Small scale hydropower scheme's.

[drinksloe]

Good post ccharlie.

 

Just wondering is the 100kw a direct replacement for the older 4kw? ie usiing same pipes and pump house and just bolting a larger turbine onto it.

Or was it a complete new build new pipe work etc?

[openspaceman]

That's scheme I've been involved in! I'm responsible for all the tree management around the development and unfortunately was responsible for felling all the trees that had to go! [ATTACH]197630[/ATTACH][ATTACH]197631[/ATTACH]

 

I'm fascinated by water power, we have a decent stream with a weir at work but the fall across the site is only about 3 ft and being in a clay area the runoof happens fast after rain and then the stream slows to a trickle, though it never dries up.

 

I had thought about Archimedes screws like that but as run of the river and being fish friendly rather than that configuration.

 

Do you know what advantage those screws have over a reaction turbine?

[ccharlie]

Good post ccharlie.

 

Just wondering is the 100kw a direct replacement for the older 4kw? ie usiing same pipes and pump house and just bolting a larger turbine onto it.

Or was it a complete new build new pipe work etc?

Interesting question. They considered upgrading the 25kW unit; however, it lies at the end of a 1/2 mile long millstream, which loads of salmon and other fish were getting trapped in. Their was a large mesh screen above the entry pipe to the turbine, which stopped them swimming down and being shredded to pieces! This mesh worked was attached to a very simple and very clever rotavator that moved clogged bits of mesh down and round, with the water pushing the dirt away and downstream. Very pleasing simplicity.

 

The Environment Agency was very keen for a new system to be installed, which would address the fish issue. So they did so, reworking a weir/salmon run at the same time. The new 100kW system is an Archimedes screw. This was selected so that fish could safely swim down the whole length of the screw during operation and be ok. I think that the maximum fish length is 5', which you don't see many of these days! The turbine has a maximum rotation speed of 2 metres per second, which is apparently fine for a fish to go down.

 

I've been in touch with the EA about the damage caused to fish by hydropower units. Out of all the hydropower schemes that have been set up in the UK there are only three recorded instances of fish being harmed (which totals about 30 fish in total). i.e. they are very safe for fish.

 

So... the old scheme is still in a shed just down from the house. The new scheme is up near to the river and the salmon run. The new scheme is run by a local coop and they pay us a rent for the use of the land and a proportion of their income, which is handy as we've got loads of dilapidated buildings to sort out!

 

Things to ask when looking into a new scheme:

1. What is the head available? We've got four metres or so, so very much a low head system.

2. What volume of water is available?

3. Are there any planning or ecological restrictions?

4. Do you have access to an electrical connection that can handle your output (not a problem if you'll use it all on site)?

5. Can you design a system so that at the end of the Feed-in-Tariff period you can either afford to carry on running it or easily remove the system?

[ccharlie]

Do you know what advantage those screws have over a reaction turbine?

For me it is primarily the fish question and not from the fish point-of-view (although I greatly approve of them not being harmed by new schemes). The fish question relates more to what you have to have in place on traditional schemes to stop them being harmed. Here there was an 8 foot by 4 foot wire mesh on rollers that would automatically rotate all day and night as required. It would break and quickly the debris in the stream would clog the mesh and stop an adequate flow of water reaching the old turbine. This would then automatically shut down until the mesh was cleaned.

 

Sometimes people have to install smolt screens, which have similar problems.

 

Anything that can be done to a system's design to limit any form of blockage is going to easily pay for itself over the 20 year period.

 

One downside that people very, very rarely mention is the noise. On a still day our 100kW system can be heard from at least 500 metres away. It's not a bad noise as such but very much there...

 

Archimedes screws are also a more basic technology that are supposedly easier to fix; however, from personal experience, it is almost impossible to find someone in the UK who is acceptable to an insurance company to weld a three foot piece of steel back onto the bottom of such a screw! (They had to send two guys over from Germany to do so...).

[openspaceman]

IThe turbine has a maximum rotation speed of 2 metres per second, which is apparently fine for a fish to go down.

 

How many RPM is that, must be some torque compared with a turbine.

 

What's the comparable conversion efficiency?

 

Can they swim up it?

 

I think you said 3m fall but the screw is how long?

[tomlt]

If you've got low head but reasonably high flow then by far your best solution is a crossflow device, forget Pelton wheels unless youve got a decent (10m plus head). Cross flows can be installed with 2-3m head and rely more on volume of water than pressure. As part of a university study i once surveyed a park in Bury nr Manchester for similar such devices to recommend micro schemes at 4 locations ( upto 100kw). Looking at the photos o would estimate you could get a 10kw device out of that easily, but you do need to account for the minimum flow during summer or b e resigned to switching it off.

 

Have a look at Gilkes pumps, they make turbines and iirc their website had lots of useful info.

 

 

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