Zero-energy Solutions Research Articles

Adaptive Phase Change Microcapsules for Efficient Sustainable Cooling.

Passive radiative cooling has recently gained significant attention as a highly promising technology that offers a zero-energy and electricity-free solution to tackle the pressing issue of global warming. Nevertheless, research efforts have predominantly focused on enhancing daytime and hot-day radiative cooling efficacy, often neglecting the potential downsides associated with excessive cooling and the consequent increased heating expenses during cold nights and winter days. Herein, we demonstrate a micro-nanostructured engineered composite film that synergistically integrates room-temperature adaptive silica-shell/oil-core phase change microcapsules (S-PCMs) with commercially available cellulose fibers. The resultant composite film exhibits a solar reflectance of 0.92 and a mid-infrared emissivity of 0.96, achieving a remarkable average daytime subambient cooling of 7.5 °C under direct sunlight in hot conditions. Encouragingly, upon reaching the phase transition temperature, the heat previously absorbed and stored by S-PCMs is released, resulting in a temperature elevation of the composite film with an average temperature differential of merely 3.0 °C compared to surrounding air. The exceptional latent heat storage capability of our S-PCMs/cellulose composite film mitigates the radiative overcooling effect and substantially diminishes the heating demand, particularly across a diverse array of environmental conditions.

Relationship between Φ4-matrix model and N-body harmonic oscillator or Calogero-Moser model

Abstract We study some Hermitian Φ4-matrix model and some real symmetric Φ4-matrix model whose kinetic terms are given by Tr(EΦ2), where E is a positive diagonal matrix without degenerate eigenvalues. We show that the partition functions of these matrix models correspond to zero-energy solutions of a Schödinger type equation with N-body harmonic oscillator Hamiltonian and Calogero-Moser Hamiltonian, respectively. The first half of this paper is primarily a review of previous work of us. The discussion of the properties of zero-energy solutions and the discussion of systems of differential equations satisfied by partition functions derived from the Virasoro algebra in the latter half of this paper contain novel material.

Generating QES potentials supporting zero energy normalizable states for an extended class of truncated Calogero Sutherland model

Motivated by recent interest in the search for generating potentials for which the underlying Schrödinger equation is solvable, we report in the recent work several situations when a zero-energy state becomes bound depending on certain restrictions on the coupling constants that define the potential. In this regard, we present evidence of the existence of regular zero-energy normalizable solutions for a system of quasi-exactly solvable (QES) potentials that correspond to the rationally extended many-body truncated Calogero–Sutherland (TCS) model. Our procedure is based upon the use of the standard potential group approach with an underlying so(2,1) structure that utilizes a point canonical transformation with three distinct types of potentials emerging having the same eigenvalues while their common properties are subjected to the evaluation of the relevant wave functions. These cases are treated individually by suitably restricting the coupling parameters.

Optical properties of La2O3 and HfO2 for radiative cooling via multiscale simulations

Abstract Radiative cooling materials have gained prominence as a zero-energy solution for mitigating global warming. However, a comprehensive understanding of the atomic-scale optical properties and macroscopic optical performance of radiative cooling materials remains elusive, limiting insight into the underlying physics of their optical response and cooling efficacy. La2O3 and HfO2, which represent rare earth and third/fourth subgroup inorganic oxides, respectively, show promise for radiative cooling applications. In this study, we used multiscale simulations to investigate the optical properties of La2O3 and HfO2 across a broad spectrum. First-principles calculations revealed their dielectric functions and intrinsic refractive indices, and the results indicated that the slightly smaller bandgap of La2O3 compared to HfO2 induces a higher refractive index in the solar band. Additionally, three-phonon scattering was found to provide more accurate infrared optical properties than two-phonon scattering, which enhanced the emissivity in the sky window. Monte Carlo simulations were also used to determine the macroscopic optical properties of La2O3 and HfO2 coatings. Based on the simulated results, we identified that the particle size and particle volume fraction play a dominant role in the optical properties. Our findings underscore the potential of La2O3 and HfO2 nanocomposites for environment-friendly cooling and offer a new approach for high-throughput screening of optical materials through multiscale simulations.

Realization of Jackiw–Rebbi zero-energy modes at photonic crystal domain walls: Emergence of polarization-indiscriminate surface states

The Jackiw–Rebbi model is a relativistic quantum model credited with the theoretical predictions of zero-energy bound states and charge fractionalization prior to the discovery of topological insulators and the fractional quantum Hall effect. In this work, we demonstrate a photonic equivalent of the Jackiw–Rebbi model by resorting to photonic crystal band structure engineering. Specifically, our photonic realization employs two spatial inversion symmetric binary photonic crystals exhibiting complementary signs of differential effective mass parameter (δm) for their second bandgaps. Their concatenation manifests a step discontinuity in the spatial profile of the effective mass parameter, forming a domain wall at the photonic crystal interface. Upon analyzing the reflectance spectra of the concatenated photonic crystal structure, we find a midgap surface state localized at this domain wall. Furthermore, much in agreement with the Jackiw–Rebbi zero-energy solution, the materialized photonic surface state also exhibits a zero-energy character in a differential energy space corresponding to the δm parameter, which has been quantified experimentally. Crucially, the conceived zero-energy mode amounts to the observation of a peculiar surface state with polarization-indiscriminate dispersion that can help realize all-angle polarization neutral optics.

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Zero modes of fermions trapped by giant vortices

Zero-energy solutions of the Dirac equation for the fermions bound to giant vortices of large winding number n are studied in the abelian Higgs and Chern-Simons Higgs models. The case of Jackiw-Rossi theory of the Majorana states in topological superconductors is discussed in detail. By expanding in inverse powers of n we find an analytic result for asymptotically all n solutions required by the index theorem. In the abelian Higgs model the zero modes fill the vortex core and reveal a universal structure independent of fine details of the gauge and scalar field interactions which, in particular, determines the general properties of the large-n superconducting cosmic strings. On the contrary, for the Chern-Simons Higgs vortices the zero modes are localized on the core boundary and the explicit solution is obtained for the supersymmetric couplings in a self-dual background.

Analysis of Legal Issues of the Crime of Endangering Public Safety Based on Data Mining Algorithm

In order to improve the analysis effect of legal issues of the crime of endangering public safety, this paper analyzes the legal issues of the crime of endangering public safety based on the actual mining algorithm and uses numerical methods to qualitatively study the evolution behavior across phase intervals. Moreover, this paper improves the algorithm based on the actual needs of legal mining. When solving the eigenvalues of the given Hamiltonian’s duration equation, the zero-energy solution can be found in the case of open boundaries. In addition, this paper applies the improved algorithm proposed in this paper to the mining of criminal law legal issues of crimes against public safety, assigns a dynamic IP to each process, and builds a model based on this. Through the above simulation research, it can be seen that the legal problem analysis model of the crime of endangering public safety based on the data mining algorithm proposed in this paper has a good legal data mining effect.

Impact of the type, orientation, and temperature of solar panels on observed efficiency in Latvian climate conditions

As solar panel technologies become more and more popular and are increasingly used in nearly zero-energy building solutions, one must make sure that the panels are able to achieve performance indicators similar to those determined by manufacturers under standard testing in real-world conditions. To determine the efficiency of poly- and monocrystalline panels, depending on their spatial orientation and other parameters, a set of test panels was installed in Riga, Latvia in 2018 for long-term monitoring of their power output. This article summarizes the results for the first two years. In the autumn of the second year of monitoring, temperature sensors were installed on the solar panels to study the effects of temperature on panel’s efficiency. The data show that the panel’s spatial positioning is a crucial element affecting the amount of energy produced, although the type of panels and climate conditions are also important.

WKB Estimate of Bilayer Graphene's Magic Twist Angles.

Graphene bilayers exhibit zero-energy flatbands at a discrete series of magic twist angles. In the absence of intrasublattice interlayer hopping, zero-energy states satisfy a Dirac equation with a non-Abelian SU(2) gauge potential that cannot be diagonalized globally. We develop a semiclassical WKB approximation scheme for this Dirac equation by introducing a dimensionless Planck's constant proportional to the twist angle, solving the linearized Dirac equation around AB and BA turning points, and connecting Airy function solutions via bulk WKB wave functions. We find zero-energy solutions at a discrete set of values of the dimensionless Planck's constant, which we obtain analytically. Our analytic flatband twist angles correspond closely to those determined numerically in previous work.

From cost-optimal to nearly Zero Energy Buildings’ renovation: Life Cycle Cost comparisons under alternative macroeconomic scenarios

Abstract Policies and financial framework aiming to encourage energy efficient building renovations should contribute to “fill” the existing investment gap between Cost-Optimal (CO) solutions, that are more economically convenient, and nearly Zero Energy (nZE) solutions, which have the lower energy consumption, in order to make more convenient to the investors to choose the more energy efficient options. This investment gap depends on the long-term expected value and volatility of several interdependent macroeconomic variables. However, standardized LCC methods used for CO assessments disregard the long-term uncertainty and interdependence affecting these variables and, consequently, misrepresent the impact of the associated risk on the economic convenience. The present work aims to model alternative macro-economic scenarios where to carry out a “stochastic” LCC of predetermined building renovation solutions, in order to provide a useful and effective decision tool for building LCC, and especially to evaluate whether and how much the future macro-economic scenario could influence the investment gap between a CO and a nZE refurbishment solution. At this aim, we estimated the Vector AutoRegressive (VAR) models of four alternative macro-economic scenarios, ranging from a “regular growth” case to more extreme conditions as experienced by major western economies in the last decades, based on real data, i.e. observed time series. The scenarios modelling and its relation to the stochastic LCC is the main result and novelty of the work compared to the conventional approach adopted in most of the literature and suggested by international regulations and standards. The method is illustrated through a case study, which demonstrates the potential of the developed methodology in providing interesting and informative results on the nature of the investment gap between CO and nZE solutions, that the policy should contribute to fill in order to address the environmental challenge in the building sector, and on how much this gap may vary depending on the volatility of the macro-economic context. The novelty of the work mainly lies on the possibility to highlight in which specific macroeconomic conditions the convenience of taking an investment decision under risk-aversion may be jeopardised (augmented), thus requiring a stronger (weaker) compensating public support.

An integrated circuit to null standby using energy provided by MEMS sensors

The advent of smart measurement systems and innovative wireless sensor networks evinces the necessity to develop novel solutions for conditioning circuits to be used in autonomous or quasi autonomous measurement systems and sensing nodes. The main problem these systems still face is the question of how to supply the nodes in a cost-effective way, considering that, very often, a battery is required, and consequently, the maintenance labor and cost to replace or recharge it may be high. The main target is to increase battery lifetime by decreasing unnecessary energy consumption as much as possible. In this context, several solutions, including energy harvesters, have already been proposed. One of the main solutions is the reduction of power consumption by the measurement device while in standby, which, in most cases, represents a significant amount of the total power dissipation. To this end, authors have already addressed a zero-energy standby solution able to supply the power requested by the measurement equipment only when the appliance is turned on. In this paper, we present an integrated circuit solution suitable to be used with MEMS scale transducers. The validation and the characterisation of the system will be shown to demonstrate the suitability of the proposed method.

Barriers and drivers to the uptake of innovative, affordable, and zero-energy dwellings in Belgium and Ireland

Despite efforts to promote and accelerate the adoption of innovative, affordable, and zero-energy dwelling solutions, the number of dwellings complying with standards such as the EPBD remains relatively low as we reach year 2020. Studies have already explored potential challenges and opportunities to the uptake of such designs. However, despite previous findings and recommendations, the market’s response remains slow. Building on existing knowledge and as part of the Housing 4.0 Energy project, this study investigates current financial, cultural, legislative and technical barriers and drivers to the implementation and uptake of small, innovative, affordable, zero-energy dwellings in small towns in Belgium and Ireland. Focus groups gathering housing providers, decision makers, stakeholders, and contractors were conducted in Leuven and Kilkenny. Outcomes revealed that participants’ general perceptions around barriers and drivers are similar between the two countries and are validated by previous research findings. However, a closer look at context specific barriers reveals considerable differences. The identification of these contextual differences enables a better apprehension of the current situation in every location leading to the formulation of context specific recommendations and a better allocation of precedence. Thus, this paper demonstrates the importance of context specific investigations not only in the identification of challenges to energy efficiency innovations but also in establishing more effective implementations.

Free Response of a Rotational Nonlinear Energy Sink: Complete Dissipation of Initial Energy for Small Initial Rectilinear Displacements

Abstract For two combinations of a dimensionless rotational damping parameter and a dimensionless inertial coupling parameter, we consider free response of a rectilinearly vibrating linearly sprung primary mass inertially coupled to damped rotation of a second mass, for which Gendelman et al. (2012, “Dynamics of an Eccentric Rotational Nonlinear Energy Sink,” ASME J. Appl. Mech. 79(1), 011012) developed equations of motion in the context of a rotational nonlinear energy sink (NES) with no direct damping of the rectilinear motion. For dimensionless initial rectilinear displacements comparable with those considered by Gendelman et al., we identify a region in the motionless projection of the initial condition space (i.e., for zero values of the initial rectilinear and rotational velocities) in which every initial condition leads to a previously unrecognized zero-energy solution, with all initial energy dissipated by rotation. We also show that the long-time nonrotating, rectilinear solutions of the type found by Gendelman et al. are (orbitally) stable only in limited ranges of amplitude. Finally, we show how direct viscous damping of rectilinear motion of the primary mass affects dissipation, and that results with no direct rectilinear dissipation provide excellent guidance for performance when direct rectilinear dissipation occurs. Some applications are discussed.

Methodology for design decision support of cost-optimal zero-energy lightweight construction

The interest to find cost-optimal zero-energy solutions for building, using multi-objective optimization, has risen dramatically over the last decade. Accordingly, several studies have been carried out, proposing new methods and tools. None, however, has introduced a simplified approach that is viable by a broader range of users. This study addresses this lack, offering a methodology that supports the decision making process on cost-optimal zero energy building, using a novel approach, namely Multi-Objective Parametric Analysis (MOPA), rather than optimization algorithms. This study adds to the domain of roof stacking construction by setting the weight of construction as a third objective. The current methodology is applied to a newly developed theoretical Reference Building (RB) for a Belgian passive roof stacking house. Different options of the building’s superstructure components (walls, roof, and windows) have been examined. MOPA follows three consecutive steps: modeling setup, parametric simulation, and ends up with evaluation and selection. The results show cost-optimal zero-energy and lightweight packages of design variables for the building envelope.

Wronskian representation of second-order Darboux transformations for Schrödinger equations with quadratically energy-dependent potentials

We construct a Wronskian representation of second-order Darboux transformations for Schrödinger-type equations that feature quadratically energy-dependent potentials. Besides generalizing the conventional Darboux transformation of second order, our results can be adapted to generate zero-energy solutions to the massless Dirac equation in two dimensions.

An agent-based model framework for understanding the decisions of households and exploring bottom-up effects on housing sustainability

Housing plays a crucial role in the transition towards sustainability. Zero-energy or low-carbon housing solutions are key, but their success depends on their acceptance by the users. We propose a conceptual and an operational framework for understanding households’ residential choices as a base for an agent-based model, using the tenant as basic unit to populate it. We firstly conceptualise the decision-making process of tenants as a system. Secondly, we cluster the synthetic agents populating the model into typologies of dwellings and tenants. Thirdly, we display their actions in the action arena, and set-up the test runs. Lastly, we introduce the next steps to follow for the simulation of the bottom-up effects on housing sustainability.

Renovation of Public Buildings towards nZEB: A Case Study of a Nursing Home

Recently, the European Union set new rules for the Energy Performance of Buildings emphasizing the need to facilitate the cost-effective renovation of existing buildings into nearly zero-energy buildings (nZEB). Within this framework, the aim of this paper is to investigate and evaluate the energy performance of existing public buildings before and after renovation into nearly zero-energy buildings. Since the general quality of existing buildings in Croatia has changed over different periods of construction, the presented research was conducted on a representative nursing home designed corresponding to different Croatian national building stock construction periods, based on a public sector buildings database obtained from the Croatian Energy Management Information System (EMIS). The thermal performance of the building envelope was designed to correspond to the periods of buildings built up to 1940, between 1941 and 1970, and between 1971 and 1980, taking into account characteristic building construction technology and service life. In terms of adopted energy efficiency measures, for all nearly zero-energy building renovation solutions, an energy and cost analysis was performed. The results showed that construction technology applied in different construction periods has the greatest impact on the energy performance of a building and thus on the economic and financial viability of investment in nZEB.

Darboux transformations for the massless Dirac equation with matrix potential: Radially symmetric zero-energy states

We present Darboux transformations for the construction of zero-energy solutions to the massless Dirac equation with a radially symmetric, diagonal matrix potential.

Zero energy mode for an electron in graphene in a perpendicular magnetic field with constant asymptotics

We study the influence of a perpendicular magnetic field with the asymptotics B(r → ∞) = B0 in an electrons in graphene. It is shown that the zero-energy solutions can exist only for one pseudospin direction, depending on the sign of the magnetic field in the infinite boundary. This, shows that zero-energy level is robust with respect to possible inhomogeneities of the magnetic field. In addition, we show that the number of the states with zero energy for one pseudospin projection is infinity. These results should be useful in the study of ripples which cause a scattering of Dirac particles in slowly decreasing magnetic fields where the asymptotic states is easy to define.