Selecting the sizes of distributed energy resources is a central planning element when designing a microgrid. Decision makers may consider several important factors, including, but not limited to, capacity, cost, reliability and sustainability. We introduce a method for rightsizing capacity that presents a range of potential microgrid design solutions, allowing decision makers to weigh their upsides and downsides based on a variety of measurable factors. We decouple component-specific modeling assumptions, energy management system logic and objective measurements from our simulation-based nested binary search method for rightsizing to meet power loads. In doing so, we develop a flexible, customizable and extensible approach to microgrid design planning. Aspects which have traditionally been incorporated directly in optimization-centric frameworks, such as resilience and reliability, can be treated as complementary analyses in our decoupled approach. This enables decision makers to gain... [more]

The digestate is a prospective biofertilizer and potential source of income for many biogas plants worldwide. However, its actual impact on the soil properties and biomass yield is still unexploited. The different digestates from eight agricultural biogas plants were researched in terms of their chemical composition and the fertilizing potential. The results obtained from digestate chemical analysis indicate that the digestate biomass had large amount of nitrogen (up to 73 g kg−1 fresh mass) and potassium (up to 25 g kg−1 fresh mass). The value of the digestate was estimated in the range of 2.88−7.89 EUR Mg−1 for liquid digestate and 7.62−13.61 EUR Mg−1 for solid digestate based on the commercial fertilizer market price of nitrogen, potassium phosphorus, organic carbon, Cu, Zn, Fe and Mg. The digestate produced at the 1 MW biogas plant is worth EUR 941−2095 per day in addition to energy sales income. The application of digestate on low-fertility land in areas close to the biogas plant... [more]

Photovoltaic panel efficiency can be heavily affected by soiling, due to dust and other airborne particles, which can determine up to 50% of energy production loss. Generally, it is possible to reduce that impact by means of periodic cleaning, and one of the most efficient cleaning solutions is the use of demineralized water. As pauperization of traditional water sources is increasing, new technologies have been developed to obtain the needed water amount. Water extracted from the air using air to water generator (AWG) technology appears to be particularly suitable for panel cleaning, but its effective employment presents issues related to model selection, determining system size, and energy efficiency. To overcome such issues, the authors proposed a method to choose an AWG system for panel cleaning and to determine its size accordingly, based on a cleaning time optimization procedure and tailored to AWG peculiarities, with an aim to maximize energy production. In order to determine th... [more]

Ultrathin Cu(In,Ga)Se2 (CIGS) absorber layers of 550 nm were grown on Ag/AlOx stacks. The addition of the stack resulted in solar cells with improved fill factor, open circuit voltage and short circuit current density. The efficiency was increased from 7% to almost 12%. Photoluminescence (PL) and time resolved PL were improved, which was attributed to the passivating properties of AlOx. A current increase of almost 2 mA/cm2 was measured, due to increased light scattering and surface roughness. With time of flight—secondary ion mass spectroscopy, the elemental profiles were measured. It was found that the Ag is incorporated through the whole CIGS layer. Secondary electron microscopic images of the Mo back revealed residuals of the Ag/AlOx stack, which was confirmed by energy dispersive X-ray spectroscopy measurements. It is assumed to induce the increased surface roughness and scattering properties. At the front, large stains are visible for the cells with the Ag/AlOx back contact. An a... [more]

In the last years, a change in the power generation paradigm has been promoted by the increasing use of renewable energy sources combined with the need to reduce CO2 emissions. Small and distributed power generators are preferred to the classical centralized and sizeable ones. Accordingly, this fact led to a new way to think and design distributions grids. One of the challenges is to handle bidirectional power flow at the distribution substations transformer from and to the national transportation grid. The aim of this paper is to review and analyze the different mathematical methods to design the architecture of a distribution grid and the state of the art of the technologies used to produce and eventually store or convert, in different energy carriers, electricity produced by renewable energy sources, coping with the aleatory of these sources.

The purpose of this paper is to establish if Marshallian and Jacobian knowledge spillovers affect job creation in the green energy sector. Whether these two effects exist is important for the number of jobs created in related fields and jobs pushed away in other sectors. In the analysis, the production efficiency, in terms of jobs and job spillovers, from inventions in solar, wind and energy efficiency, is explored through data envelopment analysis (DEA), based on the Malmquist productivity index, and tobit regression. A panel dataset of American and European firms over the period of 2002−2017 is used. The contribution to the literature is to show the role of the spillovers from the same technology sector (Marshallian externalities), and of the spillovers from more diversified activity (Jacobian externalities). Since previous empirical evidence concerning the innovation effects on the production efficiency is yet weak, the paper attempts to bridge this gap. The empirical findings sugge... [more]

In this paper an optimization problem designed to calculate electric grid specific indicators to be used within model-based methodologies for the definition of alternative electricity market bidding zone configurations is designed. The approach integrates within the framework of a bidding zone review process aligned to the specifications of the Commission Regulation (EU) 2015/1222 (CACM) and Regulation (EU) 2019/943 of the European Parliament and of the Council (CEP). The calculated solution of the optimization provides locational marginal prices and allows to determine, outside the optimization problem, the power transfer distribution factors for critical elements. Both indicators can be used as inputs by specially designed clustering algorithms to identify model-based electricity market bidding zone configurations, as alternative to the current experience-based configurations. The novelty of the optimization problem studied in this paper consists in integrating the N-1 security crite... [more]

The negative impacts of catastrophic fire and explosion accidents due to copper corrosion problems of oil-filled electrical transformers are still in the spotlight due to a lack of effective methods for early fault detection. To address this gap, a condition monitoring (CM) procedure that can detect such problems in the initial stage is proposed in this paper. The suggested CM procedure is based on identified measurable variables, which are the relevant by-products of the corrosion reaction, and utilizes an Early Fault Diagnosis (EFD) model to detect and solve the copper corrosion problems. The EFD model includes a fault trend chart that can track a fault progression during the useful life of transformers. The purpose of this paper is to verify and validate the effectiveness of the suggested CM procedure by an empirical study in a power plant. The result of applying this procedure was early detection of copper corrosion problems in two transformers with suspected copper corrosion propa... [more]

The present research assesses the influence of globalization and technological innovation on CO2 emissions in South Korea as well as taking into account the role of renewable energy consumption and energy consumption utilizing datasets between 1980 and 2018. The autoregressive distributed lag (ARDL) bounds testing method is utilized to assess long-run cointegration. The outcome of the ARDL bounds test confirmed cointegration among the series. Furthermore, the ARDL reveals that economic growth, energy consumption and globalization trigger environmental degradation while technological innovation improves the quality of the environment. In addition, the study employed the frequency domain causality test to capture causal linkage among the series. The major advantage of this approach is that causal linkage between series can be captured at the short, medium and long term, respectively. The outcomes of the causality test revealed that globalization, technological innovation, economic growth... [more]

In the latest research, it has been proven that from the point of view of losses in a cable distribution line, the most advantageous operation is to work with two or one phase of metallic cable screen ungrounded. However, such an operation may cause changes in the network characteristics and thus the occurrence of undesirable phenomena. One of those characteristics is the overvoltages in those cable screens, which can lead to cable line damage. The simulation tests presented in this article are closely related to the unusual method of operation of the MV cable screens and their performance, and they address the question of whether in a given system ground fault overvoltages may be a significant threat to the operation of the cable. The research methods used to verify these risks are related to the simulation of the cable line operating states using the DIgSILENT PowerFactory program (DIgSILENT GmbH, Gomaringen, Germany). Overvoltage simulations were performed, taking into account chang... [more]

According to the requirements of nuclear safety regulations, nuclear power plants must be equipped with seismic instrumentation systems, which are mainly used for monitoring alarm and automatic shutdown alarm during an earthquake. Both the second and third generation NPPs adopt Peak Ground Acceleration (PGA). However, among the seismic acceleration characteristics, isolated and prominent single high frequency acceleration peaks have no decisive influence on the seismic response. Especially when the earthquake monitoring alarm is at 1 out of 7, it is likely to cause a false alarm or false shutdown. In addition, it usually takes one month or more for the NPPs to restart after the shutdown. In this paper, an improved seismic instrumentation system based on the existing system is proposed. For high intensity areas, three components resultant acceleration is used to judge the 2 out of 4 logic of the automatic seismic trip system(ASTS). For low intensity areas, the seismic failure level is e... [more]

Natural radioactivity in underground locations is the main parameter for the safety of work (occupational hazards) and for the success of experiments in physics or biology requiring unique conditions. The characterization of natural prominence was carried out in the Conceptual Lab development in one of KGHM deep copper mines co-ordinated by KGHM Cuprum R&D. Natural radioactivity studies were performed and included in situ gamma spectrometry, neutron flux measurements, radon concentration, and alpha and gamma laboratory spectrometry measurements of rock samples. At a depth of 1014.4 m (2941.8 m w.e.) within the anhydrite layer, a neutron flux of 2.0 ± 0.2 × 10−6 cm−2 s−1, a gamma-ray dose of 0.008 ± 0.001 μSv/h, a photon flux density of 0.64 ± 0.20 cm−2 s−1, and a radon concentration of 6.6 Bq/m3 were determined. Laboratory analyses of 226,228Ra, 40K, and 238,234U concentrations in collected rock samples showed low values. The exceptionally low level of natural radioactivity in the Polk... [more]

Colloidal dye-sensitized photocatalysis is a promising route toward efficient solar fuel production by merging properties of catalysis, support, light absorption, and electron mediation in one. Metal-organic frameworks (MOFs) are host materials with modular building principles allowing scaffold property tailoring. Herein, we combine these two fields and compare porous Zr-based MOFs UiO-66-NH2(Zr) and UiO-66(Zr) to monoclinic ZrO2 as model colloid hosts with co-immobilized molecular carbon dioxide reduction photocatalyst fac-ReBr(CO)3(4,4′-dcbpy) (dcbpy = dicarboxy-2,2′-bipyridine) and photosensitizer Ru(bpy)2(5,5′-dcbpy)Cl2 (bpy = 2,2′-bipyridine). These host-guest systems demonstrate selective CO2-to-CO reduction in acetonitrile in presence of an electron donor under visible light irradiation, with turnover numbers (TONs) increasing from ZrO2, to UiO-66, and to UiO-66-NH2 in turn. This is attributed to MOF hosts facilitating electron hopping and enhanced CO2 uptake due to their innate... [more]

The research on tidal-current energy-capture technology mainly focuses on the conditions of high flow velocity, focusing on the use of differential pressure lift, while the average flow velocity in most sea areas of China is less than 1.5 m/s, especially in the marine aquaculture area, where tidal-current energy is needed to provide green energy locally. Due to the low flow velocity of this type of sea area, it seriously affects the effect of differential pressure lift, which is conducive to exerting the effect of impact resistance. In this regard, the coupling effect of the differential pressure lift and the impact resistance on the blade torque is comprehensively considered, this research puts forward the design method of the lift-−drag-composite thin-plate arc turbine blade. Based on the blade element momentum (BEM) theory and Bernoulli’s principle, the turbine dynamic model was established, and the nonlinear optimization method was used to solve the shape parameters of the turbine... [more]

Wet flue gas desulfurization (WFGD) wastewater treatment is a key problem in coal-fired plants. Traditional chemical precipitation methods cannot reach zero-liquid discharge (ZLD). In this paper, a new technology using the low-rank heat from flue gas to concentrate the wastewater for ZLD is proposed. A scrubber was built to verify the concentrating process, and the characteristics of the concentrated water were analyzed. The concentrated water was neutralized by adding Ca(OH)2 to raise the pH value. The wastewater can be concentrated 10~25 times to reduce the flow rate. The characteristics of the concentrated wastewater were studied by dosing lime. Then, liquid and solids were separated by filter pressing, the liquid was mainly composed of CaCl2, which accounts for 73.6%. The sludge is composed of CaSO4 and Mg(OH)2, depending on the lime consumption of the dosing process. Finally, the filter liquor after the filter press was mixed with ash to reach zero liquid discharge, and the sludge... [more]

Despite the recent expansion of the scope, the main pillars of energy security remain physical supply and price components. This paper highlights the novel developments of this notion, including the exporters’ perspective, relevant challenges, indicators, and policies. Furthermore, we apply the portfolio theory approach to five Gulf Cooperation Council countries to construct portfolios representing the trade-offs between maximizing returns (oil export growth or export prices) and minimizing risks (standard deviation of return variables). We assess portfolios’ resilience to external demand and logistical shocks by running several disruptive scenarios. We find that oil exporters adopt a balanced approach to the risks associated with export volume growth and pricing, which is different from some major oil importers that prioritize either the physical supply or price stability. Simulation scenarios of increasing oil exports to China would have a significant impact mainly on Saudi Arabia an... [more]

Rooftop photovoltaic (PV) systems are usually behind the meter and invisible to utilities and retailers and, thus, their power generation is not monitored. If a number of rooftop PV systems are installed, it transforms the net load pattern in power systems. Moreover, not only generation but also PV capacity information is invisible due to unauthorized PV installations, causing inaccuracies in regional PV generation forecasting. This study proposes a regional rooftop PV generation forecasting methodology by adding unauthorized PV capacity estimation. PV capacity estimation consists of two steps: detection of unauthorized PV generation and estimation capacity of detected PV. Finally, regional rooftop PV generation is predicted by considering unauthorized PV capacity through the support vector regression (SVR) and upscaling method. The results from a case study show that compared with estimation without unauthorized PV capacity, the proposed methodology reduces the normalized root mean sq... [more]

This paper presents the synchronisation of economic cycles of GDP and crude oil and oil products cargo volumes in major Polish seaports. On the one hand, this issue fits into the concept of sustainable development including decoupling; on the other hand, the synchronisation may be an early warning tool. Crude oil and oil products cargo volumes are a specific barometer that predicts the next economic cycle, especially as they are primary sources of energy production. The research study applies a number of TRAMO/SEATS methods, the Hodrick−Prescott filter, spectral analysis, correlation and cross-correlation function. Noteworthy is the modern approach of using synchronisation of economic cycles as a tool, which was described in the paper. According to the study results, the cyclical components of the cargo traffic and GDP were affected by the leakage of other short-term cycles. However, based on the cross-correlation, it was proved that changes in crude oil and oil products cargo volumes... [more]

Different methods to achieve zero-energy and low carbon on the scale of a building are shown by most of the research works. Despite this, the recommendations generally offered by researchers do not always correspond to the realities found during the construction of new buildings in a determined region. Therefore, a standard may not be valid in all climate regions of the world. Being aware of this fact, a study was carried out to analyse the design of new buildings respecting the “zero-energy and low carbon emission” concept in tropical climatic regions when they are compared with a base case of temperate regions. To reach this objective, the comparison between real and simulated data from the different buildings studied was developed. The results showed that the renovation of existing residential buildings allows for reducing up to 35% of energy demand and a great quantity of CO2 emissions in both climate types. Despite this, the investment rate linked to the construction of zero-energ... [more]

There are different studies that point out that the price of electricity is a fundamental factor that will influence the mining decision, due to the cost it represents. There is also an ongoing debate about the pollution generated by cryptocurrency mining, and whether or not the use of renewable energies will solve the problem of its sustainability. In our study, starting from the Environmental Performance Index (EPI), we have considered several determinants of cryptocurrency mining: energy price, how that energy is generated, temperature, legal constraints, human capital, and R&D&I. From this, via linear regression, we recalculated this EPI by including the above factors that affect cryptocurrency mining in a sustainable way. The study determines, once the EPI has been readjusted, that the most sustainable countries to perform cryptocurrency mining are Denmark and Germany. In fact, of the top ten countries eight of them are European (Denmark, Germany, Sweden, Switzerland, Finland, Aus... [more]

The printed circuit heat exchanger (PCHE) is a promising waste heat recovery technology to improve energy efficiency. The current investigation presents the experimental results on the thermal performance of a novel PCHE for low-temperature waste heat recovery. The novel PCHE was manufactured using precision machining and diffusion bonding. The thermal performances, such as effectiveness and NTU values at different temperatures, are evaluated, and water is used as a working fluid. The experimental results indicate that the PCHE’s effectiveness is around 0.979 for an inlet flow temperature of 95 °C. The predominant factors affecting the thermal performance of the PCHE are the inlet flow temperature and the flow rate of the working fluid. In addition, a comparison of the experimental results and the literature shows that the effectiveness of the PCHE is better than the others, which have fewer layers of PCHE fins.

Gas migration through fresh and hardened cement slurry is an ongoing problem in the oil industry. In order to eliminate this unfavourable phenomenon, research is being conducted on new compositions of slurries for gas wells. The article presents the results of research for slurries with low and high resistance to gas migration. The proper selection of the quantity and quality of components makes it possible to design slurry with the required static structural strength values. In addition, the cement sheath of such anti-migration slurry has low porosity and a very low proportion of large pore spaces. Additionally, the mechanical parameters do not decrease during long-term deposition in borehole-like conditions. By obtaining these results, it was possible to design slurry whose cement sheath has high corrosion resistance. The new slurry has a lower water-cement ratio. Additionally, GS anti-migration copolymer, anti-filter additive and latex are used. The presence of n-SiO2 aqueous soluti... [more]

The most relevant electrolytes used in commercial electrical double layer capacitors (EDLCs) are based on non-aqueous solvents as acetonitrile (ACN) and propylene carbonate (PC). However, these solvents are synthesized from non-renewable fossil feedstocks, making it desirable to develop more sustainable alternatives. To address this issue, in this work lactic acid was used to synthesize a panel of substances with small structural variation. The investigated products belong to the chemical family of ketals, and among them the 5-methyl-1,3-dioxolan-4-one (LA-H,H) was found to be the most suitable to prepare electrolytic solutions. Therefore, LA-H,H was combined with triethylmethylammonium tetrafluoroborate (TEMABF4), and analyzed in symmetrical EDLC. This electrolyte was thoroughly characterized by cyclic voltammetry, galvanostatic cycles and electrochemical impedance spectroscopy (EIS), disclosing competitive performances compared to PC-based electrolyte. The EDLC with LA-H,H/TEMABF4 di... [more]

The process and energy intensifications for the synthesis of glycerol carbonate (GC) from glycerol and dimethyl carbonate (DMC) using an eggshell-derived CaO heterogeneous catalyst were investigated. The transesterification reaction between glycerol and DMC was typically limited by mass transfer because of the immiscible nature of the reactants. By varying the stirring speed, it was observed that the mass transfer limitation could be neglected at 800 rpm. The presence of the CaO solid catalyst made the mass transport-limited reaction process more prominent. Mass transfer intensification using a simple kitchen countertop blender as an alternative to overcome the external mass transfer limitation of a typical magnetic stirrer was demonstrated. A lower amount of the catalyst and a shorter reaction time were required to achieve 93% glycerol conversion or 91% GC yield, and the turnover frequency (TOF) increased almost 5 times from 1.5 to 7.2 min−1 when using a conventional magnetic stirrer... [more]

This article considers the possibility of connecting the problems of the engineering synthesis of frequency control systems for induction motor drives (IMD) with the theory of the identification of IMD based on the equations of a generalized AC electric machine. The article presents experimental studies of load parrying in IMD with vector (VC) and scalar (SC) controls. These results indicate the absence of fundamental advantages in a drive with VC. This advantage should manifest in a more efficient formation of the moment and fast transients. A method was proposed for describing IMD by nonlinear transfer functions, making it possible to formulate the principle of the correction of IMD and a method for assessing their efficiency. The article shows that the correction based on the proposed nonlinear transfer functions of the induction motor is much more efficient than the traditional VC, which was confirmed by detailed experiments and modeling. The most important results are given in the... [more]