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Latent Power Turbines(TM)

 Patent application Nos. GB1418029.3  GB 0807276.1,  0618171.3,  0903879.5

 

 

A Latent Power Turbine is a heat engine inside a mechanical engine.

  

The laws of thermodynamics prevent heat engines from being 100% thermally efficient, with typical efficiencies ranging from 30% to 50%, depending on the type of engine.

We have solved this low efficiency problem by placing our heat engine inside a heat recycling mechanical engine.

Recycling is not a realistic option with existing heat engines because they rely on the working gas or steam expanding to increase its speed, to drive the turbine.

We speed up our working fluid (atmospheric air) in a different way. As you can see in the photograph, the metal conduit is tapered so that the working air accelerates before it enters the heat engine.

In order for the law of conservation of energy to be obeyed, the air must cool as it speeds up. However, because the air enters the tapered section at room temperature, the heat engine is forced to operate at a slightly lower temperature than the laboratory air. This feature is unique to LP Turbines and will be counter-intuitive to most engineers.

Here is a second counter-intuitive design feature:

Heat is drawn in through the metal conduit walls, in the manner of a heat pump. This allows thermal energy in the laboratory air to be used as the fuel for the heat engine.
The price to be paid for these benefits is that Latent Power Turbines are more bulky than other power station heat engines.

  

Acnowlegements
Innovate UK funded our early research at Lancaster University. We then went on to win 98,400 additional Innovate UK funding to test our deigns on a larger scale.

 

This is a summary of the novel features of our design:

Figure 1 The turbo-generator manufactures electricity and the fan consumes some of it. However, the air travels faster through the turbine than through the fan.

[For our prototype the air speed increases by a factor of 3, so its kinetic energy increases by a factor of 9.]

This allows the generator to produce a surplus of electricity, with the balance of energy to keep the system running, being heat drawn in from the atmosphere.

 

The temperature drop across the heat engine is very small compared with existing power station turbines, so its thermal efficiency is also corresponding small.
As you can see from the comparative diagrams below, this is not a design problem, because the exhaust heat is recycled.

 

 

  

Figure 2 The internal heat engine of an LP Turbine has a very low thermal efficiency. But, thanks to recycling, the external mechanical engine acts like a very efficient heat engine.

 

Figure 3. Our world is dominated by heat engines that have high input temperatures.
This has lead to the intuitive belief that high input temperatures are an essential design requirement.
But this requirement breaks down if the rejected heat can be recycled.

 

 

Figure 4. In our work to date, we have used this test rig to verify the basic LP Turbine theory.

Here is a summary of our results:

Figure 5. The changes in temperature and pressure around the loop were in line with our predictions.

In order to check that our experimental results were not a fluke, we repeated the experiments over a number of days using different fan speeds.

We also built an environmental chamber around the converging-diverging zone and used an electrical heating system to alter the 'laboratory' air temperature. The results were always in line with our expectations.
[Final Report for Innovate UK (Technology Strategy Board) Project 131512.]

However, we did not have sufficient funds to commission the design and construction of a bespoke turbine. Instead, we had to improvise, using a cannibalised set of air conditioning unit fan blades. These had entirely the wrong shape, producing a lot of turbulence and preventing a net output of power.

Figure 6. Our improvised turbine rotor had entirely the wrong shape to deliver a net power output. Instead, it created a large resistance to the air flow.

  

Using a correctly designed rotor for our next round of research, we predict that the following formula will link the power output from the turbine and the power input to the fan:

Poweroutput = (n2-1) x (Powerinto fan - Energy consumed/second overcoming drag and other losses)

Where n is the constriction ratio. For example, for our test rig, the air speed increases by a factor of 3 as it passes through the constriction. So n = 3.
The square term appears because the kinetic energy of the moving air depends on the square of its speed.

 

Likely commercial products

Large commercial LP Turbines could take the form of a daisy chain of alternate turbo-generators and fans.

 

Figure 7. This is one of the daisy chain loops described in our patent literature.

However, for domestic and small business purposes, the following plenum chamber design will be more convenient.

 

 

Figure 8. We envisage that the small (approx. 12 kW) Latent Power Turbine for domestic and small business use will completely different to our research prototype.

Estimating a retail price
Mechanically and electrically, this design will be no more complex than a domestic washing machine.

The construction materials required will probably be equivalent to those required for two washing machines, giving us a an estimated retail cost of about 600.

Finding out more

1    Details of the many ways in which LP Turbines could change our society can be found on this linked page.

2    More detailed technical information is provided on this page. If you need more information, please contact us.

3   To avoid technical overload, we have omitted some details from our website. If you need further information, please get in contact with us.

  

APPENDIX

This appendix may be of interest to engineers familiar with the laws of thermodynamics.

A1 LP Turbines and the Carnot equation

Figure 8 below explains how a Latent Power Turbine can have a very low Carnot efficiency, yet have a very high efficiency in converting heat into useful work.

  

  

Figure 9. Latent Power Turbines have two novel design features that give them surprising properties.

(i) They incorporate a thermal feedback loop.

(ii) They can run at a lower temperature than the laboratory air.

 

A2 Treating an LP Turbine as a pair of nested black boxes

The black box approach provides another way of understanding how a Latent Power Turbine can appear to be 100% thermally efficient, without violating the laws of thermodynamics.

The internal black box is a heat engine that must be consistent with standard heat engine theory. That is, it must posse a hot reservoir and a cold reservoir with some of the heat being rejected into the cold reservoir.

The external black box is a heat recycling system. It can only recycle the heat and add extra 'top-up heat' because a converging-diverging system is used to ensure that the hot reservoir is always at a lower temperature than the surrounding laboratory air.

 

 

Figure 10. A black box representation of a heat engine inside a mechanical engine.

This representation is only valid because the hot reservoir is below laboratory temperature, with the cold reservoir being at an even lower temperature.