Annual Heat Loss Research Articles

Numerical modeling of heat losses from hot water storage tank

Domestic hot water storage tanks (HWST) are widely used devices, and their daily operation can generate significant annual heat losses to the environment. Previous studies concerning HWST have mainly focused on the impact of insulation quality and thickness, stratification, and tank operation on total heat losses. Some studies have addressed these losses concerning different parts of the tank, including upper, lower, and side walls. However, the influence of insulating additional tank elements, such as connectors, on heat loss has not been analyzed.Therefore, experimental studies were conducted as a reference for the temperature distribution and heat loss from an insulated HWST equipped with 12 connectors. Then, CFD numerical calculations of heat loss were performed for various variants: an insulated HWST without connectors, a tank with connectors insulated in five different ways, and an uninsulated tank.It was found that, in extreme cases of poor insulation of the tank connectors, the heat loss increased by 92.5 % and 147.6 %, respectively, compared to the reference loss. This means an increase in heat loss streams by 62.0 W and 98.9 W compared to the reference case. The latter value corresponds to an annual heat loss of approximately 3 GJ. The study also showed that insulating the bottom of the tank is crucial. With proper insulation, heat losses from this part account for less than 10 % of the total heat loss.The results highlight the critical role of proper connector insulation in minimizing standby heat losses in water storage systems.

Thermal storage and loss characteristics of underground water pits of solar district heating systems in Xizang Plateau, China

Large-scale thermal storage systems are crucial for solar district heating systems. Currently, there is less engineering guidance on the heat loss patterns of underground water pits, especially in the special climatic conditions of the Xizang Plateau. Therefore, this study analyzes the heat transfer characteristics of underground water pits in the plateau climate. A cylindrical underground water pit model is constructed, and the heat loss law of underground water pits of the heating season and seasonal heat storage is investigated under multiyear operation. The results show that the heat loss rate of the underground water pit with seasonal heat storage is 0.8 % higher than that of the heating season heat storage for the same volume. The difference in heat loss between the two heat storage modes is small. The heat loss from the top, sides and bottom of an underground water pit accounted for 34.2 %, 36 % and 29.8 % of the heat loss in the first year, respectively. The percentages of heat loss from each surface after ten years of operation were 46.7 %, 36.6 %, and 16.7 %. In addition, the functions of storage volume and heat loss per unit volume of the first year in Xizang were fitted. The relationship equation between heat loss per unit volume of the first year and the annual heat loss per unit volume in the nth year was obtained. This study provides support for the heat loss of underground water pits that operate continuously for many years.

Assessing the impact of evapotranspiration from green roofs on reducing surface temperatures

Evapotranspiration is an important process in green roofs to reduce surface temperature; however, it is still not well understood. This study aims to assess the influence of irrigation and vegetation parameters in the evapotranspiration of green roofs and surface temperature. Green roofs with almost no vegetation, short Sedum and tall Sedum with 0, 3 and 6 mm irrigation were considered in Lisbon (Portugal) and Florianópolis (Brazil) climates. The outside roof surface temperature was experimentally assessed in an extensive green roof prototype and used to validate the computer simulation. The results showed that although irrigation can enhance evapotranspiration, mainly in drier regions, denser vegetation has a higher impact on this process. The annual latent heat losses of the tall Sedum green roof overcome those of roofs with almost no vegetation by 695.9 kWh/m2 in Lisbon and by 471.8 kWh/m2 in Florianópolis. Green roofs with tall Sedum also resulted in lower substrate temperatures, even without irrigation. The hourly substrate temperature of green roofs with tall Sedum can be lower than the outside surface temperature of traditional roofs by up to 33.4 °C in Lisbon and up to 24.0 °C in Florianópolis. In these roofs, the latent heat fluxes correspond to 40 % and 48 % of the total losses in Lisbon and Florianópolis, respectively. It was concluded that latent heat losses accounted for a higher percentage of the energy balance of the green roofs whose reductions in surface temperature were more significant. This research provides valuable insights regarding the relationship between evapotranspiration and surface temperature and the role of evapotranspiration on the energy balance of green roofs with crassulacean acid metabolism (CAM) plants.

Вплив підвищення нормативних вимог на рівень теплової надійності та втрати тепла через стіни й покриття житлових і громадських будівель

New edition of the State Building Regulations of Ukraine DBN V.2.6-31:2021 "Thermal insulation and energy efficiency of buildings" significantly increases the requirements for heat transfer resistance of walls and coatings of civil buildings. This study was carried out with the aim of evaluating the impact of the increased requirements of DBN V.2.6-31:2021 on the energy efficiency and comfort of buildings by comparing the thermal reliability characteristics of walls and roofs of civil buildings in different regions of Ukraine. The walls and combined roofs of residential and non-residential public buildings were analysed, the requirements for which in DBN B.2.6-31:2016 and DBN B.2.6-31:2021 differ in the minimum permissible value of heat transfer resistance, but coincide in other indicators. Climate conditions for the operation of buildings are reflected by data on atmospheric air temperature at 57 weather stations of Ukraine, which are given in DSTU-N B V.1.1–27:2010. The comparison of the same type of enclosing structures is made according to the criteria of reducing annual heat losses due to the enclosing and the probable duration of thermal failures. Annual heat losses in the set of each of the 57 weather stations are calculated according to the known dependencies of thermal physics. The durations of thermal failures of enclosures according to the comfort criterion are determined by the probabilistic method previously developed by the authors, which takes into account random fluctuations in the temperature of the external atmospheric and internal air in the room, as well as the random character of the heat transfer resistance of the enclosures. The probable duration of thermal failures of enclosing structures according to the comfort criterion, depending on the permissible temperature difference of the internal air and the inner surface of the enclosing structure, established in DBN B.2.6-31, can differ by two orders of magnitude. This indicator should be used only to compare the level of thermal reliability of enclosures with the same values of the permissible temperature difference. The increase in the heat transfer resistance of walls and roofs of residential and public buildings implemented in DBN V.2.6-31:2021 led to a decrease in heat loss by an average of 17%, a decrease in the probable duration of thermal failure of walls according to the comfort criterion by 17%, and combined roofs by 54 %.

Experimental and numerical study of adaptive ventilation and sunlight regulation building envelope combining variable transparency shape-stabilized phase change material

The development of adaptive building envelopes with advanced PCM to reduce building energy consumption is a promising topic. This study proposed an adaptive ventilation and sunlight regulation wall (AVSRW) by combining the variable transparency shape-stabilized PCM (VTSS-PCM), reflective film, and ventilation cavity. The combination of VTSS-PCM and reflective film could passively regulate the solar absorptivity (SA) of AVSRW. The ventilation cavity with airflow control enhanced the heat storage and release efficiency of VTSS-PCM. A dynamic photo-thermal coupling model of the AVSRW was presented and validated by a full-scale experiment in summer and winter conditions. Then, based on the weather data of the typical meteorological year of Changsha, China, the performances of AVSRW on days, months, and a year were evaluated. The impact of three influential factors and their combined effects on the performance of AVSRW were analyzed. Ultimately, a global optimization was conducted to improve the performance of AVSRW, and compared with the massive wall. The results showed that the AVSRW passively decreased its SA on summer days and increased its SA on winter days. The total annual undesired heat exchange (TAHE) of AVSRW first decreased and then increased with the increase of melting temperature (Tm) and thickness (L) of VTSS-PCM. The reflective film had an opposite effect on the annual heat gain (AHG) and annual heat loss (AHL) of AVSRW, resulting in the TAHE remaining unchanged with the increase of reflectivity (R) of the reflective film. The greater the L, the smaller effect of the Tm and R on the AHG and AHL, and the greater the R, the greater effect of the Tm and L on the AHG and AHL. After optimization, the values of the Tm, L, and R corresponding to the optimal solution were 24.60 °C, 0.17 m, and 0.63, respectively. Compared with the reference wall, the AVSRW with the best performance had lower AHG and AHL, and the annual energy-saving rate of the AVSRW reached 43.49%. This study guides the application and parameter optimization of AVSRW in hot summer and cold winter regions.

Thermal Performance Evaluation of Non-Autoclaved Aerated Concrete Produced with Crushed Waste Glass Bottle Aggregate and Glass Fiber

. This paper evaluates the thermal performance of non-autoclaved aerated concrete (NAAC) produced with crushed waste glass bottle aggregate and glass fiber. A total of six different mixtures, including the partial substitutions of normal sand with waste glass sand (WGS) (0%, 15%, and 30%) and glass fiber (1%, 2%, and 3%), were designed. After the compressive strength and thermal conductivity (λ) of each NAAC mixture were firstly determined, the potential of NAAC to improve the thermal performance of student residential buildings was assessed. The energy-saving effect of NAAC was simulated using Autodesk Revit software tools in two different cities, Nur-Sultan in Kazakhstan and Boston in the USA. Moreover, annual heat loss was calculated. Test results present that the increase of WGS and glass fiber contents leads to increasing compressive. Interestingly, while increasing WGS content in the mixture decreases λ, increasing fiber content increases λ despite a slight variation. The lowest annual heat loss was obtained from the mixture containing 70% normal river sand, 30% WGS, and no glass fiber. 70NS-30WG-0GF. Finally, the energy performance simulation result indicates that NAAC used in a residential building leads to significant energy savings compared to normal concrete and brick structure.

Performance enhancement of building energy through the combination of dynamic insulation panels and phase changing materials

The use of phase change materials (PCM), a type of heat transfer thermal storage substance, shows the opportunity to enhance the thermal inertia of these structures lacking significantly altering present construction methods. Because of the decreased indoor temperature swings and the load reduction, the usage of PCMs in buildings has the potential to deliver higher indoor temperatures for inhabitants as well as weaker export power consumption. Thermal energy storage (TES) systems based on phase change material (PCM) is identified as among the most enhanced energy techniques to improve eco-efficiency and conservation. The proposed dynamic insulating material and system (DIMS) allows for thermal resistance to be adjusted based on interior and outside variables. While it can be shown that using PCM and DIMS in facades enhances energy efficiency, there have been no previous studies that looked at the combined effect of the two technologies. Explore a unique wall design that includes a sheet of PCM made up of two levels of DIMS in this research. In most of the seasons and building orientations studied in this research, the PCM-DIMS-integrated wall saves much more energy than the DIMS-only combined barrier or the PCM-only combined walls. The PCM-DIMS-integrated walls can give a 15% to 72% decrease in yearly radiant heat then a 7% to 38% reduction in annual heat loss, based on the environment. The findings of this study highlight the necessity for scaled dynamic insulating layers for structures, as well as thermal storage devices.

Separate and combined integration of Kalina cycle for waste heat recovery from a cement plant

This article reports on using Kalina cycle for waste heat recovery from a cement plant. Two design alternatives have been investigated using separate and combined waste heat recovery from the kiln, cooler, and preheater. Measurements and analysis have been performed to determine the waste heat from different stages of the cement manufacturing lines. The annual heat losses from the kiln surface, preheater, and the cooler are estimated as 79.23 GWh, 44.32 GWh, and 43.6 GWh at average temperatures of about 314?, 315?, and 254?, respectively. Analysis and optimization of using Kalina cycle for waste heat recovery from the kiln shell, cooler and preheater to produce electricity have been carried out using ASPEN software. Parametric study has been carried out to determine the design parameters for Kalina cycle including turbine inlet pressure, mass-flow rate, and NH3-H2O concentration. The value of net power output using combined waste heat recovery is about 7.35 MW as compared to 6.86 using separate waste heat recovery design with a total cost saving of about 23%.

The community heating network’s thermal condition assessment

Heat losses at the heating network’s distribution pipelines were identified for Karkivcommunity. Heat losses’ calculation is performed in view of the underground pipelines’ installationin non-accessible ducts. The heating system water temperature is accepted in line with the heatingnetwork temperature chart and according to the design outdoor temperature value for heatingpurposes. Specific heat losses in the network section’ pipelines are accepted at the level of standardvalues for the specified network laying method. The water flow rate at the heat pipeline sections isdefined as per the design heat loads from the buildings connected to the heat supply network. Theheat pipeline segment with uniform diameter is accepted as the rated section. The soil temperatureat the heat pipeline axis laying depth is accepted as 5°C. The heat losses at the structural networkelements are considered by 1.15 coefficient. The calculations are performed in view of the heatingsystem water flow rate and temperate changes along the heat pipeline length. While analyzing thethermal condition of the return pipelines of the community heating network, the changes in the heatcontent of the heating system water flow in the main direction pipeline during mixing with the waterflow from the branches of the main direction line are taken into account. Considering the averagetemperature of the coldest five days consecutively, the total energy loss in heating pipeline for a groupof buildings in Kharkov region are equivalent to 180.8kW.In view of the ambient air temperature changing over the heating period for Kharkiv cityclimate conditions and the current schedule for quality heat energy supply to the consumers controlthe annual heat losses in the community heating network pipelines were calculated. The soil temperature change at the heat pipeline installation depth during the heating period was notconsidered.Heat losses in the microdistrict network for the year are 2184 GJ. The data obtained can beused to compare options when developing a strategy for reforming the microdistrict heat supplysystem.

Evaluation of Non-Autoclaved Aerated Concrete for Energy Behaviors of a Residential House in Nur-Sultan, Kazakhstan

Autoclaved aerated concrete (AAC) is commonly used as a modern, energy-efficient construction material in Nur-Sultan, Kazakhstan—the second-coldest national capital in the world after Ulaanbaatar, Mongolia. The autoclave curing method used to manufacture the AAC has potential risks and is environmentally costly because of its high-pressure and -temperature operation. Therefore, for phase I and II studies, non-autoclaved aerated concrete (NAAC) was cast, and its properties were evaluated in terms of compressive strength, density, porosity, and thermal conductivity. Moreover, the thermal conductivity prediction model of NAAC was successfully developed. In this Phase III study, the energy behavior of the NAAC was evaluated by energy simulation for a typical two-story residential house model in Kazakhstan. Different wall materials, such as fired brick and normal concrete, were adapted to compare the energy performance of NAAC. Finally, the annual heat loss and amount of heat transferred through the wall of the house were calculated to cross-check the energy-saving effect of NAAC. It was found that the NAAC conserved energy, because the heating and cooling loads, annual heat loss, and amount of heat transfer of NACC were lower than those of fired brick and normal concrete.

Determination of the Temperature Graph of Heat Supply With Minimal Heat Losses

Heat losses by pipelines of heat supply systems are calculated for the average temperature of the heat carrier per year or for the heating period for the conditions of a qualitative method of regulating the heat load. The presence of cuts of the temperature graph, the use of other methods of central regulation, are not reflected in the regulatory documents and require special research, which determines the relevance of the work. Heat losses through thermal insulation structures of pipelines have been determined for various graphs of central regulation. Heat losses were determined for each external temperature, taking into account its duration. It is shown that the average linear annual heat losses for most of the graphs correspond to a lower external temperature than the average external temperature for the heating period. Therefore, the calculation must be performed for a higher temperature of the heat carrier than is accepted according to regulatory documents.

Heat Loss Due to Domestic Hot Water Pipes

Domestic hot water (DHW) system energy losses are an important part of energy consumption in newly built or in reconstructed apartment buildings. To reach nZEB or low energy building targets (renovation cases) we should take these losses into account during the design phase. These losses depend on room and water temperature, insulation and length of pipes and water circulation strategy. The target of our study is to develop a method which can be used in the early stages of design in primary energy calculations. We are also interested in how much of these losses cannot be utilised as internal heat gain and how much heat loss depends on the level of energy performance of the building. We used detailed DHW system heat loss measurements and simulations from an nZEB apartment building and annual heat loss data from a total of 22 apartment buildings. Our study showed that EN 15316-3 standard equations for pipe length give more than a twice the pipe length in basements. We recommend that for pipe length calculation in basements, a calculation based on the building’s gross area should be used and for pipe length in vertical shafts, a building’s heating area-based calculation should be used. Our study also showed that up to 33% of pipe heat losses can be utilised as internal heat gain in energy renovated apartment buildings but in unheated basements this figure drops to 30% and in shafts rises to 40% for an average loss (thermal pipe insulation thickness 40 mm) of 10.8 W/m and 5.1 W/m. Unutilised delivered energy loss from DHW systems in smaller apartment buildings can be up to 12.1 kWh/(m2·a) and in bigger apartment buildings not less than 5.5 kWh/(m2·a) (40 mm thermal pipe insulation).

Thermal regime of Cryosols and underlying permafrost in North Yakutia in the context of global climate change

The warming and an increase in the amount of solid precipitation, which became apparent in North Yakutia on the threshold of the 21st century, have led to an increase of soil temperature in winter season and of the permafrost. The heat fluxes measured in the taiga soil on the Kolyma Lowland reveal an imbalance in the annual heat gain and loss in the cryogenic ecosystem amounting to 26.3–56.1% of the incoming energy. An increase in the summer air temperatures of the 2000th caused a universal increase in the depth of seasonal soil thawing. After the drop in high summer temperatures, the active layer thickness (ALT) either continued to grow or stabilized at higher levels in the watershed ecosystems of the Kolyma Lowland; however, ALT returned to its initial values in the tundra of the Yana-Indigirka Lowland. As for the floodplain landscapes, ALT increased near-linearly over the 24 years of monitoring. The waterlogged tundra and taiga soils as well as the upland gleyzem of the Bykovsky Peninsula differed only by a temporary increase in the thawing depth. The degree of the soil and permafrost thermal regime transformation tends to increase from west to east, fitting the heterogeneity of climate changes.

Negative thermal-flux phenomenon and regional solar absorbing coating improvement strategy for the next-generation solar power tower

Solar power tower (SPT) is regarded as the most promising technology for applications in concentrating solar power. However, a significant decrease in the solar-thermal conversion efficiency of the tower receiver in the SPT system occurs at high operating temperatures due to the massive radiation heat loss caused. In this work, a detailed heat transfer model of the tower receiver was established, and the negative thermal-flux phenomenon was discovered in the tower receiver based on the verified simulation results. In this context, a novel improvement strategy for regional solar absorbing coating on the tower receiver was proposed to enhance the thermal performance of the tower receiver in the next-generation SPT system. Two kinds of novel tower receivers by changing conventional solar absorbing coating into the silver-based coating (novel receiver I) and black chrome-based coating (novel receiver II) at negative thermal-flux regions were proposed, investigated, and compared with the prototype tower receiver without changes. The overall thermal performance of three kinds of tower receivers was numerically analyzed under different solar irradiances, solar hours throughout the day, and seasons. The results demonstrated that both the novel tower receivers achieved breakthrough enhancements on the thermal performance compared with the prototype receiver, showing great potential for practical application. The negative thermal-flux regions accounted for almost a quarter of the entire receiver surface. The annual average radiation heat losses from negative thermal-flux regions in the novel receivers I and II were effectively reduced by 93.00 and 53.14%. Accordingly, the annual average heat gains and receiver efficiencies were significantly enhanced by 6.54 and 6.03%, respectively.

Proposals for standardization the heat transfer resistance of insulated walls of residential buildings in the Republic of Belarus

Introduction. Resistance to heat transfer is considered the main criterion of energy operational efficiency in the design of enclosing structures of buildings and structures. Therefore, the calculation of the values of the normalized resistance to heat transfer, for each locality of the Republic of Belarus, taking into account the actual outdoor temperatures and the duration of the heating season is an urgent task.
 Materials and methods. To assess the energy efficiency of enclosing structures, the value of annual heat losses Q, kWh/m2, through 1 m2 of the structure was adopted. The calculation of the values of the normalized heat transfer resistance for each locality of the Republic of Belarus, taking into account the actual outdoor air temperatures and the duration of the heating season, was carried out according to the method recommended by V.G. Gagarin. A comparative analysis of the results obtained according to the methods recommended by TCP 45-2.04-196-2010* and SP 50.13330.2012 is carried out.
 Results. The calculations determine the values of the normalized heat transfer resistance for each locality of the Republic of Belarus, taking into account the actual outdoor air temperatures during the heating period and the duration of the heating season. To facilitate the design of insulated walls, a map of the recommended (calculated) values of the heat transfer resistance of the external walls of residential buildings for the territory of the Republic of Belarus is constructed.
 Conclusions. According to the results of the performed studies, it was found that the economic efficiency in the design of insulated walls according to the method recommended by TCP 45-2.04-196-2010*, depending on the region of the Republic of Belarus for which the design is being carried out, is on average from 6 to 8 BYN per 1 m2 of insulated wall.

Numerical investigations of long-term thermal performance of a large water pit heat storage

Water pit heat storage is an effective long-term heat storage. Experimental and theoretical investigations of a 60,000 m3 water pit heat storage in Dronninglund, Denmark was carried out with an aim to study its long-term thermal performance. Experimentally, detailed measurements were analyzed to monitor thermal behavior of the store, including flow rates, temperatures of the inlet and outlet flow, thermal stratification in the store and temperatures of the surrounding soil at four different depths. Theoretically, a simulation model of the water pit heat storage was developed based on the Type 343 model (ICEPIT) in TRNSYS. The calculated temperatures were compared to the measurements. The developed model was used to investigate the influence of soil properties and inlet arrangement on the thermal performance of the store. The result show that the simulation model predicts well the thermal behavior of the store. Over the whole year, the calculated average temperature of the store differed within ±4.7 K from the measured values. The measurements show that the annual charged and discharged heat are 12,787 MWh and 11,957 MWh respectively. The deviation of the charged and discharged energy between the simulation and the experiment did not exceed ±4%. The annual storage efficiency reached 90% in the second year of operation. The calculated ground temperatures were consistent with the measured ones at different depths. Measured heat loss of the store is 1392 MWh. As elucidated by the model, the heat loss from the cover contributed to 60% of the annual heat loss, while the heat loss from the sidewall and the bottom contributed 38% and 2% respectively. The influence of soil types on thermal performance of the store is significant. For a PTES surrounded by dry soil, the storage efficiency can reach 90%, while for a PTES surrounded by wet sandy gravel, the storage efficiency decreases by 7%. Change of the height of the middle inlet/outlet diffuser could slightly improve the storage efficiency by 1%. The restrains of the model were analyzed and the focus areas of further investigations were pointed out. The findings of the paper give good reference for researchers, designers and consultants in planning of a solar heating plant with a large water pit heat storage.

INVESTIGATION OF USING KALINA CYCLE FOR WASTE HEAT RECOVERY IN A CEMENT PLANT

The cement industry is considered one of the most energy intensive industrial processes in the world. The energy cost average is about 55% of the total cost of cement production. Massive energy cost is due to both heat consumption in kiln operations and electrical power consumption for different operations of grinding mills, fans, and motors. Waste heat recovery is a way to reduce the total power consumption for the cement production process by using a heat recovery system to generate electrical energy with no more fuel or electrical power consumption. In a typical cement plant, 25% of the total energy is electrical energy, and 75% is thermal energy. About 35-40% of the total process heat is lost through waste heat streams. In a cement plant, 26% of heat input is lost through the kiln, preheater surfaces, convection from the kiln, and preheaters. This article reports on waste heat recovery from a typical cement plant in Egypt. Measurements and analyses have been performed to determine the waste heat from different stages of the cement manufacturing lines. The annual heat losses from the kiln surface, preheater, and the cooler are estimated as 79.23, 44.32, and 43.6 GWh at average temperatures of about 314, 314, and 254℃, respectively. Analysis and optimization of using the Kalina cycle for Waste Heat Recovery (WHR) from the kiln shell, cooler, and preheater to produce electricity have been carried out using ASPEN software. A parametric study has been carried out to determine the design parameters for the Kalina cycle including turbine inlet pressure, mass flow rate, and ammonia water concentration. Two design alternatives have been investigated using separate and combined WHR from the kiln, cooler, and preheater. The value of net power output using combined WHR is about 7.35 MW as compared to 6.86 using a separate WHR design with a total cost saving of about 23%. تعتبر صناعة الأسمنت من أکثر العمليات الصناعية کثافة في استخدام الطاقة في العالم. يبلغ متوسط ​​تکلفة الطاقة حوالي 55٪ من التکلفة الإجمالية لإنتاج الأسمنت. ترجع تکلفة الطاقة الهائلة إلى کل من استهلاک الحرارة في عمليات الفرن واستهلاک الطاقة الکهربائية للعمليات المختلفة لعمليات الطحن للمواد الخام والتبريد عن طريق المراوح نقل الخامات. يعد استرداد الحرارة المهدرة طريقة لتقليل إجمالي استهلاک الطاقة لعملية إنتاج الأسمنت باستخدام نظام استرداد الحرارة لتوليد الطاقة الکهربائية دون مزيد من استهلاک الوقود أو الطاقة الکهربائية. في مصنع الأسمنت النموذجي، يتم فقدان حوالي 35-40 ٪ من إجمالي الطاقة الحرارية خلال تيارات الحرارة المهدرة. يفقد الغبار، وتصريف الکلنکر، والإشعاع من الفرن، وأسطح التسخين المسبق، والحمل الحراري من الفرن، وهذا يمثل ما يقرب من 26٪ من مدخلات الحرارة. نتناول في هذا البحث طرق استرداد الحرارة المهدرة من مصنع أسمنت نموذجي في مصر عن طريق دورة کالينا. تم إجراء القياسات والتحليلات لتحديد الحرارة المفقودة من المراحل المختلفة لخطوط تصنيع الأسمنت. تقدر الخسائر الحرارية السنوية من سطح الفرن والتسخين المسبق والمبرد بـ 79.23 و44.32 و43.6 جيجاوات ساعة بمتوسط ​​درجات حرارة حوالي 314 و314 و254 درجة مئوية على التوالي. تم إجراء تحليل وتحسين استخدام دورة کالينا لاستعادة الحرارة المفقودة من الفرن والمبرد والتسخين المسبق لإنتاج الکهرباء باستخدام برنامج اسبين تم إجراء دراسة بارا مترية لتحديد معايير تصميم دورة کالينا بما في ذلک ضغط مدخل التوربينات، ومعدل التدفق الکتلي، وترکيز نسبة الماء والأمونيا. تم فحص بديلين للتصميم لاستعادة الحرارة المفقودة باستخدام برنامج اسبين من خلال فصل ودمج الطريقتين وتطبيقهم في مرحلة الفرن والمبرد والتسخين المسبق. تبلغ قيمة صافي خرج الطاقة باستخدام مجتمعة حوالي 7.35 ميجاوات مقارنة بـ 6.86 باستخدام تصميم منفصل لتوليد الطاقة مع توفير إجمالي في التکلفة يبلغ حوالي 23٪.

Enhancing building energy performance by effectively using phase change material and dynamic insulation in walls

Deploying phase change materials (PCMs) in building envelopes can be effective in reducing space heating/cooling loads and providing load shedding and shifting capacity. However, the full potential of PCM-integrated envelopes can only be harnessed if the PCM undergoes phase change using free ambient heating/cooling, and the stored energy is effectively transferred between the exterior and the interior environments. Traditional thermal insulation (with a fixed thermal resistance) limits PCM utilization, which restrains the energy saving potential of a PCM-integrated envelope to a small percentage. Proposed dynamic insulation material and system (DIMS) provides the option of varying its thermal resistance based on the indoor and outdoor conditions. Although it has been established that employing PCM as well as DIMS in building envelopes separately improves buildings’ energy performance, no prior studies that analyzed the combined influence of both technologies were identified. In this study, we examine a novel wall design, comprising a layer of PCM between two layers of DIMS. We note that the PCM-DIMS-integrated wall provides significantly higher energy saving potential than the DIMS-only integrated wall or the PCM-only integrated wall in all the climates and wall orientations analyzed in this study. Depending on the climate, the PCM-DIMS-integrated wall could provide 15–72% reduction in annual heat gain and 7–38% reduction in annual heat loss. The analysis presented in this study supports the need to develop scalable dynamic insulations combined with thermal energy storage systems for buildings.

Influence of geometry on the thermal performance of water pit seasonal heat storages for solar district heating

The aim of the study is to investigate the influence of geometry on the thermal capacity and stratifications of a water pit heat storage for solar district heating. A TRNSYS component model for a truncated cone water pit was developed based on the coordinate transformation method and validated by experimental results from the water pit heat storage in Huangdicheng in 2018. The thermal performance of 26 water pits with different heights and side wall slopes was calculated for 10 consecutive years. It takes four to six years for the water pit to reach steady-state operation. The operation data from the tenth year was selected to evaluate the thermal performance of each configuration. The results show that because of the thermal insulation on top of the water pit, the height to diameter ratio of a water pit with minimum annual heat loss was always smaller than 1.0. The annual storage efficiency of a water pit increases with side wall slope due to the reduced side wall area. There is an almost linear increase in the thermal stratification number of a water pit with height. With an increase in the height, thermal stratification in water pits with a steeper slope increased more gradually than water pits with a lower slope. The findings in this paper are relevant for the design optimization of water pits as seasonal thermal energy storages.

Method for Assessing Heat Loss in A District Heating Network with A Focus on the State of Insulation and Actual Demand for Useful Energy

The goal of this paper was to evaluate heat loss and the demand of district heating (DH) in the context of the fourth generation DH concept using a data-driven approach. The heat loss profile was calculated with GIS Zulu© (software (8.0.0.7539, Politerm, LLC, St.Petersburg, Russia) using eight various states of insulation, detailed information on thermal conductivity, internal heat transfer coefficient, and geometry of the concrete trench. There is a strong correlation between the heat sold and the average annual outdoor temperatures. The outstanding episodes are extremely rare, and the difference in the overall pattern is elusive. The results of the annual heat production and annual heat loss analyses were compared using three different estimation methods. The new method was the only one that showed a positive effect after the complete modernization of thermal insulation. The actual proportion of heat loss is much higher at 16%, while the actual heat delivery is less than anticipated at 85–86% only. The trend of the normative approach is correct but cannot determine changes in network heat loss due to aging. The method focuses on the effects of the state of insulation and actual supply temperature levels. The transition to smart energy systems includes strategic and progressive energy planning, as well as new pricing rules and tariffs. Thus, the method presented is the first step in the transition towards the fourth generation DH networks.