[time-nuts] Practical considerations making a lab standard with an LTE lite
brooke at pacific.net
Sun Nov 23 20:46:22 EST 2014
It turns out that ground water that's being pumped is very similar to pumping oil. It's a limited resource.
There's a web page showing the GRACE satellite maps of California and that we are running out of ground water.
This isn't the page, but gives the idea:
So depending on ground water as a stable heat sink may no longer be an option as wells go dry.
It's been many years since the local water company has quit installing new meters.
Jim Lux wrote:
> On 11/23/14, 11:15 AM, Alex Pummer wrote:
>> 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
> I suspect more like the insolation peaks at 1kW/square meter or a bit more, the average over a day is somewhat less.
> At JPL we have a weather station on line that displays this and I don't recall seeing significantly more than 1000 W/m2.
> The nominal average 1.362 kW/sq meter at solar max is at the top of the atmosphere, and is normal to the incidence.
> The surface insolation at the equator when the sun is directly overhead is about 1.04 kW/sq meter.
> I think you'd get pretty close to that at solar noon in the Summer in Southern California, which is 32-34 degrees
> latitude, so at the solstice, the zenith angle is 10 degrees, and cos(10) is pretty close to 1.
> You do pick up some additional insolation from diffuse and scattered radiation from clouds or haze, but I'm not sure
> that makes up for the attenuation due to the same haze.
> Some time ago, I calculated that in Los Angeles (34 degrees latitude), a horizontal flat plate gets about 8-9
> kWh/m2/day in summer and about 1-2 kWh/m2/day in winter.. Tilting the collector would help a lot in the winter
> (Zenith angle is 56 degrees instead of 10), but there's no making up for the short days.
> Getting back to the time-nuts aspects, there are some charts around that show the temperature variation as a function
> of depth, latitude, soil and season. I know that for DSN, they went through all kinds of gyrations to calculate (and
> measure) this for the optical fiber timing links between the antennas and the masers. For small dissipated power (I
> doubt your oscillator is going to be putting kilowatts into the soil) you don't have to go very deep (single digit
> meters) before the diurnal variation is down in the 0.1 degree or smaller. Annual variations are bigger.
> has a bunch of charts for some unknown latitude (probably mid Atlantic states, since the data is from Virginia Tech).
> They appear to use well water temperatures as the measurement technique.
> A bit more googling found a paper by one G. Florides that refers to the Kasuda formula.. (the link is hard to cut and
> paste.. I'm sure if you google "Florides soil temperature" you'll find it)
> and gives this reference
> Kasuda, T., and Archenbach, P.R. "Earth Temperature and Thermal Diffusivity at Selected Stations in the United
> States", ASHRAE Transactions, Vol. 71, Part 1, 1965.
>>> 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.
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