Total Electricity Use Research Articles

Comparative study on the overall energy performance between photovoltaic and Low-E insulated glass units

A novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable.

Clustering-based probability distribution model for monthly residential building electricity consumption analysis

Electricity is now the major form of energy used in residential buildings and has seen a significant increase in usage over the past decades. One of the main features of electricity use in residential buildings is the diversity of total electricity consumption and use patterns among households. Current models may not be able to simulate and generate electricity use curves or reflect the variations accurately. To fill this gap, this research simulates electricity use curves in residential buildings with a clustering-based probability distribution model. The model extracts feature parameters to represent the electricity use level and patterns and then conducts a two-step cluster analysis to identify the distinctions of both electricity use levels and patterns. Based on the clustering results, probability distributions are fitted for all feature parameters within each sub-cluster. The model is then validated with three validation approaches. Monthly electricity consumption in households of the Jiangsu Province, China, was studied to test the performance of the model. Lastly, this paper discusses the application of this model under different spatial resolutions and analyzes the temporal-relevant model features.

On the Performance of Night Ventilation in a Historic Office Building in Nordic Climate

The effect of mechanical night ventilation on thermal comfort and electricity use for cooling of a typical historic office building in north-central Sweden was assessed. IDA-ICE simulation program was used to model the potential for improving thermal comfort and electricity savings by applying night ventilation cooling. Parametric study comprised different outdoor climates, flow rates, cooling machine’s coefficient of performance and ventilation units’ specific fan power values. Additionally, the effect of different door schemes (open or closed) on thermal comfort in offices was investigated. It was shown that night ventilation cannot meet the building’s total cooling demand and auxiliary active cooling is required, although the building is located in a cold climate. Night ventilation had the potential in decreasing the percentage of exceedance hours in offices by up to 33% and decreasing the total electricity use for cooling by up to 40%. More electricity is saved with higher night ventilation rates. There is, however, a maximum beneficial ventilation rate above which the increase in electricity use in fans outweighs the decrease in electricity use in cooling machine. It depends on thermal mass capacity of the building, cooling machine´s coefficient of performance, design ventilation rate, and available night ventilation cooling potential (ambient air temperature).

Assessing the demand response capacity of U.S. drinking water treatment plants

This study assesses the spatio-temporal electricity consumption and demand response (DR) capacity of U.S. drinking water treatment plants (DWTPs). We account for the installed unit processes at each plant, the electricity intensity of each unit process, the compatibility of a unit process with DR participation, and the approximate volume of water treated at each DWTP during different months of the year. We then perform a parametric analysis to calculate the shiftable load from DWTPs as a function of the length of the load curtailment period (TC), the ratio of the maximum treatment capacity to the peak-day demands of DWTPs (rmax), and the time of the year. The results of the parametric analysis suggest that the total DR capacity of U.S. DWTPs in 2018 varied between 140 MW and 610 MW as a function of TC, rmax and time of the year. We also find that the total electricity use by DWTPs has increased 25% from 2013 to 2018, largely due to the rapidly increasing adoption rate of reverse osmosis processes. These results indicate that DWTPs provide only minimal DR capacity in most locations in the U.S, but that further electrification of the drinking water treatment sector may significantly increase this DR capacity in critical geographic locations during peak summer months.

Impacts of technology-guided occupant behavior on air-conditioning system control and building energy use

Occupant behavior is an important factor affecting building energy consumption. Many studies have been conducted recently to model occupant behavior and analyze its impact on building energy use. However, to achieve a reduction of energy consumption in buildings, the coordination between occupant behavior and energy-efficient technologies are essential to be considered simultaneously rather than separately considering the development of technologies and the analysis of occupant behavior. It is important to utilize energy-efficient technologies to guide the occupants to avoid unnecessary energy uses. This study, therefore, proposes a new concept, “technology-guided occupant behavior” to coordinate occupant behavior with energy-efficient technologies for building energy controls. The occupants are involved into the control loop of central air-conditioning systems by actively responding to their cooling needs. On-site tests are conducted in a Hong Kong campus building to analyze the performance of “technology-guided occupant behavior” on building energy use. According to the measured data, the occupant behavior guided by the technology could achieve “cooling on demand” principle and hence reduce the energy consumption of central air-conditioning system in the test building about 23.5%, which accounts for about 7.8% of total building electricity use.

Investigating the performance of a hybrid PV integrated shading device using multi-objective optimization

PV integrated shading devices (PVSDs) are an interesting case study for an optimisation problem as their design is non-trivial and they must balance competing parameters and uses of solar energy. In this study, the case of a south-facing, exterior louvre blade PVSD was used to investigate how multi-objective optimisation (MOO) coupled to a parametric design approach can be used as a support tool to improve the performance of the system in four different cases. The parameters optimized were the individual tilt angle of each louvre-blade (0, 15, 30 or 45 ° from the horizontal), the vertical distribution of the blades, and the type of material on the upper surface of each louvre (reflective coating or PV cells). The objectives of the optimisation were to minimise the total annual net energy electricity use and to maximise the daylighting level in the zone. The results of the investigation showed that PVSD configurations with higher louvre counts performed better as hybrid systems as they allowed to increase daylighting compared to classic, fully PV coated systems and did not increase energy use in the zone significantly. However, for systems with lower counts of louvres, the results of the optimisation showed that the surface of the louvres was more useful as a PV element, as reflective materials had little effect on the daylighting in the zone and the reduction in energy converted noticeably affected the energy performance of the building.

Cost-saving electrical energy consumption in underground ventilation by the use of ventilation on demand

ABSTRACTElectricity is one of the biggest expenses associated with underground mining and ventilation often accounts for 50% of the total electricity use. Ventilation on demand is not widely used in Brazil, but the Ipueira, Cuiaba, and Corrego do Sitio I mines reported savings of 26%, 30%, and 21%, respectively, following its application. Frequency inverters are used to control the rotation of the main fans during shift changes. The Cuiaba mine has a control room and fans are monitored online using wireless scattered sensors. Data from field studies were compared to other foreign mines. The results showed that the application of this technique, even in an experimental way, can reduce electricity consumption significantly. Despite the energy savings that can be achieved by providing air only when/where it is needed, the costs of automation, software, and infrastructure mean that it is not practical to apply this technique at a more advanced level.

Bayesian Hybrid Collaborative Filtering-Based Residential Electricity Plan Recommender System

The deregulation of the electricity market enables residential customers to select suitable electricity retailing plans. This paper proposes a Bayesian hybrid collaborative filtering-based electricity plan recommender system (BHCF-EPRS), which is constructed in a two-stage model integrated with model-based and memory-based collaborative filtering methods. Bayesian inference is developed for missing feature estimation and user classification. Free from the requirements on total electricity use data and historical plan transaction data, the BHCF-EPRS can recommend suitable retailers and plans based on some easily obtainable features quantifying home appliance usage patterns. The BHCF-EPRS is verified to be a reliable recommender system with low error in full-ranking recommendation and high precision in top-N recommendation, which can improve the competitive operation of the electricity market.

Study of Residential Thermal Transfer Values (RTTV) and Vertical Daylight Factor (VDF) for Hong Kong

In Hong Kong, over one-quarter of the total electricity use was consumed by residential buildings. Recently, the Hong Kong Government issued a practice note namely Design and Construction Requirements for Energy Efficiency of Residential Buildings. This practice note set out the Residential Thermal Transfer Values (RTTV) of building envelopes. To enhance energy efficiency of residential buildings, the RTTV of wall (RTTVwall) and roof (RTTVroof) should not exceed 14 and 4 W/m2, respectively. Being one of the most densely populated cities in the world, most of building developments in Hong Kong are high-rise blocks located in densely built zones. The shading effects due to surrounding buildings could substantially restrict the diffuse light coming from the sky. In 2003, a practice note on lighting and ventilation requirements was issued. Referring to the performance-based approach, the note adopted the vertical daylight factor (VDF) to specify the daylighting performance of the building. The VDF should not be less than 8% for habitable rooms and 4% for domestic kitchens. This paper presents the energy performance of recently designed building fulfills the RTTV requirements. It found that VDF is a good indicator to shows the lighting elecricty consumption in buildings. For most of the bedroom, about 40% of air conditioning and 3 % lighting energy can be saved.

An Intelligent Internet of Things (IoT) Sensor System for Building Environmental Monitoring

One of the world’s largest sources of energy dissipation is heating, ventilation, and air conditioning (HVAC), which accounts for 40% of total electricity use in the United States. The main challenge of current HVAC systems is that their operation is determined by a set of predefined setpoints regardless of the actual building occupancy status. This is wasteful, especially when no or fewer people occupy buildings, while these HVAC systems deliver more than enough fresh air. Occupancy-driven HVAC control is a promising strategy to improve the efficiency of HVAC systems. In this paper, we will address the next-generation sensor hardware design and explore new system architectures. We systematically investigate, design, and implement a lowcost, hybrid smart sensor platform for accurate occupancy counting towards energy-efficient buildings. Specifically, the proposed hardware architecture is wisely divided into two modules: main and gate monitoring modules. Five heterogeneous sensors are integrated into this architecture to collect richer building environmental parameters, including temperature, humidity. CO2, acoustic, and infrared signals. These sensor signals can be fused and analyzed for cross-correlation to increase the accuracy of building occupancy counting. The proposed systems have been implemented in breadboards and PCB boards. Experimental measurements have validated system functionality and performance.

Energy efficiency of exhaust air heat recovery while controlling building air humidity: A case study

One modern method of lowering building energy use is heat exchange between outgoing and incoming air. Exhaust air moisture (partly) condenses in the heat exchanger, giving liquid water to be removed. With low absolute humidity of inlet air especially at low outdoor temperatures, a significant drying effect results for the air inside the building. Increasing air humidity by, for example, spraying water or increasing watering of plants will give an energy penalty. This paper presents an analysis of the energy efficiency (recovered versus input exergy) of a modern house equipped an exhaust air heat recovery system and external heating supplied by a geothermal heat pump. Indoor temperature is 22 °C and relative humidity is 50 or 30%. Temperature and humidity of inlet air and ventilation flow rates are variable and the effects on power use by the heat pump are assessed. Results show that without moisture recirculation a water loss up to 1 kg/h from the building may occur. Several kWh of electricity may be consumed daily by a (geothermal) heat pump supplying heat depending on outdoor temperature, and indoor and outdoor air humidity. Besides water consumption, this may imply 10–15% of total electricity use.

Opportunities to improve energy use in urban wastewater treatment: a European-scale analysis

Wastewater treatment is an essential public service that has a major impact on energy use in the urban water cycle, thus receiving increasing attention in context of the Water-Energy Nexus. Understanding the current energy use for wastewater is an essential step to design reliable policies promoting a more efficient use of resources. This paper develops a pan European estimation of electricity use for the treatment of wastewater, based on a dataset of wastewater treatment plants (WWTPs) across the continent. Prediction of electricity use has been performed using a statistical model that accounts for economies of scale. Different scenarios of improvements of energy use efficiency have been investigated to understand the possible reductions in electricity consumption at the continental scale. The overall WWTP electricity use in Europe (only plants with no less than 2000 population equivalent (PE) have been considered) was estimated at 24 747 GWh yr−1, about the 0.8% of the electricity consumption in the EU-28. Small plants (less than 50 000 PE) represent almost 90% of the total number of plants, but process only 31% of the PE and require 42% of electricity use. Plants from mid to very large size (more than 50 000 PE), being only 10% of the plants, process about 70% of the PE with 58% of the total electricity use. If all plants that use more than the current average were shifted to the average value, the saving would be slightly more than 5500 GWh yr−1. With highly stringent targets of efficiency improvement, saving of about 13 500 GWh yr−1 could be expected. Further considerations on the emerging role of WWTPs as energy and material producer are finally discussed.

A cooler cloud: A new type of thermal conductor cools data centers without water, refrigerants, chillers, or server fans - [News

Data centers are hungry, hot, and thirsty. The approximately 3 million data centers in the United States consume billions of liters of water and about 70 billion kilowatt-hours of electricity per year, or nearly 2 percent of the nation's total electricity use. About 40 percent of that energy runs air conditioners, chillers, server fans, and other equipment to keep computer chips cool.

An Intelligent Internet of Things (IoT)Sensor System for BuildingEnvironmental Monitoring

One of the world’s largest sources of energy dissipation is heating, ventilation, and air conditioning (HVAC), which accounts for 40% of total electricity use in the United States. The main challenge of current HVAC systems is that their operation is determined by a set of predefined setpoints regardless of the actual building occupancy status. This is wasteful, especially when no or fewer people occupy buildings, while these HVAC systems deliver more than enough fresh air. Occupancy-driven HVAC control is a promising strategy to improve the efficiency of HVAC systems. In this paper, we will address the next-generation sensor hardware design and explore new system architectures. We systematically investigate, design, and implement a lowcost, hybrid smart sensor platform for accurate occupancy counting towards energy-efficient buildings. Specifically, the proposed hardware architecture is wisely divided into two modules: main and gate monitoring modules. Five heterogeneous sensors are integrated into this architecture to collect richer building environmental parameters, including temperature, humidity. CO2, acoustic, and infrared signals. These sensor signals can be fused and analyzed for cross-correlation to increase the accuracy of building occupancy counting. The proposed systems have been implemented in breadboards and PCB boards. Experimental measurements have validated system functionality and performance.

Data center growth in the United States: decoupling the demand for services from electricity use

Data centers are energy intensive buildings that have grown in size and number to meet the increasing demands of a digital economy. This paper presents a bottom-up model to estimate data center electricity demand in the United States over a 20 year period and examines observed and projected electricity use trends in the context of changing data center operations. Results indicate a rapidly increasing electricity demand at the turn of the century that has significantly subsided to a nearly steady annual electricity use of about 70 billion kWh in recent years. While data center workloads continue to grow exponentially, comparable increases in electricity demand have been avoided through the adoption of key energy efficiency measures and a shift towards large cloud-based service providers. Alternative projections from the model illustrate the wide range in potential electricity that could be consumed to support data centers, with the US data center workload demand estimated for 2020 requiring a total electricity use that varies by about 135 billion kWh, depending on the adoption rate of efficiency measures during this decade. While recent improvements in data center energy efficiency have been a success, the growth of data center electricity use beyond 2020 is uncertain, as modeled trends indicate that the efficiency measures of the past may not be enough for the data center workloads of the future. The results show that successful stabilization of data center electricity will require new innovations in data center efficiency to further decouple electricity demand from the ever-growing demand for data center services.

Creation of Zero Carbon Emissions Wastewater Treatment Plants - A Case Study in Crete, Greece

Wastewater treatment plants use energy intensive processes for removing pollutants, consuming large amounts of electricity and emitting greenhouse gases. The possibility of zeroing carbon emissions due to energy use in these plants has been investigated in the current work with reference to the municipal treatment plant of Chania on the island of Crete, Greece. The sewage treatment plant processes 19,400 M3 daily consuming 0.543 KWh per M3 or 3840 MWh annually. The use of locally available renewable energies has been proposed for electricity generation combined with co-generation of heat and power from the biogas already produced in the plant with sludge digestion. Installation of solar-PV systems and wind turbines in the plant could generate electricity, each equal to 25 % of the annual electricity consumption in the plant. Additionally, biogas use can cover all the heating needs in the plant and can generate electricity corresponding at 20% of the total annual grid electricity use. Creation of a tree plantation, irrigated by the treated effluent, of 118.4 hectares, has been proposed which could annually offset carbon emissions due to the remaining grid electricity use. Creation of the tree plantation will create additional benefits, due to existing land desertification in Crete, additionally to carbon sequestration. The size of the required solar-PV and wind turbine systems has been estimated at 640 KWp and 391 KW and their cost at 0.832 mil € and 0.430 mil € correspondingly. Current work indicates that the combined use of solar energy, wind energy, biogas and carbon sequestration with tree plantations could zero carbon emissions in the municipal sewage treatment plant of Chania, Crete.

Long-term field investigation and modeling of electricity end-use patterns in hotel guest rooms

This paper presents the results of a long-term, detailed electricity end-use analysis of hotel guest rooms in order to provide a better understanding of the electricity use patterns in guest rooms and their explanatory factors. To accomplish this, a one-year of sub-hourly electricity measurements for an entire floor and major electricity end uses of fourteen guest rooms in a case-study hotel in Washington, D.C. were analyzed along with coincident weather and occupancy data collection. A regression analysis was performed on the monthly and daily end-use electricity data to identify key variables affecting different electricity end uses of the guest rooms. As a result, it was found that a regression model with a single temperature variable did not fully describe the electricity use behaviors of hotel guest rooms. The addition of the occupancy variable significantly improved the model fit for both monthly and daily total floor electricity use and was statistically significant. A review of the electricity end uses showed strong correlations between outdoor temperature and the electricity end uses for space conditioning, especially the DOAS unit and the VRF outdoor unit. However, for other end uses such as plug loads, lighting, and the VRF indoor units, the observed correlations to outdoor temperature were not significant but were moderately correlated to occupancy.

Low‐Cost, Organic Light‐Emitting Electrochemical Cells with Mass‐Producible Nanoimprinted Substrates Made Using Roll‐to‐Roll Methods

Next‐generation, power‐efficient organic lighting systems, which ideally would be low‐cost and mass‐producible, are urgently needed because more than 20% of total electricity use goes to lighting. This study presents polymer light‐emitting electrochemical cells (PLECs) made using mass‐producible nanoimprinted corrugated substrates, which effectively improve light extraction efficiency. The corrugated substrates are fabricated using roll‐to‐roll methods, using self‐assembled block copolymers on glass and film substrates (glass: 0.45 m × 0.55 m, film: 0.6 m wide). Using the glass‐type corrugated substrates, two PLECs based on (poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene]) and (“super‐yellow” poly(p‐phenylene vinylene)) (SY‐PPV) are fabricated by solution‐based spin‐coating methods, which can in practice be replaced by roll‐to‐roll methods. The corrugated PLECs with SY‐PPV show high brightness of 1740 cd cm−2 and 2.1 times greater efficiency without changing the original spectrum or angular dependence. This successful combination of corrugated substrates and PLECs is one of the best examples of a promising cost‐effective, high‐performance lighting technology.

An investigation of the impact of building orientation on energy consumption in a domestic building using emerging BIM (Building Information Modelling)

BIM (building information modelling) has developed into a powerful solution that can improve many aspects of construction industry. Current research regarding the impact of orientation on a building's energy needs seldom tap into the potential of BIM. This study investigates the impact of orientation on energy consumption in small-scale construction, and assesses how BIM can be used to facilitate this process. The methods adopted are three-fold. Firstly, a real-life building is modelled using Revit, one of the leading BIM tools. Secondly, through green building Extensible Markup Language, the model is exported to Green Building Studio, one of the leading energy simulation software. Thirdly, in the Green Building Studio, different building orientations are adopted and their impacts of the whole building energy are investigated. Based on the analysis of the energy consumption corresponding to the different orientations, it emerged that a well-orientated building can save a considerable amount of energy throughout its life cycle. Specifically, a total electricity use difference of 17 056 kWh and a total gas use difference of 27 988 MJ leading to a combined energy cost savings of £878 throughout a 30 year period between the best (+180°) and worst (+45°) orientations of the building was achieved.

Investigation of Building Walls Exposed to Periodic Heat Transfer Conditions for Green and Energy Efficient Building Construction

Buildings account for about 40% of total electricity use in the world for artificial cooling and artificial day lighting and they are also responsible for 40% CO2 emissions. This work reports a comprehensive investigation of thermal performance characteristics which include thermal transmittance, thermal admittance, decrement factor and the time lag for both homogeneous and composite building walls. A computer program with the cyclic admittance method was developed to study unsteady thermal performance characteristics. The Five building materials such as, cellular concrete, mud brick, concrete block, burnt brick and fly ash bricks were selected for the study. The heat transfer characteristics of five homogeneous building walls and their five composite walls were studied in detail. From the results, it is observed that fly ash brick homogeneous walls and their composite walls are energy efficient from the lowest decrement factor and the highest time lag perspective among five homogeneous and five composite walls studied. The decrement factor and time lag values of homogeneous fly ash bricks were observed to be 0.401 and 8.159h, respectively, whereas the values of composite fly ash brick walls were observed to be 0.342 and 9.199h, respectively.