On 5/20/2012 4:37 PM, Harold Hallikainen wrote:
> I've not been following this thread closely, but the mention of throwing
> energy away when the battery is full just bothers me. the great thing
> about grid-tied solar is that the grid will take whatever you can
> generate. So, I assume solar powered battery charging is used only when
> grid tie is not practical (extremely remote locations or self-contained
> low power devices like highway emergency phones, solar powered
> calculators, etc.).
>
> Many years ago, I helped some students with a solar powered car. It used
> lead acid batteries. We did a form of maximum power point tracking by
> having each solar panel (there were lots) drive a boost converter where
> the duty cycle was controlled by a PIC. The PIC dithered the duty cycle
> while watching the output current to the battery, adjusting for maximum
> current out of that individual converter. Later, I read an LTC applicatio=
n
> note on MPPT that indicated that the MPP of a solar cell was close to the
> same point as a fixed voltage out of the cell. So, they just used a
> standard boost converter but tied the feedback to the input voltage
> instead of the output voltage. Very simple! I was impressed.
>
> With the very low price of solar cells right now, it seems practical to d=
o
> simple grid tied systems. I remember reading years ago about distributed
> inverters where the inverter is attached to the panel. You buy panels as
> you need (or can afford) them, and just plug them in. I think stuff like
> this is now available on the market. If you put a low power radio in each
> panel, you could also gather statistics on how each panel is doing. Each
> panel could transmit its current status on a random basis every few
> seconds or minutes. A central receiver would gather the data and summariz=
e
> it, probably on a web interface through wi-fi.
>
> I just pulled my most recent electric bill. The rates are:
>
> $0.12845 for first 154.7kWH
> $0.14602 for next 46.41kWH
> $0.29940 for next tier (up to about 300kWH)
>
> So, right now, a grid tied solar that produced 16kWH per month would save
> me about 30 cents per kWH. At 30 cents/kWH, it certainly seems practical.
>
> Now, if I could just convince my condo association to let me put somethin=
g
> on the roof...
>
> Harold
>
>
Moat of our clients pump into thew grid, but some, like those of rural=20
Sonora, MX operate with battery arrays. however, my intent was to=20
discuss simple battery matters, not storage methods.

I consider pumping into the grid a storage method.

--Bob A
--=20
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