Weath­er sta­tion read­out with FreeBSD

A while ago a wind tur­bine was installed not far away from my place. It is far enough to not dis­turb us, and it is near enough to notice that it turns a lot (IIRC I have seen it only once not turning).

This trig­gered a ques­tion. How much ener­gy would such a device (small­er of course) pro­duce at my place?

The answer depends upon sev­er­al fac­tors. The wind speed, the wind direc­tion and the wind-speed-to-power-output curve of the device. If you do not take a device which rotates around the hor­i­zon­tal axis but the ver­ti­cal axis, the wind direc­tion can be tak­en out of the ques­tion (prob­a­bly not com­plete­ly, but to answer my ques­tion this sim­pli­fi­ca­tion should be ok). The output-power curve depends upon the device, and I hope it is easy to get it from the ven­dors. The remain­ing open ques­tion it the wind speed at my place. Is there enough wind with enough speed?

To answer this ques­tion I bought a weath­er sta­tion with an anemome­ter (wind speed sen­sor). I searched a lit­tle bit until I decid­ed to buy a spe­cif­ic one (actu­al­ly I bought three of them, some cowork­ers got inter­est­ed too but they found only much more expen­sive ones, so soon there will be three more weath­er sta­tions in use in Bel­gium, France and Ger­many). The main point is, I can con­nect it to an USB port of a PC and there is some soft­ware for Lin­ux to read out the data. It also comes with some oth­er outdoor-sensors (tem­per­a­ture, rain, wind direc­tion, humid­i­ty, …) and an indoor-control-unit with some inter­nal sen­sors (tem­per­a­ture, humid­i­ty). The user inter­face is main­ly the touch­screen of the control-unit. There is also some Win­dows soft­ware, which is need­ed to pro­gram the inter­val in which the mea­sure­ments are tak­en and saved in the control-unit.

It seems the weath­er sta­tion is pro­duced by Fine Off­set Elec­tron­ics Co.,Ltd and sold with­in dif­fer­ent brands in dif­fer­ent loca­tions. The Lin­ux soft­ware can read all of them, as the ven­dor and prod­uct IDs are not changed.

Port­ing the soft­ware was easy, it uses libusb and I just had to cor­rect a lit­tle prob­lem for the non-portable func­tions which are used (I asked about them on usb@ and the response was that they just got imple­ment­ed upon my request and will be com­mit­ted to HEAD soon). I made a lit­tle patch for the soft­ware to only use them when avail­able (if you have not loaded the USB HID dri­ver, you do not need to care about them) and com­mit­ted it to the Ports Col­lec­tion as astro/fowsr.

Now I just need to attach the out­side sen­sors at the place where I would put the ver­ti­cal axis wind tur­bine, install some toolk­it which takes a series of mea­sure­ments and dis­plays them as a nice graph (while keep­ing all data val­ues) and write some glue code to feed the out­put of fowsr to it. After a year I can then cal­cu­late how much pow­er a giv­en wind tur­bine would have pro­duced dur­ing the year and cal­cu­late the return of invest­ment for it.

The Lin­ux soft­ware also ref­er­ences sev­er­al weath­er sites, for some of them you can get even an iGoogle wid­get so that you can view the data from wher­ev­er you want (as long as you have a suit­able inter­net con­nec­tion). I think this is also some­thing I will have a look at later.

Note to users in Europe, the device also comes with a DCF77 receiv­er. As the time is dis­trib­uted in UTC+1 (or +2, depend­ing on the day­light sav­ing time), you should adjust the time­zone set­ting accord­ing­ly to this, not to plain UTC (so for me the time­zone should be ‘0’ for the same timezone).