Thursday, July 24, 2008

Yeah? So What!

Ok. The arctic may have oil.

Well compare that to oil reserves in the Green River Formation in the Western United States.

Then get back to me.

Thursday, July 17, 2008

Global Warming is not a settled science

We don't have to accept any more without a fight, that there is any consensus amongst scientists about Antropogenically caused Global Warming.

From the most recent Editor's Comments of the American Physical Society:

With this issue of Physics & Society, we kick off a debate concerning one of the main conclusions of the International Panel on Climate Change (IPCC), the UN body which, together with Al Gore, recently won the Nobel Prize for its work concerning climate change research. There is a considerable presence within the scientific community of people who do not agree with the IPCC conclusion that anthropogenic CO2 emissions are very probably likely to be primarily responsible for the global warming that has occurred since the Industrial Revolution. Since the correctness or fallacy of that conclusion has immense implications for public policy and for the future of the biosphere, we thought it appropriate to present a debate within the pages of P&S concerning that conclusion. T...
(AMS)

Wednesday, July 16, 2008

Nuclear Waste Vitrification Revisited

I've read a recent popular mechanics article about mini nuclear reactors. From the comments on the article, many people are still terrified about how we process nuclear waste.

Let me first say that I worked for some time with EG & G Rocky Flats, in Rocky Flats, Colorado, on a research project that was directly involved with the development of processes to treat nuclear waste.

While I am not a chemist involved in radioactive chemistry, I developed models to predict chemical and mechanical processing times, in order to assess the overall requirements necessary to treat the many thousands of drums of nuclear contaminated waste that was sitting ABOVE ground.

In my view, the process of vitrification to research the process of "vitrification", which is essentially the process of embedding the radioactive ash into glass. The ash is created by oxidizing the radioactive waste in a slow, but controlled fashion. The resulting ash is mixed with molten glass. The ash incorporates itself into the glass matrix. After it solidifies, the radioactive components are embedded within the crystalline structure. This is much like how lead crystal is safe to drink from, even though it contains lead. The lead does not leach out of the glass. The following research paper from Pacific Northwest National Labs shows that unblanketed nuclear ash-containing glass has a nearly leachless rate for thousands of years.

The vitrified glass is still radioactive, and does heat up, but in a very predetermined way. The heat-up is determined by the relative amounts of ash and glass.

Finally, the vitrified radioactive glass can be "blanketed" That is, encapsulated by non-radioactive glass. This would reduce the leach rate by many orders of magnitude... That is to TENS to HUNDREDS of thousands of years.

Add to the fact that the vitrified waste can be stored in an underground salt dome, and basically there is no problem for humanity.

Tuesday, July 8, 2008

Driving Distance Per Dollar: A comparison of electric vs. gasoline engine cars

I've been interested in determining an appropriate comparison of the cost of driving an electric car compared to an ordinary gasoline-powered (or non-plug in hybrid) car. Since I was unable to easily find this comparison published, I've done it myself here.

What am I calculating in each case? The cost per distance of an electric car and the same quantity for a gasoline powered car. The ratio of the two tells us how much farther we can go, per dollar, with an electric car.

Assumptions

Both vehicles are traveling at the same speed, and require the same brake power. The brake power is the power delivered to the wheels.

Variables

P = Power required at wheels of vehicle to drive at speed V (hp or Watts)
V = Vehicle speed (mile/hr or m/s)
ηe = Overall efficiency of electric engine
ηg = Overall efficiency of gasoline engine
Ce = Cost of electric energy ($/kW-hr or $/J)
Cg = Cost of gasoline ($/gal or $/liter)
ρ = Density of gasoline (kg/liter)
Δh = Specific energy of combustion of gasoline (J/kg)
DDe = Distance per Dollar of electric car (miles/$ or km/$)
DDg = Distance per Dollar of gasoline car (miles/$ or km/$)
Ee = Fuel economy of electric car (miles/gal or km/liter)
Eg = Fuel economy of electric car (miles/gal or km/liter)
Qg = Volumetric flow rate of gasoline (gal/hr or liter/hr)

Analysis

Step 1. Analysis of the Gasoline Car.

The Distance per dollar, DDg is the ratio of the fuel economy to the cost of the gasoline fuel consumed by the engine, DDg = Eg/Cg. The fuel economy is the ratio of the vehicle speed to the volumetric flow rate of fuel consumed, Eg = V / Qg.

The thermal power released by the combustion of gasoline is ρΔHQg. (We multiply by flow rate by the density because the thermal energy is usually listed on a mass-basis, but the flow rate of fuel is a volume-basis.) Due to thermodynamic inefficiencies inherent in the combustion process (and transmission losses), the amount of mechanical power delivered to the wheels is less than this. The ratio of the power at the wheels to the thermal power by combustion is the overall gasoline engine efficiency, ηg. The mechanical power delivered to the wheels, P = ρΔhQgηg. Rearranging this equation, we have Qg = P / (ρΔhηg).

Substituting this expression into the first equation in this section, we have DDg = ρV&etagΔh / (PCg).

Step 2. Analysis of the Electric Car

The distance per dollar for the electric car is given as the ratio of the "fuel" economy to the price of electricity needed to charge the batteries, DDe = Ee / Ce.

The electric car economy is the ratio of the speed of the vehicle to the rate of electrical power supplied by the batteries. The ratio of the power at the wheels to the electrical power supplied by the batteries is the overall efficiency ηe. Thus, Ee = Vηe / P, where P is the power at the wheels. Thus, DDe = Vηe / (PCe).

Step 3. Compute Ratio

The ratio of the electric vehicle distance per dollar to the gasoline vehicle distance per dollar is given by dividing the two equations at the end of each previous section. Note that the P and V cancel out since they represent the power at the wheels and the vehicle speed. We assumed these things were the same for both cars. Thus,

DDe/DDg = ηeCg / (ηgρΔhcCe)

Sample Calculation

For an electric car, the overall efficiency is 75%. For the gasoline car, the efficiency is about 20%. The cost of gasoline is $4.25/gallon. The cost of electrical energy is about $0.106/kW-hr (according to my ComEd bill). Finally, the density of gasoline is about 740 kg/m3 and the specific combustion energy (actually enthalpy is the correct term here) is about 47,000,000 J/kg.

Inserting these terms into the our equation for the DD ratio yields.

DDe/DDg = (0.75/0.2) x (2.734) x (4.25 / 10.6) = 4.1 !!!

The middle term accounts for the density, combustion term, and unit conversion factors.

Conclusion

For a typical electric car, the distance driven per dollar is 4 times that for a gasoline-powered car. This analysis does not imply that the overall costs of electric vehicles is lower, since a real economic analysis has to include many other factors, not the least of which is initial cost.