What to do with the weath­er data?

As can be read in the pre­vi­ous blog post­ing, I have now some weath­er data around. Here the head­er from the CSV file I gen­er­ate out of the XML file of the soft­ware:

Date;Humidity (room);Temp (room);Humidity (out);Temp (out);Pressure (abs);Wind (ave);Wind (gust);Wind (dir);Rain

Cur­rent­ly I pro­grammed the weath­er sta­tion to save the data every 5 min­utes. The long-term goal is to decide if a giv­en wind tur­bine deliv­ers a sane amount of ener­gy (dur­ing a com­plete year) at a giv­en place. As I do not want to wait that long to get some infor­ma­tion out of this, the ques­tion aris­es, what I can do with this weath­er data?

Here an exam­ple of the out­put (ignore the rain and wind val­ues, the sen­sors are not attached at a place where there is wind or rain, the com­plete set is hor­i­zon­tal­ly on the floor instead of ver­ti­cal­ly how they are sup­posed to be; and do not be shocked about the room  val­ues, it is the “serv­er room” in the base­ment):

2010-09-02 12:55:01;52.0;18.700;30.0;27.000;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:50:01;53.0;18.700;30.0;27.500;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:45:01;53.0;18.600;30.0;27.300;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:40:01;53.0;18.600;30.0;27.800;978.600;0.0;0.0;135.0;4.200
2010-09-02 12:35:01;53.0;18.600;30.0;27.700;978.500;0.0;0.0;135.0;4.200
2010-09-02 12:30:01;54.0;18.500;31.0;27.500;978.700;0.0;0.0;135.0;4.200

Some things I came up with myself:

  • A line-graph of the val­ues dur­ing a day/week/month.
  • A graph of the amount of accu­mu­lat­ed rain per hour/day/week/month/year.
  • The aver­age temperature/humidity (as an error bar, so see the min/max too) per day and night, but what to use as the times where the day starts/ends? I would like to have the day-part cov­er the real day­light time (minus some ramp-up and ramp-down time), but I do not have any idea how to get this for each day and for my region.Does it make sense to do the same per hour (with­out any ramp-up/-down)?
  • Does the com­bi­na­tion of tem­per­a­ture and humid­i­ty and maybe wind tell some­thing? If yes, how to com­bine them and how to inter­pret the result?
  • Sim­i­lar for the pres­sure. I do not know what it tells me, but in a graph I can maybe add some hor­i­zon­tal lines which tell some­thing (rain prob­a­bil­i­ty and maybe dan­ger zones?).
  • For the wind speed the instruc­tion man­u­al comes with a nice table of the beau­fort scale and a cor­re­spond­ing descrip­tion. This can be put into some col­ored hor­i­zon­tal lines which show more or less dan­ger­ous speeds.

For the plot­ting of the data, I intend to use gnu­plot with the CSV data as the input. It should allow me to auto­mate a lot of things, and some of the graphs should also be easy to real­ize inside gnu­plot itself with­out any exter­nal pro­cess­ing, the ques­tion is only how to real­ize it. For exam­ple for the aver­age of some val­ues I do not know if it makes sense to use some­thing else than the arith­metic mean.

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No good heat reser­voir avail­able?

I was search­ing for a good heat reser­voir. Unfor­tu­nate­ly it seems that all on the marked are far from state of the art (they are prob­a­bly in their class, but see below).

Most of the devices use water to store the ener­gy. I found one (in Europe/Germany) which is using phase change tech­nol­o­gy instead of water to store more heat in the same stor­age place (but you need to ask how much it costs and how long they need to deliv­er, which prob­a­bly means that it is a lot more expen­sive (part­ly due to lim­it­ed amount of pro­duc­tion quan­ti­ty) than water based heat reser­voirs). I have read a lot about phase change mate­ri­als (PCM), and it seems there are dif­fer­ent kinds of sil­i­ca or wax (or oth­er mate­ri­als) which are bet­ter suit­ed to store heat ener­gy, but the only mass-market tech­nol­o­gy seems to be water based ones.

This looks strange to me. When I look at his­to­ry, oth­er mate­ri­als than water where already used a lot in the past (e.g. stones where heat­ed and then they were used in a press­ing iron or as some­thing which is replaced now by a hot-water bot­tle or an elec­tri­cal heat­ing cush­ion in the bed; yes, all this does not involve a change in the phys­i­cal state of the mate­r­i­al, but the point is that oth­er mate­ri­als than water where already used in the past), so I do not under­stand what is pre­vent­ing to let PCM based heat reser­voirs going main­stream.

Except for choos­ing the right PCM and obtain­ing it, it does not look hard to build such a heat reser­voir. You can add a heat-exchanger in the bot­tom and feed solar-power there for long-term heat­ing the PCM, anoth­er heat-exchanger at the top to heat the use-water and/or heating-water from the heat stored in the PCM, and a 3rd heat-exchanger (placed at the top too) which you con­nect to your central-heating if you need a lit­tle bit of quick short-term heat­ing of the PCM. I do not know if you need to add some  heat-layers (e.g. by putting a big cheat of a non-PCM mate­r­i­al between the long-term heat­ing part and the short-term heat­ing part), but  it should be easy to test if some­thing like this is ben­e­fi­cial or not. If you have a fire­place which you want to con­nect to the long-term heat­ing of the PCM, it may also be ben­e­fi­cial to have a 4th heat-exchanger togeth­er with the solar-one, but maybe there is anoth­er solu­tion to do this with the 3‑heat-exchangers-setup (I have not inves­ti­gat­ed this pos­si­bil­i­ty at all).

If some­one knows some inter­est­ing prod­ucts in Europe or has some help­ful infor­ma­tion (any­thing which can be inte­grat­ed into exist­ing heat­ing sys­tems with­out much ren­o­va­tion of a lot of rooms), please write a com­ment.

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Ideas page updat­ed

I updat­ed my ideas page. I added an entry about using com­pressed air to auto­mat­i­cal­ly remove snow (or sim­i­lar) from solar cells, and an entry about maybe using heat from ther­mal solar cells to gen­er­ate elec­tric­i­ty at home. I also updat­ed the entry for non-optimal weath­er opti­mized solar cells with a link to a com­pa­ny which seems to do some­thing sim­i­lar (using a lens) to reduce the cost of solar pan­els. To cool down the pho­to­volta­ic cells, the com­pa­ny is using a heat exchang­er to make a com­bined photovoltaic/thermal pan­el. Unfor­tu­nate­ly they are mak­ing an unfair com­par­i­son of the com­bined out­put of this pan­el (the ther­mal pow­er out­put is much high­er than the elec­tric pow­er out­put) with a nor­mal pho­to­volta­ic cell. A nor­mal house­hold needs more elec­tric­i­ty than heat so you do not want to use a lot of such pan­els, but depend­ing on the fea­si­bil­i­ty of my idea about using heat to pro­duce elec­tric­i­ty, such a pan­el could be inter­est­ing.

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The local BBQ style: “Schwenken”

When­ev­er I show our local (= my region) BBQ gear to “out­siders” (all peo­ple which did not grow up in our region and nev­er went to a local BBQ), peo­ple are impressed. So I thought, let me export this great inven­tion out in the world. Maybe some­one out there is inter­est­ed enough to build the sim­ple solu­tion which has a lot of fea­tures.

The Schwenker

As a pic­ture tells more than a lot of words, let me first let you look at it.

The typical BBQ device in my region.

The BBQ device which I show you here is called a “Schwenker”. The oper­a­tion of grilling some­thing on a Schwenker is called “schwenken” (the direct trans­la­tion of schwenken is “swing­ing around” or “to swing”). As you may guess, this is because you swing around the meat (or veg­eta­bles or fish or cake (I have read that one win­ner of the nation­al BBQ-competition had a Black-Forrest-Cherry-cake on the grill) or what­ev­er peo­ple may want to put there) over the fire. The meat which is very often pre­pared on the Schwenker is called “Schwenker” (we are effi­cient with words in our region…). Basi­cal­ly this is the meat of a pork which relaxed a day or two in oil, onions and papri­ka (add pep­per, salt and herbs to your own lik­ing, oth­er vari­a­tions are with gar­lic and green herbs). While the Schwenker is on the Schwenker, you can put a lit­tle bit of beer on it to add a lit­tle bit of taste (this is option­al). It exists a small Wikipedia entry about Schwenker, there you can even read about oth­er mean­ings of the words Schwenker/Schwenken (all relat­ed to what you see/read here).


So, how to build one? Its easy. Take a met­al plate (best is a tri­an­gle where the edges are bend a lit­tle bit), attach 3 met­al poles (they need to be strong enough to car­ry the grill and the meat) to it in a way that you can attach a met­al roll between them (like a hoist, it is there to lift the grill) and that the met­al poles form a tri­pod. You get bonus points if the roll can be rotat­ed where it is attached, but is is enough if it is aligned with one of the poles. Now take a grill (round) and attach 3 lit­tle chains to it (in the pic­ture above, those chains are not so lit­tle, but it is a big grill, you can feed at least 10 peo­ple at once) so that the grill is lev­eled when you attach those 3 chains to a sin­gle point. The 3 chains need to be attached to a long chain, and this chain needs to put on the roll which is attached on the tri­pod. Now attach a hook on one of poles in a con­ve­nient posi­tion (if you stand in front of the tri­pod you need to be able to access the hook eas­i­ly) and attach the chain which is con­nect­ed to the grill and the roll. It looks a lit­tle bit more high-tech if you use a winch instead of a hook, but then you need to use a met­al rope instead of a chain.


  • vari­able heat inten­si­ty (lift or low­er the grill by attach­ing a dif­fer­ent part of the chain to the hook)
  • ecologic/equal heat­ing (swing and/or rotate the grill over the fire, you can cov­er a lot of grill area with a small fire, all meat gets about the same heat­ing with­out the need to move the meat itself on the grill a lot)
  • keep some meat hot while eat­ing (lift or low­er the grill)
  • food safe­ty (you need to cre­ate more fire but you already have some meat on the grill: move the tri­pod to the side; you want to move the fire in the fire­place: the chain is not as hot as the grill, use it to move the grill a lit­tle bit to the side while mov­ing the fire in the fire­place)

Tips & Tricks

The fire­place in the pic­ture is a part of the bar­rel of a wash­ing machine (some­where between a half and a third of a bar­rel). I got mine for free from a local white-ware shop (from a bro­ken wash­ing machine, off course).

If you cre­ate the grill your­self, take care that a sausage can not fall through. The met­al needs to be of high qual­i­ty, ide­al­ly stain­less steel. Make a lit­tle bor­der around the grill, this way you can pre­vent acci­dents where a sausage lands in the fire or on the floor.

Instead of 3 met­al poles you can use 6. Attach 2 togeth­er in a way that they do not sep­a­rate if you lift the tri­pod, but allows to sep­a­rate them if need­ed (this allows to take the tri­pod with you). In the Schwenker in the above pic­ture the met­al poles are con­nect­ed with screws to the met­al tri­an­gle, I did not use any tools to attach it hard, I attached the screws by hand. This allows me to detach every­thing with­out any tools. Each of the 3 met­al poles con­sists of 2 small ones. They are con­nect­ed by tap­ping a thread into one, and attach­ing a tube with a cor­re­spond­ing thread to the oth­er one.

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