Optimization of HVAC system energy consumption in a building using artificial neural network and multi-objective genetic algorithm

In this work, HVAC (Heating, Ventilation and Air Conditioning) systems applied in university buildings with control based on PMV (Predicted Mean Vote) and aPMV (adaptive Predicted Mean Vote) indexes are discussed. The building’s thermal behavior with complex topology, in transient thermal conditions, for summer and winter conditions is simulated by software. The university building is divided into 124 spaces, on two levels with an area of 5931 m2, and is composed of 201 transparent surfaces and 1740 opaque surfaces. There are 86 compartments equipped with HVAC systems. The simulation considers the actual occupation and ventilation cycles, the external environmental variables, the internal HVAC system and the occupants’ and building’s characteristics. In this work, a new HVAC control system, designed to simultaneously obtain better occupants’ thermal comfort levels according to category C of ISO 7730 with less energy consumption, is presented. This new HVAC system with aPMV index control is numerically implemented, and its performance is compared with the performance of the same HVAC system with the usual PMV index control. Both HVAC control systems turn on only when the PMV index or the aPMV index reaches values below −0.7, in winter conditions, and when the PMV index or the aPMV index reaches values above +0.7, in summer conditions. In accordance with the results obtained, the HVAC system guarantees negative PMV and aPMV indexes in winter conditions and positive PMV and aPMV indexes in summer conditions. The energy consumption level is higher in winter conditions than in summer conditions for compartments with shading, and it is lower in winter conditions than in summer conditions for compartments exposed to direct solar radiation. The consumption level is higher using the PMV control than with the aPMV control. Air temperature, in accordance with Portuguese standards, is higher than 20 °C in winter conditions and lower than 27 °C in summer conditions. In Mediterranean climates, the HVAC systems with aPMV control provide better occupants’ thermal comfort levels and less energy consumption than the HVAC system with PMV control.

Heating, Ventilation, and Air Conditioning (HVAC) systems are among the largest energy consumers in buildings, and their control strategies play a crucial role in achieving energy efficiency, indoor comfort, and sustainability. This review examines the main HVAC control strategies, ranging from traditional methods to Internet of Things (IoT) based and Artificial Intelligence (AI) driven approaches. In addition, occupancy-based control strategies and energy-efficient designs are critically examined for their potential to enhance system responsiveness and reduce operational costs. More than 100 recent research studies were systematically analyzed and compared across key parameters such as the objective of the study, the used control technique, strength, weakness, opportunity, threat, software/tool used, building type (residential, commercial, or industrial), control scale (single zone/multi-zone), and specific HVAC part controlled (e.g., AHU, VAV). To enable consistent comparison, a Multi-Objective Robustness Criterion (MORC) is used to assess how different control strategies balance energy consumption, thermal comfort, and Indoor Air Quality (IAQ) under changing conditions and how each control technique overcomes the limitations of the previous ones. In addition, the review also introduces a case analysis based on three U.S. cities, Charlotte, Greensboro, and Raleigh, to demonstrate the impact of outdoor climate variations and occupancy pattern on HVAC energy consumption. The results show that even a one-degree change in outdoor temperature can cause a considerable increase in annual energy consumption. Moreover, occupancy-based HVAC control can save more than $7,000 annually in the studied educational building. These findings highlight the strong impact of location-specific temperature differences on HVAC performance and emphasize the need for adaptive, climate-aware control strategies, while also pointing to future directions for smarter and more energy-efficient HVAC systems.

Heating, ventilation, and air conditioning (HVAC) systems are characterized by time-varying, nonlinear, and parametric coupling, making it challenging to design their controllers. As a major source of energy consumption in buildings, the control schemes for HVAC systems need to be optimized to improve energy efficiency. To address the above issues, a fuzzy controller was designed to regulate the HVAC system, and an improved snake optimizer (ISO) was proposed to optimize the membership function of the fuzzy controller in this study. In the ISO algorithm, the parameter Threshold of the snake optimizer (SO) was dynamically adjusted, and the snake egg-hatching formula was improved. Benchmark function tests show that the convergence speed and optimization accuracy of ISO are superior to those of the established comparison algorithms. Furthermore, simulation experiments indicate that the ISO-optimized HVAC system has a temperature error of 0 and a humidity ratio error of less than 1.5% compared to competing methods. In addition, the ISO-optimized HVAC system achieves a 40.8% reduction in annual energy consumption.

As a critical transportation infrastructure, with a high flow of people and high-energy consumption in China, coach stations have great potential in energy saving and CO2 emission reduction. In this paper, the building information and energy consumption data of 29 coach stations in five climate regions of China were obtained by field investigations. The annual total comprehensive building energy consumption was 31.37–128.08 kWh/(m2·a). The annual total CO2 emissions from building operation in the coach stations was 17.01–134.77 kgCO2/(m2·a). The heating, ventilation and air conditioning (HVAC) system was the largest energy using and CO2 emissions sector: 30.42–72.47% of the energy consumption and 30.42–83.93% of the CO2 emissions were generated by HVAC system. The energy consumption and CO2 emission level of coach stations and that of other kinds of public buildings were compared. Results showed that the energy consumption and CO2 emission levels of coach stations investigated were relatively low, mainly because the passenger thermal comfort was scarified. Based on the investigation data, energy consumption analysis models of coach stations in five regions were established by simulation when the passenger thermal comfort was met. The potentials of energy saving and CO2 emission reduction were studied from forms of the HVAC system, heat recovery and natural illumination.

Application of optimization techniques on lumped HVAC models for energy conservation

Modeling techniques used in building HVAC control systems: A review

The main purpose of this study is to evaluate the applicability of a liquid desiccant and evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS) in six typical cities in China. The six cities are located in different climatic zones in China and are selected because they are comparable owing to the outdoor air conditions. Many studies have shown that the annual operating energy consumption of LD-IDECOAS is nearly half compared with the conventional variable air volume (VAV) system. Because the climate characteristics of the six selected cities were different, the appropriate mode of operation of the LD-IDECAOS was applied to each studied city, and energy simulations were performed. Based on the design conditions of each region, the required cooling and heating loads were calculated for office buildings using transient system simulations (TRNSYS) 17, and the performance of the LD-IDECOAS and its energy consumption were simulated with a commercial engineering equation solver (EES) program. Depending on the climate characteristics of each city, adequate modifications were evaluated with simulations in terms of energy consumption. The proposed system was compared with the VAV system and the evaporative cooling assisted 100% outdoor air-conditioning system (IDECOAS) for detailed simulation results in the effort to evaluate the energy-saving potential. Finally, the results show that the proposed system saves considerable energy over conventional VAV systems and, in summer, the applications save even more energy than IDECOAS. However, there is a slight difference between the different geographical regions in terms of the annual operating energy consumption. In summary, the proposed system can yield significant energy-saving benefits in hot and humid regions whereas, in dry regions, the proposed system is more applicable in the summer. Consequently, LD-IDECOAS can be adopted for different climatic zones as a heating, ventilating, and air-conditioning (HVAC) system by introducing 100% outdoor air.

Energy-efficient personalized thermal comfort control in office buildings based on multi-agent deep reinforcement learning

A review of different strategies for HVAC energy saving

The main objective of this on-site study is to use a full-scale HVAC (Heating, Ventilating and Air-Conditioning) system installed in an office building in Taiwan for comparing the power consumption, energy-saving, and CO2reduction by variable primary flow (VPF) chilled water systems for controlling the HVAC. The on-site experimental results indicate that average power consumptions are 44,935 kWh for the constant volume (CV) chilled water systems, and 39,025 kWh for the VPF system. Approximately 19% of the maximum energy-saving rate can be achieved if the HVAC system is operated as a VPF system. Additionally, the reduced quantity of accumulated CO2emission varies from 0 to 44,186 kg with 0.623 kg-CO2kwh-1emission factor during the office hours of 08:00 (a.m.) to 20:00 (p.m.). The results demonstrate that switching the operation of an office building HVAC system from CV to VPF will significantly enhance energy savings and CO2reduction. This study is will offer useful information for evaluating an indoor environmental policy with respect to energy savings and CO2emission reduction for office HVACs used in subtropical regions.

On March 11, 2020, the World Health Organization declared the novel coronavirus (COVID-19) outbreak a global pandemic. Following this announcement, school closures around the United States began, and starting in June 2020, many schools decided to reopen for the next academic year or were planning to reopen. Guidance from ASHRAE and other organizations for reoccupying school buildings include wearing masks, increasing ventilation, increasing filtration, and using portable air cleaners (PAC).This report describes a simulation study that: (1) compares the relative reduction in aerosol exposure in education spaces as a result of changes to the operation of heating, ventilating, and air conditioning (HVAC) systems and inclusion of non-HVAC controls (e.g., wearing of masks and operating PAC) and (2) estimates the uncertainties in effectiveness associated with these controls and combinations of controls. This analysis used Fate and Transport of Indoor Microbial Aerosols (FaTIMA), a tool developed by the National Institute of Standards and Technology (NIST), to evaluate aerosol exposure in ventilated spaces. FaTIMA was used to model the release of biological aerosols in two classrooms and an assembly room with four different types of HVAC systems, including central air handling systems (CAHS), dedicated outdoor air systems (DOAS), terminal unit systems (TUS), and wall unit systems (WUS). Exposure was evaluated for 1 ?m particles (or aerosols) by which viruses are transported. In the classrooms, exposure was evaluated for 6 h of continuous exposure to a continuous source. In the assembly room, exposure was evaluated for 1 h of continuous exposure, where the source was present for the 5 h prior to the exposure period. For all the spaces and HVAC systems, the wearing of masks alone (assuming a protection efficiency of 25 % for both intake and exhalation) reduced exposure by 44 % relative to the base cases without masks. Masks with higher protection efficiencies (85 % to 90 %) reduced exposure 99 %, and masks with lower protection efficiencies reduced exposure 15 %. Masks with inhalation and exhalation protection efficiencies of 25 % combined with MERV 13 filtration in the HVAC systems reduced exposure by an average 71 % for the CAHS, DOAS, and TUS. For the CAHS, these masks combined with 100 % outdoor air (OA) intake reduced exposure by an average of 70 %. Using either a 297 clean air delivery rate (CADR) PAC or a 569 L?s-1 (1?200 cfm) exhaust fan with these masks, exposure was reduced by an average of 68 %. Combining all these controls, exposure was reduced by an average of 85 % assuming all controls were performing as intended. The results of this analysis may be useful in the selection of control options in educational facilities.

A demand-response method to balance electric power-grids via HVAC systems using active energy-storage: Simulation and on-site experiment

Efficient management of heating, ventilation, and air conditioning (HVAC) systems is paramount for mitigating energy consumption and enhancing climate resilience in modern infrastructure. This review explores the significance of leveraging project management tools to optimize energy efficiency within HVAC operations, thus fostering a pathway towards climate resilience. The integration of project management methodologies offers a systematic approach to address challenges associated with energy consumption in HVAC systems, thereby facilitating informed decision-making processes. Firstly, the review delves into the pressing need for energy conservation in HVAC operations amidst escalating concerns over climate change and its adverse impacts. The imperative to minimize energy consumption in buildings, particularly through HVAC systems, is highlighted as a pivotal step towards achieving climate resilience and sustainability goals. Subsequently, the review outlines the role of project management tools in orchestrating effective strategies to enhance energy efficiency within HVAC operations. By employing techniques such as project scheduling, risk management, and resource allocation, project managers can streamline the implementation of energy-efficient measures, thereby optimizing HVAC system performance and reducing carbon emissions. Moreover, the review underscores the importance of data analytics and technological advancements in augmenting the efficacy of project management tools for energy efficiency in HVAC operations. Leveraging real-time data monitoring, predictive analytics, and IoT-enabled devices enables proactive maintenance and continuous optimization of HVAC systems, thereby maximizing energy savings and bolstering climate resilience. Furthermore, the review elucidates the potential benefits and challenges associated with the adoption of project management tools for energy efficiency in HVAC operations. While improved cost-effectiveness, environmental sustainability, and operational performance emerge as primary benefits, challenges such as initial investment costs, technological complexities, and organizational inertia necessitate careful consideration. This review advocates for the integration of project management tools as a viable approach to foster energy efficiency in HVAC operations, thereby paving the way towards enhanced climate resilience and sustainability in built environments. By embracing innovative methodologies and technological solutions, stakeholders can mitigate energy consumption, reduce greenhouse gas emissions, and fortify infrastructure against the impacts of climate change. Keywords: HVAC, Climate Resilience, Project Management, Energy, Review.

Coach station has the characteristics of high-density passenger flow, long operation time, large number of energy-consuming equipment and so on, which leads to the problem of high energy consumption. Based on the field investigation of six coach stations in Tianjin, the general building information such as architecture overview, major energy-consuming equipment, energy construction and consumption was obtained. The total energy consumption and sub-item energy consumption of each coach station were analyzed and calculated according to the investigation data. The results showed that the annual total energy consumption per unit area of the coach stations in 2017 ranged from 41.55 kWh/(m2·a) to 128.08 kWh/(m2·a), with an average of 76.53 kWh/(m2·a). The heating, ventilation and air conditioning (HVAC) system were the main component of building energy consumption, accounting for an average of 68.26% of the total energy consumption, indicating that the HVAC system of this type of buildings had a great potential for energy saving and reconstruction. Analyzed by the statistical software SPSS, the air conditioning form and heating form were significantly related to the total annual power consumption per unit area.

Optimization of thermal processes in a variable air volume HVAC system