solar/wind tower grounding

[Radek Jager]

Hello everybody,
my name's Radek, and i usually spend winters in the philippines on a small island, where we're currently improving on our solar system; until now we've been using panels and automotive batteries separately on most bungalows, which is not very efficient and lot of maintenance. the new system (1800Wp) is centralised and runs off a 48V battery bank.
because the vegetation is dense, we're now building a tower; the PV panels will be 9m over ground, with only short periods of shade right after/before sunrise - sunset. in a 2nd stage it will be extended to approx 16m for a wind-genny.
my biggest headache now is how to ground the tower. i've read a lot of stuff; it seems that the wetter the soil, the better. now our soil here is very sandy and usually dry, a poor conductor. but, there is a 10m deep well (brackish water) about 30m away. could i sink a copper (or other) plate there and run a copper wire to the tower structure -it's standing on 4 galvanized iron legs- would that make for worse or better grounding then ground rings & rods? i have a range of info starting from my dad (el.ing. who also did the grounding on a nuclear power plant) to the local cell.tower builders on the other end of the simplicity scale. now i have to strike a compromise and just wondered if this well may be of any use.

thanx and regards to all,
RJ

[Rob Beckers]

Hi Radek,

Welcome to the forum!
Take a look at "Ufer" grounding: This was developed by an engineer in the US army in the 2nd WW, specifically for sandy soils, where they needed to ground ammunitions bunkers.

It uses concrete in a narrow trench, and rebar that is welded together in the concrete. The large porous surface of the concrete, and the salts it contains, make it conduct very effectively to its surroundings. The rebar serves to distribute the current in the concrete, and a piece that sticks out is then your conductor to ground everything to.

In many countries Ufer grounds are an excepted way of grounding, and electrical code often describes how they need to be constructed.

Hope this helps!

-RoB-

[Radek Jager]

hello Rob,
yes, i've heard about the 'ufer'. but what about the water-well? isn't salty water a good conductor and the surrounding ground pretty wet?

[Rob Beckers]

Sure, well casings are great for grounding (if they are metal all the way down to where the soil is wet enough to matter). You mentioned it's 30m / 100 feet away though. I'm assuming you have a good chance of direct hits in the climate you live in, for a tower the size you're constructing. Lightning won't 'nicely' make a 90-degree turn, to conduct along a wire, to a well that's 30 meters away. You need something right at the foot of that tower, and assuming you have cast concrete foundations for the tower anyway you could very easily turn those into Ufer grounds. If you want to run a line (bare copper, underground) to the well that's fine, it'll help, it won't replace a good local ground for the tower though.

-RoB-

[Radek Jager]

hi Rob,
ok, thanks - i meant to cast 4 independent 'boots' of cement/rebar at the bottom of every pipe (1m underground), so instead i'll connect all 4 with a beam cage and make sure there's good electrical connectivity between the rebar and the pipe? although this 'cage' is horizontal but the towerleg vertical (also 90-degrees), this doesn't matter?
or: i also planned to sit a pointed copper rod at the top of tower - better to connect it directly to rebar with wire isolated from the tower or connect the rod to tower and tower to rebar as described above?

regards,
RJ

[David MPierce]

Sure, well casings are great for grounding (if they are metal all the way down to where the soil is wet enough to matter). You mentioned it's 30m / 100 feet away though. I'm assuming you have a good chance of direct hits in the climate you live in, for a tower the size you're constructing. Lightning won't 'nicely' make a 90-degree turn, to conduct along a wire, to a well that's 30 meters away. You need something right at the foot of that tower, and assuming you have cast concrete foundations for the tower anyway you could very easily turn those into Ufer grounds. If you want to run a line (bare copper, underground) to the well that's fine, it'll help, it won't replace a good local ground for the tower though.

-RoB-
Well thanks to utmost solution Rob
:clap2:

[Jerry Smith]

Well that goes very well thanks for update :amuse: