[time-nuts] Practical considerations making a lab standard with an LTE lite
alex at pcscons.com
Sun Nov 23 14:15:03 EST 2014
by us in central California, we get 1kW/h square meter average around
the year, the south even more, el Cajon will have today +29C° in the
afternoon as of 23 of November 2014
On 11/23/2014 9:49 AM, Poul-Henning Kamp wrote:
> In message <CANX10hB0KdrnaAYzGvM1gkDUJ7gkLth0AcdxCZG894hxbUScFQ at mail.gmail.com>
> , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:
>> He installs ground source
>> heat pumps for the geothermal energy. He says that they actually work
>> quite poorly in many cases.
> There is a BIG difference between geothermal and ground heating.
> Geothermal means you drill at least 50m (Iceland) or more likely
> half a kilometer down, in order to harvest water at near boiling
> point from the Earths geological heat-sources (mostly uranium decay).
> Extracting more energy than available just means the temperature
> drops temporarily. It will increase again once you reduce the
> pump rate.
> Horizontal ground heat means that you are harvesting sunshine
> accumulated in the top one meter of the soil. Much of the energy
> is harvested from freezing the water around the pipe thus pulling
> out the relatively high melting energy of water.
> If you extract more energy than you deposit sunshine, you end
> up freezing a larger and larger volume of water/soil around
> the pipe and your compressor will eat a lot of electricity.
> In practice it looks like this:
> (The two pictures show the same pipe, with and without frozen ground.)
> Finally there is vertial ground heat where you drill down only about
> 40-80 meter, tapping heat mostly from ground water resources. Most
> places the ground water doesn't move fast enough to deliver the amounts
> of energy extracted, and over time the source returns unusably low
> temperature and must be abandonned. Typically after 25-30 years.
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