solar vacuum tubes overheat - steam engine

[george (dicegeorge)]

I've bought some solar vacuum tubes cheap (without instruction) (perhaps navitron)

someone says if i put the hot water tank higher than them then i wont need pumps.

But what happens when the hot water tank is at 99 degrees at noon on a hot august day.

where does the excess heat go?

does it get hotter and hotter until the solder melts?

or can the vacuum tubes get super hot?

or can i harness the excess heat in a steam engine and get electricity?...

[g]

[AlanD]

You need to build a 'heat dump' into the system to allow for this.

I have a system with 30 Navitron tubes, but a reasonably small cylinder (due to space issues) so have built in a heat dump mechanism to deal with this. The cylinder coil used for the HW primary circuit goes via a towel radiator in the bathroom before returning to the boiler (so in 'nornal' boiler heating mode the water goes boiler, pump, zone valve, cylinder, towel rad, boiler), so when heating water the bathroom rad gets hot too.

I use an 'excess cylinder heat' output from the solar controller to enegize a relay, which:

• Disables the bolier 'call for heat' input, so the boiler *cannot* fire, in-case a stat is at a stupidly high setting,

• Energizes the HW zone valve, which in turn energizes the CH pump.

This causes water to flow from the cylinder coil to the towel rad, then onto the boiler (which is off) before returning to the cylinder. This has proved to be very effective at preventing the system going beyond a sensible limit - heat dump triggers at 80 degrees and system has never reached 85 degrees.

There is a data logger on my solar contoller, and when I have plotted the data to a graph the effect can be seen clearly.

HTH, Alan.