Assessing the CO2 emissions associated with the Electric cars: Towards the implementation of renewable energy at electric vehicles charging stations

By: Sadah A. T. Muawad , Department of Mechanical Engineering, College of Engineering, Sudan University of Science and Technology, Khartoum, Sudan

What is the electric car?

Electric cars are electric vehicles (EVs) that have an electric motor to convert electricity to kinetic energy to drive the car instead of using an internal combustion engine that runs on petroleum fuel. The vehicle uses a large traction battery pack to store electricity and to power the electric motor and the battery needs to be charged regularly. As EVs uses electricity to run the motor, they emits no exhaust fumes. The vehicles does not contain the typical liquid fuel components, such as a fuel pump, fuel line, or fuel tank[1] The U.S. Environmental Protection Agency classifies all battery electric vehicles (BEVs) as zero-emissions vehicles[2]. Compared to internal combustion engine vehicles EVs have significant lower environmental impacts, improving the electricity mix is a great opportunity to improve EVs industry. Reducing energy consumption by EVs at different stages like EVs manufacturing process and EVs weight will drastically reduce the impacts linked to electricity generation[3]. BEVs emit no greenhouse gases (GHGs) in the driving stage; however, depending on the electricity mix the amount of GHGs emitted is vary at power generation stage.  Most of the life cycle assessments (LCAs) suggest that the (electricity generation and transmission, battery charging and driving the electric motor) GHGs emissions per kilometer in Europe is lower for BEVs as compared to internal combustion engines vehicles and hybrid cars. Based on the carbon intensity of the European Union the electricity mix in 2015, (electricity generation and transmission), battery charging, and driving range, GHGs emissions per kilometer of mid-sized BEVs are estimated as 60 to 76 g CO₂e/km compared with 143 g CO₂e/km for mid‑sized internal combustion engines vehicles. This shows that BEVS have emissions between 47 % and 58 % lower than conventional cars[4].

History of Electric cars industry [5]:

• (1828 — 1835) First small-scale electric car: Innovators in Hungary, the Netherlands and the U.S, build a small electric car, thinking in future.
• (1889 — 1891) First electric vehicle debuts in U.S: William Morrison, built the first vehicle which runs with electricity.
• (1901) World’s first hybrid electric car Is invented: Ferdinand Porsche build the first hybrid electric car, runs on electricity stored in a battery and a gas engine.
• (1996) GM develops the EV1 electric car.
• (1997) Hybrid cars mass production: In 2000 Toyota introduces and releases Prius worldwide.
•  (2010) The Nissan LEAF model: In December 2010, the company releases the Nissan LEAF model, EV with zero driving emissions.

Electric cars categories [6]:

There are three main categories of EVs, based on the dependence on electricity.

• Hybrid Electric Vehicles (HEVs): In this type both petroleum fuel and electricity are used to provide power. The braking system generates electric energy which is used for battery recharging. The electric motor and the internal combustion engine are controlled by computer system that ensures economic driving.
• Plug-in Hybrid Electric Vehicles (PHEVs): PHEVs use both petroleum fuel and electricity to power the car. The battery in this type maybe recharged through the braking system or plugging-in to an external electrical source. In PHEVs the internal combustion engine is used to recharge the battery resulting in extended range.
• Battery Electric Vehicles (BEVs): BEVs are fully electric vehicles which use an external electrical source to recharge the battery with no petrol engine.

Calculation of electric car CO₂ emissions

To recharge EVs battery you need to be plugged in to an EV charger which is connected to the electrical grid. EV chargers convert AC electricity to suitable voltage and current level for charging the EVs battery system. There are two main types of EV chargers: AC and DC, and each has its unique characteristics in terms of input, output, charging speed, and cost. Since all electric energy comes from the national grid, the electricity charging the batteries in an EV usually comes from power plants that run on fossil fuel, results in CO₂ emissions.

How much are the CO₂ emissions from EVs?

A simple analysis was conducted to answer this question. The Nissan leaf model was selected to assess the CO₂ emissions using the NEXXTLAB model which is a CO₂ fumes calculator designed to estimate the energy-related emissions of EVs. The model pays attention to the correctness of the calculations and retrieved values from different studies (for further information see reference (5)[7]). The following assumption were considered:

• Average electricity consumption by the EV is 16.50 kWh/100km.
• Total battery capacity is 40 kWh.
• Source of electricity for charging the EV is electricity mix of the United Kingdom. In 2018 the electricity has been generated from oil and other 2.8%, Coal 5%, Nuclear 19.5%, Gas 39.4% and Renewables 33.3% [8].
• Grid-to-battery conversion efficiency is 83% [9].

Based on these assumptions, it was found that the annual CO₂ emission of Nissan leaf model is [1,860 kg CO₂/yr.] (Which include power generation, transmission losses, and charger losses). It was also found that the annual CO₂ emissions can be reduced to 160 kg CO2/yr. if all the electricity required is provided from a local PV installation. The NEXXTLAB  model assumes that the emissions factor for locally produced electricity from small scale photovoltaic installations 55g CO₂/kWh [7]. If the national grid is more diversified with renewable energy electricity such as from hydropower and wind energy, the CO2 emissions from EVs can be further reduced. Based on this we can conclude that depending on electricity mix at each country the electric car’s CO₂ emissions will vary.

References

1. Alternative Fuels Data Center. How Do All-Electric Cars Work?  [cited 2020 30th March]; Available from: https://afdc.energy.gov/vehicles/how-do-all-electric-cars-work.
2. Alternative Fuels Data Center. All-Electric Vehicles.  [cited 2020 30th March]; Available from: https://afdc.energy.gov/vehicles/electric_basics_ev.html.
3. Maarten Messagie, Life Cycle Analysis of the Climate Impact of Electric Vehicles. 2017. Available from: https://www.transportenvironment.org/sites/te/files/publications/TE%20-%20draft%20report%20v04.pdf
4. European Environment Agency, TERM 2018: Transport and Environment Reporting Mechanism (TERM) report, in Electric vehicles from life cycle and circular economy perspectives. 2018: Luxembourg.
5. U. S. Department of Energy. Timeline: History of the Electric Car.  [cited 2020 30th March]; Available from: https://www.energy.gov/timeline/timeline-history-electric-car.
6. Ergon Energy. Types of electric vehicles.  [cited 2020 31th March]; Available from: https://www.ergon.com.au/network/smarter-energy/electric-vehicles/types-of-electric-vehicles.
7. NEXXTLAB. CO2 emissions calculator.  [cited 2020 31th March]; Available from: https://www.nexxtlab.lu/co2-emissions-calculator/.
8. Department for Business- Energy and Industrial Strategy, STATISTICAL PRESS RELEASE, in UK Energy Statistics, 2018 & Q4 2018. 2019: 1 Victoria Street, London SW1H 0ET.
9. Karlsson, S. and D. Kushnir, How energy efficient is electrified transport? 2013.

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