Viability of hydroelectricity

mrmmhf · 14 September 2019 at 8:13AM

We have a pond (about a quarter of an acre in size) that gets fed from numerous small streams and subterraneous sources, and the water feed is decent from autumn to spring especially when we get lots of rain. At the bottom of the pond, there is an overflow that has been concreted and this allow excess water to spill over into another stream that takes the water down the valley. This overflow gushes from autumn to spring.

Based on this, I was wondering whether hydroelectric would be an option - it would obviously be on a very small (micro) scale, but was wondering whether we could generate 1-2kW (24/7) to help the ASHP over the winter months when the days are shorter and the solar PV isn't operating at maximum levels.

Was wondering what an installation like this would entail, and would be need inverters and other expensive kit?

Martyn1981 · 14 September 2019 at 8:32AM

Hiya, have you asked on Navitron yet, they used to sell low head micro hydro, I think 2m head. And the guys and girls will certainly have some ideas.

But, when you say

there is an overflow that has been concreted and this allow excess water to spill over into another stream that takes the water down the valley.

my first thought was how much of this is on your property, as if you could pipe in that water, then you'd get all the head, which would improve things and allow the use of a more 'normal' hydro device if the head is 5m+ (I think?)

Martyn1981 · 14 September 2019 at 8:38AM

Not a recommendation, but this name/site sprang to mind, and their site has a lot of info on micro hydro, from low head upwards, and a calculator to work out possible generation.

The site seems to suggest low head is 1-5m.

Reed_Richards · 14 September 2019 at 9:24AM

mrmmhf wrote: »

Was wondering what an installation like this would entail, and would be need inverters and other expensive kit?

The electricity you will generate will be AC, at some frequency. You will probably want to connect that to your existing inverter so the inverter sees the electricity as more solar panels. I say this because you need to match your power output to mains frequency and phase and are not allowed to feed power to the grid in the event of a grid power failure; your inverter performs both these functions. So you would need some sort of AC to DC inverter to convert the output from your hydro power generator to DC but if you do it that way I imagine the new inverter could be relatively dumb and unsophisticated.

Martyn1981 · 14 September 2019 at 12:31PM

Reed_Richards wrote: »

The electricity you will generate will be AC, at some frequency. You will probably want to connect that to your existing inverter so the inverter sees the electricity as more solar panels. I say this because you need to match your power output to mains frequency and phase and are not allowed to feed power to the grid in the event of a grid power failure; your inverter performs both these functions. So you would need some sort of AC to DC inverter to convert the output from your hydro power generator to DC but if you do it that way I imagine the new inverter could be relatively dumb and unsophisticated.

Psst, I think you might have gottent AC and DC voltage the wrong way round.

Reed_Richards · 14 September 2019 at 6:49PM

Martyn1981 wrote: »

Psst, I think you might have gottent AC and DC voltage the wrong way round.

No, I don't think so. Anything rotary will generate AC. But depending on the speed or rotation and the gearing it won't necessarily be AC at the 50 Hz mains frequency nor at 230 V so you can't mix it up with your mains electricity. One way of doing this is to convert the AC to DC and then use your existing inverter to convert it back at the correct frequency. I'm not sure if "Inverter" is the correct term for an AC to DC converter but I think it is.

Or did you just want an excuse to post the YouTube link?

Martyn1981 · 15 September 2019 at 8:32AM

Reed_Richards wrote: »

No, I don't think so. Anything rotary will generate AC. But depending on the speed or rotation and the gearing it won't necessarily be AC at the 50 Hz mains frequency nor at 230 V so you can't mix it up with your mains electricity. One way of doing this is to convert the AC to DC and then use your existing inverter to convert it back at the correct frequency. I'm not sure if "Inverter" is the correct term for an AC to DC converter but I think it is.

Or did you just want an excuse to post the YouTube link?

Any excuse for some AC/DC ....... I try to spread good culture whenever possible.

Regarding AC v's DC, I have to say that's news to me, but I know very little about leccy. I'm pretty sure hydro and wind use DC generators, and in the case of regen on BEV's that's also DC, and all are rotary?

No idea if they can share a PV inverter, I'd guess at needing their own, but again a guess based on the fact that wind inverters are different to PV inverters, but again, I've no idea how they differ.

Reed_Richards · 15 September 2019 at 10:00AM

Have a look at this https://www.siemens.co.uk/education/pool/whats-new/a4siemens-lessonv1.pdf Martyn.
But basically I am right, you would convert the output from a hydro generator to DC then back to AC to match it to the grid.

Martyn1981 · 15 September 2019 at 4:13PM

Reed_Richards wrote: »

Have a look at this https://www.siemens.co.uk/education/pool/whats-new/a4siemens-lessonv1.pdf Martyn.
But basically I am right, you would convert the output from a hydro generator to DC then back to AC to match it to the grid.

Thanks I didn't know that, but where am I going wrong then as I've never heard of an AC small wind or hydro turbine. Why do they always seem to be rated in DC?

Edit - possibly you've already explained, I'm being slow, today and they produce AC but output DC, is that why they are rated in DC? Or is it just the large WT's that produce AC?

markin · 15 September 2019 at 4:33PM

The First thing to work out is the head, flow and Power Calculations.

Wales 300w off grid system

https://www.youtube.com/watch?v=MUNMjdmGIPI&list=PLEZ2hvCDKUpEvvgEy_b5C6UnYNslaYcik

Viability of hydroelectricity

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