ADSL modem as tiny dump load

[DamonHD]

Hi,

Puny on the scale of things usually discussed here, but I was frustrated with power from my off-grid system going to waste (and no 12V-input grid-tie inverter to dump excess to grid in the obvious way).

So I put in a little code to control one of the digital outputs of the k8055 USB board from my off-grid power SheevaPlug that shifts my ADSL Internet modem from mains to off-grid when the battery is very full.

It's only about 8W of load (with a very inefficient ~1W of relay drive when off-grid) but it looks like it's taking about 0.1kWh/day load from the mains, including the evening peak FWIW, and leaving the battery state fairly stable.

http://www.earth.org.uk/off-grid-stats.html

I only switch off-grid when the battery voltage hits 14V and stays high for more than an hour (to get a decent charge), and switches back to mains when battery voltage drops below 12.7V.

Rgds

Damon

[niall2]

hi Damon...

interesting that you mention a k8055 board , i have one almost put together but i,m not sure if i can use it the way i want ( or am vaguely familiar with )...it was a gift and its only now i see its a fairly clever board...

i can use picaxe code a little ( mainly with guidance from others )...can this board use a similar format to the picaxe platform ?...

or is it a totally different direction of programming ....

the board is nearly ready to play with ...

[DamonHD]

As far as I know you can't get at the k8055 PIC at all, it's just a USB peripheral, and I use the board from the command line using shell script:

http://earth.org.uk/Sheeva-files/20140509/local/k8055/check-status.sh

All buried in this line:

DATA="`$KBIN -port:0 -d:$outbitsValue 2>/dev/null`"

Rgds

Damon

[niall2]

thanks .....

i think i,ll leave it as is , i,m sure i,ll get a use for it ....it,s got 2 pwm outputs which seem interesting 

i,d like an option to tap ( or bleed ) a little windmill energy into a small solar water tank in the evenings, it might be suitable for this (and fun to play with).....

[DamonHD]

I just made my system switch to more conservative voltage thresholds (to keep more energy stored) unless tomorrow's forecast is "sunny":

http://www.earth.org.uk/note-on-SheevaPlug-setup.html#power-forecast

The clever bit is this line in my crontab:


47 6,11,21 * 2-10 * if [ "sunny" != "`wget -q -O - http://open.live.bbc.co.uk/weather/feeds/en/kt1/3dayforecast.rss | awk '/<title>.*emperature/ { if(++count==2) {if($0 ~ /[Ss]unny/){printf("sunny");}exit;} } '`" ] ; then rm -f /var/run/FORECAST_PV_GEN_GOOD.flag; else touch /var/run/FORECAST_PV_GEN_GOOD.flag; fi


and a small section in the power-monitor script that looks for that flag and adjusts thresholds accordingly.

Rgds

Damon

[Bruce S]

NICE coding! I like the way you accounted for the different spelling of sunny and temperature  .

[DamonHD]

This is not exactly going to rock the utility markets, but my ADSL dump load has been active (ie off-grid) about 2/3rds of the hours this month so far thus saving ~0.13kW/d or maybe 2--3% of our entire gross consumption, and generally into the evening grid demand peak.  My keeping 8W off the grid is not doing much against 32GW of peak demand, but hey-ho...  B^|>

4 days in a row off-grid for the ADSL modem is equivalent to skipping one (ECO) run of the dishwasher.

The live data file is here: http://www.earth.org.uk/data/k8055.flags/201406.log

When the 'VGOOD' flag is present then the ADSL modem is off-grid.

Rgds

Damon

[Bruce S]

DamonHD;
Look at it this way. How much would it be if everybody with an ADSL modem were to do the same thing  . How much non-grid use or a lower peak need there would be.
Cheers!

[DamonHD]

212MW approximately...  B^|>

Rgds

Damon

[DamonHD]

While I work to move things over, I am running my SheevaPlug and RPi in parallel.

And at the moment the RPi is on the 'dump load' supply.  It gets quietly (and without glitching, I hope) dropped back to mains when there isn't enough spare solar rather than getting turned off abruptly.

I'll start another thread about the RPi itself.

Rgds

Damon