“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

Sunday, January 06, 2013

Atmospheric Vortex Engine

Credit: Atmospheric Vortex Engine
Below is a link to a fascinating and promising concept for generation of electricity called the "Atmospheric Vortex Engine." The FAQs even include a pretty extensive and (on my relatively cursory review) accurate primer on thermodynamics. When I first read of this concept I pooh poohed it but I saw it linked in several sites that I respect and went back for a closer reading. I've come to think that it has significant potential.

I'd divide the possibilities into two "bins." The first is as an auxiliary generator at existing thermal power plants, where the site claims that power output of the plant can be increased by 20% (read the site to see how this would work). In this application, the generator could operate on the same duty cycle as the thermal plant.

The second bin would be a stand alone installation operating between solar heated ground or water (without dedicated collectors) and the much cooler temperatures clear up to the tropopause (!). In this application, I presume that the duty cycle would be less than 24/7 (though it should be much longer than a photovoltaic or concentrating solar thermal plant) and thus would provide less than continuous power and suffer from a reduced but similar intermittency issue as solar or wind generators. For all such installations, grid-scale storage would be a huge advantage.

In any case, this concept is one to keep sight of.

Atmospheric Vortex Engine:

'via Blog this'

The Archdruid Report: Into an Unknown Country

The link below is to John Michael Greer's (the Grand Archdruid of the Ancient Order of Druids in America) first post of 2013. In it, he describes his 2012 predictions and how they played out against the actual events of the year. He then makes predictions for 2013, followed by a "to do" list to prepare for the events that he foresees.

Don't let the Druid slant throw you off. This is a deep, creative, accurate thinker with much of value to add to any discussion of energy, economics, history, and culture. Don't mistake him for a doomer in the James Kunstler (for my take on Kunstler, see here) mode either.

The Archdruid Report: Into an Unknown Country:

'via Blog this'

Saturday, January 05, 2013

Energy - what can be done (Part 2)

In my first post in this series, I discussed possible primary energy savings in the area of commuting to work. In the second post in the series, I want to address what might be saved in terms of personal/passenger transportation other than commuting. Such things include vacations, shopping, miscellaneous non-commuting trips, etc. Such transportation can utilize light vehicles (cars, light trucks, SUVs), airlines, etc. I will include work-related travel other than commuting in this category (e.g., my trips to Houston or Washington D.C. for conferences). Again, I'll be relying on the Transportation Energy Data Book. For light vehicles, I'll use data from Chapter 8, for air travel, it will be Chapter 9.

In the previous post in this series, I had five bullet points for possible methods to reduce energy use in commuting. A similar list would apply here:
  • "Trip combining"
  •  Use of public transportation
  • Utilizing more fuel efficient vehicles
  • Driving more slowly (and other efficient driving techniques)

For household vehicle use, the latest data that can be used for these calculations is 2009. From Table 8.1 we find that ~2.957*10^{12}~ (almost 3 trillion) miles were travelled. From Table 8.9 we determine that 71.3% of these miles, or ~2.108*10^{12}~ (about 2.1 trillion) of those miles were NOT commuting to and from work. I'll need to engage in a bit of interpretation to determine the average fuel economy of the household vehicles travelling these miles. I'm using the Transportation Energy Data Book Quick Facts to infer that the average light vehicle fuel economy is 20.45 (calculated from the weighted average of cars and light trucks). I'm also working on the assumption that the figures represent EPA estimates. So we can estimate that ~2.108*10^{12}/20.45=1.031*10^{11}~ (103.1 billion) gallons that come from ~5.425*10^{9}~ (5.425 billion) barrels of oil.

Trip combining saves fuel in a couple of ways. First, a warm engine uses less fuel than a cold one. Second, multiple out and backs from home can be minimized. So going to the store, then from there to the cleaners, to the nail shop, to the mall, etc. rather than out and back to each saves a significant amount of fuel. It's hard to get a quantitative handle on this since it will be different for each household, each driver, and each day so I'll arbitrarily speculate that this type of trip planning will affect the 33.3% of vehicle miles travelled for "shopping" and "other family/personal business" in Table 8.9 (link is above). Further, I'll speculate that 10% of this fuel consumption can be saved. So the potential fuel and oil savings are ~0.333*0.1*1.031*10^{11}=3.433*10^{9}~ (3.433 billion) gallons from ~1.810*10^{8}~ (181 million) barrels of oil. This is enough oil for a bit under 10 days of consumption in the U.S.

As I mentioned in part 1 of this series, use of public transportation may or may not save fuel and I'll dedicate a post to my thoughts on this at a later time.

The calculations I used in the part 1 for utilizing more fuel efficient vehicles and changing driving methods can be used here as well. First, we'll use an increase from 20.45 to 30 (in this case) m.p.g. (noting that there is a large number of vehicles that do much better than this). This would reduce the 103.1 billion gallons used in non-commuting personal transportation to ~2.108*10^{12}/30=7.027*10^{10}~ (70.27 billion) gallons, a savings of 32.8 billion gallons that come from 1.73 billion barrels of oil. In the U.S., we consume this amount of oil in about 92 days. We are now officially getting someplace!

As to more efficient driving, so as to be conservative, I'll assume these more efficient drivers are driving the more efficient vehicles from the previous paragraph. I'll then assume that we can convince/incentivize/coerce 25% of them to drive in such a way as to exceed the EPA estimates (on which the previous calculations in this post have been based) be 10%, i.e., to achieve 33 m.p.g. (noting that I exceed the EPA estimate by 22% without using the more extreme hypermiling techniques such as pulse and glide, extreme drafting, etc.). In that case, the 70.27 billion gallons would be reduced to ~2.108*10^{12}/33=6.388*10^{10}~ (63.88 billion) gallons, a further savings of 6.39 billion gallons of gasoline that come from 336 million barrels of oil - 18 days worth.

As previously, let's arbitrarily reduce the savings by 25%. We can then estimate that about 1.7 billion (dropping a bunch of significant figures) barrels of oil per year. This represents about 25% of our consumption.

And not burning these 1.7 billion barrels would result in not emitting 605 billion pounds or 303 million tons of carbon dioxide.

Combined with the 9% from commuting, it's reasonably possible, without massive technology boosts, lifestyle changes, etc. to save over a third of the oil we consume just by adjusting the way our households utilize personal vehicles.

Next up: Freight

Tuesday, January 01, 2013

Why hybrids?

In my first post of a planned series on what we can do to reduce our nation's utilization of primary energy, I mentioned what might be done by replacing some of the current light vehicle fleet  with more efficient vehicles. And, as I've mentioned on multiple occasions, my personal vehicle is the hybrid Lexus CT200h. The CT200h has an EPA combined city and highway estimate of 42 m.p.g., comprised of a highway estimate of 40 m.p.g. and a city estimate of 43 m.p.g.

Does the hybrid configuration confer an advantage? A comparison with a high-mileage non-hybrid vehicle will be enlightening. For this, I'll select the Chevy Cruze Eco. This vehicle achieves an EPA combined city and highway estimate of 33 m.p.g., comprised of a highway estimate of 42 m.p.g. and a city estimate of 28 m.p.g.

The first thing to note is that the Cruze's highway estimate is very slightly higher than the CT200h. This is because, on the highway, the CT200h's propulsion is provided by its internal combustion engine, with the electric motor only providing power for hill climbing and passing. And the CT200h is a significantly heavier vehicle, primarily due to the additional equipment required for the hybrid drive train (hybrid battery, auxiliary 12 volt battery, electric motor and generator, and other associated equipment). These Cruze advantages are slightly offset by the fact that in most hybrids (though not the CT200h) utilize a smaller internal combustion engine, which is sufficient due to being able to rely on supplemental torque and power from the electric motor when needed. This smaller engine can operate at a better point in its engine map and will suffer lower pumping losses. The vehicles have very similar drag coefficients and drag areas  and so drag forces are roughly equivalent.

The second thing to note is that the city mileage for the CT200h is significantly higher. This is because city driving often consists of starts and stops, acceleration, etc. The hybrid vehicle  utilizes regenerative braking (more later) to store some of the kinetic energy added in acceleration from stop to speed rather than dissipating all of it as heat. It also utilizes the very efficient electric motor to start from a dead stop. And, of course, plug in hybrids (the CT200h is not such a vehicle) store significant energy that doesn't come from burning gasoline at all. It must be noted that ALL of the energy used in my CT200h comes from burning gasoline, regardless of whether the battery pack is charged by coasting down a hill, the regenerative braking system, etc.

So it's pretty clear that hybrids have the potential to achieve superior fuel economy compared to similar non-hybrid models. The extent to which fuel can be saved by a specific driver will depend on a couple of things - particularly driving habits and the division between city and highway driving.

What are the particular aspects of the hybrid drive train that enable such a vehicle to achieve better fuel economy than an equivalent non-hybrid vehicle? As mentioned above, one of the major items is the hybrid's ability to utilize some of the energy added to the vehicle by the internal combustion engine that the non-hybrid wastes.

First among these is regenerative braking. This is a system wherein part of the braking action effected by pressing the brake pedal is provided by having the wheels turn a generator against the torque of the generator action (think of the exercise bicycle at a gym - as you turn up the resistance, the energy you input through the pedals powers a generator that may power a display, etc.). The generator charges the battery, whose energy can then be used for acceleration, or even as the sole motive force at low speed.

Second is recapture of energy during coasting. As I let off the accelerator to slow down, go down a hill, etc., again, the turning of the wheels is used to run the generator and charge the battery. In the CT200h, both of these actions can be monitored in a display in the dash and in more detail on the monitor that also displays the GPS map, and other information I may select.

Next and again as mentioned above, the non-hybrid must have a sufficiently large engine to provide power for all required driving regimes (plus some to spare). This is much more than is required for constant speed driving. For any internal combustion engine, specific fuel consumption is lowest (i.e., the engine is more efficient) when operating near its maximum torque specification. Thus, the non-hybrid vehicle operates at a relatively inefficient portion of its engine map during a large portion of miles driven.

Further, the larger engine has significantly larger pumping losses as low pressure in the cylinders during the intake stroke draws in the air/fuel mixture, and while pumping the burned air/fuel mixture out of the cylinder and into the exhaust system.

The internal combustion engine in the hybrid can typically be sized significantly smaller than the engine in a non-hybrid vehicle (though such is not the case in the CT200h vs. Cruze Eco comparison - the CT200h utilizes a 1.8 liter engine as compared to the base model Cruze Eco's 1.4 liter engine). This is because, in those regimes where high power is required (acceleration from a stop, hill climbing, passing, acceleration onto freeway, etc.) the internal combustion engine can be supplemented by the electric motor.

There are other "nickel and dime" enhancers of fuel economy. For example, when I stop at a light (and assuming the hybrid battery pack is sufficiently charged) the internal combustion engine turns off. This also occurs gliding down a hill, gliding to stop, etc.) and, of course, the stopped engine doesn't burn any fuel.

In summary, the main fuel savers are recovery rather than dissipation of kinetic energy, lower engine size, and operation at more efficient points on the internal combustion engine's map.