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Author Topic: REA - Regenerative Electric Airplane  (Read 1882 times)

Jay Sadie

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REA - Regenerative Electric Airplane
« on: October 04, 2011, 05:57:24 PM »

REA Napkin Sketch
REA Napkin Sketch
REA (Regenerative Electric Airplane) is a new idea I have for creating an airplane that flies on electric power only, while charging itself during flight… no carbon-based fuels required.

The airplane’s energy source is a set of lithium-ion battery packs that is initially charged by a fast-charger, taking approximately 3 hours to achieve a full charge. REA's power-plant consists of 5 independent 45 kW (60 hp) brushless light-weight electric motors, each directly driving one of 5 rotating ducted blade-fan assemblies. These motors also serve as turbine generators when switched to this mode by the on-board computer system.

What is a Ducted Fan? Essentially a ducted fan is a shrouded propeller, designed in a way that will improve propulsive efficiency and reduce noise. By reducing propeller blade tip losses and directing its thrust towards the back only, the ducted fan is more efficient in producing thrust than a conventional propeller, especially at higher rotational speeds. By sizing the ductwork appropriately, the designer can adjust the air velocity through the fan to allow it to operate more efficiently at higher air speeds than a propeller would. For the same static thrust, a ducted fan has a smaller diameter than a free propeller. Ducted fans are quieter than propellers: they shield the blade noise, and reduce the tip speed and intensity of the tip vortices both of which contribute to noise production.

Electric Ducted Fan
Electric Ducted Fan
The beauty about REA is that once it is airborne it recharges its batteries in 4 different ways:

  • 1) Via thin-film photo-voltaic cells attached to the top of the wings and fuselage.
  • 2) By means of thermal updrafts found naturally in nature.
  • 3) Utilizing airflow over and under the wings while in flight.
  • 4) Making use of the thermoelectric effect as a result of temperature differences during flight.

Let’s discuss each charge option in more detail.

1. Solar Power

Solar cells are becoming more effective and lighter day by day. An airplane has a large surface exposed to the sun’s rays in flight. This obviously only works during daytime with not too much cloud cover.

Photovoltaic [PV] energy harvesting wireless technology offers significant advantages over wired or solely battery-powered sensor solutions: virtually inexhaustible sources of power with little or no adverse environmental effects. Indoor PV harvesting solutions have to date been powered by specially tuned amorphous silicon (aSi)a technology most used in Solar Calculators. In recent years new PV technologies have come to the forefront in Energy Harvesting such as Dye Sensitized Solar Cells DSSC. The dyes absorbs light much like chlorophyll does in plants. Electrons released on impact escape to the layer of TiO2 and from there diffuse, through the electrolyte, as the dye can be tuned to the visible spectrum much higher power can be produced. At 200 lux DSSC can provide over 15 micro watts per cm2.

2. Thermal Updrafts

REA has 5 computer-controlled ducted fans, 4 of which are embedded in the wings, and 1 at the rear of the airplane, between V-shaped tail fins. All these fans can tilt around a 360 degree axis, and each of the fan blades (propellers) can change pitch to maximize or minimize the angle at which the fans strike the air. By making the pitch zero degrees it acts as a regular surface where no air will flow through the blades, acting like a regular wing surface if the tilt of the rotating fan casing is set level with the wings (horizontal).

When the fans are set at the required angle thermal updrafts will pass through two, four, or all 5 fans, generating electricity as is done with regular wind turbines.

3. Wind Power

During flight, and especially during descent, a lot of air flows over the wing surfaces and fuselage of an airplane. This energy is lost into thin air. However, REA will automatically tilt the fans at the required angles and blade pitches to capitalize on this abundant energy. Think of it as the same method applied by electric motor vehicles when you apply brakes and the kinetic energy lost when slowing a moving object down is transferred to the batteries.

4. Thermoelectric Power

The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice-versa. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference. At the atomic scale, an applied temperature gradient causes charged carriers in the material to diffuse from the hot side to the cold side, similar to a classical gas that expands when heated; hence inducing a thermal current.

As a plane changes altitude it can experience large differences in temperature. By utilizing lightweight gasses and materials that can very quickly absorb or release heat, this drop and rise of temperature between the inner and outer skin of the holding tank can be used to generate electricity.

The Seebeck effect is the conversion of temperature differences directly into electricity and is named for German physicist Thomas Johann Seebeck, who, in 1821 discovered that a compass needle would be deflected by a closed loop formed by two metals joined in two places, with a temperature difference between the junctions. This was because the metals responded differently to the temperature difference, creating a current loop and a magnetic field. Seebeck did not recognize there was an electric current involved, so he called the phenomenon the thermomagnetic effect. Danish physicist Hans Christian Ørsted rectified the mistake and coined the term "thermoelectricity". The voltage created by this effect is on the order of several microvolts per kelvin difference. One such combination, copper-constantan, has a Seebeck coefficient of 41 microvolts per kelvin at room temperature

A possible 5th source of power… Ambient-radiation sources

Solar Radiation Spectrum
Solar Radiation Spectrum
A possible source of energy comes from ubiquitous radio transmitters. Historically, either a large collection area or close proximity to the radiating wireless energy source is needed to get useful power levels from this source. The nantenna (nanoantenna) is a nanoscopic rectifying antenna, and is one proposed development which would overcome this limitation by making use of the abundant natural radiation (such as solar radiation).

One idea is to deliberately broadcast RF energy to power remote devices: This is now commonplace in passive Radio Frequency Identification (RFID) systems, but the Safety and US Federal Communications Commission (and equivalent bodies worldwide) limit the maximum power that can be transmitted this way.

General

In order to prove the viability of REA a double-seater must be built as the first prototype. It is important to prove that the airplane is feasible for multiple passengers.

Although REA may resemble a glider it is not a glider. REA has a full power source and can even take off and land vertically (VTOL airplane). To take off or land vertically will obviously consume a large amount of power. Therefore it is advisable to take off or land on a runway in the normal manner.

During takeoff the computer-controlled fans are tilted forward at a 90 degree angle to provide maximum thrust. Once airborne the on-board computers will automatically adjust the tilt to minimize the power required and to maximize the forward/up thrust, depending on the speed of climb required.

Although REA can be flown completely manually, with the on-board computer disabled, it is advisable to let the computer assist the pilot. It will make thousands of calculations per second to ensure optimum power usage, something that is impossible for a human to do. The pilot still makes all the decisions on rate of climb or descent, turning angles, etc. The on-board computer “senses” the pilot’s intentions and merely calculates the optimum angles and pitches.

The on-board computer will also sense the strength of potential thermal updrafts and will make the necessary adjustments to capitalize on such updrafts, without sacrificing performance. It will delicately balance the external power sources available with the intentions of the pilot. The on-board computer will also control the thermoelectric effect by measuring the difference in air temperature during flight, making optimum use of this free form of energy provided by nature.

During descent the on-board computer will optimize the drag needed to slow down the airplane by turning the fans into the onrushing air and adjusting the tilt of the blades. In such a case the fans are used as air brakes as well as wind turbines.

Benefits

The biggest benefit of REA is that it makes use of multiple forms of energy, thereby not relying on one form only. At least one of the power generating features will be available at all times. With careful planning and pilot skills there is no reason why REA cannot stay in flight indefinitely. This may be a bold statement, but as technology improves and with the correct on-board computing power it is totally possible.

No runway required, even though it will drain the batteries during VTOL. However, it is nice to know that this is an option. A good example of where this can be useful is for landing on top of an escarpment or mountain. When taking off after a vertical landing the batteries can be recharged by thermal updrafts found at high altitudes. Also, as battery technology improves the VTOL capabilities of REA will become increasingly practical.

Low operating and maintenance costs. The advantages of induction motors: no brushes or commutator means easier manufacture, no wear, no sparks, no ozone production and none of the energy loss associated with them. 1,000+ moving parts in a combustion engine. Four in an electric motor. Electric motors are built to last decades, not years.

Almost zero noise pollution. The only sound produced by the airplane is that of the tips of the blades when spinning at high revolution. With computer-controlled pitch-control and the shielding ductwork around the propellers even this noise can be dramatically reduced.

Summary

REA is just an idea at the moment. It may seem like a Loopy Idea at first, but with careful consideration and deeper scrutiny it will become obvious that the idea is not so far out of the ordinary. I am of the firm belief that Electric Aircraft will be part of our near future. They are quiet, green and efficient… and most importantly very affordable when it comes to maintenance. Anyone who has ever bought a traditional airplane will vouch to the fact the cheapest part of owning an airplane is buying the airplane.

Flight schools will welcome REA as a trainer. It will drop the hourly operational costs and rates to a point where almost anyone will be able to afford a private pilot license.

If you’re interested in getting involved with this project then please contact me here.


For more of my own personal ideas please click here...
« Last Edit: October 05, 2011, 02:38:31 PM by Jay Sadie »
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"I do not think there is any thrill that can go through the human heart like that felt by the inventor as he sees some creation of the brain unfolding to success." - Nikola Tesla
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