Although we are mostly about energy efficient building techniques and solar power, most people’s second largest energy usage after their house is their vehicle or vehicles, so it is worth discussing.
Highly efficient cars come in several flavors: hybrids, plug-in hybrids, and pure battery-powered electrics are the most common. Others, such as hydrogen-powered and fuel cell powered electrics are interesting, but won’t be covered here.
Conventional hybrids are equipped with an internal combustion gas engine and an electric motor, both coupled to the wheels through a transmission. It achieves its efficiency by:
- Using the high torque of the electric motor to assist the gas engine during acceleration, thus allowing a smaller, more-efficient engine than would otherwise be required.
- Using the electric motor as a generator to charge the battery during deceleration or braking and simultaneously reduce wear on the brakes.
The original Honda Insight was one of the pioneering hybrids, but the Toyota Prius has been the market leader for years. Today there are numerous makes and models of hybrids.
The advantages of a conventional hybrid over other efficient choices are:
- Use of a single fuel,
- Much better mileage than an equivalent gas powered car,
- An excellent driving range, and
- Lack of “range anxiety” due to the proliferation of gas stations.
The disadvantages are that the gas engine is operating most of the time, burning fossil fuels, and consequently spewing greenhouse gases.
Plug-in hybrids differ from standard hybrids in three respects:
- They have larger batteries,
- The battery can be charged with an external charger, and
- They drive in pure electric mode until the battery is mostly depleted, after which they revert to standard hybrid mode.
They have two principal advantages over conventional hybrids:
- When the battery has been externally charged, the first part of each trip does not directly emit any greenhouse gases, and
- The per-mile cost while in electric mode is less than the cost in hybrid mode.
Whether the higher initial cost is a good tradeoff for you depends on your driving patterns.
The electric mileage champion in this category was the Chevrolet Volt (now unfortunately discontinued), with a nominal electric-only range of 53 miles, while models from other companies tend to be less than half of that. We find that our Volt vary rarely switches to hybrid mode, and so we enjoy earth-friendly electric driving nearly all the time, while the presence of the gas engine eliminates the range anxiety of pure electrics. Our home solar electric system generates all the energy required.
As with conventional hybrids, plug-in hybrids use regenerative braking – after three years of driving our brake shoes are hardly worn at all. We take it in for a minimal service once a year.
A pure electric car’s drive system consists of one or more battery-powered electric motors directly coupled to the drive shaft (or the wheels) — no engine and no transmission. Although the computerized control system is complex, the drive system requires very little by way of routine maintenance.
Electric cars are available in a wide variety of driving ranges, from 50 (or less) to at least 400 miles. Needless to say, electrics with a long driving range command premium prices. For many years, the Nissan Leaf has owned the low-range end of this market, while Tesla has owned the top.
On a per-mile fuel cost basis, electrics are much less expensive to drive than conventional cars or hybrids. The fuel is “greener,” but how much depends on how the power you get from your electric utility is generated (unless, of course, you generate your own).
Overnight recharging at home is simple, of course, but the chicken-and-egg problem of electrics is that charging stations are sparse, compared with gas stations. This leads to range anxiety because a dead battery probably means a tow to the nearest charging station. As pure electrics become common, that problem will decrease.
A second issue is that it takes longer to recharge an electric than a gas-powered car. Over the years, charging times have come down to about 15 minutes in some stations, but others may be several times that.
Pure electric cars and trucks are certainly the wave of the future, but the evolution is still occurring.