Friday Night Bath

[Sharkey]

Putting this here because it's RE-related (slolar powered, mostly).

One of the great simple pleasures of my life for the last 14 years has been a nightly bath outdoors during warmer weather. This came to a temporary end when I disassembled my bath while preparing to move out of the city. In fact, the bath was the first thing I dismantled when I got started.

Over the course of the last two weeks, I've been putting some effort into getting the solar water heater and tub set up here at the new property.

Here's a photo from last week, when I had to get inventive to move the cast-iron tub from one side of the yard to the other without any assistance. That's my hand truck on the bottom, with it's carrying capacity extended using some 2x4 and drywall screw technology. After the tub was put in place on some cinder blocks, I used the same rig to move the 4x8 foot solar direct water heating panel to the other side of the yard as well.



Tonight it's time to put it all to use. The flat plate solar water heater took a tub full of 52 degree water up to 94 degrees in partly cloudy conditions. After that, I engaged the backup heat source, wood. Anyone care for a cup of shark soup?



You can see the flat plate heater and it's newly fabricated stand in the background.

The corrugated iron surround keeps the heat in when heating with solar, and makes a fine furnace enclosure when I have to fall back to wood to compete the heating process. The chimney is a sheet of roofing that's been rolled into a "U", and closed with a flat sheet of roofing. The whole thing is put together with sheet metal screws.

The overflow and faucet holes in the tub have been sealed up, so that it can be filled completely up. When I get into it, the water comes all the way up to the rim. It's great not having to worry about splashing or spilling water, and watching the stars and sky while bathing is awe inspiring.

There's still a lot of work to do, I'll surround the tub with a fence to keep away fighting/screwing racoons and the assorted bears and cougar wildlife we have here. The fence will also provide a place for the towel and clothes pegs. I'll also have to build a decent side table for the tub to support the kerosene lamp and assorted drinking water bottles, digital thermometer, matches, etc.

The slab alongside the tub is something the previous owners left behind, it's some kind of flooring material, 40x48" in size, and it's made of concrete with agate and shiny stones on the surface. It's cracked in several places, but for my purposes, it works just fine.

Now, you'll have to excuse me, I have a date with a tub of 106 degree hot water....

[Stillphil]

Sharkey,

Can you describe how the flat plate collector works or refer me to a place that talks about it? I guess it has a pump on it?
Thanks,
Stillphil

[Sharkey]

This system is about as simple as it can get.

The collector is a commercial unit, although I once built my own out of copper plumbing fittings and sheet copper. Basically, the collector consists of two pipe manifolds (in and out) connected between with long copper pipes to which black anodized aluminum fins have been attached. This assembly is housed inside an insulated extruded aluminum frame and covered with low-iron glass. My home made unit used an insulated cedar box with a sheet of plate glass, less efficient, but it worked.

The tub is the reservoir. A small AC powered circulating pump draws from the drain fitting on the tub, and then delivers low-pressure water to the bottom of the collector by way of a garden hose.

The water gets heated in the collector, then is returned to the tub through one of the original faucet holes. The water circulates repeatedly in the tub all day until it's hot and ready for me. A layer of bubble plastic pool cover floats on the water to prevent heat loss.

An electronic thermostat monitors the collector temperature, and turns the pump on when the temperature gets above 120 degrees. This prevents overheating the collector. Yes, it will make steam if the water is not circulating! I'm currently shopping eBay for a true differential thermostat, which is one that can compare the collector temperature and the tub temperature and shut the pump off if the tub is hotter than the collector. This prevents the collector turning into a radiator and bleeding off the tub's heat if the sun goes behind some clouds, or at the end of the day when the sun sets.

No provisions for freeze protection are installed in this system, so it doesn't get used in the winter. A domestic solar hot water system would use a glycol-based antifreeze in the collector, and have a heat exchanger to transfer the heat to the domestic hot water reservoir. These types of systems require two pumps.

There are other types of collectors, and other methods of plumbing it all together. I have two additional collectors, once I get ahead on other projects, I plan on installing them on the garage and setting up a solar water heating system for the house so I don’t have to pay the utility for water heating for laundry and indoor showers.

[j_nigrelli]

if i understood the story correctly, you were moving Out of the city? where could you set up a rig like this in an urban environment?

and with that fire going underneath, i'll bet you could toast your nuts if the wind picked up!

[Dj]

Hey Sharkey... How much time does it take a panel that size to produce steam? What volume of steam could it provide if fed enough water to replenish the expansion of the steam out the far side?

I've been tinkering a lot lately with the idea of a solar-heated-water-jacket/well-cooled-water-jacket powered stirling-cycle engine... I know, no such thing as "perpetual motion" but seems to me that if the engine was built well enough it ought to have enough power to turn a small generator and at least reduce the energy consumption of the water pumps. If for no other reason than to have something to keep me out of trouble on the weekends.

[Sharkey]

Jeff, yes, I was living on 1.3 acres of very private hillside view property. The tub was discreetly tucked into the bushes in the center of the property.

Using the tub with a fire underneath is not recommended. Even a small bed of coals makes the bottom of the tub too hot to comfortably touch, so I always make sure to let the fire die out before entering.

DJ, I don't know how much steam you can make with this panel, I always try to avoid boiling it. I have had some pump failures that demonstrate it's vaporization capabilities.

Home Power magazine did some articles about Sterling engines, but I think theirs were powered by using a large parabolic reflector to concentrate the sun's rays on the hot components of the engine.

Google "sterling engine solar" (without the quotes) and you'll get 975,000 returns, so you can't be the only person interested in turning sunlight into mechanical power.

Remember, it's not perpetual motion if it has a source of outside power.

[Dj]

This is true... but to the uninitiated, trying to make a self-starting long-running device that seemingly has no real power source (preposterous... hot and cold air running an engine! ) ... well, that's close enough for some to consider it perpetual motion.

I've seen a lot of the type you describe, trying to focus tons of mirrors onto the hot side. I'd just prefer not to have my engine outside without cover... build a little pump house for it, if it worked out well enough.

But still, the more I think about it, the more I think it'd just be easier to build something like a parabolic mirror steam boiler out of an old C-band satellite dish I have laying around. And if I'm going towards steam instead of simply hot water... why not just go ahead and run a steam turbine or such. :shrug: