This paper introduces a novel Gaussian process approach for systems with unknown disturbances with quasi-periodic patterns to enhance the performance of a robust economic model predictive controller. ...A self-tuning kernel is proposed to substitute the periodic kernel used in the hybrid Gaussian process models in order to predict forthcoming disturbances more accurately while demanding a shorter training horizon. The proposed method is applied to a domestic solar thermal system, in which the hot water demand has a recurrent pattern, yet there is a slight variation daily. The simulation results demonstrate that the proposed controller has a reliable and precise prediction of future demand, and therefore it is able to manage the solar thermal system properly under various hot water load scenarios. Specifically, the proposed controller yields more than 5% improvement over a proportional–integral–derivative controller in terms of energy saving associated with the electricity usage for an auxiliary heat source.
•Novel approach for systems with unknown quasi-periodic disturbances•Introduction of a self-tuning kernel to enhance prediction accuracy•Application of the method to a domestic solar thermal system
Phase change materials are widely used as thermal capacitors in solar thermal systems. The phase change materials with carbon materials could directly absorb the solar energy and transfer to water ...for building heating, while are rarely reported. In this work, an Ethylene-Propylene-Diene Monomer based phase change material with expanded graphite is prepared. The photo-thermal performance of the phase change material is investigated with combined experimental and numerical method. The SiO2 aerogel is first used as the thermal insulator in the solar thermal systems with the high transmittance and low thermal conductivity. The effect of the phase change material height and tube passes number on the photo-thermal performance of the phase change materials are calculated. The results show that the new material has a tensile strength of 3.6 MPa, enthalpy of 126.8 J g−1，and thermal conductivity of 1.106 W m−1 K−1. The phase change material with SiO2 aerogel could resist heat lost on the surface. The phase change material has good photo-thermal performance in solar thermal systems, could heat more than 200 L of hot water at daytime.
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•A flexible phase change composite with enthalpy of 126.8 J g−1 and a thermal conductivity of 1.1 W m−1 K−1.•The phase change composite has tensile strength of 3.6 MPa.•The SiO2 aerogel is first used as the thermal insulator for photo-thermal conversion.•This phase change composite could heat more than 200 L of hot water at daytime.
Modern technological developments and intensive research efforts have primarily fueled the worldwide interest in solar energy. The risks that conventional energy sources pose to both human health and ...the environment are what have driven this change. Various solar energy solutions are available today, such as solar collectors, PV panels, solar ponds, solar chimneys, solar stills and Trombe walls. The current article aims to study the impact of porous media on the performance of Thermal solar systems, including steel foam, aluminium foam, wood, gravel, metal foam, metal balls, and glass balls. The study reviewed the most important published research that conducted analytical and experimental studies to maintain the low operating temperature as much as possible because it had a significant impact on improving efficiency, as one of the proposed methods is the use of porous media and through the results obtained indicate a significant increase in efficiency in one of the studies the addition of porous medium led to a decrease in the temperature of the photovoltaic cell by 5 to 25 degrees Celsius and the overall efficiency increased from 10% to 28%. In contrast, the electrical efficiency increased from 1% to 4%. The result of another experimental work was a decrease in the temperature of the device between 3.9 and 18.3, an increase in energy consumption by 6.6%, improved Electrical efficiency by 2.7%in another research, the solar energy efficiency of a solar distiller using oyster shells as a porous medium was 0.73% and 1.2%.
Ionanofluids (INFs) are novel types of heat transfer fluids consisting of fine nanoparticles suspended in ionic liquids (ILs). They exhibit improved thermal properties for various applications, ...especially solar concentrators. In this work, for the first time, molecular dynamics (MD) simulations are used to investigate the thermophysical, structural, and dynamical properties of a specific INF composed of the HMIMBF4 IL and SiC nanoparticles at various temperatures and nanoparticle volume fractions.
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•MD simulations were used to investigate the properties of HMIMBF4-SiC INF.•Increasing nanoparticle led to higher thermal conductivity, viscosity and density in INF.•F atom of anion and HR atom of cation have strongest correlations with nanoparticles.•Nanoparticle addition stabilize INF and decreasing ions' mobility.•Dynamics of hydrogen bonds were accelerated with increasing nanoparticle volume fraction.
Ionanofluids (INFs) are a novel type of heat transfer fluids consisting of fine nanoparticles suspended in ionic liquids (ILs). They exhibit improved thermal properties, including enhanced thermal conductivity, non-volatility, and non-flammability, making them ideal candidates for various applications, especially solar concentrators. In this work, for the first time, molecular dynamics (MD) simulations are used to investigate the thermophysical, structural, and dynamical properties of a specific INF composed of the HMIMBF4 IL and SiC nanoparticles in the temperature range of 298.15–338.15 K and at different nanoparticle volume fractions, i.e. 1.10 %, 2.27 %, and 3.47 %. Radial distribution functions (RDFs) revealed a strong structural correlation between the fluorine atoms of anion and the HR atom of the cation ring and also with the carbon and silicon atoms of the nanoparticle. The results showed that with increasing the volume fraction of nanoparticles, ions tend to have more interactions with nanoparticles, and the interactions between the anions and cations decrease. As a result, the thermal conductivity, viscosity, and density of ions in the INF increases. Finally, we made some comparisons between the simulated thermal conductivities and viscosities of the studied INF with classical models. The results showed that, in some cases, the simulation results were even better than some models compared to the experimental values. The insights obtained from this study not only enhance our understanding of the structure and dynamic behavior of the INF, but also can contribute to the development of innovative materials and more efficient solar thermal systems.
This work studies the relative influence of the constructive characteristics of thermosiphon factory made solar heating systems of components such as absorber type, collector area, thermal insulation ...of both collector(s) and tank, tank volume and volume/area ratio, on the annual energy production, the annual efficiency and the solar fraction. The research has been conducted on 28 systems available in the market, tested according to Standard ISO 9459–5:2007 and simulated fo different European reference locations (Athens, Davos, Würzburg and Stockholm) according to Standard EN 12976–2:2019. The results show that reduced volume has a marked influence on the energetic and efficiency behaviour of these systems. In particular, for reduced volume values greater than 0.8, the constructive characteristics have high influence on systems behaviour. On the contrary, for reduced volume values lower than 0.8, all tested systems have a similar behaviour at the same location. The results found in this study allow optimizing the design of TSWHS, as well as selecting a specific system according to the location and a daily load volume.
•The performance of thermosiphon solar systems according ISO 9459–5:2007 is evaluated.•The relative influence of constructive parameters of their performance is quantified.•Their best performance is achieved for reduced volume ranging from 1.0 to 1.6.
This study investigates an integrated energy system designed to supply 100% heat and power to a remote application, renewably. The system comprises a solar photovoltaic (PV) system with ...hydrogen-based energy storage (SH), a fuel cell heat recovery arrangement, an electric inline heater (powered by the PVs), and a solar thermal system (ST), altogether operating as a renewable combined heat and power solution. A theoretical simulation model is developed in MATLAB to conduct this study. The addition of the inline heater (powered by the PVs) resulted in improving the overall reliability of this integrated renewable energy arrangement from ∼95% to 100% with no additional costs. Additionally, the system is competitive against diesel generator (for power supply) and gas hot water system that is mostly used conventionally in remote areas.
•A solar-hydrogen CHP integrated with solar-thermal collectors and inline heater.•Multi-objective sizing optimisation using genetic algorithm performed on the system.•100% reliability for electricity and hot water demand guaranteed at no additional cost.•Advantageous operation of the inline heater in the whole system.•Effective and economic system for use in remote areas.
The trend of introducing solar thermal systems (STSs) in process industries has resulted in a new energy paradigm– an interactive platform where there are economic benefits and motivations to address ...sustainable development. On the other hand, this paradigm has also introduced fluctuations and uncertainties not previously seen on the energy system, and is challenging the industry. Industrial STSs are composed of large number of interacting, nonlinear and uncertain subsystems and, therefore are complex systems. This complexity of heterogenous, stochastic, and dynamic behavior make designing of industrial STSs as well as evaluation of their management strategies challenging tasks for the existing tools. In an attempt to support integration decisions, always inefficient and insufficient, machine learning (ML) is leveraged in this research. Following the ML approach, some important findings were made. Firstly, it permits for different releases of the same/different module, which can be easily embedded, coupled exogenously or run in parallel. Thus, the operation-based design approach, both for process and supply level integration of STSs, were scalable and tractable. Distinguished from past work, the approach also allowed testing of an improved STS sizing scheme, while at the same time, enabling optimization of its control concept for adaptive and flexible operation. In the considered case study, inclusion of time-varying heat demand, process temperature and solar irradiation in STS design reduces over-dimensioning by 10–30%. Furthermore, optimizing the control concept of the overall system led to improved energy efficiency of solar field and storage respectively by 23.7% and 8.3% over the state-of-the-art methods.
•ML is used as data and model interface while developing scalable modules of industrial solar thermal systems (ISTSs).•The modules allow integral and multi-time scale simulations.•Operation-based design is used to optimize both the configuration and control concept.•The ML approach led to improved sizing and overall solar gain efficiency in STS.
•Analysis of a flat-plate solar collector with three flow of liquid fluid.•Liquid fluid outlet temperature prediction with ANN model for bomb three flows.•Yield comparison of proposed ANN model, HWB, ...ISO 9806 respect to energy balance.•Deviations when f-chart method is applied with HWB coefficients of different flows.•Deviations produced when ISO 9806 model is applied with different flows.
The operation of a flat-plate solar collector using three different working fluid flows (water, i.e. 1, 1.6, 2 L/min) has been modelled using the artificial neural networks (ANNs) of computational intelligence technique. The ANNs model has been built at the entrance to predict the outlet temperature in the flat-plate solar collector using measured data of solar irradiance, ambient temperature, inlet temperature and working fluid flow. The results obtained conclude the method is accurate with the three flow rates of the working fluid (water) (e.g. RMSE = 0.1781 °C and R2 = 0.9991 for an ANN prediction of the outlet temperature of the working fluid with 2 L/min test and RMSE = 0.0090 0,1 and R2 = 0.7443 as a performance prediction test of 1 L/min), flexible when choosing the variables used and easy to apply to any solar collector. The Hottel-Whillier-Bliss (HWB) and the international standard ISO 9806 solar collector models are also described and applied using the data obtained in the tests performed on the flat-plate solar collector. The deviation that occurs with the three different flows of the working fluid (water) used, have been verified and also their repercussion when they are applied in the f-chart method.
Buildings were recognized as large energy consumers, and they represent great potential for energy savings through the implementation of a wide range of measures for improving of energy efficiency. ...Through numerous directives and procedures that have been adopted over the past 30 years, the building sector is committed to the use of renewable energy sources. Among the solutions to the global energy problem, as well as the problem of excessive emissions of greenhouse gases, primarily CO2, which directly affect global warming, the use of solar energy is one of the most acceptable environmental solutions. In the recent years, a new aspect of the application of solar systems in the construction sector has been developed - their integration into the building envelope. This paper presents an overview of the latest research related to solar thermal systems integrated into the building envelope. The current status in the field of technology of solar thermal systems integrated into the building envelope is presented in paper. Different types of these systems that can be integrated into the building envelope are described, and their basic performance is presented. Possible applications of solar thermal collectors in different parts of the building envelope (facade, roof, overhangs, balcony) are also described and presented. By applying these systems, it is possible to significantly influence to the reduction of energy consumption in the building sector, as well as environmental pollution by reducing CO2 emissions.
Abstract
Durch die Auswirkungen des fortschreitenden Klimawandels und den daraus resultierenden Forderungen nach einem klimaneutralen Gebäudebestand ist es von großer Bedeutung, einen Großteil des ...Energiebedarfs durch die Nutzung erneuerbarer Energien decken zu können. Dazu wird im Rahmen eines Forschungsprojekts ein neuartiges Wärmespeicher‐ und Energieerzeugungssystem für Gebäude entwickelt, welches die Energieerzeugung und ‐speicherung in autarken „Energiepfählen“ anstrebt. Ziel der vorliegenden Analyse war die Auswertung eines ersten Prototyps, der im Zuge des Projekts entwickelt und experimentell untersucht wurde. Bei der Untersuchung standen die Energiegewinnung, die Energieeinspeicherung und die Dauer der Entladung des neuen Systems im Vordergrund. Es konnte gezeigt werden, dass die Energiegewinnung des Prototyps gut funktioniert und vergleichbar mit bestehenden Solarthermiekollektoren ist. Allerdings wurde mit Unterstützung einer Gebäudesimulation gezeigt, dass die Energieeinspeicherung nicht ausreicht, um den gesamten Nutzenergiebedarf für die thermische Konditionierung eines Beispielgebäudes wirtschaftlich durch den Energiepfahl zu decken. Die Untersuchungen zeigen, dass der Prototyp großes Potenzial besitzt, aber eine Weiterentwicklung notwendig ist, um eine wirtschaftliche Option darzustellen.
Translation abstract
Energy recovery and energy storage of the prototype of a novel heat exchanger and energy generation system
Due to the effects of the advancing climate change and the resulting demands for a climate‐neutral building stock, it is of great importance to be able to cover a large part of the energy demand by using renewable energies. To this end, a new type of heat storage and energy generation system for buildings is being developed as part of a research project, which aims to generate and store energy in self‐sufficient “energy piles”. The aim of the present analysis was to evaluate a first prototype, which was developed and experimentally investigated in the course of the project. The investigation focused on energy generation, energy storage and the duration of discharge of the new system. It was shown that the energy production of the prototype works well and is comparable to existing solar thermal collectors. However, with the support of a building simulation, it was shown that the energy storage is not sufficient to economically cover the entire useful energy demand for the thermal conditioning of an example building by the energy pile. The investigations show that the prototype has great potential, but that further development is necessary to make it an economical option.
