Impact of EV charging patterns on FRR provision and energy storage
capacity requirements
Abstract
To cut down on carbon emissions, EVs are utilized instead of conventional cars. The rate
at which EVs are adopted has an effect on the electricity grid. This is because EVs are peak-
demand increasing loads. This thesis examines the impact of installing battery storage systems
and the load on the electric chargers at an Uppsala parking garage. The power bill is assessed in
light of the estimated cost of consumed electricity at various battery storage system (BSS)
capacities. The information for this study came from a 2021 study of a parking garage in
Uppsala. There are 30 individual charging stations and 60 individual charging outlets. The
parking garage is also wired into a photovoltaic system that includes two battery racks totaling
137 kilowatt hours. According on the findings, loads with BSS units installed are less expensive
than those without. The electricity bill can be lowered to a specific limit by examining the
system under different battery capacities. But, after 137 kWh, there is no correlation between
increased storage capacity and lower power rates. The size of the PV system and the expected
number of EVs to be charged would have a significant impact on the upper capacity limit of the
BSS unit. Costs may be drastically cut by regulating charging and discharging times.
Keywords: Impact, Electric Vehicles, Charging Patterns, FRR Provision, Energy Storage
Capacity.
1. Introduction
Smart grids, the next generation of electrical distribution infrastructure, are increasingly
being put into place. The electric distribution system is made more secure and reliable thanks to
the smart grid, which utilizes many generating alternatives that interact with energy
management. With the smart grid, we can run our power grid more efficiently and dependably
than ever before. In addition, smart grid technology may help businesses lower their operating
expenses and cut their carbon footprint. Modern regulated loads, electric cars, and alternative
energy sources can all be seamlessly integrated into the smart grid (Adil, 2021).
The need of power supply security with quality, the desire to minimize electricity prices,
and the unpredictable output of renewable energy sources are just a few of the rising difficulties
that have distribution system operators thinking about energy storage systems (Kelman, 2010).
Battery storage, compressed air storage, pumped hydro storage, super magnetic storage, super
capacitors, and flywheels are all examples of energy storage system technologies. Which
technology is best for a given situation is determined by factors including personal taste, budget,
and safety. Because of its portability and relative cheapness compared to competing
technologies, battery energy storage is being examined in this research (Afshar, 2021).
There are major issues with the current energy paradigm for land transportation, which is
dependent on petroleum products like gasoline and gasoil. The primary source of air pollution in
urban areas, which can have negative effects on the health of city residents, is the use of these
fuels in internal combustion engine vehicles (ICEVs). Air pollution is a serious problem that has
been linked to a variety of health issues, including asthma attacks, heart attacks, strokes,
metabolic disturbances, and even diabetes. Because of this, governments are giving initiatives to
create low-emission automobiles additional support. When these fuels are used, they release
greenhouse gases (GHG) like carbon dioxide (CO2), which contribute to global warming (Leou,
2013).
In addition to environmental concerns, economic and political factors must be
considered. Oil prices have increased as a result of a decline in petroleum and natural gas
production capacities. To lessen its reliance on foreign oil, India is encouraging the use of
alternative energies for vehicular travel. In this light, many have started to realize that ICEVs
aren't the transportation mode of the future. As a result, in the last few decades, substitute
vehicles have been under development (Zakariazadeh, 2014). One of the most impressive is the
use of EVs, or electric automobiles. The changing needs of electric cars will raise future loads as
a result of their widespread adoption and use within distribution networks. By enabling
customers to use their electric vehicles in vehicle-to-grid (V2G) mode, the smart grid's
sophisticated technology and services help bring down the system's operating costs (Saboori,
2015).
2. Research Methodology
Economic and technological challenges benefit greatly from statistical or data analysis of
any project or technology; this provides a wealth of information that can be used as indicators of
the near and distant future of this technology; it also facilitates research and development. In this
plan, an enclosed parking garage will store recharging stations for electric cars. Both the
electrical grid and the PV station installed on the parking garage's roof supply the facility with
electricity.
Figure 1: Battery flowchart. Nighttime and PV system extra electricity charges the battery.
Tools
The initial dataset for the charges will last 13 months, commencing in January 2021 and
ending in January 2022. The information was accessible in Excel. The file stores the daily three-
phase voltage and current measurements taken during the various charging sessions. This
evaluation is performed in MATLAB.
Program
The next sections go down each stage of the code. There are two primary components to
the coding in this project. The initial phase, devised by Alexander Wallberg, was to import and
prepare the EV data. The subsequent action is to bring in PV data. In the third phase, we did the
analysis and subtracted EV from PV, and in the last step, we did the calculation of the price of
power before and after adding the batteries. The first two stages of the code are included in the
first section, while the second part comprises the last two phases.
All the data should be proper before beginning the analysis because it will serve as a
foundation and point of reference for future research. To begin, we'll open the Excel file, which
contains one month's worth of data at a time, and import the information for the month of our
choosing. The data is taken every 30 seconds during the month. Months like January, May, July,
and September are selected at random for this purpose. These three clusters include two, three,
and four months, respectively. The first category includes months like January, when no solar
energy is produced. Months like May and September fall into the second category of middling
PV generation.
The last category includes peak PV months like July and August. The study is conducted
on these subsets to illustrate the efficacy of battery installation and its impact on the bill.
𝑃1 = 𝐼1 ∗ 𝑉1 eq. (1)
𝑃2 = 𝐼2 ∗ 𝑉2 eq. (2)
𝑃3 = 𝐼3 ∗ 𝑉3 eq. (3)
𝑃𝑡𝑜𝑡𝑎𝑙 = 𝑃1 + 𝑃2 + 𝑃3 = (𝐼1 ∗ 𝑉1 ) + (𝐼2 ∗ 𝑉2 ) + (𝐼3 ∗ 𝑉3 ) eq. (4)
Power was measured in watts (W), voltage in volts (V), and current in amperes (A).
Each vehicle's charging session ID is displayed in the received data. Each month, we can
determine if the parking space is adequate for the cars by calculating the number of charging
session IDs and comparing the results to see if we need to refurbish. The initial step was to
import all PV data into MATLAB, as the data received was in Excel files for each day. The data
for the selected month was then loaded by appending the total number of days across all months
to an array.
The addition of energy storage to the system is investigated, and the cost of power is
determined, as one of the goals of this thesis. The PV power generated, including the battery
capacity, must be minus the power used by the EVs. This will allow the parking lot's
contribution to the national grid's power needs to be calculated. In Figure 2, we can see how
much energy is used by EVs and how much is produced by the PV system. The battery will serve
an important function in the parking garage system, as it will not only store the day's extra power
but also charge at night when energy costs less and discharge during the day when rates are
higher.
Figure 2: kW with a temporal resolution of 15 min” is the total of EV power usage and PV
system power in May 2021.
Vatten fall Corporation, one of the power providers, defines the electricity bill as follows:
𝐵𝑖𝑙𝑙 = 375 + 37 ∗ (𝑋) + 0.48 ∗ (𝑌) + 0.144 ∗ (𝑍) eq. (5)
Where the first term (375) is the monthly fixed amount, X is the maximum consumption,
the second term is the high load cost, Y is daytime power consumption, and Z is nighttime power
consumption.
3. Results
The code produced intriguing and distinct outcomes. Results plotted by month or season
indicate how outcomes have varied. The following themes demonstrate our various results:
EV Consumption Analysis
The thesis analyzes EV and parking power usage. How many parking facilities charge
cars daily or monthly? Figure 3 illustrates the number of automobiles charged in different 2021
months.
Figure 3: Number of charging events for each month during 2021
Figure 4 depicts September 2021 power usage for technical information. September had
the most parking tickets. The highest value was 76.3kW/30Sec on 3 September, indicating
numerous automobiles were charging at once.
Figure 4: EV power consumption in September 2021, the unit is “kW with a time
resolution of 30 sec
PV System Power Generated Analysis
The parking house has a PV system on the roof that generates electric power and supplies
it to the charging stations in the parking. The idea is perfect to have a hybrid system for the
parking, and we can use a renewable energy source to supply electricity instead of the electric
grid, which supports sustainability and gives us free electricity. In January, electricity generation
dropped to zero, but in July, the sun shone most of the day, generating power all day.
Figure 5: In July 2021, PV power was "kW with a temporal resolution of 15 min."
Figure 6: In January 2021, PV power was "kW with a temporal resolution of 15 min."
Adding Energy Storage to the system
By using as little power as possible, the parking lot may save money. If we could
determine the appropriate battery capacity for parking, energy storage was a suitable answer. The
system features a 137-kWh battery. Figures 7(a) and 7(b) show August without and with
batteries. The plot in figure 7(a) illustrates the subtraction of generated PV power and EV
consumption, whereas figure 7(b) adds the battery status to the system in the positive section of
the plot. PV power data was recorded every 15Min during the day, whereas EV data was every
30Sec. Hence, the average EV gathered data per 15 minutes was determined for PV power
analysis.
Figure 7 (a): Power flow from the parking house, where the positive numbers represent EV
charger power demand and the negative values are PV system excess electricity
transmitted to the grid in August 2021 without utilizing the battery
Figure 7(b): Power flow from the parking house, where positive values represent EV
charger power consumption and negative values are PV system excess electricity delivered
to the grid with batteries in August 2021
Impact of using the Battery
The battery has allowed for less reliance on the utility grid for power. The amount of
energy saved by the battery in August of 2021 is displayed in Figure 8. When the EV's power
needs exceed the PV system's output or when there is no PV output, the battery stores the extra
electricity provided by the PV system for later use.
Figure 8: In August 2021, the battery lowered power usage by kW with a 15-minute
resolution
Electricity Price
This thesis calculated power prices. Several variables affect monthly price changes. The
parking house uses solar electricity instead of grid power. PV electricity may not cover power
usage certain days, but it minimizes grid power consumption. Because the sun shines most in
spring and summer, the parking only generates PV electricity in these months. Only spring and
summer benefit the PV system. Otherwise, the parking house uses all grid power. Hence, energy
storage is applied in the parking house, as mentioned before.
The battery will charge inexpensively at night and drain at peak energy prices. to
calculate battery savings. Our MATLAB code explaining January 2021 electricity prices without
and with batteries. The battery reduced the price from 1367.3 SEK to 814.68 SEK. The code
utilized the parking house's 137 kWh battery capacity.
4. Conclusion
This experiment examined how battery storage affects the system and power bill.
Installing a battery reduces power costs significantly. Charging occurrences occur more during
the day than at night, especially during working hours. Which future V2G research point and
how to employ EVs in the parking house to support the grid? Nonetheless, PV electricity
generation has grown and peaks in summer and is nearly negligible in winter. In summer, the
battery storage unit is not charged at night, which has a major economic impact on the system. In
January, the battery charges fully from the power grid at night, lowering the electricity cost. Day
and night kWh prices differ by 0.48 SEK/kWh and 0.144 SEK/kWh, respectively. The storage
system charges at night and from extra electricity between May and September. After charging
the battery to 80%, surplus electricity is sold to the grid, lowering the bill.
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