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Thermal comfort in public buildings is crucial for occupant well-being and energy efficiency. This study employs TRNSYS software to simulate the effects of thermal mass, window performance, and window–wall ratio (WWR) on summer thermal comfort. The results indicate that without energy-saving measures, increased thermal mass raises daily average maximum and minimum temperatures by 0.33–0.96 °C and 0.14–0.94 °C, respectively. Enhanced WWRs lead to higher daily average maximum and minimum temperatures for double-glazed windows (0.18–0.61 °C and 0.07–0.62 °C, respectively), while single-glazed windows show increased maximum temperatures (0.18–1.86 °C) but decreased minimum temperatures (−0.01 to −0.72 °C). Thermal mass has a modest effect on indoor overheating during high outdoor temperatures. Double-glazed windows and lower WWRs effectively reduce indoor overheating, decreasing the attenuation coefficient by 2.13–28.94%. Conversely, single-glazed windows and higher WWRs enhance heat dissipation, increasing daily average temperature fluctuations by 2.33–44.18%. Notably, single-glazed windows with WWRs ≥ 50% improve thermal comfort by reducing extreme superheat temperature occurrence in heavy-thermal-mass buildings by 0.81 to 14.63%. Despite lower cooling loads with heavy thermal mass, double-glazed windows, and low WWRs, the study suggests that single-glazed windows and high WWRs can enhance summer thermal comfort. Therefore, reasonable shading measures and lighter thermal mass are recommended for such buildings.

PurposeBuildings consume a large amount of energy for space cooling during the summer season, creating an overall sustainability concern. The upfront cost associated with sustainability repels the decision-makers to often end up adopting solutions that have huge operations and maintenance costs. Therefore, the purpose of this study is to assess the lifecycle cost (LCC) implications of optimum configurations of active and passive strategies for reducing the cooling load in buildings.MethodsSeveral green building active and passive strategies and technologies were assimilated and their thermal performance in a hot semi-arid climate of Lahore in Pakistan using DesignBuilder V6.1 was simulated to obtain the most optimum cooling load configuration. Furthermore, LCC is estimated, and overall efficiency is evaluated to identify the most effective space cooling configuration.Results and discussionThe results suggest that a configuration of EPS for external wall insulation, vertical louvers for external shading, 6 mm blue HRG (low-E soft coated) + 12 mm air space + 6 mm clear glass for windows, polystyrene as roof insulation, cross ventilation through windows, and LED lighting system has the best performance. This is the first-of-its-kind study in the hot semi-arid climate of South Asia with the city of Lahore in Pakistan as the test case and can be generalized for places with similar conditions. The findings will help the decision-makers in selecting the most load-efficient and cost-effective green building technologies to help improve overall sustainability.ConclusionThe implementation of the proposed strategies not only aids in providing user-friendly and effective decision-making but also promotes the adoption of sustainability in buildings by leveraging the existing green building technologies to enhance the environmental and economic aspects. This is a promising approach to facilitate the spread of green building construction in developing countries. It is recommended to utilize the strategies grouped in Scenario 8 to achieve a reduced cooling load and LCC of a residential building throughout its lifecycle.

Rising energy demand for building cooling exacerbates the environmental challenges associated with energy consumption. Incorporating phase change materials (PCMs) into building envelopes, particularly sun‑exposed roofs, can substantially reduce energy use. This study examines the thermal‑storage efficiency of metallic, spherical PCM modules embedded within a reinforced concrete roof, designed for hot‑climate conditions. The roof is divided into four distinct thermal zones: Zone‑1 (conventional concrete), Zone‑2 (empty spherical modules), and Zones 3–4 (modules filled with organic PCMs, organic mixture, 35 °C (OM35) and organic mixture, 37 °C (OM37)). Important thermal performance metrics, such as temperature distribution, heat flux, thermal load, time lag, decrement factor, key response index, and carbon emissions savings, are evaluated. Integrating spherical PCM modules led to significant improvements. These include an average reduction in indoor surface temperature of 10.2 °C, a decrease in cooling load of upto 69%, and a reduced decrement factor. In addition, OM35 showed a higher key response index and enhanced thermal performance than OM37. The findings demonstrate the practical viability of spherical PCM‑integrated roofs as a passive‑cooling strategy for buildings in hot climates.

Large amounts of energy storage will be needed to manage renewable-intensive grids and to decarbonize buildings and transportation. Thermal Energy Storage (TES) has the potential to lower first cost while improving round-trip efficiency, safety, and durability compared to lithium batteries. Heating and cooling of buildings consumes 20% of global energy and drives peak electric loads, especially during extreme hot or cold weather. TES can shift heating and cooling loads to off-peak or renewable-intensive periods, thereby reducing grid stress and energy costs during peak periods and supporting renewable integration (by reducing electric consumption during periods when renewable supply is low, and increasing electric consumption when renewable supply is surplus to real-time needs). Integrating TES with heat pumps or chillers can improve efficiency by 20-30% by shifting operation into the heat pump or chiller's optimal efficiency range, and to the optimal time of day based on outdoor temperature (e.g. running the heat pump at night when it is cooler outside and storing cooling for use the next afternoon). In addition to this efficiency benefit, off-peak electricity is often half the price of peak electricity, and load flexibility is a significant benefit to electric utilities in meeting targets for very high reliability and resiliency. This paper reports on early testing of a novel, tunable TES system which uses proprietary materials to store heat and/or cooling at a range of adjustable temperatures optimal for space conditioning in buildings. For example, one can: (a) store heat in winter retuned to store cooling in summer, for 4-seasons markets, as a direct retrofit for chiller/boiler hydronic systems changing to heat pumps, and (b) store cooling in humid weather, at the low temperature required for dehumidification, retuned to store cooling in dry weather, at a more efficient, higher temperature. Tunability significantly reduces the required footprint compared to systems that use non-tunable materials, and provides flexibility to pursue peak load shifting, efficiency improvement, waste heat recovery or enhanced renewable integration as HVAC loads and electricity prices vary. Tunable TES can be applied to large building, campus and district energy applications, and can be used with air-source, ground-source or hybrid heat pump architectures. This paper will report on a recent collaboration between a pre-commercial start-up company and a research organization, where capacity (energy) and rate (power) were measured for stored cooling at 43[degrees]F (6[degrees]C) and stored heat at 150[degrees]F (65.5[degrees]C) at a meaningful lab scale. The research organization provided third-party measurement and verification to validate performance.

During the industrial period, many regions experienced a reduction in forest cover and an expansion of agricultural areas, in particular North America, northern Eurasia, and South Asia. Here, results from the Land-Use and Climate, Identification of Robust Impacts (LUCID) and CMIP5 model intercomparison projects are compared in order to investigate how land-cover changes (LCC) in these regions have locally impacted the biophysical land surface properties, like albedo and evapotranspiration, and how this has affected seasonal mean temperature as well as its diurnal cycle. The impact of LCC is extracted from climate simulations, including all historical forcings, using a method that is shown to capture well the sign and the seasonal cycle of the impacts diagnosed from single-forcing experiments in most cases. The model comparison reveals that both the LUCID and CMIP5 models agree on the albedo-induced reduction of mean winter temperatures over midlatitudes. In contrast, there is less agreement concerning the response of the latent heat flux and, subsequently, mean temperature during summer, when evaporative cooling plays a more important role. Overall, a majority of models exhibit a local warming effect of LCC during this season, contrasting with results from the LUCID studies. A striking result is that none of the analyzed models reproduce well the changes in the diurnal cycle identified in present-day observations of the effect of deforestation. However, overall the CMIP5 models better simulate the observed summer daytime warming effect compared to the LUCID models, as well as the winter nighttime cooling effect.

Shallow geothermal heat has the characteristics of wide distribution and huge reserves. However, for northern rural buildings, the heating load in winter is much greater than the cooling load in summer, and thermal imbalance of the soil is prone to occur. This paper takes rural residences in southern Hebei as an example and designs a solar-assisted shallow geothermal energy system. Compared with the original shallow ground-source heat pump system, the indoor and outdoor temperature differences of the target building were first analyzed. Second, the changes in the soil temperature field and the differences in the supply and return water temperature were monitored. Finally, the initial investment and operating costs of the assisted system are analyzed. The results show that the average ground temperature field increases significantly in winter. Through the alternate operation of solar energy and ground-source heat pumps, heat extraction from the ground is reduced, and the imbalance cycle of heat extraction in winter and heat removal in summer is shortened. It alleviates the imbalance of the cold and heat loads for soil throughout the year. The inlet and outlet water temperature and heat exchange efficiency of the buried pipes have been significantly improved. The energy efficiency ratio of the system using the assisted system has increased from 3.40 in 2020 to 4.17, an increase of 0.77. The optimal ratio of the solar- assisted shallow geothermal energy system is a 12.80 m 2 solar heat-collection area and one buried hole. The winter heating operating cost of the solar-assisted shallow geothermal energy system is 18.86 CNY/m 2 . It can save 37% of the annual operating costs of heating, cooling, and hot water compared to a single ground-source heat pump system and 40%–45% compared to traditional heating and cooling modes.

Energy consumption in buildings with large, glazed facades rises markedly in the summer, driven by cooling demands that vary with structural characteristics and external climate conditions. This study is unique in examining daily cooling needs in lightweight and heavyweight constructions, utilizing meteorological data from 782 summer days in Debrecen, Hungary. Unlike standard approaches, which often overlook localized meteorological variables, this analysis focuses on actual “clear sky” scenarios across distinct summer day types: normal, hot, and torrid. The findings indicate that orientation and construction type significantly affect cooling demands, with east-facing rooms demanding up to 14.2% more cooling in lightweight structures and up to 35.8% in heavyweight structures during peak hours (8 a.m. to 4 p.m.). This study reveals that for west-facing facades, extending use beyond 4 p.m. markedly increases energy loads. Furthermore, the cooling demand peak for heavyweight buildings occurs later in the day, driven by their higher thermal capacity. These insights underscore the importance of aligning HVAC system design with operational schedules and building orientation, offering data-driven strategies to enhance energy efficiency in buildings with diverse thermal and solar exposure profiles.

The heat transfer performance of a ground heat exchanger (GHE) directly influences the operational performance of a ground source heat pump (GSHP) system. The fluid temperature within the GHE is constrained by the protective temperature limits of the GSHP unit. Specifically, the inlet water temperature has an upper limit in summer and a lower limit in winter. These temperature limits further affect the heat exchange efficiency between the GHE and the surrounding soil. In this study, an experimental station featuring a single U-shaped GSHP system was constructed, and a three-dimensional model of the system was developed. Experiments were conducted by operating one or two GHEs to investigate the heat transfer per unit well depth and the matching relationship between cooling capacity and indoor load when the inlet water temperature of the heat pump unit approaches its summer and winter limits. In summer, when operating a single GHE, the heat transfer per unit well depth reached 134.4 W/m at an inlet temperature of 45 °C. When the cooling supply just matched the cooling load demand, the heat transfer per unit well depth was 131.5 W/m. However, prolonged operation led to a scenario where the cooling supply could no longer meet the load demand. In winter, operating a single GHE resulted in a heat transfer per unit well depth of 43.95 W/m at an inlet temperature of 5 °C. These results indicate that when the number of heat exchangers is insufficient, the inlet water temperature of the heat pump unit may reach or exceed the limit value, leading to decreased unit efficiency. Additionally, inadequate heat exchange between the GHE and the soil results in insufficient cooling or heating capacity, failing to meet the indoor load requirements.

Large-scale thermal use of shallow groundwater is often constrained in cities because temperature plumes can extend far beyond project boundaries and affect third-party water rights. Unidirectional Aquifer Thermal Energy Storage (UD-ATES) addresses this by reversing the conventional open-loop arrangement. The injection well is placed up-gradient and the production well down-gradient. During summer cooling, warmed return water is injected up-gradient; the resulting warm plume is carried by the natural groundwater flow to the down-gradient well and can be recovered in the following heating season. Conversely, during the heating season, cooled water is injected up-gradient; the resulting cold plume drifts down-gradient and can be recaptured for cooling in the next summer. This configuration is particularly suited to shallow, highly permeable aquifers with pronounced natural gradients, settings in which classical ATES suffers from advective losses, while also minimizing off-site thermal impacts that complicate permitting. At the State Hospital Graz South site (Austria), we surveyed and characterized the aquifer and built a coupled groundwater-flow and heat-transport model to design a UD-ATES well pair tailored to local conditions. The optimized spacing between injection and production wells is ∼463 m, aligning transport time with the seasonal load profile with a peak thermal power of 1.25 MW (60 L s−1 by a ΔT of 5 K). Resulting temperature anomalies remain largely confined to the property, with the thermal signal decaying to below 1 K within a few hundred metres downstream. Despite an unavoidable imbalance between heating and cooling demand over the year, the system recovers a substantial fraction of the injected energy and markedly reduces the thermal footprint compared with a conventional open loop scheme. The thermal recovery factor amounts to 0.38. An expansion of the plant to a total peak thermal power of >3.5 MW using three pairs of wells appears to be feasible at the location in question. These findings support UD-ATES as a practical pathway to decarbonize large, space-constrained consumers in high-flow aquifers while safeguarding neighbouring groundwater uses.

A louver is a traditional environmental control device and passive architectural element based on an ecofriendly concept. Louvers are architectural elements that can be used to regulate natural lighting, thermal environment, and building energy use. To realize these integrated functionalities of louvers, they must be designed considering the climate and geographical characteristics of the target region. However, these aspects are typically not considered during building design in Korea, resulting in lovers being used as design elements with simple natural lighting control functions. Therefore, the objective of this study was to promote the integrated use of louvers by optimizing the louver angle according to the microclimate in Korea from the viewpoint of thermal energy use. We performed load and energy simulation planning and calculation and conducted optimization studies for the louver angle and range of motion for each region. The energy consumption in central and southern Korean regions was minimized when the angles of the fixed louvers were 45°–75° and 60°–90°, respectively. Kinetic louvers could enhance thermal energy management when installed at 30°–75° in spring, 135°–165° in summer, 75°–165° in autumn, and 45°–75° in winter. These findings can promote the realization of integrated functionalities of louvers from the perspective of indoor environment comfort based on the microclimates of the Korean regions.