Wind Turbine Hydraulic to Electrical Conversion

In summary: Yes. I have made several reliable rotating hydraulic couplings. They can accommodate changes in wind speed, direction, and flow.
  • #1
deckart
106
4
As a hobby for the last couple of years, I've been designing various theoretical wave and wind generator devices. One of the primary criteria is that the electrical power generation components have to be easily accessible.

For wave power, electrical power generation has to be on shore not in the water. For wind power, electrical power generation has to be on the ground not in the air.

That's where it gets tricky with a wind turbine. Mechanically, you can have a shaft transfer the torque to the ground components, but that same torque acts on the turbine head position. To avoid this, I've designed a means to convert the torque directly to hydraulic energy and transfer it via a rotary swivel and hydraulic lines.

Why hydraulics and not direct electrical? The main reason is that I'm a hydraulics guy and I know little about the intricacies of getting the wind turbine gen motor to produce 60Hz 240VAC electrically with a varying input velocity and torque. But I do know how to couple a hydraulic motor directly to a generator motor and spin it at the precise RPM required.

This idea is for on-grid supplementary use and for auxiliary shop hydraulic supply.

And that's where I'm going. But I'd love some input from fellow designers and hobbyists.
 
  • Like
Likes PaulK2
Engineering news on Phys.org
  • #2
Some thoughts:
A well designed hydraulic motor or pump may be 90% efficient. Add in some line losses, and the system mechanical efficiency will be, at best, 70%. You will lose at least 30% of your power when you remotely locate the generator.

You could use the water as your hydraulic fluid in a wave generator. Any leaks would be zero pollution.
 
  • Like
Likes deckart
  • #3
The motor that drives the generator can be 80-98% volumetrically efficient (80-90% mechanically efficient) depending on the type that is used. But, the "pump" at the turbine head will be near 100% (volumetrically) due to the use of hydraulic cylinders radially configured instead of a typical pump. Line loss will be nil because flow will be low in relation to line size. I dare say that the system will be comparable to the electrical equivalent net output.

And, in the end, any losses aren't really losses when the energy is free.

Water is superior to oil for transmitting energy. But, you lose lubricity and you have icing at low temp.

Thanks for input, jrmichler, I'm looking for holes in the idea!
 
  • #4
How much is the financial benefit of locating the generator at the bottom of the tower instead of the top?
 
  • #5
For a moderate residential installation, about 50 vertical feet.
 
  • #6
deckart said:
For wind power, electrical power generation has to be on the ground not in the air.
deckart said:
I know little about the intricacies of getting the wind turbine gen motor to produce 60Hz 240VAC electrically with a varying input velocity and torque.
You don't need to produce AC Mains frequency and voltage at the generator mounted to the top of the wind turbine -- you use whatever electrical generator works best up in the turbine body, and do the power conversion on the ground:

http://formatex.info/energymaterialsbook/book/559-571.pdf
deckart said:
This idea is for on-grid supplementary use and for auxiliary shop hydraulic supply.
Are you familiar with "Anti-Islanding" and other requirements for connecting your own power generation hardware to your grid connection?
 
  • #7
Hi berkeman, thank you for posting that method of converting the input. It gives me confidence in the method that I've developed which is far less complex and far less expensive.

No, I know little about the requirements for connecting my own power generation to the grid. I'm sure my power company will give me all the direction I need on that end.
 
  • #8
deckart said:
No, I know little about the requirements for connecting my own power generation to the grid. I'm sure my power company will give me all the direction I need on that end.
Yes, Your local power company is definitely the right resource for that information. :smile:
 
  • Like
Likes deckart
  • #9
This is where we exploit the advantages of pressurized fluid as a power transmission medium. Converting rotary motion directly to psi/in2 energy units and converting it again to rotary motion of a much higher velocity with low energy losses. With electrical/mechanical component combinations doing this is very expensive.

Attached is a picture of the small actuators I will use for the radial pump located at the turbine head. Except the ones shown in the photo are 1" stroke, I will use 3" stroke cylinders for the "pump" in the configuration shown in the cut-away model pic. Each cylinder is $151.50/ea retail.
0321181148.jpg

Clipboard01.jpg


The cylinders can be turned off individually and allowed to float so that turbine can continue turn and produce energy at low wind speeds. This energy is stored in an accumulator until saturated, then released to the hydraulic generator motor.

Capture14.png
 

Attachments

  • 0321181148.jpg
    0321181148.jpg
    29.2 KB · Views: 962
  • Clipboard01.jpg
    Clipboard01.jpg
    20.8 KB · Views: 1,004
  • Capture14.png
    Capture14.png
    11.3 KB · Views: 984
  • #10
Is it possible to make a reliable rotating hydraulic coupling? eg to allow for changes in wind direction?
 
  • #11
CWatters said:
Is it possible to make a reliable rotating hydraulic coupling? eg to allow for changes in wind direction?

Yes, hydraulic swivels are available. That circular symbol on the bottom right of the schematic depicts a hydraulic swivel. This is how they work:
swivel.png
 

Attachments

  • swivel.png
    swivel.png
    5.7 KB · Views: 1,071
  • #12
Would the seals in the swivel be more reliable than say the bearings in a generator?

Edit: Actually I'm not sure how they transmit the electrical power down from a conventional turbine. Do they use slip rings or a larger version of an electric toothbrush charger?
 
  • #13
CWatters said:
Would the seals in the swivel be more reliable than say the bearings in a generator?
As reliable, maybe. Hydraulic excavators use them to get power to the tracks and they work for decades without fail.
 
  • #14
Here is an updated, complete schematic of the concept system. Very compact, simple, efficient, and cost-effective transfer of energy directly to a 60Hz 240VAC generator. And completely scalable.

After looking at other radial piston designs I've opted for a 5 cylinder pump system. Again, each cylinder is able to be turned off and allowed to float so that the lightest wind can keep the turbine rotating.

One of the reasons I'm sharing this is because I believe fluid power systems are being overlooked in the renewable energy industry. And there are a lot of applications, such as in wind turbines, that such systems are very well suited. This thread is also being shared on Reddit.

turbine_pump.png
 

Attachments

  • turbine_pump.png
    turbine_pump.png
    13.3 KB · Views: 977
  • Like
Likes PaulK2
  • #15
I think you would need to quantity the costs and benefits compared to current practice before anyone would adopt the idea.

I wondered if one possibility would be to connect multiply turbines to one generator? Perhaps even run hydraulic lines from off shore turbines to on shore generators (10-20km?).
 
  • Like
Likes PaulK2
  • #16
CWatters said:
I think you would need to quantity the costs and benefits compared to current practice before anyone would adopt the idea.

I wondered if one possibility would be to connect multiply turbines to one generator? Perhaps even run hydraulic lines from off shore turbines to on shore generators (10-20km?).

Quantifying costs will be difficult. I will need to consult with engineers that design them and I don't know any, yet. I can only use general comparisons with the components that I work with.

It makes sense to convert the hydraulic energy to electrical energy close to the turbines. Energy travels long distances more efficiently as electricity.

The primary advantage of using hydraulics is going to be how it deals with a varying input RPM and load, and the energy conversion is very direct. The disadvantage is that you may have more moving parts. But the parts are simple, common, and relatively inexpensive.
 
  • #17
deckart said:
The primary advantage of using hydraulics is going to be how it deals with a varying input RPM and load,

I'm not an expert on turbines but I know they have developed power electronics to decouple what the generator is doing from what the grid is doing ...

Google found..
https://www.nrel.gov/docs/fy12osti/54605.pdf

Page 3..
Most large scale wind turbines installed during the 1980’s and 1990’s used gearboxes and fixed speed generators that produced voltage synchronous with the utility grid [6]. The wind turbine industry has since moved to using variable speed wind turbines that can maximize below-rated power production by matching blade tip-speeds against prevailing wind speeds to maximize aerodynamic efficiency, as described in Section II-C1.Variable speed operation is typically achieved by using one of two different configurations. The first employs a synchronous generator that spins at variable speeds and uses a full power converter to ensure the produced power matches in frequency and phase to that of the utility grid and is known as a ‘type 4’ wind generator [7]. The second, and most common way of achieving variable speed operation is to use a doubly-fed induction generator (DFIG), known as a ‘type 3’ wind generator [7]. The stator of a DFIG is directly connected to the grid while the electromagnets of the rotor are excited by a time-varying waveform that is produced by power electronics that need to only convert roughly 30% of the turbine’s rated power [7]. Almost all commercially available large scale wind turbines use either type 3 or 4 generators, both of which [are] effectively decoupled from the grid via their power electronics.
 
  • #18
I literally just spoke to our Director of Research & Development while getting coffee, who has a Ph.D. in an Electrical Engineering discipline (I forget the exact title), and he described a couple of methods that are used, rectification/inverting and the one above (DFIG) to deal with the varying input velocities. Most of it is over my head but he says that it is an expensive problem. Apparently, he knows a lot about how these large wind turbines work.

I only get to speak to him in passing but I pick his brain his brain on occasion. While walking back with him in the hall I mentioned that I had created a hydraulic circuit easily captures the energy regardless of the turbine velocity and he thinks it is a great approach. Then he went on about how accumulators, like supercapacitors, are much better at absorbing a lot of energy quickly, more so than batteries... then electrical vehicle braking limitations, aircraft hydraulic hydrostat constant velocity generators to deal with varying input velocities, how leaky hydraulics doesn't have to be an issue... and back to his office he went. lol

I'm getting that using hydraulics with wind turbines just hasn't been explored entirely.
 
  • #19
This system is commonly known as a 'variable displacement hydrostatic transmission'. Mitsubishi Heavy Industries has invested somewhat in the idea with the purchase of Scotland-based Artemis Intelligent Power. Their design is also a radial piston pump with piston shut-off for low speed to maintain electrical output frequency. They are currently looking at applying it for wave energy converters.

I have also designed a variant of the hydrostatic transmission with a novel axial-piston reciprocating pump that does not require an eccentric driveshaft. I showed the design to the local Parker Hannifin office but they weren't interested.

It is a shame as the pump seems to be a promising alternative to permanent-magnet or gear-driven electric motors.
 
  • Like
Likes deckart
  • #20
Punch-line said:
This system is commonly known as a 'variable displacement hydrostatic transmission'. Mitsubishi Heavy Industries has invested somewhat in the idea with the purchase of Scotland-based Artemis Intelligent Power. Their design is also a radial piston pump with piston shut-off for low speed to maintain electrical output frequency. They are currently looking at applying it for wave energy converters.

I have also designed a variant of the hydrostatic transmission with a novel axial-piston reciprocating pump that does not require an eccentric driveshaft. I showed the design to the local Parker Hannifin office but they weren't interested.

It is a shame as the pump seems to be a promising alternative to permanent-magnet or gear-driven electric motors.

That's great, Punch-line! I'd love to see your hydrostatic transmission concept.

I am familiar with the DDT (Digital Displacement Transmission), it is a cool technology that is gaining interest in the Fluid Power industry. Here is a recent article describing how it works in the Fluid Power Journal: http://fluidpowerjournal.com/2018/03/digital-displacement-pumps/

I'm in the process of developing a prototype of a transmission device, it is depicted downstream of the hydraulic motor that drives the generator in the schematic shown above. It will be the topic of a future post.
 
  • #21
Punch-line said:
This system is commonly known as a 'variable displacement hydrostatic transmission'.

I want to add, there are some differences compared to the common hydrostatic transmission, though functionally, this circuit does operate as one. But the velocities are much lower than is common.

Primarily we are using individual stand-alone hydraulic cylinders as opposed to an actual pump unit. We don't have a minimum RPM in order to maintain the volumetric efficiency a typical pump requires due to machined clearances. Instead of a high-speed (1200-3600 RPM as in a gas or electric prime mover) low torque input, we are working with a low-speed (0-100 RPM, for example) very high torque input. This makes the design very scalable with common components.

I do appreciate the feedback and critique of the design.
 
  • #22
I am by no means an expert on fluid dynamics and pump design so I do have a question about this design. Wouldn't an under square piston configuration with a 3" stroke require pivoting on each individual pump case to reduce side loading on the piston? Would an over square pump with a large bore and a wrist pin on the piston simplify construction in a radial configuration? Are off-the-shelf components in these dimensions readily available?

It would also depend on the torque requirement and form factor to suit it's location. So many factors to take into account.
 
  • #23
To be honest, I don't know the terms "under-square" and "over-square" in this context but I think I'm following you...

The cylinders would have a pivoting mount where they attach to the outer frame.

One of the cylinder rods has to be fixed to the center lug that the rest of the cylinders are attached and be able to handle side loading. That particular cylinder may simply be a ram with no annulus or an oversized rod in order to be stout enough.

Yes, I'm looking at this as something that one could build themselves from common off-the-shelf components but scalable to industrial sizes.
 
  • #24
If I had to use hydraulics, I would use a constant pressure, variable volume pump, driven by a wind turbine. That HP fluid would drive a constant speed hydraulic motor, coupled to an alternator. If the alternator used was a synchronous generator, spinning a few percent above synchronous speed, it could generate 3PH power directly to the grid.
If I needed to store some hydraulic energy I would build a thing like a gasometer, that is pushed upwards by a hydraulic ram. The vacuum pulled inside the gasometer would maintain a constant pressure on the hydraulic ram, avoiding the inverse law for compressed gas. When the wind stops and the pump pressure falls, the gasometer would push fluid out of the ram again to run the motor.
 
  • Like
Likes deckart
  • #25
An updated model of the radial cylinder configuration:
radialconfig.png
 

Attachments

  • radialconfig.png
    radialconfig.png
    26.9 KB · Views: 604
  • #26
For more input on your ideas, you might want to get in touch with "Renewable Energy Long Island", a not-for-profit organization, and "Deepwater Wind" a company currently constructing a wind farm off the shore of southern Long Island.
 
  • Like
Likes berkeman and deckart
  • #27
Baluncore said:
If the alternator used was a synchronous generator, spinning a few percent above synchronous speed, it could generate 3PH power directly to the grid.

Whoops, I think you meant induction generator. It runs a few percent faster than synchronous speed.

A synchronous generator runs at synchronous speed, a few degrees in phase angle ahead of the grid.
 
  • #28
anorlunda said:
Whoops, I think you meant induction generator. It runs a few percent faster than synchronous speed.
Sorry, we all have to sleep sometime.
 
  • Like
Likes anorlunda
  • #29
For various personal (abstract, not commercial nor professional) reasons I find this discussion very interesting
(see i.a. http://fullduplexjonrichfield.blogspot.co.za/2017/04/heavier-duty-banking-appendix-supplement.html)
And I called to mind a discussion about 48 or 50 years ago, when a then colleague in IBM, one James Philbrick (very intelligently creative, but since deceased, I am very sorry to say) described an invention that I admired. I know that he patented it in the same or following year, but I never saw that anyone took it up. I mention it here, as nearly as I remember it, in case anyone can put it to constructive use. Alternatively, if anyone happens to know that it is currently in use, I would be curious to know. Otherwise it would be a pity to waste it, I reckon.

James had been a hydraulics engineer with experience in designing systems for ships, and had recognised that a generalisation of the rotary vane pump could be used to power one flow of liquid by the input of another flow. By shifting the axis of rotation of the rotor, one could smoothly in effect change gear, either moving more fluid against lower resistance, or less fluid against higher resistance. I include a sketch of what I can remember from my distant youth. I omit the notional mechanism for moving the axis of the rotor (James represented it at the time simply as an external lever of type two, with the rotor axis in the middle).

The power is applied by one pair of opposed inlet-outlet channels (say the green arrows) which drives fluid through the other pair according to the position of the rotor in the outer drum. No doubt an arbitrary set of input-output channels could be combined for more complex requirements.

For your attention for what it is worth.

I apologise, but I failed to insert the diagram in usable form. In case my description fails to convey anything articulate (very likely!) I have posted it at:

https://www.facebook.com/photo.php?...5908628.111317.100001576411737&type=3&theater

Good luck to anyone interested.

If anyone could tell me how to include the image more conveniently, feel welcome.
 
  • Like
Likes deckart
  • #30
HI Jon, I will look into this further but from what you just posted, it sounds like the VDT (Variable Displacement Transformer) concept that a friend and I are working on. He designed a version that uses a vane pump like you are describing. It is still a theoretical device but my friend, Dan Helgerson, an educator, has dedicated a lot of time trying to bring the concept some attention in the industry.

If it is the same type of device, it is depicted near the generator motor in the schematic in this thread.

Looking at your diagram, it is very similar in that it is used as a variable displacement flow divider. I will show this to Dan.

Here is a youtube video where he describes the vane version, it begins at minute 35:45

He describes the concept in many of the recent articles that he has posted on his website: www.danhelgerson.com , particularly the one titled, "Transformation Complete".
 
  • #31
Jon Richfield said:
If anyone could tell me how to include the image more conveniently, feel welcome.

First, save the image on your own PC. Then use the UPLOAD button to insert it into a post.
 
  • #32
anorlunda said:
First, save the image on your own PC. Then use the UPLOAD button to insert it into a post.

You are a staff member, you may have an upload button but I don't believe that we do. I have to use imgbb.com to post a picture URL.
 
  • #33
deckart said:
You are a staff member, you may have an upload button but I don't believe that we do. I have to use imgbb.com to post a picture URL.

Here is a screen shot. Bottom right are buttons labeled POST REPLY and PREVIEW and UPLOAD. After it is uploaded, new buttona appear. Position the cursor to where you want to insert it and click FULL SCREEN. Note that this works with pictures stored on your PC (JPG, BMP, PNG, GIF, ...) , not a URL.

slask.png
 

Attachments

  • slask.png
    slask.png
    26.3 KB · Views: 672
  • Like
Likes deckart
  • #34
anorlunda said:
Here is a screen shot. Bottom right are buttons labeled POST REPLY and PREVIEW and UPLOAD. After it is uploaded, new buttona appear. Position the cursor to where you want to insert it and click FULL SCREEN. Note that this works with pictures stored on your PC (JPG, BMP, PNG, GIF, ...) , not a URL.

View attachment 223143

That's why we couldn't see it, it was right in front of us. :)
 
  • Like
Likes anorlunda
  • #35
anorlunda said:
First, save the image on your own PC. Then use the UPLOAD button to insert it into a post.
Thanks anorlunda, let's see whether this works for me (thought I had tried that, but maybe I boobed :wink: )
Here goes: Ah. that worked. Maybe the previous time I didn't wait long enough. Thank you. I'll try to remember that, and try first to reduce the file size in case that contributed to the problem.
VaneGear2.jpg
 

Attachments

  • VaneGear2.jpg
    VaneGear2.jpg
    21.1 KB · Views: 328

Similar threads

  • General Engineering
Replies
33
Views
5K
  • General Engineering
Replies
7
Views
2K
  • General Engineering
Replies
13
Views
40K
  • General Engineering
Replies
11
Views
7K
Replies
13
Views
4K
Replies
1
Views
4K
  • Introductory Physics Homework Help
Replies
10
Views
2K
  • Electrical Engineering
Replies
4
Views
2K
  • Other Physics Topics
Replies
4
Views
1K
  • General Engineering
Replies
4
Views
2K
Back
Top