[aprssig] Shack backup power

Bob Bruninga bruninga at usna.edu
Sat Jun 4 16:58:39 EDT 2011

>> ...With these small plug-in grid-tie inverters 
>> in the 250 Watt class, now it is possible to run our shack:
> Do you have a reference for these plug-in grid-tie
> inverters?  I can not possibly see how these would 
> be legal but I want to see the manufacturer's 
> website if they exist.

The Enphase or is it Emphase micro grid-tie inverters are designed for installation right on the back of each solar panel and put out 240 VAC to be paralleled with all other panels and then fed into the power panel.  They are UL approved, etc.  The other ones witn a standard 115 VAC plug output have no such approvals.

> Also, solar energy isn't wasted in the battery 
> if your load is constantly running.  Most of the 
> daytime energy would go to the load and the 
> excess is absorbed by the battery.  At night, 
> the battery runs down and then gets charged up 
> the next day.  A smart designer would make sure 
> there was no waste.

For remote repeater sites where the load is a constant 24/7/365, yes it is possible to match the power design to the load.  But even then the system has to be desigend for the worst sun in December to still meet that minimum load.  By DFINITION, then in the summer, when there is TWICE the total energy available, there is just no place for it to go.  The load is the same.  THe other HALF is all wasted.

For a shack system, designed about one's average operating load, on any day when one does not fully use the shack to that average, then all excess solar energy is also wasted, because the batteries have no room for today's excess solar power.. (Generally).

That's why grid-tie wins hands down.  Every penny of solar energy is credited to you no matter how or when you use it.

Bob, Wb4APR

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