Eco-Management of Wireless Electromagnetic Fields Involved in Smart Cities Regarding Healthcare and Mobility

Abstract

The everyday comfort and security of the present society are intimately associated with the assistance of different tools that function by means of diverse sources linked to the transfer and conversion of electromagnetic (EM) energy. The use of these devices exhibits expected outcomes, which are regularly coexistent with unwanted side effects. A laudable intention of an administration is to strengthen the anticipated results and lessen the unsolicited effects. This paper’s goal, in the framework of such an organization, is to evaluate the significance of the methodologies of responsible attitude (RA) and one health (OH) in the everyday exercise of the involved wireless EM energy tools in the environment of a smart city (SC). The approach of RA is linked to a tool’s eco-design, while the concept of OH is linked to the protection of an SC’s biodiversity and ecosystem. The unwanted side effects of these wireless devices could be implicated as occurrences of straying or radiated EM fields on devices or living tissues. The investigation intends to assess the enhancement of projected outcomes and the reduction of unwanted effects in the quotidian exercise of wireless EM energy transfer and transmission tools in the SC environment. The challenges are associated with the sources and the emissions of wireless EM technologies available today, and their impacts on the health of living tissues, biodiversity, and the ecosystem. The paper centered particularly on two cases engaged in the SC environment. The first involves the disrupting effects of EM exposure of onboard or near-living tissues from sensing and assistance medical tools. The second is linked to the adverse biological effects resulting from wireless inductive power transfer used for charging the batteries inside electric vehicles while motionless or running in SCs. The inquiries followed in the paper are supported by instances in the literature.

1. Introduction

Throughout history, human civilization has sought to improve its well-being, including its comfort, health, and safety. This has been achieved through various innovations in dedicated tools and the use of natural resources. These tools operate by using different available energy sources. For several decades, electromagnetic (EM) energy has found an important place and has been increasing over time. This energy has been obtained from the conversion of different resources, mainly fossil fuels. Recently, human well-being has been considered to be associated with the ecosystem and biodiversity in an ecological context. This can be achieved through the use of clean energy, converting it into EM energy, and the eco-design of EM tools, which corresponds to the sustainable use of these tools. Thus, performance is increased, energy is saved, and harmful side effects for humans in their biodiversity and ecosystem environment are reduced; these elements reflect the responsible attitude (RA) approach. Indeed, the use of EM tools presents projected results, which are regularly concomitant with unsolicited side effects. These hostile effects involve exposure to stray and radiated EM fields (EMFs) that could disrupt various devices, including health devices, as well as produce adverse biological effects (BEs) in all exposed living tissues involved in biodiversity. This exhibits the one health (OH) approach [1,2].

In the urban ecological context, the above-mentioned disturbances provoked by the side effects related to exposure to EMFs could originate, for example, from wireless communication, e.g., [3], mobility e.g., [4], or energy transfer devices [5,6], which are widely used in daily life. Different categories of exposures are related to systems involving wireless transfer or the transmission of energy. These are related to the transfer distance, the amount of power transferred, the frequency of the EMF involved, and the nature of the exposed object and its position. For portable wireless telecommunications tools such as mobile phones, they involve low power at high frequency, radio frequency (RF), and may be close to the exposed object. The exposure in this case is focused on a small area of the exposed object. For mobile phone antenna towers, they involve higher powers but are far from the exposed objects, and the exposure is homogeneous [7,8] or overall on the exposed object [9]. In the case of wireless inductive power transfer (IPT), it is a wide power range, from a few watts for charging the batteries of small household tools [10,11] to between tens of kW and on the order of MW in the case of electric vehicles (EVs), cars (tens of kW), trucks, buses (magnitude order 100 kW), boats (can reach the MW order), etc. [12,13]. The transfer distance is small (from a few mm to a few cm) and at a low frequency (up to 300 kHz). The object possibly disturbed and exposed to stray fields could be at a distance of a few cm from small tools, about one m from those involved in EVs. As mentioned earlier, exposure to EMFs from wireless power transport in general can disrupt different objects. These disturbances could be related to living tissues in general (including biodiversity). Such disturbances could directly cause BEs in tissues or indirectly impair the functioning of tools onboard living tissues.

The field of investigation involved in the present work is related to the evaluation and improvement of the behaviors of wireless EM devices used in SCs, thus, allowing for the protection of affected living tissues, biodiversity, and ecosystem from their harmful effects. The impact of such an assignment will be illustrated by two specific applications of wireless EM tools used in the SCs related to the disturbances of medical devices used near living tissues and the biological effects of EV chargers.

Indeed, this contribution aims to assess the importance of RA and OH approaches in managing the improvement of expected results and the reduction of undesirable effects in the daily practice of wireless EM energy transfer and transmission devices in the context of smart cities (SCs). This management obviously involves better monitoring and better design. How this is accomplished in practice will be illustrated by examples taken from the literature. In fact, the various analyses pursued in the article are supported by examples published in the literature. The following sections of the contribution will analyze and illustrate such management. Section 2 summarizes the different disturbance effects of EMF exposure, in the non-ionizing frequency range, on different devices and living tissues. Section 3 concerns the roles of RA and OH approaches in EMF management in wireless EM devices. Section 4 concerns the physical phenomena and the governing mathematical equations related to the design of an EM device and the evaluation of the side effects of radiated EMFs. Section 5 is devoted to two applications of wireless energy transfer and propagation devices used in the urban environment of SCs. These are disturbances due to EMF radiation from wireless communication devices on or near living-tissue tools, and tissue BEs due to wireless IPT for batteries charging aboard EVs. Section 6 is devoted to a discussion involving additional details of matters related to the preceding sections and possible evolutions in the topic.

2. EMF Exposure Perturbation Effects

In diverse circumstances, EMFs are expended daily in numerous cordial commitments. Moreover, they are engaged effectively in medical actions. Contrarily, when such fields are activated unintentionally, they may yield negative effects. The exposure to such fields could disturb apparatuses’ functioning and provoke adverse BEs in living tissues. Such concerns are closely allied to the nature of the field and the radiated matter. The field intensity and frequency characterize EMFs, while the material and structural assets depict matter. The effects of EMF radiation can be divided into two sets regarding the ranges of frequency. One covers the range shared by radio, microwaves, and infrared waves that yield non-ionizing exposure, while the second concerns the range split into ultraviolet, X-, and gamma rays that fashion ionizing radiation. In this last range, field radiation on living tissues would likely cause serious adverse health effects by generating tissue harm. EMFs in the non-ionizing class operate safely in frequent circumstances but can also provoke adverse effects for excessive field strengths and exposure durations.

Wireless energy transfer and propagation devices involve non-ionizing EMF exposures in the ranges of, respectively, low frequency up to 300 kHz and RF, at 10⁵–3 × 10¹¹ Hz. Two categories of EMF exposures are related to the distance between the source and the target. In the first, the source is close to the target, interacting in a near-field mode focused on a point of the target, while in the second, the source is distant (approximately higher than a wavelength for RF) generating a whole target homogenous far field exposure (see Section 6 for more details). The interaction between the field and the target is dependent upon the strength and frequency of the field, the exposure duration, and the properties of the target matter.

In the case of living-tissue targets, the degree of EMF exposure is evaluated by the tissue-specific absorption rate (SAR) in W/kg. This power density indicates the level of dissipated energy and its conversion to heat in a given exposure duration. This thermal outcome corresponds to the actual thermal BE of living tissues due to EMF exposure. The safety standards’ fixed limits for EMF exposures correspond to the SAR, consequent temperature rise, and EMFs induced in the living tissues. Such thresholds are established functions of the specifications of the source and tissue, as well as the exposure circumstances and duration. Such data designate the specific part of the tissue, the quality of the exposed subject (human, animal, plant, etc.), and the nature and duration of the exposure for the different situations of the subject exposed, which is related to its link with the source (fabricator, consumer, user, nearby, etc.). Excessive field strengths and exposure durations could produce a high SAR and disproportionate temperature rise, leading to adverse non-thermal BEs. These can trigger molecular disturbances, leading to tissue damage [14,15,16,17,18,19]. Additionally, fortuitous EMF exposures in the range of an ionizing frequency can cause dangerous adverse effects related to molecular disorders, triggering tissue damage because of the high energy of photons or particles.

In the case of target devices, which are usually protected against EMF radiation by the manufacturers’ safety regulations, the constancy of a device can be verified via an EM compatibility (EMC) analysis. In case the operation of the device uses EMF, exposure to external field radiation or the introduction of EM-sensitive materials could disturb the device’s own EMF and, thus, its constancy and reliability. Such effects would be amplified in medical devices operating in proximity to or embedded in tissues. Typical examples are static fixed-function onboard sensing tools [20,21,22,23,24,25,26,27,28,29,30], active organ stimulation tools [31,32,33,34,35], and magnetic resonance imaging (MRI) scanners used in guided therapies and interventions [36,37,38,39]. An EMC analysis is necessary to confirm the consistency of these medical tools disturbed by an external field or interfering substances [40,41].

3. RA and OH Approaches in Management of EMFs

The RA and OH approaches (see Section 6) are directly linked to the sustainable design of a target or source device and are associated with the object to be protected. Thus, a target corresponding to a living-tissue onboard tool is at risk, or a functional device acting as a source that directly radiates threatens living tissues. In the latter case, optimization aims to improve the overall performances, such as efficiency, power factor, etc., and to reduce the disturbing parasitic radiations. These two aspects of optimization, reinforcing the expected behavior and minimizing the undesirable side effects, added to the operational supervision of the device, are largely related to the RA and OH approaches and clarify their alliance [42]. The operational supervision of the device includes the planning of operations, which enables the sustainability associated with clean (carbon-free) energy use and economic pricing [43]. In fact, EM energy is considered strictly clean if it comes from a clean means of energy conversion. The above-mentioned disturbances related to parasitic EMF radiation could alter the operation of the exposed devices or produce BEs in the radiated tissues [41,42]. These adverse effects can be circumvented in two ways: via a sustainable design of the device components or through shielding technologies. Such shields are placed on the interface of (between) the radiation source and the exposed device or tissue. It should be noted that the electrical conductivity and/or permittivity (according to the involved frequency) of the materials of the device components are closely related to the disturbances of EM radiation. Such sensitivity to EMFs could be decreased by choosing materials corresponding to trivial conductive or dielectric behavior in the construction of a target device. Moreover, to ensure the constancy of the field distribution in MRI scanners, the materials inserted into their scaffold should be free of magnetic and conductive materials, thus avoiding EM noise, which can deteriorate the image due to artifacts [39,40].

It should be noted that, where sustainable design and shielding would be impossible or insufficient to circumvent the harmful effects of EMFs, the RA approach should be managed, in addition to device designers and manufacturers, by users involved in biodiversity and with decision-making capacity (i.e., public authorities) regarding the modes of use. Precautions should therefore be taken by monitoring spaces involving EMF radiation (see for example Section 5.2.4) or by establishing restricted areas without radiation sources.

4. Physical Phenomena and Ruling Equations

The phenomena ruling the design of an EM device are related to EMFs and electric circuit domains. The phenomena implicated in the side effects of device-radiated EMFs are likewise related to EM and heat transfer (HT) spheres. Actually, the interaction of EMFs radiated by a wireless EM device with matter crops undesirable thermal effects, which are governed by the EM and HT phenomena, coupled via the dissipated EM power (P_d) in these matters. In the instance of EMF exposure to living tissues, a bioheat (BH) phenomenon will rule the BEs and the temperature elevation created by a heat source P_d. These stated phenomena are governed by conforming mathematical equations, which are displayed in the following sections.

4.1. Governing Equations

Founded on Maxwell’s local behavior, the differential form of the general EMFs four equations [44] is given by:

∇ × E = − ∂_t B (Maxwell—Faraday)

(1)

∇ × H = σ E + ∂_t D (Maxwell—Ampère)

(2)

∇ · D = ρ_e (Maxwell—Gauss)

(3)

∇ · B = 0 (Maxwell—Thomson)

(4)

The HT equation in its differential form is given by:

c ρ ∂T/∂t = ∇ · (k ∇ T)

(5)

Note that, if we assume a constant value of the materials’ parameters, the typical time constant of electric/EM phenomena lasts about 3–6 periods of the wave, while thermal issues usually need a few minutes. It means that, for pulse work, sometimes, we can skip thermal analysis.

In the case of EMF exposure of living tissues or devices, the EMF harmonic fields, the BH, and the heat source P_d equations are given as follows:

∇ × H = J

(6)

J = J_e + σ E + j ω D

(7)

E = −∇ V − j ω A

(8)

B = ∇ × A with ∇ · A = 0 (gauge)

(9)

c ρ ∂T/∂t = ∇ · (k ∇ T) + P_d + P_t + c_f ρ_f p_f (T_f − T)

(10)

P_d = ω ε″ E²/2

(11)

In (1)–(11), H and E are the magnetic and electric field vectors in A/m and V/m. B and D are the magnetic and electric induction vectors in T and C/m², and A and V are the magnetic vector potential and electric scalar potential in Wb/m and volt. J and J_e are the total and source current densities vectors in A/m². The electric conductivity is denoted by σ in S/m, the volume density of electric charges by ρ_e in C/m³, and the angular frequency by ω = 2πf, with the frequency f in Hz. The character ∇ is a partial derivative vector operator. The character ∂_t is the partial time derivative operator. The behavior’s magnetic and electric laws, respectively, given by B/H and D/E, are signified by the permeability μ in H/m and the permittivity ε in F/m. The symbol ε″ denotes the imaginary part of the complex permittivity (j ω D = j ω (ε’ − j ε″) E), and ρ represents the material density in kg/m³. E represents the electric field strength (absolute peak value) in V/m; c represents the substance-specific heat (at constant pressure) in J/(kg °C), with k the thermal conductivity in W/(m °C) and T the temperature in °C. The dissipated power volume density in W/m³ given by Equation (11) links to the principal dielectric EMF loss and will be used in the coupling of EMF and BH equations. The BH Equation (10), related to living tissues, involves a self-tissue heat source P_t, convective heat transfer via irrigating fluid, and an external heat source related to the EMF exposure P_d, all in W/m³. T_f and T are, respectively, the fluid temperature and the local temperature of tissue in °C, and c_f, ρ_f, and p_f are, respectively, fluid, specific heat in J/(kg °C), density in kg/m³, and perfusion rate in 1/s.

Note that Equation (10) is comparable to Penne’s bio-heat equation [45,46] and is associated with animal living tissues, counting the convective heat transfer in the blood. Actually, the sap in plants plays a blood role in animals. Moreover, phloems and xylems encircling the sap act as veins and arteries, enfolding the blood. The term P_t in (10) is related to animal metabolic heat or internal heat in plant tissues. In addition, the last term in (10) acts for the convection of fluid heat transfer connected to animal blood or plant sap.

The analysis of an EM device, including electric circuits, is related to the EM domain, with Equations (6)–(9) coupled to the circuit domain via a general circuit equation under the form:

v = 1/C ∫ i dt + r i + L di/dt + dΨ/dt + ᴕ

(12)

In (12), v is the source voltage, i is the circuit current, r is the total circuit resistance, L is linear inductance, C is capacitance, ᴕ is the non-linear voltage drop (e.g., a semiconductor component) in the electrical circuit, and Ψ is the flux linkage. The equations describing the EMF and circuit domains to be solved are, therefore, Equations (6)–(9) and (12).

4.2. Numerical Solutions

The solution of the diverse equations relative to the EMF, BH, and electric circuit domains, (6)–(9), (10), and (12), respectively, should account for the specific characteristics of the involved structures. These are geometrical complexity, inhomogeneity of matter, nonlinear behaviors of variables, and domain interdependence, which imply sophisticated computational strategies [47]. Satisfying such attributes inflicts material local solutions, suggesting the employment of discretized 3D techniques as a finite-element method (FEM) or equivalent methods (BEM, FDTD, etc.) [48,49,50,51,52,53,54,55] concomitant to appropriate equation-coupling schemes. Thus, a weak coupling (iterative, due to distant time constants) of EMF and BH domains would be practiced through (11). In the case of electric circuit domain consideration, the coupling with the EMF one would be strong (simultaneous, due to close time constants) [56,57].

Note that the impact of the parameters involved in the solved equations of the EMF, BH, and circuit could be more or less significant depending on the frequency range involved, their degree of nonlinear behavior, and their degree of interdependence. Thus, depending on the device or phenomenon being modeled, the different parameters could reflect a small and negligible impact or a crucial one.

5. Applications of Wireless EM Energy Transfer and Propagation in SCs

An important part of SC technologies is the huge sets of transmitters, sources of signals, and targets. In this section, we will consider two applications of systems involving wireless energy transfer or propagation. The first, which is related to healthcare, investigates the perturbations due to EMF radiation from wireless communication devices on targets of near or onboard living tissues and medical tools intended for sensing or supporting duties. Actually, in SC environments at clinics, hospitals, homes with remote medical care, or simply in everyday life, we may need wearable or other body-near tools for different supervisions or treatments. The analysis is related to such tools for their sustainable design, permitting their protection against EMF radiation. In the second, which is connected to electric mobility [58], is the analysis of a wireless IPT for battery charging aboard an EV, considering its sustainable design and allowing the reduction of its stray-field BEs in living tissues. In both cases, the involved living tissues are relative to urban SC biodiversity involving humans (adults and children), animals (domestic and wild), plants (ornamental and wild), and all other members of the SC’s biodiversity. Moreover, these applications belong to connected remote strategies [59]. In the case of connected SCs, the two applications related to healthcare and mobility could be managed via their connections through the SC network [60].

5.1. Near and Onboard Living-Tissue Tools in SC Environment

Onboard tools are utilized in shapes that are portable, detachable, or integrated, which can execute inactive or active actions. Their deeds are placed in living tissues in general urban biodiversity. They can perform a detecting task, e.g., examination, predicting, etc. [20,21,22,23,24,25,26,27,28,29,30], or assistance jobs, e.g., support, invigorating, drug release, etc. [31,32,33,34,35], as well as serving as scanners involved in image-assisted medical therapies and interventions [36,37,38,39]. These two burdens could be distinct or linked and distantly piloted or self-ruling. Thus, such tools generally require permanent real-time inside and outside elegant interactions. Additionally, their required operational power could be integrated or distantly transmitted [61]. Moreover, remote data communication routines are essential for the intelligent operation of onboard tools using wireless transmission or other remote-sensing strategies, such as satellites for the observation, monitoring, and management of biodiversity in general [62].

Detecting tools (sensors) are normally non-invasive and portable or detachable, functioning in real-time and permitting continuous observation of the involved tissue, therefore providing appropriate health information to deduce its comprehensive state and, furthermore, an early health picture appraisal. Further personalized concerns related to disruptions of vital functions, such as the rate of respiration, the pressure of fluid circulation, etc., could be identified via detachable smart tools.

The supporting tools are of two categories implanted in the tissue (for health maintenance and organ stimulation) or containing the tissue (for image-assisted therapeutics). The first are pumps, tissue stimulators, pacemakers, implanted cardioverter defibrillators, etc., while the second are imaging scanners containing living-tissue parts that are concerned with surgical or implanted drug release procedures [36,39].

In addition, the above-detailed tasks of observation, prediction, support, stimulation, etc., of onboard tools, also permit the management of post-cure conditions in circumstances of previous disorders. Thus, circumventing transpositions, displacements, relocations, etc., substituting face-to-face care with an integrated connected support approach.

5.1.1. Onboard Tools Urban SC Perturbations Due to EM Radiations

Exposures to external EMFs have diverse consequences on onboard tools, including the impairment of their function and possible heating, which can increase the temperature of the living tissues involved. Thus, both categories of adverse effects can be critical and contingent on the nature of the organ being monitored, such as, for example, organ fluid circulation rate, the organ’s vital role, the tool task in the organ, etc. Figure 1 demonstrates the interaction of EMF exposure with the tool design, its duty, and its exposure side effects on biodiversity (OH approach) [41].

5.1.2. Onboard Tools Sustainable Design

As mentioned in Section 3, EMF perturbations of an onboard tool could be circumvented through eco-design either by managing its constituents or via shielding equipment. This could be achieved by avoiding EMF-sensitive matters in tool ingredients. Otherwise, shields should be used. Simple conductor shields could be employed when their heating does not produce a temperature rise in the adjacent living tissues. Otherwise, an amendment of the simple conductive shielding is needed. Thus, the use of multifunctional matched shield constituents permits low-reflectivity shields that lessen the strong field reflection triggered by the high substance conductivity [63,64,65,66,67,68]. The outcome of such an eco-design involving RA and OH approaches permits a sustainable onboard tool with diminished adverse EMF effects. Figure 2 clarifies the weight of eco-design comprising RA and OH approaches through the design or shielding of onboard tools, considering the whole biodiversity by supervising hostile urban SC EMF effects.

Figure 1 and Figure 2 demonstrate the impact of eco-design of an onboard tool on its performance and the reduction of its disturbances due to EMF exposure, which leads to a reduction in unwanted side effects.

5.1.3. Case of Image-Assisted Medical Therapies and Interventions Tools

Disorders in the distribution of the RF magnetic field inside of an MRI tunnel, which is image-correlated, are characteristically activated by external EMFs or by the insertion of conductive or magnetic stuff into the imager scaffold. In MRI-assisted interventions or therapies, only actuating tools fabricated from non-conductive and non-magnetic ingredients, such as piezoelectric matter, are tolerable. In general, piezoelectric actuators [69,70,71,72,73] employ for their excitation thin conductive electrodes. The positioning of such electrodes regarding the field orientation performs an important role connected to the influence of the conductive surface perpendicular to the field direction. Thus, the higher this surface, the higher the corresponding disturbance will be. Such an occurrence, which is related to the currents induced, could be exploited in the actuation context to diminish disorder in the distribution of RF magnetic field B₁ [36]. The checking of such a field distribution could be achieved via EMC analysis by solving Equations (6)–(9) and comparing the field distributions without and with the introduced matter. Figure 3 displays the RF magnetic field B₁ distribution (vertically directed) in the axial section of the birdcage inside the tunnel of an MRI, at 63.87 MHz (corresponding to static magnetic field B₀ of 1.5 T), for the no material case. Figure 4 exhibits an example of a cubic piezoelectric material with relative values of (µ, and ε) and σ of (µ_r = 1, ε_r = [450 990 990], σ = 0 S/m) coated by thin electrodes on two opposite faces with (µ_r = 1, ε_r = 1, σ = 3.77 × 10⁷ S/m)—see Figure 4a. Figure 4b,c show the field B₁ distributions in the two situations, where the electrodes are, respectively, perpendicular and parallel to the field direction. The effect of the conductors, in the last case (parallel to the field), is drastically reduced (Figure 3 and Figure 4c are almost identical). The results in Figure 3 and Figure 4 illustrate a simple qualitative example related to RA material use, avoiding adverse effects due to possible EMF noise image perturbation.

5.2. IPT Batteries Charging in EVs in SCs

A typical case of decarbonized energy applications is related to the substitution of internal combustion engine vehicles with EVs provided with battery energy storage. This solution was thought of in an ecological background for reducing air pollution and protecting global biodiversity and ecosystems, which are presently crucial. The energy storage batteries of these EVs, at last, will be wirelessly charged by IPTs in stationary and/or running modes. When replacing a long-established mode of transport to protect biodiversity and the ecosystem, it is necessary to ensure that the replacement solutions are consistent with such protection. Moreover, the building of these IPTs must expand what is ecologically considered to be best associated with a clean energy economy. In such a framework, both the RA and OH approaches will find their place in the design and control of IPT tools involved in the SC environment.

5.2.1. Wireless IPT Structure

A wireless IPT charging tool is inserted between the power source and the battery load. The IPT central element responsible for wireless charging is an inductive coupler transformer (ICT) connected to the source and load through power electronics converters. The ICT is composed of a transmitter and receiver coils having inductances of L₁ and L₂ and parted by an airgap characterizing a mutual inductance M₁₂. The airgap size reflects a weak coil coupling, and hence, the transfer of the required power implies a significant absorbed reactive power. So, the two coils are compensated by capacities C₁ and C₂. Thus, an IPT tool can perform a galvanic split wireless power transfer and a capacitive compensation that permits the electronics connected to an ICT to function at resonance. Such compensations on both sides of the ICT ensure consistent efficiency [74,75,76,77,78,79,80,81,82] and can use different topologies (series S and parallel P) contingent on the character of the load, such as for the two sides, SS, SP, PS, PP, etc. [75,82]. The SS compensation topology seems to be an economical option [81,82]. Magnetic ferrite sheets are usually employed to coat the outer external surfaces of the coils of the ICT, thus enhancing the transfer efficiency that is correlated to a better coupling coefficient. Figure 5 illustrates the schematics of an IPT involving its ICT details. The IPT includes its ICT–ferrite sheets sandwiched between the grid, via an AC-DC-AC-filtered adjusted frequency–voltage conversion, and the battery, via an AC-DC-filtered conversion [42].

5.2.2. Wireless IPT Sustainable Design and Control

The RA approach in IPT sustainable design and control involves the featured and topology construction of the coils and ferrites of ICT, compensations, static converters, and filters. Thus, this affects better performance [74,75,76,77,78,79,80,81,82,83,84] through enhanced coupling and dropped stray fields [42,85,86] that control the OH approach. This illustrates the junction of the two approaches. In addition, these two approaches are intimately connected, in addition to the IPT design, to the battery, state of charge estimation, and management [87]. Such management involves load-planning (battery charging) control that enables sustainability connected to clean (carbon-free) energy use and economical pricing. See, for example, [43]. Actually, EM energy, as mentioned earlier, is thought to be rigorously clean if it originates from a clean energy conversion process [88,89]. Figure 6 illustrates the two situations of unsustainable (a) and sustainable (b) designs of an IPT in the urban context of SCs [42].

Figure 6 demonstrates the implication of sustainable design of an IPT in the urban context of SCs through the use of a clean energy source and eco-design, allowing for high performance and reduced adverse side effects.

In the design and optimization of the ICT discussed in the last section (see Figure 5), the involved coupling coefficient k and the resonant frequency ω_o (for coils SS compensation) are given by:

k = M₁₂ (L₁ L₂)^−1/2

(13)

ω_o = (L₁ C₁)^−1/2 = (L₂ C₂)^−1/2

(14)

The ICT structure, outlined in Figure 5a, is presented in Figure 5c. It includes the coils, transmitter (on the ground), receiver (on the EV bottom), and the two magnetic ferrite plates covering the coils. Moreover, Figure 5c comprises a steel plate acting for the EV chassis. The coils of the ICT coupler with ferrites (pads) are parted by an air gap of (d) distance and (sh) coil axes shift. This structure will be considered in the design through Equations (6)–(9), accounting for (13) and (14) via (12) in strongly coupled EM and electric circuit domains. The BEs in living tissues relative to induced fields and temperature rise could be determined by solving (6)–(9) with a source corresponding to a stray field and (10) with a heat source P_d relative to (11). These EM and BH domains will be coupled in a weak manner.

5.2.3. RA and OH Approaches in SC Context

The wireless IPT charging of EVs in an SC-friendly manner is appropriate for shared and autonomous EVs, buses, trams, ships, medium-duty delivery trucks, drones, etc. IPT charging modes may be full static (in public stations or at home), full dynamic (electric roads), mixed dynamic–static mode, discontinuous electric roads, or split static charging points. A full static mode corresponds to a limited range and requires high battery storage. A mixed dynamic–static mode is mostly suitable for highways and necessitates moderate battery storage. An intermittent dynamic mode matches a partially fixed trajectory, entails low battery storage, and is appropriate for public mobility with road portions having challenging charging infrastructures. The mode using distant static charging points relates to electric buses charging at their stops, for which the battery storage depends on the number of stops, the distance, and the static duration. All these charging modes entail security protections against EMF exposure.

RA and OH approaches intend, for the different charging modes, an appropriate eco-design, clean energy use, reduction of harmful effects, risk evaluation, and safeguarding of biodiversity. Furthermore, the management of energy between the EV and the grid might help the RA. Therefore, we can use control algorithms for grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operating modes [90,91]. Additionally, it is required to guarantee the interoperability of different IPTs (ground and vehicle sides) [82,92] and deliver a fitting charging profile allowing for better RA [93]. In addition, connectivity and autonomous driving capability will make EVs much safer [94].

5.2.4. EMF Exposure, Charging Modes, and Protection

The EMF exposure due to ICT stray fields is directly dependent on the 3D relative positions of its two coils (ground to vehicle sides) and, hence, is strongly affected by the charging mode (static or dynamic) and the vehicle space positioning.

The consequences of such fields on living tissues are concomitant to their location in relation to the ICT position and the relative placing of its coils. The stray fields in dynamic charging mode are variable depending on the moving location of the receiver coil fixed at the EV bottom relative to the transmitter fixed on the ground. In this case, as well as in the case of buses with distant static charging points, the living tissues concerned are those inside the EV in the passenger compartment. In such situations, the protection of passengers could be achieved by shielding the vehicle’s upper part, over ICT, including the passenger compartment. This is an easy task using appropriate shapes and material shields [5,63]. The passenger compartment in the case of static charging mode is normally empty, while for such a mode, the involved living tissues are those located outside the EV near the ICT under its bottom. These involve humans, animals, or plants, and could be affected by stray-field exposure due to open-space static charging. Such a mode is regularly exercised at home for personal EVs and at distant static points related to electric buses charging at their stops. In these circumstances, the ICT shielding (in 3D geometry) is very problematic due to its configuration and position, partly on the bottom of the EV and in the ground. This problem is more difficult for larger or more twisted air gaps corresponding, respectively, to the distances “d” or “sh” in Figure 5c. As such, these parameters are difficult to control, and therefore, any element existing below or near the bottom of the EV must be avoided, especially for a significant duration. Thus, for the home-charging case, this should be practiced only in enclosed places or encircled areas in the open space. For the bus stop-charging case, the ICT should be located far from the bus entrance and the passenger waiting area.

5.2.5. Living-Tissue BE Control

The exposure circumstances painted above could be controlled and verified by the solution of the equations given in Section 4 by checking the induced electric field values in the living tissues matched to the standards’ established thresholds [95,96,97,98]. For different charging modes, the previously mentioned routines must contain the specific geometry and matter properties of living tissue. The evaluation of living-tissue EMF exposure needs methods based on 3D computations to solve the EM domain (6)–(9) comprising the ICT system (Figure 5c) and the living-tissue object (inside the vehicle or located nearby). Digital models (phantoms) regularly represent such living tissues. The significant features of such models are the consistency of the physical–biological properties, the realistic state (shape), and the reliability of the numerical methodology used. Several models and matter characteristics related to living tissue could be found in the literature, e.g., for human tissues [99,100,101,102,103,104]. For the human case, Figure 7 displays a structural body and its various organs and tissues [45].

5.2.6. Case of Exposure BEs in Human Body Nearby an EV

A demonstrative example of ICT EMF exposure concerning the case of a human body placed on the ground horizontally adjacent to an EV while in static charging mode is given in this section [45]. Figure 8 displays the induced field distributions (of B and E fields) in the body due to ICT EMF exposure. The utilized human body model for computations relates to the high-resolution human structural model, is well-matched with the numerical 3D FEM approach used, and is presented in Figure 7. The induced B and E fields in the body tissues have been computed from the solution of (6)–(9), with a source field corresponding to the stay fields of the ICT (3 kW at 30 kHz). The results were matched to the thresholds fixed by the safety standards [95,96] (27 μT for magnetic induction B and 4.05 V/m for the electric field E). In the present case, the results were in agreement with these safety guidelines.

Figure 7 and Figure 8 illustrate the use of a high-resolution human structural model, which is well-suited to the 3D FEM numerical approach used for matching an EMF-exposed body to thresholds set by safety standards for safety monitoring.

6. Discussion

The analyses and examinations involved in this contribution demonstrated the significance of RA and OH approaches to the management of enriching projected outcomes and reducing adverse effects in the daily practice of wireless EM energy transfer and transmission devices in urban smart cities context. Moreover, such management also permitted the protection against EMF exposure of medical onboard tools, as well as the living tissues of humans and their urban environment’s biodiversity and ecosystem. The RA and OH approaches were practiced via eco-design and monitoring involving human decision-making. The control of the different management actions (design, protection, control, risk evaluation, etc.) has been mastered and accomplished through governing physically involved phenomena and their mathematical equations treatments.

Following the different analyses involved in the paper’s sections, several points merit additional discussion.

As discussed earlier, regarding EMF devices, a laudable management objective is to augment the projected outcomes and reduce the unplanned effects, thereby increasing device performance and protecting biodiversity and the ecosystem. These objectives could be achieved through RA and OH approaches. It should be noted that the more sophisticated the device, the greater its side effects will be. For example, a more powerful communication tool or a faster battery-charging device would produce higher radiated or stray EMFs, respectively. In such a case, the role of RA and OH approaches would be more crucial.

Concerning the far-field exposures (Section 2), the definition of the far-field region could approximately be considered through the formula r′ > (2D²)/λ, where λ is the wavelength, D is the maximum dimension of scattered matter in free space, and r’ is the far-field distance. For example, for a radiated body at a frequency of 300 MHz (λ about 1 m), r′ is approximately for an adult human > 8 m, for a child > 1 m, and for a cat > 0.2 m.

The RA and OH approaches intend on the management of the EMF-perturbing source device, as well as the targeted medical device. In the first, the goal is to reduce stray or noise fields, while the second the goal is to ensure the device’s functioning and its shielding protection when necessary.

In the case of wireless-charging batteries, theoretically, the behavior of charging capacity versus running autonomy is approximately presented as follows. For a compensated IPT, neglecting losses, the transferred IPT energy = the battery storage energy capacity = the running energy autonomy. Thus, P_t T_t = n_c C_c = P_m T_r, where P_t and T_t are the transferred power and charging time, n_c and C_c are the number of battery cells and the battery cell storage energy capacity, and P_m and T_r are the motor power and the running time. It is worth noting that, for a given transferred power, motor power, and battery cell capacity, the charging time and autonomy time are correlated to the number of cells.

In the case of charging a bus battery on an urban trajectory, the choice of charging routines must take into account not only the battery storage capacity but also the infrastructure complexity and especially the exposure to harmful EMFs of the living tissues involved in urban biodiversity. These routines can be at the day, circuit (round trip), or stop level. The corresponding distance autonomies will be all of the circuits of a day, one circuit, or the distance between stops. Respectively, for these choices, the battery storage needs are significantly reduced, and theoretically, when using an electric road (permanent source), the necessary storage is zero. Of course, the infrastructure complexities and the protection technologies are different for such routine options. The day or circuit-level routines are without passengers. The case of a circuit charging routine could be a good compromise for battery storage, infrastructure complexity, and exposure safety. In such a case, the ICT could be on the roof of the bus, as shown in Figure 9. This figure illustrates how to optimize storage capacity, infrastructure, and EMF adverse exposure.

In this contribution, the OH approach has often been mentioned. It highlights the interdependence of biodiversity members “all for one and one for all” for the good of the ecosystem where they live. We have insisted on the fact that human well-being must not cause inconvenience to the members of a biodiverse setting, including humans, and even share this well-being. It is not a gift from humans to biodiversity and the ecosystem but just a return to them for their actions promoting the existence of humans. It is even enough to imitate them, like the actions of pollinators (like bees) [105], hydrologists (like beavers) [106], etc., in their roles in the ecosystem. We can find even more alliances, such as, for example, of certain viruses with their hosted organism (virus–host interaction), thus giving their hosts the ability to produce a toxin to destroy their competitors (as in the case of baker’s yeast) [107]. Other examples of interactions could be found, such as between bacteria and phytoplankton [108], or between certain microorganisms, plants, and nutrient cycles [109].

Regarding the RA approach definition, in the past, we had different attitudes toward technologies related to factors such as efficiency, compatibility, cost, etc. Recently, due to environmental threats, we need to consider the relationship between technology and environmental conditions. Thus, this involves finding a responsible attitude (RA) towards resources and emissions based on the technologies available today.

In applications related to onboard medical tools and wireless IPT mobility devices, sensors and actuators can be involved, and a wireless sensor and actuator network (WSAN) can be used, especially in a complex context. A WSAN is an assembly of sensors that collects data at their locations, and actuators interact with them autonomously or are wirelessly controlled. A WSAN realization point can encompass a mix of planned multi-actuation actions composed of sensors to perform more complex tasks. In fact, WSANs are increasingly used for health and medical care (on-site or remote), ecosystem monitoring and control, mobility, smart cities, etc. [110,111]. Such applications may contain high-level complexities that require adequate supervision. The presence of daily EM environmental disturbances in the vicinity of the concerned WSANs could threaten the operation of their components, as mentioned before, and the analysis of these disturbances in the context of complex scenarios always remains crucial.

Regarding connectivity in an SC environment [112,113,114], in addition to connections with other SCs, the different SC platforms, involving internal city administration, security, education, etc., could take into account healthcare and mobility boards [115,116,117]. Remote monitoring of the corresponding data of these boards could take into account the objective of the present contribution “Eco-management of wireless EM devices involved in SCs for healthcare and mobility”. This could be achieved by checking the proper functioning of the tissues’ onboard tools and the state of the EV battery, including its charging system (IPT parasitic radiation), thus protecting humans and their environmental biodiversity and ecosystem.

For the two investigated applications of this contribution, normally if the intended device’s design is correctly made, the medical near-body tools would function correctly, and the EV charger would not induce biological effects. The protection protocols of such applications are often defined by medical staff.

In the applications considered in the paper, humans could be affected by emissions of wireless EM devices in two ways: perturbations of medical near-body tools related to healthcare and biological adverse effects on the body due to mobility (EV) battery-charging tools.

To end on an encouraging tone, it should be noted that the harmful effects of EMFs discussed in this contribution are relatively different for biodiversity and the ecosystem from the effects of other current terrestrial pollution (chemical, biological, etc.) that could be cumulatively irreversible or degradable in the very long term. For the harmful effects of recently emerged EMFs, it is sufficient to take the necessary precautions using the recommended approaches to promptly stop the effects of these pollutions.