EP4554808A1 - Method and system for extending the driving range of battery electric vehicles - Google Patents

Abstract

The invention relates to a method and a system for extending the driving range of BEVs comprising the production of electrical power by TPV conversion of chemical energy into readily usable thermal and electrical energy.

Description

Method and system for extending the driving range of battery electric vehicles

FIELD OF INVENTION

The present invention generally relates to the extension of the driving range of Battery Electric Vehicles (BEVs). It more precisely relates to the continuous and simultaneous supply of electrical energy for (re)charging the traction battery, and of thermal energy for operating on-board refrigeration and/or Heating, Ventilation and Air-Conditioning (HVAC) systems, from the combustion of a low-carbon (renewable) fuel such as methanol.

BACKGROUND OF THE INVENTION

Conditioning the cabin of all-electric automobiles using the traction battery accounts for a significant driving range reduction. In a car powered solely by an Internal Combustion Engine (ICE), the heat for the cabin is produced using waste heat from the engine. An ICE wastes energy creating heat as a byproduct of its operation. By contrast, a highly efficient electric motor produces very little heat, so the air temperature must be raised by some other means. In early all-electric automobiles, this was done by a simple resistive heater like the one found in a fan heater or electric fire. Modern BEVs use a heat pump system, which takes thermal energy from the outside air and compresses it before releasing the heat to the inside. However, heat pumps perform poorly in colder climates, precisely where a supplemental heat source is required, and their high energy consumption significantly reduces BEV driving range.

In 2019, the American Automobile Association conducted primary research to understand the impact of ambient temperature on the driving range and equivalent fuel economy of five all-electric automobiles sold throughout the United States. Testing was performed at 20°F (~-7 °C), 75°F (~24 °C) and 95°F (35 °C) according to guidelines established in SAE International standard J1634, Battery Electric Vehicle Energy Consumption and Range Test Procedure. The study found that the use of the HVAC system results in significant reductions of driving range and equivalent fuel economy: On average, HVAC use at 20°F resulted in a 41 percent decrease of combined driving range and a 39 percent decrease of combined equivalent fuel economy (when compared to testing conducted at 75°F). Also, an ambient temperature of 20°F resulted in a 12 percent decrease of combined driving range and an 8 percent decrease of combined equivalent fuel economy (when compared to testing conducted at 75°F). Mazda calculated the optimal battery size for all-electric automobiles to be of 35.5 kWh (See, e.g. MAZDA MX-30 RIGHT SIZED BATTERY STRATEGY at https://www.mazda.co.uk/why-mazda/news-and- events/mazda-news/articles/mazda-mx-30-right-sized-battery-strategy/). This is sufficient for approximately 200 km of inner-city driving and considered adequate for two reasons:

The first is, that people seldom use anywhere near the required 100 kWh needed to guarantee 500 km of autonomy. Most car makers agree on this.

The second reason is, that a smaller battery means less weight, reduced cost and better handling in any BEV.

New battery technologies, such as Li-Sulfur, Li-Air, or Mg-ion batteries, have been explored. Although they have higher theoretical energy densities than lithium-ion batteries, these batteries suffer from other issues, such as safety (due to dendrite formation) or poor cyclability, which prevent their application in BEVs (J. Deng et al., Electric Vehicles Batteries: Reguirements and Challenges; Joule, Volume 4, Issue 3, 18 March 2020, Pages 511-515.}.

Limitations of traction battery capacity contribute to what is known as "range anxiety", which poses an obstacle to the mass-market adoption of BEVs (P. Chakraborty et al., Addressing the range anxiety of battery electric vehicles with charging en route; Sci Rep 12, 5588 (2022). Over the last few years, several government bodies across the globe have been focused on offering financial as well as non- financial incentives, rebates, and subsidies to drive the adoption of electric vehicles. Notably, China, the U.S. and Germany are offering tax rebates and other incentives for the purchase of low/zero emission range extender electric cars. Additionally, companies such as BMW Group, Volvo Car Corporation, Nissan Motors Corporation, and General Motor Company are looking to incorporate range extender technologies into their new models.

In comparison to passenger cars, the electrification of heavy-duty vehicles poses greater challenges due to the high energy density requirements for traction batteries and the associated costs. Additionally, specific CO2 emission targets for heavy-duty vehicles are yet to be generally set and mandated. Despite this, the heavy-duty transportation sector is also making efforts to reduce its CO2 emissions.

As an example, the UK's Tevva Motors Limited provides electric trucks within a weight range of 7.5 to 14 tons, featuring a range extender that can run on hydrogen fuel cells for 310 miles (ca. 500 km) of green fright hauling.

Extended-range electric trucks have emerged as a promising solution for reducing emissions in the heavy-duty transportation sector. This allows for the gradual electrification of heavy-duty long-haul trucks, which may not be commercially viable with batteries alone, while still achieving significant emissions reductions compared to traditional diesel-powered trucks. Range-extended electric commercial vehicles can not only reduce additional payload and costs but also minimize the need for expensive charging infrastructure deployment at depots («Automotive & Transportation)), Electric Vehicle Range Extender Market, Industry Report, 2018-2025.}.

SUMMARY OF THE INVENTION

The drawbacks of the prior art are considerably reduced or completely overcome with the method and system according to the invention, as defined in the claims.

A first aspect of the invention is directed to the use of thermophotovoltaic (TPV) technology to generate a continuous flow of electrical energy for preferably (re)charging the traction battery in motion to extend the driving range of light-duty and heavy-duty vehicles with electric powertrain.

TPV energy conversion is the direct conversion of radiant heat into electricity through the photovoltaic effect. A basic TPV system consists of a thermal absorber, emitter and a photovoltaic (PV) solar cell. It has the advantages of fuel versatility, very quiet operation, low maintenance, and high-power density. By effectively harnessing and utilizing both the electrical and thermal energy outputs, the overall efficiency of TPV systems can be significantly enhanced.

Advantageously the electrical energy is generated from the TPV conversion of the chemical energy stored in a renewable low-carbon fuel such as methanol.

A second aspect of the invention is directed to the utilization of the waste heat from the TPV conversion for operating an energy recovery ventilation process powering the on-board HVAC system in BEVs.

In another embodiment of the invention, an absorption chiller is configured to recuperate heat from the TPV energy converter for operating an absorption refrigeration process supplying cool air to the BEV's cargo space and/or cabin.

The system according to the invention is preferably designed and configured as a compact modular TPV energy converter for use as driving range extender in BEVs.

The invention also relates to BEVs that contain at least one module as defined above.

According to another embodiment of the invention, in addition to the production of electrical power by TPV conversion of chemical energy into readily usable thermal and electrical energy, there is provided a method of heating a fluid such as an air flow caused by a means such as a fan, said method comprising the steps of (a) providing an ignition system with a pre-vaporized mixture of a renewable low-carbon fuel such as methanol and ambient air; (b) igniting said pre-vaporized mixture to generate heat; and (c) efficiently transferring the generated heat to the fluid to be heated.

Said ignition system comprises either a) a porous, ideally non-precious metal, catalyst suitable for catalyzing the combustion a pre-vaporized mixture of a renewable low-carbon fuel such as methanol and air; or b) a low-voltage arc discharge device as a viable alternative to conventional catalytic ignition mechanisms.

Said pre-vaporized mixture of a renewable low-carbon fuel such as methanol and air is produced using a Peltier element supplied with a renewable low-carbon fuel such as methanol and ambient air through a regulated pump powered by the BEV battery. Said element is powered by the BEV battery to produce a pre-vaporized mixture of said low-carbon fuel and air.

According to another aspect of the invention, in addition to the production of electrical power by TPV conversion of chemical energy into readily usable thermal and electrical energy, there is provided an apparatus for heating ambient air and infusing the filtered preheated air into a mixing duct as a component of the on-board HVAC system for heating, said apparatus comprising (a) one or multiple catalytic burners, each comprising (i) a housing defining a cavity and having air-input ports for receiving ambient air, fluid-input ports for receiving a renewable low-carbon fuel such as methanol, and an exhaust-gas-outlet port for discharging exhaust gases; (ii) a fluid diffusion medium disposed in said cavity and in fluid communication with said low-carbon fuel input ports; (ill) a series of flow fields defining a series of fluid communication cavities leading to the combustion chambers; (iv) a pervaporation membrane for supplying the ignition system with said low-carbon fuel in vapor form, the pervaporation membrane having an input face and an output face, the input face being in contact with the fluid diffusion medium and the output face being in contact with the ignition system; (v) a porous, ideally non-precious, metal catalyst suitable for catalyzing combustion of said low-carbon fuel in the presence of air, with said catalyst being disposed between said pervaporation membrane and said flow fields defining a series of fluid communication cavities leading to the combustion chambers, or a low-voltage arc discharge device as a viable alternative to conventional catalytic ignition mechanisms; (vi) a thermally isolated shell positioned in between the catalytic combustion frames; (b) a means for supplying the ignition system with said low-carbon fuel; and (c) a means for supplying the annular, helical or lattice burner burner with said low carbon fuel and ambient air.

According to another aspect of the invention, there is provided a method of converting chemical energy into electrical energy, said method comprising the steps of (a) providing thermal energy from digitally controlled catalytic or arc-discharge ignited combustion of a pre-vaporized mixture of a renewable low-carbon fuel such as methanol and air; (b) converting the thermal energy into shaped optical radiation matching the energy band gap of high-efficiency PV cells; and (c) guiding said photon energy through light-conducting media towards, and focusing it onto, high-efficiency PV cells to convert it into electrical energy readily usable to (re)charge a BEV traction battery.

According to another aspect of the invention, there is provided an apparatus for converting chemical energy into thermal energy and electrical energy, said apparatus comprising (a) one or more annular, helical or lattice burners, each comprising (i) a housing defining a cavity and having air-input ports for receiving ambient air, fluid-input ports for receiving a low-carbon fuel such as methanol, and an exhaust-gas-outlet port for discharging exhaust gases; (ii) a fluid diffusion medium disposed in said cavity and in fluid communication with said low-carbon fuel input ports; (ill) a series of flow fields defining a series of fluid communication cavities leading to the combustion chambers; (iv) a pervaporation membrane for supplying a porous catalyst with said low-carbon fuel in vapor form, the pervaporation membrane having an input face and an output face, the input face being in contact with the fluid diffusion medium and the output face being in contact with said catalyst; (v) a porous, ideally non-precious metal, catalyst suitable for catalyzing combustion of said low-carbon fuel in the presence of air, with said catalyst being disposed between said pervaporation membrane and said flow fields defining a series of fluid communication cavities leading to the combustion chambers, or a low-voltage arc discharge device as a viable alternative to conventional catalytic ignition mechanisms; (vi) a thermally isolated shell positioned in between the annular, helical or lattice burners; (vii) one or more capillary tubings enclosed within said thermally isolated shell, each comprising light-conducting media and a selective emitter; (viii) one or more burners directed to each capillary tubing; (b) a means for supplying each burnerwith said low-carbon fuel; and (c) a means forsupplying each combustion frame with fresh ambient air.

Said burners are preferably affixed to one or more individual annular combustion frames, each surrounding the thermally isolated shell.

Alternatively, said burners may be affixed to one or more individual helical combustion frames, each surrounding the thermally isolated shell.

In another embodiment of the invention, said burners are affixed to a combustion lattice surrounding the thermally isolated shell.

In another embodiment of the invention, one or more annular, helical or lattice burners are mounted on a motor-driven shaft along the annular combustion frames, the helical combustion frames, or the combustion lattice, so they can be directed in various angles to the capillary tubings.

Additional objects, as well as aspects, features and advantages, of the present invention will be set forth in part in the description that follows, and in part will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings, which form a part thereof and show by way of illustration various embodiments for practicing the invention. The embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the apparatus claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, aspects and advantages of the present invention will be more fully understood when considered with respect to the following detailed description, appended claims, and accompanying drawings where:

FIG. 1A is a longitudinal cross-section of the invented method for recovering waste heat from the TPV- conversion process to power the on-board HVAC system, with a thermally isolated energy conversion shell positioned in between one or more combustion frames or a combustion lattice;

FIG. IB is a simplified functional depiction of 1A;

FIG. 1C is a simplified longitudinal representation of 1A, with the thermally isolated energy conversion shell positioned in between annular combustion frames;

FIG. 2A is a longitudinal cross-section of the invented TPV-conversion system featuring a heat-isolated energy conversion shell enclosing the capillary tubings, each comprising light-conducting media and a selective emitter, embedded between either combustion frames or a combustion lattice and bilateral PV cells;

FIG. 2B is a simplified functional depiction of 2A;

FIG. 2C is a simplified longitudinal representation of 2A, with the heat-isolated energy conversion shell positioned in between annular combustion frames with bilateral PV cells.

FIG. 2D is a simplified longitudinal representation of 2A, with the heat-isolated energy conversion shell positioned in between a helical combustion frame with bilateral PV cells.

FIG. 3 shows the radiative emittance of Yb₂O₃ over the spectral range between 0.4 and 1.9 pm at 1598 K (1324.85 °C), 1808 K (1534.85 °C), and 1850 K (1576.85 °C).

FIG. 4 shows the solar spectrum useful to silicon photovoltaic cells (C. Strumpel et al., Modifying the solar spectrum to enhance silicon solar cell efficiency -An overview of available materials; Solar energy materials and solar cells Solar energy materials and solar cells, 2007, Vol.91(4), p.238-249.). DETAILED DESCRIPTION

According to one example of the invention, the TPV waste heat recuperation system harnesses waste heat from the combustion of a renewable low-carbon fuel to operate the on-board HVAC, eliminating the need to draw power from the traction battery e.g., for running a heat pump, in BEVs. The air-heat exchanger works by passing hot air from the combustion chambers through a tube bundle enclosed in a thermally isolated shell. The counter flowing cold ambient air is blown into the thermally isolated shell - where the heat transfer occurs - and subsequently injected as warm ambient air into a mixing duct as a component of the on-board HVAC system.

FIG. 1A illustrates, by way of a cross-section, the general structural features of the TPV waste heat recuperation system configured to operate as methanol-air catalytic combustion air heater. Both sides A and B in the cross section comprise flow fields defining fluidly connected cavities 4 leading from a fluid diffusion medium 3 through a pervaporation membrane 5 onto a porous catalyst 7. The fluid diffusion medium comprises a heating coil 6 connected to an electric source 19 that controls heat generation in order to preheat methanol liquid up to 65 °C. The ignition system is connected in parallel to said electric source to enable and trigger spark ignition or thermal tip ignition of a pre-vaporized mixture of a renewable low-carbon fuel such as methanol and air inside the combustion chambers 8. Upon ignition, combustion is maintained without electricity. Each combustion chamber has and air vent and is connected to an exhaust-gas tubing bonded to a thermally isolated shell 16. Heat pipes 10 made of cupper are positioned around the thermally isolated shell in order to improve heating response time.

The heat pipes are made of metal such as cupper. Each has three sections: the evaporator, adiabatic, and condenser. The interior of each pipe is covered with a wick, and each pipe is partially filled with a liquid such as water. When the evaporator section is exposed to heat, the liquid inside vaporizes and the pressure in that section increases, causing the vapor to flow at a fast speed toward the condenser section of the heat pipe.

FIG. IB is a simplified functional depiction of 1A, which illustrates the flow of fluid methanol injected along fluid conducting tubes 22 via an electric fluid pump 25 connected to a controller from a methanol source 1 through fluid input ports 21 into the fluid diffusion medium. Moreover, it illustrates the flow of ambient air blown by a fan 11 along ambient-air-conducting tubing 13 through an ambient-air-input port 17 into the thermally isolated shell. Ambient air is also blown in countercurrent through infusion- air-input ports 23 into infusion-air-conducting tubings 9 running along the outside of said thermally isolated shell. Said infusion-air-conducting tubings are connected to the combustion chamber exhaust gas tubings to create a negative pressure as infusion ambient air flows through them, thus causing methanol to flow from said fluid diffusion medium through said pervaporation membrane and said porous catalyst into said combustion chambers while extracting exhaust gases. FIG. IB also illustrates the flow of warm infusion air out of the thermally isolated shell through a warm-infusion-output port 24 along a warm-infusion-air-conducting tubing 25 for heating the cabin of BEVs. Exhaust gas predominantly consisting of the non-toxic products from methanol combustion (CO₂ and water) flows through exhaust-gas-output ports 15 out of the thermally isolated shell and is sent into the atmosphere along an exhaust-gas-conducting tubing 18. Temperature sensors 14 are connected to said ambient- air-conducting tubings, as well as to said fluid-conducting tubing and to the warm-infusion-air- conducting tubing.

In another example, the TPV waste heat recuperation system harnesses waste heat from the annular, helical or lattice burners to operate an absorption chiller that vaporizes a refrigerant, which is then absorbed by another substance, and ultimately released as a liquid through a cooling process, resulting in the production of cool air for the BEV's cargo space and/or cabin.

In another example, the heat generated from the annular, helical or lattice burners is harnessed to produce optical radiation that is transmitted via light-conducting media onto bilateral PV cells for conversion into readily usable electricity to (re)charge the traction battery in BEVs.

According to an embodiment of the invention the combustion of a pre-vaporized mixture of a renewable low-carbon fuel such as methanol and air is initiated by catalytical thermal tip within each individual burner, promoting efficient and consistent heat generation. Each burner can be operated at varying temperatures continuously or in a pulse mode to account for the reduction of heat losses. Alternatively, an arc discharge device operating at a voltage range of 3.7 to 3.8 volts generates a spark to ignite said pre-vaporized mixture. Upon catalytical thermal tip ignition, the combustion reaction is self-sustaining and does not require an external power source, such as electricity, to maintain the flames.

FIG. 2A illustrates, by way of a longitudinal representation, the general structural features of the TPV energy converter. Both sides A and B in the cross section comprise flow fields defining fluidly connected cavities 4 leading from a fluid diffusion medium 3 through a pervaporation membrane 5 to a porous catalyst 7. The fluid diffusion medium comprises a heating coil 6 connected to an electric source 19 that controls heat generation in order to preheat methanol liquid up to 65 °C.

The ignition system is connected in parallel to said electric source as to enable and trigger (catalytic thermal tip or spark) ignition of methanol inside the combustion chambers 8. The use of nanosized Ptbased catalysts with high activity at low temperature has been reported in the literature (B. Bitnar et al., Thermophotovoltaics on the move to applications; Applied Energy Volume 105, May 2013, Pages 430-438.). However, platinum is known to degrade thermally, with vapor compound (PtO₂) formation accompanied by transport causing a fast catalyst deactivation due to the loss of the expensive active phase (C.H. Batholomew, Mechanisms of catalyst deactivation; Applied Catalysis A: General Volume 212, Issues 1-2, 30 April 2001, Pages 17-60.). Given the high temperatures required to activate a selective emitter such as Ytterbium oxide (Yb₂O₃), the porous catalyst 7 needs to be designed for high thermal stability. La, Mn hexaaluminates have been investigated and determined to be excellent candidates for the development of a high-temperature catalytic burner in methanol-fueled systems for energy generation, with the catalytic combustion of lean methanol-air mixtures reportedly starting at ca. 250 °C (S. Cimino et al., Catalytic combustion of methanol over La, Mn-hexaaluminate catalysts; Fuel Processing Technology Volume 133, May 2015, Pages 1-7.). These materials exhibit a stable phase composition up to 1600 °C and exceptional resistance to sintering and thermal shock, which makes them attractive materials for several applications, incl. as catalysts for high-temperature applications, superionic conductors, and luminescent and laser materials (JJ. Spivey et al., Preparation and characterization of hexaaluminate materials for high-temperature catalytic combustion; from the book: Catalysis: Volume 13, 12 December 1997, ISBN 978-0-85404-209-8.).

Each combustion chamber has an air vent and a burner nozzle pointed directly at one of the heat- isolated capillary tubings 27, each comprising light-conducting media 28, respectively positioned around the inside of a heat-isolated cylindrical energy conversion cell 29. The selective emitter is enclosed within said capillary tubings and spectrally matched to the energy bandgap of the PV cells 30 to enable efficient conversion into electricity.

FIG. 2B is a simplified functional depiction of 2A, which illustrates the flow of fluid methanol injected along fluid conducting tubes 22 via an electric fluid pump 26 connected to a controller 12 from a fuel source 1 through fluid input ports 21 into the fluid diffusion medium 3. It also illustrates the infusion of ambient air into the lower end of the energy conversion cell, and the extraction of exhaust gases through the upper end on the opposite side of said cell.

The burners are each focused on single capillary tubings generating temperatures of no less than 1200 °C from (catalytic) methanol-air combustion. In order to achieve temperatures equal to and exceeding this threshold up to 1600°C, a mechanism is provided for generating hydrogen and injecting it into the methanol stream prior to reaching the burner nozzles. At and above this temperature threshold, Yb₂O₃ emits light predominantly in the near-infrared region roughly between 800 nm and 1200 nm, as shown in FIG. 3. The emitted light is guided out of the energy conversion cell towards the PV-cells through said light conducting media. The wavelength of said light matches the silicon band gap shown in FIG.

4.

Claims

1. Method for extending the driving range of BEVs comprising the production of electrical power by TPV conversion of chemical energy into readily usable thermal and electrical energy.

2. Method according to claim 1 wherein said chemical energy is stored in a renewable low- carbon fuel.

3. Method according to claim 2 wherein said low-carbon fuel is methanol

4. Method according to anyone of the previous claims wherein said thermal energy is used to operate the on-board refrigeration and/or HVAC systems in BEVs.

5. Method according to anyone of the previous claims wherein said electrical energy is used to (re)charge the traction battery of BEVs.

6. A low-carbon fuel-based modular TPV energy conversion system for generating thermal and electrical energy in BEVs.

7. System according to claim 6 comprising a combustion frame or an array of combustion frames producing digitally controlled micro-flames ignited by catalytic thermal tip or spark to provide a highly efficient and reliable combustion process.

8. BEV comprising at least one system according to claim 6 or 7.