A gravity turbine idea

What's not clear is how you extract the energy from a spinning, falling rotor.

And how is this more efficient than a conventional hydroelectric power station?

Hi, the rotor spins inside a stator, like a standard turbine, the difference being that there is a vertical displacement to the rotor (as that is how the rotor gains it's spin); I feel it is better than a hydroelectric turbine because there is the potential to run this turbine down a much longer drop than is possible (or at least, efficient), with a hydroelectric turbine.

Ok, I think I know how it works now.

Chris Bestwick said:

The speed of the rotor could be governed by a regenerative braking system to maximise overall efficiency.

Surely, the regenerative braking is the principle of how it works, rather than being an add-on.

No, the main premise is the turbine - the weight of the water (and rotor), provide the potential energy of the system that is transformed to electrical energy via the rotation of the rotors within the stator; the regenerative braking serves to mediate the rotational speed of the rotor (and also to increase the efficiency of the system). The system could just utilise regenerative braking (and I have considered it previously); it would serve to make the system much simpler, but I'm unsure as to which system would prove more efficient or scalable - as I said, I'm not an engineer!

Hi Chris,

My perspective on this comes from my past life as an R&D manager and IP manager for the UK part of a major multinational - it's the sort of role where individuals were always approaching me with concepts for new products.

Sadly, as it sounds like you've already found, it's a vicious circle: it's pretty much impossible to get support until you have a viable prototype / model, and clear evidence of potential customers (i.e. market), and it's really hard to get that without the funding...which takes you back round the loop.

My experience is that major investors (whether purely financial, or large companies looking to support development with a view to buying it) will, quite bluntly, expect you to re-mortgage your house to fund initial investment - their attitude will be that if you don't have enough faith in it to put your money on the line, why should they. I'm not defending that view, it just is what it is. Which is no real help whatsoever at this stage where you're being quite honest that you simply don't know.

However, two paths I have seen work are:

1. Find a small company in a related field who might be interested. They won't have huge resources, but if you can get the enthusiasm of the owner / CEO / MD they may be willing to put some effort in outside office hours to at least help with feasibility. Obviously you have to be careful with IP here, sadly you can't take much on trust, I'll say more about that in a moment.
2. Find a university that's interested. Universities are always looking for good student projects. I realise from your past life that I'm probably teaching grandmother's egg-sucking here, but for undergraduate (and even PhD!) projects there doesn't have to be a commercially viable outcome, all that matters is there is something which is interesting to investigate. Which this would be. So you get a bit of free development research, they get a nice project, the only downside is that it won't happen fast and may need to be repeated a couple of times to get a useful answer - so maybe one year a student investigates the technical feasibility, the next year a different student investigates the commercial feasibility. And in my experience this is less risky from the IP point of view: Universities have to be seen to be squeaky clean there, so if it starts becoming viable their IP team will work with you on it (although you still have to remember that their IP team is still acting on behalf of the Universities interest, not yours). 

On IP generally, people will advise you to get a patent and to use NDAs when talking to people. To be honest that's all a bit moot anyway as you've described your thoughts here, but in any case with a concept this vague it adds very little value - a big company would find a subtle way around whatever you protected, even if you had the money to take them to court (which it doesn't sound like you do). But what you don't want is to find that an apparently friendly person you discuss it with who tells you that they're not interested - and then a year later produces a product like it. It happens a lot, it's really annoying, and in my experience it's very hard to protect against. The best advice I can give there is that if you do take option 1 above do the best you can to find someone trustworthy, whilst remembering that they will be running a business.

On the design itself, I can see the idea that for e.g. a very low water flow (too low for a turbine) it may still be able to extract useful energy, if the mechanical losses can be kept low enough that the energy output is sufficient to make the energy output cover the cost of manufacture and install. I think if it was my idea I probably would be approaching a University to see if it was an interesting project.   

Hope that helps, although I suspect these are all thoughts you've already been through! 

Andy

Hi Andy,

Thanks for your feedback. I did start out with universities but found that, where they were able to offer it as a student project, there wasn't the adequate funds to undertake any useful work - I was fortunate for my current to be the recipient of three internships - two undergraduate and one master's, made available by funding bodies outside of the universities. It may have been that the internships weren't well focused (I had little to do with them on a daily basis), but they all seemed too limited by the money available.

When I worked at the university, we were fortunate that we were in a growing sector, where numerous companies were willing to offer fully funded PhDs to get the work done that they wanted. As you rightly point out, chasing funding as an individual is much more difficult, to the point that I (and my wife), have decided that I've reached an end, for my health's sake - mental and physical. What I'm doing here is very much the last throw of the dice!

Maybe we need an Ideas Cooperative; I'm sure there are plenty of people who come up with really good ideas but can't get any traction in getting them off the ground, and there are plenty of people who have both the expertise and experience to help them, it's just creating a body that brings them together - all of the orphan and unhomed ideas that would otherwise die, brought together with people who are able to make judgements on those ideas, and then the people who are able to help and direct them towards funding bodies or individual investors. I'm sure there are government bodies that sell to do similarly, but at arm's length, and, from my experience, you have to already have some business acumen and experience: that precludes many people!

Ok so breaking this idea down into parts:

1. Using the potential/gravitational energy released from a large quantity of mass being lowered down a height, be that water in a hydro power plant, or heavy mass lowered down a shaft, or a large mass moving up/down on rails is known physics and at various scales, proven. However to store energy in any significant quantity, generally requires a combination of very significant differences in height between start/end points and very large quantities of mass than can be transferred. Potential energy = mass x gravity x height

Hydro dams and pumped storage use natural or man-made bodies of water with huge capacities for storing water, i.e. mass, to provide that energy storage. Compare that to a mine shaft, where is that huge mass of water or other material going to be held - does it need a large reservoir at the top? Likewise at the bottom, can the mine accommodate those large quantities of water flow into the base or will it need mining further to expand the capacity? Which then raises questions about constructing a large underground reservoir at significant depth.

There are projects looking at using mine shafts but these tend to be based around the use of solid weights/masses being raised/lowered up and down the shaft on ropes. The challenge of these though would be the quantity of mass, and hence energy stored, is much, much lower due to the limited mass involved. Some designs propose arrangements of using multiple masses, large numbers of weights, but then there's a practical question of handling, connecting, lowering, disconnecting, moving around the weights/blocks. It's comparatively complex compared to using a liquid like water, which simply flows and can be pumped between upper and lower reservoirs.

2. Extracting the energy from the system - with conventional hydro generators, the turbine extracts the energy from the flow of water driving the generator, and they do this with high efficiency. In a system raising/lowering masses along a vertical shaft, so effectively a lift, this would be ropes/chains/pulleys and a gearbox connected to a motor-generator, again likely to be quite efficient. And in both cases, the major mechanical devices and generators are fixed in a stationary position (very useful for construction, operation and maintenance)

I am not sure what benefit is gained from having the generator directly connected to the mass, moving vertically up/down the mine-shaft with the load, I guess it is akin to the concepts of using heavily loaded trains for energy storage, only rather than using inclined rails, this would be a vertical lift shaft. You refer to a cylindrical stator, how long is this cylindrical stator, is it moving with the rotor and connected mass, or is it fixed extending for the whole of the mine shaft with the rotor and mass moving inside the stator?

Ok, I will try to reply as best I can.

The initial idea is to use mine shafts to house the turbine; some mine shafts are very long with significant galleries that may offer storage and/or drain aways, though geologists would be better placed to comment.

As suggested, if the water supply for the turbine comes from underground reservoirs, supplied by river storm surges, then this could supply the water not far from the surface, given that water can be transported utilising only small drops in levels. As a country, we have to look at ways in which we can mediate flooding given the likelihood that it will become more prevalent and more damaging as time goes on; building the underground reservoirs would thus be, potentially, doubly beneficial. I realise that the volume of water that could be stored and used, would need to be considered, but there may be the potential.

There is no suggestion that the water, as a mass, or as free flowing water, would be moved up and down the shaft. The idea is that the water is ejected when it reaches the bottom of the spindle, reducing the weight of the rotors that needed to be raised to the top of the spindle.

The idea is that the stator covers the run of the rotor, it's run being dictated by engineering limitations and mineshaft depth.

Forgive me if I have failed to address any of your points; I struggle to hold information in my head these days (significant executive function impairment), and trying to go between lists of technical points using very difficult; please do get back to me if I've neglected anything.

If the upper reservoir is a near-surface, but underground, mined reservoir then I think this would be very expensive to construct. It's very expensive to construct a reservoir that's above ground, being underground would add to that cost and complexity significantly. 

The bottom reservoir, at the end of the mineshaft, over time may accumulate water as water is ejected but not returned to the upper reservoir - depending on the natural level of the ground water, mines can naturally flood and can need pumping out so with regular in-flows it could fill up.

An economic factor which would make it very difficult, is how much water would be available to supply the upper reservoir. Typically hydro reservoirs are on the surface, they have large catchment areas and are fed by rivers and steams all year round, relying on significant in-flows. I'm not sure how an underground reservoir could secure sufficient annual water flow.

For the stator, electrical stators are constructed from reasonably expensive materials - magnetic steel laminations, insulated copper windings, frames to hold the assembly together, protective varnishes and coatings. They are engineered to be compact because being big makes them both expensive and incredibly heavy due to the magnetic steel cores, the largest stators you might find on a very large power station are under 8 metres in length, with relatively small bores. compared to a mine shaft.

Constructing a stator that extended over the length of the mine shaft reaching into the high tens or hundreds of metres would, in practice, appear to be impossible due to the size, cost and weight of such a stator. 

Unfortunately even very mature energy storage technologies like hydro, using well established proven technologies are incredibly challenging in terms of the economics to make the projects viable, which is why there have been so few built in recent years. Hydro project of any scale are in the realm of very large projects, they're of a size that even very large companies approach cautiously because of the costs involved.