Generating electricity from flowing streams.

johntheexpat

So, it goes like this.  I have two sets of friends nearby who have old water mills.  So they both have reasonably fast moving water passing by their properties.  One of them has, for the last four years, been tentatively heading down the "green" electricity route.  One expert who visited reckoned with a bit of planning and structural work, they could pull 40KW of power out of the river, which with generous Government schemes etc, would show a pretty healthy profit.

But, as is always the way, things are painfully slow.  His property sits across the boundaries of two communes, the people who would install the kit aren't the same as the people who would manage the kit and neither of them will actually buy the electricity.  He is being pushed down the "you get free electricity" route in return for letting them install the stuff, but of course, he doesn't ever use 40KW of electricity, so most of the return would go to others.  And then getting everyone to sit down in the same place at the same time is nigh on impossible.

So, I keep telling him to sod the lot of them and find a small turbine that can be placed in the flow and just take the power generated and use it directly to heat the building.  Even if it is only a 1 KW supply, when connected to a heat exchanger, he should be able to pump 4KW of heat into the house 24/7 during autumn/winter/spring and that would easily repay any costs.

The problem is, easy as it sounds, where do you find a turbine like that?  Something that can be powered by flowing water, preferably kick out 230V ac, low maintenance, reasonably cheap and easy to install.

Any help/advice/comments gratefully received.

EarthRod

A motor from a washing machine would produce a decent amount of electricity, but it would have to be a multi-pole permanent magnet type. The motor being turned mechanically (in other words spinning the shaft) would generate the electricity.

A second-hand wind turbine motor might do the trick for the power required. Trouble is they might be expensive!

SteveCritten

Check on Ice energy website I believe you can get a grant.

johntheexpat

The problem with getting grants is that you have to pump the electricity back into the grid, one way or another.  My personal view is that green electricity is only really green when it is used at the point of generation, for small producers.
It seems to me that a typical 3KW installation can never be really green because of the amount of kit that is associated with it.  You seem to need kit to step the voltage up from DC to AC and then get it in phase with the grid.  You need kit to monitor how much is then pumped back into the grid.  Then there is all the remote monitoring, sharing of information and returning money to you that all adds inefficiencies and costs.  Its no wonder that it is only worthwhile when the price is so artificially high.

My view is that you should be able to strip all the kit and middlemen out and use the power generated where it is generated.  Solar panels have a big problem in that you need to store power for when it is needed and the best way at the moment is a pretty meaty lead/acid battery, which isn't cheap.

But with a river, during autumn, winter, early spring, the flow is really pretty reliable.  So what I want to find is a way of taking out a KW or two directly, probably (but not necessarily) converting it to 230V ac, and using it directly so that all the kit associated with measuring it, getting it in phase etc is not needed.

A constant 1KW is 168KWh per week, say for 40 weeks of the year, which is 6,700 KWh per year which at current prices is worth about 650 euros/year.  So a system that costs 3000 euros would have a return of about 20%.  Which is a pretty reasonable investment if the thing lasts 10 years.

That's basically what I'm looking for.

SteveCritten

My view mate is I agree with you that I would rather renewable energy be truly green but it isn't. So until then if the government are throwing my money at it then I may as well have a piece of it. I was looking at solar panels and the storage batteries way back in the eighties when I built my first house. Still panels aren't efficient enough still all these years later and wonder if they ever will.

johntheexpat

I'm really not sure I would ever invest in solar panels, but with the stream thing, these friends of mine could be pulling a reliable 24/7 draw of several KW.  The problem with going down the grants path is that firstly, the project isn't run of the mill (pun very much intended) and secondly the interested parties are keen to max out the return, so are looking for a big job (40KW or there abouts).  I sit here slightly apart form all this and see a project that is making no progress and shed-loads of potentially free energy just washing away down the river.

It has been discussed for several years now and knowing the French, it could go on for many more years before anything moves, hence my desire to come along with an instant, cheap, discreet and easy to install option that would at least get some return.

EarthRod

OK. This would be an interesting project for your friends and I can also see why you are interested.

I think you need to get a few things down on paper to 'establish' the requirements and costs. For example:

1. Determine what power output is needed to meet minimum requirements.
2. Source a multi-pole permanent magnet type electric motor to meet power requirements.
3. How fast does the stream move, note lowest speed and fastest speed.
4. Having determined the speed of water, calculate what reducing or increasing ratio gears are required to produce the right speed to spin the electric motor shaft to obtain the correct voltage output.
5. Incorporate safety cut-out mechanism between stream wheel and ratio gearing.
6. Source a switching control panel for the electrical output from the motor to feed into the house power distribution. Must have necessary gauges, fuses and safety over-voltage and under-voltage cut-out devices.
7. The system will require approval by a qualified electrical engineer and possibly the local council and property insurers (they will at least need to be notified).

Not an easy project and fraught with technical issues. Your friends need to talk with someone who has already successfully carried out a similar build.

SteveCritten

Plus don't forget permission from British Waterways as though you and your friends may own the land the stream runs through the water is the responsibility of British Waterways.

EarthRod

John has not made it clear if this is in France or UK.

Also, does the water wheel exist as part of the building? If not then structural engineering is required which of course involves planning permission, a structural engineer, as Steve says - waterways permission, and anyone downstream who might be concerned about the water flow (fishing farm for example).

This is getting very expensive!

noiseboy72

British Waterways no longer exist, it's the Canal and River Trust. However, they have nothing to do with ditches and small streams with no navigation. You need to talk to your local water company or drainage board - depending upon where you are. (Assuming this is the UK!!)

Putting power into the grid is actually not that difficult. You use a grid tie inverter to convert from the variable DC to in-phase AC. You then have the meter changed for one that will essentially run both ways, recording power used and that returned to the grid. In the UK, this is fairly simple to arrange, but of course, it all needs installing by a qualified electrician.

The complications only start to arrive if you are generating over 10KW or so, as this will most likely require significant changes to your wiring and potentially that coming into the house.