[ANSS-netops] solar power problems
Philip Crotwell
crotwell at seis.sc.edu
Wed Jan 7 17:32:48 UTC 2015
We use the same batteries. But get the PVX-1040HT if you can as they
have a (H)andle. Very useful! :)
Philip
On Wed, Jan 7, 2015 at 12:18 PM, Patrick Bastien
<bastienp at ldeo.columbia.edu> wrote:
> 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> 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
>>>>
>>>> _______________________________________________
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>>>> 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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>
>
>
>
> --
> *********************************************************
> 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
> 80225
> **********************************************************
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