Passive Solar Research Articles

Earthship buildings: opinions on their contribution towards sustainable alternative housing in the UK

Earthship buildings are marketed as being an epitome of sustainable alternative housing. Built by reusing or repurposing mostly reclaimed urban waste products, their design includes the utilisation of low-embodied-energy materials, passive solar heating and cooling, photovoltaic power systems, rainwater harvesting and solar hot water heating, along with black- and greywater-treatment systems. This study explores stakeholder opinions of whether Earthship buildings can contribute towards the future of alternative housing in the UK. Opinions were sought through a questionnaire completed by UK members of online social media groups whose shared focus is related to sustainability (n = 50). The results reveal that the public believe that the main benefits are their minimal environmental impact and also their reliance on renewable energy resources, while the main barriers are identifying suitable building plots and obtaining the necessary planning permissions. Notwithstanding that the participants included in this study already have sustainability interests, it is surmised that the public deem that the general principles of Earthships are an acceptable choice of alternative home/living. However, while the uptake of Earthship homes proves increasingly popular in some parts of the world, the utmost concern within the UK setting is the reality of finding somewhere suitable to build an Earthship and acquiring necessary authorisations to construct the building.

Development and characterization a novel leakage-proof form stable composite of graphitic carbon nitride and fatty alcohol for thermal energy storage

The form-stabilization ability of the produced graphitic carbon nitride (g-C3N4) for preventing the leakage of stearyl alcohol (SAOH) as promising organic phase change material (O-PCM) was investigated comprehensively. The SEM analysis showed that the g-C3N4 had well defined pores which is capable to confine the molten SAOH in them. The FTIR and XRD confirm the chemical compatibility of g-C3N4 and SAOH. The differential scanning calorimetry thermogram showed that the melting and freezing temperature of the FS-OPCMs including 70 wt% SAOH were 54.57 °C and 55.25 °C with respective high latent heats as 191 kJ/kg and 187 kJ/kg respectively. The thermal aging test for 1000 melt/freeze cycles confirmed that structure and thermal degradation durability are excellent. The thermal conductivity of developed FS-OPCM is enhanced by 122 %, which were resulted in about 50–54 % reduction in the charging/discharging time of FS-OPCM relative to the SAOH. The results exposed that the developed g-C3N4/SAOH (70 wt%) composite can be considered as potential solar energy storage material in different implementations such thermal cooling of photovoltaic panels, automotive and electronic units as well as solar residential water heating and passive solar space heating.

Experimental and numerical simulation of paraffin-based ternary composite phase change material used in solar energy system

A series of paraffin-based ternary composite phase-change materials (PCMs) were prepared by combining paraffin (PA) with expanded graphite (EG) and nano-copper (Cu) in a two-step method. The thermal properties of the composite PCMs were studied by establishing an experimental test system and a simulation model. The results showed that the network pore structure of EG restrained the agglomeration phenomenon of Cu and that the addition of Cu improved the thermal conductivity, heat storage and release rate of the PA/EG composite PCMs. When the PA and EG mass percentages were 93/7 and the mass fraction of Cu was 1.25%, the thermal conductivity and thermal diffusivity were 2.57 W/(m·K) and 1.72 mm2/s, respectively, which were 9.5 and 13.5 times higher than PA, and the latent thermal value reached the theoretical value. Cu significantly accelerated the phase-change process of the composite PCMs, and the storage and release heat-response rates increased by 152.17% and 100%, respectively. After 200 storage/release cycles, there was little additional effect on the phase-change temperature and heat storage capacity. Compared to pure PA, the performance of the composite PCMs improved significantly, indicating that these composite PCMs are suitable for passive solar heating.

A Perspective on the optical spectral design for passive solar heating and radiative cooling

Heating and cooling, as the basic requirements of human life, account for more than 28% of global energy consumption. To minimize carbon footprint and save energy, various strategies based on passive heating and cooling have attracted much attention. Typically, as the sun and outer space are the natural thermodynamic resources for renewable energy harvesting, passive solar heating and radiative cooling have been widely explored through a precise spectral design to effectively exploit solar energy and thermal radiation. In this Perspective, based on the previous works and principal development of passive solar heating and radiative cooling, the corresponding ideal spectral design under different temperature conditions is proposed and highlighted. As demonstrations, we present several examples of different optical spectral designs for realizing passive solar heating and radiative cooling to fit various scenarios. Finally, possible solutions to the current problems and the directions for future development are discussed.

Intelligent radiative thermostat induced by near-field radiative thermal diode

A radiative thermostat system senses its own temperature and automatically modulates heat transfer by turning on/off the cooling to maintain its temperature near a desired set point. Taking advantage of far- and near-field radiative thermal technologies, we propose an intelligent radiative thermostat induced by the combination of passive radiative cooling and near-field radiative thermal diode for thermal regulation at room temperature. The top passive radiative cooler in thermostat system with static thermal emissivity uses the cold outer space to passively cool itself all day, which can provide the bottom structure with the sub-ambient cold source. Meanwhile, using the phase-transition material vanadium dioxide, the bottom structure forms a near-field radiative thermal diode with the top cooler, which can significantly regulate the heat transfer between two terminals of the diode and then realize a stable temperature of the bottom structure. Besides, the backsided heat input of the thermostat has been taken into account according to real-world applications. Thermal performance of the proposed radiative thermostat design has been analyzed, showing that the coupling effect of static passive radiative cooling and dynamic internal heat transfer modulation can maintain an equilibrium temperature approximately locked within the phase transition region. Besides, after considering empirical indoor-to-outdoor heat flux, rendering its thermal performance closer to that of passive solar residential building walls, the calculation result proves that the radiative thermostat system can effectively modulate the temperature and stabilize it within a controllable range. Passive radiative thermostats driven by near-field radiative thermal diode can potentially enable intelligent temperature regulation technologies, for example, to moderate diurnal temperature in regions with extreme thermal swings.

Combination of Passive and Active Solar Heating with Thermal Energy Storage.

This study investigated the impact of individual and combination of different sources of heating (passive solar heating, electric oil-heater, and solar air heater) in a pilot-scale building containing phase change material (PCM) for a potential reduction in energy consumption while maintaining thermal comfort. Unlike most of the recent simulations and modelling studies, this impact was tested experimentally using two identical control and test huts located at the University of Auckland. The control hut was equipped with standard gypsum boards while the test hut had gypsum boards containing PCM (PureTemp 20, PT20). The study found that combining both active and passive solar heating with a temperature-controlled electric oil heater demonstrated the ability to provide significant energy savings and maintain thermal comfort in the test hut, most notably overnight. The suggested combination was tested over different weather conditions and with different temperature constraints to maintain thermal comfort and achieve energy savings ranging from 33% to 87.5%.

Method for determining the optimal value of the specific heat capacity and temperature regime of a short-term heat accumulator of passive solar heating systems with a flat reflector of radiation

The article presents the results of the analysis and generalization of the experience of operating residential facilities with solar heating systems, even a slight accumulation of the daytime excess heat of solar radiation is determined, which can significantly increase the replacement coefficient of the heat load for heating the systems under consideration. An unjustified increase in the capacity of the heat accumulator has been determined that does not give a noticeable increase in the replacement coefficient for the heat load of the system. Studied and developed new and improved existing insolation passive solar heating systems. The article shows the results of the analysis and operation of residential buildings with solar systems, it is determined that a slight accumulation of daily excess heat of solar radiation can significantly increase the replacement coefficient for the heat load on the heating of the systems under consideration.

Annual thermal performance of a passive solar heating system with a Trombe wall with phase change materials

In this work, the potential of a passive solar heating system with a Trombe wall with phase change materials for the climatic conditions of Uzbekistan was evaluated. A dynamic mathematical model has been developed, and validation has been carried out by comparing experimental data. The annual thermal characteristics of a three-room residential building, a three-room residential building with a Trombe wall, a three-room residential building with a Trombe wall with phase-change heat accumulator materials are determined. Calculations show that the specific energy consumption for heating a 3-room residential building is 211 kW·hr/m2·year, and the energy consumption for heating such an object with a Tromba wall installed on the southern wall is 134.3 kW·hr/m2·year, the energy consumption for heating such an object with the Trombe wall installed on the southern wall with phase change materials are 91.8 kW·hr/m2 year. This means that the use of the Trombe wall system will lead to a reduction in energy consumption by at least 36%. The average value of the thermal efficiency of the Trombe wall for the heating period is 37.08%, and the average value of the thermal efficiency of the Trombe wall with phase change materials for the heating period is 52.6%.

Using the utility method - F-scheme in studying the long-term thermal performance of the heat-storage and transmitting wall (Trombe wall)

With the development of building construction engineering and the way to obtain energy from natural sources, the sun has become an important source to avail from thermal energy. In this research, the study of the long-term thermal performance of a passive solar heating system containing an absorber and storage wall was done by using the general design utilizability Method The equations of the mathematical model for this system were solved using the MATLAB environment program. In order to calculate the values of the solar refractive index (f) for this system for the four months of the winter season (November to February). The climatic conditions during these months are the daily values based on the monthly average in the city of Kut (Iraq). Since the best type of wall is the concrete wall, changes are made to this type of wall. A number of variables that affect the performance of the wall have been changed, including in it = wall area, wall thickness. The results showed that increasing the wall area and decreasing the thickness leads to an increase in the value of the solar refractive index, and the maximum values of the solar refractive factor were found during November, and the concrete material is the best performing material among brick and stone material, according to previous studies.

Influence of Photovoltaic Shading on Rooftop Heat Transfer, Building Energy Loads, and Photovoltaic Power Output

Abstract Photovoltaic (PV) modules on building rooftops provide shade from summer heating, leading to a reduction in cooling load during hot seasons. However, PV shading also reduces passive solar heating during winter months, leading to an increase in the building heating load during cold seasons. In this study, the heat transfer performance of an enclosure formed by adjacent PV modules is analyzed for three locations in the United States, comparing the daily heat flux through rooftops for the case of a PV-shaded rooftop as well as an unshaded roof. Several result metrics are developed as part of this work, including the saved energy load (SEL), or the energy conserved by adding PV-shading to the rooftop, and the additional energy load (AEL), or the supplemental building energy required to replace shaded solar heating. Finally, this work calculates the utility factor, being the ratio of SEL and PV power output to AEL as a metric of PV effectiveness. SELs are 5.2, 6.2, and 11.7 kWh/m2 · year for Dayton, Boise, and Phoenix, respectively, while the AELs for the same locations are 1.6, 1.5, and 2.1 kWh/m2 · year. The utility factors for the same three locations are 61, 71, and 79. In general, locations with hot, non-cloudy summers and clear skies in winter see the largest utility factor. Further, it is shown that PV shading can conserve building energy during the winter months by preventing radiative losses to cold winter skies.

Improving the indoor thermal environment in lightweight buildings in winter by passive solar heating: An experimental study

Traditional lightweight building envelopes with constant thermal properties are of small heat capacity and large thermal resistance. Lightweight building envelopes with variable thermal conductivity and variable equivalent specific heat capacity can promote passive solar heat gain for clean heating and improve the indoor thermal environment in winter. In this paper, a real-scale lightweight solar house integrated with flat gravity-assisted heat pipes and PCM (phase change material) was built up, and the indoor heating effects of four forms of the solar house were experimentally studied. The results showed that (1) the heat pipes efficiently transferred solar heat absorbed by the exterior surface of the south envelope into the indoor environment during the day and increased the average daytime indoor air temperature by 3.8°C, but this benefit was not proportional to the area of heat pipes. (2) The PCM effectively stored solar energy during the day and released heat to the indoor environment at night, and the daily range of indoor air temperature was reduced by 8.7°C, with only 81% mass and 33% volume of concrete block, respectively. (3) The solar house increased the effective proportion of solar energy for indoor heating from 8.7% to 57.5% in the form of DHP + PCM house.

Study on the influence of thermo-physical parameters of phase change material panel on the indoor thermal environment of passive solar buildings in Tibet

In this study, an unsteady heat transport numerical model of phase change material (PCM) panel under indoor-outdoor dual thermal disturbance conditions was development by using the apparent heat capacity method, which was employed to evaluate the effect of thermal performance parameters of PCM on the heat storage and temperature regulation capability of PCM panel. Then, a single-space passive solar building located in Tibet was used as a basic building model to study the influence of thermo-physical parameters, such as phase change temperature, thickness and position of PCM panel in composite wall on indoor thermal environment. Meanwhile, the indoor discomfort degree hours and heating energy consumption of the passive solar building with composite wall containing PCM panel were quantitatively analyzed, and the dynamic payback period of PCM investment in Tibet was calculated for economic analysis. The results indicated that the phase transition temperature, thickness and position of PCM panel have a significant impact on its heat storage and temperature regulation capability, and the composite wall containing PCM panel with reasonable thermo-physical parameters could obviously damp indoor air temperature fluctuation and save the building heating energy consumption. Compared with the basic building, applying a 30 mm thickness PCM panel with phase transition temperature of 18 °C on the interior side of the composite wall could reduce indoor discomfort degree hours in studied period (Dec. 20 to Dec. 24) by 74.9% and reduce heating energy consumption in the whole heating period (Dec. 01 to Mar. 01) by 20.76%, respectively. Furthermore, the economic analysis results show that the application of PCM panels in passive solar buildings in Tibet has high economic value, and the dynamic payback period of PCM investment in Tibet with 3% discount rate is 41.29 years, which is lower than the usual service life of a building.

Integration of active solar cooling technology into passively designed facade in hot climates

Sustainable buildings have recently become a global priority. In hot climates, meeting the cooling demand in the sustainable buildings is challenging. To meet this demand in office buildings during summer, the study proposed a holistic configuration of applying passive solar design strategies (PSDSs), and then integrating an active solar cooling technology (ASCT) into the facade. Three hot climates, namely, humid subtropical, hot semi-arid, and hot desert, were investigated using a building energy model. First, four PSDSs, window-to-wall ratio (WWR), glazing type, shading devices, and wall material were sequentially applied to the facade. Then, an absorption chiller driven by a solar thermal collector (STC) was integrated into this passively designed façade. The best tilt angle, area, and dimensions of STC were specified for the main façade orientations. Finally, this study provides design guidelines for integrating ASCT into passively designed façade of office buildings in hot climates. The results reveal that WWR has the highest impact on the cooling demand reduction, whereas the least effect results from the shading devices. The passively designed facade reduces the cooling demand by 43.5%–65.7%. The sloped STC at a tilt angle of 30° is the most efficient option for all orientations except the north where the horizontal STC is considered the best. For these tilt angles, STC area required for meeting the cooling demand ranges from 2.88 m2 to 4.5 m2, corresponding to an STC-to-façade width ratio of 74.1%–84.3%. In the case of the vertical STC, the ASCT is unable to meet the cooling demands.

An evidence-based framework for designing urban green infrastructure morphology to reduce urban building energy use in a hot-humid climate

Urban green infrastructures (UGIs) play an essential role in reducing urban building energy consumption by cooling surrounding areas and shielding buildings from direct solar radiation heat gain. Although the energy-saving effect of UGIs is widely agreed upon, there is a lack of systematic knowledge about how UGI morphology affects urban building energy consumption. Consequently, an effective method to design UGI morphology to reduce urban building energy consumption in urban design is not available. A grading system was proposed to evaluate the strength of evidence for the findings and conclusions in studies that pertain to the cooling and energy-saving effects of UGI. The evidence-based literature review found that strategically designing the morphology of UGI, including its size, shape, location, connectivity, spatial pattern, and configuration, can effectively reduce the air temperature surrounding the UGI area and building energy demand. This study formulated a morphological design framework for UGI as part of the urban design process to reduce urban building energy consumption. Based on the evidence-based answers to the key questions in the framework, design strategies are provided as visual charts and technical principles. The study includes an urban design case in Nanjing, China, which applied this framework to achieve the goal of urban energy savings.

Switchable Surface Coating for Bifunctional Passive Radiative Cooling and Solar Heating

AbstractThe ability to achieve dual‐mode thermal regulation for switchable heating and cooling on a single platform has thus far been challenged by the availability of suitable materials. The materials need to possess both high solar reflectance and high transmittance, necessitating large and small thicknesses in the same coating layer, respectively (i.e., the thickness constraint). Herein, for the first time, a single‐layer coating made in a facile one‐step process is reported, which exhibits rapid switch between high solar reflection (≈96.6%) and high solar transmission (≈86.6%). In the dry state, high solar reflectance and infrared (IR) emittance (>96% from 8 to 13 µm) enable passive radiative cooling, resulting in all‐day near/sub‐ambient temperatures in the demanding weather conditions of the tropical climate. Upon wetting, high transparency in the broadband range (0.3–2.5 µm) allows solar heating, leading to switchable thermal regulation. Such unprecedented performances are achieved through a unique hierarchical porous structure comprising of vertically aligned microscale pores in nanoscale pore matrix. This structure breaks the thickness constraint and broadens its applicability, in particular for seasonal areas with large temperature variation throughout the day.

Aboriginal Community Co-Design and Co-Build—Far More than a House

There is urgent need for a new model to address the housing crisis in remote Australian Indigenous communities. Decades of major government expenditure have not significantly improved the endemic problems, which include homelessness, overcrowding, substandard dwellings, and unemployment. Between 2017–2020, Foundation for Indigenous Sustainable Health (FISH) worked with the remote Kimberley Aboriginal community, Bawoorrooga, by facilitating the co-design and co-build of a culturally and climatically appropriate home with community members. This housing model incorporates a program of education, health, governance, justice system programs, and land tenure reforms. Build features incorporate sustainable local/recycled materials and earth construction, and ‘Solar Passive Design’. The project faced challenges, including limited funding, extreme climate and remoteness, cultural barriers, and mental health issues. Nevertheless, the program was ultimately successful, producing a house which is culturally designed, climatically/thermally effective, comparatively cheap to build, and efficient to run. The project produced improvements in mental health, schooling outcomes, reduced youth incarceration, and other spheres of community development, including enterprise and community governance. Co-design and co-build projects are slower and more complex than the conventional model of external contracting, but the outcomes can be far superior across broad areas of social and emotional wellbeing, house quality and comfort, energy consumption, long-term maintenance, community physical and mental health, pride, and ownership. These factors are essential in breaking intergenerational cycles of poverty, trauma, and engagement with the justice system. This paper provides a narrative case study of the project and outlines the core principles applied and the lessons learned.

New paradigms in bioclimatic design toward climatic change in arid environments

Energy consumption in buildings has increased exponentially since the industrial revolution. Given this scenario, the Argentinian government has proposed to implement energy efficiency measures in the public and private sectors with the aim of reducing energy demand by 10.3% by 2030 [72]. The Rational and Efficient Energy Use Program (PROUREE) aims to reduce consumption levels in buildings of the National Public Administration (NPA), assuming an exemplary role before the rest of the society [73]. In this context and, as a first instance, this study aims to know the performance of a bioclimatic building of the NPA currently constructed in an arid climate with high irradiance, when exposed to the consequences of CC. After validation in Energy Plus with data measured in situ, and considering that these types of buildings are replicated in the region, a simple design strategy is proposed to increase thermal, daylighting, and energy performance by 2099, without changing the project: the building was rotated 180° (case B), allowing to reduce direct solar gain, increase exposure to the strongest summer breezes and homogenize daylighting. The findings suggest that the implementation of these passive design parameters through an integrated analysis (energy, daylighting, and thermal comfort), can reduce energy consumption by 33.82 Kwh/m2, which represents 51.82% of the total energy consumption of the building in arid climates with high solar irradiance (Measured case = 65.26kwh/m2. Improved case = 31.44kwh/m2). These obtained reference values will serve as a source of reference for designers and policymakers to anticipate climate change and counteract the effects of CC through energy efficiency.

Design of the passive solar house in Qinba mountain area based on sustainable building technology in winter

This paper aims to make better use of solar energy through the application of passive design concept. The test results show that the average temperature of the case building is about 7.2 °C, indicating that the indoor thermal comfort of rural houses in Qinba mountain area is poor in winter For the purpose of improving the indoor thermal comfort of rural buildings in this area, the simulation is carried out by using ANSYS. CFX software, and the effects of direct benefit solar house and additional solar house are compared. The results reveal that adding additional solar space can achieve better results. The average temperature of the first floor is increased by 1.1 °C ∼1.4 °C and that of the second rises by 0.7 °C ∼1.1 °C. Compared with the original building, the energy saving rate of the building with additional solar space in the heating period is more than 50%. Therefore, the additional solar house can be promoted as a low-energy heating measure for rural buildings in this area. The promotion of additional solar house will certainly play an important role in improving the indoor thermal environment of residential buildings reducing energy use in building and promoting green buildings.

Erratum to: Heating load reduction characteristics of passive solar buildings in Tibet, China

Erratum to: Heating load reduction characteristics of passive solar buildings in Tibet, China

Passive and Active Solar Systems in Eco-Architecture and Eco-Urban Planning

The subject of this article is a presentation of multi-scale passive and active solar and shading systems in urban areas. This research assumes the hypothesis that insolation systems are interdependent and that their integration in urbanized space affects the city biome. Attention has been paid to the role of innovative solutions used in the field of ur ban insolation, such as heliostats in the development of future eco-architecture and eco-urban planning. This research has been based on the assumption that only by taking into account the close symbiosis between an energy-efficient building and its appropriate insolation, in combination with properly planned surroundings, it is possible to actually achieve the principles of sustainable development in the urban fabric. The analytical part concerns detailed investigation into solutions in the field of passive and active solar architecture and urban planning, regarding both insolation and shading. The article analyzes source materials, includes descriptions of case studies, and presents a comparative analysis of passive and active solar and shading systems. The research method, both empirically and theoretically, is closely related to case study analysis and has involved collecting and systematizing data on micro and macro “solar” design systems.