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Anyone achive solar power overnight? Answered

Here is how to do it:

Use a standard 55 gallon steel drum and stick one of these on it.

Provide water cooling for the TEG: http://www.customthermoelectric.com/Water_blocks.html
If your water is 20 Celcius, you should pump 36 Litres/hour to keep max power output.

Also hook up piping for hot oil for heating

Now wrap it with 400 mm of rockwhool insulation.

Fill it with molten salt and heat it to 250 Celcius.

Tadaa: 24 W of power output, round the clock. (minus the power for the cooling pump, maybe 1-2 W)

I calculate that the temperature will drop from 250 to 225 Celcius in 16 hours.

To get the temperature back up in 8 hours you need to heat it with 2400 W.
You can do this easily with a solar trough system of about 3 m2. A trough is good because you only need to align every few days.

Budget
Oildrum 50\$ ?
Salt 370 kg  = 150\$?
TEG 80\$
Cooler 80\$
Pump 15\$
Piping 100\$?
Trough (plastic sheet and mylar) 100\$?
high temperature oil pump 500\$ ?

Does seem like a lot for a little.

Anyone have a better idea?

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Sorry for the dumb question, but what is this salt which is liquid, or melting, at 225 to 250 C?

Are we talking about NaSO4.10H2O, or some other salt? I think Steve already mentioned NaCl and its 800 C, too high, melting point.

What salt are you using?

Well I was now looking at Battery option. A Lead Acid Deep Cycle 12V100Ah should be able to give 50 W, round the clock. Say we only cycle it 50% to get 25W out, same a above, then we need to charge it with 75 W for 8 hours a day, and lets make that 100 to account for losses in the battery and electronics. You can get 100 W from 1 sqm of thin solar cells. Also, i made a mistake above... You dont need 2400 W for 8 hours, just 800 W for 8 hours. You should be able to get that from 1 sqm of solar concentrator, provided you insulate the pipes. Funny to think about that a barrel of salt can hold the same energy as a battery.

Solar Thermal-Electric is just not feasable on the small scale. Sadly, stick to PV for about \$6/watt for the panels and hopefully not a tonne for the storage system.

But salt melts at 800 C, which will destroy the TEC, and I don't see why you need the TEC anyway, all you need is a molten salt tolerant heater