Reduce Energy Demand Research Articles

Dynamic Simulation of Heat Distribution and Losses in Cement Kilns for Sustainable Energy Consumption in Cement Production

Sustainable energy consumption in cement production involves practises and strategies aimed at reducing energy use and minimising environmental impact. The efficiency of a cement kiln is dependent on the kiln design, fuel type, and operating temperature. In this study, a dynamic simulation analysis is used to investigate heat losses and distribution within kilns with the aim of improving energy efficiency in cement production. This study used Computational Fluid Dynamics (CFD) with Conjugate Heat Transfer, Turbulent Flow, and the Realisable k−ϵ turbulence model to simulate heat transfer within the refractory and wall systems of the kiln, evaluate the effectiveness of these systems in managing heat losses, and establish the relationship between the heat transfer coefficient (HTC) and the velocities of solid and gas phases. The simulation results indicate that a temperature gradient from the kiln’s interior to its exterior is highly dependent on the effectiveness of refractory lining in absorbing and reducing heat transfer to the outer walls. The results also confirm that different thermal profiles exist for clinker and fuel gases, with clinker temperatures consistently peaking at approximately 1450 °C, an essential condition for optimal cement-phase formation. The results also indicate that phase velocities significantly influence heat absorption and transfer. Lower velocities, such as 0.2 m/s, lead to increased heat absorption, but also elevate heat losses due to prolonged exposure. The relationship between the heat transfer coefficient (HTC) and the velocities of solid and gas phases also indicates that higher velocities improve HTC and enhance overall heat transfer efficiency, reducing energy demand.

Optimizing power grids: A valley-filling heuristic for energy-efficient electric vehicle charging.

The expansion of electric vehicles (EVs) challenges electricity grids by increasing charging demand, thereby making Demand-Side Management (DSM) strategies essential to maintaining balance between supply and demand. Among these strategies, the Valley-Filling approach has emerged as a promising method to optimize renewable energy utilization and alleviate grid stress. This study introduces a novel heuristic, Load Conservation Valley-Filling (LCVF), which builds on the Classical and Optimistic Valley-Filling approaches by incorporating dynamic load conservation principles, enabling better alignment of EV charging with grid capacity. We conducted a comprehensive analysis of the heuristic across five EV charging scenarios. In both the Original and Flexible scenarios, LCVF reduced energy demand by up to 10.65%, demonstrating its adaptability and effectiveness. Notably, in the 24-hour Availability scenario, LCVF achieved a reduction of over 20% in energy demand compared to CVF. These findings indicate that LCVF could play a crucial role in enhancing real-world EV charging infrastructure, boosting energy efficiency and grid stability. By integrating DSM strategies like LCVF, energy grids can better accommodate renewable energy sources, promoting more sustainable operations.

COMPOSITE HYDROPHOBIC PDMS-SILICALITE-1 MEMBRANES FOR THE SEPARATION OF THE ACETONEBUTANOL-ETHANOL (ABE) FROM AN AQUEOUS MIXTURE BY PERVAPORATION

One of the challenges in butanol production is its separation from aqueous acetone-butanol-ethanol (ABE) because of the azeotropic nature of the mixture and the high energy needed to recover the solvents from the dilute solution. Currently, pervaporation has been one of the most studied recovery approaches due to its selectivity when highly hydrophobic membranes are used, as well as the reduced energy demand involved in applying vacuum instead of conventional distillation. In this study, an ABE aqueous mixture was separated by pervaporation using pure and composite (mixed matrix and layered) PDMS + silicalite-1 membranes. For mixed matrix membranes, silicalite-1 crystals were dispersed in PDMS (20, 40, 60, and 80 wt%), then spin-coated using toluene as a solvent, and finally characterized by SEM-EDS, XRD, TGA, and FTIR. A total flux of 35.65 g/m2×h and a separation factor towards butanol of 22.60 was achieved with membranes prepared using 500 mg of (80 wt% + PDMS/mL of toluene) and 1,000 mg of silicalite-1 (80 wt% + PDMS/ mL of toluene), respectively. The high flux is related to the larger free volume in the polymer resulting from the incorporation of hydrophobic crystals of silicalite-1, thus improving the selectivity towards butanol. Also, the physicochemical properties of the membranes are paramount to high performance in the recovery of the ABE mixture, particularly the appropriate silicalite-1 loading.

Electrochemical Mineralization of Chloroquine in a Filter-Press-Type Flow Reactor in Batch Recirculation Mode Equipped with Two Boron-Doped Diamond Electrodes: Parametric Optimization, Total Operating Cost, Phytotoxicity Test, and Life Cycle Assessment

This study investigated the electro-mineralization of chloroquine (CQ) in a filter-press-type flow reactor using two BDD electrodes operating in batch recirculation mode. The optimal operating parameters were established using response surface methodology (RSM) and central composite rotatable design (CCRD) with three parameters: current density (j), initial pH (pH0), and volumetric flow rate (Q), with the mineralization efficiency of (CQ) and specific energy consumption (SEC) as responses. Optimal operating parameters were j = 155.0 mA/cm2, pH0 = 9.75, and Q = 0.84 L/min within a reaction time of 9 h, leading to a maximum mineralization efficiency of CQ of 52.59% and a specific energy consumption of 15.73 kW/mg TOC, with a total operating cost of USD 0.18 per liter. Additionally, an ultra-high-performance chromatography study identified three by-products (4-amino-7-choloroquinoline, formic acid, and acid acetic) of CQ degradation. Furthermore, the phytotoxicity test indicates that the electrochemical wastewater proposed decreased the effluent’s phytotoxicity, and an increase in the percentage of Vigna radiata germination was observed. The carbon footprint of optimized electrochemical mineralization of chloroquine is 2.48 kg CO2 eq., representing a 48% reduction in cumulative energy demand (CED) when the source of energy is a mixture of fossil fuels (50%), wind (25%), and photovoltaic (25%) energy.

Design and Implementation of Sustainable Transportation- Electrical Velomobile

Velomobiles exemplify a cutting-edge solution for sustainable transportation, merging design, efficiency, and eco-friendliness. These human-powered vehicles combine the benefits of bicycles with a streamlined, enclosed structure, offering a practical alternative to traditional transport. Constructed from lightweight materials like carbon fiber, velomobiles prioritize aerodynamics, comfort, and functionality. Their enclosed design shields riders from weather, making them suitable for year-round use, while their three-wheel stability and ergonomic seating enhance comfort and ease of handling. The aerodynamic structure reduces energy demands, ensuring efficiency even in stop-and-go urban traffic. Beyond comfort and design, velomobiles contribute significantly to sustainability. They offer a zero-emission alternative to cars, reduce urban congestion, and promote physical fitness. With storage compartments for convenience, they address common limitations of bicycles. By making cycling safer and more appealing, velomobiles encourage a shift toward greener commuting, helping cities tackle pollution and climate challenges effectively.

Ranking the Barriers to the Energy Upgrading of Buildings Using the Best-Worst Method

The global need to reduce energy demand has led European governments to accelerate their endeavors to achieve their targets regarding nearly zero-energy buildings. Despite the implementation of funding initiatives for the energy upgrading of buildings in EU member states and other European countries, research has shown that the absorption rates of the offered funds remain low. This research aims to assess the significance of the barriers to improving the energy efficiency of Greece’s building stock. This is achieved by ranking the identified barriers using the best-worst method (BWM). The innovation provided by this study is that the data obtained are based on the experience of three categories of stakeholders, including professionals in the field, i.e., engineers and skilled workers, and homeowners. The results show that all three groups are discouraged from performing the energy upgrading of buildings due to economic barriers but also technological barriers related to a lack of training in the use of and slow development of related new technologies.

Energetic Analysis of Passive Solar Strategies for Residential Buildings with Extreme Summer Conditions

This study investigates the implementation of passive design strategies to improve the thermal environment in the extremely hot climates of Brazil, Portugal, and Turkey. Given the rising cooling demands due to climate change, optimizing energy efficiency in buildings is essential. Using the Trace 3D Plus v6.00.106 software, typical residential buildings for each country were simulated to assess various passive solutions, such as building orientation, wall and roof modifications, glazing optimization options, window-to-wall ratio (WTWR) reduction, shading, and natural ventilation. The findings highlight that Brazil experienced the higher discomfort temperatures compared to Mediterranean climates, with indoor air temperatures exceeding 28 ºC all year round and remaining between 34 ºC and 37 ºC for nearly 40% of the time. Building orientation had a minimal impact near the equator, while Mediterranean climates benefited from an up to 10% variation in energy demand. Thermal insulation combined with white exterior paint resulted in Şanlıurfa experiencing annual energy savings of up to 26%. Optimal roof solutions yielded a 19% demand reduction in Évora, while WTWR reduction and double-colored glazing achieved up to a 35% reduction in Évora and 19% in other regions. Combined strategies achieved energy demand reductions of 44% for Évora, 40% for Şanlıurfa, and 32% for Teresina. The study emphasizes the need for integrated, climate-specific passive solutions, showing their potential to enhance both energy efficiency and the thermal environment in residential buildings across diverse hot climates.

Future technologies for building sector to accelerate energy transition

This Editorial briefly introduces and organizes the worthy studies provided in the Special Issue of Energy and Buildings, entitled “Future technologies for building sector to accelerate energy transition: a special issue”. The main topics of selected papers are herein summarized, proposing scientific studies concerning the next generation buildings, and thus mandatory targets of energy efficiency, reduction of energy demands, novel technologies for building envelope and active energy systems, on-site conversion from renewable energy sources. Both areas of the building industry are considered, and thus decarbonization of existing buildings and novel constructions characterized by mandatory energy performance levels of nearly, net- and plus-energy buildings. These topics are crucial for improving building performance, and reducing energy consumption, with reference to both the heating and cooling seasons, therefore addressing the new and mandatory challenges of zero-energy and zero-emission buildings, also taking into account climate change. The results of manuscripts published in this special issue show worthy potential and real achievements, with significant reductions in energy demands and emissions, and therefore they underline the usefulness of traditional and novel technologies and strategies for buildings, highlighting the economic and environmental benefits of novel design and retrofitting methods and solutions. The debated topics are essential to dealing with climate change, reducing energy poverty, environmental impact, local overheating and UHIs, going, finally, in the direction of a mandatory, sustainable, and smart future for the building sector.

The role of advanced energy management strategies to operate flexibility sources in Renewable Energy Communities

Renewable Energy Communities (REC) can largely contribute to building decarbonization targets and provide flexibility through the adoption of advanced control strategies of the energy systems. This work investigates how the role of flexibility sources will be impacted by shifting towards advanced control strategies under a high penetration of variable Renewable Energy Sources, in the following years. A large residential area with diverse energy systems, building envelope configurations, and energy demand patterns is modeled with the simulation environment RECsim, a virtual testbed for the implementation of energy management strategies in REC. Photovoltaic (PV) panels, Battery Energy Storage and Thermal Energy Storage (TES) of different sizes for each household provide a realistic description of a REC which includes both consumers and prosumers.This study explores a scenario in which advanced controllers based on Deep Reinforcement Learning (DRL) replace existing Rule-Based Controllers in building energy systems across a significant number of buildings. These control policies are simulated under three different scenarios that consider consumers with different pricing schemes and TES penetration.Efficient control strategies, have demonstrated significant potential, regardless of the presence of thermal storage and ToU pricing schemes, in reducing energy demand by 12.6%, cutting energy costs by 20.8%, and enhancing self-sufficiency and self-consumption, with minimal impact on Shared Energy. Implementing a flat tariff scheme under DRL enables consumers to increase their energy demand during periods of PV generation, which is particularly advantageous in a REC. Also, this approach lowers overall energy demand by 12.6% and boosts self-sufficiency, and it also decreases electricity exports from the REC to the grid by 18.2% compared to a ToU tariff scheme. When using ToU tariffs, thermal storage can be used to achieve cost savings, but total Shared Energy decreases, as do self-sufficiency and self-consumption of the REC. The results indicate that in a REC with high variable renewable energy and decentralized control, consumers using TES and ToU tariffs with peak prices during high irradiance periods may not be beneficial for the grid compliance.In conclusion, the coupling between DRL and thermal storage should be supported by more innovative pricing schemes for RECs and/or coordinated energy management, although it requires advanced communication and monitoring infrastructure.

Buildings in Hot Climate Zones—Quantification of Energy and CO2 Reduction Potential for Different Architecture and Building Services Measures

Reducing energy and associated greenhouse gas emissions in buildings is one of the key aspects of climate change on a global level. To put the building sector on a low carbon development path, policies and adequate financing play a crucial role in each region. In the global South, policies and regulations related to the decarbonization of the building stock are increasingly being implemented. For policy and decision makers, adequate data on the status quo of the building stock, as well as the quantification of energy reduction measures, are essential to make informed decisions on the building regulatory and funding framework. The objective of this study is to provide data-driven insights into the potential for energy and CO2 reduction in buildings across various hot climate zones in the Global South. A simulation-based approach was employed to model five different building types, ranging from residential homes to office buildings, under a variety of architectural and building services scenarios. The simulations were conducted using the dynamic building energy simulation tool EnergyPlus, which assessed the impact of various energy-saving measures under both current and projected future climate conditions. This study concludes that optimizing passive design features, such as improved windows, solar shading, and reflective surfaces, in conjunction with active systems like decentralized cooling units and renewable energy integration, can result in a notable reduction in energy demand and emissions. Our findings provide a robust basis for policymakers to develop targeted energy efficiency strategies for buildings in hot climate zones, which will play a crucial role in achieving climate goals in the Global South.

A dynamic modelling approach to explore zero emission building stock opportunities towards 2050 – Case study of a university campus

The building sector has a significant influence on energy use and environmental impact. When observing a university campus, reduction of energy use is a complex issue due to the variety of building types, usage, building construction age, and different implementation of improvement measures. To investigate how energy efficiency measures on a single building may influence the entire campus, a combination of building energy simulation and a scenario-based aggregation method using dynamic material flow analysis principles was implemented. This study investigated possible energy efficiency measures at a university campus in Trondheim, Norway. Scenario analysis was used to identify the most critical factors for future development and to evaluate to what extent the campus might develop towards a net zero-emission campus during the period 2017–2050. Four scenarios were introduced including two aspects: renovation of the existing building stock and changes in campus energy supply systems. The results on energy efficiency packages highlighted that saving potentials were highly dependent on the construction period of the buildings. The package combining envelope renovation and operation improvements showed the highest savings. The findings indicated that advanced renovation, including extensive use of heat pumps, might be the most promising strategy for reducing energy demand by 26 %.

Hybrid model-based predictive HVAC control through fast prediction of transient indoor temperature fields

Efforts to reduce energy demand in the building sector have prompted a focus on the operational control of HVAC systems. Despite extensive research on HVAC control based on temperature prediction models, existing approaches often rely on node-based or average temperature predictions, which lack the detailed temperature distribution data necessary for accurate control, especially in transient situations with both spatial and temporal variations. This study introduces a precise HVAC control method based on a fast temperature field prediction model. By combining the single-step prediction response coefficient (SPRC) method with Convolutional Neural Network (CNN) architecture, sub-temperature field prediction models for multiple independent heat sources were constructed and integrated to achieve fast temperature field predictions. Subsequently, utilizing the predicted temperature field, air conditioning operation parameters were optimized and controlled to minimize energy consumption. Application of the proposed method in real building scenarios demonstrated the temperature field predictions closely aligned with computational fluid dynamics (CFD) simulations, achieving a mean absolute error (MAE) of 0.27 °C and a root mean square error (RMSE) of 0.24 °C. Furthermore, this model achieved a notable 57.8 % improvement in prediction accuracy compared to models relying solely on single-step prediction responses. Additionally, the model predictive control based on the hybrid model's temperature field predictions significantly reduced the runtime of the HVAC system by 18.18 % while maintaining temperatures within the comfort range throughout the operation period. The method presents a promising avenue for optimizing HVAC operations and minimizing energy consumption in building environments, thereby contributing to sustainable building management practices.

Incorporating PCMs and thermal insulation into building walls and their competition in building energy consumption reduction

To diminish the 30 % share of buildings in final energy consumption, in this study, phase change material (PCM) and insulation are incorporated into the walls of the building. The primary goal is to determine whether insulation or PCM is more effective in reducing heat exchange through walls. Defining the parameters of the indoor setpoint (7 cases), the type of material (9 cases of PCM and one thermal insulation), the thickness of PCM or insulation (2 cases), and their location (3 cases: L1, L2, and L3), energy consumption (output parameter) was investigated in 420 cases. Because the geographic location of the building has a significant effect on energy consumption, in four different climate regions (ASHRAE index: 3B, 2B, 4B, and 4B), the competition between PCM and insulation in reducing energy consumption was investigated running 1680 cases. In the first climate zone, a layer of PCMs (3 cm thickness) with a melting range of 22–25 °C must installed at the L2 location to achieve the 61.8 % reduction in annual energy demand. If the thickness reaches 6 cm, the optimal material (PCM) should be installed at L3. If the indoor temperature is set higher than 27 °C, insulation should be installed instead of PCM. In the second and third zones, in all cases, it is better to install insulation than PCM. In the fourth zone, at a thickness of 3 cm, PCM can compete with insulation, but at a thickness of 6 cm, insulation is almost a better option. Numerical results affirm that in 71.4 % of cases, thermal insulation is superior to PCM. Genarally it is not recommended to install insulation/PCM in layers close to the building interior.

Development and characterisation of novel compressed earth bricks bio-sourced with raw and treated alpha fibres

In this research, the effect of using alpha fibres on the physico-mechanical properties of compressed earth bricks (CEBs) was investigated. CEBs were produced using soil, lime and different amounts (0%, 0.5%, 1%, 1.5% and 2%) of raw (RAF) or treated alpha fibres (TAF). First, the diameter, density and water absorption of RAF and TAF were determined. Then, the produced CEBs reinforced by these fibres were subjected to compressive strength, thermal test, density and capillarity water absorption tests. The obtained results showed that the addition of RAF and TAF leads to a reduction of the thermal conductivity by 33% and 31%, respectively. The finding also indicated that the density was decreased by 26% and 17% with the inclusion of TAF and RAF respectively. Besides, the compressive strength was reduced and water absorption coefficient was increased when fibres reinforced CEBs but remaining within the standard’s recommended limits. Moreover, the addition of fibre improves the acoustic properties of samples by 98%. The CEBs developed in this paper could be an alternative to other more common building materials, which would lead to a reduction of energy demand and environmental problems.

Design and Development of Integrated Direct Air Capture and Methanation Processes

AbstractThe synergies from integrating direct air capture and CO2 methanation are assessed and quantified. Three direct air capture and methanation processes with different integration strategies are proposed: only heat integration, direct air capture sorbent regeneration with high‐pressure H2, and complete integration in a single unit. The heat integration study via pinch analysis evaluated the potential energy demand reduction. Overall autothermal operation is achievable, as the heat generated in methanation often exceeds that required for direct air capture sorbent regeneration. A novel process combining CO2 adsorption and methanation in one reactor provided the best productivity and energy demand results. However, this design requires complex cycles and strict demands on the sorbent and catalyst, requiring further development and experimental demonstration.

A data-driven framework for occupancy optimisation strategies towards energy demand reduction in non-domestic buildings

Proactive strategies for data-driven operational schedules based on monitored occupancy patters can enable energy demand reduction and optimal resource utilisation. A replicable framework that enables strategic closure of specific thermal zones is introduced and design and operational considerations are discussed. The potential of the framework is illustrated through a case study building, where up to 6% annual energy savings were estimated, highlighting the effectiveness of zone closures. Further findings indicated that total energy savings from the simultaneous closure of multiple zones were marginally larger compared to savings from closing off zones individually, depending on zone capacity and use. Therefore, balanced considerations should take place prior to selecting which zones to close off, also taking into account user acceptability, capacity of systems and controls as well as the internal layout of the building. The research enhances the understanding of the relationship between occupancy and energy demand, while offering recommendations for more energy efficient and sustainable building design and operations that require minimal capital cost. Practical Application This paper provides design and operational considerations based on a robust and replicable framework for energy savings by optimising operational building schedules based on monitored occupancy patterns. This allows a proactive implementation of data-driven strategies that maximise resource utilisation, such as closure of specific zones during periods of low occupancy, without requiring any physical intervention. The findings on a case study building demonstrate that annual energy savings can be achieved, underscoring the potential for substantial cost reductions and improved energy efficiency. Applications can also extend to optimising energy demand for energy flexibility.

The key role of sufficiency for low demand-based carbon neutrality and energy security across Europe

A detailed assessment of a low energy demand, 1.5 ∘C compatible pathway is provided for Europe from a bottom-up, country scale modelling perspective. The level of detail enables a clear representation of the potential of sufficiency measures. Results show that by 2050, 50% final energy demand reduction compared to 2019 is possible in Europe, with at least 40% of it attributable to various sufficiency measures across all sectors. This reduction enables a 77% renewable energy share in 2040 and 100% in 2050, with very limited need for imports from outside of Europe and no carbon sequestration technologies. Sufficiency enables increased fairness between countries through the convergence towards a more equitable share of energy service levels. Here we show, that without sufficiency measures, Europe misses the opportunity to transform energy demand leaving considerable pressure on supply side changes combined with unproven carbon removal technologies.

Cradle-to-gate analyses of biochar produced from agricultural crop residues by vacuum pyrolysis

Abstract Agricultural waste, if not managed efficiently, can pose significant environmental threats. Biochar production, a cost-effective solution, offers a potential to significantly reduce carbon dioxide emissions and thereby combat climate change. However, the environmental impact of this process is not uniform and varies depending on the agricultural residue used. These impacts, spanning the entire lifecycle from cultivation to disposal, underscore the necessity of a thorough assessment before biochar can be widely adopted for practical applications. This study employs a cradle-to-gate approach to evaluate the life cycle assessment (LCAs) of producing biochar from various agro-residues, such as rice husk, sugarcane bagasse (SB), and corn cob (CC). The LCA was conducted using SimaPro software, version 9.5.0.1, and the ReCiPe impact assessment method. The results indicate that CC cultivation has the highest impact across most categories, while rice husks exhibit higher water consumption (2.8 × 103 m3). Using diesel, electricity, and fertilizers significantly contributes to global warming potential (GWP). SB shows the most negligible impact during biomass cultivation. However, pyrolysis processes exhibit high implications on various indicators. Applying biochar to soil for carbon sequestration and improvement can reduce GWP. Sensitivity analysis demonstrates a notable reduction in GWP and cumulative energy demand, approximately 10%–24% and 4–11 MWh, respectively. Paddy cultivation and rice husk biochar production have a lesser environmental impact. Changing energy sources during biomass growth and biochar production significantly influences environmental factors.

Blacklight sintering of BaZrO3-based proton conductors

Acceptor-doped BaZrO3, a ceramic proton conductor, is well researched for use in solid oxide fuel cells due to its proton conductivity and chemical stability. A major drawback of the material is the difficulty of sintering as it requires high sintering temperatures and long heating times (> 1600 °C, 24 h). An emerging sintering technology to mitigate this challenge is blacklight sintering, which uses a high-powered blue or UV light source to heat ceramics extremely fast leading to short sintering times and reduced energy demand. In this work, BaZr0.8Y0.2O3-δ (BZY20) and BaZr0.8Y0.1Sc0.1O3-δ (BZY10Sc10) were blacklight-sintered with a high-power blue laser in under four minutes. Even though the resulting samples have a gradient from large to small grains and structurally disordered grain boundaries, the proton conductivity is comparable to conventionally sintered samples. Hence, blacklight sintering is a promising technology with the potential to sinter BaZrO3 much faster, while saving energy.

Achieving deep transport energy demand reductions in the United Kingdom

The transport sector is a crucial yet challenging area to decarbonize, given its heavy reliance on fossil fuel usage, carbon-intensive infrastructure and car-centric lifestyles. It remains the largest contributor to local air pollution in cities yet has the potential to improve people's physical and mental health. This research investigated the potential contribution of transport energy demand reduction to climate change mitigation and improving public health. Using a comprehensive bottom-up modelling framework, the Transport Energy and Air pollution Model (TEAM), this study provides an integrated assessment of the impacts of deep mobility-related energy demand reductions, including lifecycle carbon emissions, local air pollution and health impacts. Using a sociotechnical scenario approach and the UK as a case study, this research reveals that energy demand reductions of up to 61 % by 2050 compared to baseline levels are achievable and can enhance citizens' quality of life. Business as usual approaches which rely on a technical transition miss the legislated carbon budgets and result in higher energy demand in 2050. More comprehensive scenarios deliver a reduction of up to 72 % in total lifecycle carbon emissions by 2050, with approximately half of the reduction achieved through mode shifting and avoiding travel, while the other half comes from vehicle energy efficiency, electrification, and downsizing of the vehicle fleets. The research shows that it can lead to significant co-benefits such as improved local air pollution and public health. The feasibility and practicality of policy measures and integrated strategies identified for achieving deep transport-energy demand reductions are discussed.