The Fuel Cycle of the Future

By Bill Moore

Posted: 04 Jan 2010

This winter I am learning a lot about the real world operation of plug-in hybrids, at least our plug-in hybrid. Here's one of the key lessons so far: the colder it gets here on the Great Plains, the more gasoline our plug-in Prius is burning. Instead of seeing fuel economy readings in the 65-90 mpg range and even higher, we're seeing it plummet to 35-37 mpg. Where we were went an entire month (Oct 30-Nov 1, 2009) before refueling, getting the equivalent of just under 80 mpg, we'll likely now have to refuel every two weeks, maybe three at the very best.

The reason is as plain as the frost-bitten noise on my face. With outside temperatures at well below freezing -- this morning it was -17F (-8C) -- it is necessary to run the engine continually to warm the passenger cabin and keep the windows defrosted. Additionally, the batteries are colder (pack battery temperature over the weekend was 35F (1.6C) ), which means it takes them longer to warm up and begin to propel the car in PHEV mode, typically it seems about 4-5 miles, which is just the distance my wife drives the car to work.

This wasn't entirely unexpected. During the Plug-In 2009 conference in Montreal this past fall, I sat in on a presentation about cold weather operation of similarly converted plug-in hybrids in Canada. They experienced the same phenomenon: PHEVs experience far steeper drops in fuel economy than comparable IC engine-only vehicles, where fuel efficiency also suffers in the winter, but not by the same percentage.

I got to thinking about this over the weekend and wanted to share with you not only what we're learning personally about operating a PHEV conversion in near Arctic conditions, but how I see this reality possibly impacting plug-in hybrid car owners of the future and the fuel industry in general, both electric and liquid.

I just finished reading Gal Luft's "Turning Oil to Salt" and am now about half way through Bob Zubrin's "Energy Victory." Both make the case for alcohol fuels, Luft for ethanol, Zubrin for methanol; fuels that can be made from renewable crops like corn stover, rice and wheat straw, miscanthus, even hemp (should America stop being so damned stupid and myopic about this plant). Zubrin points out that thousands of methanol-fueled cars operated across California in the late 1980s with great success. There are even more E85-capable cars and trucks on America's roads today; Brazil being the model for a true flex-fuel nation. The Chevy Volt will be E85-capable.

Now, I understand the issues with food crop-based ethanol and biodiesel, but progress is being made with cellulosic ethanol and algae-based biodiesel, where for every unit of energy we input, we reap as much as seven in the case of cellulosic ethanol. Algae is even better. While I haven't found any sources online that give a similar ratio of energy-returned-on-energy-invested (EROEI) for algae derived biodiesel, most sources are in agreement that it is 25 times better as a source for biodiesel than palm oil, and 300 times better than soy." Conservatively, an acre-size bond could produce 1,800-2,000 gallons of biodiesel. A comparable acre of soybean will produce only 50 gallons. Some companies place the amount of algae biodiesel per acre significantly higher by a factor of ten, even a hundred on one case, though they are only guessing as the moment. While it does take energy to process the lipids found in the algae into a diesel-substitute, most of the energy to grow the algae is free courtesy of our star, the Sun and the magic of Mother Nature.

The concern that many have rightly expressed about the limits of growing biofuel crops in the higher latitudes where growing seasons are shorter than, say, in Brazil, which can produce three crops of sugar cane a year, becomes less worrisome in a PHEV future. It is only during the coldest winter months, December through February, or November through March, depending on which latitude you live, that higher amounts of fuel are consumed. We are finding that as long as the temperature is above 50 degrees during the daytime, we can expect to see the car run more on it batteries and less on its IC engine, shifting the "fuel" cycle to grid power and less on liquid fuels. What happens in the heat of summer, when air conditioning becomes necessary, we have yet to experience. But the warmer it is, the longer the growing season and more crops that can be harvested, so it would appear to balance out.

Since the frost-free growing season in the higher latitudes also occurs during the time when most PHEVs will be running principally on grid power, this suggests to me a fuel cycle where crops are grown and algae flourishes during the summer, is harvested in the fall and then gradually processed over the winter months into fuel when demand will be at its maximum. As the weather warms, drivers will find their fuel economy again climbing into the 100 mpg+ range, alleviating pressure on biofuel stocks, allowing them to resume the growing-harvesting-processing cycle.

How all this will impact Extended Range Electric Vehicles (EREV) like the Chevy Volt, is yet to be seen. My guess is, based on comments by senior GM program managers and engineers, that the Volt's battery pack will be climate controlled, enabling it to operate more effectively during cold winter weather than my unprotected conversion pack, whose only heat comes from the chemical reaction of recharging overnight and the relatively warmer temperature of our unheated garage. But even here, I would hazard a guess that fuel consumption, on average, is likely to increase somewhat. I am looking forward to finding that out someday.

As for the energy that powers the grid that charges the PHEVs, in a perfect world, much of it in the Spring will come from wind and hydropower from snow pack run-off, while through the summer and into the early fall, solar power will provide the kick needed. Of course, until we get to that perfect world, a good share will still come from coal, natural gas and nuclear. In the case of coal and natural gas, their CO2 output can be captured and fed to nurture the growth of algae or reformed into methanol.

Unlike the current petroleum-dominated cycle where fuel use increases in the summer (as people drive more) and declines in the winter, the fuel cycle of the future will more closely match that of the planet, itself. It won't be perfect, but it will be a important step in the right direction.

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