A gravity turbine idea

Hi all,

Forgive me for such a long first post – I wanted to give some background to the situation and felt that I needed to try to explain my idea as fully as possible if I were going to ask anyone to comment on it; I do not know if there is any value in what I propose but I am at a loss as to what else to do.

In 2018 I had an idea for a new type of renewable energy turbine, and I have spent the last eight years trying to make it a reality.

At separate times I have had involvement from Professor Chris Sansom (Professor of Concentrating Solar Power (CSP) and Theme Lead, Zero Carbon at Derby University) and Professor Jo Darkwa (Professor of Energy Storage Technologies, Faculty of Engineering for the University of Nottingham). To a large degree, the issue has been the same at both institutions; namely a lack of funding. At Derby University I was fortunate that my company, Vortex Energies Ltd., was the recipient of three funded internships; but the level of funding didn’t allow for adequate modelling or sufficient practical work to be undertaken. Jo Darkwa recognises that a full feasibility study is required but has so far been unable to locate suitable funding.

It has been repeatedly suggested that I pursue investors personally; this may be an avenue for some, except that I have no experience of running a business (Vortex Energies Ltd. was only set up as part of Derby’s funding applications process). Additionally, I have suffered a couple of strokes that have left me with some physical and cognitive difficulties; even if someone were to invest in the idea, I simply couldn’t run the business side, and the technical aspects are way beyond me. I also have no connections with either engineering or physics, which would at least have offered some credibility in putting forward my idea.

To give some background to my personal situation: before my first stroke in 2016, I spent twenty years as a carer for my wife, who has ME. Prior to that (and before going to university to study archaeology) I was a Research Technician at the University of Nottingham in the Laboratory of Biophysics and Surface Analysis, Pharmaceutical Sciences.

Having spent the last eight years trying to get the idea off the ground, I promised my wife that if nothing came of the discussions with Prof Jo Darkwa, I would call it a day, considering the toll it’s taken on us both from chasing the idea for those years.

And that is where I am now. I don’t know what to do with the idea; I have no clue as to its viability and I can’t take it forward myself.

What does give me heart is that having had two professors look at the idea, they both felt it had enough merit to be worthy of further consideration. I do not know if this was a result of academic intrigue or because they felt there was a possibility of it becoming a viable business proposition? But given how limited the scope is, in academia, to pursue an ideafor its own sake these days, you might hope it would be the latter, though others will be better judges.

Feel free to contact me or ask any questions but please bear in mind that I am not an engineer or physicist, and my grasp of any technical aspect is, at best, limited.

Chris Bestwick

GRAVITY TURBINE: a system for storing and generating green electricity, as and when it is needed. A more predictable source of renewable energy, available at any time and in any weather, and with the security of mainland production of energy.

A cylindrical stator houses a rotor that gains its rotation by falling down a threaded spindle, driven by gravity. The rotor carries a payload, creating a larger mass, and thus higher potential and kinetic energy in the system.

The speed of the rotor could be governed by a regenerative braking system to maximise overall efficiency. The payload would be ejected at the bottom of the spindle to reduce the energy needed to return the rotor to the top of the spindle, where a new payload would be added. The rotor would be removed from the spindle at the bottom to be returned separately, allowing other rotors to run down the spindle unimpeded.

The payload could be anything that can quickly and easily be removed/ejected, and may be determined by local factors. Water would be an obvious choice, given its relative abundance (in the UK), its clean, non-toxic nature and possible ease of supply.

We could consider that the water supply could largely, if not entirely, be met by building a series of underground reservoirs, fed by storm water surges in rivers (given that these events are likely to become more prevalent as the climate crisis plays out), and possibly run off from towns and cities. This would have the added benefit (and possible funding sources), of reducing flooding downriver, and the water could be transported significant distances with little cost in elevation (in relation to the elevation of the turbine siting – see the aqueduct carrying water from Uzes to Nîmes, a distance of 50km with a total vertical drop of 17 meters). It would have the added benefit of not imperilling river ecosystems by taking water directly from rivers (when at their normal levels).

The rotors could be raised from the bottom of the spindle by utilising the ejected water from the rotors, which runs into a sump beneath the spindle. This then runs into a small-scale water turbine, with the generated electricity feeding into a battery-based energy storage system. Additionally, if a counterweight of containerised water is used to help raise the platform (holding the rotors), and the water is again ejected from the container at the bottom of the spindle, running into the same sump that feeds the small-scale water turbine, in tandem with the water from the rotors, it would reduce the additional required energy needed to return the rotors to the top of the spindle, if not provide it entirely.

The rotor return system could also be self-resetting, with gravity covering the hard work of raising the empty water container to the top of the spindle by allowing the rotor platform to fall to the bottom (in a controlled manner, and assuming it has a higher mass).

This could allow for a completely self-contained system of energy production, with water being the only outside requirement.

A number of rotors could operate within the same stator, their frequency determined by demand; a number of turbines could operate on a single site.

The UK has many old collieries that could provide useful sites in that they already have deep shafts as a precursor to the larger shaft needed for the turbine, whilst the prospect of employment in many of these areas would surely be welcomed. The shaft diameter could be enlarged, allowing for greater electricity generation, if the system showed adequate benefits for doing so.

A secondary shaft would be required for the rotor return system.

 

 

Parents
  • I know I said that I wouldn't pursue the idea any further but, sorry, I lied... Wink

    I wanted to add a few thoughts as to what, I feel, the idea could add to the market; I realise there are difficulties, some related to cost, some related to the physical realisation of the idea, but putting those aside (as I think, perhaps naively, that nothing that has been raised is insurmountable), I wanted to touch upon what I believe to be some potential benefits to the idea that other renewable energy projects can't offer.

    I've touched upon the idea of the underground reservoirs serving two purposes previously, and I do believe that there is some merit in that thinking. As our climate changes and weather systems, fed by warmer land and seas, are able to hold more water, the possibility of flooding events rises: public and private spending on food defenses and mitigation is inevitable.

    If the reservoirs, by taking water from the river basins (or where it is proven to best benefit), can be seen to reduce the extent of flooding, or even the possibility of flooding (though I do understand that flooding can be caused by many factors), then surely it could receive some of the funding for that purpose, and the cost of the reservoirs could be offset (to a degree)?

    If the reservoirs, and by extension, the gravity turbine structure, could be sited underground, this offers a number of benefits: first of all, if there is no visible sign on the surface, it shouldn't garner some of the the disparagement by the public that plagues the installation of solar farms and wind turbines. Additionally, it benefits from being in a place that offers a certain amount of security (and if it was built with this in mind, the potential for a great deal of security), against bad actors, when off-shore wind turbines, and to a degree, land-based wind turbines and solar farms enjoy much less security.

    We have seen that Russia, for instance, is quite happy to ignore the Geneva Convention by attacking civilian infrastructure and energy installations in Ukraine, and we can only assume that, should it ever come to it (and I'm not saying it ever will, but it may prove prudent to ward against it), other bad actors would be quite happy to follow suit.

    Of course, the gravity turbine is not affected by the weather in the same way as wind and solar (assuming that the reservoirs are of a size or number to meet an extended dry spell, such as we've had this year).

    Also, the gravity turbine doesn't require the flow rate of water that many large-scale hydroelectric systems need, although I accept that there would be a sizeable head of water provided by the reservoirs).

    There has been mention of systems utilising old coal mines for generating electricity by dropping weights down the mines and using regenerative braking to generate electricity, though these are better thought of as energy storage systems as they generate as the weight drops but then they utilise cheaper electricity at night to haul the weight back to us starting point. In fact, they actually run at an energy deficit overall due to inefficiencies in the system, or at least to my understanding, but please educate me if my thinking is off.

    There are many systems that rely on this premise (of cheaper energy being used to reset the system at times of low demand); some of the hydroelectric systems pump water back to reservoir to reset the head of water required. The problem comes, as I see it, with the introduction of cheap, reliable and more energy efficient battery storage systems, which may also benefit from greater longevity, certainly without maintenance.

    Not only will they replace old, inefficient systems of energy storage, but energy producers will use them to do away with the old system of peak and low demand times by routing excess energy to these battery systems, to be called upon at times of peak demand, also easing production demand. However, we still need to produce that energy, which is, and will, shift to the sole production of electricity. But then, I may be misunderstanding how things work.

    But anyway, for those that have read it, thank you for your time, and, if all you take away from it is a laugh because of my naivety and misunderstanding, then I'll take that!


    Best regards,

    Chris

  • I know I said that I wouldn't pursue the idea any further but, sorry, I lied...

    No problem, we need subjects for discussion on a discussion forum after all!

    I think it might be useful to put some numbers to things to see how practical they are? For instance, how much electricity do you hope to generate? (for background typical GB usage nationally is usually in the 20 - 45 GW range).

    What sort of usable depths are you envisaging? (I've looked up Thoresby Colliery - the last Nottinghamshire one - its shafts were nearly 800m deep, but the pit head seems to sit less than 70m above sea level - so how will the used water escape? and how fast? How much shaft would remain usable?)

    How much water would be required? E = m.g.h - so 1kg (i.e. 1 litre) of water falling 1m generates about 9.8 Joules - if that happens every second then it'll deliver 9.8 Watts - in a 100% efficient system at least, somewhat less in a practical one. Or if you prefer 1m² (or 1 tonne or 1,000 litres) of water per second delivers at most 9.8kW for each metre of drop.

    How long would you expect the stored water to keep the system running - i.e. how big a reservoir would be needed?

    How long would you expect local rivers (or other sources) take to recharge the reservoir? (especially in summer when there unlikely to be excess water available).

    Perhaps the numbers will be enlightening.

      - Andy.

  • Hi Andy,

    Thank you for your continued interest.

    The simple answer to your question is, I don't know! I'm not an engineer or physicist, and really, it's' why I've ended up on this forum; there are so many variables at play of which I am completely ill-suited to provide answers, whether it's the diameter, depth and payload of the rotor, it's rotational speed and vertical velocity, which might govern the velocity of the magnets through the coils and thus the potential energy generated (though I realise that the overall energy available would be dictated by the weight of the payload and rotor, and the vertical distance it falls); I have many, many questions that I simply cannot resolve myself, and any figures I do put forward would not be based on considered thought.

    I'm sorry I can't be of more help.

    Chris

  • I'm not a proper engineer or physicist either, but I think we can make some progress using really just O-level maths... the only trick, if there is one, is seeing which of the technical details can be ignored, or better still, lumped together into some big overall value.  I'll be making all sort of assumptions and approximations, so do argue about them - mostly we can adjust the answer with simple scaling so no problem.

    1. How much electricity do you want from this? For reference it's said that a modern on-shore wind turbine can product 2 or 3 MW (or less than 0.1% of lowest national demand) Wind turbines are easily scaled up though - you have many of them on a single wind farm and many wind farms across the country. If you're relying on existing, suitable, mine shafts, I guess you'd be far more limited in how many could contribute. Let's say you wanted to contribute 10% to the national supply, and had 100 mine shafts to play with - so each shaft would have to contribute 0.1% - so between 2 and 4 MW say (so in the same ball park as a big wind turbine ... possibly not unreasonable). Let's say 3MW for the time being.

    2. How deep - I reckon height about sea level will be a limiting factor if you're ultimately relying on natural drainage. So let's say 100m deep (that might be generous, but let's see how it plays out).

    3. How much water? OK to get 3MW - i.e. 3,000,000 W from a 100m drop - i.e. calculate m from 3,000,000 = m x g x h where g=9.8 (gravity) and h is the height dropped - i.e.100m so we have 3,000,000 = m x 9.8 x 100, or rearranging to 3,000,000/(9.8x100) = m which I think comes out at just over 3,061 kg - so we'd need that many litres or roughly 3 m³ or 3 tonnes of water per second.

    4. How long? I guess this depends on how you see the system being used - as a main source of generation, a seasonal thing, a regular backup for renewables (e.g. when winds are low) or just for very rare 'keep the grid going at all costs' emergency response. For the sake of a number, lets say a week - i.e. it can run for 7 days before the reservoir is completely exhausted (as before, feel free to haggle).

    If we need 3 m² a second, we'd need 3 x 60 x 60 x 24 x 7 = 1,814,400 m³ for a week. So the reservoir would have to contain that ... if it was 10m deep and mile (1660m) long it would have to be about 109 metres wide (which would cover an area of about 450 acres (I know, mixed units again)) -  that's probably not dissimilar to some of the smaller normal water reservoir in these parts. You'd need one of that size for each shaft of course. Other shapes might do equally well of course (although deep ones might reduce the available head significantly as they emptied).

    As for refilling, say we had a river 20m wide and 2m deep and flowing at 1 metre/second (just random numbers out of my head) and we could take 10% of the flow (the Environment agency probably wouldn't like that, but let's assume for the moment). The total flow would be 20x2x1 m³ or 40 m³ per second, 10% of that, 4 m³. To refill 1,814,400 m³ would therefore take 1,814,400/4 seconds = 453,600 s or about 5.25 days I think. (But of course you could only do that when the river was sufficiently high.)

     How do those numbers feel? (obviously they're just a first approximation and the assumptions - e.g. that generation is 100% efficient so the real answers will be significantly less favourable - but it should give you an idea whether it's go-er that might benefit from a few tweaks, or so far out it's not worth pursuing).

    If it's still a go-er, then start thinking about refining your assumptions - e.g. can you really drain a shaft down to 100m if you have a sizeable river nearby (generally the top of the water in the river equals the level of the water table in the surrounding land...)

        - Andy.

    (please could someone double-check my arithmetic!) 

Reply
  • I'm not a proper engineer or physicist either, but I think we can make some progress using really just O-level maths... the only trick, if there is one, is seeing which of the technical details can be ignored, or better still, lumped together into some big overall value.  I'll be making all sort of assumptions and approximations, so do argue about them - mostly we can adjust the answer with simple scaling so no problem.

    1. How much electricity do you want from this? For reference it's said that a modern on-shore wind turbine can product 2 or 3 MW (or less than 0.1% of lowest national demand) Wind turbines are easily scaled up though - you have many of them on a single wind farm and many wind farms across the country. If you're relying on existing, suitable, mine shafts, I guess you'd be far more limited in how many could contribute. Let's say you wanted to contribute 10% to the national supply, and had 100 mine shafts to play with - so each shaft would have to contribute 0.1% - so between 2 and 4 MW say (so in the same ball park as a big wind turbine ... possibly not unreasonable). Let's say 3MW for the time being.

    2. How deep - I reckon height about sea level will be a limiting factor if you're ultimately relying on natural drainage. So let's say 100m deep (that might be generous, but let's see how it plays out).

    3. How much water? OK to get 3MW - i.e. 3,000,000 W from a 100m drop - i.e. calculate m from 3,000,000 = m x g x h where g=9.8 (gravity) and h is the height dropped - i.e.100m so we have 3,000,000 = m x 9.8 x 100, or rearranging to 3,000,000/(9.8x100) = m which I think comes out at just over 3,061 kg - so we'd need that many litres or roughly 3 m³ or 3 tonnes of water per second.

    4. How long? I guess this depends on how you see the system being used - as a main source of generation, a seasonal thing, a regular backup for renewables (e.g. when winds are low) or just for very rare 'keep the grid going at all costs' emergency response. For the sake of a number, lets say a week - i.e. it can run for 7 days before the reservoir is completely exhausted (as before, feel free to haggle).

    If we need 3 m² a second, we'd need 3 x 60 x 60 x 24 x 7 = 1,814,400 m³ for a week. So the reservoir would have to contain that ... if it was 10m deep and mile (1660m) long it would have to be about 109 metres wide (which would cover an area of about 450 acres (I know, mixed units again)) -  that's probably not dissimilar to some of the smaller normal water reservoir in these parts. You'd need one of that size for each shaft of course. Other shapes might do equally well of course (although deep ones might reduce the available head significantly as they emptied).

    As for refilling, say we had a river 20m wide and 2m deep and flowing at 1 metre/second (just random numbers out of my head) and we could take 10% of the flow (the Environment agency probably wouldn't like that, but let's assume for the moment). The total flow would be 20x2x1 m³ or 40 m³ per second, 10% of that, 4 m³. To refill 1,814,400 m³ would therefore take 1,814,400/4 seconds = 453,600 s or about 5.25 days I think. (But of course you could only do that when the river was sufficiently high.)

     How do those numbers feel? (obviously they're just a first approximation and the assumptions - e.g. that generation is 100% efficient so the real answers will be significantly less favourable - but it should give you an idea whether it's go-er that might benefit from a few tweaks, or so far out it's not worth pursuing).

    If it's still a go-er, then start thinking about refining your assumptions - e.g. can you really drain a shaft down to 100m if you have a sizeable river nearby (generally the top of the water in the river equals the level of the water table in the surrounding land...)

        - Andy.

    (please could someone double-check my arithmetic!) 

Children
  • Hi Andy,

    Good to hear from you again and thanks for your hard work!

    Can we just assume that there is a direct translation from weight of water to output, or do we need to consider the ability of that mass to drive a rotor through the appropriate stator of a certain size? I realise there will be some inefficiencies, regardless, but how do we gauge the appropriate size of stator, the effective back emf, etc?

    The system does not rely on a constant flow of water, more so, there will be rotors dropping down the system at regular intervals such that there is the ability to both empty and remove the rotors. This will obviously impact the throughput and thus the energy produced, though we can make allowances.

    Regarding refilling, I wasn't looking at a constant flow but rather the mass of water available in flood events; quite how much this would be would differ according to each river basin, but the expectation would be that there would be a number of these events through the year, though if your calculations are correct (and I've no reason to doubt them), a good number of reservoirs would need to be filled a number of times per year, even at a relatively low mass per rotor. To a degree, this could be mitigated by extending the run height of the system, but this may not be possible; I have still been unable to track down relevant water tables, so for now, that is a moot point.

    It may be a suitable system for emergency use, though it's a sizeable investment for such an event, particularly as battery systems could now step into the role (assuming they were kept in readiness).

    Again, thank you for your work; it has served to sink my idea, I think, but you have been able to make assumptions that enabled the calculations that simply defeated me - in the years before my strokes, it wouldn't have been an issue, but these days...

    Best regards,

    Chris