Combisystem Research Articles

Performance evaluation of composite phase change materials with varying expanded graphite content in a drawer-type latent heat storage tank

The poor thermal conductivity of single-component phase change materials (PCMs) significantly impacts the operational efficiency of solar combi-systems. There is still a gap in the research on the heat release behavior of composite phase change materials (CPCMs). Therefore, this study investigated the heat release behavior of a self-developed drawer-type heat storage tank by varying the content of expanded graphite (EG) in the CPCMs used in it. Simulation was carried out using COMSOL Multiphysics 6.1, followed by experimentation on a test bench. The average outflow temperature, effective energy conversion (EEC), and heat release rate were used to evaluate the performance of the tanks. Comparing the simulation with experimental results, a maximum error of 8.75 % was obtained, indicating the accuracy of the study. The results indicate that adding EG can significantly improve the thermal conductivity of CPCM, with superior heat release behavior observed when the mass fraction of EG reaches 5 %. Under similar temperatures, the average outflow temperature from a 5 % EG tank is approximately 4.4 °C higher, EEC is 84 % higher, and heat release rate is 1.63 times higher than that from an ordinary thermal tank. Under different temperatures in a 5 % EG tank, increasing by 5 °C results in an average outflow temperature increase of 4.1 °C, EEC increase by a factor of one and an increase in heat release rate by 36 %. This study provides valuable insights for subsequent research on operation strategies for solar combined systems.

Rational Use of Energy in Sport Centers to Achieving Net Zero—The SAVE Project (Part B: Indoor Sports Hall)

Sports centers are significant energy consumers. This article outlines the engineering design for a comprehensive energy performance upgrade of the indoor sports hall in Arkalochori, Greece, and presents the projected results. The indoor sports hall constitutes a major sport facility on the mainland of Crete, hosting a broad cluster of sport municipal activities and the official basketball games of the local team in the 2nd national category. Having been constructed in the mid-1990s, the facility exhibits very low thermal performance, with considerably high U-factors for all constructive elements (from 4 to 5 W/m2∙K), still use of diesel oil for indoor space heating and domestic heat water production, and ineffective old lamps and luminaries covering the lighting needs of the facility. The energy performance upgrade of the indoor sports hall was studied, and the following passive and active measures were considered: Opaque-surfaces’ thermal insulation and openings’ replacement, stone wool panels, installation of heat pumps for indoor space conditioning, removal of diesel oil for any end use, production of domestic hot water from a novel solar-combi system, upgrade of lighting equipment, installation of solar tubes on the main sports hall roof for natural lighting as well as of a photovoltaic system for covering the remaining electricity consumption. With the proposed interventions, the studied building becomes a zero-energy facility. The payback period of the investment was calculated at 26 years on the basis of the avoided energy cost. This work was funded by the “NESOI” Horizon 2020 project and received the public award “Islands Gamechanger” competition of the NESOI project and the Clean Energy for EU Islands initiative.

Active solar heating system for residential building in Algeria An energetic economic and environmental investigation

In this work we used a typical single family house in Algeria as an example, the influence of building type on the energetic efficiency of an integrated solar combisystem (SCS) is determined by means of numerical simulation using TRNSYS software program. We considered two types of buildings, which have the same size and the same orientation. The first one is a low energy pilot house performed by CDER 'Centre de Développement des Energies Renouvelables' and CNERIB 'Centre National d’Etudes et Recherches Intégrées du Bâtiment' in the framework of MED-ENEC project, however, the second considered house is a virtual building; in which the walls are of the conventional type in Algeria. Based on the obtained results, it is outlined how the total system load can be decreased by adopting some solar architecture techniques. The analysis of the auxiliary energy required by the solar combi system and the average solar fraction; shows the profitability of the SCS application in Algeria, especially in the case of low energy house. Furthermore, the economic aspect and the environmental impacts of the integrated solar heating system have been investigated. The equity payback and greenhouse gas 'GHG' emissions have been estimated by means of a numerical simulation using the powerful tools of the RETScreen free software program. The obtained results showed that the equity payback is strongly dependent on the fuel used by the conventional heating system. In the case, where the heating is assured by the gasoil, the equity payback is around the half of the project lifetime. From the environmental standpoint, the solar application is entirely advantageous. In addition, the natural gas is the most favourable conventional energy resource, with a minimum yearly GHG emissions compared to electricity and gasoil.

Innovative conceptual approach in concentrated solar PV/thermal system using Fresnel lens as the concentrator

ABSTRACT Photovoltaics (PV) is an ever-evolving field. Significant technological advancement in the PV field has been evident in recent years, including PV concentrators to enhance energy density. The present experimental study explores the viability of using a refractive Fresnel lens for electrical and thermal energy through a novel approach, i.e. irradiance bi-focussing method. Unlike in most of the concentrated PV (CPV) studies, real size PV module (polycrystalline) is used here, and its surface temperature was maintained well within 80°C with the help of a self-sustainable (burlap-based) passive cooling technique. Since the concentrated irradiance gets bifurcated and simultaneously received by both PV module (≈⅓) and the thermal collector (≈⅔), the power output from CPV is more than double compared to the reference module, and the maximum thermal efficiency recorded is 48%. Even the exergy analysis upheld the proposed system as the maximum exergy efficiency is ≈ 2.5 times compared to the reference module. Concerning the heat gain, the thermal collector performance is on par with a conventional solar water heater. Hence, such a combi system can entertain a variety of day-to-day energy applications. Further, as the distance between the concentrator and PV module changes the illumination level, it can be optimized based on the cooling and/or PV module type.

Investigation of Techniques for Enhancement of Efficiency of a Hybrid Photovoltaic and Solar Thermal System: Literature Review on Applications and its Advancement

Abstract: Over the most recent couple of decades, tremendous consideration is drawn towards photovoltaic–thermal systems because of their advantages over the solar thermal and PV applications. This paper intends to show different electrical and thermal aspects of photovoltaic–thermal systems and the researches in absorber design modification, development, and applications. From the previous review articles, it has been concluded that the heat energy exhausted from the PV module can be further utilized in different ways and helps in achieving better efficiency. Furthermore, the types of photovoltaic–thermal systems such as air collector, water collector, and combi system, coupling with heat pump and their application to buildings are also stated. This paper also discussed certain design aspects like modifications in the flow channel by adding fins, thin metallic sheets, rollbond absorber, and porous media and the effect of these modifications on the hybrid system’s efficiency. Further- more, the use of the latest technologies such as nano fluids, thermoelectric generators, and phase-change materials improves the overall system performance. The role of soft-computing techniques is forecasting the impact of various parameters on the photovoltaic–thermal system is also discussed.

Rational Use of Energy in Sports Centres to Achieve Net Zero: The SAVE Project (Part A)

Sports centres constitute major energy consumers. This article presents the proposed energy performance upgrade process and the achieved results for the municipal sports centre in Arkalochori, Greece. The facility consists of a swimming pool centre, an outdoor 8 × 8 football court, and two tennis and basketball courts. It operates with considerably high energy consumption due to the lack of any measure towards its energy efficiency improvement since its initial construction in 2002. Due to the significantly high heating cost, the swimming pool centre remains operative only during the summer period. The energy performance upgrade of the facility was holistically approached through all possibly applicable passive and active measures: insulation of opaque surfaces and replacement of openings, construction of a new, bioclimatic enclosure for the swimming pool’s centre and conversion of the current outdoor facility to an indoor one, installation of heat pumps for indoor space conditioning and swimming pool heating, installation of a solar–combi system for domestic hot water production, upgrade of all indoor and outdoor lighting equipment and installation of a photovoltaic plant on the new enclosure’s roof for the compensation of the remaining electricity consumption. With the proposed measures, the municipal sports centre is upgraded to a zero energy facility. The payback period of the investment was calculated at 14 years on the basis of the avoided energy procurement cost. The swimming pool’s centre operation is prolonged during the entire annual period. This work has been funded by the Horizon 2020 project with the acronym “NESOI” and was awarded the public award of the “Islands Gamechanger” competition of the NESOI project and the Clean Energy for EU Islands initiative.

Gaz Yakıtlı Kombi Sisteminin Yapay Sinir Ağı ile Yakıt Miktarı Tahmini Isparta Örneği

Bir gaz yakıt olan doğalgazın çevreye duyarlı temiz enerji kaynağı olmasından dolayı dünyadaki kullanımı giderek artmaktadır. Türkiye’de doğalgaz çıkarımı noktasında çalışmalar gün geçtikçe yapılmaktadır. Ancak büyük miktarda dışa bağımlı olarak satın alınmaktadır. Doğalgaz Türkiye’de kullanımına bağlı olarak stok yapılmak durumundadır. Bu avantajından dolayı tüketmiş olduğumuz doğalgazın yıllık tüketim tahmini de son derece önem arz etmektedir. Özellikle son yıllarda doğalgaz maliyetlerinin artmasıyla birlikte ne kadarlık bir yıllık harcamanın yapılacağı konusunda önemli hesaplamalar yapılması gerekmektedir. Günümüzde, yönetimsel enerji kullanımları sayesinde enerji maliyetlerinde düşüşler sağlanabilmektedir. Bu çalışmada, Isparta ilinde bulunan 120 m2 büyüklüğünde doğu kuzey cepheli mantolaması bulunan 10 yıllık bir konut için doğalgaz yakıtlı kombi sistemi kullanan bir evde geliştiren bir ölçüm sistemi ile odaların, dış havanın sıcaklık değerleri ve sistemin yakıt miktarı ölçülerek kayıt altına alınmıştır. Ekim, Kasım, Aralık, Ocak, Şubat, Mart aylarına ait 181 adet veri ele alınmıştır. Bu verilerin 141 tanesi eğitim, 10 tanesi doğrulama ve 30 tanesi test için kullanılmıştır. Oluşturulan yapay sinir ağı modeli eğitim verileri ile eğitilmiştir. Standart bir kış sezonunda oda sıcaklıklarına ve dış hava sıcaklığına göre tüketilen günlük doğalgaz miktarları, yapay sinir ağı (YSA) modeli yardımıyla eğitilmiş 0.118 MSE hata ile doğalgaz yıllık tüketim miktarı %98 oranında tahmin edilmiştir.

Techno-economic design of a solar combisystem in a residential building

A solar combisystem is utilized to supply domestic hot water (DHW) and heat a residential building. This system decreases the fossil fuel consumption and, hence, reduces air pollution and global warming. This paper proposes an innovative method to design and optimize a suitable solar combisystem for a residential building with respect to technical and economic parameters. First, different configurations of solar combisystems, including various components, are considered. Then, the optimum design variables are determined for each configuration using Grouped Method of Data Handling (GMDH) type of Artificial Neural Network (ANN) and Non-Dominated Sorting Genetic Algorithm II (NSGA-II). Total Solar Fraction (TSF) and Life Cycle Cost (LCC) are considered as objective functions. Finally, the optimum design is chosen for the solar combisystem. Typically, researchers have focused on evaluating the performance of a single solar combisystem configuration in each study. However, this research takes a different approach by optimizing multiple configurations, resulting in a significant improvement in the total solar fraction by 7.3%. This is the main novelty of this paper. Based on the results, the optimum configuration of the solar combisystem includes 17.91 m2 of evacuated-tube collectors with a tilt angle of 50°. Also, the volume of the hot water tank and heating buffer tank are, respectively, equal to 204 and 500 L (L). In this system, solar energy provides 94% of the required energy for supplying DHW and 23% of the energy for heating the building. Moreover, reduction of annual CO2 emissions is 1806 kg. This paper presents a guideline to design solar systems for the residential buildings considering technical and economic aspects.

Economic and Energetic Assessment and Comparison of Solar Heating and Cooling Systems

Solar heating and cooling (SHC) systems are currently attracting attention, especially in times of increasing energy prices and supply crises. In times of lower energy prices, absorption SHC systems were not competitive to compression cooling supported by photovoltaic (PV) modules due to the high investment costs and total energy efficiency. This paper aims to discuss the current changes in energy supply and energy prices in terms of the feasibility of the application of a small absorption SHC system in a mild Mediterranean climate. The existing hospital complex restaurant SHC system with evacuated tube solar collectors and a small single-stage absorption chiller was used as a reference system for extended analysis. Dynamic simulation models based on solar thermal collectors, PV modules, absorption chillers and air-to-water heat pumps were developed for reliable research and system comparison. The results showed that primary energy consumption in SHC systems designed to cover base energy load strongly depends on the additional energy source, e.g., boiler or heat pump. Absorption SHC systems can be price competitive to air-to-water heat pump (AWHP) systems with PV collectors only in the case of reduced investment costs and increased electricity price. To reach acceptable economic viability of the absorption SHC system, investment price should be at least equal to or lower than a comparable AWHP system.

Simulation and Optimization of Solar Domestic Hot Water Systems

Energy-efficient building is the only solution to reduce energy costs and greenhouse gas emissions. A solar combi-system is a solar installation that provides both domestic hot water and heating. In this work, the authors evaluated the energy needs of such a system in the case of an F3 type house on a site in Meknes. The technical regulatory document is used to determine the energy demand for heating and to verify the conformity of the buildings to the thermal regulations. The domestic hot water demand is evaluated according to the analytical method. A thermal simulation of the production of domestic hot water under TRNSYS 16 confirms the results obtained by the analytical method.

Multi objective optimization of detailed building models with Typical Short Sequences considering sequential and adaptive methods

Multi-objective optimization of detailed building models may lead to high computational time expenses. The work presented in this paper presents an alternative of classical approaches based on the usage of reduced sequences in a sequential and an adaptive approach. The sequential approach runs directly the reduced sequence obtained from a typical day selection algorithm which employs a k- medoids clustering algorithm in a multi-objective optimization study. It was applied on a solar combisystem connected to a building model and showed its capability of reproducing the Pareto front 25 times faster with relative errors not exceeding 5% when considering several parametric configurations of the model and focusing on a limited number of selection criteria during the day selection process. On the other hand, the adaptive approach for optimization named OptiTypSS achieves day selection during the optimization process by combining an iterative day selection algorithm (TypSS) with a genetic algorithm of optimization (NSGA-II). The method succeeded in obtaining results with errors inferior to 3% being therefore as efficient as a classical metamodel adaptive approach yet with relatively higher computational time. Further improvements including parallel simulation during the day selection process can be done to enhance the performance.

Energetic, economic, environmental and climatic analysis of a solar combisystem for different consumption usages with PSI method ranking

Using solar systems is increasing due to oil shortage, environmental effects, and renewability. Solar thermal combisystems use the energy taken to provide for both domestic hot water (DHW) and space heating (SH), which is under investigation by energy researchers. This study uses a dynamic energy analysis of the solar system to evaluate the solar parameters. Also, the environmental and economic effects of using solar systems are discussed. The study is done on four different consumption usages in four different climates of Iran. Energy simulation shows that hot & humid climates, office, and mall usages have the largest solar fraction (minimum of 95.2, 38.5, and 35%, respectively). The lowest optimal collector surface area belongs to a hot and humid climate with 4–21.5 m2 and office usage with 4–159 m2. Also, collector efficiency decreases with higher collector area amounts. 20-year economic analysis shows that the net present value of hospital usage with a maximum of $2216.8, cold climate with a maximum of $768.4, and hot & humid climate with a maximum of $2765.9 are the most affordable. The environmental analysis illustrates that CO2 emission avoidance is highest in hospital usage with a maximum of 1924.5 kg, residential usage with a maximum of 1707.8 kg, and hot & dry climate with a maximum of 1349.2 kg. Lastly, the preference selection index (PSI) method is used to rank all application possibilities, which shows that using systems is highly recommended in cold, hot & humid climates with the best ranks of 1 and 3 and hospital usage with the best rank of 1.

Hybrid solar photovoltaic thermal systems in Nearly-Zero Energy Buildings: the case of a residential building in Greece

ABSTRACT The continuous increase in energy demand has led to the gradual depletion of fossil fuels and the corresponding environmental degradation. As a result, the implementation of energy efficiency measures, as well as the integration of Renewable Energy Sources systems, are a challenge on the road towards Nearly-Zero Energy Buildings. Within the framework of this study, an extensive literature review was carried out on the existing Photovoltaic/Thermal collector technologies, their energy, environmental and economic efficiency. Furthermore, a solar combi system with photovoltaic/thermal collectors installed in a residential building was studied. The system was evaluated for its energy and environmental efficiency. Finally, the results in terms of thermal efficiency and carbon footprint were compared with those of a solar combi system with a flat plate collector.

Experimental assessment of double-pass solar air heater by incorporating perforated baffles and solar water heating system

An investigation on a solar combi-system that serves the dual purpose of supplying increased temperature air for Solar Air Heater (SAH) based applications and hot water for domestic applications is presented in the article. To achieve the objective of the solar combi-system, two identical double-pass SAHs were fabricated: one without augmentation, while the other with an augmentation of vertical plate perforated baffles on the absorber plate and the pipe carrying hot water over the bottom plate. Experiments for the upward and downward flow of air were carried out for three consecutive days in each case to investigate the thermal performance of both SAHs. Compared to the conventional SAH, daily average outlet air temperature, daily average heat gain received by air, daily average efficiency, heat transfer coefficient (average), and Nusselt number (average) were higher by 6.48%, 17.10%, 17.24%, 5.77%, and 5.20% for the upward flow of air in the augmented SAH, respectively. Whereas increment of 8.59%, 21.46%, 21.87%, 27.28%, and 26.68% was obtained in respective parameter for the downward flow of air in the augmented SAH. The thermal performance of augmented SAH was found superior compare to that of conventional SAH in the case of the downward flow of air.

Energy, Economic and Environmental (3E) Analysis of a Tank-in-Tank Solar Combisystem

In this study, the thermal performance of a tank-in-tank solar combisystem is dynamically simulated to investigate the effect of various parameters such as collector type and area, storage tank volume, building specifications, heat exchange terminal units, and climatic conditions on system performance. The results showed that by increasing the collector area, tank volume and thickness of wall insulation, the solar fraction increases. It was also found that the use of floor heating instead of a radiator system improves the system performance. The solar fraction using the evacuated tube solar collector is 2.3% higher than that using flat plate solar collector. The annual solar fraction of 45.6%, 63.4%, 41.2%, 34%, 57.3%, and 88.1% is obtained in Hot-Dry (Tehran), Hot-Dry (Yazd), Cold-Dry (Tabriz), Moderate-Humid (Rasht), Hot-semi Humid (Abadan), and Hot-Humid (Bandar Abbas), respectively. The environmental analysis indicates that using the proposed solar combisystem could save 2241.3 m³ natural gas and offsetting 4731.5 kg less CO2 emissions during a year. The life cycle cost analysis shows that the payback time of the proposed system for the economic conditions of Iran is 7 years.

Life-cycle cost optimization of a solar combisystem for residential buildings in Nepal

ABSTRACT Current solar thermal systems used in Nepal are mostly for domestic hot water heating. Meanwhile, there is a growing need for space heating. A solar heating system can be configured to provide heat for both space heating and domestic hot water, leading to a solar combisystem. Research on residential solar combisystems in the Nepalean context barely exists in literature. This paper intends to propose, model and optimize a solar combisystem for typical single-family houses in Nepal. The optimization problem is formulated to have life-cycle cost as the objective function and a total of 11 variables, which are related to the sizing of combisystem components and the insulation thickness of building envelope. The number of hours not satisfying the thermostat heating set point is treated as the constraint. TRNSYS is used for modeling the solar combisystem. Particle Swarm optimization and the Hooke-Jeeves algorithm implemented in GenOpt are sequentially applied to solve the optimization problem. The results show that the optimization is effective to reduce the life-cycle cost by 66% for the Terai region and 77% for the Hilli region. The findings have demonstrated the importance of building envelope insulation to spread the use of solar combisystems in Nepal.

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.

Quantifying the performance advantage of using passive solar air heater with chimney for photovoltaic module cooling

The foreseeable growth of photovoltaic (PV) systems highlights the prominence of improving its efficiency. The performance of PV module deteriorates as a major part of irradiance is converted to heat. Amongst several PV thermal management techniques, passive air cooling is gaining importance due to its self-sustained nature. In the present experimental study, the performance of conventional solar air heater is enhanced by incorporating chimney. Further, by placing the PV module in the airflow path, its performance is improved compared to an identical module kept open to ambient. During testing, a maximum system efficiency of 35% was observed as air heater contributes to the maximum thermal efficiency of 25%. Further, due to better airflow over the PV module rear surface, a 13% reduction in surface temperature was observed compared to the outer module, which gave a 6% rise in power output. In such a combi system, the working of both PV and air heater complements the advantage to each other. Hence, the total efficiency of the air heater and PV module as two separate entities is always less than the system efficiency of the combi system.

Computational Simulation and Dimensioning of Solar-Combi Systems for Large-Size Sports Facilities: A Case Study for the Pancretan Stadium, Crete, Greece

The article examines the introduction of solar-combi systems in large-size sports facilities. The examined solar-combi systems consist of solar collectors, a biomass heater and thermal storage tanks. In a sense, they constitute hybrid thermal power plants. The full mathematical background is presented on the operation of such systems, along with a proposed operation algorithm, aiming at the maximization of the captured solar radiation. A case study is implemented for the coverage of the thermal energy needs for hot water production and swimming pools heating, met in the Pancretan Stadium, Crete, Greece. In this way, the article aims to indicate the technical and economic prerequisites that can guarantee the feasibility of the examined systems, highlighting the significant potential contribution of such systems towards the realization of energy transition plans from fossil fuels to renewables. The economic feasibility of the introduced system is based on the avoiding diesel oil and electricity procurement cost, consumed for the coverage of the thermal energy demands under consideration. The optimum dimensioning of the examined case study results to an annual thermal energy demand coverage balance of 55% by the solar collectors and 45% by the biomass heater, giving a payback period of 5–6 years.

Alternative storage options for solar thermal systems

The efficient implementation of solar systems in buildings depends on the storage of energy yielded, as it can both increase the solar system's autonomy and make it a feasible solution for zero energy buildings, and make storage vessels more compact, reducing precious space requirements. This is of particular important in places with reduced time of sunshine, where solar systems are less effective, because of the deviation between solar radiation and the demand. The traditional storage options use water, which is practical, safe and low-cost, especially when the storage requirements are small. However, when larger storage is needed, limits concerning the use of water exist, mainly due to the need for larger installation space and the increased thermal losses. The use of phase change materials (PCM) for thermal energy storage seems an upcoming technology. The main idea is the substitution of water with PCM, which feature larger specific energy storage capacity compared to other conventional materials. In the context of the specific paper, a combined solar thermal system used for the preparation of domestic hot water (DHW) and space heating (Solar Combi System) with two different types of storage is studied, for two Greek cities. The aim is to find out which is the most efficient way of storing energy with respect to the autonomy of the system, for a solar combi system. This is being achieved by determining the comparative autonomy of PCM and water storage system for various climates. It was proven that using PCM is advantageous, as it can extend the autonomy duration of the solar system for 2 to 8 hours, depending on the season and the climatic conditions. However, it was also seen that in solar combi systems used throughout the whole year, PCM are inefficient during summer period.