Tag for solar farm with dynamic panel orientation

While cycling around and pouring over aerial imagery I’ve come over time across a half dozen solar farms, to include one under construction where the solar panel groups are mounted on a heavy pole/mast w/ an electric engine which aligns the panels every so many minutes to the sun, actually somewhat ahead so as to get maximum output all daylight hours for each repositioning time frame. Each assembly had 54 panels and the on-site engineer told the benefit far outstripped the cost of maintenance.

Image sample in wiki, 1st page, 2/3rd down at left, though not clear if this is an installation with movement. “only” 27 panels on these.


The question: Is there a ready tag value specific to solar or in general to express the dynamic direction of these panels? TagInfo shows 292 pages with direction to include E;W and the wiki, but for the image, does not give a particular hint. Positioning is calendar adjusted.


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These are called heliostats, but mapping of them is all over the place, and I think power=heliostat is an extremely poor tag as it can confuse mirrors for solar furnaces with PV panels. Some people have mapped them as areas not realising that a few minutes after the aerial image their orientation will be different. The actual range of orientation will depend on available daylight anyway, and can be calculated from lat/lon and altitude (if you want to be fancy you can include some line-of-sight over nearby terrain too). I therefore think the mapping of these should:

  • Use nodes only, or if you must use an area orient the area to the South (as here at Almaraz)
  • Not use a direction tag. It can be calculated, but somewhat tediously for someone mapping them).
  • Map these as power=generator with appropriate power:method etc
  • Map the heliostat as a distinct feature (I think I’ve used location=heliostat), as a hint to consumers why there’s no direction tag, and as a hint to editors not to map them in an arbitrary position.

The Almaraz ones have a tag solar:tracking=dual, but I don’t know what that means (two axes?).

Note the Almaraz one (similar to in your example) allows grazing of livestock under the panels, so avoid landuse=industry.

PS. I suppose there is scope for a direction tag something like direction=heliostatic.

orientation=heliostatic would have my vote but would not object to direction=heliostatic.

Only seen the panels being vertically fixed mounted, horizontal-vertical axes gets really really fancy. Taginfo gives 2K for =dual and 93 for 2-axis suspecting they’re one and the same. Guess the 2K could be easily generated from a few large farms. The once I’ve seen are just in the 50-100 range and much smaller, farmers with a few in the yard. Those I’ve mapped individually as generator rather than solar farm.

The dynamic on some I’ve confirmed from 2 different aerials at different times of day, position and shade distinctly different.

NOT into mapping individual assemblies as the sample your linked to Almaraz, but the generator:solar:modules equivalent of panel rows, mast mounted assemblies would get me to add those tags.

Anyway, think if there’s some form of consensus it would be useful to add wiki language and guide forward on tagging.

Originally both generator:orientation and generator:place were in use with solar panels, but once I realised (seeing someone else’s work) that iD showed direction and that the other tags did not do anything over-and-above direction we moved wholesale to it. It has the advantage of being widely used, supported in one editor (great for QA as one edits) and simplifying tag usage.

The same process worked with location. I suspect there are quite a few other power-related tags which are unnecessarily or inappropriately “namespaced”.

If you’re in the Northern Hemisphere! :grinning:

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Officiously put in use, coined by the US Department of Energy

Well just like the South-pointing Chariot, the notion still works!