If you want the most energy-efficient shower to make the most of your solar hot water, in addition to the shower heat recovery device you might also look at the shower design itself.
While I am not a particular fan of their overpriced refrigerators, the Sunfrost people have a fascinating take on showers on their website at http://www.sunfrost.com/concepts_sustainable.html
Their design makes great sense, I believe, and I am seriously contemplating using it in the house I am designing for my family now.
--- In Sola...@yahoogroups.com, "John Allen" <johnaallen@...> wrote:
> I like the enclosed shower idea, and I was attracted to the mention of 1/2
> Gallon of water Per Minute, GPM, shower flow rate.
> I have a shower head that works fine at 2 GPM and it has a shut off valve
> that allows me to throttle it down and up without affecting the
> mixture/temperature. At 1 GPM it is sort of OK. but below that it just
> I resurrected a prior shower head that did not have a built in valve, and
> added a ball valve to it. This one has more of a needle like spray and can
> still project a couple inches at about .5 GPM, but it is hardly satisfying
> at that rate. It is acceptable to me at .8 GPM but my family prefers to run
> it at it's max of 1.5 GPM
> What flow rates do you all live with? Does anyone care to recommend their
> shower head?
> John Allen
I have a sneaking suspicion that the very low rates don't rinse well, so actually take more
total water. Of course, one of the best ways to save a lot of water in the shower is to get
wet, then turn off the water while soaping down. The design of the subject shower stall,
with its fairly tight construction and the metallized bubble-wrap walls would be very
comfortable while showering in this way.
> On a sunny day, I'm almost producing all the hot water I need via
> collector and I think I can make it to 100% by reducing flow rate
> shower. I'm particularly motivated because I have an old gas water
> that I want to completely eliminate. I estimate it is only 50%
> that it's daily stand by loss is about 20 degrees * 40 gallons *
> per gallon or ~7,000 BTUs. In addition I estimate it is using 12
> of natural gas per day for the pilot light. (another 12,000 BTUs),
> 19,000 BTUs is roughly the same as my daily hot water need - 50
gallons * 40
> degrees * 8 .3 pounds = ~ 17,000 BTUs
> Can anyone confirm these estimates or point out a likely error?
Doesn't the pilot light heat the water?
Ho JohnYes a small electric hot water heater is all you need to back up your solar hot water system. Heat recovery from the drain ( as David neley mentioned) is also a good idea. Very small water heaters may be purchased from people who sell mobile homes or you could make your own with heat tape and a copper coil.John
John A Allen
Various people mentioned a concern about reduced flow showers having poorer rinsing ability.
Most modern low-flow shower heads do surprisingly well in this, since they mix a large quantity of air with the water. This increases the apparent volume as well as the motion of the water, allowing it to do more than it would if it were a mere stream of water.
I suggest doing your homework before you purchase your next shower head, to get ones that are well rated in performance as well as being low in flow rates. Even some surprisingly inexpensive ones come out quite well in this regard.
For the gentleman who "doubts he will get rid of his ceramic tile"--be aware that this kind of mass is exactly what works against comfort in the shower. It simply takes too much energy to warm the tile and keep it that way. That energy must either come from some sort of heat source or from the water itself.
One key to the original design is the low mass of the enclosure combined with the insulation around that low mass. It could easily get warm and tend to stay that way. Thus, if you ignore that component you are not likely to have results as good.
Have you not added an insulation blanket to your heater?
If you have a conventional, tank-type heater, these insulation blankets can help immensely. They are available for less than $20 in most big-box stores like Home Despot, and from small hardware stores as well.
If you insulate sufficiently, you can make up some of the difference between the conventional heaters and the tankless ones. If you have the budget, a tankless heater designed to function as a backup for a solar heating system is likely the best option for most--although if you are in a cooling climate and desire air conditioning, it is hard to argue with a geothermal heat pump with desuperheater option that uses the waste heat from the cooling cycle to heat domestic hot water rather than pumping that heat into the ground.
> Doesn't the pilot light heat the water?
Most certainly. But the tank still gets about 20 degrees colder over a days time if I turn it off.
Since your shower appears to be over a crawl space, you may be able to install a GFX unit there. Rather than running the heat to your heat storage tank, it is much more sensible to run the shower drain heat back into the cold input line to the shower--actually, running the cold line to the GFX before it goes to the shower is how it is usually done. This raises the "cold" side temperature, so you use less from the hot supply.
Typically, the GFX unit is said to capture about 65% of the waste heat from the drain. If your base water supply temperature is 60 degrees, and the drain is at 98 degrees, one would expect the supply to become about 84 or 85 with the use of the GFX on the "cold" side. This reduces the amount of hot water you would need to bring the water to comfortable temperature in the shower.