When talking about electric cars, many people people still have the image in mind of a slow golf car or a quiet car for disabled people. This car proves the opposite. The car accelerates from 0-60 mph in less than 4 sconds, has 248 HP, an equivalent fuel usage of 192 mpg and is 100% electric. This is the new Tesla Roadster….

Tesla Motors

The Tesla Roadster is made by the company Tesla Motors

Tesla roadster front-view

The name Tesla is derived from Nikola Tesla an Serb-American inventor,physicist, mechanical engineer and electrical engineer. Tesla’s patents and theoretical work formed the basis of modern alternating current electric power (AC) systems. The same motor also used in the Tesla Roadster.

Tesla roadster back-view

Efficient

As you may know, a good electric motor is much more efficient (95%) compared to a diesel engine (35%) or a petrol engine (25%). The result is that you need less energy for driving an electric car compared to a fossil fuel car. Although the car has more weight due to batteries, this is over compensated by the improved efficiency of the engine and the energy retrieved back during regenerative braking.

The electric engine of the tesla roadster

Torque

Not only are electric engines very efficient, they also have a perfect torque curve. This perfect torque curve causes an electric car to accelerate very fast. An electric motor has a high torque for the full rpm range (0-13.000 rpm).

Motor torque curve. Click on graph for details.

This is the precise opposite of what you experience with a gasoline engine, which has very little torque at a low rpm and only reaches peak torque in a narrow rpm range. This forces you to make frequent gear changes to maintain optimal torque.

Specifications

The specifications of the Tesla roadster are impressive.

Motor	type	3-phase, 4-pole elektromotor
	Max. power	248 PK (185kW)
	Max. rpm	13,000
	Efficiency	90% average, 80% at peak power
	Max. torque	244 Nm

Renewable

The electric car does not produce CO2 or other polluting exhaust when the electricity of the car is generated using renewable energy sources. Fortunately there are more than enough renewable energy sources on earth.

Source: New renewable energy sources, Norway

The annual amount of solar energy on earth is larger than the all the available oil, gas, uranium and coal added together. The annual amount of exploitable energy using solar power or wind power are (both) larger than the world annual energy consumption. Knowing this, it is very strange that we keep burning fossil fuels, polluting our environment and changing our world climate.

If we want to start using these renewable energy sources to build a sustainable future we must invest large scale in renewable energy production. With peak-oil happening (in the near future) and climate change (which is already started) we cannot wait any longer.

Energy usage

The energy usage of the Tesla is 176 Wh / mile. The average US residential retail price for electricity in 2007 was $0.1064 / kWh. The energy consumption cost for the Tesla is 0,176 * $0.1064 = $0.0187 / mile. Lets compare this with a Toyota prius getting 45 mpg–U.S. (5.23 L/100 km / 54 mpg–imp) on the highway according to the U.S. EPA. The price of gasoline cost $3.60 per gallon (updated 4/28/2008) and thus driving a Toyota prius will cost $3.60 / 45 = $0.08 / mile. So the Tesla is 4 times less expensive to drive than a Toyota prius (when comparing the energy / fuel usage). When we calculate the equivalent fuel usage we get the following:

The Tesla Roadster has an equivalent fuel usage of 192 mpg.

Using the Tesla together with your own solar panels make things even more interesting.

Range

The range of a car is determined by the energy usage per mile and the amount of energy available in the car. The Tesla Roadster makes use of lithium-ion batteries. These batteries have a high energy density of 200 Wh / kg. This packs 5 times more energy per kg than the well known lead-acid batteries. The result: the Tesla has to carry “only” 500 kg (~1100 pounds) of batteries for a range of 220 miles.

Re-charge

Plug your Tesla Roadster into its at-home charging unit, and you’ll be fully charged in about 3.5 hours. But this is only needed with a completely dead battery. Even after a 100-mile trip, you can be completely charged in less than two hours (with a Home Changing Station installed operating at 70 amps). And should you need to charge on the road, packed away in the trunk is an optional mobile-charging kit that lets you charge from most standard electrical outlets while away from home.

Charging at home

Regenerative breaking

With regenerative braking, the motor is used as generator which recovers and stores the energy usually lost when you slow down. Up to 30% of the energy can be recovered using regenerative braking. This is especialy true in a city where you need to a lot of breaking (due to the traffic lights).

Video

Sources

• Average Retail Price of Electricity
• Weekly U.S. Retail Gasoline Prices, Regular Grade
• Tesla Motors