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EDIT: Thanks to everybody for replies and comments, which have been most useful. It seems that the hydro side of the equation would be challenging to implement, given the issues with sufficient head, protection of the generating apparatus and so on. I will look again at the possibility of solar and take it from there.

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I am trying to assess the feasibility of using a micro-hydro setup to charge a car battery.

The application is that of a simple time-lapse camera that would monitor a shallow water crossing on a stream.

The problem is that there's no mains electricity anywhere nearby the water crossing where the camera would be situated so it would need a standalone power supply of some kind. The location is in dense woodland and I envisage the camera sitting there all year, so powering it with solar power under leaf cover and in this latitude (the UK) would presumably be tricky.

However, there is the stream, right there. Although small, this runs strongly and reliably all year round. I am wondering if I can hook up a 12V car battery to a small micro-hydro generator like this to trickle-charge the battery and use the battery to run the camera platform. It would probably require something like 5volt and 1.5 amps.

I know something about electronics in the abstract (I know what capacitors are, where roughly they are used, why you'd use an MLCC in preference to an Al etc). On the other hand I have no real technical knowledge, or circuit design know-how, so this would be quite a challenge and probably take me a long time. I'd be more than ready to give it a shot, provided I had some certainty that it is feasible.

Can this be done without wizard-levels of electronics ability? Any opinions or pointers welcome.

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closed as primarily opinion-based by Daniel Grillo, Dave Tweed Jan 12 at 17:35

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.If this question can be reworded to fit the rules in the help center, please edit the question.

    
I'm reminded of an ant trying to push a watermelon up hill. A Car Battery is way to big to properly charge with something like that. That said, I doubt your camera will use 7.5W. Even if it does, your looking for a LiPo battery solution, like a usb power pack or laptop battery pack. That would work better. – Passerby Jan 10 at 20:54
    
Try reading this trailcampro.com/batteryconsumptiontest.aspx – Passerby Jan 10 at 20:58
    
One of the big challenges for small hydroelectric installations is keeping the intake water clean. There's all sorts of garbage that floats down streams in the wild. Leaves, small critters, rocks, algae, etc... could fairly easily clog your little turbine. – Connor Wolf Jan 10 at 22:38
    
Power is flow x head. That generator looks absolutely tiny, it's going to need several metres of head to generate any power at all. A quick calculation 1litre/s = 1kg/s. Acceleration due to gravity 9.8m/s^2 Assume head of 1m: 1m x 1kg x 9.8m/s^2 = 9.8W. But that thing doesn't look like it can handle 1 litre /s. You'd be lucky to get 0.1L/s through it, which means at least 10m of head to get an output of a few watts. If your stream is flat and you have no way of creating a static head, you'll have to rely on velocity head with something like an open bladed propellor to catch enough flow. – Level River St Jan 11 at 2:40

If there's enough continuous water flow to charge a battery to power a camera then there's enough to power the camera directly. No need for a battery - just a voltage regulator.

The usual thing most people don't appreciate is that hydroelectric generators need head (height difference between inflow and outlet) to generate enough driving pressure to overcome the resistance of the generator.

Measure how much head is available and what is a reasonable pipe size you could install at that location. You will find plenty of information on the web to calculate what power you could extract with those parameters. When you have the information you can add them to your question and we can improve the answers.

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It's usually advisable to have some storage of electrical energy to cope with output fluctuations, but a large enough capacitor might do. – pjc50 Jan 10 at 21:34
    
Not if supply always exceeds demand which is a possibility in this case. In most cases the electrical grid runs without storage (as storage is difficult on an AC system). Adding a battery in this case complicates matters quite a bit and the OP is looking for simple solution. – transistor Jan 10 at 21:37
    
A fair suggestion. However, there are seasonal factors in play here. Specifically, we get most rain in the winter, so summer flow will tell the a different story. Also, the UK is currently (and rather inconveniently) suffering from record-breaking rainfall and the stream is in a state of semi-permanent spate. Still, I shall go and make inquiries. – SlowLearner Jan 10 at 22:09
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@SlowLearner a battery is good for solar as it gets you through the night. I imagine the flow of your stream is constant for days at a time. Therefore to be of benefit, a battery would have to be suitable for several days or weeks of charge, which may mean it has to be quite large, which may mean the charge leaks away with a significant current... I think the no-battery option would be appropriate if you choose hydro power. – Level River St Jan 11 at 2:32
    
@SlowLearner The only real way to store the energies you would require for the length of time required (seasonal), is to pump water up to a reservoir and use hydro-electric to regenerate the power. Somehow I find the idea of using hydro-electric to pump water up stream a little redundant. – Aron Jan 11 at 2:35

I agree with Mr. Cowie that solar is probably your best bet, not to mention the most easily installed in a remote location and the system components are easily sourced with appropriate capacities - panels, charge controllers and batteries.

I am guessing that the 7.5W you mention is derived from maximum ratings- the first thing to do would be to measure the actual power consumption and use that (with an added safety margin) as your baseline.

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The feasibility of using a micro-hydro setup is mostly a hydraulic problem rather than an electrical problem. To get the head to drive a turbine like the one you proposed, you would need to dam the stream. You also need the create an inlet and piping to route the water to the turbine. The inlet needs a system to keep the piping and turbine from getting clogged by material in the steam.

There is such a thing as a run-of-river paddle wheel of some sort, but you need to keep that clear of tree branches etc. floating in the stream. The following link provides a lot of information about micro-hydro systems. In the comments of the article someone states; "to my knowledge, there are no viable run-of-river turbines out there." The context there is micro-hydro. I believe that run-of-river systems have been used for large systems. HomePower Link

I think you need to look harder at solar power. With batteries that are better matched to your load, that might work even with your low insolation level

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