Transport Trajectory

For the built environment one of the issues is the electrification of vehicles and the resultant demand for electricity for charging as part of the services infra-structure. This presents both challenges and opportunities. Challenges in providing power and charging points as part of the infrastructure and opportunity in the flexibility of load and the possibility of power sharing and load matching between buildings, embedded energy assets and the vehicles.

While deep decarbonisation of transport is a real challenge new developments and retro-fit projects can contribute to the process and in doing so achieve netzero across the development

In the first instance new developments should be designed to reduce necessity for transport and introduce walking and cycling opportunities to reduce commuting demand at source.

The idea of a “Smart microgrid” concept offers the opportunities for low carbon transport, including automated vehicles, shared ownership and using IT smart data system to manage the provision of public transport services. Although starting from a low base In the near and medium terms, it is anticipated that there will be an increased penetration of BEV’s into the UK car and light vehicle fleet. This in turn, will drive demand for local charging points. 

These can be integrated into the local smart micro-grids, providing complementary loads, opportunities around V2G and additional investment opportunities for infra-structure operators. 

Nation Grid produced estimates of the penetration of BEV’s into the UK car fleet. as part of its Future Energy Scenarios planning . Ofgem’s Future insights series (no5) sets out the implications of the transition to electric vehicles.

Although a little dated the graphs shows a couple of interesting features. The projected bands are very wide and getting wider. Note the change from 2015 upper and lower bounds to 2017 upper and lower bounds. Not withstanding the increase range, successive estimates are increasing. Both the National Grid and Ofgem documents were produced before the declaration of climate emergency and the UK commitment to netzero. The four scenarios presented in the National Grid paper all fail to reach netzero by 2050. The most challenging is the 2 degree scenario meeting 80% carbon reduction by 2050.

Carbon Trajectory for Deployment of charger points

To assess the power demand for charges, we need a mean charge event charge. This will depend on the vehicle battery size, the mean state of charge (SOC) at arrival and the desired end point. Battery sizes are increasing as user demand greater range and battery costs fall. Typical battery sizes are :

VehicleBattery Size
Nissan Leaf30 – 40kWh
Mitsibushi`16 kWh
Ford Focus23 kWh
Renualt Zoe41 kWh
BMW i333.2 kWh
Tesla Model S100kWh

For workplace or residential chargers used for commuting on average, vehicles will arrive with higher SOC. For modelling the trajectory below we assume a demand of 10kWh/charging event for BEVs. (This figure also corresponds to an average annual mileage per vehicle of 8500 miles per year and power consumption 300 Wh/mile. This gives an annual demand per vehicle of 2550kWh/year. Assuming charging of 5 days per week for 50 weeks of the year gives a mean charge of 10.2kWh for BEV’s. National Grid in the assessment use 1760kWh/year as an average for the current PHEV/BEV ratio.

Source: Sonas Energy Internal Report, for illustration only

In the diagram above we have present a illustrative growth scenario for number of BEV’s serviced per day to illustrate the trajectory. This is a linear growth scenario from a small number in 2020 to over 150 vehicles/ charging events per day in 2035. ( This might represent say 40% of the fleet and so would be typical of a development with something like 375 car parking spaces.) The top right of the diagram shows that the declining carbon intensity of the grid more than offsets the increase in number of BEV charging demand events.

The net carbon savings can also be calculated based on the assumption that the BEV displaces the fuel consumption of a conventional ICE vehicle.

To calculate the conversion factor we compared the power consumption of a BEV with the fuel consumption of an equivalent ICE vehicle.

Taking the BMW Mini as an example this is available as full BEV or conventional petrol ICE. The BEV has a power consumption as 260Whr/mile and the petrol ICE version 52mpg. For this example, for every kWh of electricity used for charging the BEV we displace 0.735 kgCO2e from an equivalent ICE petrol engine. Applying this factor the trajectory above is drawn showing the trajectory of the net carbon savings per kWh charger. As shown in the lower two graphs in the figure 4 above, for progressive changeover to BEV we achieve significant net carbon savings.