[permaculture] batteries vs grid-tie

Stephen Sherman spsherm at msn.com
Tue May 12 13:51:07 EDT 2009


I can't seem to find the original post, but here are a few thoughts...

Batteries add to the cost of a system, but they provide power when the 
grid is down. Not only from the power they store, but also because many 
(perhaps most) grid connect/battery-less inverters won't invert if the 
grid is down, even if your PVs/wind are making electricity. So it really 
depends on what you want out of your system. Do you need electricity 
when the grid is down? Do you need your AE system to act as a UPS for 
some critical equipment? If so, you probably will need some batteries on 
the system and an inverter designed to use them.

Personally, I think having some batteries and grid interconnect is the 
ideal, in that it allows you to use the grid to take the extra power, 
and still allows you some electric power when the grid is down. At least 
it is a good solution for my situation. YMMV

I'd be very cautious about bringing any batteries indoors into a living 
space or connected to one. Even the sealed batteries can pose a serious 
health and fire hazard if something ever goes wrong. Better to construct 
a separate space for them if you need to shield them from weather extremes.


Rain Tenaqiya wrote:
> In general, I've decided that if you can easily connect your energy system to the grid and avoid batteries, that's the way to go.  Batteries have a high embedded energy, though they are recycled.  If lithium batteries ever become affordable for home systems, that would be a big improvement.  However, the grid has the potential to even out the supply and demand of energy, making renewables more viable.
>  
> On the other hand, your system is very small (a little smaller than mine), and the cost of the equipment required to hook up to the grid may not be worth it in your climate.
>  
> As for your fridge (I also have a small Nova-Kool), the hot temperatures must consume a lot of the energy that your panels produce (mine uses about 240 watt hours/day).  You might want to install a low voltage disconnect to protect your batteries.  Bringing the batteries indoors would extend their life and increase their capacity, as well.
>  
> I hope this helps,
>  
> Rain
>  
>  
>
>
>       
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