Down-sizing battery systems [RE-wrenches]

Todd Cory, Mt. Shasta Energy Services toddcory at finestplanet.com
Sun Jan 27 10:12:07 PST 2008


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You back up the whole house, even dishwashers? When I do a grid tied 
with battery back up, only critical loads go on the inverter.

Once again I feel the need to say that we do our customers a great 
disservice to not educate them about the importance of sustainability, 
living lean and conserving before we design the systems we install. This 
allows for a smaller system, which means more renewable resources are 
available for others.

The systems I do are pretty much the same as in years past. The battery 
banks are in the 10 kWh (usable) size which will run a smart, efficient 
home for 1 to 1.5 days. Storm related outages here are usually less than 
an hour, so this gives them solid operation of essential equipment 
during grid outages. A few have generators for extended outages, but 
this is not the norm, especially considering how the GVFX deals with 
generators.

This fall it became cheaper here (per btu) to heat with resistance 
electric than oil or gas so many people are using plug in resistance 
electric heaters now. As this trend becomes the norm nationally, I 
expect we could likely see rolling outages from high winter heating 
loads, and excess draw from the electrical grid. Battery back up grid 
ties are definitely more work to install, but most people around here 
want the option of having their system provide them with uninterruptible 
energy, especially considering our winter storms.

Todd


Jeff Yago wrote:

>Over the years I have noticed we are designing smaller and smaller battery banks for both grid-connected and total off-grid applications. 
>
>I think this may have come from the pre-90's solar design goals that off-grid applications should have 4 to 5 day of autonomy.  This was easy to do when the only electrical loads were a refrigerator, a few lights, and a small television.  However, this is harder and harder to achieve these days as more and more homeowners consider multiple computers, a satellite receiver, high-speed Internet, recessed lighting, a 60" television with theater-sound, and a dish-washer as must-have  necessities.
>
>To reduce battery space requirements and costs, we are starting to install off-grid systems with fewer days of battery-only capacity, and relying on a back-up generator to re-charge when solar is not available. I also think since it is now easier to sell back to the grid, perhaps there is less need for huge battery banks in battery back-up type solar systems to absorb all that excess power when installing a large solar array. 
>
>Anybody out there doing battery based systems that are starting to notice these market trends?
>
>Jeff Yago
>


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