Passive Space Heating Research Articles

Fabrication and evaluation of polyurethane supported form‐stable PCMs

AbstractThe current research is oriented towards the development and assessment of the properties of the form‐stable phase change materials (PCMs), comprising of the thermoset polymer matrix (polyurethane, PU) enclosing capric acid (CA) as an active thermal energy storage (TES) component. The Fourier Transform Infrared Spectroscopy (FTIR) and Field‐Emission Scanning Electron Microscopy (FE‐SEM) have been used to characterize the chemical nature and morphological details of the developed PU‐based PCMs (PUPCMs). TES attributes and thermal stability of the resultant PCMs are evaluated by thermo‐analytical techniques such as Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). A thermal reliability test has been conducted to determine the phase change efficiency of the prepared PCMs. PUPCMs have been found to be suitable for TES applications, such as passive space heating or cooling building applications.

Study on impact of photovoltaic power tracking modes on photovoltaic-photothermal performance of PV-PCM-Trombe wall system

Due to the lack of research on the impact of photovoltaic (PV) power tracking methods on the performance of Building-Integrated Photovoltaic-Thermal (BIPV/T) systems, this study comparatively analyzes the photovoltaic-photothermal performance of the PV-PCM-Trombe Wall system operating in Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT) modes during winter passive heating conditions. Additionally, the study investigates the influence of these modes on the thermal characteristics of buildings. The results indicate that the MPPT strategy achieved a PV efficiency of 15.50 %, while the PWM strategy resulted in a significant reduction to 12.72 % (a decrease of 2.78 % compared to MPPT). Importantly, both strategies effectively utilized solar energy for passive space heating without noticeable differences in photothermal performance. Furthermore, the study observed that the upper part of the PCM plate reached higher peak temperatures earlier in the vertical dimension. Experiment A exhibited peak temperatures ranging from 33.57 °C to 34.76 °C, while Experiment B had a wider range of 27.99 °C to 36.10 °C. Minimal temperature variations were observed across the PCM plate in the thickness direction, measuring only 0.60 °C in Experiment A and 0.70 °C in Experiment B. These research findings provide valuable insights into the roles and impacts of different PV power tracking strategies in PV-PCM-Trombe wall systems.

A scoping review on recent advancements in domestic applications of solar thermal systems

The rapid growth in smart technology and green energy contributing crucial role in taking our homes into next level. Meanwhile the solar powered thermal systems (STS) are much desired for energy conservation and management of houses. Domestic application of STS will not only reduce electricity consumption but also reduce carbon emission. This paper gives a scoping review on role of various types of STS namely, solar water heating, solar active and passive space heating and cooling, solar thermal water pumping, solar cooking, solar drying, solar distillation, solar green house, solar photovoltaic thermal systems (PVT) and solar thermal energy storage systems in domestic applications. The recent advancements with respect to each type of STS is outlined. Starting from various collectors and materials for STS, each system’s working principle and technological advancements in the view of adopting it to domestic applications are discussed in detail. Also, performance evaluation and role of each different STS in home application is elucidated. The research gaps and potential barriers for adopting STS for domestic homes are explored.

Annual performance analysis of a dual-air-channel solar wall system with phase change material in different climate regions of China

Applications of phase change material (PCM) in buildings have significant energy-saving potential. In this work, a dual-air-channel solar wall system with PCM is proposed, which has the following main functions: electricity generation, hot water supply, passive indoor space heating and ventilation cooling. Continuous experimental tests were conducted through two hot-box rooms in Hefei to confirm the energy saving effects of the system. Mathematical model of the system is established and validated against the experimental results. With the validated model, the annual performance of the system in three selected cities (Urumqi, Beijing and Hefei) is investigated. Annual electricity generation and average electrical efficiency of the three cities are 179.67 kWh, 179.21 kWh, 119.28 kWh and 11.22%, 10.67%, 11.06%. Annual energy saved are 863.24 kWh, 770.53 kWh and 576.43 kWh. Parametric analyses are also conducted. Proper increase of PV coverage is beneficial to the comprehensive performance of the system. Decrease of the thickness ratio of the outer and inner channel and increase of depth-to-width ratio of the channel can both enhance the thermal performance in heating season. The selection of melting temperature and thickness of PCM should be based on the weather condition of the region where the system is applied.

Development and investigation of microencapsulated caprylic acid ‐based phase change materials for thermal energy storage applications

The present study is focused on the preparation of microencapsulated phase change materials (Micro-PCMs) for thermal energy storage applications. These Micro-PCMs capsules comprise of a renewable material, caprylic acid (CA), as core latent heat storage material, confined inside the polymethylmethacrylate (PMMA) shells and are produced by the suspension-like polymerization method. The prepared Micro-PCMs are characterized by FTIR, SEM, and Particle Size Analyzer. The phase change properties, including melting and crystallization temperatures, and latent heats associated during phase change are determined by DSC and are reported as 14.3 ± 0.2°C, 9.7 ± 0.4°C, and 98.7 ± 1.5 J/g, 99.0 ± 1.7 J/g, respectively. The TGA results indicated that the synthesized Micro-PCMs exhibit a two-step degradation pattern and have good thermal stability. The T-History test is carried out to study the thermal energy storage/release time of the Micro-PCMs. Thermal cycling test has been performed to check the thermal reliability of the microcapsules. The synthesized Micro-PCMs are good contenders for latent heat absorption and can play a vital role in the area of thermal energy storage (TES) applications, such as passive space heating or cooling applications, smart textiles, and thermo-responsive functional coatings.

Design and performance of an off-grid solar combisystem using phase change materials

An off-grid solar combisystem with built-in latent heat storage unit is designed and developed for active space and water heating during day and passive space heating during night. A flat plate solar thermal collector and a photovoltaic module with a Li-Ion battery power the fully autonomous system. The optimized solar combisystem design comprises a heat transfer loop for simultaneously charging phase change material and water. The combisystem can consistently heat the water to about 45 °C during a normal sunny day and retain thermal energy for two days. In addition, the system can also heat the space to a comfortable zone during day and from dawn to dusk along with water heating during winter season, even in fluctuating weather condition. The average energy saving ratio and energy saving obtained during winter season space heating are about 56 % and 4.4 kWh, respectively. The solar combisystem performance shows that the average energy saving ratio and energy saving obtained for space heating were ~ 93% and ~ 2.8 kWh, respectively. It was observed that the air temperature in the phase change material integrated space unit (area coverage ~60%; melting point: 23 °C) remain ~ 4 to 6 °C cooler than corresponding without phase change material integrated space unit. The long-term performance evaluation of the solar combisystem shows that the off-grid system can efficiently maintain the space temperature in a comfortable zone during cooler and warmer season along with water heating for residential application. It is evident that the off-grid phase change materials integrated solar combisystem can lead to significant energy saving in residential buildings both in colder and warmer weather conditions.

An experimental study of a built-middle Photovoltaic Trombe wall system

This paper proposed a PV-integrated Trombe wall system (PVTW) with the photovoltaic panel installed in the middle of air channel, named as built-middle photovoltaic Trombe wall system (PVMTW). The system has multiple functions: such as photovoltaic power generation, passive space heating, heat preservation and heat insulation. A series of tests were carried out in winter between the comparable hot- boxes to investigate the thermal and electrical performance of the PVMTW system. The results showed that the average electrical efficiency and thermal efficiency were 0.12 and 0.40, respectively, under the natural convection mode. The total efficiency of the PVMTW system was calculated to be 0.587, which is 11.4 % higher than that of traditional PVTW system with the solar cells laminated on the glass cover.

Experimental Nearly Zero Energy Building with Green Technology – Renovation Pilot through Passive House Expertise

The paper presents the preliminary planning of a demonstration pilot for exemplary renovation of an existing building (“Solar House 1 – Campina”) towards nZEB level using Passive House principles and technologies. The “Solar House” was one of the lighthouses of solar energy developments in the ‘80s in Romania, being built in 1977-1978 in Campina (Centre-South Romania) and represented an experimental building using innovative solar technologies for DHW preparation, active and passive space heating. The decision of transforming the existing building in a demonstration pilot nZEB with green materials was taken and the feasibility study is currently underway. The pilot aims to analyse and test, the cost effectiveness of Passive House (PH) technologies integration in a deep renovation process with the view to achieve the fixed nZEB levels, as an exemplary case study demonstrating the benefits and feasibility of applying PH principles and energy performance evaluation in real context. Both approaches of applying the renovation standard EnerPHit and targeting Passive House criteria are discussed together with the nZEB targets, while the analysis of technical (energy performance) and economic (total costs) feasibility is presented. The proposed building will act as a training and consultancy centre in Campina - created as a model for achieving greater energy efficiency and environmental responsibility in Romania.

A new design of a solar water storage wall: a system-level model and simulation

Some configurations have been proposed as passive solar wall, but nearly all of them suffer from common shortcomings such as high heat loss flux and low thermal capacity. In this paper, a modified design for building passive solar wall is proposed and a detailed computerized model for its dynamic behavior was developed as a triplet (S, Q, M) from first principles and empirical equations, such that the designer is able to alter any of the variables. Hence, the wall-room properties can be adjusted to improve the wall performance. In this model, S is a solar water wall which is designed on the south wall of a building with a water storage tank as the sensible thermal storage placed inside to passively heats the space with controlled heat transfer and a sufficiently sized storage. Also, Q is a question relating to S which is the performance evaluation of the proposed system including annual and monthly performance along with the room and storage temperatures. Finally, M is a set of mathematical statements $$\hbox {M}=\left\{ {\Sigma \_\hbox {1},\Sigma \_\hbox {2},\Sigma \_\hbox {3},\ldots } \right\} $$ which can be used to answer Q. The statements M are based on the lumped capacitance approach which utilizes solar optocalorics, solar thermal conversion and convective heat transfer to simulate passive space heating of a small building. A code was developed to solve the problem and to evaluate parametric sensitivity for design features. A new TrnSys model was introduced and the code results were compared with TrnSys outcome.

Experimental study of a building-integrated dual-function solar collector system

As a novel building-integrated solar thermal system, a building-integrated dual-function solar collector system are designed with two operating modes: passive space heating mode in cold winter and water heating mode in warmer seasons. Based on a long-term experimental test, the paper investigates the performance of the system operating under these two modes. Experimental results indicated that the characteristic thermal efficiency of the system working at the water-heating mode with natural circulation was calculated to be 40.5% and at the space-heating mode the functional relationship between the temperature difference of the indoor air and the solar radiation on the absorber plate of the solar collector can be expressed as two linear equations.

Reducing unwanted thermal gains during the cooling season for a solar heat pipe system

The heat pipe augmented solar heating system significantly reduces heating loads relative to other conventional passive space heating systems. However, thermal gains from the system during the cooling season increase cooling loads and tend to increase overall space conditioning loads. The effectiveness of several design modifications and control strategies for the heat pipe wall to reduce unwanted gains was investigated. Computer algorithms were used to simulate four different unwanted gains reduction mechanisms: shading, an opaque cover, a mechanical valve, and switching the elevations of the evaporator and condenser sections to provide heat transfer out of the room during the cooling season. For each mechanism, three different control strategies were evaluated: (1) Seasonal control, for which the prescribed mechanism was deployed at the beginning and removed at the end of the cooling season, (2) ambient temperature-based control, for which the mechanism was deployed if the forecast for the next hour was greater than 18.3°C (65°F), and (3) room temperature-based control, for which the mechanism was deployed if auxiliary cooling was required for the previous hour. For the seasonal strategy, a season determination (SD) parameter was defined and results suggested that SD may be a ‘universal’ parameter that can be applied across a range of climates for quick cooling season assessment. The heat pipe system performed best with ambient temperature-based control strategy, and the cover and valve were the best single mechanisms. Experiments on a full-scale heat pipe wall prototype using valve and cover control mechanisms confirmed significant reductions in unwanted thermal gains with little to no increase in room temperature during the testing periods.

Numerical simulation of combined solar passive heating and radiative cooling for a building

While solar energy can be utilized for passive space heating, efficient passive space cooling is achievable through lower temperature ambient thermal sources. In this study, a model was proposed for the combined solar heating and radiative cooling and a MATLAB code is developed to simulate combined space heating and cooling of a small building in Louisville, Kentucky. The combined system consists of the glazing/transparent insulation subsystem and the thermal storage subsystem. The space is passively heated and cooled by means of natural convection from the surfaces of the storage subsystem where the storage tank is heated by solar radiation and cooled by night sky radiation as a low temperature thermal source. The model for this system consists of several transient energy balance equations based on the lumped capacitance approach and it has been implemented utilizing MATLAB. Using the aforementioned system and the auxiliary heating/cooling units, the room temperature can be kept within the prescribed comfort range. The simulation is carried out to find the monthly and annual solar fraction, required heating demand, auxiliary heating demand as well as the unwanted heat gain during heating months. Also, the radiative cooling fraction, required cooling demand and auxiliary cooling demand during cooling months are obtained. The optimum value for transparent layer absorptivity was found to avoid unwanted heat gain. Parametric sensitivity was evaluated for material and design features related to the combined system. Simulation results for temperature profiles of the room and storage tank are also illustrated.

Heating season performance of a full-scale heat pipe assisted solar wall

Previous computer simulations and bench-scale experiments showed that the heat pipe assisted solar wall had the potential for significantly improved performance relative to conventional passive space heating systems. To further test this potential, a full-scale prototype of the heat pipe system was designed, built and installed in a classroom on the University of Louisville campus in Louisville, KY. During the spring heating season of 2010 (January–April), maximum daily peak thermal efficiency was 83.7% and average daily peak thermal efficiency was 61.4%. The maximum hourly average room gain achieved during the season was 163W/m2. On days with good solar insolation, the thermal storage was heated to temperatures sufficient to provide significant energy to the classroom – even during the coldest days of the season. During the longest period (4 days) of low insolation during the season, average hourly heat delivery to the room from storage remained positive, and was never less than 16.6W/m2. During good insolation days following a period of consecutive low insolation days, thermal storage temperature was quickly restored to levels comparable to those obtained during consecutive good insolation days. Estimated heat removal factor * transmittance absorptance product FR(τα) and heat removal factor * overall loss coefficient FRUL values for the system were comparable to those for glazed liquid active collectors.

Energy Performance of a Building-Integrated Dual-Function Solar Collector in Passive Space Heating Mode

The building-integrated dual-function solar collector has two independent operating modes: passive space heating mode in cold days, and solar water heating mode during hot days such as the summer. The novel system avoids summer overheating in hot climate and water-freezing in cold climate, meanwhile remains low operating cost as a passive solar heating system. In this study, the energy performance of the novel system in passive space heating mode was studied by experiment and numerical simulation. The experimental and numerical results show that the system performed a high ability in utilizing solar energy for building when working in passive space heating mode and the value of the transient operating efficiency generally kept as a constant.

Modelling and validation of a building-integrated dual-function solar collector

A novel building-integrated solar thermal system known as building-integrated dual-function solar collector is proposed. The system has two independent operating modes: passive space heating mode and water heating mode, and it uses the following criteria to select the operating mode that during cold days such as winter days it works in passive space heating mode, but in warm seasons such as summer it works in the water heating mode. A testing system was established, and it performed in thermosiphon water heating mode for water heating. Two dynamic numerical models were, respectively, presented for the two operating modes of the testing system. The experimental data on the testing system were used to validate the two models. The results show that the numerical model for the system in the thermosiphon water heating mode can give a fairly good prediction and the model for the system in the space heating mode also gives a good prediction.

Thermal characteristics of a building-integrated dual-function solar collector in water heating mode with natural circulation

As a modified building-integrated solar thermal system, building-integrated dual-function solar collector here proposed is able to provide passive space heating in cold winter, and water heating in warm seasons. In this study, evaluations were made on this modified collector system for the warm period operation under the water heating mode with natural circulation of flow. A dynamic numerical model has been developed and validated by experimental data. Based on practical air-conditioned room design conditions, numerical analysis was performed to study the water heating performance, as well as to compare the solar transmission through building facade in different seasons with or without its presence. The results show that when working in the water heating mode, the system performs well in providing services hot water in the warm seasons without bringing in summer overheating problem.

Effect of a dual-function solar collector integrated with building on the cooling load of building in summer

As a building integrated solar thermal system, the dual-function solar collector integrated with building works for passive space heating in cold winter season, and for water heating in warm seasons. In this paper, the study is made on the dual-function solar collector integrated with building when it works in water heating mode with natural circulation. The coupled model of the collector and building’s environment is established and validated. A numerical simulation is achieved to show the thermal effect of the novel system on the building in summer. By comparing with the cooling loads of the rooms with or without the novel collector in summer, the results show that when in summer, the novel solar system is available for serving hot water, and it does not have the summer overheating problem, and can even improve the thermal environment of its building slightly.

A numerical and experimental study of a dual-function solar collector integrated with building in passive space heating mode

A newly designed solar collector named dual-function solar collector is proposed. The dual-function solar collector integrated with building can perform in two different modes: working as a passive space heating collector in cold sunny days such as in winter, or working as a facade water heating collector in hot days such as in summer. An experimental study has been carried out to investigate the performance of the novel system in space heating mode, whilst, the dynamic numerical model has been established and validated. The experimental and numerical results show that during the period of the measurement from 9:00 to 17:00, the mean indoor temperature was up to 24.7°C while the mean ambient temperature was only 4.8°C, and a temperature stratification was present in the room. Moreover, a numerical study on the effect of optical property of coatings has been carried out.

Modelling and simulation of elements for solar heating and daylighting

Through the development of highly efficient transparent insulation materials (TIM), new opportunities are appearing in the field of daylighting and passive solar space heating. The simulation program WANDSIM, developed at the Fraunhofer-Institut für Solare Energiesysteme (ISE), models the dynamic performance of three important elements for daylighting and passive solar space heating: window glazing; transparently insulated masonry; transparently insulated glass wall. Selected simulation results of each type are represented and compared under thermal and daylighting aspects. The advantages of the transparently insulated glass wall, a new combined passive space heating and daylighting system, in economy and comfort are verified.

Operation of a multistory solar building under adverse climatic conditions

Architectural, urban, thermal, economic and industrial aspects of a multistory solar building have been investigated when operating under adverse climatic conditions in Turkey. Active, passive and hybrid space heating systems which could be adapted to the building structure have been studied comparatively. The magnitudes of the design elements and the technical-economic results of the selected hybrid system have been determined. A domestic hot water installation has been also described.