•Integration of a PCM fluidized-bed storage in solar air systems for building heating.•Alternative to the usual energy storage based on packed beds of rocks or pebbles.•Reducing the ...charging/discharging times in comparison with a packed bed.•To promote the more widespread use of solar air heaters for heating of buildings.•Even small solar radiation levels enable operation of the air heating system.
This work studies the integration of a fluidized bed energy storage unit containing Phase-Change Materials (PCMs) into solar air-based systems for heating of buildings. The use of a PCM fluidized bed energy storage unit in air systems offers an interesting alternative to the usual energy storage media based on packed beds of rocks or pebbles because it enables faster charging (or discharging) of the thermal energy storage (TES), associated with high energy densities provided by the latent heat of the PCM. The airflow rate that passes through the solar collectors is sufficiently high to provide satisfactory fluidization of the bed, achieving high heat transfer coefficients.
The results of the simulation study conducted on the proposed air system show that the system can successfully supply a significant part of the heating requirements of a single-family house in locations with mild winter conditions, such as Barcelona and Madrid, where a TES containing between 1000 and 2000kg of PCM achieves solar contributions of about 50%. For locations with more severe winter conditions, such as Zurich and Stockholm, very large storage capacities (up to 5000kg of PCM) combined with large collector areas (20m2) are required to meet between 20 and 25% of the house heating needs.
•A multi criteria analysis of solar systems for typical houses is presented.•A four person household in a 120m2 detached house was used as a case study.•Solar thermal and photovoltaic system use was ...evaluated for the 4 climatic zones of Greece.•Solar energy systems cover at least 76% of the total primary energy needs.•Solar energy systems offer a viable solution towards nearly net zero energy buildings.
Solar energy systems are currently the most widely installed renewable energy systems in the building sector in an effort to reduce the energy consumption of buildings. This paper investigates solar potential regarding photovoltaic and solar thermal utilization in typical residential buildings in order to identify their impact towards nearly Net Zero Energy Buildings (NZEB). Different options regarding the installed capacity of photovoltaics and solar combi systems in various locations and climatic conditions are evaluated from a technical as well as from an economic point of view. The results indicate that in all cases, photovoltaics are able to cover the annual electricity demand of a residential building with a payback period of less than 7years. In the case of solar combi systems, payback period ranges between 5.5 and 6.5years when compared with a conventional fuel oil heating boiler and 9years when compared with a natural gas boiler, providing at least 50% of the total heating demand of the buildings. In total, solar energy systems are able to cover at least 76% of the primary energy demand of residential buildings proving that they are a viable solution towards NZEB.
This research paper provides an increase in the energy efficiency and reliability of self-draining solar plants by optimizing their hydrodimatic operating modes. Based on this goal, the objectives of ...the study were to analyze the existing methods of protecting solar collectors of water heating and hot water supply systems from freezing and to identify the most promising methods. Also, the identification of the regularities of the hydrodynamics of a self-draining solar circuit.
Hybrid configurations that combine two different solar thermal collector technologies are considered to improve the economic competitiveness of solar systems in district heating applications. ...However, the performance of these systems in the industrial sector has been scarcely studied. This study evaluates the energetic and economic potential of hybrid systems with flat plate and parabolic trough collectors under different industrial process temperatures and radiation levels. To enable this evaluation, a hybrid field sizing methodology was developed. The results showed that the hybrid system could achieve high solar fractions with a lower levelized cost of heat than parabolic trough collector individual systems and smaller solar field areas than flat plate collector individual systems. Furthermore, the hybrid system with approximately 50% flat plate collectors reached monthly solar fractions up to 91% higher than the individual flat plate collector alternative. The seasonal performance demonstrates that the hybrid configuration could have great potential for applications with higher demand in the summer months, such as solar cooling with absorption chillers and solar water desalination for crop irrigation. This study contributes to the understanding of the potential of hybrid systems in the industrial sector and presents tools and insights for future research of hybrid solar thermal configurations.
This study investigated the techno-economic-environmental feasibility of solar heating systems for supplying power to detached buildings in the rural context. A hybrid solar–electromagnetic heating ...technology and a time-of-use pricing-based energy management technique were proposed. The developed model was validated through experiments on solar collectors and the phase-change storage tank based on the proposed time-of-use strategy. A comprehensive techno-economic-environmental single-criterion optimization scheme was constructed through coupled modeling and optimizations with TRNSYS and GENOPT. Furthermore, the comprehensive evaluation model was used to conduct a multiattribute assessment based on 13 specific sub-indicators of the studied cases. The post-operation costs and life cycle cost of the existing system under time-of-use pricing reduced by 12.2% and 7.16%, respectively. The case with optimal configuration, that is, life cycle cost optimization goal, exhibited levelized cost of energy and solar fraction of 0.82 RMB/kW·h and 64%, respectively. In severe cold regions of China with general abundant solar resource, cases utilizing a high solar energy proportion exceeding 64% perform better. This comprehensive evaluation of different scenarios provides valuable references to stakeholders for advancing renewable energy utilization in sustainable, low-carbon heating systems in rural areas of China.
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•A devised time-of-use pricing strategy integrating the phase-change storage tank is proposed.•Techno-economic and environmental performance are investigated deeply for a practical detached building in rural contexts.•A comprehensive evaluation is implemented to assess the optimized cases from the techno-economic and environmental aspects.•In general abundant solar resource regions, solar fraction of cases exceeds 64%.
► A storage tank is used in many solar water heating systems for the storage of hot water. ► Using larger storage tanks decrease the efficiency and increases the cost of the system. ► The optimum ...tank size for the collector area is very important for economic solar heating systems. ► The optimum sizes of the collectors and the storage tank are determined.
The most popular method to benefit from the solar energy is to use solar water heating systems since it is one of the cheapest way to benefit from the solar energy. The investment cost of a solar water heating system is very low, and the maintenance costs are nearly zero. Using the solar energy for solar water heating (SWH) technology has been greatly improved during the past century. A storage tank is used in many solar water heating systems for the conservation of heat energy or hot water for use when some need it. In addition, domestic hot water consumption is strongly variable in many buildings. It depends on the geographical situation, also on the country customs, and of course on the type of building usage. Above all, it depends on the inhabitants’ specific lifestyle. For that reason, to provide the hot water for consumption at the desirable temperature whenever inhabitants require it, there must be a good relevance between the collectors and storage tank. In this paper, the optimum sizes of the collectors and the storage tank are determined to design more economic and efficient solar water heating systems. A program has been developed and validated with the experimental study and environmental data. The environmental data were obtained through a whole year of operation for Erzurum, Turkey.
This paper reports the simulation results of two different solar-assisted heat pump (SAHP) systems able to cover a significant part of the space heating demand of a single-family house located in ...Madrid (Spain) using solar energy. Most SAHP systems reported in the literature serve large buildings located in cold climates using long-term (seasonal) storage tanks, a solution that leads to high investment, operation and maintenance costs that greatly limit their applicability to milder climates and/or small-scale buildings. To explore this potential application in more detail, this study examines the integration of a water-to-water heat pump in two solar house-heating systems equipped with different short-term (diurnal) stores: water, and latent (containing a phase-change material -PCM) tanks for the weather conditions of Madrid. The SAHP system’s energy performance is assessed using the TRNSYS program, implementing in the simulation scheme an experimentally validated slab-like macro-encapsulated PCM tank model (as a TRNSYS component) for the simulations including the PCM tank. Simulation results indicated that the integration of the intermediate PCM tank in the SAHP system may perform unexpectedly, generating degradation in the system performance if only conventional thermostatic control strategies are considered, diminishing the solar energy transferred to the heat pump up to approximately a 30%, and lowering the heating availability of the system from 98.9% to 72.8%. An analysis of this thermal performance degradation led to the conclusion that more advanced control strategies based on accurate knowledge of forecasts for the following days’ heating requirements, PCM temperatures and associated states of charge of the tank from the history of the fluid inlet/outlet temperatures are required.
•A solar-assisted heat pump system for building heating applications is studied.•TRNSYS schemes include an experimentally validated macro-encapsulated PCM tank model.•Useful solar energy delivered to the PCM system diminished approximately a 30%.•Limited benefits on PCM system performance were obtained increasing PCM conductivity.•PCM charging/discharging control strategy proved to be the major limiting factor.
It is indispensable for the sustainable energy supply of our society to increase the proportion of the renewables in the energy production. For this purpose, it is important to distribute the ...renewables, like solar heat, with maximal efficiency among the consumers. The theoretically established, effective tool for the solution of this problem is the mathematical (and especially, the game theoretical) modelling.
In the paper, a new differential game is proposed for solar heating systems with several consumers (players) to describe the temperature change of the solar storage and the change of the players’ payoffs over time, taking into account the heat recharge and the heat loss of the storage as well. After discretizing the players’ strategy sets, the general course of the solution of the solar heat distribution problem (among the consumers) is given assuring maximal yields for the players. For two consumers, the solution is given in details along with several practical examples, where the Pareto optimality of the non-cooperative solution (Nash equilibrium) is checked and a more advantageous cooperative solution is suggested (which is also Pareto optimal if possible) underlying that cooperation generally provides higher payoff for each player than if they consumed according to conflicting non-cooperative behaviour.
•A differential game is proposed to model solar heating systems for more consumers.•The general strategy sets are discretized to solve the heat distribution problem.•Non-cooperative (Nash) equilibrium is given and its Pareto optimality is studied.•Solution (being possibly Pareto optimal) suggested for cooperation is also given.•Illustrative realistic examples show the practical applicability of the results.
Currently, solar heating systems face several challenges in winter cold conditions, including low heat collection temperature, high heat collection loss, low thermal storage density, and unstable ...storage temperature, making it difficult to meet heating quality requirements. Taking the heating of a driving school building in the suburbs of Baiyin, Gansu as a case study, and using typical meteorological data for the local heating season, we simulated the indoor thermal load of the building using DEST software. We then designed a focused solar heating system with phase change thermal storage, coupling focused solar thermal technology with latent heat storage technology. The thermal storage performance of Ba(OH) 2 ·8H 2 O composite phase change material in an oil-sealed environment was verified. Mathematical models of the major components of the focused solar heating system with phase change storage were developed, along with a TRNSYS system model. An objective function was established using the annualized cost method, with the area of the collector and the mass of PCM as variables. Optimization was performed using Genopt software, invoking the Hooke-Jeeves algorithm to optimize the heat collection area S and mass m of phase change material in the focused solar heating system. The optimized results showed a collector area of 4.11 m 2 , and a PCM mass of 130 kg, resulting in a 10.04% improvement in the solar assurance rate. Over the system’s entire lifecycle, the cost decreased by 1025 RMB, and the carbon emission reduction increased from 10,838 to 16,101 kg.
Process heating is the activity with the most energy consumption in the industrial sector. Solar heating (SH) systems are a promising alternative to provide renewable thermal energy to industrial ...processes. However, factors such as high investment costs and area limitations in industrial facilities hinder their utilization; therefore, hybrid systems that combine two different solar thermal or photovoltaic technologies where each technology operates under conditions that allow a higher overall performance than conventional configurations have been proposed. In this review, we discuss the limitations of conventional SH systems and the potential of hybrid configurations to overcome them. First, the current literature about conventional and hybrid systems is presented. Then, the application of common performance indicators to evaluate hybrid configurations is analyzed. Finally, the limitation, advantages, and potential applications of conventional and hybrid systems are discussed. This work shows that conventional systems are the most promising alternatives in low and high-temperature industrial applications. At the same time, in medium and processes, hybrid configurations have great potential to increase the performance of SH systems and help to boost their adoption in the industrial sector. There are few studies about hybrid systems in industrial applications, and further research is required to determine their potential.
