The present disclosure relates generally to transport structures, and more specifically to lightweight, aerodynamically-contoured vehicles that use solar panels for extending vehicle range.
Until recently, producers of automobiles and other transport structures were constrained to rely on the process of “machining” often heavy and dense metallic materials to produce essential vehicle components.
With the increased popularity of additive manufacturing (“AM”), also called 3-D printing, parts once created exclusively by machining and other subtractive processes may now be cost-effectively 3-D printed as metals, plastics, and sophisticated components using strong, lightweight composite materials such as carbon fiber. Using additive manufacturing, vehicle parts including the chassis and body panels can be more easily made using any number of lighter composite materials to produce an overall lighter, more sophisticated, more reliable and more streamlined vehicle having a larger number of features at lower costs.
In recognition of the advantages associated with the use of AM to complement conventional machining techniques in the automotive industry, a new line of vehicles has been proposed to exploit new technology arenas. One such arena involves the efficient use of solar energy in transportation. Conventional approaches to developing solar-powered cars have been circumscribed by practical limitations including, for example, the inability to harness adequate amounts of solar energy given the energy demands of conventional solar vehicles.
Attempts have been made to use solar power to augment, rather than replace, gas or electric driven systems, but here again, any benefit from the solar harnessing attempts has been cancelled out by the excessive mass and drag associated with the vehicle. Even for lighter vehicles, conventional approaches involve vehicles covered with large numbers of static solar panels mounted to the vehicle, where the capacity of the panels to receive energy is limited by the angle of solar rays. Moreover, each such solar panel on the static array contributes to the overall mass of the vehicle, and ultimately reduces any benefit of solar absorption.
The solar vehicle described hereinbelow, and the structures and assemblies that include it, represent a solution to these and other longstanding problems.
Several aspects of solar-powered extended range vehicles, structures and assemblies used in these vehicles, and techniques for additively manufacturing such structures and assemblies will be described more fully hereinafter with reference to various illustrative aspects of the present disclosure.
In one aspect of the present disclosure, a solar extended-range vehicle includes an aerodynamically-contoured frame coupled to an exterior structure, a suspension system mounted to the exterior structure and coupled to a wheel system, at least one electric motor coupled to the wheel system, and at least one stowable solar panel arranged along a region of the frame for supplying power to the electric motor.
In another aspect of the present disclosure, a solar extended range electric vehicle includes a frame coupled to an exterior structure, a suspension system mounted on the exterior structure, an impact structure arranged near a front of the frame and coupled to the suspension system, a wheel system coupled to the suspension system, a plurality of electric motors coupled to the wheel system, and at least one stowable solar panel operably coupled to a battery assembly.
Different solar-powered extended range vehicles, structures and assembly techniques may be described that have not previously been developed or proposed. It will be understood that other aspects of these vehicles, structures and techniques will become readily apparent to those skilled in the art based on the following detailed description, wherein they are shown and described in only several embodiments by way of illustration. As will be appreciated by those skilled in the art, these vehicles, structures and techniques can be realized with other embodiments without departing from the spirit and scope of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.
Various solar-powered extended range vehicles, structures and assembly techniques will now be presented in the detailed description by way of example, and not by way of limitation, in the accompanying drawings, wherein:
The detailed description set forth below in connection with the drawings is intended to provide a description of exemplary embodiments of solar-powered extended range vehicles, structures and assemblies used in these vehicles, and techniques for additively manufacturing such structures and assemblies. The description is not intended to represent the only embodiments in which the invention may be practiced. The term “exemplary” used throughout this disclosure means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other embodiments presented in this disclosure. The detailed description includes specific details for the purpose of providing a thorough and complete disclosure that fully conveys the scope of the invention to those skilled in the art. However, the invention may be practiced without these specific details. In some instances, well-known structures and components may be shown in block diagram form, or omitted entirely, in order to avoid obscuring the various concepts presented throughout this disclosure.
Numerous types of AM exist. Most AM techniques involve creating a computer aided design (CAD) 3-D model of the part and use software to ‘slice’ the CAD model into a format having printer-readable instructions for building the part layer-by-layer (‘slice-by-slice’). The 3-D printer may be provided with the desired material(s) for use in 3-D printing the part pursuant to these instructions.
Depending on the printer technology such as powder bed fusion (PBF), in which PBF is a technology that itself incorporates various 3-D sub-classes of technology (including Selective Laser Melting (SLM), Selective Laser Sintering (SLS), Electron Beam Melting (EBM), Direct Metal Layer Sintering (DMLS), Selective Heat Sintering (SHS) and the like), the 3-D printer may include a powder bed for containing the powdered material from which the print material is sourced. The powdered material may be uniformly deposited layer-by-layer using a roller on a build plate. Armed with the 3-D printing instructions from the slicer operation, the controller circuit associated with the 3-D printer may illuminate a laser or electron beam onto a deflector. The deflector may cause the beam to focus on designated regions within that layer of deposited powder. The beam fuses or melts together the powder in the designated regions in the layer if so instructed by the slicer program, and ignores the remaining regions of powder in the layer. The 3-D printer repeats these tasks for designated regions in each deposited layer until the entire structure is rendered from the build plate up. Excess powder is collected from all the non-fused regions and the completed AM structure is removed from the printer, at which point the 3-D printer can be readied for reuse as desired.
In other AM techniques such as fused deposition modeling (FDM), the CAD file is used similarly and instructions are generated based on a sliced data model as before. However, in FDM, a material-injecting print extruder mounted to a gantry system is used in lieu of a laser or electron source. One or more reels of desired materials in filament form, typically a thermoplastic, is provided to the FDM printer. The filament is fed through a nozzle, heated up to condition it for printing, and extruded through the nozzle onto a region of the build plate dictated by the print software. That is, the FDM print extruder heats and extrudes the material onto selected regions associated with a layer and extrudes nothing at the remaining regions of the layer where nothing is to be printed. This practice is in contrast to PBF techniques, where powder is used to fill up the entire layer and then the desired regions of the layer are fused together. The FDM printer continues to perform this process layer-by-layer, until the structure is printed. Instead of actively being fused together by a laser or beam, the material in the FDM printer is configured to harden as it cools, either by itself or with an extruded adhesive. In both FDM and PBF techniques, if an area of overhang of the structure being printed (e.g., an upper portion of a hollow case) is subject to gravitational deformation or collapse prior to completion of the AM process, the 3-D printer may further print a section of “support material” which, while not necessarily part of the structure itself, serves to maintain the structural integrity of the thing being printed. After the combined structure dries and is removed from the 3-D printer, the support material may be carefully removed from the structural material using various techniques.
In one aspect of the present disclosure, a solar extended range electric vehicle is introduced. While the vehicle may itself have a plethora of styles and practical uses, the vehicle may in one exemplary embodiment be an all-weather commuting vehicle. The vehicle's range may also vary depending on a number of factors including mass, type and area to be driven, etc., the vehicle in one embodiment may be configured to have at least a 200-mile range on regulatory cycles, including an electrically charged engine and the solar range enhancement capabilities. Advantageously, in the embodiment shown, the vehicle need not compromise in other areas (e.g., features, comfort, performance or some combination thereof). More specifically, attributes such as comfort, stability, and impact protection properties of the vehicle may resemble those features of conventional passenger cars.
The 200-mile range may be made possible by the low demand energy of the vehicle, which can be less than 150 Watt hours per mile (W h/mi), and, as discussed below, by solar charging the battery, resulting in an extended range. Features that can enable both the low demand energy and the significant mileage provided by solar charging include, for example, the low mass of the vehicle, the low automotive coefficient of drag (Cd), and the low frontal area (A). These features may be achieved in one embodiment by (i) dual passenger inline seating which may result in an approximately 440 Kg curb mass, (ii) low frontal area and a high fineness ratio to achieve Cd. A (Coefficient of drag×area)=approximately 0.15 m2, and (iii) the smallest battery possible in view of the vehicle range and power, with approximately 20 kWh usable.
The excellent dynamics of the vehicle in these embodiments may be achieved, for example, using a high power-to-weight ratio and a high overturning moment. These features, in turn, may be realized by the following exemplary attributes: (i) a power of 80+kW due to vehicle motors and power electronics, (ii) all-wheel drive (AWD) for maximum power utilization (battery limited), (iii) a low center of gravity (CG) as a result of a strategically low battery placement and low seat height (described further below), and (iv) a narrow but non-zero track width, dynamic leaning, and full torque vectoring via wheel motors. It will be appreciated in other embodiments, that other attributes may employed, however, and may provide an equally suitable performance.
These and other features of the solar extended range electric vehicle are described in more detail with reference to the illustrations and explanations that follow.
Energy Efficiency Analysis.
This section presents data from the top-down in an energy efficiency analysis that was performed to enable an optimal and non-compromising design of the solar extended range electric vehicle. One purpose of this analysis was to determine test mass and Cd·A values of the vehicle that would yield a desired energy demand value of less than the chosen target of 150 Wh/mi. Survey of published battery electric vehicle (BEV) performance has shown that drive cycle energy consumption is a function of three terms: (i) coefficient of drag×Area (Cd×A), (ii) rolling resistance (which is a function of the vehicle mass) and (iii) Inertia forces (which are also a function of mass). Inertia forces are largely recoverable with regeneration techniques.
In short, Radiometric analysis of modern BEVs suggests that a test mass of approximately 510 kg and a coefficient of drag×area of approximately 0.12 m2 Cd×A should be targeted in the solar vehicle to achieve the desired energy output limit of <150 Wh/mi.
Solar Energy Analysis.
SA solar energy analysis was performed to determine the design and location of the solar panels on the solar energy range extended vehicle. Table I illustrates the result of that analysis:
Solar energy conversion efficiency and vehicle energy demand will likely improve over time. It should be noted that, while values of almost 16 miles daily range based solely on solar power have been achieved, that value is expected to increase further based on the various teachings in this disclosure and other factors.
In addition, two solar panels 106 may be located on either side of the tail in a deployable array, which in this embodiment is a total area of three square meters. Solar panels 106 may provide sufficient energy for tasks like commuting and when folded or stowed to their original position, low drag. Additional solar panels 108 beneath primary array of solar panels 106 can provide additional energy when the sun is low in the sky with the vehicle oriented mostly along the North-South direction. Two-axis solar tracking can improve Array Effectiveness by a multiple in the range of 1.3-1.8.
In an embodiment, the aerodynamic contour of the body as shown in the illustrations above assists not only in reducing the coefficient of drag overall, but also for enabling one of a dynamic leaning narrow track or a non-tilting wide track vehicle for turns.
The following portions of the specification discuss further benefits of the solar extended range electric vehicle, some of which were addressed in connection with
Enabling Practical Use of Solar Vehicles.
Personal transportation optimally uses minimal energy. However, transportation based entirely on solar electric power, which would result in very low vehicle energy consumption, is not presently feasible in passenger vehicles due to current practical limitations of solar panels. Thus, one solution as disclosed herein is to provide an electric vehicle which uses solar energy efficiently to extend overall range. In such an electric vehicle. the lowest energy consumption may result from minimizing mass (e.g., vehicle mass) and parasitic energy loss due to drag.
An electric vehicle with motor/generators may recover vehicle kinetic energy under braking. For example, a regenerative brake is an energy recovery mechanism which slows a vehicle or object by converting its kinetic energy into a form which can be either used immediately or stored until needed. A typical regenerative brake involves using an electric motor as an electric generator. Vehicles propelled by electric motors, such as the solar extended range electrical vehicle disclosed herein, use the motors as generators when using regenerative braking such that the act of braking can transfer mechanical energy from the wheels to electrical energy which in turn is used to power the vehicle. Thus, in an automated regenerative braking system, the vehicle's control system may automatically initiate battery charging when the brakes are applied. Regenerative braking systems consequently enable the vehicle to recover some of the associated kinetic energy loss.
The next major loss is aerodynamic drag which increases with the product of drag coefficient and frontal area. The drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. A lower drag coefficient generally indicates that the vehicle at issue has less aerodynamic drag. For example, the drag equation states:
From the above equation it is evident that the drag force FD is proportional to the drag coefficient CD, such that the drag force on the vehicle decreases with a lower CD.
A fineness ratio of 3:1 or greater may be used to minimize the aerodynamic drag coefficient CD. Fineness ratio is the ratio of the length of a body to its maximum width. This ratio can be used in the solar extended range electric vehicle to reduce drag, while simultaneously providing the passengers with a suitable environmental enclosure.
The frontal area is a function of the projected cross sectional area in the direction of travel. Upright passenger seating and visibility constraints increase roof height and consequently frontal area. Accordingly, to combat drag due to frontal area in an embodiment, vehicle width is minimized for lowest frontal area. Specifically, in one embodiment, inline passenger seating is used. Inline passenger seating increases a number of available seats without increasing frontal area. In other single-passenger embodiments, a single driver seat having a carefully controlled width may be provided.
In addition to the above considerations, the vehicle may include accommodation for static stability. Static stability is the ability of a body to remain upright when at rest, or under acceleration and deceleration. Static stability is a requirement that extends to fully enclosed passenger vehicles. One solution to achieving static stability is to provide a tricycle or quadricycle wheel system with the center of gravity located between the wheels both laterally and longitudinally. Narrow track vehicles with static stability will have reduced overturning moment due to the narrow track width. Dynamic leaning while cornering reduces overturning moment by aligning the inertial force vector with the center of the track. In an embodiment, a quadricycle wheel system 110 (
In an embodiment, inline seating 104 (
In another embodiment, the vehicle may use straddle seating with foot controls minimized. For example, one or more functions ordinarily controlled using foot controls may be instead controlled using alternative hand-accessible controls. Alternatively or in addition, a size of the foot controls may be minimized and more spread out among the available area proximate the driver's foot position. The minimization of foot controls may advantageously allow battery placement of battery cells 122 (
In an embodiment, as shown in
While the above-described configuration yields a vehicle architecture consistent with the present disclosure, it will be appreciated that numerous modifications to the vehicle may be made while preserving its energy efficient, drag-resistant nature. As such, the configurations and embodiments described above are exemplary in nature and are not intended to limit the scope of the present invention to these particular embodiments.
Aerodynamic Body for Narrow Track Vehicle.
A fundamentally low aerodynamic drag shape will minimize pressure drag and form (i.e., friction) drag simultaneously. Pressure drag may be minimized through the use of gradual transitions in cross-section such that the volume of fluid displaced per increment of vehicle length is lowest. This gradual cross-section change is called ‘area-ruling’, which in three dimensions may be most similar to two cones placed base-to-base and whose axes align with the path of the shape.
Gradients between areas of dynamic and static pressure should ideally result in a rate of change of area to be gradual, smoothing the exterior profile from angled lines to a curve. Where negative gradients occur, an ideal shape may be a shallow exponential curve body of revolution, typically from the maximum cross-section to the trailing edge. Lastly, relative motion between solids and fluids causes friction (at low speeds friction is much lower than pressure drag), and the lowest surface area to volume ratio for a given design may have the lowest friction—which is why the leading edge approaches a spherical cross-section. All of the above describe the ideal ‘teardrop’ aerodynamic shape from a physics perspective (see, e.g.,
Applicability to surface vehicles is embodied by a teardrop shape in planform. Passengers are most comfortable with torsos generally upright, and seated frontal area is generally shoulder width versus trunk and head height—or a 2:1 height to width ratio. Such a vehicle will also preferably have more vertical cross-section behind the rear wheels which puts the center of pressure behind the center of gravity for improved yaw stability. For lowest drag, the suspension and wheels may be submerged in the bodywork, which is substantially the case with at least the embodiments shown in
Inline Seating Arrangement for Aerodynamic Body.
As noted above, single track vehicles generally provide an inline seating arrangement for passengers. These vehicles are low mass and low cost, but generally have no environmental exposure control nor impact protection.
In contrast to these conventional single-track vehicles, a narrow-track vehicle may, in another aspect of the present disclosure, be configured to monopolize on the low frontal area provided by inline seating, while simultaneously providing structure for environmental exposure control and impact protection. The vehicle may include packaging volume for high voltage batteries for energy storage which, as in prior embodiments, can be located beneath the passengers if the seating is generally recumbent and fore and/or aft of the passenger compartment.
In another aspect of the disclosure, the vehicles described above may be assembled via a frame comprised of a plurality of nodes, or 3-D printed joints that connect structural components such as, for example, carbon fiber connecting tubes, to form the vehicle chassis. Furthermore, in an embodiment, the deployment mechanism of the solar panels may be achieved by the use of additive manufacturing. In other embodiments, additively manufactured parts would be combined with other custom machined parts or with commercial-off-the-shelf (COTS) part to produce the final vehicle.
Folding Solar Power Arrays for High Energy Absorption and Low Drag on Vehicles.
Adequate solar energy absorption for a solar powered vehicle to achieve range targets implies large surface area of solar conversion cells. Most solar powered vehicles achieve the necessary surface area by implementing the largest possible plan area of the vehicle and installing solar cells on every available surface. However, these conventional approaches can be problematic and unpredictable. For example, many of these cells are inefficient as they provide low cross-section to the emitter during charging as the solar emitter moves across the sky, thereby driving further cost and mass into the vehicle to increase surface area for more paneling and achieve necessary energy absorption. Secondarily, the frontal area of the vehicle increases with width in plan view.
Planar arrays are the simplest implementation to achieving a given cross-section for a lowest mass, but other mostly planar arrangements may perform nearly as well from a specific mass per unit energy basis. Conformal arrays are possible, but require flexible cells and when deployed yield lower solar power due to cosine losses. Similarly, painted-on cells can yield larger surfaces, but also suffer from cosine losses. Telescoping planar arrays also improve solar absorption by increasing available surface area. Lastly, multi-hinged panels can be implemented—but likely with highest mass.
Referring still to
In another embodiment, the solar arrays on a vehicle, using active tracking or manual deployment techniques, can be optimized for most efficient capture of the sun's rays, subject to the capabilities of the configuration of the solar array.
In another embodiment, the arrays of solar panels may be configured to form a canopy over the vehicle for maximum exposure.
In another embodiment discussed below with reference to
The solar extended range electric vehicle is, in one embodiment, composed of several smaller structures designed not only to impart small mass and aerodynamic features to the vehicle but also to protect it occupants from injury in an impact event.
In another embodiment, an interior tub 1100 is provided for use within the alloy space frame.
In an embodiment, interior tub 1100 is located within the alloy space frame. The space frame may be mounted directly to the tub, or the exterior structure (
The interior tub 1100 may effectively create a sealed interior compartment for an occupant within the vehicle, adding an extra layer of protection for the occupant in an impact event. With the interior tub 1100 structurally mounted in a solid way in the frame or exterior structure of the vehicle, a single integrated component may be created that can protect the driver in the event of a collision or other significant forces exerted on the vehicle. In another embodiment, an interior tub may be created and designed to withstand two occupants in the vehicle. Alternatively, the vehicle may include a second interior tub situated inline with the first interior tub. This embodiment may result, however, in excessively large profiles. In another embodiment, the interior tub is extended and additional seating structure is provided so that it can accommodate more than one occupant or object.
In the embodiment where the interior tub 1100 is composed of a composite material such as carbon fiber, the interior tub 1100 may be made significantly lighter than, e.g., an all metal component. This light construction contributes to the overall mass savings of the solar vehicle. The interior tub 1100 may also protect the occupant from exposure to the battery cells beneath the user. The interior tub 1100 may also be personalized or stylized to the desire of the occupant and may easily be configured to receive wiring routed from other parts of the vehicle to power on one or more subsystems.
Tires 1206 are in close proximity to one another in this narrow track embodiment. In other embodiments, such as in wide track vehicles or similar, the wheels are father spread apart. Interior tub 1600 from
Various packaging options have been considered in an attempt to increase the total surface area of the solar panels, based on certain configurations of the panels. The increases in surface areas generally translate to an increased solar absorption and consequently an increased storage of electricity based on that absorption. However, this increase is beneficial only to a point where the increased area and configuration of the solar panels provide further benefit to increase the overall range of the vehicle. Stated differently, there is a point beyond which the car will not experience any appreciable gains from a larger solar area. Some viable options for the surface areas are identified below.
In a front region of vehicle 1300, solar panel 1313 is arranged in an evidently static pattern of the frame along a front region is solar panel 1313, which measures a considerably larger 600 cm2. Thus the total surface area of panels exposed to sunlight=600 cm2+400 cm2=1000 cm2.
To enable the configuration of
In addition, a deployment motor (not shown) may cause the solar panels 1501A-D to slide to the right (relative to
The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to the exemplary embodiments presented throughout this disclosure will be readily apparent to those skilled in the art, and the concepts disclosed herein may be applied to other solar vehicles and for techniques for additively manufacturing structures within solar vehicles. Thus, the claims are not intended to be limited to the exemplary embodiments presented throughout the disclosure, but are to be accorded the full scope consistent with the language claims. All structural and functional equivalents to the elements of the exemplary embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f), or analogous law in applicable jurisdictions, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”