Would like to ask Wdyasq a Question

[wja69]

My thoughts started here with rain gutters creating energy, after reading wdyasq's post with all the equations realized, it doesn't quite seem worth the time, however this idea prompted a few other thoughts in a similar range. using a few small generators off of a drain line from out of the washing machine with the much higher psi, this obviously isn't a powering idea but a regaining of lost energy to some extent, would that possibly generate enough energy to recoup some losses from use of the appliance to make it worth while, figure I will also mention that I have a similar thought for home heating/cooling system as well as the dryer, obviously using the same precept of smaller generators along the piping nearer to the site of origination where the force is strongest. Mostly thinking of this as looking into starting a coin op laundry with the hope of off setting the utility costs as much as possible. OK I am a newbie so flam on if you feel the need. But very serious about getting into alternative energies as the utility companies are just cleaning us out. Thanks in advance for your time and commentary.

[bob g]

it generally takes a pump to push the water up the drain pipe and out of the machine

attaching a generator should cause back pressure on the pump, making its motor draw

more power more or less in proportion to the generators drag

not sure you can get a net gain out of that scheme

actually i know you can't

the motor is going to be around 85% efficient, the pump maybe 60%, the water turbine maybe the same 60% and your generator perhaps 75% at best

total that all up?  pretty inefficient without looking for my calculator i bet the overall efficiency is on the order or 20-25% tops

so for every extra kwatt/hr of drag you put on that hose, returns you maybe a quarter kwatt/hr in return?

better with a wall wart in my opinion.

unless i am missing something???

bob g

[wdyasq]

Well wja69, I regret you are a victim of the mean and cruel utility company. However, as you are planning on running a coin laundry, there are a host of places energy can be recovered.

Now IF ... I were running a coin laundry and THOUGHT I may save some energy, I'd look where I can plainly see energy going out the building ... probably the hot dryer exhaust. I expect one could use a heat pump to transfer the heat FROM the water going down the drain into the water about to go into the washer also.

Be forewarned, I doubt there is commercial equipment to capture or transfer this heat. One would need to design and engineer the tools to do this conversion. This can be very expensive. The expense of a failed prototype can be more than all of the energy saved in building several.

However, bob g has it right, there is no free lunch in physics. Any time one tries to recover energy from a pumping endeavor they are usually going backwards. Just the losses in small electrical generation units are about 60%+.

Well, good luck in your laundry. There are so many small energy saving projects there you will have plenty of things to think about before you figure out the utility companies actually do a damn good job of supplying reasonably priced power.

Ron

[REdiculous]

What I would look at is the elements in the dryer. Can you get some copper pipe in behind 'em? Batch water heaters.

I wouldn't bother w/ the exhaust...it's probably not that hot by the time all the ducts meet up. On the other hand, we had a little attachment on our dryer that let you vent to the inside and it kept the hallway warm-ish.

Ooh, if it were me I'd think about building a line dryer. Pipe the exhaust into a large box (closet?), add a clothes line...maybe. hrmm.

[hydrosun]

 the most energy is used to heat the water. A heat exchanger with the cold water going through the exhaust from the dryers might preheat the water. Then it could go through a solar water heating system. I was involve in salvaging 30 solar water heating panels coming off a coin operated laundry. They were all hooked up in parallel in line on the roof. If you want to build your own check out builditsolar.com for ideas.

chris

[ghurd]

"They" do make heat exchangers for both air and water.  Even milk.

I saw an air unit back about 1990.  It was being used to change the air in a smoke filled pub.  Warm smokey air went out, unit grabbed heat from that air and put the heat into the incoming air.  Seems like it claimed 90% efficiency, which was shocking to me.  But over all it was not a lot different than a large window A/C with a bit of extra ducting.

The dryer intakes would need ducted to the exchangers warm air output.

The problem I see with that is cooling hot 100%-humidity lint-filled air. Seems like condensation will trap the lint on the cooling coils.  I bet the commercial units have that problem worked out.

Most water heat exchangers I ever saw depended on warm waste water heating the incoming cool water, and washing machines do not drain and fill at the same time, so would maybe need a preheat tank and circulating pump.

It's not uncommon on commercial scale, but it is not something Lowe's will carry.  Some of the steel mills collect waste heat from the mills to heat the office buildings.  

G-

[Airstream]

Electrolux in Europe has been perfecting heat recovery for driers for a while - and a couple of years ago they recommended that they became cost effective only in painfully cold winter areas but now with energy costs rising it seems they have withdrawn the warnings. Any homemade method to recover heat would probably draw the wrath of your insurance inspectors if not the whole building inspector cadres.

Any passive water heat exchanger recovery would have to be double barrier to eliminate the chance of gray water contaminating clean water - and that would mean a lot of stainless steel and copper.