Building Thermal Loads Research Articles

Application of the Clustering Method to the Determination of Typical Days of Thermal Loads of Buildings in Uzbekistan

Application of the Clustering Method to the Determination of Typical Days of Thermal Loads of Buildings in Uzbekistan

Investigation of annual performance of a building shaded by rooftop PV panels in different climate zones of India

Photovoltaics panels are generally used on rooftop for electricity generation. However, installation of PV on the rooftop also has potential impact on the heating and cooling load of the building. This work studied these indirect benefits of rooftop PV panels by conducting experiments in Raipur, India, and compared the results with the exposed roof. Further, mathematical model is presented to analyze the annual effect of PV shading in terms of thermal load saving and power generation. Annual variation of cooling/heating load, PV power generation and overall energy-saving efficiency index is presented for different climatic zones of India. Average annual reduction in the roof and ceiling temperatures for different cities are in the range 6.05–10.96 °C and 3.94–7.15 °C, respectively. Annual cooling load reduced by 70.33–94.37%. Although PV panels shading shows negative impact during the winter season by increasing the heating load of building in all the climatic zones, the overall thermal load of building may reduce up to 22.76–74.07%. Furthermore, the overall energy-saving efficiency index varies from 21.27 to 25.12%, with maximum efficiency observed for Jodhpur city followed by Raipur. Overall, this study highlights the potential of rooftop PV application in buildings under different climatic zones of India.

Experimental evaluation of the cooling performance of radiant ceiling panels with thermal energy storage

Demand-side management (DSM) strategies in buildings generally rely on short-term heat storage in structural thermal mass. However, the thermal storage capacity is limited by the available thermal mass as buildings are increasingly built using lightweight technologies. In addition, the structural thermal mass generally has a low heat storage and release rate, limiting the ability to manage building thermal loads. To overcome these limitations, we propose an innovative, flexible cooling system that can be installed in office buildings to replace conventional all-air systems. The system utilizes the high thermal energy storage capacity of macro-encapsulated phase change materials (PCM) discreetly incorporated below the serpentine copper coil of standard radiant ceiling panels (RCP). A walk-in dual climate chamber was used to evaluate experimentally the ability of the RCP-PCM system to shift cooling loads to off-peak hours. In addition, the heat removal capacity rate and the resulting indoor thermal environment improvements are assessed. The measured passive cooling power ranged between 11 W/m2 and 31.4 W/m2, with an average of around 17.3 W/m2. Results indicate that the RCP-PCM system can shift the cooling loads to off-peak hours while maintaining acceptable thermal comfort conditions during work hours (8:00 to 18:00). During the testing period, the system was able to passively absorb heat gains between 180 and 230 Wh/m2 during the day and operate actively only at night during unoccupied periods. This load-shifting capability of the RCP-PCM system can be of great help in planning DSM strategies for increased penetration of renewable electricity in building cooling applications.

Thermal design of energy piles for a hotel building in subtropical climate: a case study in São Paulo, Brazil

The use of shallow geothermal energy through energy piles for the air-conditioning of buildings is increasing worldwide. This type of renewable energy technology is still not utilized in Brazil, where the hot dominating weather regions and the air cooling demand predominate. In this case of unbalanced heat transfer to the ground, the efficiency of the system may decrease with time due to the excessive heat injection into the soil. In order to investigate the possibility of an efficient application of this technology in São Paulo city, a balanced use of the ground for a ground-source heat pump (GSHP) system utilizing energy piles is evaluated in the present paper. Energy foundations were designed to meet the balanced heating and cooling loads (air conditioning and water heating) of a hypothetical business hotel building located in a site at the campus of the University of São Paulo, where thermal response tests (TRTs) were conducted on different types of energy pile. The number of energy piles required to supply the building thermal loads were estimated using the pile heat exchanger modelling software PILESIM 2.1 and compared with an analytical model prediction. The evaluations were done for three different types of pile tested at the site chosen for this study: micropiles, steel pipe, and continuous flight auger (CFA) piles. The results indicate that the ground heat extraction should be considered for the use of GSHP systems with energy piles in air cooling-dominated scenarios similar to the case studied here.

Experimental investigation of an integrated absorption- solid desiccant air conditioning system

Separate handling of sensible and latent components of building loads can be an energy efficient approach compared to simultaneous management of both. This paper presents a detailed experimental analysis of an energy efficient air conditioning system using solid desiccant integrated with absorption system for separate building thermal load handling. The experimental system consists of silica-gel based solid desiccant for latent load handling, whereas the gas fired air-cooled NH3-H2O absorption chiller is used to handle sensible load of the space. A chilled water-cooling coil heat exchanger is installed on the process side of desiccant cooling system to integrate it with the absorption chiller. The performance of integrated absorption- solid desiccant system is compared with a standalone conventional desiccant air conditioning system with a direct evaporative cooler considering it as baseline system under wide range of operating conditions including air temperature, air humidity, and regeneration temperature. The comparative analysis is performed in terms of supply air temperature, cooling capacity, and coefficient of performance. The experimental results exhibit that supply air temperature of the integrated system is 15.2 °C compared to 24.6 °C achieved by conventional desiccant system. Moreover, COPth of the integrated system is also 50–55% higher than its counterpart and it is almost comparable with double-effect absorption chiller. It is concluded that the integrated system using separate load management approach is more efficient for HVAC applications.

Thermal and energy performance of a user-responsive microalgae bioreactive façade for climate adaptability

As a recent trend in the energy-efficient architecture, microalgae bio-reactive façades can control buildings’ thermal loads by the responsiveness to solar radiations and adaptive variations in culture density. Although these smart systems can provide adaptable shading during the year, they cannot meet the varying thermal comfort needs of building users in a short time because the microalgae medium’s culture remains almost unchanged during the day. This paper reports on an innovative method that helps microalgae bioreactive façade respond to solar radiation and users’ thermal needs in a short time. To achieve it, a smart window panel will be introduced, which contains two remotely-controlled adjustable bioreactors which can regulate the algae medium in height based on the users’ thermal needs. This novel panel can serve as a bio-adaptable sunshade integrated with the building facade. Thus, the internal building thermal loads can be adjusted via the height of the bioreactor façade. Experimental and simulation research was conducted to compare the thermal performance of bioreactor facades at different microalgae medium height levels in the BSk climate zone. The results indicate that indoor and outdoor temperature differences for full, ¾, ½, and ¼ medium height level every 15-minute time interval are 12.55, 11.50, 10.87, and 6.53, respectively, indicating that the full-height level has the most influence to control the thermal load of the system. According to the results, the bioreactor façade with adjustable medium height greatly impacts building thermal control in a short time.

Evaluation of Tio2 and CaC03 in fiber cement roof tiles for reducing the thermal load buildings

In this research, different materials are evaluated to improve reflectivity and reduce the thermal load generated by solar irradiation in buildings that use fiber cement tiles. This study aims to find commercial materials that are affordable and of low weight per area so that the general community can obtain favorable results in reducing the thermal load in buildings. This study uses materials based on solutions of white enamel and titanium dioxide (Tio2), with different concentrations of TiO2 and calcium carbonate, dispersed on corrugated sheets of fiber cement roofing. In them, the range of variation and the temperature profile of the surface (internal and external) are evaluated as a function of the concentration of the mixture, the margin of experimental performance, the weight per unit area and the results are compared between sheets, with and without the new coating solution. The sheet that presented the best performance was the one that had in its mixture a composition by weight of 75.29% white enamel and 24.71% titanium dioxide. This can reduce the average temperature on the external surface up to 9.5°C in the same buildings in approximately and 3.85°C on the surface of the side that does not have the mixture. In general, the performance of the solutions is sensitive to the manufacturing process and materials (centrifuge of the mixture, the amount of calcium cobalt, the amount of titanium dioxide and the total dispersion of the mixture on the surface of the tiles roof fiber cement).

A model and data hybrid driven approach for quantifying the meteorology-dependent demand flexibility of building thermal loads

A model and data hybrid driven approach for quantifying the meteorology-dependent demand flexibility of building thermal loads

GIS-BASED THERMAL LOAD ESTIMATION OF BUILDINGS IN THE NATIONAL SCIENCE COMPLEX, UP DILIMAN

Abstract. Building thermal load is the energy exhausted to maintain a specific indoor temperature in comparison to the outdoor temperature. Majority of this energy makes use of a considerable amount of fossil fuels which contributes to greenhouse gases emission leading to global warming. Thermal load estimation of buildings allows people to identify infrastructures in need for retrofit for a more sustainable and smart urban management. This paper presents a small-scale study to estimate the thermal cooling load of fourteen (14) buildings in the National Science Complex of the University of the Philippines Diliman. Results of the annual cooling load calculation for the year 2020 was reported with an estimated lowest cooling load of 1,618 kW for the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) observatory and the highest cooling load of 13,484 kW for the Institute of Mathematics. The values calculated was an overestimation as the entire building was set up as a homogenous cold room without any windows or doors. For future work, it is recommended that input data be supplemented with digital surface model (DSM) and triangulated irregular network (TIN) raster data derived from Light Detection and Ranging (LiDAR) to not only categorize but assign specific values over each building group of the study area.

VEGETATION INSULATION SCREEN AS A PASSIVE COOLING SYSTEM IN HOT HUMID CLIMATE: HEAT AND MASS EXCHANGES

Planted roofs are passive cooling techniques that reduce the thermal load of buildings. In this paper, a Dynamic mathematical model based ontime average Navier-Stokes equationsfor a plantedroof in hothumidclimates has beendeveloped for evaluating the cooling potential.Transfer equations are solved using a finite difference scheme and Thomas algorithm. The model was applied for the simulation of a planted roof in Togolese climate conditions. Results showed that, evapotranspiration and Solar Heat gain Factor are functions of the Leaf Area Index LAI which is the most important parameter when considering the foliage material. For LAI equal to 6, latent heat peak value reaches 900 W.m-2while that of sensible heat is around 350 W.m-2. Solar heat gain factor can bereducedto 15% fortheplantedroofagainst 45% forbareroof. It is clearly proved that the foliage density and hence the vegetation canopy type selection greatly influence the thermal efficiency of the bioclimatic insulation screen. A larger Leaf Area Index reduces the solar flux penetration and increases evapotranspiration which is an important parameter when considering surrounding microclimate formation.

Influence of the moisture driving force of moisture adsorption and desorption on indoor hygrothermal environment and building thermal load

To more accurately evaluate the indoor hygrothermal environment of a building, control the indoor temperature and humidity, evaluate the thermal comfort of occupants, and select the capacity of the heating, ventilation, and air conditioning (HVAC) system, moisture transfer from and into architectural materials should be considered. However, the most widely used commercialized software ignores the moisture effect from envelopes or adopts a simplified model based on the difference in humidity ratios between hygroscopic materials and interior zone air. In this study, the effects of the driving forces of hygrothermal models were identified and quantified. The calculated results show that the indoor humidity changes differed when the moisture effect by moisture adsorption and desorption was considered in the models. Because the simplified effective moisture penetration depth (EMPD) model uses differences in the humidity ratio as a driving force, the calculated results of the indoor humidity ratio exhibit relatively constant tendencies. However, the thermodynamic chemical potential model corresponds to a detailed heat, air, and moisture transfer (HAM) model that uses the water potential as a driving force; this model can consider the moisture effect based on temperature and humidity changes. Therefore, the humidity ratios calculated using the detailed thermodynamic HAM model show differences of 0.01%–38.78%, and the difference in relative humidity between building materials and indoor air becomes smaller; these results are comparable to those of the simplified model. Finally, the adoption of a simplified model can result in differences in the sensible heat load of 4.4%–13.8% and latent heat load of 16.1%–51.2%. Thus, this study confirmed that a coupled HAM model, which uses the water potential as a driving force, can be employed to accurately simulate the hygrothermal behavior of building envelopes.

Thermal performance evaluation of integrated solar-geothermal system; a semi-conjugate reduced order numerical model

In cold climates, a borehole thermal storage system is key to supplying renewable energy year-round for heating applications. For such systems, coaxial borehole heat exchangers are getting more attention in recent years due to their superiority over other types of borehole heat exchangers. As such, more research is needed to understand the heat transfer mechanism and enhance the heat transfer process. In this study, an efficient reduced-order numerical code is developed to solve the heat transfer phenomenon in the coaxial borehole heat exchanger system for application in solar borehole thermal energy storage system. This concept assists in transferring heat between the subsurface and the Heat Transfer Fluid. In addition, the numerical solution integrates the building thermal load, thermal energy originated from the solar collector system, and heat loss to the adjacent strata and atmosphere. The developed numerical model is validated against the field-test experimental data performed with a coaxial borehole heat exchanger. The accuracy and computational speed of the model are compared its corresponding three-dimensional full-scale finite volume based model. Finally, the verified numerical code is employed to estimate the efficiency of solar-borehole thermal energy storage system for a two multi-family residential building in Ontario, Canada. The proposed model offers a novel holistic approach for estimation of the solar heat collection, geothermal heat storage/extraction, and heat loss phenomenon in a solar-BTES system accurately and efficiently. Moreover, it can serve as the basis to design solar-borehole energy storage systems of any size and at any location.

Sustainable Energy Solutions for Thermal Load in Buildings—Role of Heat Pumps, Solar Thermal, and Hydrogen-Based Cogeneration Systems

Abstract Economic and population growth is leading to increased energy demand across all sectors—buildings, transportation, and industry. Adoption of new energy consumers such as electric vehicles could further increase this growth. Sensible utilization of clean renewable energy resources is necessary to sustain this growth. Thermal needs in a building pose a significant challenge to the energy infrastructure. Potential technological solutions to address growing energy demand while simultaneously lowering the carbon footprint and enhancing the grid flexibility are presented in this study. Performance assessment of heat pumps, solar thermal collectors, nonfossil fuel-based cogeneration systems, and their hybrid configurations is reported in this study. The impact of design configuration, coefficient of performance (COP), electric grid’s primary energy efficiency on the key attributes of total carbon footprint, life cycle costs, operational energy savings, and site-specific primary energy efficiency are analyzed and discussed in detail. Heat pumps and hydrogen-fueled solid oxide fuel cells (SOFCs) are highly effective building energy resources compared to traditional approaches; however, the carbon intensity of electrical energy and hydrogen production are keys to the overall environmental benefit.

Controlling a large constant speed centrifugal chiller to provide grid frequency regulation: A validation based on onsite tests

High penetration of intermittent renewables may cause safety and stability problems to the electricity grid. Building thermal loads could contribute to the grid stability in the era of renewable energy and smart grid, because they are high and flexible. This study proposes a model predictive control strategy to control a large constant speed centrifugal chiller to follow grid frequency regulation signals while providing sufficient cooling to the building. Onsite tests were conducted to identify critical parameters in the process including time delay and ramping speed of chiller power consumption. A dynamic platform was built based on the studied system and fine-tuned using onsite tests data. Validation tests were conducted using the 40 min Regulation A and Regulation D test signals provided by PJM (Pennsylvania - New Jersey - Maryland Interconnection). According to the onsite tests, the total delay time and the maximum ramping speed of chiller power were 20–25 s and 2.53 kW/s, respectively. Validation based on the 40 min test signals shown that the composite performance scores were 0.901 and 0.885 for Regulation A test and Regulation D test, respectively. Continuous 12 h validation tests in a working day shown that the composite scores were 0.917 and 0.893 for Reg A and Reg D tests, respectively. And the studied constant speed centrifugal chiller could provide a regulation capacity of 5–7.5% of its nominal power.

A clustering-based climatic zoning method for office buildings in China

Since the influence of building types has not taken into consideration, the current climatic zoning scheme of China may not fully reveal the real energy requirements, especially the annual energy consumption variation of different types of buildings. This study proposes a novel zoning method based on the clustering of building thermal load data of a typical office building. Thermal load simulations were performed under 274 cities’ meteorological conditions across China. Two widely used clustering algorithms: K-Means and Agglomerative Hierarchical Clustering were adopted and compared. Based on the inter-city clustering results, a new zoning map with five distinct zones for building thermal design was developed. To demonstrate the thermal load patterns, especially its dynamic characteristics, three representative cities from the three most densely populated zones were selected for intra-city clustering. The results demonstrate that K-Means method performed better in building thermal design zoning and thermal load pattern analysis, and the optimal thermal zone number is 5. The present zoning method could be applied to other building types and promotes an improvement of the existing zoning strategy. It benefits not only architects, but also building operators and policy makers for energy efficiency design and even green urban design.

Optimal Building Thermal Load Scheduling for Simultaneous Participation in Energy and Frequency Regulation Markets

This paper presents an optimal scheduling solution for building thermal loads that simultaneously participate in the wholesale energy and frequency regulation markets. The solution combines (1) a lower-level regulation capacity reset strategy that identifies the available regulation capacity for each hour, and (2) an upper-level zone temperature scheduling algorithm to find the optimal load trajectory with a minimum net electricity cost. In the supervisory scheduling strategy, piece-wise linear approximations of representative air-conditioning equipment behaviors, derived from an offline analysis of the capacity reset mechanism, are used to predict the cooling power and regulation capacity; and a mixed-integer convex program is formulated and solved to determine the optimal control actions. In order to evaluate the performance of the developed control solution, two baseline strategies are considered, one with a conventional night setup/back control and the other utilizing an optimization procedure for minimizing the energy cost only. Five-day simulation tests were carried out for the various control strategies. Compared to the baseline night setup/back strategy, the energy-priority controller led to a 26% lower regulation credit and consequentially caused a net cost increase of 2%; the proposed bi-market control solution was able to increase the regulation credit by 118% and reduce the net electricity cost by 14%.

Study on the influence of key parameters of exterior window structure on building energy saving effect

On account of the problem which was related to the negative effect of exterior windows energy saving in current residence building, we constructed a single energy-saving building with same structure and different exterior windows. Meanwhile, taking indoor temperature field and building energy consumption as entry points, the key parameters of the energy saving effect of the exterior window were compared and analyzed to study the indoor temperature field and the building thermal load and cooling load in the heating, cooling and transition season of energy-saving buildings which had exterior window structures (standard external windows, blue heat-absorbing glass windows, thermal reflection glass with high light transmission, ordinary hollow glass windows, low-E insulating glazing units, low-E high through glass windows, ordinary 3mm glass windows) with different window frames under the same climate environment. In addition, the grey theory and regression analysis were used to get the correlation degree and matrix equation between the energy-saving effect (the indoor temperature in heating season, the indoor temperature in refrigeration season, the indoor temperature in transition season, the annual cumulative heat load index, the annual cumulative cooling load index, the heating season heat load index, the air-conditioning season cooling load index) and key parameters (the glass thickness, the air layer thickness, the glass layer number, the heat transfer coefficient, the solar heat gain coefficient, the shading coefficient, the solar transmittance, the solar reflectance, the visible light transmittance, the visible light reflectance) in energy-saving buildings.

A regression-based framework to examine thermal loads of buildings

Abstract Building facades play an important role in thermal loads, which act as an isolation barrier to ensure thermal comfort to the occupants. Depending on the properties of the building material adopted, each component of a building facade may lose or gain heat, contributing to the building’s thermal load. There is a growing need to examine the role that external construction components play from an energy perspective towards achieving environmental comfort in buildings. The novelty of this research is to propose a methodological framework based on Design of Experiments (DOE) that characterizes the thermal loads that are directly caused by variables controlled by building designers and consultants. Such variables include external construction components (walls and openings assessed via window-to-wall ratio), air infiltration rate, artificial lighting, occupation levels, heating, and cooling equipment, and appliances during the operation phase of a building, taking into consideration the local climate data in which the building is located. This work validates the proposed method with a case study of a single-family house, which provides a better understanding of the influence and interactions of design factors on building thermal loads. Results reveal that the window-to-wall ratio has a major influence on evaluating the thermal loads in buildings. The higher the ratio, the higher the value of the thermal loads. The proposed framework aids designers in determining the components that are influencing thermal loads in buildings, as well as the required window-to-wall ratio. Findings highlight that construction components of external walls and openings are responsible for around 93.9–97.58% of thermal loads in buildings. Furthermore, this work presents the important role of sustainable building decisions at an early stage of designing construction projects.

Theoretical Minimum Thermal Load in Buildings

Summary Building cooling and heating accounts for a large portion of total global energy use and requires commensurate amounts of resources, which contribute significantly to global warming. Traditionally, addressing this issue has meant improving the efficiency of equipment supplying the thermal energy, reducing envelope heat transfer, and reducing air infiltration. However, this approach is already reaching practical limits. In this perspective, we explore (1) how to reduce thermal load in buildings theoretically and (2) how to achieve that reduction and dramatically lower the energy required to support building loads practically. First, we discuss our framework developed for calculating the theoretical minimum thermal load (TMTL) in buildings. Our analysis shows that current thermal loads in buildings are more than an order of magnitude higher than the TMTL. We also introduce an approximate formula to calculate energy savings from zonal control of thermal load, which shows that the majority of zonal control benefits can be achieved with fewer than 10 zones. Then, we discuss pros and cons of various approaches and strategies to achieve the TMTL. We conclude our perspective with some longer-term R&D ideas, such as thermally adaptive clothing and thermal storage to help approach the TMTL, while providing the additional benefit of interacting with the renewable grid of the future.

Performance Comparison for Building Thermal Load Prediction of Office Buildings Using Machine Learning Methods

Performance Comparison for Building Thermal Load Prediction of Office Buildings Using Machine Learning Methods