Tuesday, May 26, 2009

The Green Lawnmower

I have a new, unexpected hobby: mowing the lawn. For our first few years here in Virginia we opted to have a lawn service cut our grass, so my wife and I could focus on other things, including establishing our respective businesses in a new location. When the economy and stock market tanked, this became an obvious source of savings in our monthly budget, complicated by my determination not to buy a gasoline-powered lawn mower. Since our yard is a little too big for either a corded electric mower or a manual push mower to be practical, I focused on finding a suitable rechargeable mower. My experience so far has left me with decidedly mixed feelings about this relatively new technology. Some of these issues look applicable to plug-in electric cars, as well.

It might seem odd that someone with my industry background would shy away from a gas-powered mower. Among other reasons, small engines produce a disproportionate share of local air pollution, even after the implementation a few years ago of the EPA's Phase I rules for small spark-ignition engines. (Phase II and III are coming along in a few years.) I also gained a healthy respect for this fuel and its properties during my stint in Texaco's Los Angeles refinery (now owned by Tesoro) at the beginning of my career. I am a firm believer that the safest place to store gasoline at home is in your car's fuel tank, particularly in a warm climate. Second-best would be in a lockable shed a safe distance from the house. Lacking one of those and concerned mainly about my young and inquisitive child, I concluded that if I couldn't find a satisfactory rechargeable mower I would grit my teeth and continue to pay the lawn service. Happily, it turned out that several manufacturers now offer rechargeable mowers that aren't just toys.

After reading many reviews I chose the Solaris S21HB, made in Canada by Linamar Consumer Products. It is a beast, weighing about 110 lb. with batteries. Several family members remarked that pushing it around our yard would provide a nice alternative to one of my weekly gym workouts. I suspected that would be true even before I acquired my current familiarity with the actual grade of much of our lot. The main reason this machine is so heavy is directly relevant to a periodic topic on this blog: our old friend energy density. The Solaris's two 24V lead-acid batteries contribute about 30 lb. (The only Lithium-ion battery mower I could find, made by Bosch, is not yet sold in the US.) Their combined 40 Amp-hours of storage equate to the energy content of less than 4 ounces of gasoline. Even if it uses its stored energy 3-4 times more efficiently than a gasoline engine, the mower's range is still substantially less than from the typical 1-quart fuel capacity of a gas mower. As a result, I must adapt my lawn mowing to the limitations of my new, green device. Since I can't cut all the grass in one session, I have to split it into two tasks at least 8 hours apart, to allow enough time to recharge the batteries. My alternative is to invest $100 in a second set of batteries, which are currently out of stock.

As much as I enjoy the relatively quiet and odor-free operation of the battery mower, I sometimes find myself envying my neighbor's gas mower and wondering if I made the right choice. While mowing the lawn recently it occurred to me that this situation appears similar to that of owning a plug-in electric car without an onboard backup engine. Battery technology is still not up to providing a driving range comparable to a car powered by liquid fuels at an acceptable cost or weight premium. Buyers of such cars face a choice between adapting their lifestyles to match these limitations or relying on future services such as the on-the-fly battery swapping model envisioned by Better Place. As a consumer, I doubt I'm up for either one. Barring the overnight commercialization of the latest fast-charging battery technology--which would still require truly enormous currents and voltages to deliver as much effective energy in a comparable interval as filling 10 gallons of gasoline--I'll lay odds that my next car will be either a diesel or a conventional hybrid. At this point, like it or not, petroleum remains the best energy carrier we have.

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