Annual Thermal Load Research Articles

Relationship between construction parameters and thermal loads in a building without internal gains

The analysis of building characteristics indicates that there are some uncertainties influencing its energy performance: Environment, volumetry or operating conditions. It is important to have a low-cost system that performs this analysis and energy management by optimizing the coupling between production and consumption. Knowing the relationship between the annual thermal needs with different construction parameters can help to define this system and allow understanding the expected heating and cooling consumption based on easily available information. In this work, a numerical methodology has been applied to estimate the thermal loads of a building without internal gains. For this purpose, a simulation environment has been developed to execute a sensitivity analysis through the interconnection between TRNSYS 16.1 and GenOpt programs. Volumetry, building materials according to Spanish regulations and percentage of external windows are evaluated as analysis variables of the parametric study. Heating, and cooling loads have been calculated to quantify their influence: Older regulations imply higher annual loads; the increase in building height and area reduces the annual thermal loads and higher percentages of glazing on the external façades imply higher annual demands, particularly in the east and west orientations; the variation of the envelope results in the most influential factor. Finally, a statistical study has been performed to assess the annual trends: Heating trends point to more stability with two defined intervals, while cooling trends are more asymmetric.

Residential demand-side management using integrated solar-powered heat pump and thermal storage

Due to the mismatch between rooftop solar energy generation and residential electrical demand, considerable solar energy is exported into electricity networks causing a range of issues such as voltage instability and connection overload. To address these problems, we propose and analyse a residential hot water, heating and cooling system, which features a heat pump combined with thermal energy storage to align peak thermal loads with output from a rooftop solar system. This work quantifies the impacts of thermal storage on residential space-conditioning peak load reduction. Annual hourly thermal and domestic hot water loads were determined for a representative Australian house, located in Brisbane, using building energy simulation software and verified using measured data. Combined with the measured sub-metered electrical loads of other electrical appliances, this data was used to simulate the solar system export, heat pump demand, and thermal storage system performance. Results show that by combining a 5-kW solar system, the proposed system can reduce annual grid-electricity demand by approximately 76% compared with a conventional non-thermal storage system. Peak electrical load was also observed to undergo a temporal shift and reduce by approximately 45%. Furthermore, the solar fraction for air-conditioning and domestic hot water loads reached 84%, while solar self-consumption increased to about 56%. This study demonstrates that the proposed system is an effective means of managing electricity demand, shifting peak load and improving solar utilization, thus relieving stress on electricity networks from high penetration of solar photovoltaics.

Study on the Passive Heating System of a Heated Cooking Wall in Dwellings: A Case Study of Traditional Dwellings in Southern Shaanxi, China.

In China, research on winter heating and energy saving for residential buildings mainly focuses on urban residences rather than rural ones. According to the 2018 China Building Energy Consumption Research Report, rural residential buildings emit about 423 million tons of carbon, accounting for 21% of the country’s total carbon emissions. According to the research on China’s greenhouse gas inventory, the main sources of carbon emissions in rural areas are from cooking and the burning of fuelwood and biomass for heating in winter. In this study, the southern Shaanxi area, which is hot in summer and cold in winter, was selected as the research site, and a fire wall system was planned that combines cooking and heating facilities in residential buildings. The system uses the heat generated by cooking and the heat storage capacity of the wall, as well as the principle of thermal radiation and heat convection, to increase the indoor temperature. The advantage is that the hot air generated is mainly concentrated in the inside of the wall, which reduces the direct contact with the cold outdoor air and avoids excess heat loss. In this study, in addition to considering the influence of the cooking fire wall system on the indoor temperature, the difference in the outer wall with or without solar thermal radiation was also considered. The research results show that the use of a cooking fire wall heating system reduces the annual heat load of the building to 440.8318 KW·h, which is a reduction rate of 7.91%. When there is solar radiation on the outer wall, the annual thermal load of the building is reduced by 1104.723 kW·h, and the reduction rate is 19.84%.

Experimental and numerical investigation of eco-friendly materials for building envelope

ABSTRACT This work aims to evaluate the impact of new materials on thermal performance and energy savings. Indeed, this study shows the importance of the use of natural and recycled waste-based feather materials. For this purpose, a full-scale cell located in Casablanca was considered as a case study to build a simulation model performed on TRNSYS. This model is then used for the impact of the techniques studied on energy performance, GHG emissions, and hours of discomfort inside another cell in Casablanca. This study showed that the developed nonwovens exhibit excellent insulation performance with thermal conductivity in the range of 0.031–0.044 [W/m. K]. Moreover, the minimum energy performance is observed for developed wool insulation with a performance of 30 (KWh/year.m2). The comparison of these values with the Moroccan thermal regulation which sets a threshold of 40 (kWh/year.m2) for the annual thermal load of residential buildings in the climatic zone of Casablanca, shows that the feather waste insulation integrated into the building is mainly sufficient to meet the requirements of Moroccan regulations. Annual GHG emissions are mitigated by 44.61 for FC1, 46.54 for FC2, 47.95 for FC3, 46.59 for FW1, 46.99 for FW2 and 48.58 for FW3(%).

Annual energy simulation for the air conditioning of Fuxing high speed trains

China ranks first in the world both for the operating mileage of high-speed railways and the quantity of high-speed trains. The energy consumption of air conditioning ranks second for the sub-systems of high-speed trains. In this paper, a simulation model is created to calculate annual thermal load and electricity consumption hour by hour for Fuxing high-speed train in Harbin, Beijing, Shanghai and Guangzhou. The simulation is validated in climate laboratory and shows 1.3%–13.2% deviation compared with the test results in different external temperatures. The simulation results show that the annual electricity consumption for a coach, the whole fleets of Fuxing trains and all high-speed trains in China are estimated as 60,050 kWh, 286.2 M kWh and 1.71G kWh respectively. Through analyzing the thermal load, electricity consumption and energy efficiency, six technical means are proposed to be implemented in the air conditioning of Fuxing trains considering both for energy saving and hygrothermal comfort. Heat pump and decreasing the inside setting temperature are the two methods to reduce the consumption in heating, and their saving will be 15.1% and 7.8% respectively. Replacing hot gas bypass by parallel compressors, removing reheating and reducing air flow of CFs in part-load are the three suggestions in cooling with saving of 9.6%, 4.9% and 5.4% respectively. Changing alternating current fans to electronically commutated fans will be one rich oil deposit where energy can be dug in all the working hours, and it will save 4.8% of total energy. Meanwhile, 131.0 M kWh and 781.8 M kWh (45.8%) electricity will be saved for Fuxing trains and all the high-speed trains in China respectively if all the six technical means can be implemented into the air conditioning system.

A dish-stirling solar concentrator coupled to a seasonal thermal energy storage system in the southern mediterranean basin: A cogenerative layout hypothesis

In the future, renewable energy sources will increasingly represent an efficient energy source capable of meeting the demands of residential and industrial buildings avoiding the emissions of greenhouse gases into the atmosphere. In this paper, a heat and electric power cogeneration plant implementing a field of dish-Stirling collectors, a seasonal geothermal storage and a system of water-to-water heat pumps is proposed for the first time. The cogeneration plant has been designed both to supply thermal energy to the heating system of Building 9 of the Department of Engineering in Palermo and to produce electricity. The operation of the plant has been tested by means of hourly-based numerical simulations that have been carried out using a numerical model implemented with Transient System Simulation Tool. The experimental data of a pilot dish-Stirling collector, located in the same area, has been used to carefully calibrate the numerical model. Using energy and economic performance indicators, it was possible to select the best configurations among 1440 analysed cases. Results of simulations show that with the best plant configuration, it is possible to cover 97% of the building's annual thermal loads with energy produced by the solar system. The remaining 64% of electrical energy produced by the electric engines is free to be used for other applications. Financial analyses have shown that market penetration of this type of plant would need a strong support through incentives.

Techno-economic assessment of bifacial photovoltaic and geothermal based multigeneration system for cleaner communities

This study proposes an integrated renewable energy based multigeneration system for fresh water, heating, electricity and fuel requirements of a community with a greenhouse in Gokcebayir, Canakkale, Turkey. Solar and geothermal sources are used as renewable energy resources while sea source is employed in the desalination process to produce fresh water. The bifacial photovoltaic and hydrogen subsystems are integrated to transfer excess daytime photovoltaic electricity to hydrogen gas as an energy storage medium that is employed as hydrogen fuel for hydrogen vehicles and proton-exchange membrane fuel cell for electricity production during the lack of solar radiation. Geothermal energy system is integrated with photovoltaic subsystem and hydrogen subsystem to create more reliable energy system due to its continuous characteristic, and to provide various outputs such as heating via residential heat pump and fresh water via multi effect distillation desalination system. The bifacial photovoltaic modules are employed in two novel arrays which are the top of the greenhouse and an enhanced albedo field 1.3 MWp photovoltaic plant. The pitch distance and height determinations are made specifically for bifacial photovoltaic plant arrays in terms of solar electricity gain. The proposed bifacial photovoltaic plant is analyzed, modeled and integrated with hourly electric load, thermal load and hydrogen subsystem. The proposed system supplies electricity to a community with 150 households and a greenhouse. 1642 MWh annual electricity demand and 485 MWh annual thermal load is met at the 0.058$/kWh levelized cost of energy with 7938 kg annually produced hydrogen and 14551 kg daily fresh water. The proposed system poses 4.29% internal rate of return where 0.21% electricity could not meet due to the insufficient electricity availability especially during winter months at 39°47′N latitude, 26°15′E longitude.

Optimum design of building integrated PV module as a movable shading device

Building-integrated PV (BIPV) can be used as an external shading device as well as an electricity generator. In this study, the energy efficiency of the movable BIPV shading system installed over the windows has been investigated. In the first stage, the PV panels monthly electricity generation at different tilt angles and the building's monthly thermal load for the various overhang depth of windows were calculated. Based on the data obtained from these analyses, optimal condition for PV panel and overhang were determined for each month. In the next step, the geometry of the BIPV Panel was designed such that in each month the BIPV panel can provide obtained conditions. The movable BIPV shading was compared with the fixed modes include BIPV installed over the window with distance, BIPV installed over the window without distance, overhang, and no shading mode with fixed PV on the roof. The building annual thermal load integrated with the movable system, in comparison with four mentioned fixed modes is 12, 16, 15 and 20 % lower, and electricity generation, excessive to building thermal demand is 70, 142, 113, and 290 % higher respectively. The annual electricity generated by the movable PV is only 2 % higher than the fixed mode.

Parametric modeling and simulation of Low temperature energy storage for cold-climate multi-family residences using a geothermal heat pump system with integrated phase change material storage tank

A novel geothermal heat pump (GHP) system with an integrated low- to moderate-temperature salt hydrate phase change material (PCM) storage tank for buildings in cold climates is proposed in this study. The purpose of the PCM storage tank is to dampen peak heating loads and to remove annual ground thermal load imbalances on the ground heat exchanger (GHX) to assist in achieving an optimally-sized GHX. As heat is extracted from the closed-loop system by heat pumps in heating mode, a significant portion of this heat is used to solidify a salt hydrate PCM. This heat of fusion is later released back into the heat transfer fluid, storing it in the PCM tank and GHX for later diurnal and seasonal use. To examine the merits of the proposed concept, electric utility meter data on 15-minute time intervals were mined from an actual apartment building and used to estimate space heating, cooling, and hot water heating loads. Those data were used in an hourly, dynamic 20-year life-cycle simulation model in TRNSYS to design an optimum combination of GHX and PCM storage, where each component was sized to balance the annual ground thermal loads. The system simulation results show significant potential for GHX size reduction with a PCM storage tank, but the system is quite sensitive to the PCM melt temperature due to significant hysteretic nature of the salt hydrate PCM heating and cooling curves. We also find that there is no unique optimum unless other factors are considered such as installation cost and physical constraints; many combinations of GHX size and PCM mass are capable of achieving the design goal with similar annual electric energy consumption. For the cases examined here, a PCM melt temperature of 27 °C yields the most favorable economic results, and a preliminary economic analysis suggests that with typical drilling cost and PCM tank cost values, the GHX size can be reduced by over 50 %.

Seasonal and annual performance analysis of PCM-integrated building brick under the climatic conditions of Marmara region

In this work, thermal performance of a conventional brick incorporating phase change material (PCM) is studied. The influence of brick containing PCM on heating and cooling loads is examined considering different fusion temperatures, locations and quantities of PCM. Seasonal and annual thermal performance analysis of brick filled with PCM is evaluated and quantified for climatic conditions of Marmara region, Turkey, by an established and verified numerical model. The obtained results are compared with those of conventional brick and brick filled with phase stabilized material to identify the contribution of latent heat to energy saving. The results showed that filling the gaps of brick near the indoor ambient provides a higher energy conservation. The optimum fusion temperature of PCM varied from season to season in the range of 18–26 °C. An adverse effect of the latent heat activation was observed in summer season, causing higher cooling energy demand by an inappropriate selection of phase transition temperature. Then, an annual analysis was performed to determine the optimum melting temperature which was found to be 18 °C. By incorporating PCM to the brick, the annual thermal load decreased by 17.6%, 13.2% of which was attained due to the utilization of latent heat. The outcomes of this study suggest that the integration of PCM with optimum fusion temperature into the brick can reduce heating and cooling loads considerably in every season of the year and provide thermal comfort for the occupants.

Soil Thermal Inertia Effect on Shallow Basement Energy Performance in Different Morocco Climates

Abstract This study deals with the energy performance of a shallow basement in six climates ranging from cold to desert climate. A case study of a partially buried house located in the hot semi-arid climate of Marrakech (Morocco) is first monitored during 2 months in summer and 2 months in winter. A trnsys model of this house was built and validated against the monitoring results. Simulation results show that the annual thermal load of the partially buried house is always lower than that of the corresponding above ground building house except for the Atlantic climate. Indeed, burying the house at 1.2 m reduces its annual thermal load by 19% at least in the Mediterranean climate and by about 39% in the cold climate.

사무소 건물의 창호에너지소비효율등급제 적용성 평가

In this study, we analyzed the annual heating and cooling energy requirements of reference building with 97 certificated windows using TRNSYS 17, to review the applicability of the “Window Energy Consumption Efficiency Rating System” to the office building. The analyzed model was a medium-size office building with lightweight curtain walls and a window-to-wall ratio of 52%. The results are as follow : First, the annual total thermal load was 60,261 to 111,616 kWh and the ratio of heating load to cooling load was 1:9 showing that cooling was the main factor of the thermal load. Second, the total thermal load by SHGC showing an almost perfect linear relationship. The F-test significance probability in the regression model was 0.000 meaning statistical significance and the coefficient of determination was 0.9656 showing high correlation. In contrast, the F-test significance probability in the regression model by U-value was 0.00484 showing statistical significance but the coefficient of determination was 0.0805 showing low correlation. Third, the SHGC of window was the main factor of the total thermal load in the office building. It showed the limitation of subject in “Window Energy Consumption Efficiency Rating System” which was limited to insulation performance and airtight performance. Thus, in to evaluate the window sets in terms of energy saving, the “Window Energy Consumption Efficiency Rating System” with SHGC should be considered.

Seasonal performance evaluation of CO2 open refrigerated display cabinets

An increasing number of supermarkets and convenience stores has led to a proportionally higher demand for open refrigerated display cabinets (ORDCs). Ease of access to refrigerated products is the main advantage of ORDCs; however, they also exhibit high cumulative energy consumption as well as direct and indirect CO2 emissions. This work aims to formulate, establish, and apply a seasonal performance evaluation method for ORDCs and “walk-in” type refrigerated device driven by CO2 chillers. First, a thermodynamic modeling approach is used and fitted to experimental data. The relative error between the predicted and actual heat load is within ±10%, whereas it is within ±20% for the normalized compressor electric input. Then, an evaluation tool is constructed using the seasonal energy consumption of ORDCs commonly used in Japan and driven by a transcritical CO2-compression chiller within Japanese climatic conditions. This tool can be used to predict the annual energy demand for given ambient conditions as well as the reduced environmental impact of multiple combinations of refrigerated display cabinets compared to conventional HFC/HCFC-based systems. According to the annual temperature distribution in chosen regions, the annual thermal load, annual electricity consumption, and annual coefficient of performance are calculated and analyzed. Simulation results quantitatively evaluate the beneficial effect of Te as being translated to a better COP, and lower energy consumption and CO2 emissions. Considering the geographic location of the store, the quantitative results show how a hotter climatic condition leads to higher energy consumption and CO2 emissions, and lower COP. The proposed evaluation method is generally applicable to any regional setting and any chiller-ORDC combination.

Energy performance of mixed-mode office buildings: Assessing typical construction design practices

Studies have demonstrated the energy savings potential of mixed-mode ventilated office buildings. Yet, it is important to widen the knowledge about how those buildings have been designed and built in practice, and which design parameters have greater influence on its energy performance. The aim of this paper was to evaluate how building envelope design parameters influence the energy performance of cellular mixed-mode office buildings, in order to identify key design variables. The analysis presents a comparison among literature research studies and typical construction practices from a sample of buildings located in the city of Sao Paulo, Brazil. According to a base case model, established based on the real buildings sample, three sensitivity analysis techniques were performed to obtain relative parameter sensitivity to thermal loads: OFAT, Morris and Monte Carlo. Results showed the importance of the window opening effective area and the reduced impact of the window-to-wall ratio on the energy performance of mixed-mode office buildings. By applying a multivariate regression model, it showed significant in predicting 78.1% of the variance in annual thermal loads. The accurate determination of annual thermal loads into mixed-mode office buildings can be used to optimize the envelope characteristics based on a combination of input data and the building geometry. Findings from this study could also be applied to other locations, provided that similar climatic environment and urban context are taken into account.

Thermal performance improvement method for air-based solar heating systems

In recent years, the use of the air-based solar heating systems, which heat outdoor air and use it for heating and hot water, has increased in Japan. Air-based solar heating systems do not require special equipment for heating by direct use of air heated via convective heating, and they can be used for the hot water supply through heat exchange when the room temperature is high. However, because solar energy is only available during the daytime, and because of heat loss to the ground from the foundation concrete (which is a thermal storage body storing the collected heat), the load reduction effect is much less than the amount of the heat that is collected by solar heating. In this study, a simulation model was developed to understand the annual thermal load performance of an air-based solar heating system. The models of the solar collector, hot water tank and thermal storage were verified by comparison with experimental results. In order to improve the thermal performance of conventional systems, the solar collector, indoor air circulation, insulation under the foundation concrete, and additional thermal storage were examined. In particular, this study examined the effect of solar heat using water bottles that can achieve a large thermal storage effect at low cost. Simulation results show that the proposed system reduces annual heating and hot water load by 17.9% compared to conventional systems.

Assessment of the energy efficiency of a public university building in Southern Brazil

The adequate assessment of the thermal performance of a building requires the knowledge of its characteristics within its inserted context, making it possible to verify the actual and future performance of the building. Therefore, this study aims to analyse the energy efficiency of a public university building located in southern Brazil. The assessment was carried out according to the Brazilian Technical Regulation for Energy Efficiency Labelling of Commercial, Services and Public Buildings (RTQ-C). In this study, the building envelopment was evaluated under the actual condition and in the reference condition, using the simplified method. The constructive parameters of the building were obtained from the architectural project and technical standards, although the assigned climatic group of the building was defined based on the Brazilian bioclimatic zones. In the end, it was possible to identify the energetic efficiency level of the envelopment through the total annual thermal load of the building in its actual condition. Considering the urban and climatic context, as well as constructive characteristics of the building, strategies were proposed that can be adopted even in the project planning stage, aiming to improve the classification of the envelopment and to meet the energy efficiency policies of the country.

ファサードの高性能化手法の評価 （第3報）カラーマップによる高性能窓システムの年間熱負荷比較

ファサードの高性能化手法の評価 （第3報）カラーマップによる高性能窓システムの年間熱負荷比較

Impact of glazing type and orientation on the optimum dimension of windows for office room in hot climate

This study aims to show the impact of orientation and glazing type on optimum window size in hot climate using genetic algorithms. In winter the optimization of window size is obtained thanks to thermal gains from solar radiation, taking into account this free heat gains from the sun reduces heating demand of the building. In summer the optimization of window size is complex, in this case, the window is considered as a heat gains element. For a hot climate, the sun can be used as a passive strategy to reduce energy consumption. An optimal window size allows avoiding problems of glare and overheating. ASHRAE proposed a Window to Wall Ratio (WWR) which is considered as the optimal window size that ensures minimum annual thermal loads, this coefficient neglect different parameters such as (Glazing type, the orientation, daytime). A typical office room located in Ghardaia (South of Algeria) is selected as a case study. The results show that daylight is a key factor in limiting the window size in hot climate. The WWR cannot be considered as optimal for the whole year; this study shows that the optimal window size varies with daytime.

Comparative investigation on building energy performance of double skin façade (DSF) with interior or exterior slat blinds

Advanced passive control technologies attract a great deal of attention by architects and engineers as a way of achieving both high indoor environmental quality and energy efficient buildings. This study investigates the thermal and daylighting effects of a double skin façade (DSF) system with interior and exterior blinds. A buffer type DSF and slat type blinds are used for this comparative study. To investigate thermal and daylighting effects of three passive control models, evaluation of annual heating, cooling, and lighting loads is conducted using a widely-accepted whole building energy modeling program, EnergyPlus. A simulated DSF model is developed using the air-flow network (AFN) model in EnergyPlus and calibrated against measured data from an experimental DSF facility installed to an office building in Daejeon, South Korea. After a proper calibration of the simulated DSF model, the impact of blinds in the cavity of the DSF is also evaluated by adopting a slat blind model in EnergyPlus. For exterior and interior blind models, the simulated DSF model is modified by removing a DSF box and adding slat blinds at inner and outer surfaces of the windows. A Radiance-based daylighting simulation program, Daysim, is used to evaluate daylighting aspects of blinds and lighting controls within an office building with simulated DSF, interior blind, and exterior blind models. Generated lighting and blind raise/lower control schedules from Daysim are used as input values in EnergyPlus for annual thermal and lighting load calculations. In addition, the impact of natural ventilation to reduce trapped hot air within the cavity of the DSF box is considered in this study during a cooling period only for the DSF model. Results indicate that the simulated DSF model can save up to 40%, 2%, and 5% for heating, cooling, and total loads, respectively, when compared to the baseline (i.e., no passive technologies) without any blinds or controls. With the combination of the daylight-based dimming control based on the indoor illuminance levels and the blind raise/lower control, the simulated DSF and the exterior blind models could potentially reduce the building thermal loads and lighting energy consumption by around 27–52%., respectively.

建物調査による事前情報および短期間実測データを用いた熱負荷推定法に関する研究 (第2報)未知パラメータが増えた場合の対処法と実物件への適用

建物調査による事前情報および短期間実測データを用いた熱負荷推定法に関する研究 (第2報)未知パラメータが増えた場合の対処法と実物件への適用