In the first of a regular series on new and emerging powertrain technologies, our expert – who has enjoyed a long career in the energy industry – considers electricity’s carbon footprint
Electric buses, either battery-powered or plug-in hybrids, are beginning to appear on the industry’s buying agenda, but it is important to look at the electricity supply situation when considering them.
In the UK, electricity is distributed by National Grid, which maintains and operates the supply network. Electricity suppliers pay a tariff to National Grid for delivering electricity, which is purchased by consumers from them.
There are currently 22 suppliers listed, but 97% of the UK’s electricity is provided by the ‘big six’ such as E.ON, npower and EDF Energy. Three of the six are non-UK owned, and they supply 37% of our electricity.
More importantly, the electricity production mix includes fossil fuel (coal and gas), 50%; nuclear, 20%; renewable, 24%; and imported – from France and the Netherlands – 6%.
In the UK, the average carbon footprint associated with the production of 1kW/h of electricity is 0.523kg of CO2. A typical battery-powered bus has battery storage capacity of 324kW/h. Charging efficiency of 85% is claimed, and thus for such a bus, the energy needed to charge the batteries is 372.6kW/h.
An electric bus’ range is expected to be around 250km, and so the amount of energy used to travel 1km is 1.49kW/h.
Using this value and the average carbon footprint to produce a kW/h of electricity then gives a carbon footprint of 779.3g/ km, which perhaps makes electric not so clean unless provision is made to use renewably-sourced power – and nuclear is not renewable.
There is also the carbon footprint of battery production to consider, but we will leave that for another article.
FIND OUT MORE: Our industry expert speaks with authority and can back up all of his facts, but what do you think? Email editorial@divcom.co.uk if you agree or disagree with him.
