Gridtek 10 islanding with outback? [RE-wrenches]

[David Katz]

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Geoff,
There is a problem with load shifting with batteries. The batteries will 
cost $0.15 to $0.25 per kilowatt hour if they are well taken care of and 
more if they are ruined early, so he cannot win. If the customer goes 
with a low cost battery like a Trojan L16, each battery can discharge 
about 1 kwh per day if cycled to half discharge. At that rate they would 
be good for 5 years maximum, which is 1825 kilowatt hours per battery. 
$200 / 1825 = $.11 / kwh. You will also lose 10% in the batteries and 
20% in the inverter. $.11/.7 = $0.16 per kwh. He would be better off 
with the 1.5 cents per kwh from the wind and no batteries.
Cheers
David
David Katz
President, AEE Solar
formerly Alternative Energy Engineering
1155 Redway Drive - Box 339
Redway, CA 95560 USA
(707) 825-1200
(707) 825-1202
email: david at aeesolar.com
web: www.aeesolar.com


Geoff Greenfield wrote:

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>
>Thanks for the reply - also (obviously) I could approach this with an SMA
>sunny island (right? lords of the red box?)
>
>Further conversations with the customer have shed more light on the
>situation. Instead of (as I assumed) being motivated by the value of having
>stand by power during outages and a desire to max efficiency/production
>during normal operation, the request for batteries is based on something
>else entirely.  The rural co-op has let him go pure bi-directional net meter
>for 3 years due to lack of policy and luck... they have now installed
>computerized meters and sell him power at 10.6 cents and purchase it at 1.5
>cents.  On average, his wind offsets 60% of his use.  he wants to "load
>shift" (?) with a batt-verter system set up to power most of his 120 loads
>from the batts and charge from the grid/wind AC...  needing some sort of
>control to charge when the wind is exceeding household use, and obviously to
>maintain the batts at some minimum should the wind hit the doldrums...
>
>A design challenge for sure!
>
>
>For a brighter energy future,
>
>Geoff Greenfield
>NABCEP Certified Energy Practitioner
>
>THIRD SUN SOLAR & WIND POWER Ltd.
>340 West State Street
>Athens, OH 45701
>
>www.third-sun.com
>(740) 597-3111
>------------------------------
>
>  
>

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