Self- Sustainability

Discussion in 'Earth Science' started by quinnsong, Feb 21, 2014.

  1. Aqueous Id flat Earth skeptic Valued Senior Member

    I suspect at some point the quinnsong family will be arriving at that place but it looks to me like they're just glancing at the map right now.

    That would be great for a thread that had some appetite for technical detail. I did float a 6W per swept meter for wind and 1kW peak incident power per sq meter for solar, thinking I might picque quinn's interest in getting down to particulars. At this point I'm just offering very general ideas, little or no risk, just to whet Mr Q's appetite and see if he might find any of this of interest. I also had in mind that this is some small piece of a larger future he is building while shouldering the burden of military service, and that moves me to send a shout out in the form of some random ideas that may or may not ever be of use to him. But if they give him five minutes of rest from his duties, just pondering wild hare schemes, then mission accomplished.

    Actually you yourself are a good source for specific advice. My approach is neither specific nor advisory, not even touching on systems level considerations. I'm at that place where all the ideas go up on the board first and then at some point Mr Q crosses out the ones not best suited to his interests. At this stage, when the requirements are unknown, the principle that comes to mind is If at first all objections must be overcome then nothing would ever be attempted.

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    So far, the things I see suggested include:

    (1) a micro hydroelectric generator
    (2) a small photovolaic array
    (3) a home grown ethanol crop
    (4) a lighting system using LEDs
    (5) a conventional small turbine
    (6) a low cost generator (e.g. car alternator/battery) powered by a homemade prop on a rugged(e.g. car wheel) bearing.
    (7) a solar trough using a parabolic reflector focused onto a pipe
    (8) a windmill/shaft powered chiller using ammonia working fluid with Hg liquid piston
    (9) a solar collector powered chiller using the ammonia-water cycle

    By all means add to the list. You'd be the first person I would refer him to.

    I'm assuming his service experience includes safety training and a sober view of risk mitigation. If he has such a tower, or can get one for a song, one of his first steps would be to get professional advice about the design limitations, to protect against tower collapse, as well as any lightning protection and, preferably, a way to retract the blades and string up guys when the weather gets iffy, perhaps even to drop the payload altogether.

    Thanks. Yeah, I'm strictly limiting my remarks to that scenario.

    Agreed. That's the tough question which needs the requirements to take shape before anyone can speculate as to the design of a practical system.

    All I had in mind when I said that was that they might heat some water in the solar collector and use it to do something useful, such as to prepare a warm meal.

    This is what will get them closer to calculating their actual power needs. There might be some tradeoffs they'd be willing to make, like doing away with an air conditioner and just staying under a fan when it gets uncomfortable.


    I had some more thoughts on this on par with some of the others.

    #10. It may be possible to address energy storage in electrovoltaic cells without going through the electricity generating stage. That is, whereas the storage battery converts electricity into chemical energy while charging, and then converts the stored chemical energy back into electricity during discharge, the DIYer may find an application for using the chemical energy directly. The first thing that comes to mind is hydrogen gas from water, although there might be some advantage to using it to separate metals, and then maybe burning them for heat, or something along those lines.

    You can generate hydrogen gas directly from water by passing a DC current through it. If you can devise a means to safely contain the gas and burn it, you may be benefit from this to some degree. [Note, hydrogen gas is highly explosive. Initially work with no more than a test tube full to avoid hazard.] As a project for Mr Q, I suggest he try this simple experiment. Obtain some pharmaceutical grade saline solution, a lantern battery, two pieces of hookup wire and a lid from a jar. Fill the lid with saline. Form one of the wires so it lies in the bottom of the lid while attached to the battery. Form the second wire so that it dips into the saline while attached to the second battery terminal. Place it as such and wait a while. Soapy bubbles of hydrogen and oxygen gas will form. Spark the second wire to the first, and the foam will ignite and burn gently before dissipating. With some creative enhancements, I think you will see that this can be done on a larger scale to produce usable light and heat. Ideally you would have no intermediate products of electrolysis and combustion - just pure hot water as the result. As a side note, you can generate chlorine this way, and with a little more work I think you could produce small amounts of disinfectant/cleaning solution, assuming you have salt to start with (this may be more applicable to people living in marine environments). BTW, tell me at what stage you think I'm putting you back in the cave.

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    #11. This is a variation on (7). You may be able to use your light bulbs as sources of heat to generate warm water. You can try this with a low voltage lamp, like a car headlamp. Place the lamp in a clear dish and fill it partially with water. Connect the lamp to a 12V supply. Place a thermometer in the water and observe any heating. You can imagine that, with the lens facing down, the dish may be oriented like a ceiling fixture, so that it projects plenty of light while warming the water. It would take some additional creative steps to apply this, but it might be a suitable temperature for washing hands/face or some small article of clothing. A variation on this might be a table lamp, say a large clear glass bottle or vase. You might experiment with ways to orient the bulb to get adequate light. I think you can expect to produce several liters of warm water. Each Joule of heat raises a gram of water one degree C. If you were using a 30W bulb (30 Joules per second), and all of it went to heat, then for every second the light was on you would be raising 1g of the water 30 degrees (or 30g of water 1 degree). After burning the lamp for an hour, you could expect to get several kilograms (a few liters) of warm water, depending on how much energy is lost in the process. Obviously you would want to treat the connections with a durable sealant. But the energy conscious person might imagine using the lamp for an hour or so and then taking advantage of the warm water for some light washing.
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  3. quinnsong Valued Senior Member

    Exactly right in your speculation. I emailed him a couple of days ago and next time we skype if he has the time to go over the ideas he will give me some input or have some questions (if and that is a big if because he had a mission ) on the technical aspects of your suggestions. Unfortunately, I would not even know what questions to ask regarding anything mechanical, well maybe cars but that is it. This is a perfect way for him to escape at the end of the day, he was very excited when I told him I would be emailing these posts, so thanks again to all for your input!

    I will be sure to post any comments or questions Mr. Quinn has.
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  5. Aqueous Id flat Earth skeptic Valued Senior Member

    Hey that's great. I'll certainly stay tuned. There's already a quality to this discussion which is just remarkable -- the back story of what's unfolding in his life, and the possibility that this conversation could extend to some ungodly theater of operations where he's got a lot more on his mind, and even strike a chord in him at all -- when you put it all together (even without any knowledge of the specifics) -- it makes this a remarkable little discussion we're having. I certainly wish him the best of luck and a safe and speedy return.
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  7. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    speaking of car generators, I bet they will function as motor too at least one of the two types (DC or AC) if not both.
    If true then there is a simple wind generated energy source that could be considered. (Still on a tall guy-wire supported pole is best as I dicussed in prior post.)

    The vertical shaft wind turbine is slightly more efficient than the horizontal shaft one and of course needs no tail for "turning into the wind." It will however not self start even in a strong wind.* Thus some times also on the shaft is set of three hemispheric cups, like often found on wind speed gages. That would not be needed if energy from battery started the DC generator / motor and were used for water heating (No need for inverters or making 60Hz as I discussed in prior post.)

    Prior post =

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    Vertical shaft can go down to motor/ generator at base for less weight to lift up. Taller with guy wires would produce more energy.
    As blades have constant cross section you can make them too - any reasonable wing like air foil cross section will do (curved side out). Might be best to make them of bent plastic or wood, not metal, if you have weak TV signal as they will modulate it if metal.

    * The near ground one of photo might self start as has more gusty / turbulent wind.

    PS cheapest "long shaft" may be a few section of iron water pipe. (Central part of a solid rod is nearly useless added weight and cost). Make sure the torque on it tends to tighten the coupling joints. (One may need to be welded to pipe if has same thread "handedness") I.e. mount two blades so it turns in correct direction for that. (The more blunt, leading edge of the wing airfoil will advance, I'm almost sure.) Possibly "inch pipe" (or even less?) Turning inside 4 inch pipe guyed at each join is the cheapest way to go. That pipe /post of the photo looks more costly as is that torque resisting concrete base. I would make much smaller base probably with several inch conical depression in the center, but initially for pull up, it would have a deep "ash tray" like notch in it holding the pole so it hit the greased far side of conical depression and slides down into the pit of the base.

    I'll let you work out how to best mount the motor / generator, in the base, but note that "Pipe reducers" do exist and several could fit motor/generator inside the last largest one. Don't forget it rains. I. e. the bottom of the "pole pit" needs to drain water. One solution is that bottom is above ground level inside an inverted larger concrete cone or a metal "tripod". That would still require much less concrete than the torque resisting base of the photo.

    Alternatively the motor/ generator could be in the open air under a small "table" which the "4 inch" pipe screws into with the internal pipe passing thru to join the motor /generator shaft.

    You should find this link interesting:
    Last edited by a moderator: Mar 7, 2014
  8. Trippy ALEA IACTA EST Staff Member

    I've been tinkering with a couple of ideas myself, and had a range of ideas on a variety of scales.

    1. I want to modify our house so that it has a central heating unit that operates using a system that stores the energy it extracts from the house during the summer underground then extracts that heat and moves it back into the house during the winter. I would also set it up so that it maintains a constant relative humidity (at a comfortable, setable level), and changes the air in the house, drawing fresh air from the outside which is warmed using a heat exchanger.

    2. I want to buy a vespa, strip it of its motor and petrol related paraphenalia, fit it with an electric motor and batteries, set up a solar charging station at home, and give it the capability of trickle charging itself during the day using solar panels built into it (as well as regeneragtive braking).

    3. Mrs Trippy and myself live at the end of a leg-in, we have a 50m path between us and the road and it gets very dark at night. I want to set up a solar charged, lead-acid powered LED lighting system to fix that problem, and to illuminate the street number on our letterbox and the instructions on the side of it.

    And this is a sample of the projects I have banging around in my head that are somewhat relevant to the thread.
  9. Trippy ALEA IACTA EST Staff Member

    This reminds me of another idea I have had - although, I'm not sure how well it would work. I want to build a glasshouse for growing tomatoes, however, I want to set it up with a solar panel, some batteries, and a heating bed so that I can have tomatoes year round.
  10. billvon Valued Senior Member

    Solar electric power to battery to electric heat is incredibly expensive and really not at all practical - especially since you can just store the heat.

    Before you consider that, I'd run the numbers and figure out how much (for example) water you need. To store heat from day to night you need hundreds of gallons of water for a typical home. Based on that you'd be looking at tens of thousands to hundreds of thousands of gallons of water in an insulated storage tank. It might not be cost effective to store a million pounds of water.

    Solar charging station would work well, but I'd caution against putting solar on a scooter. The available area is small and solar is somewhat fragile. I've done this on a 1kW electric bike and it didn't work well for several reasons.
  11. Trippy ALEA IACTA EST Staff Member

    Stirling Engine
  12. Trippy ALEA IACTA EST Staff Member

    Yeah, but storing the heat can be problematic, can it not?

    I know - this is one of the reasons why I've only ever toyed with the idea, I've neevr been able to think of a useful working fluid for storing the heat - the closest I've come so far is storing it in the ground itself, which to some extent kinda negates the point because you're effectively just using a heat pump, and the alternatives I've come up with, for example, using ceiling space as a heat source, well, you may as well jjust use the heat source directly.

    This is one of the debates I've had mulling over and over in my head. The flip side of the fragility issue is that there is a supplied in the town I live in that sells solar panels which are designed to withstand being walked on with the intention that you can fit them on the flat surfaces on a yacht. The main advantage I can see in the on-board charging is that I would effectively be using the scooter for say 20 minutes a day (commuting to and from work), and then it's left essentially unused for 8.5 hours, and I figured 'why not find a way to have it trickle charge off solar panels during that time'. Of course, my original plan was to convert a car... >_>
  13. Trippy ALEA IACTA EST Staff Member

    My original plan was this:

    I live in the southern hemisphere. Find a north facing location to build my greenhouse (it's not a huge thing, you understand).

    First step is build the back wall. The original plan had been to build a back wall with a high thermal mass - say, build it out of concrete blocks, and fill the hollows with something of a high thermal mass.
    Paint the north facing side of the back wall black, the south facing side white, and put some insulation on the south facing side.

    Set up a well insulated hot water cylinder, and a solar heating system for the water. Thermally isolate the base of the greenhouse from the surrounding soil.

    The first question, of course, is whether or not this would give me any additional growing days, and how many given that I live just south of the 45th paralell (somewhere around 46° south IIRC).
  14. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Hard to do on single house scale and in many areas illegal to inject water into the ground, without complex approvals.

    I led a DoE supported project with help of 4 others at APL/JHU at least 35 years ago call CASES, Community Annual Energy Storage System, CASES. I googled to see if there was anything on it and discovered this: I had forgotten I wrote summary on it for Environment

    Basic system used water source heat pumps in homes that ran in part on the heat removed from large buildings. Thru out community there are cool and warm water circulation pipes. Even in winter larger buildings produce surplus heat that is often just dumped with cold air intake. The cold water these small heat pumps eject is used instead to cool the building that is as you are thinking is aided by outside air for ventilation only. Also there are large ice machines (rotating drum with thin ice scraped off so very efficient compared to ice machine making block as essentially no thermal gradients in thin ice.) They supply any heat needed that can not be recovered from the large building. This ice is stored for summer cooling, mainly of the bigger buildings.* The computer model running on real hourly weather data got COP annual average of about 8 or even 10 if community was "perfectly balance" thermally on an annual basis.

    * Where suitable aquifer exist and approval can be obtained for injection (and take out, but that is usually easy) it can be main storages instead of ice filled insulated "Quonset huts." One thing working against single home scale is aquifer water does flow / move - what you put down will be else where 6 month later. Another is that the volume you would use will basically be so small that months of thermal contact will bring it nearly into thermal equilibrium with the dirt. You can not store "winter cold" on that scale for summer use or summer heat for winter heating via water source heat pumps, but they are much more efficient for heating than air source heat pumps even with just existing ground water temperatures. Usually, to avoid the legal problems, ground heat but not ground water is used via pipe loops at least a yard down in the earth.
  15. Trippy ALEA IACTA EST Staff Member

    Yes, I had worked that out for myself, thankyou.

    I have a... working knowledge of environmental law in my jurisdiction... I wasn't talking about injecting water into the ground
  16. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    You had said: "a central heating unit that operates using a system that stores the energy it extracts from the house during the summer underground then extracts that heat and moves it back into the house during the winter. " And I miss-understood that, but it does give me an idea you may want to look at:

    If one is building a new house, well insulated, and estimates the total summer heat removal requirements and converts that in melting ice and warming the ice water say to 20C (78F) you get 80 + 20 = 100 calories of cooling per gram of ice stored in an '"ice basement." House needs a foundation anyway and many do have a concrete floor so main cost would be the ice machine (a heat pump)* making heat for house in winter much more efficiently than an air source heat pump pulling calories out of sub freezing air.

    I don't know how small an efficient rotating drum dipping into 0C water exist commercially. The ones in the CASES design had drums of about four foot diameter as I remember. As the heat is pulled thru less than 1mm of ice before being scraped off, the drum's internal Freon temperature is not much below 0C so that design is much more efficient than one making big blocks of ice where the Freon must be much colder (due to thermal gradient in the thicker ice). If the ice basement volume is not too large, this system might pay back the extra cost in less than 5 or so years.

    The house would have a small room on the ground floor holding the ice machine with the ice just falling into the "ice basement." The ground floor (wood?) would have insulation on the lower side so little heat provided by the ice machine returns to the ice basement in winter. Quite possibly all one would need to do for summer cooling is have thermostat controlled a fan in that "small ice machine room," moving the cold air above the stored ice up into the top occupied level of house (typically bed rooms).

    What do you think? Interesting enough idea to put some numbers in and evaluate the cost effectiveness (pay back period)?

    * Few think of an ice machine as a "water source" heat pump, but that is what they are. The rotating metal drum type is much more efficient heat source than the air source heat pumps commonly used and has only the simple drum as the sole cold heat exchanger and the radiator or hot air ducts etc. in the house that are needed any way, not the two heat exchangers of the air source with finned copper tubing. In volume production for home size they would be significantly less costly to make and as the Freon needs to be only a few degrees below 0C (Not colder than the winter air at night.). So are much more efficient to operate too.
    Last edited by a moderator: Mar 8, 2014
  17. Trippy ALEA IACTA EST Staff Member

    Correct. I've had two ideas floating around in my head, either using a UST to store some working fluid for holding the heat - and I considered several options for this, including variations on the ice machine you mentioned., or using the thermal mass of the ground directly. Each has its own unique difficulties.

    At this point, primarily, I think that I do not have the capital to invest in ideas such as this, and that clearly I still have much to think about.
  18. Aqueous Id flat Earth skeptic Valued Senior Member

    In my mind the closest thing to what you are suggesting is to modify and existing air conditioning system (or one you put together from components) such that the condenser is not cooled at the relatively warm temperature of the ambient air, but rather at the substantially cooler temperature of the underground. The simplest way to do this is simply to circulate water through a geothermal well and run it across the condenser coils, the way folks will sometimes do with tap water. The drawback is evaporation, plus preventing algae to grow on the coils -- and without introducing a pH that will harm the material used in the geothermal well. The goal here is to reduce the work required by the compressor, perhaps cutting it by 50% or more. Another more design intensive step is to eliminate the compressor altogether. For example you might be able to make the ammonia-water cycle work well in this application. In this case you'd be reducing the work required for a pump to pressurize aqueous ammonia after the hygroscopic absorption stage of the process.

    There may be a feasible way to reverse the process, that is, to "chill" the underground such that waste heat dumps across the indoor evaporator. This is kind of tricky esp. if the underground temp and the indoor temp are even closer than they were in the summer. BTUs are the big design hurdle. That underground sink needs a very large surface area, more so when the temp differential is small.

    It also comes to mind that ammonia changes phase at around the freezing point of water which means you can pick some uncomfortably cold temperature, and set the minimum operating pressure such that that's your liquid phase, and benefit from the fairly large expansion as it vaporizes, with only some relatively small change in temp. I think RussWaters could offer some expertise with this, and probably Origin & Exchem. And I'm sure you could expound on this better than me. In fact just by adjusting the nominal pressure you can, I think, adapt an ammonia based system, without water or before it is reabsorbed, to give you that phase change advantage over a relatively small change in temp - pressures which I think are not too hard to achieve -- and in this way adapt a heat engine that works in the summer to work year 'round. If the ground is the reference (whether sink or source) then the only time you're dead is when the weather is really pleasant. I think this means you could use it to develop useful power during temp. extremes, besides aiding in heating/cooling the home.

    Yeah I think the regenerative braking is a windfall with a motor. Collecting it is a little tricky though since effective use of it requires moving many moles of electrode material over the relatively short intervals of braking. In the alternative you need a dummy load to draw it off as waste heat, and/or conventional brakes, to balance safety against economy. The other thing to consider is some radical battery technology which best works this way. There's a good project in and of itself. The world needs a good nickel battery. (As in 5 cents).

    Solar panels built into the car? I wonder. Remember that catamaran which was outfitted with solar cells a couple of years ago? I wonder if a long lightweight section of a vehicle could be employed to get the surface area that might make that worthwhile. I can't think of how to do it other than maybe two "trucks" -- back and front halves of the vehicle, with the long, lightweight span in the middle, aluminum maybe?, just able to hold up the panels. The point there is that you need ballast to stay on the road (hence a rear truck), but you can't afford the weight of a school bus in the middle span. But you need that surface area. Still you'd be producing only hundreds of watts of power, in peak daylight, which pales in comparison to the approx. 13 MJ in one gallon of gas. That's at least taking into consideration the efficiency of the solar cells. Another way to approach this is to see if you can estimate how many Joules it takes to get somewhere, and what percentage of that would be available from solar cells once you figure out how many square meters you can afford to carry. Finally you need to point them all in the same direction. Not at all impossible, but more difficult unless you start with a planar surface -- something that suggests an airplane wing. And now ou have wind loading to consider, which might be overcome with a plastic bubble of some kind, perhaps even a relatively light but uncannily sturdy ellipsoidal geodesic dome could achieve that. It wouldn't look like a Vespa anymore - a cross between a mobile hot house and a wiener wagon maybe. Otherwise you could try to conform the solar cells to the contours of the body and just deduct the number of cells on average that don't receive the light orthogonally.

    The first thing that comes to mind is that you can save a heck of a lot of energy by flashing the lights, esp. as low duty cycle. In any case as you know already know you can save power by having them come on continuously when you walk by. I've used the infrared sensors too for that with the higher power floodlights. That was when I discovered how many nocturnal animals I had. I would swear they all started to come over to my place just to play with my lights. I ended up switching to the low wattage lights we call Malibu lights, around the pool and places where it's easy to trip over tree roots in the dark. I just put them on a timer. They don't blind you either and give the whole place a cozy feel at night. You can either bury high voltage lines or just suffer some loss from running low voltage lines in which case you can thread them through an existing irrigation line -- or add them while you're installing one. The point there is that there is no shock or fire hazard with putting the low voltage cable under water.

    Oh I think it's dead on. For most folks heating and cooling the castle is where most of the utility outlay goes. Addressing that needs to come first in any well considered plan such as the quinnsongs of the world might be contemplating. I think a lot of this ties in neatly with your expertise. If I'm not mistaken, you'd be best qualified here to comment on geothermal wells and related subjects.

    I throw out one last train of thought for you and then give it a rest. I have it mind that the Hg liquid piston can be employed with a refrigerant like ammonia to work as an engine. For example, the piston might push a ferrous magnet (not sure what alloys could hold up to the Hg, but they could perhaps be coated, maybe with Teflon) and the magnet could be pushed through a coil in the manner of a linear generator. It would need to stroke which takes some design. Another idea was to employ this with hydraulic fluid on the load side, such that it could directly push a hydraulic system of any design. That's about the lowest friction method I can conceive of for converting heat into useful work. No moving parts (per stroke anyway) either. High reliability, probably even with no maintenance to speak of. The energy yield is low, which can be addressed by making it highly parallel, but that's limited by the high cost of Hg. The next question is whether the Hg can be dispensed with altogether -- whether a column of ammonia can push a column of hydraulic fluid directly, and whether there's any cross contamination/corrosion to worry about. I still think this has a reasonable feasibility to it, all things considered. Even the ammonia hazard can be mitigated by sealing the system and placing it underwater such that it's virtually impossible for any substantial vapor to escape. Plus it's a natural chemical -- at worst if you spill aqueous ammonia in moderate amounts you just fertilize the ground. And it's cheap enough and widely available.
  19. Trippy ALEA IACTA EST Staff Member

    This is kinda what I had in mind, but I wasn't thinking of a geothermal well, I was thinking more of a UST and a heat pump. The main advantage I saw in a UST was in the that you could effectively use the thermal mass of the ground to provide insulation. And now that I think about it, I have an inkling I may have seen something similar on Grand Design or a

    The basic idea, I suppose, is that the working fluid keeps the compressor cool, which in turn keeps the house cool.

    Hmmm. Good points.

    Well, I was thinking that regenerative braking isn't universally applicable, in that it's not going to stop you in case of an emergency, as far as getting it into the brakes goes, I was thinking maybe store it in a capacitor, then trickle charge from the capacitor to the battery. I have done some research on regenerative braking, but that's the best scheme i've come up with. There again, it depends on the circumstances - stop start driving versus driving down a hill.

    I'm not expecting the battery to be fully charged by the end of the day, at most I'm hoping to reduce the load on the home station.

    That was the general plan, yeah. Remote control or PIR on a ten minute timer for the letterbox, normally open magnetic reed switch and a ten minute timer for the path lights. Either that or a flip-flop and two reed switches so that opening one gate turns them on, and opening the second turns them off.

    Alternatively, as far as the letterbox goes, I was only considering using, say, half a dozen LEDs to provide backlighting.

    Flatterer. I don't now if I would go that far, but i'll try and contribute where I can.

    Alternatively, Mercury may not be ferromagnetic, but it doesn't have to be to have an electric current induced in it.
  20. quinnsong Valued Senior Member

    No Mercury or Ammonia

    The Mister has had very little time to go over the posts of the thread i emailed him but he had a few comments on what he has been able to read. He is much more interested in the solar, wind and water ideas than any chemicals such as ammonia or mercury:. He recalled to me when the Navy had a spill of just a marble-sized mercury spill and the ensuing cleanup, so he has an aversion to using chemicals it seems.

    He did give me a brief summary of his drawing and idea-[2:07:19 PM] It is a system that utilizes a low draw electric motor pumping water up into a vertically standing pipe that routes the then falling water to a water wheel turning a generator. the motor will be a low draw e-motor because it will be solar powered. I did ask where the water would be coming from if we did not live near a stream and he said a water basin. He also mentioned something about an Archimedic spiral and then I was lost

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    , so did a search and found this on that wiki:
    Now I completely understand.

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  21. Trippy ALEA IACTA EST Staff Member

    This sounds remarkebly similar to another idea I had that kinda arose out of discussions on this forum.

    The problem with wind and solar is matching peak loading with peak generation, you need some way of storing the extra energy during peak generation for peak loading. One approach is batteries. Another approach is to use an elevated reservoir of water. The basic idea is you have two reservoirs, an upper and a lower. When generation exceeds demand, water is pumped from the lower to the upper and the energy is stored as GPE. When demand exceeds generation, water is allowed to flow from the upper back to the lower to power a turbine.
  22. Aqueous Id flat Earth skeptic Valued Senior Member

    Understandable. Ok we can scratch that off.

    Also see'_screw

    It sounds to me like he's thinking of doing this to store the energy of the solar panels, as an alternative to needing batteries as Trippy said. As he mentioned, this can be done by pumping vast amounts of water uphill and the letting it run back through the water wheel as needed.

    The microhydroturbine billvon mentioned very early in the thread is an excellent example of a water wheel, and it's ready-made and tested. Here I'll show how you might estimate how much water might be involved.

    Let's say you are operating a medium sized solar array. Just to get this rolling, lets say it covers 10 sq meters. It will intercept no more about 10kW of sunlight. About 75% of that sunlight is lost in the glassy material of the photocell, never to convert to electricity. That leaves you with 2.5 kW of power in the middle of a clear summer day with your panels directly facing the sun.
    Let's say that for one hour you folks are out of the house doing something else. Nothing is turned on, so you want to capture 2.5 kilowatt-hours of energy and store it as a column of water.

    1 Watt of power is 1 Newton of force exerted over 1 meter per second. The question is: how much water exerts a force (its weight due to gravity) of 1 Newton? That's the amount of water which, when lifted 1 meter in one second, burns 1 Watt of power. And that's the amount of water which, if the water wheel was perfectly efficient, would give back 1 Watt of power when you open the valve and let it flow through the water wheel sometime later.

    The answer is 1/9.8 kg of water. This is because the force due to gravity is F = mg, where m is the mass of the water in kilograms and g is the gravitational acceleration, 9.8 m/s[sup]2[/sup]. Let's call this 1/10 of a kg of water. Water weighs 1 kg per liter. Therefore you need 1/10 of a liter (102 mL actually) which turns out to be about 3.4 fl oz. Thus for every 3.4 fl oz you raise one meter you burn one Watt, and you generate one Watt of electricity in a perfect water wheel attached to a perfect generator in which 3.3 fl oz runs back through it over a span of one meter.

    We need to store 2500 Watt-hours from the solar panel. Therefore we need to store 255 L of water = 8626 fl oz = 67.4 gallons. That's per second. In one minute we need to move 4043 gallons. That's about eight times the water flow of a red-capped fire hydrant (500 gpm) and more than twice the flow of a blue capped fireplug (1500 gpm). In one hour this will fill a pond with nearly a 918,367 liters of water, which is 242,607 gallons. 918,367 liters occupies 918 cubic meters which, as it turns out, is enough to put one acre of land under about 9" of water. It would fill a 57'x 57' x 10' deep pond.

    In return, when you ran that water back through the perfect, lossless water wheel you would get back 2.5 kWh, which is enough to run one 100W light bulb for 25 hours. If you factor in the losses at the pump and water wheels (say they each operate at 80%, plus the losses in the pipe) . . . you should expect to get a little more than half than much power back, maybe enough to run one 100W bulb about 14 hours or so.

    In all of this we only raised the water one meter. If we raised it 10 meters then the amount of water volume drops 10 times to 92,837 liters or 24,261 gallons which fills a 57' x 57' pond which is 1' foot deep. I'm assuming as I say this that all of the energy needed to raise the water higher is equally recoverable; that the water wheel output for the 10 meter high pond is 10 times the electric power output for the one meter high pond. There is some additional design needed to work that out.
  23. quinnsong Valued Senior Member


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