[ANSS-netops] solar power problems
Meremonte, Mark
mmeremonte at usbr.gov
Wed Jan 7 16:06:00 UTC 2015
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> 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] 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
>> 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>
>> Sent: Monday, January 5, 2015 7:50 AM
>> To: Mitchell M Withers (mwithers)
>> Cc: 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> 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
>>>
>>> _______________________________________________
>>> ANSS-netops mailing list
>>> ANSS-netops at geohazards.usgs.gov
>>> https://geohazards.usgs.gov/mailman/listinfo/anss-netops
>>>
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>>
> --
>
> ============================================================
>
> Robert W. Busby
> Transportable Array Manager 508-801-7628
> USArray / EarthScope 37 Haynes Avenue
> www.earthscope.org/usarray Falmouth MA USA 02540-2312
>
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--
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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, 85-833000 Email: 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
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