Re: Is it a matter of scale?
Dan Clemmensen (Dan@Clemmensen.ShireNet.com)
Mon, 01 Sep 1997 10:00:28 -0400
EvMick@aol.com wrote:
>
> Anyway...it occurs to me that the tempeture differential between well water
> and ambient air temp in many places at many times of the year exceeds the
> minimium requirement for OTEC....(only in this case it'd have to be called
> something else)...particularly if boosted with a little solar augmentation.
>
> On the other hand...in the winter in many places the reverse is true...the
> well water temp is that much higher than the ambient air temp.
>
> In either case is a "table top" demo model possible? (or even household power
> generation?) Or ....since the reputed effeciency is only 2 or 3
> percent...must it be huge to operate at all?
>
The problem is that this is a very difuse energy
source, so you need a fairly big installation. However,
if you mostly want to use low-density energy (as in home
heating and cooling) you can in fact use well, stream, or
lake water effectively in an open-loop configuration, or
you can bury a bunch of polybutylene pipes about 4 feet
underground and circulate water in a closed- loop system.
There are companies that install residential geothermal systems.
They use electrically-driven heat pumps to boost from the 56
degree F ground temp to the house temp in the winter. These
systems have a high capital cost, but a very low running cost.
I just did an altavista search (+home +geothermal) and got
a bunch of stuff, including
http://www.cpco.com/electric/home.html
I'd love to play with this stuff with the goal of replacing the
electric pumps with rankin or stirling engines using a working
fluid with a vapor temp in the corrrect range, and using solar
boost. I suspect that this is feasible, but its not economical
for me: I work for a living. However, consider the implications
for when nanotech is available. You can get all the energy you
need for heating and cooling by running a closed-loop pipe in
the ground, horizontally or vertically, about 200 feet of pipe
per 1000 square feet of living space. A bit more pipe for
domestic water heating, maybe a bit more to power the system and
to boost for cooking. the remainder of your current domestic
power demand is near zero. So, nanotech frees you from the
power grid.