Stable Indoor Temperature Research Articles

Evaluation of energy-saving potential and indoor thermal environment of passive solar houses in various heating climate regions of China

ABSTRACT Passive solar houses comprise crucial strategies of reducing heating and cooling energy for buildings, which have been extensively used in plenty of nations. This study develops a study on indoor thermal environment, the energy-saving performance and natural lighting in different heating climate regions (represented by Lhasa, Xining and Urumqi). An attached-sunspace solar house integrated with phase change material floors is also proposed to ameliorate indoor thermal comfort and simultaneously diminish the heating energy consumption. In addition, the dominant factors analysis of building envelope affecting building energy consumption are sensitively studied. Moreover, the influence of the depth of sunspace and the intensities of internal heat gain on indoor thermal conditions and heating energy consumption are further analyzed. The results indicate that among the three types of solar houses, the passive solar sunspace offers the most stable indoor temperature and Trombe-wall solar houses and attached-sunspace solar houses have striking energy-saving advantages compared with the traditional houses. And the annual power consumption of 695.1 kWh, 427.4 kWh and 688.8 kWh in Lhasa, Xining and Urumqi can be saved in view of natural lighting respectively. Additionally, the whole natural temperature of attached-sunspace solar house is on the rise apparently when the PCM floors are embedded in the house and the energy saving fraction of these three regions is 81.9% for Lhasa, 68.8% for Xining, 55.7% for Urumqi respectively with the integration of phase change floors. The sensitivity analysis of key parameters impacting building energy consumption from high to low are the heat transfer coefficient of external wall, the ratio of window to wall, air tightness, the heat transfer coefficient of external window, and the heat transfer coefficient of roof. The depth of 1.2 m for sunspace is recommended as the optimal choice. Indoor natural temperature is on the rise as intensities of internal heat gain increase. The same downward trend for the main bedroom and the whole building is displayed with the increasing interior heat sources in terms of annual heating load.

Carbonated balsa-based shape-stable phase change materials with photothermal conversion and application in greenhouse

Greenhouse enables to promote plant yield through creating optimal environment. Efficient solar energy conversion and storage is a promising strategy to address energy shortage issue of greenhouse in winter. This paper prepares form-stable composite phase change materials (PCMs) to store solar energy efficiently. Lightweight and porous balsa wood subjected to high-temperature carbonization is designed to simultaneously solve the liquid leakage, enhance the thermal conductivity, and improve the photothermal conversion and thermal energy storage of PCM. OP44E and SEBS are utilized as PCM and thickener, followed by vacuum impregnation into the carbonized balsa wood (CW). Results indicate that carbon content of CW increases with the augment of carbonization temperature. Shaping effects of CW and SEBS endow composite PCMs to have highest adsorption rate of 92.7 wt% with enthalpy over 190 J/g. Composite PCMs reveal reliable thermal properties and thermal stability below 100 °C. Composite PCMs have photothermal conversion larger than 88 % under a xenon lamp radiation. Temperature of PCMs on the shallow layer is higher owing to its photothermal conversion capacity. Greenhouse test indicates that CW/OP44E/SEBS greenhouse gains higher PCM temperature of 71.5 °C at 70 min, compared to 40.3 °C in empty and OP44E/SEBS cases. CW/OP44E/SEBS greenhouse maintaining indoor temperature over 20 °C lasts 15.3 min longer than empty and OP44E/SEBS greenhouses. In addition, form-stable composite PCMs featured with excellent thermal stability and photothermal conversion are capable of maintaining stable indoor temperature of greenhouse, indicating potential in the field of agricultural building temperature regulation.

Integrated Room Monitoring and Air Conditioning Efficiency Optimization Using ESP-12E Based Sensors and PID Control Automation: A Comprehensive Approach

This study addresses the critical need for efficient room monitoring and air conditioning systems, particularly in educational settings like the STMIK STIKOM Indonesia campus. The paper introduces a novel approach that combines ESP-12E based sensors with Proportional-Integral-Derivative (PID) control automation to optimize air conditioning efficiency. Utilizing an ESP-12E microcontroller, the study designed and implemented a room monitoring tool equipped with DHT22 and BH1750 sensors for accurate measurement of temperature, humidity, and light intensity. We also explores the integration of a PID control system into an existing air conditioning (AC) unit. The PID controller was fine-tuned to maintain a stable indoor temperature of 25oCelsius, even when subjected to external heat loads, such as ten LED lamps. The effectiveness of this system was quantified through real-time monitoring of temperature, humidity, and energy consumption, both pre- and post-implementation. Results indicated a rapid and stable response from the PID controller, achieving an amplitude of 1 within 0.08 seconds, thereby confirming its successful tuning and adaptability. We found that this study has broader implications for enhancing energy efficiency and creating conducive learning environments. However, it is worth noting that the research was conducted under specific conditions, and further studies could explore its applicability in different settings.

The energy saving performance of the thermal diode composite wall in different climate regions

The effective management of energy consumption during building operations continues to be of utmost importance. The role of a building's envelope in regulating energy consumption is critical. However, traditional building insulation systems often struggle to maintain optimal indoor temperatures in the face of fluctuating external temperatures. Solar energy, for instance, can easily penetrate a room through windows during the cooling season, leading to increased energy consumption. Similarly, heat dissipates easily during the heating season. To address these challenges, thermal diode composite walls with unidirectional heat transfer offer a groundbreaking approach to simplifying the design of thermal management systems. The thermal diode composite wall effectively controls heat conduction, convection, and radiation through the implementation of different functional layers. By regulating the heat flux through the building envelope, this technology significantly reduces energy consumption during building operations while maintaining a stable indoor temperature. To evaluate the performance of an adaptable thermal diode composite wall, we designed, implemented, and conducted tests on a thermal diode composite wall building. The results of the study demonstrate substantial energy savings, ranging from 3.5% to 69.3% for annual operation in various regions, with better performance observed in colder regions. In the forward heat conduction mode, the temperature difference between the inside and outside wall surfaces reached a maximum of 20.99 K, while in the reverse mode, it reached −35.67 K. These findings highlight the remarkable potential of thermal diode composite walls in significantly improving the energy efficiency and comfort of buildings. Consequently, the adoption of thermal diode composite walls presents numerous opportunities for the development of low-carbon buildings.

Assessing the co-heating test as reference for heat loss coefficient estimation: In-depth analysis on an artificial dataset

In order to bridge the building energy performance gap it is necessary to quantitatively and qualitatively characterize the actual energy demand of buildings and the thermal behaviour of their envelopes. Current European legislation prescribes the assessment of the energy efficiency of the building stock by means of energy performance certification, which labels the building performance based on theoretical data and specifications reflecting the design phase. At the current state, in most European countries such certificates provide the only insight into the overall performance of the building stock, while the need of characterizing the actually achieved building behaviour is recognized. The most common testing procedure used with the aim of characterizing the as-built thermal performance of commissioned dwellings is the co-heating test. It consists of a prescribed measurement procedure where a vacated house is submitted to an elevated indoor temperature. During the experiment, the indoor and outdoor environment, as well as the energy demand needed to maintain the stable indoor temperature are precisely monitored. Up to date, this testing procedure is acknowledged as the most reliable in practice, however, the limitations of the methodology are not yet completely explored and unambiguously defined. Thus, the aim of this work is to explore the limits of the co-heating testing procedure on artificially generated experiments which provide a completely defined environment and reference targets. To assess the impact of different aspects, such as the parameters of the statistical models or monitoring period and length, the artificial datasets provide the ideal conditions since the impact of measurement inaccuracy can be avoided and the expectations of the methodology itself can be evaluated. The main findings complement the prevalent research and indicate the possibility of assessing the building performance in the 10% bounds from the target, however considering idealised monitoring data. The research shows that using global horizontal instead of south vertical irradiation can provide overall more accurate results, especially in transient months. Finally, when assessing suitable periods for performing tests in a moderate climate, only 20% of the whole year can be considered to yield satisfactory results.

Effects of microencapsulated phase change material on indoor thermal comfort and energy consumption

Phase change materials, PCMS can be also used in thermal energy systems with various building materials in order to increase thermal performance. In this study, artificial marble with microencapsulated PCM (MPCM) was fabricated and its indoor environmental control and energy saving effects were analyzed using field tests in a standard Korean apartment building. The MPCM capsules contained approximately 70% n-octadecane and were fabricated using the in situ polymerization chemical method. The thermal environment was analyzed using internal temperature and the predicted mean cote (PMV) measurements. The results of the wall board with MPCM installed room temperature fluctuation decreased by 1–2 °C that it was possible to maintain a stable indoor temperature due to the thermal buffering effect. The average change of PMV was −0.03 for 12 h that no significant effect on the thermal comfort. The results of convection heating system energy consumption was reduced by 27.7%. Furthermore, we studied the long-term real-scale thermal performance in winter seasons.

A Model Predictive Control for Heat Supply at Building Thermal Inlet Based on Data-Driven Model

At present, the traditional control strategy of heating systems is still unable to achieve building heating on demand, which enhances the energy consumption of heating and affects the thermal comfort of buildings. Therefore, this study puts forward a novel data-driven MPC for building thermal inlet, which allows the optimal operation of the district heating system and has been verified by simulation with three public buildings. In this method, the indoor temperature at the next moment reaches the temperature set value by changing the current flow rate. First, based on the energy consumption monitoring platform and the measured data of the buildings, the building indoor temperature prediction model at the next moment is established by using long short-term memory (LSTM). Compared with subspace model identification (SMI), LSTM has higher prediction accuracy, and the R2 was about 0.9 in three buildings. Second, the particle generated by particle swarm optimization, which represents the flow variation, is input to the trained LSTM to predict the indoor temperature. By minimizing the objective function, the optimal flow change at the current time can be calculated. The results showed that the MPC based on a data-driven model can adjust the flow rate in time to maintain a stable indoor temperature with ±0.5 °C error. In addition, when the temperature setting needs to be changed, the indoor temperature can reach the new set value in 3 h, which outperforms the PID control. The method proposed in this paper can greatly reduce the influence of regulation lag by adjusting the flow in advance.

Optimization for the Model Predictive Control of Building HVAC System and Experimental Verification

This article presents an optimized prediction model of building dynamic HVAC system load, which simplifies the input parameters of the model while meeting the accuracy requirements of the prediction results. The model was established using the open-source Modelica-based building library, and the linear aggregation method was used to establish the model. A reduced-order model was developed, and the accuracy of the simplified and reduced-order models was verified. A control strategy was constructed using the indoor mean radiant temperature (MRT) aggregated from a simplified prediction model of HVAC system load as the target feedback parameter, and its feasibility was verified experimentally. It was found that the MRT adopted by the new control strategy can reflect the changes in outdoor air temperature and load in a timely manner; moreover, using this as a control parameter can significantly reduce the influence of load changes to maintain a stable indoor temperature. The control system is further simplified by the predictive model, which improves the engineering practicability by maintaining the control accuracy.

Smart glazing thermal comfort improvement through near-infrared shielding paraffin incorporated SnO2-Al2O3 composite

Building’s energy conservation signifies a lowering in building energy consumption without sacrificing thermal comfort. Window glazing is the most suitable approach to the built environment that can be controlled through its sustainable development for global energy consumption. In this work, for the first time, paraffin incorporated SnO2-Al2O3 composite coating is developed on a 5 cm × 5 cm glass using a screen-printing method, which signifies an intelligent cooling behaviour for a comfortable indoor environment irrespective of their emplacement. The composite energy-saving properties exhibit less transmission of infra-red light while keeping high visible light transmittance behaviour resulting superior heat-shielding performance. The composite coated glass's average indoor temperature profile remains at ∼30 °C when the outside temperature reaches a maximum of 45 °C during outdoor testing. While the same composite film is set inside, the indoor average temperature maintains ∼30 °C, whereas outside temperature reaches a maximum of 80 °C.The distinct temperature profile for composite coated glass indicates high transparency of 80% throughout the experiment. Interestingly paraffin has been incorporated into the composite, offering no leakage, translucent characteristics, and limited water ingress. In comparison, non-coated glass is failed to provide them with a comfortable, stable indoor temperature. We believe this study envisages the recent technological innovations combined with phase change material and transparent infrared absorber together as a composite for window glass for warmer climates, which further leads to significant energy savings compared with plain glass.

Application of energy-saving control strategy in air conditioning terminal equipment based on constant temperature difference of chilled water

Effectively reducing the energy consumption of central air conditioning systems is an important aspect of building energy efficiency. The energy consumption of terminal equipment accounts for over 25% of that of air conditioning systems. Although the heat and moisture exchange mechanism of the terminal unit has been extensively studied, studies on control strategies for terminal unit operation are lacking. This study proposes an energy-saving optimization control strategy for terminal units based on the constant temperature difference of chilled water in an engineering application study. A fan coil unit (FCU) controller was designed and manufactured, and a Local Area Network (LAN) control system was constructed and compared to determine the optimal control strategy. When adopting the energy-saving optimization control strategy for the terminal unit based on a constant chilled water temperature difference, the energy consumption of the terminal equipment was significantly decreased by 7.2%. The flow rate of chilled water was reduced by 26.94% when the indoor air temperature requirements were met, effectively reducing the energy consumption of the central air-conditioning system. The adjustment time required to reach a stable indoor temperature was reduced and environmental comfort was improved. These results demonstrate the potential of this control strategy for use in engineering practices to replace traditional control modes.

Study on the design of heating and energy saving of enclosure structure of rural self-built houses

For severe cold areas, indoor heating in winter is very important, and it is also important to achieve energy saving and emission reduction in the heating process. This paper briefly introduced a kind of heating envelope structure, the geothermal energy-based phase change wall, and analyzed two rural self-built houses in Shangluo city, Shaanxi province. One self-built house was built without the phase change wall, and the other was built with the geothermal energy-based phase change wall by the municipal government. The results showed that the self-built house that adopted the phase change wall had a better heat preservation effect and relieved the indoor temperature fluctuation; after the heating equipment was turned on, the self-built house that adopted the geothermal energy-based phase change wall had a higher and more stable indoor temperature, and the power consumption during the experiment was less.

Comparison of temperature and humidity among traditional underground and modern house in Gharyan, Libya

Modern buildings are associated with a lot of shortcomings, such as consumption of an excessive amount of non-renewable energy and resources, environmental pollution and depletion of natural landscapes, etc. Vernacular buildings can be argued to help in reducing environmental problems for local society. Libya, as a developing Arab country, has also faced several urbanization problems in recent years. However, the country has a remarkable span of vernacular architecture patterns. Vernacular architecture that the country owns may be a solution to combat such challenges. There are three types of traditional vernacular dwellings in three regions of the country as underground housing (the mountain region), compact dwelling (the desert), and the courtyard house (coastal region). Thus the aim of this study is to make a comparison between underground and modern housing in Gharyan, Libya, with regards to thermal performance and humidity. Thermal performance in both underground and above ground houses was measured with an instrument called a hygrometer. The result from the thermal measurement that was done in one month of the winter season (21/01/2019-18/02/2019) demonstrates that the underground house has an indoor mean temperature and humidity of 16.12°C and % 62.07 RH while the other house type has an indoor temperature and humidity of 12.70°C and % 70.13 RH. The underground house seems to have a relatively reasonable and stable indoor temperature compared to the modern house indoor. In addition, the underground house seems to be relatively less humid compared to the modern house for indoor environment in particular.

Development of a stable inorganic phase change material for thermal energy storage in buildings

Building energy consumption is influenced evidently by solar radiation. To achieve a stable indoor temperature by minimizing the heat fluctuations resulted from solar radiation, latent heat thermal energy storage systems with phase change materials (PCMs) in building envelope have been studied. Though inorganic PCMs have promising potential applications among all kinds of PCMs, the supercooling and segregation are the major issues which have restricted their practical applications. The purpose of this study is to lessen the supercooling degree of an industrial grade PCM (CaCl2·6H2O) by using a nucleating agent - flake graphite. A super absorbent polymer (SAP) was also used as a thickener to prevent segregation of CaCl2·6H2O during phase transition. The combined method of thermogravimetric analysis/differential thermal analysis (TGA-DTA) was firstly proposed to evaluate the segregation of inorganic PCM innovatively. The results showed that using 0.5 wt% flake graphite not only eliminated the supercooling of CaCl2·6H2O, but also improved its thermal conductivity for better thermal performance. The results of Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) demonstrated that the flake graphite did play an important role on the crystallization of CaCl2·6H2O. Numerical simulation demonstrated that using modified CaCl2·6H2O within walls of buildings in Hong Kong and Changsha are economically feasible with the payback periods of 18.3 years and 8.4 years respectively.

Experimental research on the dynamic control scheme of a heating system based on integrated meteorological parameters

A good heating regulation should be able to maintain relatively stable indoor temperature. Hence, the dynamic control scheme of a heating system should be formulated considering outdoor temperature, solar radiation, wind speed and direction, and other meteorological factors, rather than just the outdoor temperature. A dynamic control strategy of a heating system based on an integrated meteorological parameter is proposed, which converts several parameters into one using the equivalent influence method. An analysis of the thermal dynamic characteristics of both the building envelope and the heating system established a complete feedforward control scheme. A residential community in north China was selected to conduct operation data monitoring using the aforementioned model. Results showed that the new control scheme could effectively stabilize indoor temperature. The variance of the indoor temperature was 0.48 using the traditional method, and that of the test object was 0.31 after adopting the proposed model.

Contribution to the Study of the Energy Needs for a Building in the City of Errachidia Influence of Orientation and Local Materials

Given the share of buildings in energy demand, improving the energy efficiency of buildings in Morocco is an important source of energy savings. In order to finally get surplus energy balance buildings to maintain a stable indoor temperature, this work investigated the influence of orientation and local building materials with and without insulation on energy needs of a building in the city of Errachidia using theECOTECT ANALYSIS 2011software dedicated to the Thermal Simulation of Buildings.

Determination of Moisture Buffering Capabilities of Common Furniture Materials

According to previous existing studies, the building materials can have a high impact on relative humidity fluctuations in a room by adsorption/desorption processes. The aim of this paper is focused to determine the influence of commonly used furniture materials to indoor air relative humidity. The measurements were performed in a controlled environment of the climatic chamber. During the measurements, a stable indoor temperature together with a constant air moistening was ensured. The indoor air parameters were measured with data loggers as well as the periodical weighting of materials was performed, to determine the moisture content of materials. The results showed that the common furniture materials have a very significant impact on indoor air relative humidity. The calculations of the influence were performed according to the mass balance equation comparing the predicted results without considering the influence of materials to the actual measured results from real case studies, therefore estimating the adsorption capabilities of these materials. The influence of these materials to the stabilization of indoor relative humidity can be expressed as a coefficient in mass balance equation depending on the type of material, area, and thickness of material, initial moisture content, and indoor air parameters. The findings of these results can be used in the design stage of indoor climatic systems to more precisely predict the relative humidity.

A proportional–integral (PI) law based variable speed technology for temperature control in indirect evaporative cooling system

The operation of indirect evaporative cooler (IEC) largely depends on the ambient temperature and humidity. To maintain stable indoor temperature, proper controller is essential. On-off control is a mature and stable control method used on constant speed fans. However, large fluctuation of indoor temperature can be observed because of limited control precision. To achieve better thermal comfort, a proportional–integral (PI) law based variable speed technology is proposed for accurate temperature control in an IEC system. This technology had been proved highly effective in central air-conditioning systems and direct expansion air-conditioners in terms of control precision and energy saving, but its techno-economic feasibility in IEC has not been investigated. In this study, annual dynamic simulation has been conducted to an IEC system based on the IEC model and control algorithm. Results show that indoor temperature can be controlled within ±0.5 °C around the setting point for 81.9% of time, while it is only 30.5% under on-off control. The PI based controller is well adapted to cooling loads in all seasons with good control precision, fast response speed and small overshoots. Response time of PI control is only 10 min in a disturbance rejection test, which is much shorter than 30 min under the on-off control. Annually, IEC with variable speed fans consume 50.0% less energy than that of on-off fans. At last, economic analysis shows that this technology is economically feasible only when the power of primary air fan is larger than 1.75 kW.

Study on the energy performance enhancement of a new PCMs integrated hybrid system with the active cooling and hybrid ventilations

A new hybrid system for the energy cascade utilization has been proposed, integrating the hybrid ventilations, the active PV cooling, the radiative cooling together with the PCMs’ storages. A mathematical modelling together with systematic energy performance evaluation criteria has been presented to disclose the heat transfer mechanism of the hybrid system involved with different energy forms, diversified energy conversions and thermal energy storages. Multivariable parametrical analysis has been conducted and technical solutions were thereafter proposed in terms of maximizing the energy performance with the robust design and operating parameters. From our results, the interior radiant cooling system results in a stable indoor temperature with considerable energy saving potentials. The new hybrid system shows an overwhelming energy performance over the traditional system. Moreover, the polynominal fitting method is more accurate and robust than the traditional linear fitting method in terms of acquiring critical knowledge about the design and operating parameters. Research results for different scenarios with different geometrical and operational parameters have been presented to demonstrate and verify the effectiveness of the proposed technique.

Development and optimization of a novel controller for regenerative indirect evaporative cooler

Abstract The main characteristic of an indirect evaporative cooler (IEC) is the high dependency on ambient air conditions. To ensure stable indoor temperature and provide better thermal comfort, proper control strategy is essential. However, very limited studies report the controller used in IEC. In this paper, a novel control scheme named high-low (H-L) is proposed for regenerative indirect evaporative cooler (RIEC). Under H-L control scheme, the fans would be switched between high speed and low speed rather than completely turned off. The H-L control adopts the multi-speed technology, providing energy saving potential compared with conventional on-off control and overcome the complexity and costly of variable speed technology. The annual performance of RIEC was simulated under H-L control based on the RIEC model and dynamic indoor heat and mass balance model. The influence of low speed to high speed ratio (L/H) is discussed in order to propose an optimal L/H by considering both the thermal comfort and annual energy consumption. The results show that the H-L control can provide stable indoor temperature and satisfactory thermal comfort with Predicted Mean Vote (PMV) in the range of -0.5 to 0.5 for 76.2% of time. The optimal L/H is found to be 0.25 to 0.33 because of high thermal comfort provided and lowest energy consumption.

Melamine foam impregnated with paraffin as thermal regulation materials for obtaining stable indoor temperature

Developing thermal regulation materials is essentially important for constructing energy conservation buildings. We here developed novel multifunctional composite foams with thermal regulation ability by impregnating phase change paraffin into the interconnective pores of melamine foam (MF), followed by coating a thermal insulation layer comprised of SiO2 nanoparticles (SiO2NPs). The endothermic and exothermic enthalpies of the as-prepared paraffin@MF@SiO2NPs were 179.9 and 169.5 J g−1, respectively, which was capable of absorbing and releasing latent heat via phase transition. The SiO2NPs insulation layer was able to suppress the heat transfer from outdoor environment to the foam and also prevented a direct heat exchange between foam and the indoor environment. As a consequence, the paraffin@MF@SiO2NPs exhibited excellent thermal regulation capability to maintain stable indoor temperature. Moreover, the paraffin@MF@SiO2NPs was lightweight (0.796 g cm−3), which can be tailored into diverse shapes and assembled together according to the design need. Our strategy demonstrated here might be extended for developing new type of thermal regulation materials that have great potential application in constructing energy conservation buildings.