Energy Efficiency

Energy efficiency is another “hot” topic. And like many topics in technology, its very prone to misunderstanding and misrepresentation.

For example, a recent prominent engineering magazine published a cover article on the subject of electric cars, one of my favorite topics. And the cover had a really cool graphic comparing the energy density of lead acid batteries to the newer lithium ion batteries which have 4 time better storage capability, and then comparing that to gasoline’s energy density which is eighty three times more power per pound than lead acid technology.

Those are great facts to be conscious of in the race to produce better transportation technology. But it is entirely misleading. The energy density metric is, by itself, wildly out of proportion when you consider that 60% or more of the stored energy of gasoline is lost in the conversion process as waste heat in a combustion engine. In addition, mechanical losses throughout the drivetrain result in additional losses of about 15 to 20 percent.

The point of the electric car, or steam car, or hydraulic car or whatever technology you want to look at, is efficiency. This is because the net efficiency will impact how much storage mass and volume are required for a given vehicle range and drive cycle. Because gasoline is extremely dense as an energy storage medium, you can get by with inefficient usage. Just like when electricity was much cheaper, we paid less attention to what it cost to heat and cool our homes.

Its also cost per transportation mile. If the government is allowing 50.5 cents per mile as an estimated operating cost for a standard combustion engine car, then an electric car that costs 5 cents a mile to operate sounds like a pretty good deal. And if it can’t go 400 miles on a charge, then its good for in town driving.

The key enabling technology for electric cars, hybrids or not, is power storage or batteries in one form or another. General Motors’ EV-1 was doomed from the beginning because they tried to make the vehicle work using lead-acid batteries. The efficiency of the electric motor and the control technology to make it work in this application are well demonstrated.

The interesting parallel here is looking at industrial mechatronics from the standpoint of efficiency of certain components. If I have an application with a gearbox, under normal conditions I might use an inexpensive worm and spur drive. But when I consider the efficiency gain, a planetary solution might allow me to use a smaller motor for the same load, or lower the operating cost of the equipment over a year’s time.

For the electric car, as well as the industrial gearbox, there are a lot of great solutions out there that people are working on. We need to make sure that we are considering them in their proper context so that we make the right decisions on what works best for us as individuals. I think in the long run, it will make things better for everyone.