In response to “Introducing the first all-electric hybrid vehicle” fleet column (December 2010, page 25):

Do you have an update regarding the performance of Navistar-Modec EV Alliance LLC's eStar truck in the cold weather Chicago has experienced this winter?

— Dennis Fleming, DSM coordinator, JEA, Jacksonville, Fla.

Fleet columnist Paul Abelson responds:

As with all batteries, performance deteriorates with temperature. The colder the temperature, the greater the loss of range. I predict a 20% drop at 32° F and another 20% at 0°. That's the loss that lead-acid batteries experience. I don't know if NiMH batteries experience the same losses, so that's just a guesstimate.

By the way, recharging takes more input energy as temps decrease, and charging takes longer.


In response to “Stimulus success story” (December 2010, page 48):

I was surprised to read that $2,880,000 was spent to save $67,000/year in electricity, and that this is touted as a success.

Also, no data was given about annual maintenance costs for the solar panels and communication equipment.

Neglecting interest, depreciation, and operation costs, payback is more than 40 years out. This is success?

— Tom Werblow, city engineer, North Platte, Neb.

Author George Allan, PE, responds:

I guess the basic question is how one defines success.

We believe this was a success because this project and the dozen similar projects funded have increased the state's goal of more “clean” energy (i.e., solar and wind power). The capital cost of clean energy is high and most communities can't finance the construction without assistance. But in this case, Massachusetts decided to fund 100% of the construction with stimulus funds.

In my opinion, that's a better use of stimulus funds than the many highway repaving projects we've seen.

We expect maintenance of the solar panels to be minimal — normal wear and tear that any electrical component in the system would experience. Also, this project is connected to an existing SCADA. The water district received a 10-year warranty on the inverter and a 25-year warranty on the solar panels. I hope that answers your questions.