Emilis Prelgauskas - interests

Personal Transport

In July 2002 this practice received its first hybrid electric car.

The Prius


The Toyota Prius demonstrator was purchased through CMI-Toyota Adelaide complete with its side and rear advertising decals (in my view the car in its grey paint scheme isn’t distinctive enough to otherwise differentiate from the other traffic) .

The attractions of hybrid electric in this practice’s context include:-

  • while a full electric car would have been preferred, this is at least a commercialised mainstream offering rather than a one-off or special vehicle

  • the vehicle embodies the mix of technology and consumer ‘normality’ to make it barely distinguishable from other road users

  • the technology mix of electric power drive, electronic controls and optimised efficiency internal combustion engine provide opportunities for the driver.

Toyota have a dedicated Prius web site describing the vehicle. Non factory web sites (www.corolland.com) and mail lists (Prius_Technical_Stuff) describe the user reactions.

The vehicle first appeared in Japan Motor Show in 1997, was released in Japan in 1998, in the US in 2000, and in Australia in 2002. In that period the vehicle has been undergoing substantial revisions, with newer models having refined battery, electronics and power. It can now be considered a commercialised product rather than experimental (more than 100,000 delivered worldwide).

For those interested in consumer offerings, the appointments as well as handling are appropriate. The vehicle is very quiet due to electric motor drive, body sound proofing and internal combustion engine muffler.

With a 30kW electric motor + 55kW petrol back up it is not intended as a racer.

For those interested in the technology, the appeal includes:-

  • fuel use potentially of 4.6 l/100km highway and 4.2 l/100km city use to the test standard. The city fuel use reflects the recharge during slowing, and the ‘standby’ mode when stationary in traffic when no energy is used (the internal combustion engine switches off)
  • the electronics provide LCD information in terms of the mix of power delivery from internal combustion engine, the electric engine, the battery bank, and power return during deceleration from the wheels via generator to the battery bank. The other read out provides current fuel use and 5 minute averages fuel use data
  • the electronic interface ‘fly-by-wire’ means driver behaviour can’t ‘thrash’ the vehicle, a desirable feature in fleet vehicles. The electronics protects the battery bank from excessive discharge, the internal combustion engine to operate at consistent rpm and valve settings or be switched off. Start up is by decompressing the cylinders, so there is no ‘cranking’

My personal reactions are to enjoy the fuel economy chase by:-

  • attention to vehicle exterior cleanliness, higher tyre pressure, as well as introducing some body ‘tweaking’ drawn from my sailplane experience to minimise form drag
  • adjusting driving style in line with fuel consumption information to reduce average fuel consumption (4.7 l/100km seems to be a readily achievable average whereas ‘drive without attention’ seems to result in 5.4 l/100km average)

Driving style includes paying attention to the car’s set up.

It will cruise ‘electric only’ during gradual acceleration and speeds less than 63kph.

At start up, the internal combustion engine operates until the catalytic converter reaches operating temperature. Otherwise when the internal combustion engine cuts in, prompt acceleration is effective use of the power on. This engine can be encouraged to switch off by coming right off the throttle once selected speed is reached. The car’s rolling resistance is low.

In this way the aviation concept of ‘on the step‘ can be used.

Accelerate to a speed slightly higher than the intended speed. Back off the throttle until the speed stabilises at a slightly reduced figure. The result is a rolling body with reduced power setting sufficient to maintain the momentum. The result is fuel economy.

Similarly, gradual acceleration toward the bottom of a descent and speed decay on uphill grades assists fuel economy (a lot like flying a sailplane really).

There appear to be optimum electric plus petrol operation speeds for level and ascent grades. Speeds in the low 70’s and mid 80’s (kph) give good fuel economy. Over 100kph fuel penalty rises. Top speed is unstated.

The future is intimated (‘prius’ means ‘to go before’). This vehicle is only one of numerous ‘eco’ streams being investigated by personal vehicle manufacturers. Including fuel cells, high speed flywheels, hydrogen power, solar power, electric power and so on.

From all of these a composite solution will emerge.

I would like to externally recharge my car, because I am in the fortunate position to have a renewable power source. The Prius doesn’t do this because of assumptions about most external power being mains and from fossil fuel generation; that petrol is currently the fuel with a distribution network as well as having good ‘energy density’.

I would like to have more electric battery capacity. The Prius balances the expense and weight of the 300V DC battery bank and its low ‘energy density’ against the weight penalty of 2 motors, body weight savings to achieve a compromise.

With the full electric RAV4 already in use in California, and ‘cockroach’ solar cars, this practice is likely to look to future electric vehicles beyond the Prius.

The economics of the vehicle are a matter of where value is placed.

For this practice the Prius is consistent with the ethic, it is like the practice’s building projects it is a realisation of that ethic, and some cost premium is thus justifiable.

Beyond that there are recurrent operating cost savings which somewhat offset the capital cost.

Compared to a conventional comparable vehicle (8 l/100km), the Prius is expected to purchase 37% less fuel. In a 200,000 km/7 year life this is $6,000 less fuel bill at current price.

Fuel saving driving on current experience offers a further 8% fuel reduction, or $1500 less fuel bill at current price.

The vehicle servicing cost will be interesting to track. Potential exists for lower wear and tear on the brakes (with electric motor regenerative braking instead), and on the internal combustion engine (constant running, electronic interface protection).

The concern is with the unknown, such as - if intermittent and undiagnosable electronic faults occur. This is the subject of discussion on the mail lists. End of section