Supercapacitor in Battery Charges of Photovoltaic Panel: Analysis of an Association of Batteries and Supercapacitors in a Collaborative Operation

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Available online at www.sciencedirect.com View metadata, citation and similar papers atAvailable core.ac.uk online at www.sciencedirect.com brought to you by CORE ScienceDirect provided by Repositório Científico do Instituto Politécnico do Porto ScienceDirect AvailableEnergy online Procedia at www.sciencedirect.com 00 (2018) 000–000 Available online at www.sciencedirect.com 2 T. Nogueira et al./ Energy Procedia 00 (2018) 000–000 Energy Procedia 00 (2018) 000–000 www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia ScienceDirectScienceDirect 1. Introduction EnergyEnergy ProcediaProcedia 00153 (20 (2018)17) 000 80–85–000 The energy from the cells can either be used directly or can be used to recharge batteries, which in turn can power www.elsevier.com/locate/procedia some consuming application [1]. A necessity for the storage system arises to limit the effect of the variation of the 5th International Conference on Energy and Environment Research, ICEER 2018 solar conditions along the environmental day conditions [2]. However, the cost of batteries and their limited lifetime 5th International Conference on Energy and Environment Research, ICEER 2018 are serious disadvantages [3] [4]. In addition, there is a technical contradiction in extracting the maximum power from a photovoltaic panel and the charge cycle of a lithium ion battery. To contain that problem, in this work we propose Supercapacitor in battery charges of photovoltaic panel: analysis of an association of batteries and supercapacitors in a collaborative operation. Supercapacitor in battery charges of photovoltaic panel: analysis of To get the point of maximum power generation from a photovoltaic (PV) panel, under frequent variations in solar The 15th Internationalthe technical Symposium feasibility on District Heating and Cooling irradiance and temperature, it is necessary to perform the MPPT - Maximum Power Point Tracking of the PV panel the technical feasibility [5] [6]. However, there is a problem in extracting the maximum power point from a PV panel, as shown in Fig. 1 (a), Victor Barbosaa,c, Teresa Nogueiraa,b,*, Emerson Caratic, Carlos Felgueirasa,b with the charge time curve of a lithium ion battery, as shown in Fig. 1 (b). This problem comes up because to follow VictorAssessing Barbosa thea,c, Teresa feasibility Nogueira ofa,b ,using*, Emerson the Caratiheat cdemand, Carlos Felgueiras-outdoora,b the charging of a battery it is necessary to go through two stages, one of constant current and another of constant aISEP- School of Engineering, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida 431, 4249-015 Porto, Portugal voltage, which do not match to the voltage and current output from PV panel operating in MPPT. b temperaturea function for a long-term district heat demand forecast CIETI - CenterISEP -for School Innovation of Engineering, in Engineering Polytechnic and Industrial of Porto ,Technology, Rua Dr. António R. Dr. Bernardino António Bernardino de Almeida de 431, Almeida 4249 431,-015 4249Porto,-015 Portugal Porto, Portugal Even using only converters this problem persists because photovoltaic generation may contain unhoped bcUTFPR – Federal University of Technology - Parana, Campus Pato Branco, Via do conhecimento, KM 01, s/n, 85503-390 Pato Branco, Brazil CIETI - Center for Innovation in Engineering and Industrial Technology, R. Dr. António Bernardino de Almeida 431, 4249-015 Porto, Portugal fluctuations, while battery charging cannot have fluctuations. Therefore, the MPPT of the PV panel is not possible cUTFPR – Federal Universitya,b,c of Technology - Paranaa , Campus Patoa Branco, Via do conhecimento,b KM 01, s/n,c 85503-390 Pato Brancco, Brazil I. Andrić *, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Corre without consideration of generated energy waste, if there isn´t an intermediate step of energy storage. aIN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal Abstract bVeolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract cDépartement Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France The power generation from photovoltaic sources is variable and may contain unhoped fluctuations, which can be relievedThe pow byer generationusing energy from storage photovoltaic systems. sources However, is variable there is anda technical may contain contradiction unhoped influctuations, extracting thewhich maximum can be relievedpower from by usinga photovoltaic energy storage panel and systems. the charge However, cycle thereof a battery. is a technical To overcome contradiction this problem in extracting, this paper the presents maximum an powerimprovementAbstract from a photovoltaicconsisting in panel a collaborative and the charge association cycle of aof battery. lithium To ion overcome batteries t handis problem supercapacitors, this paper showing presents the an improvementtechnical feasibility consisting in a photovoltaicin a collaborative system. association of lithium ion batteries and supercapacitors showing the technicalTheDistrict structure heating feasibility of networksthe inenergy a photovoltaic are ccommonlyonversion system. addressedsystem was in thedeveloped literature and as onewas of set the up most the effectiveconverter solutions’s configuration, for decreasing design the Theandgreenhouse operationstructure gas ofsimulation emissions the energy .from The c onversionthe power building management system sector. wasThese of developed systemsfull system require and i mplementationwas high set investments up the wasconverter which simulat are’s returnededconfiguration, and thethrough results designthe areheat Fig. 1. (a) PV panel power curve (b) Battery charge curve. andpresentedsales operation. Due. Theto simulationthe proposed changed .s ystemTheclimate power development conditions management and and building itof technical full renovationsystem analysis implementation policies, was carriedheat demandwas out simulatfor in both theed situationsfuture and thecould results, with decrease, andare presentedwithoutprolonging the. The theuse investment proposedof supercapacitor. returnsystem period. development It was concluded and it thattechnical the supercapacitor analysis was carriedin the photovoltaic out for both systemssituations bring, with better and The problem was analyzed in this study with an intermediate step of fast energy storage, provided by the use of a withoutchargingThe main the conditions, scope use ofof thissupercapacitor. resulting paper is toin assessshorter It was the charging feasibilityconcluded times of that using and the the better supercapacitor heat systemdemand performances. – outdoorin the photovoltaic tempe rature function systems for bring heat demandbetter supercapacitor [7]. The idea of using a supercapacitor is to supply the power needed to charge the battery when the forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 charging conditions, resulting in shorter charging times and better system performances. PV panel does not produce all the necessary power, or to absorb the excess of panel generation. buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district © 2018 The Authors. Published by Elsevier Ltd. © 2018 The Authors. Published by Elsevier Ltd. This©renovation 2018 is an The open Authors.scenarios access Pu articlewereblished developedunder by Elsevierthe CC(shallow, BY Ltd.-NC intermediate,-ND license (deep).https://creativecommons.org/lice To estimate the error, obtainednses/by heat-nc- nd/4.0/demand) values were 2. Methodology description Thiscompared is an open with accessresults articlefrom a underdynamic the heatCC BY-NC-NDdemand model, license previously (https://creativecommons.org/licenses/by-nc-nd/4.0/ developed and validated by the authors. ) SelectionThis is an andopen peer access-review article under under responsibility the CC BY- NCof -theND scientific license (https://creativecommons.org/lice committee of the 5th Internationalnses/by Conference-nc-nd/4.0/ on) Energy and SelectionThe results and showed peer-review that when under only responsibility weather change of the is scientificconsidered, committee the margin of of the error 5th couldInternational be acceptable Conference for some on applicationsEnergy and EnvironmentSelection and Research, peer-review ICEER under 20182018. responsibility. of the scientific committee of the 5th International Conference on Energy and The proposed design involves the use of supercapacitor in a Li-ion battery charger, using the solar energy from the Environment(the error in Research,annual demand ICEER was 2018 lower. than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). PV panel, called in this paper as the Solar Battery Charger with Supercapacitor (SBCS). Keywords: battery charger; digital control; photovoltaic panel; supercapacitor The diagram of this type of charger is shown in Fig. 2, where the systems of control (SC), which control the direct Keywords:The value battery of slope charger; coefficient digital control; increased photovoltaic on average panel; supercapacitorwithin the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and current converters (CCC), are represented in order to achieve the main objective of charging the battery. These control renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the systems are coordinated by the power manager (PM), which reads the signals of generated power, current and voltage coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and levels in the system, in order to continuously charge the battery even if there isn´t enough solar radiation. improve the accuracy of heat demand estimations. According to the diagram of Fig. 2, the PV panel converts the energy needed to charge the battery. We can see in

Fig. 2, the CCC1 is the direct current converter that performs the tracing of the maximum power point of the PV panel. © 2017 The Authors. Published by Elsevier Ltd. * Corresponding author. Tel.: +351 919 652 799; fax: +351 228 321 159. The CCC2 bidirectional converter has the function of keeping energy in the supercapacitor when the photovoltaic Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and * CorrespondingE-mail address: author. [email protected] Tel.: +351 919 652 799; fax: +351 228 321 159. panel generates excess energy and can´t be received by the battery. In addition, the CCC2 can manage power from Cooling. E-mail address: [email protected] supercapacitor to charge the battery when the PV panel does not generate enough, in way of maximizing the generated 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. Keywords: Heat demand; Forecast; Climate change energy from PV panel. So, the supercapacitor performs the function of intermediate energy storage, a kind of energy 1876This -is6102 an open © 2018 access The article Authors. under Published the CC BYby Elsevier-NC-ND Ltd. license (https://creativecommons.org/licenses/by-nc-nd/4.0/) buffer function. Selection and peer-review under responsibility of the scientific committee of the 5th International Conference on Energy and Environment This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) The CCC3 converter has the objective of charging correctly the battery according to its manufacturer’s description, SelectionResearch, andICEER peer 2018-review. under responsibility of the scientific committee of the 5th International Conference on Energy and Environment Research, ICEER 2018. following optimum charging curves [8]. That combination of a supercapacitor and a battery to form an energy storage system reduces the stress on the 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. battery caused by the high discharge currents, resulting in an increase in the life of the batteries [9]. ThisPeer -isreview an open under access responsibility article under of the the Scientific CC BY-NC-ND Committee license of The 15th(https://creativecommons.org/licenses/by-nc-nd/4.0/ International Symposium on District Heating and Cooling) . Selection and peer-review under responsibility of the scientific committee of the 5th International Conference on Energy and Environment Research, ICEER 2018. 10.1016/j.egypro.2018.10.019

10.1016/j.egypro.2018.10.019 1876-6102 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect ScienceDirect Energy Procedia 00 (2018) 000–000 Victor Barbosa et al. / Energy Procedia 153 (2018) 80–85 81 2 T. Nogueira et al./ Energy Procedia 00 (2018) 000–000 Energy Procedia 00 (2018) 000–000 www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia 1. Introduction

The energy from the cells can either be used directly or can be used to recharge batteries, which in turn can power some consuming application [1]. A necessity for the storage system arises to limit the effect of the variation of the 5th International Conference on Energy and Environment Research, ICEER 2018 solar conditions along the environmental day conditions [2]. However, the cost of batteries and their limited lifetime 5th International Conference on Energy and Environment Research, ICEER 2018 are serious disadvantages [3] [4]. In addition, there is a technical contradiction in extracting the maximum power from a photovoltaic panel and the charge cycle of a lithium ion battery. To contain that problem, in this work we propose Supercapacitor in battery charges of photovoltaic panel: analysis of an association of batteries and supercapacitors in a collaborative operation. Supercapacitor in battery charges of photovoltaic panel: analysis of To get the point of maximum power generation from a photovoltaic (PV) panel, under frequent variations in solar the technical feasibility irradiance and temperature, it is necessary to perform the MPPT - Maximum Power Point Tracking of the PV panel the technical feasibility [5] [6]. However, there is a problem in extracting the maximum power point from a PV panel, as shown in Fig. 1 (a), Victor Barbosaa,c, Teresa Nogueiraa,b,*, Emerson Caratic, Carlos Felgueirasa,b with the charge time curve of a lithium ion battery, as shown in Fig. 1 (b). This problem comes up because to follow Victor Barbosaa,c, Teresa Nogueiraa,b,*, Emerson Caratic, Carlos Felgueirasa,b the charging of a battery it is necessary to go through two stages, one of constant current and another of constant aISEP- School of Engineering, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida 431, 4249-015 Porto, Portugal voltage, which do not match to the voltage and current output from PV panel operating in MPPT. b a CIETI - CenterISEP -for School Innovation of Engineering, in Engineering Polytechnic and Industrial of Porto ,Technology, Rua Dr. António R. Dr. Bernardino António Bernardino de Almeida de 431, Almeida 4249 431,-015 4249Porto,-015 Portugal Porto, Portugal Even using only converters this problem persists because photovoltaic generation may contain unhoped bcUTFPR – Federal University of Technology - Parana, Campus Pato Branco, Via do conhecimento, KM 01, s/n, 85503-390 Pato Branco, Brazil CIETI - Center for Innovation in Engineering and Industrial Technology, R. Dr. António Bernardino de Almeida 431, 4249-015 Porto, Portugal fluctuations, while battery charging cannot have fluctuations. Therefore, the MPPT of the PV panel is not possible cUTFPR – Federal University of Technology - Parana, Campus Pato Branco, Via do conhecimento, KM 01, s/n, 85503-390 Pato Branco, Brazil without consideration of generated energy waste, if there isn´t an intermediate step of energy storage.

Abstract Abstract The power generation from photovoltaic sources is variable and may contain unhoped fluctuations, which can be relievedThe pow byer generationusing energy from storage photovoltaic systems. sources However, is variable there is anda technical may contain contradiction unhoped influctuations, extracting thewhich maximum can be powerrelieved from by usinga photovoltaic energy storage panel and systems. the charge However, cycle thereof a battery. is a technical To overcome contradiction this problem in extracting, this paper the presents maximum an improvementpower from a photovoltaicconsisting in panel a collaborative and the charge association cycle of aof battery. lithium To ion overcome batteries t handis problem supercapacitors, this paper showing presents the an technicalimprovement feasibility consisting in a photovoltaicin a collaborative system. association of lithium ion batteries and supercapacitors showing the Thetechnical structure feasibility of the inenergy a photovoltaic conversion system. system was developed and was set up the converter’s configuration, design andThe operationstructure ofsimulation the energy. The conversion power management system was of developed full system and i mplementationwas set up the wasconverter simulat’s edconfiguration, and the results design are Fig. 1. (a) PV panel power curve (b) Battery charge curve. presentedand operation. The simulation proposed .s ystemThe power development management and itof technical full system analysis implementation was carried was out simulatfor bothed situations and the results, with andare withoutpresented the. The use proposedof supercapacitor. system development It was concluded and it thattechnical the supercapacitor analysis was carriedin the photovoltaic out for both systemssituations bring, with better and The problem was analyzed in this study with an intermediate step of fast energy storage, provided by the use of a chargingwithout the conditions, use of supercapacitor. resulting in shorter It was charging concluded times that and the better supercapacitor system performances. in the photovoltaic systems bring better supercapacitor [7]. The idea of using a supercapacitor is to supply the power needed to charge the battery when the charging conditions, resulting in shorter charging times and better system performances. PV panel does not produce all the necessary power, or to absorb the excess of panel generation. © 2018 The Authors. Published by Elsevier Ltd. This© 2018 is an The open Authors. access Pu articleblished under by Elsevierthe CC BY Ltd.-NC -ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) 2. Methodology description SelectionThis is an andopen peer access-review article under under responsibility the CC BY- NCof -theND scientific license (https://creativecommons.org/lice committee of the 5th Internationalnses/by Conference-nc-nd/4.0/ on) Energy and EnvironmentSelection and Research, peer-review ICEER under 2018 responsibility. of the scientific committee of the 5th International Conference on Energy and The proposed design involves the use of supercapacitor in a Li-ion battery charger, using the solar energy from the Environment Research, ICEER 2018. PV panel, called in this paper as the Solar Battery Charger with Supercapacitor (SBCS). Keywords: battery charger; digital control; photovoltaic panel; supercapacitor The diagram of this type of charger is shown in Fig. 2, where the systems of control (SC), which control the direct Keywords: battery charger; digital control; photovoltaic panel; supercapacitor current converters (CCC), are represented in order to achieve the main objective of charging the battery. These control systems are coordinated by the power manager (PM), which reads the signals of generated power, current and voltage levels in the system, in order to continuously charge the battery even if there isn´t enough solar radiation. According to the diagram of Fig. 2, the PV panel converts the energy needed to charge the battery. We can see in

Fig. 2, the CCC1 is the direct current converter that performs the tracing of the maximum power point of the PV panel. * Corresponding author. Tel.: +351 919 652 799; fax: +351 228 321 159. The CCC2 bidirectional converter has the function of keeping energy in the supercapacitor when the photovoltaic * CorrespondingE-mail address: author. [email protected] Tel.: +351 919 652 799; fax: +351 228 321 159. panel generates excess energy and can´t be received by the battery. In addition, the CCC2 can manage power from E-mail address: [email protected] supercapacitor to charge the battery when the PV panel does not generate enough, in way of maximizing the generated 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. energy from PV panel. So, the supercapacitor performs the function of intermediate energy storage, a kind of energy 1876This -is6102 an open © 2018 access The article Authors. under Published the CC BYby Elsevier-NC-ND Ltd. license (https://creativecommons.org/licenses/by-nc-nd/4.0/) buffer function. Selection and peer-review under responsibility of the scientific committee of the 5th International Conference on Energy and Environment This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) The CCC3 converter has the objective of charging correctly the battery according to its manufacturer’s description, SelectionResearch, andICEER peer 2018-review. under responsibility of the scientific committee of the 5th International Conference on Energy and Environment Research, ICEER 2018. following optimum charging curves [8]. That combination of a supercapacitor and a battery to form an energy storage system reduces the stress on the battery caused by the high discharge currents, resulting in an increase in the life of the batteries [9].

82 Victor Barbosa et al. / Energy Procedia 153 (2018) 80–85 4 T. Nogueira et al./ Energy Procedia 00 (2018) 000–000

The MPPT implemented function was target, the maximum power point was reached for the system, as seen in the T. Nogueira et al./ Energy Procedia 00 (2018) 000–000 first chart in Fig. 3, where the Ppv curve overlaid the Ppv max. Another important issue is the battery current and voltage regulation by the CCC3 also reaching its objectives within a margin of tolerance, keeping whenever possible the SOC of the battery in constant growth, as seen in the third chart in Fig. 3. Transients in the current Ib and Iscap, are in the second chart, during the moment when the supercapacitor is charging and when it is discharging are justified by the fact that the CCC2 converter is changing their mode of operation in these transitions and the current in the inductor of CCC2 does not follow that exchange instantaneously. One of the most important results was the energy transfer from the supercapacitor to the battery when there was no power available from the PV panel, keeping the battery charge stable even when the supercapacitor is charged above 3 V, as seen in the fourth chart. It was also possible to verify that the battery through the two stages of charge, the first of constant current and the second of constant voltage, as shown in the fifth chart. In Fig. 4 we can see that system operated in state of charging the battery and supercapacitor, during the periods in which Ppv > Pbmin. It also operated in state of charging the battery and discharging the supercapacitor, when Ppv < Pbmin. With this, the system alternated between two states in most of time, maintaining the battery charge, that is, Cb being at zero, as seen in Fig. 4. Another verified characteristic is that the voltage regulation, VCC, does not need to be between 25 to 30 V as specified during the design of the converters, but only with values above the battery voltage, Vb, as seen on the fifth chart in Fig. 4. To perform this voltage regulation, was used the current that goes to the supercapacitor or the one Fig. 2. SBCS proposed design. supplied by it.

The basic operation of this system is based on four main states: i) charge only the battery, ii) charge the battery and discharge the supercapacitor, iii) charge the battery and supercapacitor and iv) charge only the supercapacitor. For these operation states, the MPPT function can be at on or off state, according to the current operation conditions. The supercapacitor discharges when the power generated by the PV panel is below the minimum required by the battery, Pbmin, helping to charge the battery. The supercapacitor is charged when the power generated by the panel is greater than Pbmin, taking advantage of the surplus energy generated. This happens because the MPPT function is running along with these steps, so the supercapacitor is charging and discharging. One concern about charging a typical Li-ion battery is to avoid an overvoltage. Because this is important, the battery voltage must be constantly monitored [9]. Finally, when the battery current reaches the floating current, Ibmin, means the battery has fully charged, then the charger is turned off [10], as seen in Fig. 2. It was implemented the SBCS circuit with the appropriate devices and operational components data [10] [11] [12] and the Psim electronic simulation software was used to analyses the work-flow.

3. Results and discussion

3.1. Case study 1 – Time from 0 to 120 seconds

From the SBCS performed simulation was obtained the operational quantities results and the output signals:

Nomenclature

3. Results and discussion

3.1. Case study 1 – Time from 0 to 120 seconds

From the SBCS performed simulation was obtained the operational quantities results and the output signals:

Nomenclature

SOC battery charge state Fig. 4. SBCS variables curves from study case 1. Ib battery current Fig. 3. SBCS variables curves from case study 1. Fig. 4. SBCS variables curves with PM output signals. Vb battery voltage Vscap supercapacitor voltage 3.2. Case study 2 – Time from 0 to 300 seconds VCC voltage CC Ppv power generated by the PV panel Another simulation was carried out with a slower variation of the solar irradiation, a system simulation from 0 to MPPT control on/off of de MPPT algorithm 300 seconds. The results are shown in Fig. 5. It was observed that SBCS works better for less abrupt variations of the Cb on/off battery control solar irradiation, means, the charging of the battery is done in a smoother way, without abrupt variations in the battery Iscap ref reference current in supercapacitor current, Ib. Given that solar irradiation over a one-day period varies at small rates [13], so SBCS reaches the battery charging requirements satisfactorily. The SBCS was obtained better performance in transitions of charging and For simulation time from 0 to 120 seconds, we can see in charts from Fig. 3 the results variation and, for the same time simulation, we can see in Fig. 4 the output signals of the PM. 84 Victor Barbosa et al. / Energy Procedia 153 (2018) 80–85 T. Nogueira et al./ Energy Procedia 00 (2018) 000–000 5 6 T. Nogueira et al./ Energy Procedia 00 (2018) 000–000 discharging of the supercapacitor, approximately in time 175 seconds and 280 seconds in the Fig. 5. 4. Conclusion For this case study we make a comparison between using or not the supercapacitor. As a result, the charging time increased, in addition to the wasted energy, since there is excess of generation. All difference between the energy In this work a photovoltaic battery charging system with supercapacitor was presented. The simulations were generated by the PV panel and the energy consumed by the battery would be wasted, since there would be no place to performed using the Psim software to check for the technical feasibility in the use of supercapacitors in photovoltaic store it without the supercapacitor. battery chargers. The simulation results carried out to control supercapacitor charge and discharge and for the extraction maximum power of the photovoltaic panel were verified. Battery charge was carried out continuously even for brief zero photovoltaic generation and the supercapacitor operated properly as an energy buffer. We observed that system worked properly for the frequent variations of the solar irradiation, keeping the objective of charging the battery continuously, even under adverse weather conditions. When submitted to a time of some minutes without any solar irradiation, supercapacitor was able to maintain the battery charge. We conclude for the effectiveness of the MPPT photovoltaic panel, the rapid response of the control system, the adequate storage capacity and the quick delivery of supercapacitor energy.

References [1] Kan, S.Y., Verwaal, M. and Broekhuizen, H. “Battery Capacitor combinations in photovoltaic powered products,” Journal of Power Sources, vol. 162, nº 2, 22, pp. 971-974, November 2006. [2] Manimekalai,P., Harikumar, R. and Raghavan, S. “An Overview of Batteries for Photovoltaic Systems,” International Journal of Computer Applications, vol. 82, nº 12, pp. 0975-8887, November 2013. [3] Marcos, V. Martínez, M. González, F. and Montero, M. “A Grid Connected Photovoltaic Inverter with Battery-Supercapacitor Hybrid Energy Storage,” MDPI - Multidisciplinary Digital Publishing Institute, Sensors, vol. 17, nº 8, 2017.

[4] Zuo, W., Li, R., Zhou, C., Li, Y., Xia, J. and Liu, J. “Battery‐Supercapacitor Hybrid Devices: Recent Progress

and Future Prospects,” Advanced Science, open access, February 2017.

[5] Rodrigues, M., Brito, M., Nogueira, T. and Martins, F. “Modeling and Simulation of a Three-Phase Inverter to Inject Energy in Grid from Photovoltaic System,” em 6th International Scientific Conference, Renewable Energy Sources, Tatranské Matliare, Slovak Republic, 2016. [6] Dandoussou, A., Kamta, M., Bitjoka, L., Wira, P. and Kuitché, A. “Comparative study of the reliability of MPPT algorithms for the crystalline silicon photovoltaic modules in variable weather conditions,” Journal of Electrical Systems and Information Technology, vol. 4, nº 1, pp. 213-324, May 2017. [7] Bonkoungou, D., Koalaga, Z. and Njomo, D. “Modelling and simulation of photovoltaic module considering single-diode equivalent circuit model in matlab,” International Journal of Emerging Technology and Advanced Engineering, vol. 3, nº 3, pp. 493-502, March 2013. [8] Park, S., Koh, B., Wang, Y., Jaemin Kim and Chang, N. “Maximum power transfer tracking in a solar USB charger for smartphones,” em Low Power Electronics and Design (ISLPED), IEEE International Symposium, EUA, 4-6 Sept. 2013. [9] Ongaro, F., Saggini, S. and Mattavelli, P. “Li-Ion Battery-Supercapacitor Hybrid Storage System for a Long Lifetime, Photovoltaic-Based Wireless Sensor Network,” IEEE Transactions on Power Electronics, vol. 27, nº 9, pp. 3944-3952, Sept 2012.

Fig. 5. SBCS variables curves from case study 2. [10] Chem, LG, “Rechargeable Lithium Ion Battery, Model : 18650HE4 2500mAh,” LG Twin Towers, Product Specification, Document n. BCY-PS-HE4-Rev0, Seoul, Republic of Korea, 150-721, 2013. Another point still analyzed is in the period which the power generated by the panel is less than the minimum for [11] Komaes EUA, “Komaes Solar,” Especification sheet: Solar Module - KM(P)20, 10, 2016. [Online]. Available: the battery charge, Ppv < Pbmim, when there aren´t enough power to charge the battery, so the current Ib goes to zero, http://www.komaes-solar.com/. [Acedido em 2018]. so the battery would take longer to charge. For this case study with supercapacitor, the battery has loaded up to just over 5% of its total charge. In case of simulation without the supercapacitor, the battery charged up to about 3,6%. [12] Maxwell Technologies, “16V Small Cell Module,” Document number: 1015371.6, 2014. In the case study with supercapacitor, for finishing the first step of battery charging where the current is constant [13] Burgess, P. “Variation in light intensity at different latitudes and seasons, effects of cloud cover and the and goes until the battery reaches 65%, it will take approximately 65 minutes. Considering the system without the amounts of direct and diffused light,” em Continuos Cover Forestry Group Scientific Meeting, UK, 2009. supercapacitor, at the same 300 seconds, the battery charged about 3,6%, reaching to 65%, will take about 90 minutes. We can say that the system without supercapacitor takes about 38,46 % longer to charge the battery. These analyzes were performed observing that, in this case, the relation between the time in which Ppv > Pbmin, time Tb, and the total simulation time Tt, the relation Tb/Tt, was of 0,623. Victor Barbosa et al. / Energy Procedia 153 (2018) 80–85 85 T. Nogueira et al./ Energy Procedia 00 (2018) 000–000 5 6 T. Nogueira et al./ Energy Procedia 00 (2018) 000–000 discharging of the supercapacitor, approximately in time 175 seconds and 280 seconds in the Fig. 5. 4. Conclusion For this case study we make a comparison between using or not the supercapacitor. As a result, the charging time increased, in addition to the wasted energy, since there is excess of generation. All difference between the energy In this work a photovoltaic battery charging system with supercapacitor was presented. The simulations were generated by the PV panel and the energy consumed by the battery would be wasted, since there would be no place to performed using the Psim software to check for the technical feasibility in the use of supercapacitors in photovoltaic store it without the supercapacitor. battery chargers. The simulation results carried out to control supercapacitor charge and discharge and for the extraction maximum power of the photovoltaic panel were verified. Battery charge was carried out continuously even for brief zero photovoltaic generation and the supercapacitor operated properly as an energy buffer. We observed that system worked properly for the frequent variations of the solar irradiation, keeping the objective of charging the battery continuously, even under adverse weather conditions. When submitted to a time of some minutes without any solar irradiation, supercapacitor was able to maintain the battery charge. We conclude for the effectiveness of the MPPT photovoltaic panel, the rapid response of the control system, the adequate storage capacity and the quick delivery of supercapacitor energy.

[4] Zuo, W., Li, R., Zhou, C., Li, Y., Xia, J. and Liu, J. “Battery‐Supercapacitor Hybrid Devices: Recent Progress

and Future Prospects,” Advanced Science, open access, February 2017.