Hydro -How to...?

Annatar

I have started to look into micro Hydroelectricity generation for the home. however the flow n head does not look to be good enough to make this worthwhile.
Flow: 5L per sec
Head: 5m

I have started to consider some way of introducing a multiplier to this...
A dam basically.
I figure if I can get pressure from a dam, equivalent to what a Head of 25 - 30m's would give Im in good enough territory :- 1kW

Theoretical power (P) = Flow rate (Q) x Head (H) x Gravity (g) = 9.81 m/s2 )

Now the question, how big has the dam to be to generate the relevant pressure?

Lu Tze

Annatar wrote: »

Now the question, how big has the dam to be to generate the relevant pressure?

If you are looking for 25m head then you need Top water level on the dam of 25m above your generator.

Pressure head in metres is the same as difference in elevation

Annatar

Lu Tze wrote: »

If you are looking for 25m head then you need Top water level on the dam of 25m above your generator.

Pressure head in metres is the same as difference in elevation

Really??
Damn.... scuze the pun.
I figured say a 1 metre high, 3 metre wide by lets say 5 metres long would give ALOT of tonnage pressure....*


Ahhhh wait a moment, unless you are saying the water spills over the top of the dam turning the generator.
I was taking from near the bottom, and getting a tonne of water for every cubic metre behind it with the resultant pressure...

* then again Im not sure if the static pressure behind the dam is affected only by height... 1 x 3 x 5 would give 15 tonne of water. But if it is not positioned directly above the outlet...does it matter?

Annatar

Does a dam 1metre high, 5 metre wide and 3 metres long have the same pressure at the outlet as a 5 metre high, 1 metre wide 3 metre long dam.

Part of me says no, and yet.... the total amount of water restrained cannot be ignored.

I dunno

Lu Tze

It doesn't matter how much volume is behind it, the pressure head is the difference in elevation between the two points (normally).

I attached a quick sketch there (MS Paint, for all your engineering design needs!), the arrowed line showing the difference in elevation, and therefore pressure head in metres between the reservoir and the pipe at that point.

It does not matter what size the reservoir is in plan i.e. what volume of water is there, it is the difference in elevation that causes the pressure.

I hope this helps

Lightning McQue

Have you installed a micro-hydro turbo?

Lu Tze

Lightning McQue wrote: »

Have you installed a micro-hydro turbo?

Me?

No, i have no experience with them.

i was just trying to answer his question on pressure, from the basic hydraulics course i've done.

Annatar

Lu Tze wrote: »

It doesn't matter how much volume is behind it, the pressure head is the difference in elevation between the two points (normally).

I attached a quick sketch there (MS Paint, for all your engineering design needs!), the arrowed line showing the difference in elevation, and therefore pressure head in metres between the reservoir and the pipe at that point.

It does not matter what size the reservoir is in plan i.e. what volume of water is there, it is the difference in elevation that causes the pressure.

I hope this helps

Soooo..... for example any dam of 3 metre height, the pressure is the same regardless of width and "length"?

Somehow I expected it to have some impact on pressure


Hmmmm any other way to get more out of low flow? Some other multiplier for the equation?

Annatar

Just wondering if a 10 metre 8" pipe which is reduced to a 6" for another 10 metres gives any benefit over a straight 20 metre 8" feed pipe to a generator?

Increase in pressure with an inverse reduction in flow? Power gain... zilch???

Lu Tze

No not really-thats why we have been building water towers instead of reservoirs in low pressure area as there is no way to compensate other than booster pumps. if you do find away you will have a very lucrative patent!

Annatar

Lu Tze wrote: »

No not really-thats why we have been building water towers instead of reservoirs in low pressure area as there is no way to compensate other than booster pumps. if you do find away you will have a very lucrative patent!

Aaargghhh!!
Up to me to save the world. AGAIN!

Where did i put my thinking cap???!!!!?

At the mo, I was thinking of a tower but with a looped pipe syphoning water up and down.
Actually doesnt need to be a tower. a handy hillside, up n down would - should serve

Annatar

Annatar wrote: »

Aaargghhh!!
Up to me to save the world. AGAIN!

Where did i put my thinking cap???!!!!?

At the mo, I was thinking of a tower but with a looped pipe syphoning water up and down.
Actually doesnt need to be a tower. a handy hillside, up n down would - should serve

Actually scratch that.
Head will only be from intake level to output level. A loop up n down of a millon miles gains nothing

mumhaabu

Planet Mechanics on National Geographic did this which was shown on Nat Geo around this time last year.

http://www1.natgeochannel.co.uk/explore/green/mechanics_prog.aspx?mediaType=video&ep=3

The basically got a natural dam in a stream up a mountain and ran loads of Firefighters hose down the mountain to spin a turbine which recharged a battery bank with an inverter attached for to provide power for a remote cabin in the welsh valleys which was targeting itself for zero emissions and to attract the ever expanding eco tourism market. They were replacing a Diesel Generator which was difficult to run due to the fact their was only a track to the cabin and Diesel had to be hauled in by the 5 gallon drum load by hand up a mountain - not easy!

It might be archived somewhere on Rapidshare if you look around. It believe watching this programme would help as it is based on the Scrapheap challenge format and Colonel Dick hosted it.

quentingargan

I've fitted a micro-hydro here. If you have running water year around, it is by far the best way of getting electricity - way more than wind (and I sell wind turbines, so I should be saying the opposite really....:()

I've never done attachments before, but hopefully there will be an attachment here which is the owners manual for this turbine. It shows how to measure the pressure drop caused by pipework, how to calculate the flow etc. According to this, 6 m head and 5 l/sec should give you 180 watts. That would be pretty good if you have it... The machine itself cost me about €2,200, but you'd need either batteries or a grid tie inverter with this. Q

Lightning McQue

Quentin

Would it be possible for you to put up photographs of your micro-hydro turbine site.

How big is the turbine in Kw?

how much electricity does it generate over the year?

What is the payback period?

How much did the groundworks cost?

How much are the maintenance costs?

Could a lay person look after any maintenance issues?

Have you installed any in the South Leinster region?

Which is the best system - battery or grid connected in terms of costs, maintenance, payback etc?

Thanks

Lightning McQueen

quentingargan

Hi Lightening,

I'm not an expert on hydro to be honest, and I don't really sell them, though I have played around with them a bit, and brought a few in for myself and friends who want them.

In relation to your questions

How big is the turbine in Kw?
The turbine has a variable jet and you can adjust the magnetic drag on the generator, so it can go up to 1.9kw with an optimum flow and head height, but in practice, our site is not ideal and we only use it to take 5L/sec from a pond which can only run it for a few days at a time.

how much electricity does it generate over the year?
As above, we only use it occasionally (when there is no wind) but if you have enough flow and head height it could generate 16,000 units of electricity a year. Grid tied, that would be worth about €200 a year. Payback time two years or maybe three. But in practice, most sites wouldn't let it run flat out like that.

How much did the groundworks cost?
Just 250m of 2" pipe in our case. Higher flow rates would need a larger pipe.

How much are the maintenance costs?
None. Bearings if ever needed. Clean the filter at the top every month or so. Thats about it.

Could a lay person look after any maintenance issues?
Yes,

Have you installed any in the South Leinster region?
No

Which is the best system - battery or grid connected in terms of costs, maintenance, payback etc?
Now that there is a feed in tariff, I'd say grid tied.

Q

Cheeble

Hi Q,

Can you resolve this apparent contradiction for me?

quentingargan wrote: »

.....The machine itself cost me about €2,200.....

quentingargan wrote: »

.....worth about €200 a year. Payback time two years or maybe three.....

Cheeble-eers

Annatar

I have an idea....
(a)
Okay lets say its a one metre difference in elevation from pipe inlet to generator, and a 24 metre drop from generator to outlet.
Im figuring the position of the generator doesnt actually matter as long as its a nice closed system (no air) from inlet to outlet - push AND pull.
And so the above head is 25 metres.

Why do this? Might be easier to get permission to lay the "post-generator piping" in a streambed that passes through a neighbours land than it would be to build a generator housing there.

Now... a progression on this.
(b)
My Uncles have drilled down 80-100 feet to get drinkable water - pumping it out etc.
What if you drill a similar hole but use this for the post generator piping.
Dump the water underground. Voila!! Instant Head.... (thats sounds dodgy)

Unknown bit.... would the subterranean dumping area absorb the flow???

See attached image... might make it clearer what Im prattling on about.


Whatchas think?

quentingargan

Cheeble wrote: »

Hi Q,

Can you resolve this apparent contradiction for me?





Cheeble-eers

Oops. That should be €2,000 per year. There are costs for inverter and civil work. Q

dbar

Annatar wrote: »

I have an idea....
(a)
Okay lets say its a one metre difference in elevation from pipe inlet to generator, and a 24 metre drop from generator to outlet.
Im figuring the position of the generator doesnt actually matter as long as its a nice closed system (no air) from inlet to outlet - push AND pull.
And so the above head is 25 metres.

Why do this? Might be easier to get permission to lay the "post-generator piping" in a streambed that passes through a neighbours land than it would be to build a generator housing there.

Now... a progression on this.
(b)
My Uncles have drilled down 80-100 feet to get drinkable water - pumping it out etc.
What if you drill a similar hole but use this for the post generator piping.
Dump the water underground. Voila!! Instant Head.... (thats sounds dodgy)

Unknown bit.... would the subterranean dumping area absorb the flow???

See attached image... might make it clearer what Im prattling on about.


Whatchas think?

Wont work Im afraid, its the head (Pressure) before the Turbine that counts, not after.

Lightning McQue

Quentin

The turbine costs €2200

What is the cost of the grid tie inverter, 250 metre of pipe, civil costs, electrician to wire to the fuseboard, switching gear.

Are there any other costs I have left out?

The payback period seems very short. You may not generate 16000 kw/year. I presume this is 1.9*34*352. What about dry periods so I presume you never oversize the turbine. So if you generate 70% of the proposed output and assuming that the cost of the project was €10000 then your pay back period would be 10 years.

So I guess with night rate electricity and generating your own electricity there would be no point in installing solar panels.

If you were to install a 11 kw heat pump would you generate enough electricity over the course of the year to run the heat pump with a 1.9 kw turbine. I presume after 10 years that effectively you would be running the heat pump on free/green electricty.

Does this have any merit or is this too simplistic an idea?

Your thoughts would be appreciated.

Lighning McQueen

me_right_one

Hmmmm. All very interesting. If you generated enough elec to run a house, how would you regulate it and ensure the power supply was steady? You couldnt have much fluctuation in power for PC's, flatscreen tele's etc

Lightning McQue

A 1.9 Kw turbine doesnt have the capacity to generate enough electricity to say run the washing machine or dishwasher. But if its grid-tied then you get a credit for the electricity that you do generate and over the course of the year you may generate enough to cover the cost of your ESB bill. The heat pump is switched off from May to October but the turbine will still be generating electricity (the stream doesnt stop flowing). I presume that 16000*.09c =€1440. You will not be using that much electricity over the Summer etc. Micro-hydro is a well proven technology in Canada etc and identifying the energy potential of the site is the key.

So is it worthwhile, hopefully Quention can answer that question.

Lighning McQueen

Annatar

dbar wrote: »

Wont work Im afraid, its the head (Pressure) before the Turbine that counts, not after.

But, to use the aforementioned example, the post-gen 24 metres would introduce its own pressure through the generator on the water in the pre-gen pipe. The trick is to keep it completely air free. All pipes running full with water. So the pressure is constant.
A regulating stopcock at the outlet might need to be introduced to fine tune it.

How do I explain what I mean...?
attached an image... everyone has done this at some stage. A glass under the water, turned upside down and drawn nearly all the way out. It airlocks.
The water under the pull of gravity wants to go down, and so exerts a pull pressure on the sides of the glass. Actually probably more accurate to say the pressure inside the glass is less than outside, to external airpressure wants to squish the glass.
Either way its the same result.
The same would happen in the Post-Gen pipe except it would be in constant motion. The sub pressure post-gen will drag water through the generator but will never be satisfied, and so it will continue as long as there is water filling all the pipes to capacity.

quentingargan

Lightning McQue wrote: »

A 1.9 Kw turbine doesnt have the capacity to generate enough electricity to say run the washing machine or dishwasher. But if its grid-tied then you get a credit for the electricity that you do generate and over the course of the year you may generate enough to cover the cost of your ESB bill. The heat pump is switched off from May to October but the turbine will still be generating electricity (the stream doesnt stop flowing). I presume that 16000*.09c =€1440. You will not be using that much electricity over the Summer etc. Micro-hydro is a well proven technology in Canada etc and identifying the energy potential of the site is the key.

So is it worthwhile, hopefully Quention can answer that question.

Lighning McQueen

All microgenerators produce wild AC which has variable frequency and voltage and would blow the daylights out of any device. You either regulate this by using batteries and an inberter, or (preferably) by grid-tie, using the grid as a buffer and selling your surplus / buying your shortfalls.

The new feed in tariff of 19c per kwHr make this a total no-brainer if you have a stream that runs 365 days a year.

In relation to the other discussion about sucking water through a turbine, I'm afraid ones I have worked with rely on a jet of water running through free air space to hit a revolving turgo wheel. It wouldn't work without air. Q

Cheeble

There are some good videos on you-tube showing pelton turbines. See for example this one running off a 60m head!
http://www.youtube.com/watch?v=r7DFDrFbWT4

Q is right about these needing the jet of water in air.

In principle however, Annatar is also correct that if a closed, air-free system is used, it doesn't matter whether the turbine is at the top or bottom of the pipe (other than second order problems with cavitation if the static head is too low). A turbine doesn't work off pressure; it works off flow.

Practically, there are a lot of problems with implementing such a scheme, but it could be done.

Lightning McQue

Cheebie

Do you instal micro-hydro turbines and if you do where are you located?


Lightning McQueen

derry

Annatar wrote: »

Theoretical power (P) = Flow rate (Q) x Head (H) x Gravity (g) = 9.81 m/s2 )

Great thread .
Some people figure you can make power from the rain water flowing down the drain pipes.
So as to be better able to explain the concept of how much volumes of water are needed to generate hydro power can you run a simple calculation ( eg max theory power without all the losses)

The example I would prefer to use is a oliympic pool 2500 cubic meters of water 2 meters deep x 50 meters x 25 meter raised 2 meters above the ground where the hydro generator is .(I presume this is average head of 3 meters starting at 4 meters and finishing at 2 meters)

I would like to show that it could produce say X Kw for Y time such as 24 hours ( rougly of course) and my head for these maths isnt great except I know it not a lot of power

assuming flow rate (Q)is liters per second seconds I figure on ~8.5kw for 24 hours is that correct
Also would deviding by 2 the answer be the norm to get approx real world results ???

2500/24/60/60=~0.3 meteres per seconds or 300 liters per second

300 x 3 meters x ~10 for gravity =~9000 watts (note my crappy maths might be wrong)

Others with good maths can also supply the solution if they wish preferably with formula shown as well

From that I can plug in other number like increase in head of height or increase in volume of water or increase in power demands to show other examples

thanks

Derry

Lightning McQue

Derry

Heres a simple example I did recently on a site

The flow calculation

Get a container and see how long it takes to fill it. eg 104 litre container, so say it takes 5 seconds to fill the container then litres per minute is 60/5*104 = 1248 lpm or 20.80 litres per second

Head calculation 8 metres

Gravitional constant 9.81

Water to wire efficiency 70%

power (watts) = 8*20.80*9.81*70%
= 1143

Obviously the flow may change over the year so you should measure it over the winter and summer months

The site has the potential to produce 10013 kw/h

Lighning McQueen

Cheeble

Derry,

I'd start out by considering the potential energy stored in the water due to the 3m average height:

Volume of water v 2500 m3
mass of water m 2500000 kg
average height difference h 3 m
gravity g 9.81 m/s2
Potential Energy m*g*h 73575000 joules
Time t 24 hours
Time (Secs) t 86400 seconds
Joules/second Power 852 Watts

Assuming 100% conversion efficiency.
Hope I haven't dropped a decimal along the way.

Cheeble-eers

derry

Cheeble wrote: »

Derry,

I'd start out by considering the potential energy stored in the water due to the 3m average height:

Volume of water v 2500 m3
mass of water m 2500000 kg
average height difference h 3 m
gravity g 9.81 m/s2
Potential Energy m*g*h 73575000 joules
Time t 24 hours
Time (Secs) t 86400 seconds
Joules/second Power 852 Watts

Assuming 100% conversion efficiency.
Hope I haven't dropped a decimal along the way.

Cheeble-eers

Thanks

Looks good to me

So soultion is only about 0.85Kw so real world more like 0.5Kw average power so not much to power a house

To get 5 kilowatt real world what a small house could easly use would require 8 olyimpic pools region of water with average head of 3 meters and then how to refill the 8 pools every day

It gives some idea of how much water is needed to get any power as most dams will only let the dam run down 10% before stopping power production

From the maths a smaller body of water with a high head is the better solution but those are harder to find or make

I worked in France on a small lake fixxing power lines and the lake was like 10 miles long and two miles wide with a good head of ~300 feet to the turbines(realy a repump water back up at night time solution).Power was low only 6 megawatt barely eneough for the local village of ~500 houses

Derry