EMISSIONS AND SUSTAINABILITY

 

Vehicle emissions are a major contributor of greenhouse gases leading to climate change and local air pollution affecting human health which is why many authorities have, in recent years begun to provide incentives to encourage a switch to electric vehicles or ultra low emission vehicles. Electric vehicles are zero-emission at point of use. However, emissions are produced during manufacturing and during generation of electricity, the amount depending on the method of generation.  The Channel Islands draw most of their electricity through

undersea cables connected to Electricité de France, the main power utility of France which is

predominantly reliant on nuclear and renewable energy.  As a result, using electric vehicles in the

islands creates much lower emissions at point of use than petrol and diesel burning vehicles and

reduces the islands'  reliance on imported foreign oil. However even in the UK with a mix of power

generation, the reduction in overall emissions using an electric vehicleis around 40% and this

will reduce further as more power is produced from renewables.

 

The second major issue which is the impact of engines on local air  quality. The motor vehicle

engine emits many types of pollutants including nitrogen oxides (NOx), volatile organic
compounds (VOCs), carbon monoxide (CO), carbon
dioxide (CO2), particulates, sulphur dioxide
(SO2) and lead. Emissions are related to use of the engine, mainly the fuel type and the temperature of combustion. At low loads, engines are inefficient and therefore the products of incomplete combustion dominate, for example CO and VOCs in petrol engines and carbon monoxide, VOCs and smoke in diesels, the latter being the most serious health issue. In fact, of the two fuels petrol is better suited to the Channel Islands because of  issues with diesel particulate filters. However with either option,  a very short drive is very inefficient use of an internal combustion engine.  

 

Since 2009, the exhaust emissions standards for new cars have effectively required fitment of a DPF in the exhaust of diesel cars, the 'Euro 5' standard came into force and in fact models built before this year would have been fitted with them in anticipation of the new regulations. However they are not well suited to stop start island driving as the filters do not regenerate over slow speeds. Regeneration is a process where the collected soot from the exhaust is burnt off when the engine is hot and this forms a residue of ash. Read the AA's report on DPF's

 

Most VOCs are emitted in the exhaust, although they also escape at other points within the fuelling chain. Evaporative losses can occur during filling, the so-called "fuelling loss". Losses can also occur from the engine when the car is being driven and when the engine is cooling down. VOCs are also released from the fuel tank as the temperature goes up and down during the day; this is called the "breathing loss" and is due to vapour evaporating from the petrol as the fuel gets hot.

 

Combustion vehicles are inefficient as a form of propulsion. Even the most advanced engines have only 40% thermal efficiency and many are only  20% efficient. In other words, only around 20 pence of every £1 from the fuel that goes in your tank actually actually moves the vehicle from A to B. The rest is lost in transmission inefficiencies, heat loss through the exhaust and brake friction.  The equivalent figure is around 70% in a battery electric car since it is more efficient at turning kinetic energy into mechanical energy.    

 

There is added environmental impact from importing hydrocarbon fuels which have to be brought in by tanker, then put into bulk storage and finally distributed to garages around the island using tanker lorries.  This is known as the well to wheel energy inputs. There is an extra layer in the logistics chain for the Channel Islands which make distributing petrol and diesel fuels more energy intensive than the mainland. These added logistics also increase the risk of spillage with consequential risks to the environment.

All these factors combined with very short journey times surely make a good case for vehicle electrification in the islands.

http://www.psehealthyenergy.org/_Full_Fuel_Cycle_Assessment__Well_to_Wheels_Energy_Inputs__Emissions_and_Water_Impacts

 

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