Realize Energy Savings Research Articles

Energy-Management Method to Reduce the Capacity of Lithium-Ion Batteries in Hybrid-Voltage-Source Three-Level Inverter for DC-Electrified Railway Vehicles

The hybrid-voltage-source three-level inverter is a traction circuit system aimed at realizing energy savings with lithium-ion batteries for direct-current-electrified railway vehicles. However, this system has the limitation of being unable to freely control the power flow of the batteries owing to the pulse width modulation. However, because this system has batteries, energy management is required for the batteries. Therefore, it is necessary to propose an energy-management method that achieves the required energy-saving effect while considering the constraints of the battery power control. In this paper, a management method is proposed to control the power flow of the batteries by determining the pulse mode of the inverter and the modulation wave offset based on the state of the charge and inverter frequency. In a 0.75-kW class mini-model verification, the effectiveness of the proposed energy-management method is then confirmed based on the state of the charge, inverter frequency, offset, and battery power. Subsequently, we evaluate the energy-saving effect of this hybrid system using a numerical simulation while considering an actual railway vehicle. In addition, the optimal capacity of the batteries is investigated. As a result, the best energy-saving effect is obtained when two of the assumed batteries are connected in series and three in parallel, and the power consumption is reduced by approximately 21%.

Climate policy without a price signal: Evidence on the implicit carbon price of energy efficiency in buildings

Based on data for a portfolio of 548 multi-unit buildings observed over 16 years, we quantify the impacts of more than 400 energy efficiency interventions among 239 treated buildings. We exploit variation in the timing of investments to provide evidence that treated and control buildings follow the same trend in the absence of energy efficiency investments, and use staggered difference-in-differences regressions to document building-level energy savings, CO2 abatement, and heating expenditure reductions. Our results show that a ranking of interventions based on realized energy savings yields substantially different priorities as compared to a ranking of implicit carbon prices, with estimates of frequently subsidized measures (such as wall insulation and windows replacement) well in excess of available benefit estimates for avoided emissions.

Beyond Good Faith: Why Evidence-Based Policy is Necessary to Decarbonize Buildings Cost-Effectively

The ambitious climate targets set by industrialized nations worldwide cannot be met without decarbonizing the building and heating sectors. Using Germany as a case study, this paper takes stock of the extensive set of energy-efficiency policies that are already in place and clarifies that they have been designed “in good faith” but lack in overall effectiveness as well as cost-efficiency in achieving these climate targets. We map out the market failures and behavioural considerations that are potential reasons for why realized energy savings fall below expectations and why the household adoption of energy-efficient and low-carbon technologies has remained low. We highlight the pressing need for empirical research to assess the efficacy of existing energy-efficiency programs and apply modern statistical methods to develop targeted and cost-effective policies. To this end, we identify some key research questions and identify gaps in the data required for evidence-based policy.

Retrofit effectiveness: Evidence from a nationwide residential energy efficiency programme

Buildings in the EU are responsible for 40% of energy use, with approximately 75% of buildings classed as energy inefficient. Many energy efficiency technologies have failed to deliver on the promised savings. This paper measures the extent to which residential dwelling retrofit delivers real energy savings in Ireland using a unique dataset of whole-home energy use (n = 8,572 households) over a two-year period. It is one of the largest studies of retrofit using whole-home energy data for a general housing sample, who do not disproportionately experience fuel poverty. It uses whole-home energy data to capture potential fuel switching induced by retrofit. Finally, this study addresses concerns regarding self-selection issues associated with the decision to undergo a retrofit by comparing with a second control group of homes that received a retrofit prior to the observation period.Results following a generalised difference-in-difference methodology indicate that retrofits reduce energy use by 1,091 kWh/year, on average. However, the magnitude of savings depends on the measures installed. Further analysis suggests that retrofits represent better value for money when factoring in actual changes in energy use. This study highlights possible unintended consequences of retrofit policies that may hinder progress towards national energy efficiency targets.

Energy performance analytics and behavior prediction during unforeseen circumstances of retrofitted buildings in the arid climate

During the COVID-19 pandemic, the energy consumption profile has been changed in several facilities as a response to the lockdown and other precautionary measures. Lockdown has reduced the electrical load consumption in commercial buildings. Accordingly, the energy cost savings have been reflected in the energy bills. However, such savings were not due to improvement of energy performance and equipment efficiency, but because of changes that occurred in the operating conditions and parameters. As a result, it was complicated to identify the real energy savings in the energy retrofit projects during this period. For the energy conservation and refurbishment projects, a challenge was faced to calculate an accurate energy savings amount and to track the energy pattern and performance during these lockdown months.This study discusses the energy behavior of retrofitted buildings that follows the energy performance contracting. It shows the improvement of energy consumption for one year for 30 studied buildings. It discusses the strategy to follow in the calculation of the energy savings during a full lockdown period. This article addresses the approach to be taken into consideration and its consequences to monitor the energy profile as per the International Performance Measurement and Verification Protocol.

Efficiency of ventilated facades in terms of airflow in the air gap

Abstract The gradual exploitation of the natural environment has forced most developed countries to promote ecological solutions and the development of sustainable construction. Ventilated facades perfectly match into this trend, and with their appropriate design, they bring real energy savings. This paper analyzes numerically the influence of the inflowing air, mimicking the wind, on the efficiency of heat removal from the ventilated space and heat transmission by thermal radiation and conduction through the consecutive layers of the external wall. For the purpose of comparison, two variants of ventilated facade were adopted: open and closed joints, at different wind speeds prevailing outside. The results obtained show that in windless weather, the ventilated facade with open joints shows higher heat removal efficiency and thus lower heat transmission to the building interior. At higher wind speeds of 5 m/s, the open-joint and closed-joint ventilated facades achieve similar heat transfer efficiency, and the prevailing temperature inside the building for the two technologies is almost identical. Subsequent increments of incoming wind on the building result in minimal differences in the heat transmission to the building interior, representing changes of about 0.1°C at increments of another 5 m/s of incoming wind. Conscious use of this facade technology, along with appropriate urban design of cities, can help reduce the energy needed to cool buildings during the summer period.

A zone-level occupancy counting system for commercial office spaces using low-resolution time-of-flight sensors

Understanding the locations of occupants in a commercial built environment is critical for realizing energy savings by delivering lighting, heating, and cooling only where it is needed. In this paper, we present an indoor occupancy counting system using a sparse array of inexpensive, low-resolution, and privacy-preserving time-of-flight sensors. We develop and validate an algorithm for zonal occupancy counting that can deal with multiple people walking underneath the sensors in arbitrary directions, and evaluate the system both in realistic simulations of office spaces and in a real-world installation. We found that our system has an error rate of around 0.4%, resulting in highly accurate person localization and zone counting using only a few sensors per space.

A Review of Behavioral Energy Reduction Programs and Implementation of a Pilot Peer-to-Peer Led Behavioral Energy Reduction Program for a Low-Income Neighborhood

Utility-sponsored residential energy reduction programs have seen rapid advancement in the Unites States (US) over the past decade. These programs have particularly emphasized investments in energy efficient appliances and enveloped improvements. They have generally required co-investment by residents and, as a result, have mostly reached medium to high-income residents, with low income residences, in effect, supporting the utility investments through higher energy costs. Additionally, utility initiatives directed toward behavior-based energy reduction have reached residences with more advanced technologies, such as smart meters and smart Wi-Fi thermostats linked to phone apps, technologies generally not present in low-income residences. This research seeks to inform development of behavior-based energy reduction programs aimed specifically at low-income residences, premised on peer-to-peer energy education and support. It focuses on the design and implementation of a pilot program for 84 low-income residences in a medium-sized Midwestern US urban neighborhood, followed by measurement of realized energy savings and assessment of program outcomes through surveys of resident participants and interviews with program implementers. Only 21 residences provided an initial response to outreach. Of these, only 11 participated, and of these, energy savings were, in general, modest. However, evidence based upon other research and qualitative data obtained from program implementers and participants is presented in this study for the development of an improved design. The improved design emphasizes grassroots community co-design of the program and community engagement through program implementation to transform energy consumption and behaviors and find energy justice for vulnerable communities.

Mind the Energy Performance Gap: testing the accuracy of building Energy Performance Certificates in Ireland

Ireland’s Climate Action Plan aims upgrade 500,000 homes to B2 Energy Performance Certificate (EPC) standard by 2030. Evidence of an Energy Performance Gap, where actual energy use differs from the EPC, could undermine progress towards such targets. This paper studies the energy performance gap for a general housing sample (n = 9923) over multiple years. It provides a novel comparison between whole-home energy use (electricity and gas) that accounts for fuel switching and removes potential rebound effects by excluding households that may have changed their behaviour following a retrofit. Results suggest that actual energy use is unresponsive to the EPC, with a range of 457 kWh/year observed across EPC-level averages for the entire sample. This difference equated to less than 5% of the sample average annual energy use observed. The Energy Performance Gap range features an average deficit of 17% below theoretical energy use. The least energy efficient dwellings feature an average difference ranging from − 15 to − 56% of the relevant EPC. Conversely, energy efficient houses display higher-than-theoretical energy use, with average surpluses ranging from 39 to 54% of the relevant EPC. Results sound a note of caution for policymakers that rely on a theoretical EPC to deliver real energy savings. Future EPCs could be improved by incorporating historical household energy usage to help improve models.

Energy Optimization for Adjustable-Speed Drive Applications: Increasing Efficiency to Cut Costs and Preserve Assets

Whether you believe there is a connection between carbon dioxide and global warming or not, reducing energy consumption by improving operating efficiency has the benefit of preserving natural resources, reducing production costs, and postponing investment in infrastructure, such as generating stations and transmission lines. Induction motors are a logical target since they are the primary machines in use and account for the vast majority of industrial loads. Loads driven by induction motors consume more than half the electrical energy generated. A small improvement in efficiency has a pronounced effect on overall energy consumption. When a process has a range of operating points, adjustable-speed drives (ASDs) are often employed to realize energy savings based on affinity laws. While this saves substantial energy, it can be further optimized with flux vector control and other techniques. This article examines the topic of optimal energy control, which results in additional energy savings.

Experimental Study of a New Pneumatic Actuating System Using Exhaust Recycling

Pneumatic actuating systems are an important power system in industrial applications. Due to exhaust loss, however, pneumatic actuating systems have suffered from a low utilization of compressed air. To recycle the exhaust energy, a novel pneumatic circuit was proposed to realize energy savings through recycling exhaust energy. The circuit consisted of three two-position three-way switch valves, which were used to control the exhaust flows into a gas tank or the ambient environment. This paper introduced the energy recovery configuration and working principles and built a mathematical model of its working process. Then, the mathematical model was verified by experiments. Finally, through experiments in which the air supply pressure, the critical pressure and the volume of the gas tank were regulated, the energy recovery characteristics of the pneumatic actuating system were obtained. Using the new circuit, the experimental results showed that the energy recovery efficiency exceeded 23%. When the air supply pressure was set to 5 bar, 6 bar, and 7 bar, the time required for pneumatic actuation to complete the three working cycles were 5.2 s, 5.3 s, and 5.9 s, respectively. When the critical pressure was set to 0 bar, 0.5 bar, 1 bar, and 1.5 bar, the times for pneumatic actuation to complete the three working cycles were 4.9 s, 5.1 s, 5.2 s, and 5.3 s, respectively. When the volume of the gas tank was set to 2 L, 3 L, 4 L, and 5 L, the number of working cycles was 3, 4, 5, and 6, respectively. This paper provides a new method of cylinder exhaust recycling and lays a good foundation for pneumatic energy savings.

Appliance-specific feedback and social comparisons: Evidence from a field experiment on energy conservation

The provision of feedback about individual electricity consumption is a widely used approach to promote pro-environmental behavior. This form of feedback typically invokes social comparisons by informing households about their aggregate electricity consumption relative to others. While previous research has shown that aggregate consumption feedback translates into significant energy savings, the potential for further reductions may remain untapped because households lack knowledge about their appliance energy consumption patterns. In this paper, we present evidence from a field experiment, where we provide residents with feedback about their electricity consumption, specific to a high-energy use appliance (i.e. air-conditioner). We provide the relevant social norm information by varying the reference group of each resident. We find that our appliance-specific feedback is a powerful tool to curb electricity consumption. Residents significantly reduce their average air-conditioning usage by 17% in our treatment groups. Notwithstanding, our effects are not driven by comparative feedback with respect to different reference groups. We interpret this as encouraging evidence to promote the use of appliance-specific feedback to realize energy savings.

Design of VO2-based photoactuators for smart windows

Smart windows can slow down the heating rate in buildings to a certain extent and realize energy savings and emission reduction. Various approaches have attempted to make windows ‘smart’ by tailoring their thermal insulation behavior in response to environmental changes. However, there is still room for further improvement in their efficiency and automation performance. Here, based on photothermal functional fillers and shape memory substrates, a new type of photoactuator for smart windows—passively controlled shuttering—was designed. The photoactuator was composed of VO2@SiO2 and methyl methacrylate butyl acrylate polymer (MBP). These two functional components had similar transition temperature (30 °C), and the photothermal conversion of VO2@SiO2 stimulated the shape memory behavior of the composite. It was demonstrated that the intelligent performance was closely related to the shape memory properties of MBP and the phase transition characteristics of VO2 NPs, which synergistically modified the solar regulation ability. The results suggest that this new type of optical driving window has potential applications in the field of wearable sensors, energy conservation and medical devices.

Smart Wifi Thermostat-Enabled Thermal Comfort Control in Residences

The present research leverages prior works to automatically estimate wall and ceiling R-values using a combination of a smart WiFi thermostat, building geometry, and historical energy consumption data to improve the calculation of the mean radiant temperature (MRT), which is integral to the determination of thermal comfort in buildings. To assess the potential of this approach for realizing energy savings in any residence, machine learning predictive models of indoor temperature and humidity, based upon a nonlinear autoregressive exogenous model (NARX), were developed. The developed models were used to calculate the temperature and humidity set-points needed to achieve minimum thermal comfort at all times. The initial results showed cooling energy savings in excess of 83% and 95%, respectively, for high- and low-efficiency residences. The significance of this research is that thermal comfort control can be employed to realize significant heating, ventilation, and air conditioning (HVAC) savings using readily available data and systems.

Influence of Phase Change Phenomena on the Performance of a Desiccant Dehumidification System

Demands of standalone dehumidification systems have been increasing in order to realize energy savings in air-conditioning processes. In a desiccant dehumidification system, the water vapor from the moist air undergoes a phase change phenomenon, this being from vapor to adsorbed phase, a process analogous to latent heat exchange. The energy exchange involved in such a process is often significant—up to 80% of the total energy exchange. In this study, the influence of the phase change phenomena involved in a desiccant dehumidification system was evaluated experimentally, along with the performance investigation under low desorption air temperatures of 308, 318, 328, 338, and 345 K. The system was driven by a constant adsorption temperature of 293 K. The dehumidification ability, latent heat ratio, and latent effectiveness were employed as key performance indexes. The results showed that with the increased desorption temperature, the latent heat ratio decreased, whereas the dehumidification ability and latent effectiveness increased. The highest latent heat ratio was found to be 0.61 at the desorption temperature of 308 K, whereas the highest latent effectiveness was obtained at the desorption temperature of 345 K. A suitable temperature for the effective and efficient dehumidification was observed to be 318 K for the current system.

Experimental evaluation of calculated energy savings in schools

A lot of studies focus on IAQ in classrooms and energy retrofit of schools in order to increase the pupils’ performance and reduce energy consumption. However, there are limited number of studies that compare the calculated (as part of energy audits) and actual energy savings, discussing such a difference in order to give the recommendation for the future renovation projects. Long-term field data were collected over eight heating seasons from four schools organized into two groups characterized by different range of modernization activities. The group A includes two schools where besides the thermal modernization of building envelopes, the central heating installation was modernized and hydraulic balanced. The group B also comprises two schools where only the thermal retrofit of building envelopes took place, but the heating installation was not modernized, nor hydraulic balanced. The calculated level of energy saving was not covered in 18.1% and 20.3% in the case of schools from group A and in 47.2% and 41.1% in the case of schools from group B, respectively. The results may be of interest for the investors, engineers and policy makers who intend to minimize the difference between the planned and real energy savings as well as the payback time of modernization activities.

Energy optimization of pneumatic actuating systems using expansion energy and exhaust recycling

As an important power source in industrial applications, compressed air makes up an increasingly large proportion of total industrial energy consumption. Due to the compression and leakage of air, however, pneumatic actuating systems have suffered from a low utilization of compressed air. Moreover, for a traditional pneumatic circuit, a three-position five-way valve is used to control the air inlet and exhaust with a single pressure, also causing low efficiency. This study proposes a novel bridge circuit to realize energy savings through utilizing compressed air expansion energy and exhaust energy. The circuit consisted of five two-position two-way switch valves. The open-and-close sequence of these valves was used to control the motions of a cylinder piston. This circuit could realize system energy conservation by less air intake and waste air reuse, while simultaneously ensuring that the piston reached the end of its stroke with stability. In order to optimize air consumption, a nonlinear dynamic system optimization model was built based on the idea of dynamic optimization, and the pressure and flow of the pneumatic system and the dynamic equation were considered as constraint conditions. Optimization of the open-and-close sequence of the five switch valves in the bridge circuit was conducted using orthogonal collocation on finite elements and the interior point method. Lastly, a bridge actuator test platform was built to test the stability and energy efficiency of the proposed pneumatic circuit based on the open-and-close sequence obtained through the optimization algorithm with different air supply pressures and workloads. Compared with the traditional circuit, the proposed circuit yielded energy savings of 55–87%, and the impact acceleration at the end point is smaller than that at the end point, with only −0.01–0.02 m/s. These results suggested that the circuit is important for enhancing the utilization of compressed air.

Comparison of theoretical heat transfer model with results from experimental monitoring installed in a refurbishment with ventilated facade

One of the main points to consider when a building is renovated is the improvement of its energy efficiency, minimizing the heat loss through the enclosures and its heating consumption. Under this scope idea a ventilated facade was designed and incorporated in an educational building located in the city of Burgos (Spain). The main objective of this document is a comparison between the theoretical model of heat transfer across the building envelope separating the environment and the interior space, and the heat intake through a linear regression model with installed experimental monitoring. For this it has been necessary to carry out an exhaustive study of the thermal transmission of each one of the materials that make up the thermal envelope of the building, as well as the linear thermal bridges that can be produced before and after the renovation. In addition, thanks to the monitoring installed in the demonstrator building, the interior and exterior temperatures and the heat consumption of each of the radiators is known. In this way expected and real energy savings have been compared.

A simplified calculation process of buildings’ energy saving potential

The real estate sector is responsible for 40 percent of the energy consumption and one third of the CO2 emissions in Europe. Moreover one third of the European Union’s buildings are in fact older than 50 years while only one percent is being renovated each year. The building stock is therefore of great importance for the European Union in order to achieve its climate targets not only for 2020 but also long term. The difficulty however is to decide where and how to realize energy savings in the most efficient and economical way – especially for property owners with a large and heterogeneous building stock. This paper provides a simplified analysis method to evaluate real estate portfolios and estimate their buildings’ saving potential. This method has been integrated into AiBATROS®[1] software and can help to prioritize measures increasing energy efficiency. Verification and validation of the process are demonstrated comparing results with another method’s energy calculations.

Appliance Specific Feedback and Social Comparisons: Evidence From a Field Experiment on Electricity Saving

The provision of feedback about individual electricity consumption is a widely used approach to promote pro-environmental behavior. This form of feedback typically invokes social comparisons by informing households about their aggregate electricity consumption relative to others. While previous research has shown that aggregate consumption feedback translates into significant energy savings, the potential for further reductions may remain untapped because households lack knowledge about their appliance energy consumption patterns. In this paper, we present evidence from a field experiment, where we provide residents with feedback about their electricity consumption, specific to a high-energy use appliance (i.e. air-conditioner). We provide the relevant social norm information by varying the reference group of each resident. We find that our appliance-specific feedback is a powerful tool to curb electricity consumption. Residents significantly reduce their average air-conditioning usage by 17\% in our treatment groups. Notwithstanding, our effects are not driven by comparative feedback with respect to different reference groups. We interpret this as encouraging evidence to promote the use of appliance-specific feedback to realize energy savings.