it might not produce MUCH electricity but any at all would be helpful, even if just to run a filter pump or a light at the pond.
we are planning on attempting to put in a flowing well to our pond..which is common in our area..and if we can get enough force to try to run some type of elec system off of it..although probably quite small.
Please, do the engineering and experimentation. Many of us would be interested in the results. Presently, I'm on "city water", and have always been curious if an in-line rotor would supply enough electricity to be useful. The trade off is that water pressure will drop by whatever energy the rotor consumes.
At the least, it could make doing the dishes or laundry more "rewarding".
John Polk wrote:
The idea is good, but can it be done cost-effectively? To get the water into your tank, you will need a more powerful pump (and motor). The cost of a tank large enough to be of use (plus the cost of the tower) would probably be greater than a PV panel that could provide more watts.
In our area, the water from the roof of the tank would be enough to keep it full. I had thought of something similar, but instead of a tower and tank.... a tank in the eaves of the house. The south side of the house feeds a heated tank.... heated by a solar panel lower than the tank that thermo-siphons. The north side of the house (hopefully with more storage) holds the cold. I don't know if there would be enough pressure for a shower... but for everything else.... Not potable without good filtering though.
I had also thought that this eaves tank would hold enough water to keep a small turbine going while filling the water barrel at ground level (several small turbines for most people... we have at least 6 down pipes here).
But I'm afraid the numbers are very challenging.
Changing the piping size will increase pressure but decrease flow. The best way to do the calculating is to realize that the overall energy in the water is just based on the weight of the water and the distance it falls. The energy is "potential" energy of a mass held at a height. A basic unit of work/energy is a "foot-pound" - e.g. one pound dropped one foot. We change from work to energy when time comes into play - since dropping that pound one foot in second is different from lowering it over an hour.
I can run through some numbers and, for now, leave out system (in)efficiencies such as piping friction, generator inefficiency.
40 foot-pounds in a second is about equivalent to 50 watts of energy.
A gallon of water weighs about 8 pounds.
(a) So dropping the gallon of water 5 feet in one second is about 40 foot-pounds and generates 50 watts for that second...
... which means, 60 gallons dropping 5 feet over one minute will generate those 50 watts for a minute
...... and 3,600 gallons dropping 5 feet over an hour to generate 50 watts for an hour.
[I'm pretty sure an overall system efficiency of even 50% would be a challenge here which would double the water requirement to 7,200 gallons in an hour.]
(b) you can raise the height of the tower (in typical hydro systems you seek out a greater "head" which is your stream drop). But moving to a 20 foot tower quadruples the feet and allows you to require 1/4th of the water -- still... 900 gallons dropping 20 feet in an hour to light that 50 watt bulb.
Sorry to dampen (pun!) things. Hydro really needs masses of water and it should be running downhill as much as possible. We don't appreciate it when we see a small stream running. If that is 5 gallons of water each second passing by/down we don't realize that this small creek is sending 18,000 gallons by in an hour -- thats a lot of water to hold in a tank!
A small farm-pond at a higher point on your property would store a lot more water... even a pond 16 feet across and 8 feet deep holds about 12,000 gallons weighing almost 100,000 pounds. IF your pond is 40 feet higher than the generator and if you could achieve overall efficiency of 50% you could get that 50 watts for about 24 hours before it ran dry.
Corrections/comments welcome. I'm no expert but have spent some time with these numbers !
keep this post going..I'm going to mention this to my genius son and see what he can come up with..sure get a lot of pressure when we have a storm with the gobs of water running off my roof through my drain system to my pond !!
Brenda Groth wrote:
keeping this up near to top to get more input, this is very interesting, you know I never thought of using the water from the eaves to turn a generator, with all the rainstorms we have had this spring it would have charged a lot of batteries..even with just a simple auto type generator..maybe even off of some rain barrels or just something put into a drain??
[font=Verdana]It IS interesting - but remember.. the numbers "drive a hard bargain" ! Lets try this one out!?
A 1 inch rainfall on the two halves of an A-frame roof that are each, lets say, 15 feet by 30 feet.
That is 75 cubic feet of water or almost 5000 pounds of water. Let it fall through your downspouts about 10 feet and you have 50,000 foot-pounds of potential energy. Lets say you get drenched by all that water in an hour! (with Global "climate chaos" that is happening more and more). That would give you 50,000 foot-pounds in 3600 seconds or about 14 foot-pounds of energy per second. With perfect efficiency in your system you'd get about 17 watts of energy continuously for the hour. With realistic efficiencies probably more like 5-10 watts.
I'm afraid that's not much.
It would keep one CFL lit for the hour, maybe.
That would be cool I guess!
With perfect efficiency in your system you'd get about 17 watts of energy continuously for the hour. With realistic efficiencies probably more like 5-10 watts.
I'm afraid that's not much.
It would keep one CFL lit for the hour, maybe.
That would be cool I guess!
Or enough LED night lights to keep from tripping till the power came back... or it got light out. That is why I decided it would be better for water storage for someone with no city water... or a water meter. It would work for flushing (if you were that wasteful) clothes washing and maybe showering. It would need to be filtered to drink. The power saved from a pump for pressure to pull it out of the ground would be far more than you could generate. One days rain here was more than enough (much more) than needed to fill a 55 gallon drum. (PNW) Heating the water with solar would save even more power... $20 a month around here.... a lot more if you are off grid.... maybe a lot more in two years even on the grid.
There are a few thing where electric power makes sense (not needed anywhere really). Night time lighting is one, refrigeration is another.... computers and communication? They need it for sure, but rely on some kind of grid for connect.... but most of all manufacture. Entertainment too, though, I would be happy reading a book or playing an acoustic instrument for music.
Energy conversion needs to be conserved... use it in the form it shows up in as much as possible, rain water as water pressure and collection is best use until you have enough of a surplus for power.... probably a stream. Sunlight best use would be light and heat first... then power gen for night lighting etc.
... maybe I'm dreaming but I think with a grid that just goes off some day, priorities need to be set.
They're probably the best alternative energy forum on the planet.
The general consensus is that if you custom built a "low head" microhydro generator, and you channeled all the water from your whole roof through one pipe, and you got a long heavy downpour, you still wouldn't make enough to light a useful lightbulb, or store any "excess".
There's just not enough potential energy there. You might get a generator small enough if you cannibalize one of those hand crank flashlights. Finding a way to get the water to turn even that tiny thing will be an adventure.
So, A+ for thinking outside the box, but unlikely to change your life in any meaningful way.
If it wasn't enough for electric, it could still be a gravity feed for a stock tank or something similar.
Dander: Do a little research on water wheels and in stream turbines, many types have efficiencies in the 80-90%range.
Hmmm... well actually I have done quite a bit of research. I'm not sure about marketing claims (efficiencies are often a murky area) but you can calculate the efficiency of any unit based on the manufacturer's energy-output specs. These they do provide. (And, frankly I have the impression that the micro-hydro companies are eager to make sure you know what you get).
Consider, for example, the Harris "High Efficience PM" - a widely respected unit. This is a $2300 unit. Performance data chart taken from Backwoodssolar.com.
With a good high flow of 50 gallons-per minute and a good drop of 100 feet this unit is stated to produce 500 watts continuous.
Let's compare with the theoretical output:
50 gallons of water is about 400 pounds so we have 400* 100 = 40,000 foot-pounds per minute. Divide by 60 and thats somewhat more than 650 foot-pounds per second. Times 1.356 to get watts and the theoretical energy in that much water dropping that far is 880 watts.
So.. the efficiency of the unit is 500/880 or 57%.
This does not include smallish losses due to friction in the piping or electrical line losses or losses from conversion of DC to AC. I think 50% is a good estimate.
Home-brew units are cool but could rarely get the efficiencies of a highly-engineered unit like the Harris.
I would be very interested in knowing the names of manufacturers who claim 80-90% efficiencies. If they are using some other scheme for calculating efficiency that would explain our disparity I suppose. But comparing the output energy to the energy actually in a mass of water falling a distance, as I did in the above comments, seems like the only legitimate way to evaluate speculative systems such as those proposed above. You can't get more energy out of downspouts, rainwater or anything else than is actually available.
I am not trying to dampen anyone's enthusiasm for new and creative ideas - that's something I love about permaculture. But I do believe it is a mistake to imagine that the only reason our culture is hooked on fossil fuels is greed or stupidity and that we have a monopoly on their opposites. There is a stupendous amount of energy in a gallon of oil and it takes a lot of wind and/or sun and/or falling water to match those. Hydro, in my opinion, is a niche energy source and not a particular bargain unless you have a good-sized stream.
Read a short article in Farm Show, vol 34, no4, 2010, "Home-Built Water Wheel Generates Electric Power." The water wheel they built to work off of channeled water from their spring-fed pond is attached to a 100-watt generator. The generator preheats water at his son's house.
By the way Suzy-Bean. I forgot to mention that "Farm Show" is a fantastic source of inspiration for me as well... we just have to look a little more "under the hood" to be sure projects like that are worth the hours in our days that we put into them !
My recently-purchased property actually had a huge (8 foot diameter), hand-made hydro wheel attached to a large generator and taking its water from a good-sized farm pond up about 50 feet higher than the cabin and about 500 feet away. It wasn't functioning and we had to decide how much time to put into fixing it up.
It seemed like a nice scheme to charge-up the batteries when the sun and wind weren't cooperating (solar PV and a small wind generator were also there). It had a large diameter pipe from the pond and I figured 100 gallons per minute was possible.
It was possible, but... when I did the calculations, which are similar to those above. I realized I might get 300-500 watts output. Run that baby for 4 hours and you've got at best 2 kwh, maybe 100-150 amp-hours of battery charging.. not too shabby.
But 100 gallons per minute times 60 minutes is 6000 gallons per hour or about 25,000 gallons drained down from my pond in those 4 hours. The pond is 30 feet across and about 5-8 feet deep. 25,000 gallons is about 3000 cubic feet of water so the pond would drop about 4 feet. Not such a good deal - we decided.
Like I said - do the numbers and we are usually humbled!
all the best...
p.s. We will observe the pond's overflow and recharge rates sometime this spring and summer and might still decide on a smaller, more efficient micro-hydro unit if the pond can really recharge 4 feet of drop in level. In our area we already notice that the windless and sunless times are often the wettest (e.g. March, April). The waterwheel we passed on to a friend of its maker who has a good, flowing creek on his property.
By the way... administrators - shouldn't this thread be moved to the "alternative energy" forum ?
I understand that putting tyres in water is not the best solution, however it beats them going to land-fill and collecting water, which stagnates and causes more issues.
I know that your calculations for energy are accurate and I agree, you can't get more energy out than is there to begin with.
System efficiencies are a major draw back, I'm off grid and am considering adding a hydro electric system into what I've got, unfortunately there are multiple legal hurdles with every agency under the sun giving the standard bureaucratic "NO" to any thing that has to do with me using the water way for anything but scenery. (Fish and Game being the worst)
You can't expect to wield supreme executive power just because
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