RV water heater idea

I was subscribed to the "Mother Earth News" since their inception in about 1980.
There were a lot of innovative ideas shown in the magazine back then.

One was someone who installed a large water storage tank in his vehicle. He bypassed the radiator and used the tank to cool the engine. He had a fairly long commute to work so could heat up the entire tank.

When he got home he then had hose connections to circulate the water thru some form of heat exchanger in his house.

I never saw any follow up on this concoction so don't know how well it turned out.

I must have 3-4 years of this unique publication. Very original ideas that were thinking outside of the box.

There also was an article on "Sky Lids", they were roof shutters that would open and close by R-12 refrigerant phase change thru heat gain. 2 canisters on a "teeter totter" type mechanism that would control solar heat gain.

One should look at co-generation to see what has been developped for heat recovery:
engine coolant + exhaust gases
I read about 40% of engine fuel is lost in exhaust gases

mattmia2 said:

I was going to say, hx off of the coolant for the engine would be more effective.

Yes... as long as it does not void the engine waranty.

hot_rod said:

The most common DHW homebuilt around here is a 4" piece of ABS lay it in the sun for the day, a bicycle pump to pressurize it. I was looking for something a bit more reliable.

You will still need this if you don't move.

mattmia2 said:

I was going to say, hx off of the coolant for the engine would be more effective.

The advantage of this solution, if one keeps the original engine radiator and temperature control, is that there is (practically) no risk of water turning into steam.
I don't see any control on the OP system.

Your transfer area is essentially that 1in^2 cross section of metal. that is more how you make a handle that stays cool than how you transfer energy. Even if you found a small gas water heater and routed the exhaust through the flue I don't think you'd transfer a lot of heat.

For summer homes use solar to achieve over 80° and then convert an old refrigerator to a heat pump to boost that to useable DHW. Fridgidaires worked particularly well.

Did MotherEarth advocate cheating electric provider via "guerrilla market"?

I agree with Larry, no "free" power methods were recalled by me.

Some mentioned it went from "Hippe" mode to "Yuppie" mode and interest was lost by many.

reverse electric meter.Was it even possible in nineties?

Yes (I have the book). Most/all AC spinning-disk wattmeters will go backward.

BUT synchronizing a stand-alone single-phase alternator to the line is tricky and dangerous. Requires exact sync or machines and wires go BOOM. (Is much easier with 3-phase machines.)

This got "trivial" with smart semiconductor phasing. But 1990s is a bit too early (you'd pay more for electronics than domestic electric is worth/credited).

https://en.wikipedia.org/wiki/Synchronization_%28alternating_current%29#Conditions

reverse electric meter

Now with the smart watt hour meters a different price can be applied for what is taken from and what is injected in the grid. One has to pay for the connection though as you might need it when your solar panels are not enough (night).

https://en.wikipedia.org/wiki/Smart_meter

Too much private injection in a street will rise the voltage. Then the private inverters disconnect. This destabilise the grid. One solution is (private) batteries to bufffer the local production excess.

No idea, mys step son (4 people house) has spent 7000 EUR on one and has a very low electicity bill. It is quite an investment though.

One has to program the use of the wash machines (laundry, dryer & dish) and use the locally produced electricity to store DHW while the sun is shining.

I wander what Hot_rod will finally do for his RV?

hundred gallons weighs a lot.

I believe lead-acid can be less expensive than 10kwh storage is getting around $3k right now.