The movement to electric vehicles (EVs) is a major stop along the way to green transportation. In parallel, nations are also setting aggressive goals to decarbonize the electric grid. For example, the US aims to create a net-zero carbon energy supply system by 2050. While EVs do not produce greenhouse gases at the tailpipe, until the grid is completely green, every mile driven by an EV creates carbon dioxide indirectly from the power they consume. This premise is true whether from home or using commercial charging stations powered by the grid. An open issue exists. Many countries’ current grid could not sustain the projected increase in transportation electric demand. This consumption is in addition to industrial and heating electrification and the surging electric demand from data centers.With this backdrop, the King Abdullah Petroleum Studies and Research Center or KAPSARC studied the issue. The intent was to produce alternatives to alleviate the dual problem of grid capacity and less-than-green grid charging of EVs.KAPSARC is a non-profit think tank in Riyadh, Saudi Arabia. It conducts independent research on energy economics and sustainability. It heavily used geographic information system (GIS) technology to study the best location throughout Riyadh to site off-grid EV charging stations. 
How Green Are EVs?
It depends.Using the US as an example, buyers of vehicles measured efficiency in miles per gallon or MPG. The higher, the better. To help EV buyers, the US Environmental Protection Agency (EPA) conjured up a term called miles per gallon electric or MPGe. It helps compare EV efficiency to gas-powered cars. The EPA used the energy equivalent of 33.7 kilowatt-hours to one gallon of gasoline to derive the measure. Available EVs range from less than 50 MPGe to nearly 150 MPGe.How green is the grid today? The US electric energy system emits 0.86 pounds of CO2 for every kilowatt-hour consumed.An EV can travel 100 miles, consuming between 40 and 60 kilowatt-hours, depending on its efficiency. That adds up to a carbon footprint of about 35 and 50 pounds for every 100 miles driven.So, while EVs certainly lower greenhouse gas emissions, EVs will continue to emit CO2 until the grid is completely green. Thus, charging EVs off-grid with a charging mechanism based on 100% renewable energy creates EVs that produce no tailpipe emissions and none from the charging power.The Green EV Charging Station
The study’s premise was to propose an off-grid method of charging EVs. This method provides completely green charging for EVs and does it without burdening the existing grid. KAPSARC’s study determined how many locations can accommodate off-grid green charging stations.The study proposes a combination of four components and four alternatives. Instead of the conventional commercial station tapping into the existing grid, it uses a microgrid solution consisting of:- Photovoltaic (PV) cells (solar arrays)
- Wind turbines.
- Batteries
- Hydrogen generation by electrolysis, hydrogen fuel cells, and hydrogen storage
- PV, Batteries, and Wind
- PV, Batteries, Wind and Hydrogen
- PV and Batteries
- PV, Batteries, and Hydrogen
The proposed green charging station consists of four components.
The study proposes relatively small charging station modules, limited to a capacity of 60 to 66 kW and able to house 6 level 2 chargers. Each charging station could accommodate 6 EVs for several hours. This study did not consider high-capacity DC charging stations due to space limitations. The hydrogen component does two things. First, it uses excess electricity generated from the solar and wind components to produce hydrogen. Two, it stores excess hydrogen to be used later by generating electricity using hydrogen fuel cells. The premise of the study is that these charging stations are off-grid.Why Location Matters
The team limited the study area to Riyadh, the kingdom’s capital and largest city. Finding the space to locate the facilities in an urban setting is hard. The study team looked to GIS to solve the problem. It obtained a rich land parcel dataset of Riyadh from the Royal Commission for Riyadh City. This dataset provided a detailed representation of all land parcels in Riyadh, including their designated use (i.e., residential, commercial, industrial, etc.) and area. The analysis determined the footprint of each of the parcels.
The study team leverages a detailed map of Riyadh’s parcels for analysis.
The study team used Esri’s ArcGIS Pro for the spatial analysis. The focus was on hospitals, universities, schools, shopping malls, and gas stations. The idea was that level 2 charging stations could be conveniently located in areas where people would tend to spend time charging.The thorny issue in an urban environment is the footprint of the charging station, particularly for the solar arrays. The study assumed that 110 watts of solar energy is needed for about 1 square meter of footprint. For example, a 66kW charging station would require six hundred square meters of solar arrays if it only used solar arrays.The team used GIS to compare the various alternatives. While alternative C had the lowest present value cost, the available land was limited.
Using just solar and batteries limited available parcels.
However, even though the use of hydrogen was more expensive today, the team felt that hydrogen generation would continue to improve and costs would drop as the technology continued to mature. Wind was also considered, but its use is limited in an urban environment. Adding hydrogen increased the number of sites that could house the charging station with the same reliability and kW hour capacity.
Adding hydrogen to the mix increased the number of available sites for the charging stations.
The study examined various combinations of these technologies. The main study factors included costs, reliability, capacity, and the footprint of the proposed facility.