undefined | Better HN

0 pointshyperpallium9y ago0 comments

The problem is demand will vary the same for all those in the same locality with time of day.

Now, if you could somehow form a grid with people on the opposite side of the globe...

BTW I like the idea of hydrobatteries: hydroelectric power stations sometimes pump water back up into the resevoir. One could do this with local water towers; perhaps even dual-purpose existing rain tanks, per house. Maybe not large enough; haven't done the math.

0 comments

MrsPeaches9y ago

Here you go:

E = mgh

1000l tank = 1000kg

7m high roof (~2 stories)

E = 1000kg * 9.81ms^-2 * 7m

=~ 70 000j

1Wh = 3600j

So a 1000l tank on your two story high roof would be able to store ~19Wh

Not including mechanical losses

For comparison a single decent sized SLA battery will be able to store 1000 Wh

hyperpalliumOP9y ago

Thanks! Not as good aa I'd hoped...

LeifCarrotson9y ago

The numbers work better with increasing size, because volume is the cube of the dimensions. Also, you can build a pond on a hill with some excavators much more efficiently per unit volume than an enclosed plastic container.

A 1m cube weighs 1,000kg and has about 20Wh. A 10m cube weighs 1,000,000 kg and has about 20,000 Wh. A 50m deep, 1 km square reservoir has 1,000,000 Wh. And that's still assuming that it's 7m above the turbine!

j / k navigate · click thread line to collapse