Posted by Windsun on January 19, 2006, 2:18 pm
None of those setups make much sense to me, I guess I don't understand what
you are trying to do.
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>>If it is 150 feet away, why not just wire the panels up in series and use
>>an
>>MX60 charge controller - probably cheaper than the wire you would need at
>>12
>>volts.
> Comparing apples to apples, we might have...
> 1. $894 for 300' of 4/0 24 V wire
> $100 for 2 12 V in-house batteries
> ----
> $994, with about 24 Wh/day of wiring loss, or
> 2. $17.54 for 3 50' 16 ga 120 V outdoor extension cords
> $100 for an out-house 120 V or 240 V OK4U
> $100 for 2 12 V out-house batteries
> ----
> $217.54, with about 20 Wh/day of wiring loss, or
> 3. $17.54 for 3 50' 16 ga outdoor extension cords
> $100 for an in-house OK4U
> $495 for an MX-60
> $100 for 2 12 V in-house batteries
> ----
> $712.54, with about 4X the peak current and 320 Wh/day of wiring loss,
> or
> 4. ?
> I'm thinking the 2 out-house batteries (do they need a charge controller
> in this case?) would contribute as much to backup storage as 2 in-house
> batteries. With luck and more DOD, they might wear out under warranty and
> prolong the life of the in-house batteries :-)
> Nick
>
Posted by wmbjk on January 19, 2006, 3:12 pm
On 19 Jan 2006 12:59:15 -0500, nicksanspam@ece.villanova.edu wrote:
>
>>If it is 150 feet away, why not just wire the panels up in series and use an
>>MX60 charge controller - probably cheaper than the wire you would need at 12
>>volts.
>Comparing apples to apples, we might have...
>1. $894 for 300' of 4/0 24 V wire
> $100 for 2 12 V in-house batteries
> ----
> $994, with about 24 Wh/day of wiring loss, or
Do you really need to shoot for 1% loss? Or use welding wire? It seems
like a less flexible #2 should do at far lower cost.
>2. $17.54 for 3 50' 16 ga 120 V outdoor extension cords
> $100 for an out-house 120 V or 240 V OK4U
> $100 for 2 12 V out-house batteries
> ----
> $217.54, with about 20 Wh/day of wiring loss, or
The batteries are in parallel without MPPT, or any controller? Won't
that be a drag on array efficiency?
>3. $17.54 for 3 50' 16 ga outdoor extension cords
> $100 for an in-house OK4U
> $495 for an MX-60
> $100 for 2 12 V in-house batteries
> ----
> $712.54, with about 4X the peak current and 320 Wh/day of wiring loss, or
>4. ?
Similar to No.3, except everything located outdoors as in No.2?
>I'm thinking the 2 out-house batteries (do they need a charge controller
>in this case?) would contribute as much to backup storage as 2 in-house
>batteries.
Perhaps the whole thread didn't make it to my server. Which option has
two sets of batteries, and how is the indoor system connected?
Wayne
>With luck and more DOD, they might wear out under warranty and
>prolong the life of the in-house batteries :-)
>Nick
Posted by Eric Sears on January 19, 2006, 3:29 pm
On 19 Jan 2006 08:56:55 -0500, nicksanspam@ece.villanova.edu wrote:
>Someone just asked what kind of wire I'd use to connect 6 110 W panels
>(660 W at 24 V) to a house 150' away. Losing 1% of the power in each wire
>makes (660/24)^2r = 6.6 W, ie r = 0.00827 ohms per 150', ie 1000r/150
>= 0.058 ohms per 1000', ie 4/0 wire, almost 1/2" in diameter. Wow.
>The Windsun site says $298/100', ie $894 for wire.
>But if this is a grid-tied backup system, why not put 2 12 volt batteries
>and a low-power inverter in a box near the panels, with more batteries and
>a larger inverter in the house? If we make 0.8x660x4.6 = 2.4 kWh on an
>average day at a latitude tilt near Phila, that's only 100 watts over 24h,
>small enough for a Microsine or OK4U inverter with 3 of Home Depot's $5.84
>50' 16 ga outdoor extension cords and (100/120)^2x0.3x4.016 = 0.84 watts.
>Nick
This perennial problem of cable loss raises the prospect of some
innovative solutions, such as the one Nick suggests - I like it!
Of course, there are code requirements etc - but as long as things are
done safely, there isn't usually any problem.
I have often considered doing as Nick suggests. I know of a situation
where someone needs to run a wind turbine some 1000m from their house.
My intention had been to use a battery just as a buffer for the
generator, running a cheap inverter (230v) at close to the output of
the turbine (maybe 400 watts), and a homemade switching regulator that
would divert the excess. By using a reasonable time delay (so as not
to switch the inverter too often - perhaps 5 to 10 minutes), the
inverter would be turned on and off by the regulator (rather than left
running all the time), to send bursts of power to the house.
This keeps the battery mostly fully charged.
Of course, using Nick's scheme there would be less loss on the line,
but the risk of battery failure is increased (under warranty? grin).
>I'm thinking the 2 out-house batteries (do they need a charge controller
>in this case?) would contribute as much to backup storage as 2 in-house
>batteries. With luck and more DOD, they might wear out under warranty and
>prolong the life of the in-house batteries :-)
If we are considering overcharge - a controller is probably not
needed.
But flattening it completely too many times could drastically shorten
its life. Presumably if the inverter switches off at low volts (and
then auto switches on again!), then the low voltage cutout may be able
to be trimmed a bit higher.
When dc-dc converters get as cheap at MSQ inverters (unlikely!), there
will be lots of solutions !
Eric
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>>an
>>MX60 charge controller - probably cheaper than the wire you would need at
>>12
>>volts.
> Comparing apples to apples, we might have...
> 1. $894 for 300' of 4/0 24 V wire
> $100 for 2 12 V in-house batteries
> ----
> $994, with about 24 Wh/day of wiring loss, or
> 2. $17.54 for 3 50' 16 ga 120 V outdoor extension cords
> $100 for an out-house 120 V or 240 V OK4U
> $100 for 2 12 V out-house batteries
> ----
> $217.54, with about 20 Wh/day of wiring loss, or
> 3. $17.54 for 3 50' 16 ga outdoor extension cords
> $100 for an in-house OK4U
> $495 for an MX-60
> $100 for 2 12 V in-house batteries
> ----
> $712.54, with about 4X the peak current and 320 Wh/day of wiring loss,
> or
> 4. ?
> I'm thinking the 2 out-house batteries (do they need a charge controller
> in this case?) would contribute as much to backup storage as 2 in-house
> batteries. With luck and more DOD, they might wear out under warranty and
> prolong the life of the in-house batteries :-)
> Nick
>