Solar water heating

[Solar Flare]

I know you can't read this so it won't matter

wrote:

[Mary Fisher]

b) it might at present

a) Is that your sole criterion for the value of solar water heating?

Then do it. save money and emissions in some other imaginative way.

[meow2222]

The panel output leg has a 1/4" hole near the top of the tank. As soon as water stops flowing, the water in the output leg is replaced by air that enters this hole. At this piont you then have a panel full of water, and one leg full of water, one empty. The lot empties back through the pump. There is no need for any hole high up. The one must is the panel output piping must be at least half inch, not quarter inch, so that air can go up and water down at the same time.

There are no doubt many ways to c*ck a design up. It seems logical to confine our examinations to competently designed setups.

Air target temp is low, the output air need only be mildly warm, low temp panel operation equals good efficiency. With hot water the target temp is close to the stagnation temp of the panel, so once the water is halfway hot the panel efficiency is way down. If the water ever reaches panel stagnation temp, efficiency has by then dropped to zero. This is one of the various plusses of hot air panels.

Curious how you plan to use the same panels for both water and air :)

NT

[Mary Fisher]

There isn't a 'boiling wash' on our machine, I've never had one which had - since the gas boiler but that was hardly a machine.

I doubt that there are any 'boiling washes'. They're not necessary and harmful to some fabrics.

Well, you said you were here to learn.

Mary

[S Viemeister]

My machine has an almost-boiling wash - 90C/194F.

[AJH]

OK I thought a hole was necessary, what you now suggest is much the same as my thoughts but in a different leg, so much less likelihood of waste pumping.

OK again, in fact the efficiency of either given the same delta T is about the same, the air system has less to warm up and so should react quicker to take advantage of sunshine.

Even this is somewhat dependant on what algorithm you choose to make use of the heated water, in my case I will almost certainly feature a thermal store, because this fits in with wood burning, it certainly adds a lot of cost but would enable harvesting of sunshine at a low temperature.

It's still a pipe dream atm, my heating is largely provided by wood that just costs me a bit of effort to collect, so investment in solar is not a good one for me.

If I were faced with re roofing (1862 built property seems to have been re roofed once after fire damage) then although it is SW facing a warm roof with triplewall polycarbonate weather surface looks feasible.

To implement this my thoughts are that the solar DHW could be supplied by a small portion of the roof and aim for enough collector area to fill a thermal store and supply all summer and some spring and autumn needs. I wonder if I would get away with circulating the water through just the front face of the two channels, water is pretty opaque to IR.

If so then the air doesn't need to share the same passages and can have a manifold to the rear channel over the whole length of the roof blowing down to the bottom and into the lower part of the building, ideally into the floor slab.

Strangely enough I have just returned from the ongoing task of clearing a house, now that it is not occupied the evacuated tube panel is showing some gain, the collector actually showed 57C and it was overcast today. When the house was occupied the gas central heating was set such that the panel never made a noticeable contribution. I am in two minds whether to nick it off the roof before it is sold as the estate agent says it does not increase the value of the house.

AJH

[Steve Spence]

Many Americans don't wash clothes with hot water.

[Solar Flare]

You can usually pick them out with their greyed out white clothes.

[Steve Spence]

hmm... really? nope, not quite right. It's been a long time since detergent required hot water. Saves a lot of energy as well.

[Solar Flare]

I have some watches for you to buy too. You are a salesman's dream. Try reading the boxes of detergent even. The brands I have at the current hide this information completely.

Cold water is always defined as over 20C for detergents. This is "warm" water from your taps...not cold.

NOTE: Temperatures below 65 degrees F. will not activate laundry additives and may cause lint, residue, poor cleaning, etc. In addition, detergent manufacturers and care labels define cold water as

80-85 degrees F. "Cold water below 65 degrees F. is not recommended for washing" "As long as the water temperature does not fall below 70 degrees F (21 degrees C), you will still be getting your clothes clean." http://72.14.203.104/search?q=cache:jZZU6ZdhuWsJ:extension.missouri.edu/explore/hesguide/clothing/gh0134.htm+detergent+effectiveness+cold+water&hl=en&gl=ca&ct=clnk&cd=6If thermal energy (water temperature) is reduced, chemical energy (laundry product) should be increased by adding more detergent. "Launder using hottest water safe for fabric" manufacturer defines "cold water" as 65F-85F. This is not cold water from your taps. on and on.

The laundry detergent scams do not really agree with the chemical scientists. The detergent companies had to redefined "cold water" to make their claims. Advertising at work.

Have a good one.

[Mary Fisher]

True. Same in England.

Mary

>

[Doctor Drivel]

In the UK we don't have cold water detergent. Well not that I know of. If it is so good and equal to hot water detergent, then the energy crisis is partly solved. Just disconnect all the washing machine heaters. Washing machines a few years back were the appliances that were near causing the California grid collapse. They put out on TV for people not to use them as much and have only full loads.

If it is so good, I want some and will meddle with the washing machine to get it to work cold only. Or just set it to low temperature wash.

[Steve Spence]

I'm told my other UK folks that you do have cold water detergent. I don't know personally, I've never been to the UK. Our washing machine (Sears front loader) has a (wash/rinse) cold/cold, warm/cold, hot/hot settings. It doesn't have a onboard heater. We always use the cold/cold unless I'm washing my greasy clothes, and the whites are never gray, and the colors stay bright.

[Mary Fisher]

Biological detergents are universally available. Many people will be using them without understanding that they can be used with cold or tepid water. 'Ozone' detergents are most often used in commercial laundries.

In the machine I use the former; for hand washing (pure wool) in warm water I use soap flakes.

I don't have grey whites or dull colours.

Mary

[daestrom]

Why go all the way up to the panel height? If you make sure the hole is always above the water level in the tank, and put a small enough orifice/restriction in the hole, the flow of water out the hole will be minimal. With the pump off, the difference between where the hole is and the water level in the tank will start the reverse syphon process. As water syphons backwards through the collector and pump, the return line will be more and more air (less and less water) so the dP for the syphon grows and grows. Soon the whole pipe and collector will be drained.

Things that can go wrong: 1) If there are any low spots that don't slope back to the tank, they may hold water that can then freeze. 2) Some fool puts a check valve in the line. 3) If the orifice/restriction/hole gets clogged with scale/crud/biofouling, then the system may not drain. The first two are avoided by careful installation. The last, increase the height above the water line for the hole to provide a stronger dP for clearing the crud. Heck, maybe rig a circuit that if the pump is running but no water out the hole after 60 seconds, sound an alarm. Scale could be prevented with a simple mechanical reamer every 3 months or so.

But running a pipe all the way up to panel and pack down creates a 'loop-seal' that will *prevent* drain down, exactly the wrong thing. Now you have to 'upside-down U' sections of piping to break the syphon seal on both to prevent freezing.

daestrom

>

[daestrom]

Not entirely. To prevent forming steam in the top most portion, the pressure there must be kept above the saturation pressure for the temperature. So if the collector outlet temperature is 180F, the pressure must be kept above 7.57 psia. With the return line open to atmosphere (14.7 psia), then the vertical fall from the collector to tank is limited to somewhere in the range of 16 ft.

If you arrange so the major friction loss is on the return line, say a throttle valve right before the tank return, then the pressure drop across it will add to the pressure 'seen' at the panel (i.e. the backpressure raises the pressure in the panel). This would support more vertical height panels.

The *worst* thing would be if the throttle valve/restriction were on the riser side.

daestrom

[Doctor Drivel]

Because it is "foolproof" and will "always" work, no matter what pump, or extra panels you insert later. Just putting the bombproof method forwards, nothing else.

As the end of the pipe is open to atmosphere in the tank at "all times", it will not cause a vacuum and lock in the water. When the pump is on, it will pump some way up the pipe, how much depends on pump friction, etc. Once the pump stops, the water in the pipe will drop back and as it is a open vented pipe, the water will just fall back.

The last thing you want is water dropping from a small hole inthe wtaer in the tank, as this aerates the water. Not what you want.

[daestrom]

Now that's 'Drivel'. Washing machines in the US don't have 'heaters' built into them. (well, maybe *some* brand out there does, but by and large the most common units do not). During the CA energy crisis (I would hardly call it a 'collapse' since the only time people lost power was when it was deliberately *turned off*), the messages went out for people to do a *lot* of things differently to conserve energy. Not just washing machines. And to shift there energy usage to off-peak hours. But not just washing clothes. Running A/C, taking showers, cooking dinner, any thing to reduce peak demand.

daestrom

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Doctor Drivel" saying something like:

That was a concrete mixer. Understandable mistake, I suppose.

[Morris Dovey]

| Now that's 'Drivel'. Washing machines in the US don't have | 'heaters' built into them. (well, maybe *some* brand out there | does, but by and large the most common units do not).

At least some of the big name manufacturers' top brands do indeed incorporate heating elements.

The Maytag Neptune series is the only one of these with which I've had first-hand design experience. It should be noted, however, that the heater is used under computer control in such a way as to reduce the overall water/energy budget of the machines' wash cycles.

I was also told that they'd experimented with incorporation of an ozone generator into some test machines with the aim of reducing detergent and bleach use; but that the idea was dropped because the ozone unacceptably shortened the life of some common synthetic fabrics.

I had an opportunity to examine a Japanese machine that used a flood of tiny air bubbles to completely replace detergent - and I understand that the technology is considered "promising".

The primary factors involved are 'wetness' and the mechanical action of flexing fabric/causing water to move between the fibers. Detergent acts to make water "wetter". Warming the water improves its ability to disolve some types of soil. If the water were cooler, the machine would need to run longer to produce the same level of cleaning. The real deal is to make the machine smart enough to figure out where the optimums are each individual load - because the parameters change dramatically from load to load.

They've been working on it; and the development has been (and will continue to be) an iterative process.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA