38. NEKONVENČNÍ ZDROJE ELEKTRICKÉ ENERGIE
DESIGNING PROPER RESIDENTIAL PHOTOVOLTAIC SOURCE FOR COMMON CHARGING OF ELECTRIC CAR Pavel Šimon1, Mária Pálušová2 1 Institute of Aurel Stodola, Faculty of Electrical Engineering, University of Žilina, ul. kpt. J. Nálepku 1390, 031 01 Liptovský Mikuláš, Slovakia, Tel.: +421 917 714678,
[email protected] 2 Institute of Aurel Stodola, Faculty of Electrical Engineering, University of Žilina, ul. kpt. J. Nálepku 1390, 031 01 Liptovský Mikuláš, Slovakia, Tel.: +421 …..,
[email protected]
Abstract Article describes algorithm of designing possible PV systems for common daily electromobiles charging. It shows what need to be considered during this design. There are common principles described, and what result could be achieved. Introduction Two trends are to change of hundred years of energetics – A. RES local production and B. electric based mobility. From heavily centralised production and transportation based on business giants to local, decentralised production close to its consumption [1]. On other hand RES production is highly volatile. Growing number of electric cars is pushing consumption to places in distribution network where were not common such load. Those are global trends, but how can new EV owners use those on personal level? How to properly design residential RES (usually PV source) to cover charging of daily EV charging needs. How would be EV usually charged Electromobility can bring “fuelling” cars closer to place where are usually parked. Transporting electricity to our homes is easy and common for decades. This will allow charge EVs almost immediately when they arrive at destination – home. But are EV really charged after coming home from work? We expected that, but we do not know for sure. Thus, IAS starts survey in between EV owners [2]. Slovakia has more than 700 electric vehicles – battery only, or plug-in hybrid. About 200 were available before start of supporting program [3] and during this support was additional 521 EV bought [3]. Additional 112 are on waiting list and had made reservation of support. Preliminary result of survey Up to now (15th April 2018), only 5 % of EV owner filled survey, thus is still only preliminary result. But it shows, that assumption of home charging is fulfilled – most of EV owners charge at home or in company. As result shows, the most of EV owners is charging at home (52.6 %) or in company (28.9 %), only 15.8 % of EV is charged in public chargers (TESLA super charger, GreenWay net, ZSE chargers, …). Majority of charging is done on 1 phase up to 4.6 kW, and only 10.5 % is usually traveling more than 100 km in a day. Even 7.9 % EV owner has no daily routine.
Result are still preliminary, but we can make small conclusion, that except place of charging, EV owners will not much change their travelling habits, when they change from ICE (Internal Combustion Engine) to EV. But how energy will flow to those cars is crucial point of new energy model. Energy in ICE mobility is centrally distributed to petrol stations, and drivers are usually filling their fuel tank only when is going empty – not after any routes. But charging habit are different – EV is usually charged daily and at home [4]. Common amount of needed energy As survey show, common route for EV is trip from home to work and back. Majority of those are less than 100 km daily. Some of those are charged only at home (1st scenario), some are charged in company charging points too (2nd scenario). Based on available types of electromobiles, their average consumption varies between 10 kWh/100 km (0,1 kWh/km) to 20 kWh/100 km (0,2 kWh/km). Combination of mentioned data conclude in obvious daily energy needs in Table 1. Table 1 Average daily EV consumtion on common routes Average EV consumption
1st scenario daily trip (up to100 km)
2nd scenario daily trip (up to50 km)
[kWh/km]
[kWh]
[kWh]
0,1
10
5
0,2
20
10
Table 1 shows that common daily route will require between 5 kWh to 20 kWh of recharging after its finish. This gives background for designing reasonable PV systems for charging. Design of PV system – capacity of energy storage The most important point for designing PV system is knowledge on produced energy requirements. After concluding this answer, there can be used many methodologies. One of them is to design it via number of panels [5]. Other possibility is established in another source, for example in [6]. Previous chapter stated, that daily energy need will vary between 5 to 20 kWh. Unfortunately, there is discrepancy in residential PV source placement and common daily staying of EV. As survey shows, EV owners are placing their EV in companies during day. This significantly influence PV system design – without storage included system will not be suitable for late afternoon charging. Through this, first point of PV system design is including adequate amount of storage capacity. EV and PV source owners need to have exact knowledge of their common daily trip and EV usual consumption. Let say using 1st scenario (EV would be charged only after returning => about 100 km daily trip) and less powerful EV – 0,1 kWh/km consumption. Than, storage included in PV system is 10 kWh of utilizable capacity (which is different form nominal) [7]. Design of PV system – PV power During designing of PV system for residential EV charging grow another question: for what period PV charging will be used (winter or summer)? Publicly available PV calculating source PV-GIS [8] shows, that PV production is significantly different on any season (see Figure 1).
Figure 1 PV-GIS output in real place of Slovakia Graph on Figure 1 shows, that each month of PV production is different. Even this graph shows only expected production based on calculating method [8]. But in our region is concluded, that usual summer daily production is about 6 to 7 hour of “full” capacity (6 – 7 kWh/kWp), on other hand during winter, usual daily production could fall to 1 or less hour of “full” capacity (1 kWh/kWp) [9]. Based on answer of question “which season would like EV owner use his own energy?”, PV source need be designed. For summer consumption is easy to use about 2 kWp of PV source. This will give included storage (10 kWh, see above) full charge. Even 2 or 4 kWh could be used for in house consumption. Unfortunately, during winter season will not be suitable for proper charging. 2 kWh would give somewhere between nothing to 4 kWh of energy. When EV owner likes charge its car during winter season, then PV source need to be designed to be compatible with storage. This mean 10 kWh of battery will need 10 kWp PV source. In that design is high probability of full battery for daily routes. But during summer PV system would have big over production. It could produce 60 to 70 kWh and only 10 kWh would be stored in battery. There could be some self-consumption in house, but usually not that high. In our region (Slovak or Czech Republic) is legally difficult to give overproduction to grid without interacting with grid operator. Even for free is not possible to feed to grid. This give summer design of EV charging system some difficulty. But modern investors have great option – possibility to control PV output based on consumption. Unfortunately, usually this will end in installing higher level control system. This system will control PV system, storage, in-house consumption and some else technology. Conclusion Price of electricity produced in nowadays PV system without storage is below end user electricity price. This could inspire EV owners to build their PV systems for charging. But as was written above, PV system without battery will not make sense for EV owner. That ended in necessity of including any type of battery to PV system design. During PV system design need to be two important questions answered: 1. How many daily energies need to be charged to EV (distance and EV consumption will give answer); 2. Which season is preferable to charge – winter of summer? Those two questions have highest influence on PV system design.
References [1] P. Šimon, “What chalenges will massive use of EV brings (Aké výzvy prinesie masívne nasadenie elektromobilov),” EnergiaWeb.sk, 2017. [Online]. Available: https://www.energiaweb.sk/2017/04/09/ake-vyzvy-prinesie-masivne-nasadenieelektromobilov/. [2] P. Šimon, “Research of influence of EV to energetics (Výskum vplyvu elektromobility na energetiku),” Inštitút Aurela Stodolu v Liptovskom Mikuláši, 2018. [Online]. Available: https://lm.uniza.sk/~simon/elektromobilita.html. [3] Automotive Industry Association of the Slovak Republic, “Support of electric vehicles,” Automotive Industry Association of the Slovak Republic, 2018. [Online]. Available: https://www.zapsr.sk/podpora-elektrickych-vozidiel/informacia-o-alokovanychprostriedkov/#bxe_green_line. [4] P. Šimon and P. Tauš, “How to create synergy between electromobility, grid operators and RES,” in RESpect 2018, Poráč, 2018. [5] L. Ladányi and Z. Dostál, “Design of the PV system according to the PV panel field,” in RESpect 2018, Poráč, 2018. [6] R. Rybár, P. Tauš and M. Cehlár, Solárna energia a jej využitie I., Košice: Edičné stredisko Fakulty BERG, TU v Košiciach, 2009. [7] P. Bača, “Přehled možností akumulace elektrické energie z OZE,” in Alternatívne zdroje energie ALER 2011, Liptovský Ján, 2011. [8] European Union, “PHOTOVOLTAIC GEOGRAPHICAL INFORMATION SYSTEM (PVGis),” 1995-2017. [Online]. Available: http://re.jrc.ec.europa.eu/pvg_tools/en/tools.html. [9] P. Tauš, J. Tomčejová, M. Horváth, P. Šimon and S. Karabinoš, Odborná príprava pre oblasť obnoviteľných zdrojov energie, Košice: TUKE, 2014.
