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Author Topic: Solar anyone?
TheMoMan
BlabberMouth, a Blabber Odyssey
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Icon 1 posted April 08, 2016 15:33      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
The tesla thread got somewhat high jacked.

Solar power and collection: Solar Steam engine using a closed loop with a Freon type gas as as the liquid and gas to drive the generator this could be totally closed like a home refrigerator, so that the gas does not leak away.

Thoughts?

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Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5848 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
The Famous Druid

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Icon 1 posted April 09, 2016 00:23      Profile for The Famous Druid     Send New Private Message       Edit/Delete Post   Reply With Quote 
At the risk of being accused of hijacking...

Yesterday was the anniversary of Casa del Druid going solar.
Looking at the stats, our (nominally) 4 kW PVs have generated 5015 kWh in 366 days = 13.7 kWh per day.

We've exported about 2900 kWh to the grid, and bought 3800.
So, we're generating about 85% of the electricity we use. If I could convince the druidlings to turn stuff off when they finish, I reckon we'd be about break even.

--------------------
If you watch 'The History Of NASA' backwards, it's about a space agency that has no manned spaceflight capability, then does low-orbit flights, then lands on the Moon.

Posts: 10680 | From: Melbourne, Australia | Registered: Oct 2002  |  IP: Logged
TheMoMan
BlabberMouth, a Blabber Odyssey
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Icon 1 posted April 09, 2016 10:44      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
TFD My brother the Engineer and myself both agree that PV cells are inefficient and might be beat with a closed loop steam system, or thermopiles (think lots of thermocouples in series) with the cold junction shielded from the heat.

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Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5848 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
The Famous Druid

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Icon 1 posted April 09, 2016 20:31      Profile for The Famous Druid     Send New Private Message       Edit/Delete Post   Reply With Quote 
Modern PV cells have a conversion efficiency of around 20%, with expensive experimental cells achieving about 25%, the theoretical maximum is 33.7% (source)

Not a whole lot worse than the best experimental solar-thermal-electric which runs at 31.2% efficiency.

Both compare unfavorably to solar water heaters where efficiencies over 60% are common.

Which is where PV-Thermal hybrid systems have a lot of promise.
There are several different designs being trialled, but the basic idea is you run water through pipes mounted in or behind your solar PV panels.
The water keeps your PV panel cool (PV efficiency drops when they're hot) and you capture that 'waste heat' to use in your morning shower.

With some manufacturers claiming over 85% efficiency (yeah, I know, "manufacturers claims" are sometimes dodgy) they look pretty appealing.
There's even an aussie company making roofing material with PV-T built in

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If you watch 'The History Of NASA' backwards, it's about a space agency that has no manned spaceflight capability, then does low-orbit flights, then lands on the Moon.

Posts: 10680 | From: Melbourne, Australia | Registered: Oct 2002  |  IP: Logged
TheMoMan
BlabberMouth, a Blabber Odyssey
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Icon 1 posted April 10, 2016 10:15      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
I must have been looking at old data that was quoting 10-15% conversion. On the thermopiles is that with pellitier junctions?

I have used them for CPU cooling, small wattage units low BTU.

--------------------
Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5848 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged


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