#4 Driving A Greener Future

Public Transport

Public Transportation is one of the most fuel efficient ways to travel today. With all the talk of hybrids and fuel efficient cars, trains and bus systems have been providing sustainable transports for decades.  According to David MacKay’s “Sustainable Energy - Without the Hot Air”, cars on average are 33 miles/ gallon witch translate to 80 kWh/ 100passenger-km. He estimates that trains if full to capacity can reach an efficiency of 3 – 4.4 kWh/ 100p-km, buses can reach 6 kWh/ 100p-km. Public transports get there benefit in carrying more passengers for the same energy usage.  Trains are particular a plus because the technology can be directly powered by alternative energy sources.

But although MacKay notes the clear energy efficiency of these forms of public transport, there is a logistical and economic problems dealing with these systems.  Trains are slow to adopt new technology even if the technology is proven just because of the nature of the system. It would take 30 or more years to replace fuel based locomotives and heavy investment infrastructure converting rails so that they operate on electrical energy. This is evident by trains today still using air based braking system despite electric braking systems   being faster, safer, and more efficient. Another issue is he assumes full ridership which is never the case for most public transport system. There will always be times when people will not be using the public busses and trains. When these systems are under capacity, those systems operate inefficiently and sometimes more energy wasteful then cars. These public transport systems, to ultimately achieve their maximum efficiency, require a complete government and more importantly public shift in funding and utilizing public transport.

Private Transport

David Mackay would suggest that the electric car is the most promising personal transport vehicle in providing a solution to the environmental problems.  Electric cars have a lower manufacturing cost, very good energy economy with a 21 kWh/ p-100kh, and have the benefit of being able to be directly powered by renewable resources. Some of the drawbacks are that electric cars have a maximum driving distance of 100 km and the battery life is currently 10 years or less. But changes in electric car infrastructure and improvements in battery technology can potentially lengthen the lifespan and travel distance of electric cars.

The Tesla Roadster