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Home , Sensible heat

Energy Conversion and Management 84 (2014) 311–325

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Energy Conversion and Management

journal homepage: www.elsevier.com/locate/enconman

Comprehensive thermodynamic analysis of a renewable energy sourced hybrid combined with latent storage ⇑ Zafer Utlu a, , Devrim Aydın b, Olcay Kıncay c a Istanbul Aydın University, Engineering Faculty, Department, Istanbul, Turkey b Institute of Sustainable , University of Nottingham, Nottingham NG7 2RD, UK c Yildiz Tecnical University, Mechanical Faculty, Mechanical Engineering Department, Istanbul,_ Turkey article info abstract

Article history: In this study an experimental thermal investigation of hybrid renewable heating system is presented. Received 20 February 2014 storage stores energy, gained by solar collectors and supplies medium temperature heat to Accepted 4 April 2014 both day time also night time while solar energy is unavailable. In addition to this an accu- Available online 8 May 2014 mulation tank exists in the system as sensible heat storage. It provides supply–demand balance with storing excess high temperature heat. Keywords: Analyses were done according to thermodynamic’s first and second laws by using real data obtained Latent heat storage from a prototype structure, built as part of a project. Results show that high percent of heat loses took Solar energy place in heat pump with 1.83 kW where accumulator-wall heating cycle followed it with 0.42 kW. Con- Heat pump Energy trarily highest break-down of exergy loses occur accumulator-wall heating cycle with 0.28 kW. Averagely Exergy 2.42 kW exergy destruction took place in whole system during the experiment. Solar collectors and heat pump are the promising components in terms of exergy destruction with 1.15 kW and 1.09 kW respec- tively. Exergy efficiency of system components, investigated during discharging period are in a close approximately of 32%. However, efficiency of solar collectors and charging of latent heat storage are 2.3% and 7% which are relatively low. Average overall total energy and exergy efficiencies of latent heat storage calculated as 72% and 28.4% respectively. Discharging energy efficiency of latent heat storage is the highest through all system components. Also heat pump has a significant efficiency which is 78%. Ó 2014 Elsevier Ltd. All rights reserved.

1. Introduction Development of HRES is mentioned below [3];

High fossil fuel prices and greenhouse emissions are the driving a. Binary HRES force for studying to find new ways of benefitting from various Binary is the most mature HRES among all and it constitutes the renewable energy resources [1]. For most people all over the world, basis of combination of renewable sources. This system solar energy is evaluated as a primary energy source for the employs two different renewable sources. Classification of cou- future. Whilst research about new and renewable energy resources ples used in binary HRES is given below. As it can be seen, solar is vital, improving systems is as important as energy is the constant component, and it can be combined with benefitting from new energy resources. Storing energy in a HP for heating or wind turbine for electricity generation. suitable way, not only provide equilibrium between supply and Considering that renewable sources are cyclic and unstable, demand but also increasing performance and utility of energy combination of these systems brings significant advantages systems [2]. such as, higher and more stable thermal-electrical power gener- Over recent decades several researches have been made about ation, higher efficiency, and cost-effective system designs. binary hybrid renewable energy systems (HRES) (solar-ground, Solar assisted ground sourced horizontal heat pump. solar-wind, solar-heat storage) used for heating and cooling pur- Solar assisted ground sourced vertical heat pump. poses. Researches about a hybrit system in which all these sources Solar assisted geothermal heat pump. were used optimally have been carrying on. Solar –wind energy sourced HRES. Solar energy sourced heat storage system. b. Three component HRES ⇑ Corresponding author. As a result of the recent developments in stor- E-mail address: [email protected] (Z. Utlu). age systems, combining these systems with a solar source and http://dx.doi.org/10.1016/j.enconman.2014.04.024 0196-8904/Ó 2014 Elsevier Ltd. All rights reserved. 312 Z. Utlu et al. / Energy Conversion and Management 84 (2014) 311–325

Nomenclature

A area g efficiency c specific heat (kJ/kg K) D difference E_ energy (W, kW) _ Ex exergy (W, kW) Indices h (kJ/kg) i input 2 I solar radiation (W/m ) o output m_ flow rate (kg/s) s stored T temperature (°C, K) a accumulated W (W, kW) d destruction LHS latent heat storage l loss SHS sensible heat storage s,r solar irradiation HP heat pump k heat source AT accumulator tank c collector WH wall heating system t total HRES hybrid renewable energy system n net PCM change material 0 ambient conditions GSHP ground sourced heat pmp p pump YREB yildiz renewable energy building sp supply g generation Greek symbols comp Q thermal energy (W, kW) tr transferred w exergy to energy ratio for radiation

HP came into question. In addition to the advantages of binary, optimum collector area in a solar assisted heat pump system, as three component HRES provides balance between supply– well as, comparisons were made between theoretical and experi- demand, as well as, make design and operation conditions of mental results [5]. Hancıoglu and Hepbasli presented a detailed hybrid systems easier. Furthermore, solar and ground energy research about design, test and performance criteria of GSHPs is highly dense in the summer when the heat load is very low [6]. Moreover, Wang et al. experimentally investigated solar or zero, alternatively, these sources are insufficient in the win- assisted-ground coupled heat pump combined with thermal heat ter. Three component HRES will bring a significant advantage to storage. Researchers calculated HP and system COP as 4.29 and store energy generated by system components. 6.55 respectively [7]. In a similar experimental analysis, Kuang c. Four component HRES et al. found system COP in the range of 2–2.25. Furthermore heat- Four component HRES is a relatively new technology based on ing capacity of the system and electricity consumption of HP were combining , HP, solar (thermal and pho- determined as around 5 kW and 2.5 kW respectively [8]. In another tovoltaic) panels, as well as, wind energy. In this concept, the experimental study conducted by Yumrutas et al., COP of HP found main purpose is generating both electrical and thermal energy in the range of 2.5–3.5 [9]. Li et al. developed a solar assisted heat from renewable sources in an efficient way. Once in practice pump water heater. According to experimental analysis exergy these systems will be an important step on the way of decreas- efficiency was 21%. Additionally overall COP of the system was var- ing energy consumption in residential buildings. However, ied between 3.11 and 6.61 [10]. Liang et al. investigated the affect research-development studies seem crucial to achieve efficient, of collector area to the HP performance in a solar assisted HP sys- low cost and stable four component HRES. tem. Results showed increasing the collector area from 0 to 40 m2, increased COP of HP and energy saving rate 11.33% and 24% respec- In this study a comprehensive thermodynamic analysis of three tively [11]. Bi et al. made an exergetic analysis of GSHP, which component HRES consist of solar collectors, HP and LHS has been found overall exergy efficiency was 10% in heating mode and 7% made. At present, there is an insignificant amount of literature in cooling mode [12]. Similarly; Dghigh et al. [13], Bakırcı et al. available in this subject matter. Specifically, research on second [14] and Dikici et al. [15] made various numerical and experimen- law analysis seems insufficient. The main purpose of this study tal studies about utility of hybrid systems using both solar energy was investigating the affect of LHS on the system performance and horizontal type heat pump. Akpınar et al. [16] and Özgener and (first and second law) and electricity consumption of HP. Addition- Hepbasßlı [17] investigated solar assisted vertical heat pumps. ally investigating suitability of hybrid heating systems with wall Bedescu [18–20] made several researches about solar assisted air heating applications was an aim of present study. and water sourced heat pumps. Cervantes et al. [21], Hawlader Approximately 50% of overall energy consumption takes place et al. [22], Urchueguía et al. [23], and Dikici et al. [24], also ana- in the building sector of which 70% is used for pur- lysed usage of air or water as heat source in solar assisted heat poses. Considering the high amount of fossil fuel consumption and pump systems. exergy destruction, current and forthcoming studies for improving There are several numerical and experimental studies about renewable sourced heating systems have significant importance. storage of solar energy in heat form for heating applications. Ucar and Inalli [25], Koca et al. [26], Öztürk [27], Alkilani et al. [28], Fab- 1.1. Literature Review rizio [29], Kousksou et al. [30], Aghbalou et al. [31], Kenisarin et al. [32], Hussain et al. [33] and Argiriou et al. [34] developed various There are several studies about hybrit systems. Dincer evalu- designs for storing solar energy for long time or short time periods. ated the performance of thermal energy storage systems in solar In the last decade significant improvements about renewable thermal applications [4]. On the other hand, Kaygusuz analysed energy technologies, have been providing a possibility to increase Download English Version: https://daneshyari.com/en/article/763795

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