Eco-friendly small cars are great, but hybrid cars are better and soon we will be able to buy plug-in hybrid electric vehicles like the Chevrolet Volt, or completely electric cars like the Mini-E. You can also get your hybrid car converted to a plug-in hybrid now, with the addition of more battery capacity.
These plug-in hybrid vehicles can drive many kilometers in electric mode only before switching to their internal gas powered engines. Overnight, or whenever the cars are parked near an electrical power outlet, the batteries can be recharged, minimizing the gas when driving.
For example, Hymotion offer a plug-in conversion kit for the Toyota Prius that gives the option of driving 24kms (15miles) in electric mode if your speed is less than 64kph (40mph), or you can get the equivalent of 42km/litre (100mpg) for 48kms (30miles) and then the usual 19.5km/litre (46mpg) average for the rest of your driving. These plug-in hybrid cars and electric vehicles available today and all the future electric vehicles, will need to get their electrical charge from somewhere. The big question is exactly where will the electrical energy come from and how clean will it be.
Everyone’s electricity provider has a different carbon emission value, dependent upon whether the electrical power is generated using coal, gas, oil, nuclear or from renewable sources such as hydro, wind or solar. In the US, in 2005, the carbon dioxide emissions ranged from 0.320kg (0.7lb) per kWh to 0.890kg (1.96lb) per kWh across the continent. The higher the number of coal plants, the higher the emissions. Access to hydro sources power lowers the emissions a lot.
Let’s see what this means for a driver who converts his or her Prius to a plug-in hybrid. If the driver had a regular gas powered car, travelling about 20,000kms (12,500miles) a year in a 50:50 highway/urban drive cycle and with a 30mpg average consumption, the carbon dioxide emissions are around 3.7tons a year. A regular hybrid Prius emits approximately 2.37tons for the same drive profile.
The converted plug-in hybrid Prius would emit 1.93tons for the cleanest US electrical provider, with 1.36tons from burning gas in the Prius engine and 0.57tons from the electricity used to re-charge the batteries.
If you happen to get electrical power from a high emissions electrical provider to recharge your Prius, then the emitted carbon dioxide for just the electrical charging is 1.58tons which makes the overall emission 2.93tons…this is worse than just driving the Prius on gas only.
If you are going to spend your hard earned green dollars on turning your hybrid vehicle into a plug-in hybrid, make sure you also have a low emissions electrical energy provider, otherwise you might just end up creating more carbon dioxide than you thought you were saving.
However, if you are really interested in lowering your greenhouse gas emissions from your driving then it is important to decide where you are going to get your electrical energy from….and maybe you should be making it yourself. Check out our article on home renewable generation options.
Trevor Williams is a University of Victoria Mechanical Engineering PhD candidate specialising in renewable energy, power grid modeling and plug-in hybrid electric vehicles. He has a bachelors in Aeronautical Engineering, a Masters in Management Science and over 23 years international experience in the space industry, having worked on Earth observation and telecommunications satellites.
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