cellular pv site project [RE-wrenches]

[Bob Maynard, Energy Outfitters]

Bob,

Telco equipment (wire based systems) have been and continue to be -48vdc
almost exclusively.  Cellular transmitter sites have been +24vdc (often
their industry calls it 28vdc) in every occasion I've run into (about 18
sites).  Couldn't agree more with your comments on how they "size" their
power needs!

Regards,
Bob Maynard
Energy Outfitters LTD
800-GO-SOLAR

-----Original Message-----
From: lizardlists [mailto:lizardlists at houston.rr.com]
Sent: Tuesday, March 25, 2003 7:45 PM
To: RE-wrenches at topica.com
Subject: Re: cellular pv site project [RE-wrenches]


telco stuff is -48V for as long as I can remember, and anyone else that I
know.  No idea where the 24V could have come from.

Most guys doing inside plant design where they colocate with someone else
(i.e.rent space) do their power caculations based
on breaker size,  sometimes the will add up all the theitotical maximam amp
draw for everything in a max worse case config and running at full capacity
and add 20% and use that for their power spec...  Needless to say, they ask
for more then they really will use.  the industry operates in paranoia that
some future upgrade or capacity expansion will cause them to have to take
some down time for a power upgrade.  To see someone use a clampon amp meter
and take some real mesurements is a rare event.

Power consumption and heat load compared to physical size are real issues,
more and more circuits operating and very fast speeds eats lots of power and
converts it to heat and noise.  Wireline telco gear sips power compared to
the newer and denser data, and wireless (cel) stuff.

bob.




----- Original Message -----
From: "Bob Maynard, Energy Outfitters" <bob at energyoutfitters.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, March 25, 2003 1:36 PM
Subject: RE: cellular pv site project [RE-wrenches]


> HI Keith,
>
> I designed and sold several mountaintop cell site systems here in the
> Northwest during the late 90's.  They were all negative ground 24vdc
> systems.  Most of their equipment was dc with an occasional small ac
device
> which we powered by an Exeltech inverter.  The load profiles are typically
> quite heavy, pretty surprising for electronic equipment!  Watch out for
> equipment room ventilating/cooling equipment.  They greatly appreciate
some
> lighting circuits for the equipment room(dc or ac didn't matter).  If
there
> is an inverter, they like a couple of receptacles to plug in test
equipment
> when they're at the site working.  We normally used simple contactors for
> charge control to assure we didn't generate any noise, although on the
last
> systems I used Trace C-40's with no adverse effects.  PV by itself could
not
> carry these systems by themselves in our climate.  We tried wind machines.
> They were a nightmare with the harsh mountain top conditions, icing, wind
> gusts, etc.  Virtually all ended up with engine generator backup, low
> voltage auto start and large rectifiers.  Most sites used industrial
> batteries, some wet, some sealed.  A few experimented with L-16's but to
get
> adequate amp/hour capacity required to many strings in parallel, leading
to
> problems.  Hope some of this is useful, feel free to contact me on or off
> list.
>
> Regards,
> Bob Maynard
> Energy Outfitters LTD
> 800-GO-SOLAR
>
> -----Original Message-----
> From: keith [mailto:kcronin at lava.net]
> Sent: Monday, March 24, 2003 10:23 PM
> To: RE-wrenches at topica.com
> Subject: cellular pv site project [RE-wrenches]
>
>
> Wrenches....
>
> Has anyone done any pv generation work for any of our cellular carriers?
> I got a call looking to do one.  I understand the 24 volt positive
> ground from the 1930's.  The one I am not sure about is the standard
> 120/240 volt 200 amp service that most of these are powered by, via the
> utility company.  I received a verbal 45 amp constant load as a
> preliminary number to shoot for.  I thought most phone/cellular
> equipment was dc in the first place? A 45 amp load is a giant pv load
> for a 24/7/365 application. I think the load can be a lot smaller
> without all of the inefficiencies with the ac-dc losses.
>
> Any experienced wrenches would like to comment?
>
> Keith Cronin
> Island Energy Solutions
> 318 A Kuulei Road
> Kailua, Hawaii 96734
> 808-262-3268 Tel
> 808-263-0338 Fax
> www.islandenergy.net
>
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