on “seeing the light”! Few have realised the fallacy of CFL “efficiency”, seemingly foisted on consumers by manufacturers’ lobby groups and now driven by official policy in many countries.

    True – CFL’s convert electrical power into light at much higher efficiency than incandescent bulbs. But when conversion “losses” are recuperated as space heating, that advantage fades away.

    But what about the CFL claimed 5yr, 10yr or even greater lifetimes? Surely that is saving the planet by reducing the number to manufacture?

    False, sadly. The glow tube can have a long life while internal blackening reduces light output until emitter coil failure. The problem is the drive electronics, often squeezed into an extended “cap” to try to match the incandescent bulb form factor. A designer’s nightmare – tight budget, limited space, subject to mains spikes and horribly hot.

    Typically, a direct on line, ‘constant current’ switcher is squeezed in there, with capacitive energy storage (~400VDC for European mains supplies). Even the best quality electrolytic struggles to survive a few thousand hours in these conditions.
    Cut corners with “cheap” imports and then the total system can barely survive a single year of typical use.

    Never mind, you were just following (misguided) Government policy – spend several Euro for a replacement (and don’t forget to go to the recycling center to scrap the old one properly, else another microgram dose of mercury joins the hundreds of thousands already in the landfill).

    Of course there are counter examples – special luminaire fittings that provide base cooling do better, some manufacturers are getting ‘more honest’ about ridiculous lifetime claims. But try to make a considered choice and selectively use incandescent where appropriate?

    Sorry Sir, it is against the law to sell those now (UK retail chain representative).

    Hmm… And BTW, who decided to stretch the millisecond ‘warm up’ time to long long seconds? Surely switching on is often to bring light to stop you stumbling in the dark? Soft turn on might be a nice marketing tweak, but please – allow me a choice!

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