biodiesel

etyler88,

Both petrol and diesel are (CH2)x hydrocarbon chains. If memory serves me, petrol chains are 5 - 10 carbons in length, and diesel is 10 - 15. So called biodiesel is made from animal and vegetable oils that have carbon chains the same lengths as diesel.

 

Gasoline is very volitile.
At first, it was considered too explosive to use as a fuel.
Many oils, which are not volitile, can be used as a diesel fuel.
Diesel also has the advantage of allowing for higher compression ratios which translate to higher efficiencies.

So, while it's relatively to get oils out of bio products which can be used as diesel fuel, it's not practical to convert those oils to a more volitile fuel.

 

Minnesota has had a state mandate for years, requiring all gas to be part bio. We use E10 (a 10% ethanol blend with 90% dino gas) all year long. And by 2013 that will be increased to E20.

It works great, as proven by my Prius over the past 5.4 years, and the technology for extracting the sugars in the bio mass continues to improve. Heck, even switchgrass (the stuff that naturally grows along highways and in non-farmed fields) has been used to make ethanol. Corn, sugar cane, and sugar beets are other sources too.

So I strongly disagree with it not being practical. It is an excellent way to help reduce the dependence on oil while the electric part of the hybrid continues to evolve... and clean & renewable sources of electricity expand.

 

I think you misunderstood me.
I was not calling BioFuel impractical but rather, converting one BioDiesel to BioGas impractical.

 

There are several reasons why we have bio-diesel and not bio-gasoline. The two most important I can think of off the top of my head are diesel engines have a much simpler control system than gasoline engines and diesel engines are easier to ignite reliably.

Gasoline engines use a closed loop system, and burn at the optimal air / fuel ratio (known as stoichiometry). If the air / fuel ratio is not right, the mixture will not ignite reliably. "Biogasoline" would have to have about the same energy content and "flamability" as gasoline. The spark plug ignites the gasoline mixture and it burns through the cylinder. If the air-fuel ratio is not right, the burn will be slow leading to incomplete combuston and raw fuel going out the exhaust or fast which causes pressure spikes and engine "knock" which can damage the engine.

The gasoline engine controller must "guess" at the right air / fuel ratio to get things started. If it is not correct the engine will never start. Once the engine is warmed up the oxygen sensor will report if the air / fuel ratio is off, but the controller has to know what the energy content of the fuel is to get things started.

In a diesel engine, the air / fuel mixture is "squeezed" causing the temperature and pressure to increase. When it gets to a critical point, the air-fuel mixture spontaneously combusts. Each molecule of fuel joins with nearby oxygen molecules on it's own. There is no flame propogating across the sensor that must be maintained. The advantage is that the air / fuel ratio is not critical. If the driver wants more power, then inject more fuel. If the driver wants less power, then reduce the fuel. As long as you have more air than the fuel needs you get a good fairly clean burn.

As long as bio-diesel fuel is not too thick (viscous) to get through the pump and injectors and is flammable enough to spontaneously ignite you can use it. It doesn't have to be identical to diesel, just in a reasonable range.

Bio-gasoline would have to have a similar viscosity to gasoline so the fuel pump and injectors would not clog, but also have nearly identical energy content and flammability.

Ethanol is the closest we have. It is pretty good, but the engine controller must know how much ethanol is in the fuel, because it has a different energy content, so it needs to inject a lot more fuel to get the same air / fuel ratio. It is ok up to about 10-20%, but more than that and the engine controller will have problems. Flexible Fuel Vehicles have a sensor to detect what percentage of ethanol is present in the fuel and adjusts accordingly.

This is an over simplification, but I believe it is valid. If there are combustion experts out there who can explain it better, please go ahead.

Best regards,
Steve T

 

If the goal is to deliver a vehicle that is at least SULEV clean and at least as efficient with an automatic transmission as a "full" hybrid, diesel doesn't cut it. And adding cleansing equipment to the diesel increases the cost and reduces the MPG, making it less competitive.

Close isn't good enough with you consider 60,000,000 new vehicle purchases worldwide each year.

That's why HSD is so appealing. It makes achieving that clean & efficient goal realistic... as well as laying out a path for the future, which hopefully will exploit electricity more. A non-hybrid diesel simply doesn't. It's a dead-end technology... quite different from the potential "full" hybrids still have to offer.

 

As I understand it Brazil sells bio-gas at the pump next to dino-gas and at the same price. There is also a E85 gas available. From what I've read there is contention that the biomass necessary for production is based on a dino-gas economy (fertilizers and diesel) and so in the end saves no energy. I would really like to know the truth here.

 

When I was in brasil, last march, alcohol (bio-gas) was 1.10 per litre and real gas was 2.65 per litre. No E85 in my area.