Specific Electrical Energy Consumption Research Articles

Thermal management of water electrolysis using membrane distillation to produce pure water for hydrogen production

When electrolysis units are used for water splitting to provide green hydrogen, waste heat must be dissipated to avoid performance degradation. Therefore, the hypothesis was that if a membrane distillation unit could use the waste heat to desalinate the feed water, then the operating costs may be reduced. This study demonstrated the first integration of a 0.03 m2 active area membrane distillation heat exchanger (MDHX) system with a 2.2 kW commercial electrolyser. The MDHX system satisfied the thermal requirements of the electrolysis unit. It was estimated that for a 2GW electrolysis plant, it could result in annual savings of up to $2 million. During operation with the 2.2 kW electrolyser, the MDHX unit was able to produce 50 % of the permeate rate required to match the water consumption of the electrolyser. Experimentally the MDHX system operated with a specific electrical energy consumption of 230 kWh/m3. Design changes such as improving pump efficiency and optimising flow field geometry to allow for lower flow rates, suggest there is scope for reduction in energy consumption. Indeed, further development of the MDHX technology is necessary before it can compete with large-scale seawater reverse osmosis (SWRO) methods.

Electric energy consumption (EEC) in groundwater-based drinking water supply systems: analysis and comparison of seven Italian case studies

ABSTRACT Drinking water and wastewater services depend on energy: electric energy consumption (EEC) of this sector amounts to 2–3% of global EEC. The attention of the scientific community and of water utilities about this topic is focused on energy optimization of wastewater treatment plants and pumping stages in drinking water supply systems (DWSSs). However, because of increasingly stringent regulations and because of more and more extended water-source pollution, the need for ‘unconventional’ drinking water treatment systems, which are very energy-intensive, will bring treatment to be a key factor in this scenario. Analyzing EEC in seven full-scale DWSSs, we wanted to control EEC in every single stage of the DWSS (withdrawal, drinking water treatment plant (DWTP) and distribution) and to identify opportunities for reducing energy consumption in DWSS, with a special focus on each drinking water treatment process. The most energy-intensive unconventional treatment turns out to be membrane filtration by reverse osmosis (for which specific consumption per cubic meter of pumped water is equal to 0.243 Wh/m3), whereas the most energy-intensive conventional treatment turns out to be air oxidation (specific EEC from 0.012 to 0.087 kWh/m3). The main strategies for energy conservation can be applied both in management and in the design phase.

Towards sustainable water management for Galdieria sulphuraria cultivation

The red microalga Galdieria sulphuraria has emerged as a promising biotechnological platform for large-scale cultivation and production of high-value compounds, such as the blue pigment phycocyanin. However, a large amount of freshwater and a substantial supply of nutrients challenge both the environmental and the economic sustainability of algal cultivation. Additionally, the extremophilic nature of Galdieria sulphuraria requires cultivation in an acidic culture medium that directly leads to strongly acidic wastewater, which in turn generally exceeds legal limits for industrial wastewater discharge. This research aims to address these challenges, by investigating cultivation water reuse as a strategy to reduce the impacts of Galdieria sulphuraria management. The results indicated that a 25 % water reuse may be easily implemented and showed to be effective at the pilot scale, providing no significant changes in microalgae growth (biomass productivity ~0.21 g L−1 d−1) or in phycocyanin accumulation (~ 10.8 % w/w) after three consecutive cultivation cycles in reused water. Moreover, a single cultivation cycle with water reuse percentages of 71 and 98 %, achieved with membrane filtration and with centrifugation, respectively, was also successful (biomass productivity ~0.24 g L−1 d−1). These findings encourage freshwater reuse implementations in the microalgae sector and support further investigations focusing on coupling cultivation and harvesting in continuous, real-scale configurations. Centrifugation and membrane filtration required substantially different specific electrical energy consumption for water reuse and biomass concentration: in real applications, the former technique would roughly span from 1 to 10 kWh m−3 while the latter is expected to fall within the ample range 0.1–100 kWh m−3, strongly dependent on system size. For this reason, the most suitable separation train should be chosen on a case-by-case basis, considering the prevailing flow rate and the target biomass concentration factor targeted by the separation process.

Electrocoagulation efficiency probed using electrochemical impedance spectroscopy

Electrocoagulation efficiency probed using electrochemical impedance spectroscopy

Power consumption of electric centrifugal pumping plants under extraction of highly watered oil

Relevance. Currently, oil fields in Russia are mainly developed using the method of artificial maintenance of reservoir pressure to achieve high oil recovery. The use of artificial impact on productive formations by the method of water injection contributes to the premature irrigation of production wells. Water content of productive layers in oil fields significantly complicates the technology of oil production. With the increase in water content of the surface fluid, the power consumed by the engine increases. Minimization of energy consumption is quite relevant, as oil is produced with significant expenditures of electrical energy. It is important to investigate the dependences of the electric energy consumption on the well water cut. Aim. To study the dependence of energy consumption of submersible electric centrifugal units operated in oil production wells on water cut. Methods. Submersible electric centrifugal installations for oil production. Results. In order to study the effects of formation water cut on electrical energy specific consumption, wells with a water cut of more than 90% were selected. Using the formula, the authors have calculated the electrical energy specific consumption for oil production. The analysis of the results of the calculated data showed that in producing wells with a water cut of up to 90 %, the average specific electric power consumption for oil production is within the recommended standards. In wells with the water cut more than 90%, the average specific electric power consumption for oil production exceeds recommended specific norms of electric energy consumption during operation of oil producing wells equipped with electric centrifugal installations. Based on calculated data, the dependence of the specific electrical energy consumption for oil production on the water cut of reservoir products was plotted, and wells with a water cut of more than 90% were selected. The analysis of the graphical dependence showed that in wells with an oil water cut of more than 90%, the specific energy consumption reaches maximum values ​​(the specific energy consumption increases by 40%).

Multi-stage humidification–dehumidification system integrated with a crystallizer for zero liquid discharge of desalination brine

Desalination plants discharge a massive volume of brine every day, which negatively affects the ecosystem, particularly the subsurface ecology and marine life. To mitigate the brines' detrimental effects on the environment and facilitate the recovery of salt crystals and freshwater, the Zero Liquid Discharge (ZLD) approach was proposed. This study proposes four different configurations of multistage humidification dehumidification systems integrated with a crystallizer, exploring their energy and economic implications. Key findings from the study include the higher Gained Output Ratio (GOR) in series configurations due to lower temperature differences, resulting in lower heater energy consumption. The crystallizer significantly enhances water productivity, but it is a major consumer of both electricity (85%) and thermal energy (50.45–57.7%) in the system. Increasing the heat source temperature reduces the Specific Electrical Energy Consumption (SEEC) and the specific area while slightly increasing the Specific Thermal Energy Consumption (STEC). Elevated cooling water temperature raises SEEC and specific area but has negligible effects on STEC. Higher feed water flow rates increase SEEC but lower both STEC and specific area. Feed salinity elevation decreases productivity, SEEC, STEC, and specific area. The crystallizer constitutes 15.43–26.44% of the total capital cost, with series configurations incurring higher costs. Unit freshwater production costs, considering salt selling, range from 1.733 to 4.821 $.m−3. In a waste heat scenario, parallel configurations become profitable, where freshwater can be distributed at zero cost, while the produced salt crystals can be sold at an even lower price of $58.09 per tonne and $57.04 per tonne, respectively.

Performance investigation of poly(vinylidene fluoride-cohexafluoropropylene) membranes containing SiO2 nanoparticles in a newly designed single vacuum membrane distillation system.

The current study focuses on the development of a superhydrophobic poly(vinylidene fluoride-cohexafluoropropylene) nanocomposite membrane suitable for vacuum membrane distillation by incorporating SiO2 nanoparticles. At loading hydrophobic nano-SiO2 particle concentration (0.50-1.50 wt.%), the developed nanocomposite membranes are optimized in terms of vacuum membrane distillation performance. The influence of temperature, vacuum pressure, and feed water flow is studied for desalinating high-salinity brine. The results show that the developed vacuum distillation membrane is capable of 95% salt rejection during the treatment of a highly saline feed (65,000 ppm) at fixed flow rates of 120L/h saline feed and different operating conditions consisting of feed inlet temperatures ranging from 40°C to 70°C and distillate inlet temperatures of 7-15°C. The vacuum membrane distillation process achieves 0.38-1.66% water recovery with increasing concentration factor, meaning that recovery is increased, and shows a specific electrical energy consumption of 5.16-23.90 kWh/m3 for product water. Overall, the newly designed membrane demonstrates suitability for a vacuum membrane distillation system. PRACTITIONER POINTS: Desalinate high-salinity brine (TDS > 35,000 ppm) using a vacuum membrane distillation system. A hydrophobic PVDF-HFP/SiO2 nanocomposite membrane development for vacuum membrane distillation. A newly designed single vacuum membrane distillation system for RO brine treatment.

THERMODYNAMIC ANALYSIS OF THE HEAT PUMP-ADSORPTION AIR DRYING SYSTEM USING A RECOVERY

This paper describes the development of a heat pump and adsorption system that incorpo-rates a recuperator. A theoretical model is developed to analyze the system's operation numeri-cally. The study includes a numerical analysis of the thermodynamic efficiency, an examination of the changes in air parameters at different points in the system, an investigation of the impact of variations in temperature and relative humidity of the surrounding air, and also an analysis of the effect of the regeneration air temperature on the system's performance. Graphical representations of the system's efficiency are generated by modifying the parameters of the outside air and the re-generation air temperature following the heat pump condenser. The study also explores the in-fluence of the recuperator's efficiency on the overall energy efficiency of the system. The results demonstrate that this advanced system significantly reduces the specific electrical energy con-sumption for air drying compared to systems lacking a recuperator or a recuperator and a heat pump, regardless of the outdoor air parameters.

Influence of internal design on the performance of pilot vacuum-assisted air-gap membrane distillation modules for brine concentration with solar energy

Membrane distillation (MD) in batch operation is proposed for brine concentration with solar energy in zero liquid discharge (ZLD) desalination processes, but there are some research gaps yet. Energy efficiency is key for implementing the technology with solar energy and there is not enough experience and experimental results of operation of MD pilot modules at high salinity feeds. This research focuses on the experimental evaluation and comparison of two multi-envelope spiral wound commercial membrane distillation modules operating in vacuum-assisted air gap MD at the solar MD pilot facilities of Plataforma Solar de Almería in Spain. These modules have similar membrane area (24 and 25.9 m2) and residence time (large, to maximize thermal efficiency), but different internal design: 6 envelopes 5 m long and 12 envelopes 2.7 m long, respectively. This difference affects mostly the feed circulation velocity for equal feed flow rate. Performance parameters such as permeate production and specific thermal energy consumption (STEC) are compared and experimental models performed and validated for different feed salinities. Permeate quality and specific electrical energy (SEEC) consumption are also evaluated. The results show that the best module for batch operation is the one with a larger number of channels but of shorter length.

Electrified steam methane reforming of biogas for sustainable syngas manufacturing and next-generation of plant design: A pilot plant study

Electrification of the traditional steam methane reforming (SMR) technology for syngas manufacturing has a significant CO2 reduction potential and make it more feasible to operate in combination with carbon capture/utilization, especially if renewable electricity is used. This pilot plant study demonstrates the first operational experience with industrial-scale electrified steam methane reforming (eSMR) technology using biogas as sustainable carbon feedstock. Across an operating envelope spanning from combinations of 5 to 20 barg and 750 °C to 1000 °C, the eSMR produces syngas as expected from thermodynamics. However, without the thermal restrictions inherent in the SMR design, the eSMR can achieve higher temperatures, enables fast transient operation, with high stability and control, thereby increasing the overall performance and design flexibility. Initial thermal responses of the eSMR were tested, demonstrating fast start-up from an idle state to operating conditions, within 2.6 h, including heating from 630 °C to 900 °C. Furthermore, dynamic temperature control was also demonstrated with heating rates up to 330 °C/h. Experimental energy efficiency of the pilot reactor was quantified between 72 % and 80 %, with the residual being heat loss to the surroundings due to the relatively small scale. With further scale-up to ≥1 MW reactor capacity, efficiencies of ≥99 % are predicted with a specific electrical energy consumption of 1.0 kWh/Nm3 H2. Overall, the efficiency and operational flexibility are improved due to the direct electrical heating of the catalytic system. Combined with biogas as feedstock, this paves the way for attractive and competitive plant designs for sustainable and renewable production of chemicals and fuels.

The Energy-Saving Control Criterion for Impact Crushing Machines

The purpose of the article is to substantiate the use of a new criterion for controlling the grinding technological process to improve the use of electrical energy. The subject of the study is the process of using electrical energy in impact grinding machines. The set goal is achieved by solving the following problems: analyzing the energy of the grinding process, determining the parameters of raw materials and operating modes of the electric drive that affect the efficiency of electrical energy usage. Based on theoretical research, a mathematical model of energy consumption in grinding processes has been developed. Analytical studies of the resulting mathematical model showed the nonlinear extreme nature of the specific energy consumption of the grinding process with changing raw material parameters and operating modes. This creates the prerequisites both for using specific electrical energy costs as a control criterion and for the use a controlled electric drive to achieve maximum energy savings. The most important result is that the operating modes of grinding machines could be established by more efficient use of electrical energy. The significance of the work lies in the fact that by adapting the operating modes of the electric drive to the current parameters of the raw materials and the state of the equipment make possible to reduce the specific electrical energy consumption up to 15% and this is the basis for using a criterion based on specific costs in control systems for technological processes with grinding impact machines. For further application of the obtained results it is necessary to conduct experimental studies to confirm the increase in the efficiency of electrical energy use.

Theoretical, numerical and experimental research on an innovative ocean thermal energy conversion coupled VMD desalination system

This paper proposes an OTEC-VMD desalination system that fully exploits tropical ocean thermal energy to alleviate freshwater shortages on remote islands, with no need of coupling with other heat sources. Based on an in-depth analysis of the mass and heat transfer theory of the OTEC-VMD desalination, a CFD model is established by embedding a UDF program in commercial software and an experimental prototype with a water production capacity of 1 kg/h is designed and manufactured. The CFD simulation and experimental test results show good agreement, with relative errors around 5 %. The proposed system can stably produce water, demonstrating the feasibility of OTEC-VMD seawater desalination experimentally for the first time. At a warm seawater temperature of 30 °C, the water production reaches 1.07 kg/h, achieving the design target. The system's water recovery ratio and specific electrical energy consumption are 0.254 % and 2.62 kWh/m3, respectively, and the TDS is lower than 5 mg/L. Compared to low-pressure flashing, the equipment achieves an average volume reduction rate of 94.71 %, making it more suitable for installation and transportation in remote marine locations, with great potential in replacing the low-pressure flashing device in the open-cycle of OTEC power plant to promote the large-scale application of OTEC technology.

Experimental performance of a spray tower system for water desalination and indoor thermal comfort

Present work characterizes a spray tower-based desalination system, designed to simultaneously provide fresh water by condensation and supply dehumidified air to occupied spaces. Its configuration is open air-open water, with Celdek 7090 packing in the humidification section and water-cooled helical coils for dehumidification. The performance parameters calculated are: gained output ratio, recovery ratio, coefficient of performance, specific electrical energy consumption, mass ratio, humidification, and dehumidification efficiency. This performance is analyzed for varying air Reynold’s number and water flow rate. The best results were obtained for the sea water flow rate tested of 18 liters per hour, and showed maximum humidification efficiency, dehumidification efficiency, COP, freshwater rate, gained output ratio and concentration factor equal to 87.14%, 94.56%, 3.34, 0.9 liters per hour and 1.05, respectively. Exit air meets the thermal comfort requirements which avoids the ventilation thermal loads in the space cooling.

TEMPERATURE OF THE COMPRESSOR SUCTION AIR AND ITS INFLUENCE ON THE EFFICIENT OPERATION OF THE COMPRESSOR UNIT

The climatic conditions of Uzbekistan are characterized by relatively long summers with air temperature of 40-45 0C and higher, which is the reason of significant heating of air suctioned by compressor. Increase in temperature and corresponding decrease inair density contributes to 8-10% decrease in compressor unit productivity, leading to significant economic losses in the process of compressed air production. By means of artificial cooling of suction air at the inlet to the compressor unit it is possible to increase the energy efficiency of operation of the mine reciprocating compressor unit.The effectiveness of artificial air temperature reduction depends on the amount of temperature reduction and the type of plant drive, as well as on the purpose -toreduce the specific electric energy consumption for compression or to increase the capacity of the reciprocating compressor.

Combining machine learning with multi-physics modelling for multi-objective optimisation and techno-economic analysis of electrochemical CO2 reduction process

As a carbon capture and utilization (CCU) technology, gas diffusion electrode (GDE) based electrochemical CO2 reduction reaction (eCO2RR) can convert CO2 to valuable products, such as formate and CO. However, the electrode parameters and operational conditions need to be studied and optimised to enhance the performance and reduce the net cost of the eCO2RR process before its industrial application. In this work, a machine learning algorithm, i.e., extended adaptive hybrid functions (E-AHF) is combined with a multi-physics model for the data-driven three-objective optimisation and techno-economic analysis of the GDE-based eCO2RR process. The effects of eight design variables on the product yield (PY), CO2 conversion (CR) and specific electrical energy consumption (SEEC) of the process are analysed. The results show that the R2 of the E-AHF model for the prediction of PY, CR and SEEC are all higher than 0.96, indicating the high accuracy of the developed machine learning algorithm for the prediction of the eCO2RR process. The process performance experiences a notable improvement after optimisation and is affected by a combination of eight variables, amongst which the electrolyte concentration having the most significant impact on PY and CR. The optimal trade-off single-pass PY, CR and SEEC are 3.25×10−9 kg s−1, 0.663% and 9.95 kWh kg−1 based on flow channels with 1 cm in length, respectively. The SEEC is reduced by nearly half and PY and CR are improved more than two times after optimisation. The production cost of the GDE-based eCO2RR process was approximately $378 t−1product (CO and formate), much lower than that of traditional CO2 utilisation factories ($835 t−1product). The electricity cost accounted for more than 80% of the total cost, amounting to $318 t−1, indicating that cheaper and cleaner electricity sources would further reduce the production cost of the process, which is the key to the economics of this technology.

Saline wastewater treatment by bioelectrochemical process (BEC) based on Al-electrocoagulation and halophilic bacteria: optimization using ANN with new approach

ABSTRACT In the present study, a bioelectrochemical reactor (BEC) was utilized to treat two types of real saline produced water (PW). BEC was designed based on the combination of electrocoagulation (EC) process with halophilic microorganisms, and it was assessed in terms of biodegradation of hydrocarbons. The effects of various operating parameters including the current density, electrical contact time (On/Off), hydraulic retention time (HRT), and total dissolved solids (TDS) at different levels on the chemical oxygen demand (COD) removal efficiency, settleability, and performance of isolated halophilic microorganisms were examined. Additionally, a novel neural network (ANN) approach modelling using adaptive factors was used to predict and optimize the effects and interactions between operating parameters during BEC process by predicting complicated mechanisms and variations associated with microorganisms. In addition, a new algorithm was developed for the sensitivity analysis to achieve the optimum operating conditions and obtain maximum efficiency in COD removal, sludge volume index (SVI), mixed liquor suspended solids (MLSS), and specific electrical energy consumption (SEEC), simultaneously. BEC was found to be significantly more effective at removing most hydrocarbons, particularly pristine and phytane. In addition, the results showed a significant improvement in settling ability of the biological flocs with average SVI of 91.5 mL/g and a size of 178.25 μm using BEC. Based on estimated operating costs and energy consumption, BEC was more cost-effective and efficient than other bioelectrochemical systems.

Electrocoagulation treatment of paint wastewater from equipment cleaning and conversion of by-product sludge into nano-pigment

This work aims to treat paint wastewater from industrial equipment cleaning by electrocoagulation (EC) using aluminum electrodes and reusing residual sludge as a starting material for synthesizing a blue inorganic nano-pigment. An initial pH of the wastewater without adjustment, a current density of 133.33 A/m2, an electrolysis time of 30 min and an inter-electrode distance (IED) of 2 cm were the best operating conditions for EC. The reduction rate of COD and turbidity was about 92% and 99.6%, respectively. At optimum conditions, specific metal consumption and specific electrical energy consumption are about 0.168 kg/m3 and 15 kWh/m3, respectively. The paint wastewater treatment sludge (PWTS) from EC was first characterized and then mixed with cobalt(II) chloride to synthesize an inorganic blue nano-pigment. The effects of Co/Al molar ratios and temperatures were studied. From colorimetric data, the pigment obtained at 1100 °C is more bluish than those synthesized at a lower temperature. This study will have beneficial effects on the environment as well as on the economy because it makes it possible to transform PWTS into value-added products. Treated wastewater can be reused for paint equipment cleaning and EC sludge can be completely transformed into pigment. The zero-waste principle can therefore be achieved.

Analytical investigation of the dew point water recovery system with potential application for drinking water production

The article presents the analytical investigation of the Dew Point Water Recovery (DPWR) system with potential application for drinking water production. Four different configurations of the DPWR system were proposed, differing in the number and type of dew point cooling exchangers used, and their operation was described using a validated convective heat transfer coefficient mathematical model. It was found that the three stage configuration of the DPWR system with a regenerative exchanger has the best water recovery performance, while the three stage configuration with a counter-flow exchanger has the best ratio of energy supplied to the system in relation to the amount of water produced. It was also found that the DPWR system can operate in a wide range of operating conditions with a specific electric energy consumption reaching below 0.9 kWh/m3 and GOR in the range of 0.36–2.16. What distinguishes the DPWR system from other methods of drinking water production is the ability to work without an additional source of thermal energy apart from the energy of the air supplied to the system. Thanks to this property, the system has the potential to fill the technological gap of a low-energy and easily accessible method of drinking water production.

Shape-controlled synthesis of lead dioxide nanoparticles for enhanced electrocatalysis of electrochemical ozone production

Shape-controlled nanomaterials of PbO2 have attracted considerable attention in designing highly efficient electrocatalyst, since the physicochemical properties of PbO2 vary from their structure and morphology. PbO2 materials demonstrating promising ability in electrochemical ozone production (EOP) have attracted the focus of research recently, and therefore boost the strategical improvement in their key performance, such as electroactivity, current efficiency and space-time yield. In this work, the PbO2 crystals with controllable structures of rod-like, sphere-like as well as star-like PbO2 were acquired to explore their physicochemical properties and EOP performance systemically. Among the samples, PbO2 nanorods, benefitting from their abundant active surface chemisorbed oxygen, exhibit relatively high electrocatalytic activity towards EOP. Such structural feature is beneficial for triggering the generation of a rapid charge, improving mass transfer, and subsequently enhancing the corresponding electrocatalytic reactions. A maximum EOP current efficiency of 14% was achieved by the PbO2 nanorod electrode at a cell potential of 4.0 V corresponding to a specific electric energy consumption of 101.53 kWh·(kg·O3)−1. Overall, an in-depth understanding of the nanostructure–performance relationship of PbO2 and EOP performance is demonstrated in this work, which can provide an insight into the rational design of PbO2 for the EOP.

Analysis of the Specific Energy Consumption of Battery-Driven Electrical Buses for Heating and Cooling in Dependence on the Technical Equipment and Operating Conditions

This paper analyzes methods of heating battery-driven electrical buses. The examined buses were two identical airport transport buses and two buses used in local transportation. To heat the first buses, an electrical water heater with a heating capacity of 20 kW, and for air conditioning, a rooftop air conditioner with a cooling capacity of 20.6 kW was installed. Climate control in the city buses was achieved using an R744 heat pump with a cooling capacity of 25 kW and a heating capacity between 14 and 21 kW, along with an electrical water heater with a capacity of 32 kW. During the project, the measurement data of the buses described above were taken for a full year and evaluated. The analysis of the measurement data brought insights into the specific electrical energy consumption of climate control in the buses in real operating conditions at outdoor temperatures between 2 °C and 36 °C. The results of this project additionally provide information on the optimization potential for the climate control of buses.