[Discuss] Eclipses Re: Great talks last night, however...

[bogstad at pobox.com (Bill Bogstad)]

On Mon, Jul 24, 2017 at 12:10 AM, grg <grg-webvisible+blu at ai.mit.edu> wrote:
> On Sun, Jul 23, 2017 at 04:59:08PM -0400, Richard Pieri wrote:
>> On 7/23/2017 3:42 PM, grg wrote:

>> The ground can hold a lot of heat energy but it doesn't conduct it much.
>> That's why a GHP spreads its ground loop system out across a large area.
>> You're not getting that from burying big battery packs unless you also
>> install the same kind of extensive ground loop system which costs to
>> install and maintain.
>
> Look at it this way: if you put a battery in the ground underneath a solar
> panel, the warming of the ground from that battery is going to be strictly
> less than the warming of the ground from the sunlight hitting it directly
> before the solar panel was installed.  With an 85% charge/discharge
> efficiency, the ground is being warmed only 15% as much as under direct
> sunlight.  Since there wasn't runaway heat buildup under sunlight, only 15%
> of that amount of heating is also not going to exceed the earth's ability
> to sink the heat away.

Grg, I suspect that the above section is correct overall; but you do
seem to be assuming
that the absorption/radiation characteristics of a solar panel
installation across the entire
spectrum are the same as bare ground.  Of course, you have the
advantage that a nominal
85% of the energy you put into the batteries is going to be delivered
back out to some "remote"
location so that energy isn't going to be warming up the local battery
environment anyway.
That probably provides sufficient breathing room to make it even less
of an issue for small
scale installations.

For larger utility grade systems, we might be looking at flow
batteries in the long run anyway
and there is no reason that the storage system needs to be that close
to the generation
system.  Build them wherever cooling/heating/physical space/proximity
to load considerations
make the most sense.

This article from ars technica:

https://arstechnica.com/business/2017/07/german-energy-company-wants-to-build-flow-batteries-in-old-natural-gas-caverns/

talks about a commercial project to do just that in Germany as well as
other projects elsewhere.  Without any pricing info,
it is difficult to say if this is viable, but it seems like a number
of groups think that it might be.

Bill Bogstad