Computing stuff tied to the physical world

Electricity consumption

In Hardware on Apr 8, 2012 at 00:01

Came across this graphic a while ago – US energy cost and consumption over the years:

Screen Shot 2012 03 27 at 18 44 08

For comparison, in 2012, electricity here costs ≈ €0.21 (i.e. $0.28) per kWh, including taxes.

Our usage (i.e. Liesbeth’s and mine) was about 3000 kWh in 2011. That includes electric cooking, but note that heating and warm water is provided through natural gas.

That puts us in the late 1950’s w.r.t. US electricity consumption levels – yo, Elvis! :)

I’ve started to get involved in a local initiative (see this Dutch website if you’re interested – “duurzaamheid” is all the rage these days, it seems), with all sorts of simple and not-so-simple ways planned 1) to consume less, 2) to switch to renewable sources, and 3) to fall back to natural resources for the rest. It’s not an all or nothing game, more a way to plot a practical trajectory for improving things over the next couple of years.

Here’s the JeeLabs neighborhood:


Lots of space to catch some sunlight on all those rooftops – but careful with that chimney’s shadow!

Now that solar energy has become so cheap (Wp prices including inverter have dropped below €1.70), we’re finally getting together with a couple of neighbors here to actually make it happen. This year, and hopefully before the summer is gone again!

The aim is to try and get 4000 to 5000 Wp onto our roof (16..21 panels of 100×160 cm), which would cover for our entire yearly electricity needs, even without pushing for further savings. For the 52°N latitude of the Netherlands, panel + inverter efficiencies are estimated in the 80..85% range, nowadays.

That’s just half the story, gas consumption is the other biggie – but hey, ya gotta’ start somewhere, eh?

  1. Glad to see you do the solar jump :) I used to work at Wagner und Co Solartechnik in Germany, planning grid connected PV systems. Don’t hesitate to ask for help/infos regarding the quotes u’ll get. Regards from Berlin

  2. I’m also so glad for 2 reason

    1. having a PV system it’ a great think

    2. when you’ll finish, you’ll must make some jeemonitor for this :-)


  3. With a challenging roof like that (shadow on only one cell can bring a string down) I wonder what your thoughts are on converters? How many JeeNodes will you need to monitor those???

  4. The angle of the roof isnt as critical as you might think – our local uni here has strings of panels mounted vertically as a wall in a test bed and is still getting 70-80% of peak efficiency.

    You might want to look at – good example of web connected remote monitoring (sound familiar?) and also some good real world figures of expected outputs based on weather / location.

  5. Be careful with interpreting reported PV output figures and what one might expect. Reported figures typically are MAX under best conditions and achievable for only small number of hours a day. Facing direction of the wall and sloped roof is significant. For example, non-south facing vertical walls are less than best conditions.

    Remember that the amount of sunlight hitting fixed PV panels goes as the cosine of the angle between (perpendicular) normal vector and the incident suns rays. As the earth rotates through out the day, the incident angle varies for a fixed installation and output varies. There is also the effect of light path through the earth’s atmosphere, attenuating the actual amount of light hitting the PV.

  6. Here in Italy a firm produces “hybrid” panels (both PV and hot water). So, using nearly the same space you can reduce the use of gas, too…

  7. An interesting and simple idea for measuring the output of your panels, is using PlugWise plugs. These are enery monitoring plugs in a ZigBee network, but can also (supposedly) measure the energy production of solar panels.

    Got the idea from a belgium forum here (sorry, dutch only):

    As I do not have solar panels myself (yet :-)), I can’t confirm that it really works. But I found the idea to be interesting, so I thought I’d share :-)…

  8. I’ve been looking at PV panels since I’ve started thinking about my new house. Now that the house is built (and I’m living in it), still no PV panels… it’s simply too expensive. But I will do it, one day.

    My house uses 6 hot water solar panels (plus a 1000 liter accumulator tank) for heating the house and domestic hot water. The backup system for the 3-4 months of cold winter is a wood-based solid fuel boiler. That makes my house very ecologic, since we have plenty of sun and firewood locally. Not a drop of fossil fuels in sight on my house! :)

    That takes care of the heating issue, but I’m still spending electricity from the grid.

    To be mostly independent from the grid in terms of electricity, requires a battery bank of some sort to store the energy and spend it later. Batteries are expensive and have a very limited life (replacing the battery bank every 3 years is not funny, nor cheap). How exactly are you solving that problem?

    • Here, you get the same price for electricity sent to the grid as for electricity taken from the grid. So everybody uses inverters tied directly into their AC mains. The grid is – so to speak – the battery. You send the surplus out in summer, and get it back in winter.

  9. There is a similar mechanism here, but it’s very complicated to “participate” (the government has very limited quotas).

    But if everybody is generating excess energy to the grid in the Summer, and everybody has additional needs in Winter, how does the grid itself manage this time offset?

    I understand that is not a problem for today (the majority of consumers do not generate energy), but were are actually shifting the problem to the grid. Are we not? :)

    • This is actually becoming a problem in the US as additional solar farms come on the grid. It is not an issue summer to winter as the load profiles for electric follow the temperatures. It is more of an issue from one day to the next and even hourly. There has been several studies and many ideas tossed around as to what to do. This has more to do with infrastucture and load paths on high tension lines between distribution zones. There are even companies that monitor solar radiation and report it every 15 minutes to help the distribution companies plan for loads. For longer term storage, pumped hydro which is pumping water to back behind a dam during peak sun periods to use during the night or on cloudy days for power generation. This also works for wind power.

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