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Abstract One of the strategies to improve environmentally friendly energy harvesting can be realized by using biomass as a primary energy source for generating electricity and H2. In addition, high energy efficiency can be achieved by minimizing exergy loss through process integration and exergy recovery. As an implementation, this study proposes a cogeneration system for black liquor (BL) to co-produce electricity and H2. The system primarily comprises BL drying, circulating fluidized bed gasification, syngas chemical looping (SCL), and power generation. The Aspen Plus V8.8 software package is used for modeling and performing calculations of the proposed integrated system. Furthermore, thermodynamic analysis of gasification is performed by employing Gibbs energy minimization. The effects of target solid content on the required total work and compressor outlet pressure during drying and gasification with different steam-to-fuel ratios are evaluated. Moreover, the SCL process adopts three reactors, namely, the reducer, oxidizer, and combustor. Compared to conventional processes, the integrated drying-gasification-SCL processes are significantly cleaner and more energy efficient. The proposed integrated system can achieve a net energy efficiency of about 70% with almost 100% carbon capture.

Abstract As an alternative to thermoelectric generators, heat engines show great interest thanks to their ability to convert temperature spatial gradient into time-domain temperature variations or vibrations. To this end, MultiPhysic Memory Alloys (MPMAs), combining shape memory characteristics with ferromagnetic properties, provide significant attractive characteristics such as sharp transition with reduced hysteresis as well as magnetic properties enabled by heating, thus allowing easier device development and implementation. In this study, we report the development of a heat engine for small-scale energy harvesting where the MPMA transfers its heat to a pyroelectric element that provides thermal to electrical energy conversion, yielding a more direct energy conversion path compared to conventional electromechanical heat engines. Furthermore, thermally decoupling the pyroelectric element from the MPMA allows a faster cooling of the latter, accounting for higher variation frequency. Compared to the use of electromagnetic transduction through a coil attached to the moving MPMA, this approach is shown to provide 3 to 9 times more power density (according to considered volume), with theoretical potential gains from 8 to 25 with the use of nonlinear electrical interfaces.

The virtual energy storage system (VESS) is one of the emerging novel concepts among current energy storage systems (ESSs) due to the high effectiveness and reliability. In fact, VESS could store surplus energy and inject the energy during the shortages, at high power with larger capacities, compared to the conventional ESSs in smart grids. This study investigates the optimal operation of a multi-carrier VESS, including batteries, thermal energy storage (TES) systems, power to hydrogen (P2H) and hydrogen to power (H2P) technologies in hydrogen storage systems (HSS), and electric vehicles (EVs) in dynamic ESS. Further, demand response program (DRP) for electrical and thermal loads has been considered as a tool of VESS due to the similar behavior of physical ESS. In the market, three participants have considered such as electrical, thermal and hydrogen markets. In addition, the price uncertainties were calculated by means of scenarios as in stochastic programming, while the optimization process and the operational constraints were considered to calculate the operational costs in different ESSs. However, congestion in the power systems is often occurred due to the extreme load increments. Hence, this study proposes a bi-level formulation system, where independent system operators (ISO) manage the congestion in the upper level, while VESS operators deal with the financial goals in the lower level. Moreover, four case studies have considered to observe the effectiveness of each storage system and the simulation was modeled in the IEEE 33-bus system with CPLEX in GAMS.

Abstract A promising and shortly emerging energy supply chain network based on residential-scale microgeneration through micro combined heat and power systems is proposed, modeled and optimized in this work. Interchange of electrical energy can take place among the members of this domestic microgrid, which is connected to the main electrical grid for potential power interchange with it. A mathematical programming framework is developed for the operational planning of such energy supply chain networks. The minimization of total costs (including microgeneration system’s startup and operating costs as well as electricity production revenue, sales, and purchases), under full heat demand satisfaction, constitutes the objective function in this study. Additionally, an alternative microgrid structure that allows the heat interchange within subgroups of the overall microgrid is proposed, and the initial mathematical programming formulation is extended to deal with this new aspect. An illustrative example is presented in order to highlight the particular significance of selecting a proper optimization goal that thoroughly takes into account the major operational, technical and economic driven factors of the problem in question. Also, a number of real-world size case studies are used to illustrate the efficiency, applicability and the potential benefits of the microgeneration energy supply chain networks suggested in this study. Finally, some concluding remarks are drawn and potential future research directions are identified.

The multi-effect distillation with thermal vapour compression (MED-TVC) desalination system is efficient to produce freshwater. The steam ejector performance is not fully understood as the phase transition has been ignored in many studies. The present work develops a two-phase condensing flow model to assess the steam ejector performance considering nonequilibrium condensation phenomena. The transition of the flow structure from an under-expanded flow to an over-expanded flow in the steam ejector is investigated in detail. We present that the maximum Mach number can reach 4.02 in the under-expanded flow, which is weakened to 2.88 in the over-expanded flow. The steam undergoes several expansion-compression processes in the steam ejector in the under-expanded flow, which induces the formation and evaporation of massive droplets. In the over-expanded flow, the steam is compressed and then expanded after leaving the primary nozzle and the condensation process is not observed in mixing and constant sections. The increasing suction chamber pressure significantly improves the entrainment ratio while leading to an increasing entropy loss coefficient. The entrainment ratio is improved from 0.25 for the under-expanded flow to 1.69 for the over-expanded flow, while the entropy loss increases from 0.081 for the under-expanded flow to 0.29 for the over-expanded flow. This indicates that the transition of the flow structure from an under-expanded flow to an over-expanded flow can entrain more steam from the last effect while causes more entropy losses in a steam ejector for the MED-TVC desalination system.

Abstract In order to account for variations in the performances of buildings, it is necessary to construct explanatory models of water and energy consumptions. In this paper, a modelling approach is illustrated for those parts of the variances in consumptions of water and energy that are neglected in conventional monitoring and targeting procedures. It is shown that these parts of the consumption variance need not be random and that identifying an autoregressive component can generate better models. Additionally, conventional procedures do not exploit the seasonality that is common in many buildings. Such improved models permit the more reliable detection of significant changes in a building’s performance, and more accurate estimations of the effects of changes, whether the result of plant faults or operator intervention.

Abstract We investigate the prospects of three zero-emission scenarios for achieving the target of limiting global mean temperature rise to 2 °C or below, and compare them with the business-as-usual (BAU) scenario involving no climate policy intervention. The “2100 zero” emissions scenario requires zero emissions after 2100 until 2150. The “350 ppm zero” emissions scenario entails zero emissions in the latter half of this century, which can be achieved by the cumulative emissions constraints of the Wigley–Richels–Edmonds (WRE) 350 from 2010 to 2150. Finally, the “net zero” scenario requires zero cumulative emissions from 2010 to 2150, allowing positive emissions over the coming several decades that would be balanced-out by negative emissions in the latter half of the century. The role of biomass energy carbon capture and storage (BECCS) with forested land is also assessed with these scenarios. The results indicate that the 2 °C target can be achieved in the “net zero” scenario, while the “350 ppm zero” scenario would result in a temperature rise of 2.4 °C. The “2100 zero” scenario achieved a 4.1 °C increase, while the BAU reached about 5.2 °C. BECCS contributed to achieving zero-emission requirements while providing a limited contribution to energy supply. The findings indicate substantial future challenges for the management of forested land.