[ANSS-netops] ANSS-netops Digest, Vol 59, Issue 6
Greg Steiner
vlf at cablerocket.com
Wed Jan 7 18:40:18 UTC 2015
Patrick, I'm curious as to how you get multiple MPPT controllers to
charge a single battery bank. Are they inherently designed for this form
of parallel operation?
Greg Steiner
On 1/7/2015 11:16 AM, anss-netops-request at geohazards.usgs.gov wrote:
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> Today's Topics:
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> 1. Re: solar power problems (Patrick Bastien)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 7 Jan 2015 12:18:20 -0500
> From: Patrick Bastien <bastienp at ldeo.columbia.edu>
> To: <anss-netops at geohazards.usgs.gov>
> Subject: Re: [ANSS-netops] solar power problems
> Message-ID: <54AD6A5C.6080608 at ldeo.columbia.edu>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> The Concorde Sun Extender PVX-1040T has a nominal capacity of 104AH, so
> 312AH for the northern TA stations and 208AH for the southern TA stations.
>
> Beginning late last summer, the LCSN has begun to switch from older
> PWM-style charge controllers to MPPT charge controllers. Although it is
> too soon to say something definite, this is seeming to have a larger
> effect on station up-time than just adding more panels or batteries.
> Something I am doing that might be considered non-standard is wiring
> each solar panel individually to its own small MPPT change controller.
> This allows each solar panel to generate the maximum amount of power
> regardless of the lighting condition of the other solar panels. The
> several MPPT charge controllers then feed a common battery bank. I then
> regulate the voltage powering the sensor by using a small low-noise DCDC
> converter imbedded inside a cable. The MPPT benefits might be magnified
> for the LCSN because of the location of many of our solar powered
> stations are in forests or forest-adjacent.
>
>
> Patrick Bastien
> LDEO-LCSN
>
> On 1/7/2015 11:06 AM, Meremonte, Mark wrote:
>> Bob, May I ask the AH size of AGM batteries for an average TA
>> station? Thank you, Mark
>>
>> On Wed, Jan 7, 2015 at 8:29 AM, Robert Busby <busby at iris.edu
>> <mailto:busby at iris.edu>> wrote:
>>
>> Hi Mitch et al.
>> This is a good discussion of Power for seismic stations, thanks.
>>
>> In the Transportable Array deployment, all 1717 stations
>> operate(d) off solar power for at east two years. The average
>> current draw for a station is 0.5Amps on a 12V system, but can
>> vary from 0.4 to 0.6A depending on the telemetry system. High
>> current telemetry systems such as VSAT are powered separately. We
>> avoided AC power because of the proximity of noise due to pumps,
>> motors, etc.
>>
>> In general we use (2) 90W PV panels and (2) AGM Lead Acid
>> batteries for stations south of the Kentucky/Tennessee line (row U
>> in TA station codes) and (3) 90W PV panels and (3) AGM Lead Acid
>> batteris north of there. Shady or snowy sites occasionally got
>> more panels and batteries. For permanent stations I'd go with the
>> (3) PV and 3 or 4 batteries. We prefer good quality batteries
>> designed for solar applications, such as the Concorde Sun Extender
>> PVX-1040T. We use PWM regulators with Low voltage disconnect at
>> 10.8V. A few more sophisticated options are discussed below.
>>
>> I would concur with the notion that the most effective way to
>> improve a marginal station power situation is to add 1 or 2
>> batteries, and often this can be done without much infrastructure
>> alteration. And the next option is to add a panel. There is
>> little concern about over driving the charge controller with too
>> much current from too many panels. In Alaska, the "more
>> batteries" approach is taken to extremes in which stations have 24
>> batteries to float through the winter. I would also concur that,
>> to date, neither wind nor fuel cells have proved reliable enough
>> to warrant their use, especially in permanent stations of the Lower48.
>>
>> More complexity described below:
>> Our system has, in addition to the main battery bank, a small
>> reserve battery. When the system switches to the reserve, certain
>> loads such as the telemetry radio and local data storage are duty
>> cycled at four hour intervals. This reduces the power of the
>> station to about 3W, yet still provides complete telemetry (though
>> with episodic latency) and complete local storage. For us, this
>> reserve power serves to identify the source of the outage is
>> clearly power as opposed to a host of other possibilities. In the
>> original design this reserve battery was Alkaline Lattern 30AH
>> batteries [(3) x 6Volts] (a primary battery, disposed of after
>> use). More recently, We have also used 100-300AH rechargeable
>> batteries that are then connected to the main batteries using a
>> battery isolator circuit-which connects the reserve batteries to
>> the charger only when the main battery has recharged to 13.2V. We
>> add a 10A current limit to the battery interconnection. The
>> reserve power load shedding can be thought of as doubling the
>> capacity of the reserve batteries, reducing the cost of overall
>> power system for this reserve capability. Without that
>> sophisitication of load shedding, adding more batteries is
>> effective but there is a cost in terms of station uptime. When a
>> very large, undifferentiated battery bank is depleted, it will
>> take a longer time for the batteries to reach the reconnect
>> voltage. In this time, the station itself could be operating on
>> the minimal power produced. We keep the main battery bank fairly
>> modest so it recovers voltage quickly, and defer recharging the
>> reserve pack until there is ample power-sometimes weeks, or in
>> Alaska, months later. Its meant to get you through an ocasional
>> bad spell. One issue in this reserve battery switching is the dc
>> currents can introduce magnetic pulses seen on the
>> seismometer-particularly Trilliums within a few meters of the
>> switches.
>>
>> If you are plannning a Net-ops meeting in the future, I'd be
>> happly to elaborate on the power system for Alaska, which uses a
>> Genasun MPPT charge controller and LiFePO4 (Lithium Ion) batteries
>> and the same duty cycle loads, reserve battery concepts. These
>> significantly reduce the weight of a 1440AH system to 420 lbs and
>> do not require derating the capacity for cold temperatures. They
>> are very expensive, but not as much as a helicopter trip.
>>
>> Bob Busby
>> TA Manager
>>
>> On 1/6/2015 7:36 AM, Kyle Persefield wrote:
>>
>> Mitch,
>>
>> My 2 cents worth
>>
>> Because of cost, we have found throwing on more solar panels
>> to be the
>> cheapest and least maintenance intensive solution. Fuel cells and
>> thermoelectric generators are expensive and then there is the
>> recurring
>> cost for fuel, getting fuel to the site, then monitoring of
>> the fuel
>> supply level to consider, and the added required maintenance.
>> We have not
>> found a solution to use these devices as demand requires their
>> use. Or
>> turning them on and off as needed. So long as there is fuel
>> they are on.
>>
>> We have been very disappointed with wind turbines. The
>> smaller ones,
>> which are designed for the consumer market, the bearings
>> always fail.
>> Expect no more than 2 or3 years out of these "cheap" units.
>> Then of
>> course there is the need for wind. No wind for extended
>> periods is just
>> as bad as your overcast scenario.
>>
>> Kyle
>>
>> -----Original Message-----
>> From: ANSS-netops
>> [mailto:anss-netops-bounces at geohazards.usgs.gov
>> <mailto:anss-netops-bounces at geohazards.usgs.gov>] On
>> Behalf Of Mitchell M Withers (mwithers)
>> Sent: Monday, January 05, 2015 7:12 AM
>> To: Philip Crotwell
>> Cc: anss-netops at geohazards.usgs.gov
>> <mailto:anss-netops at geohazards.usgs.gov>
>> Subject: Re: [ANSS-netops] solar power problems
>>
>>
>> Here is a snippet from a recent report from a visit to an
>> example station
>> with a reftek, three S-13's, and an episensor. Stations vary
>> of course
>> and we do use low voltage cutouts at every station (fancy ones
>> that cut
>> out the transmitter first, then the DAS and everything else if
>> the voltage
>> continues to get lower).
>>
>> "The new battery banks, when installed were at 12.95 and
>> 12.98. The total
>> station draw is exactly 600ma (checked continuously for about
>> three
>> minutes). I did a quick calculation of 4 batteries at 96AH
>> each, 384/.6 =
>> 640/24 =26.6 days. This calculation would assume no solar
>> charge, but does
>> not take into account reduced battery capacity due to cold
>> temperatures."
>>
>> The panels at that particular station were supplying about
>> 700ma together
>> on an overcast day and are being replaced with bigger panels
>> this week.
>> Of course one solution is more battery and more solar at every
>> station
>> along with more frequent refreshing of batteries. But that
>> gets expensive
>> and time consuming so I was fishing to see if anyone is doing
>> something
>> creative. (e.g. wind or hamster wheels).
>>
>> Mitch
>>
>> Center for Earthquake Research and Information (CERI)
>> University of Memphis Ph: 901-678-4940
>> Memphis, TN 38152 Fax: 901-678-4734
>>
>>
>> ________________________________________
>> From: Philip Crotwell <crotwell at seis.sc.edu
>> <mailto:crotwell at seis.sc.edu>>
>> Sent: Monday, January 5, 2015 7:50 AM
>> To: Mitchell M Withers (mwithers)
>> Cc: anss-netops at geohazards.usgs.gov
>> <mailto:anss-netops at geohazards.usgs.gov>
>> Subject: Re: [ANSS-netops] solar power problems
>>
>> Hi
>>
>> How did you come up with your 25 day figure? Can you put some
>> numbers on
>> power input and output?
>>
>> We use two 105 amp-hour batteries per station, where the load
>> is about
>> 1/2 an amp. That gives me about 17.5 days theoretically, but my
>> understanding is that you never want to discharge batteries
>> anywhere near
>> their rating as they can be damaged by high discharges. So
>> maybe worry
>> less about age and more about installed capacity, ie double
>> the battery
>> and replace them half as often.
>>
>> We also, because of the cell modems, can monitor the battery
>> voltage over
>> time, we have a cron job to ping the cell modem once an hour
>> and ask it
>> what the input voltage is. For example here is the last few
>> days at one
>> station. You can definitely tell the difference between sunny
>> days and
>> rain, and we get a heads up if the power is getting low and can do
>> something before the station goes down.
>> http://eeyore.seis.sc.edu/earthworm/status/HAW_last720.png
>>
>> Here is another station that we are becoming worried about,
>> looks like I
>> might get to go on a road trip soon!
>> http://eeyore.seis.sc.edu/earthworm/status/CASEE_last720.png
>>
>> Philip
>>
>> On Sun, Jan 4, 2015 at 9:07 AM, Mitchell M Withers (mwithers)
>> <mwithers at memphis.edu <mailto:mwithers at memphis.edu>> wrote:
>>
>> Many of our stations run on battery and solar and that
>> normally works
>>
>> well. We have a routine battery replacement cycle to make
>> sure they don't
>> get old. Theoretically, we should be able to run with zero
>> solar for
>> about 25 days. But this has been an unusually dreary winter
>> in the
>> southeast and we haven't had much sun for the past two months
>> or more.
>> I'm wondering what others do in areas with limited sunlight to
>> power
>> stations that don't have AC available?
>>
>> Mitch
>>
>> Center for Earthquake Research and Information (CERI)
>> University of Memphis Ph: 901-678-4940
>> Memphis, TN 38152 Fax: 901-678-4734
>>
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>>
>> --
>>
>> ============================================================
>>
>> Robert W. Busby
>> Transportable Array Manager 508-801-7628
>> USArray / EarthScope 37 Haynes Avenue
>> www.earthscope.org/usarray <http://www.earthscope.org/usarray>
>> Falmouth MA USA 02540-2312
>>
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>>
>>
>> --
>> *********************************************************
>> Mark Meremonte Geophysicist
>> U.S. Bureau of Reclamation: Seismotectonics & Geophysics Group
>> Denver Federal Center Work: 303-445-3298 Cell: 303-808-3894
>> POBox 25007, 85-833000Email: mmeremonte at usbr.gov
>> <mailto:mmeremonte at usbr.gov>
>> Denver, CO 80225 Web: http://www.usbr.gov
>> Ship: U.S. Bureau of Reclamation, DFC, Bldg. 67-10th Floor, Denver, CO
>> 80225
>> **********************************************************
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