Pitch
As advances in technology have progressed, could there be at least one idea that was overlooked in the past ?
Description
Summary
This proposal is centred on the possibility that what has been found through several years of independent research could be applied to electricity generating equipment on a global scale. As such it is a practical fix which bypasses the need for verbal, often violated, agreements between disparate organisations.
The idea originated from the consideration that a large proportion of the input energy expended to generate electrical current is required merely to overcome the magnetic interaction between a generator’s rotor and stator.
That being the case, it seemed implausible that the magnetic effect could not be imitated externally, in reverse, in order to minimise the required input effort.
What actions do you propose?
The actions involve retrofitting electrical generators with hardware designed to reduce the input work required to be expended by the associated turbine.
If this was done then technologies such as, say, hydrogen could be made cost effective to the extent that such a medium could become a basis for future power generation and storage.
The principles of a method of implementing such a cost reduction can be demonstrated with the aid of an existing proof-of-concept rig. Scaling those principles up would be one first practical step to ameliorating climate change. Maybe a small step, but hopefully significant.
Following on from this, the methodology could be exported to most generating equipment in existence. Creating a new market in this way would obviously encourage new business opportunities. Business would profit and at the same time environmental improvements would naturally occur.
Generator types vary in terms of size and geometry. All rely on electron movement caused by the application of flux sources on coil windings. All experience what could be considered as a braking effect caused by the magnetic interaction between the flux bearer and flux recipient. The aggregation of these individual brake points is generally referred to as “counter-torque”.
It has been found that there is a way of overcoming this braking by synchronising what might be termed equivalent force vectors with the peaks of the rotor brake points. The brake points are in turn synchronised with the generated EMF. Advantage is taken from the fact that the resulting current, when flowing through inductors, is always lagging. The equivalent force vectors can be timed to occur at the peaks of the next generated electrical cycle.
Before a generator’s output is dissipated, either directly or via a transmission system, it is possible to re-use that same output to produce current pulses causing associated inductors to act, momentarily, as electromagnets. If the polarity of the electromagnets’ application area matches that of other flux sources mounted on the associated generator’s shaft then the action of repulsion provides the force required to reduce the braking.
The electrical cost of this action is low because it makes use of a natural phenomenon that is unique to inductors i.e. the storage of electrical current for 90°, during which time a charged particle cloud is created around the inductor, this being a property of magnetic fields in general. One other negligible cost is incurred, that of a delay of generated power delivery of 360°.
The pulse stream is composed of, simply, the half-waves of the generated current. The pulses are required to be of similar electrical polarity so a simple full wave rectifier is employed. Each pulse has to be present at the time of the next generated brake point peak so it is necessary to employ two inductors through which a half-wave propagates with a total delay of 180°. If there was only one inductor, the pulse would always be too early to synchronise with the next generated half-wave.
This action occurs for each full electrical cycle i.e. 360°, so two sets of inductor pairs are used on both the left and right branches of the full wave rectifier.
Only the second in the sets of two inductors is actually used to force the generator rotor over the brake points.
The first is used only as a delay mechanism so its size can be minimised; the size of the second can be maximised by the same proportion. Because we are effectively mimicking the effect of the generator’s stator on the rotor (in reverse), the flux density between the compensator fixed coils and flux source(s) at the time of generation has to match.
The proof-of-concept uses air-cored coils and a geometry which emulates a 4-pole salient pole machine. Permanent magnets are used for both the generator and compensator rotors. As in any electrical generator, the generator magnets affect the stator coil; conversely, the compensator magnets are affected (repelled) by the compensator coils.
In a scaled up version, the compensator would have a wound rotor and be excited in a similar fashion to the generator rotor. Whatever flux concentrating mechanism in use on the generator would apply to the compensator also.
To give the reader some idea of what scaling up would entail, a rough analogy could be made by considering the generator and compensator as two generators. For purely illustrative purposes, consider the two generators as single phase, two pole salient rotor types. Both have two major windings on the stator and the drive-shafts are connected together. The second generator is the compensator. The first is driven by a turbine and its two stator coils are wired in series, the endpoints of which are connected to a full wave rectifier. Note that this is not unlike any offshore renewable device as power has to be transferred in DC form due the capacitive effects of seawater surrounding cables.
The rectifier’s left and right branches each have a minimised inductor and one of the second generator’s windings in series with them.
In this scenario, no compensation will occur for two reasons:
1. The compensator’s stator is wrongly configured.
2. There are two rotor shoes on the compensator; we only need one shoe affected by two coils per 360°. A non-magnetic counterbalance would replace the missing shoe.
If it is assumed that the generator and compensator rotor shoe arcs are 90° long around the stator internal circumference what would cause it to work is:
1. Rewinding the second generator’s stator such that the winding areas match the area of a rotor shoe.
2. Removing one shoe from the second generator, adding a counterbalance and doubling the compensator rotor windings.
As in the proof-of-concept, the location of the compensator’s windings would be at a point slightly offset from the driven generator’s zero crossing points, spaced 180° apart.
A first-fit design of components for both single and three-phase machines has been completed. Several optimisations and tradeoffs are possible and, given the fact that professionals within the generator design world know far more about generator construction than this proposal’s originator, it is likely that many enhancements could be made.
As an aside, a rough analogy of what has been found might be the mechanics of a game called “swing-ball”. There are two players, each holding a bat, with the intention of hitting a ball suspended on a rope in such a way that the two actions are synchronised. The perfect scenario is when the rope is horizontal.
Conceptually, if the bats are replaced by coils and the ball is replaced by flux sources mounted on the generator shaft then, when the current pulses are synchronised, the generator rotor is forced over the brake points maximally.
Proof of concept Specifics
Included in the reference section are 5 images.
Image 2 is a view of the front elevation of the test rig. There are two sets of magnets mounted on two plates which spin on a single shaft. The lower plate holds 4 equidistantly spaced magnets and is effectively a 4-pole salient pole rotor. Each magnet in turn affects the single stator coil shown at the base.
The upper plate is the compensator rotor. It holds 8 compensator magnets which are geometrically in line with those on the generator. Only 4 of these are used. Above the compensator rotor are 2 fixed compensator coils. The flux pulses occurring as a result of the current flowing in those coils are referred to as P2 and P4 in the composite diagram, Image 1.
The output from the stator coil is routed to a full wave rectifier which has 2 coils in series on both the left hand (LH 90° and 180°, p1 & p2) and right hand (RH 90° and 180°, p3 & p4) branches. p1 and p3 are used only to contribute to the current lag needed for pulse synchronisation. They can therefore be reduced in size to the minimum definition of a coil. The coils p2 and p4 are increased in size by the same proportion.
Images 3 to 5, taken as a set, illustrate precisely what happens as a result of the application of the pulses p2 and p4.
Each compensator coil has one half of the windings and one half the diameter of the stator. Halving the diameter quartiles the area. In addition, the compensation magnets are a quartile of the generator magnets but twice the thickness which means that the flux is half that of the generator poles.
Image 3 shows the left hand compensation coil positioned exactly over one of the compensation magnets. If the coil current has risen in a time shorter or matching the time taken for the magnet to transition from the start of the coil boundary to the position shown, and the magnetic polarities match, then the compensation coil is unaffected.
During the transition, the coil flux has built up in a compressed state and, as a consequence, as the compensation magnet moves away from the coil the compressed flux expands. As implied by the test results, the rotor is assisted over the effect that the stator has on it.
Image 4 shows the state immediately after the flux expansion. The magnet has cleared the left hand coil. The next stage in the sequence is that a compensation magnet encroaches onto the right hand coil but, as it does so, a similar current rise in a time matching or exceeding the encroachment occurs within it.
Image 5 shows the state after the next expansion. This propels the compensation magnet such that the generator rotor is again assisted as it moves onto the stator.
Implementing what is effectively a delay in half-waves could be thought of as a buffer. It may be easier to appreciate what is going on if the compensation process is considered to be one translating AC to DC, compensating at the DC level then giving the option to retain the output at the DC level (for instance to power electrolysers) or to reinstate the output to AC.
Snapshot of the proof-of-concept test results and deficiencies as at 4-May-2013
Angular velocity (av) units measured in KHz, sourced from a photodiode, 8 pulses per physical revolution, translated to rpm e.g. .100 KHz = 100Hz / 8 * 60 = 750 rpm.
4 generator rotor poles at 750rpm = 3000 rpm = 50Hz.
Mechanical only (MO) av .134 (unloaded, just spinning)
Loaded, not mounted(LNM) av .108 1.95Vpeak (slows, now supplying current)
2 comp coils, loaded and mounted(LM) av .120 2.2Vpeak (prime mover has less work to do)
Note that the angular velocity AND volts increase.
MO – LNM = .134 - .108 = 26. (normalised)
LM – LNM = .120 - .108 = 12.
Compensation speed increment = 12 / 26 = 46.15%.
Half possible compensation applied due to the use of only one end (half area) of compensation coils, therefore total speed increment possible = 2 x 46.15%.
The rig is driven by a brushed DC motor supplied via a fixed frequency PWM. A DVM is connected in series. The reading from the DVM is therefore only an indicator as the actual input depends on the duty cycle.
DVM reading for LNM = .22.
DVM reading after LM speed reduced to LNM speed = 0.06, difference = 0.16.
0.16 / 0.22 = 73% which is incorrect. Better instrumentation would enable determination as to whether the PWM duty cycle reduction matches the angular velocity increment. As far as can be determined by inspection (using an oscilloscope trace), this would appear to be the case.
Who will take these actions?
The natural take-up of a retrofit device which predominantly saves the very energy required to produce a commodity which is now relied upon for global survival would inevitably encourage actions throughout the global community.
Specifically, there are various means of increasing efficiency in conventional plant. In particular, CCGT plants have a thermal efficiency of around 60%. Operators of these plants are therefore effectively wasting, in efficiency terms, 40% of the input energy. Assuming a mid-point efficiency increment due to counter torque compensation of 60%, then 60% x 40% = 24% which when added to the current 60% efficiency is an up-rating to 84%.
The original efficiency increment of 70% maximum was derived from a possible 90%+ and de-rated due to expected frictional and magnetic losses. As evidenced by NASA in their FES project, frictional losses can be reduced by replacing conventional with permanent magnet bearings (suitably supported by superconductor guides) and wind turbulence losses attenuated by running the driven component in a vacuum.
As a purely speculative observation, if the figures used to de-rate the compensated generator were removed, what could be possible?. The start of a hydrogen economy ?
Where will these actions be taken?
This proposal could be considered in the context of other energy efficiency efforts except for being different to the extent that most energy efficiency projects are devoted to reducing power requirements in order to save energy. The project contained in this proposal seeks to improve the efficiency of the conversion of energy to power.
This suggests that most actions will be taken within an engineering context on a per-machine basis. Eventually, in the context of duplication and roll-out worldwide, those actions should start to make improvements globally.
The following is a possible high level action plan outline:
Laboratory proof-of-concept verification.
Prototype build, testing against uncompensated generator.
Selected generator, full size build, field test ; at the same time investigate inclusion of friction reduction technology currently in use at NASA.
At this stage, could consider a single device containing an integral counter-torque compensator.
Document design, deal with demonstrations, organise manufacturing licenses.
Investigate hydrocarbon to hydrogen possibilities.
Investigate advantages and build requirements for inclusion of counter torque compensation in renewable devices.
How much will emissions be reduced or sequestered vs. business as usual levels?
A scaled up version would incur extra frictional losses caused by the addition of a second rotor and given that all flux sources will be electromagnets, other magnetic losses would be likely.
Given the proof-of concept test results, although limited, the likely-hood is that input power reduction would be greater than 50%, possibly as high as 70%. This is a very rough estimate but, given that we have as much power to offset the braking as is produced by the associated generator we are affecting, it would appear reasonable.
We know that emissions are proportional to input power, therefore for the two percentages given above the following table, according to DOE / EPA inventories, can be drawn:
Units are Million Metric Tons CO2 equivalent
50% 70%
Electricity Generation >1000 >1400
Industrial Indirect Emission >250 >350
What are other key benefits?
There are obvious improvements across both the fossil fuel and renewable energy sectors.
Other benefits are maybe not so obvious. In general, the energy required to complete tasks which would otherwise be too expensive to contemplate is minimised. The following list is not exhaustive:
Desalination / water reclamation.
Gasification of waste.
Geo-engineering facilities e.g. CO2 extraction/sequestration and ocean de-acidification. In a related area there are on-going projects seeking to profitably use CO2. Counter-torque compensators would be beneficial in those areas.
New generation possibilities are opened up given a step-change in efficiency. Local domestic power generation could become a reality when considered matched with other projects. One such project in progress today builds on the flywheel energy storage system, the output of which would be considerably improved if a counter-torque compensator was integral to it.
What are the proposal’s costs?
Prototype – one-off cost
Prototype production – single phase – minimal cost to verify scalable – parts only
Not greater than $10K, existing generator with extended shaft with basic compensation, machine costs low, simple design (which exists).
A small generator for the purpose costs around $2K.
Engineering design – cost per generator type
One-off engineering design cost of 5 x generator cost, given that specific generators have wide ranging variations in geometry and size.
An alternative is the design and implementation of a combined generator and counter torque compensator. This could make use of the non salient pole design with the intention of using multiple units to replace the monolithic design currently driven by high pressure, high temperature steam-fed turbines.
Production – cost per generator implementation
The compensator real-estate and footprint will be approximately that of the generator.
Components are new windings, custom rotor(s), shaft connection and new wiring. I approximate the cost of compensation to be 1.5 times the cost of the generator initially, reducing to 1 x cost when in production.
Time line
The advantage of implementing the solution described is that the time line can be varied depending upon the urgency of the requirement for a solution.
Related proposals
Electrical Power Sector/Re-use of Generated Electrical Current to Magnetically Assist the Turbine
Geoengineering/Scaling up of CO2 Scrubbing Technologies
Transportation Efficiency/Large Solutions Need Large Funding
References
Image 1 - Composite Diagram
Image 2 Front Elevation of Test Rig
Image 3 - Sequence 1 of 3
Image 4 - Sequence 2 of 3
Image 5 - Sequence 3 of 3
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