# News Electric Cars, plug-ins? Why not CNG?

1. Jan 21, 2009

Natural Gas, It's the only logical substitute to Crude Oil. The mechanics of the vehicle are almost identical to gasoline, base infrastructure is already in place (pipelines), Although the major Oil producers also produce Natural gas, the US has reserves that match that of Saudi Arabia and UAE.

21% of all electricity in the US is produced by Natural Gas, 50% by Coal, 1% by petroleum

I don't get what the point is to use electricity created from natural gas to run a car, and not just use natural gas itself.

Just look at the numbers (all data from eia) This is just a rough estimate, world reserves accuracy isn't validated, and prices don't account for the different grades of product

NYMEX->1/21/09

Price
Oil - $40.34/barrel Ngas-$4.6350/mbtu
Diesel-$1.3656/gal Gasoline-$1.1340/gal

World Reserves
Oil- 1,332,000,000,000 barrels
Naturalgas- 61,941,925,400,000 mbtu

Market Cap
Oil-----$53,732,880,000,000 Ngas--$287,100,824,229,000

Total World btu
Oil-----7,725,600,000,000,000,000
Ngas--61,941,925,400,000,000,000

btu/$1 Oil-----143,777 Ngas---215,749 diesel---109,614 gasoline-110,229 2. Jan 21, 2009 ### russ_watters ### Staff: Mentor It is certainly a possibility, but the difficulty with natural gas is the storage. It is tough to get any kind of decent range with a pressurized tank. 3. Jan 21, 2009 ### signerror Perhaps efficiency - gas-fired CCGT power plants can achieve 60% thermodynamic efficiency, twice that of an internal combustion engine. I don't know the figures for gas turbine cars, but from general principle I doubt they're 60%. http://en.wikipedia.org/wiki/Fossil_fuel_power_plant#Gas_turbine_combined-cycle_plants Yes it is! Besides, of course, hydrogen fuel cells, hydrogen internal combustion engines, methanol combustion or direct methanol fuel cells, bioethanol (from miscnathus grass, sugar cane, or blue-green algae), biodiesel (methyl or ethyl esters of lipids), alkali metal hydrides (such as LiAlH4 or NaBH4), chemical electric batteries (Li ion or NiCad), ultracapacitors, synthetic hydrocarbons from biomass (via CO, Fischer-Tropsch), synthetic butanol, dimethyl ether (from methanol), solid boron, or ammonia. But besides those, it's the only logical substitute for oil. Last edited: Jan 21, 2009 4. Jan 21, 2009 ### mgb_phys It's completely standard in europe. You can modify a gasoline engine for about$1000, it still uses gasoline as well (most can't start on LPG).
There were even grants to pay for it and LPG is about 1/2 the price at the pumps because of lower tax
The main reason for not doing it is the worry that once you have paid for the conversion they will put the same tax on LPG as they do on petrol/diesel.

CNG is a bit trickier. LPG gives about half the range of diesel and CNG about half again. It also needs high pressure tanks to store it rather than just a barbecue type propane cyliner

Last edited: Jan 21, 2009
5. Jan 21, 2009

### drankin

I agree, we should work more towards natural gas. As russ said there is a range problem but for the typical daily commuter it is a cleaner/cheaper alternative to gasoline that can easily be used by the general public. More so than electric cars in my opinion. I'm a firm believer that burning a fuel is the most practical way to move a vehicle (and be able to provide enough heating & AC energy).

6. Jan 21, 2009

### mgb_phys

Burning natural gas to make electricity is especially dumb.
The only reason to do it is that it is very cheap to build a gas fired plant compared to any other, you can even build a small 100-200Mw almost off the shelf by bolting together backup generator sized units.
Expensive to run and they only have a short life but if you manage the contracts for power generation wrongly this is what you get.

7. Jan 21, 2009

### signerror

It's not dumb at all! As I pointed out, gas-fired CCGTs achieve the highest thermodynamic efficiencies - 60% even. This is not a cheap off-the-shelf solution, it is a capital-intensive power plant which uses more than one thermodynamic cycle - for example, a high-temperature Brayton cycle (a gas turbine) with a lower temperature Rankine cycle (a steam turbine).

http://en.wikipedia.org/wiki/Fossil_fuel_power_plant#Gas_turbine_combined-cycle_plants

http://en.wikipedia.org/wiki/Combined_cycle

Together with the much lower CO2 intensity of natural gas (half that of coal), CCGT baseload power is a very reasonable short-term reduction strategy for GHGs. For example, a 60% efficiency gas-fired CCGT will emit 1/4th the CO2 per kWh of a 30% efficiency coal plant. It is less capital-intensive and much faster to construct than nuclear power, so it could be a transition strategy.

http://en.wikipedia.org/wiki/File:BiodieselsCountryOfOrigin.jpg

Utilities build (non-CCGT) gas power plants because they are economic for peaking power (fast, on demand load balancing in peak hours). This is because the upfront capital costs are cheap, so amortized, running gas power at very low capacity factor is cheaper than anything else at low capacity factor, except maybe hydroelectric dams. The fuel costs may be high, but at low capacity factor that is less important. See for instance:

http://www.iea.org/Textbase/publications/free_new_Desc.asp?PUBS_ID=1472

8. Jan 21, 2009

### mgb_phys

Thermodynamic efficiency doesn't matter if your fuel is more expensive.

Then using that electricity to electrically heat houses and run stoves instead of piping gas directly to them is about as bright as burning diesel in a power plant to create electricity for plug-in EVs.

9. Jan 21, 2009

### signerror

They are not mutually exclusive. The economy still has non-heating needs for electricity.

It does, because less is needed as a result, which lowers the effective fuel costs. Additionally there is the large CO2 advantage of natural gas - add in a carbon tax and the economics change. For instance, from a 2008 Canadian study:

$/MWh vs.$/MTCO2 (Canadian \$)

http://www.cbo.gov/ftpdocs/91xx/doc9133/Chapter1.4.1.shtml#1088555

http://www.cbo.gov/ftpdocs/91xx/doc9133/toc.htm

Last edited: Jan 21, 2009