California has been the hub for the implementation of green cars in the USA, but what impact will these new technologies have on electricity demand in the state?
Researchers at the UC Davis Institute of Transportation Studies have found that near-term marginal electricity mix for plug-in electric and fuel cell vehicles and fuels in California will come from natural gas powered plants, including as much as 40 per cent from relatively inefficient steam- and combustion-turbine plants.
The report suggests that the marginal electricity emissions rate will be higher than the average rate from all generation and will likely be more than 60 per cent higher than the value estimated in the Low Carbon Fuel Standard. However, even with the relatively high fuel carbon intensity, the study does conclude that these alternative vehicle and fuel platforms still reduce emissions compared to conventional petrol and hybrid models, thanks to improved vehicle efficiency.
The study will be published in the April 2010 issue of the Journal of Power Sources and saw the authors develop hourly electricity demand profiles for seven vehicle and fuel pathway scenarios. Conventional internal combustion engines and hybrid electric vehicles were compared to plug-in hybrids, battery electric vehicles and fuel cell vehicles while the study also looked at the sensitivities of electricity supply and emissions to hydro-power availability, along with timing of electricity demand including vehicle recharging.
According to one of the authors, Ryan McCarthy, electricity generation must match demand continuously and adding electricity demand from vehicle recharging or hydrogen production will require additional power to be generated. He believes that electricity demand from these vehicles will only have a minor impact on overall demand.
In terms of vehicle emissions, the study found that all of the pathways, except for fuel cell vehicles using hydrogen from electrolysis, reduce greenhouse gas emissions compared to internal combustion engines and hybrid electric vehicles. Fuel cell vehicles using hydrogen from steam methane reforming and battery electric vehicles recharging according to load-level profile, reduce emissions the most – by more than 25 per cent compared to hybrid electric vehicles; while off-peak charging reduces emissions by 21 per cent compared to hybrid electric vehicles.
