Diesel has more energy density, why is propane so popular?

[Technomad]

Propane contains 7.5kWh/l while Diesel contains 9.7 kWh/l. [1]

That's a %30 difference.  At the same time, propane is a heavy gas, and potentially explosive while diesel is rather stable and gives off non-explosive vapors.

I know the RV industry has a whole bunch of reasons for using propane, primarily for cooking, and once you have a propane tank aboard, you might as well use it for heating.  Thats fine and so most RVs have propane.

I'm designing my systems from scratch and going my own way in terms of what I chose, mainly to fit my lifestyle (which is, btw, to do sous vide and use the microwave to reheat things, and I'm generally trying to avoid putting a propane tank on my rig.)

In fact, I really would prefer to be completely all electric.  I would rather invest in batteries and solar panels (which seem super cheap to me when you get residential units) than in fossil fuels.  Not because I'm an environmentalist (I'm not) just because of the nature of burning things in a custom designed vehicle.

I've used a diesel heater before on a boat-- it was a little furnace, and sipped the gas.  With a forced air blower on it would have been great.  Meanwhile, my experience with a propane furnace in a truck camper is that I would be cold at 3am when the battery ran out.  (Though I was probably on the wrong side of the %50 limits for lead acid in those days-- first night I fully depleted the battery and then after that was charing it with the alternator and may never have gotten it back to %100.)

On the other hand, lets figure out the costs  per unit of heat:

Propane costs about $2.50/gallon (and has ranged between $2-$3 a gallon for the past 7 years), and Diesel is around $2.95.[2]

Or in short, 8.8 cents per kWh or propane and 8 cents per kWh of Diesel.

I'm assuming that in both systems they are equally capable of converting a liter of their fuel into heat at the same efficiency.  Does anyone know the relative efficiency of force air heating with diesel vs propane in BTU/kWh per liter terms?

So propane is only %10 more expensive per kWh and that more than justifies using it if it makes sense for you, while the savings for diesel looked at here are not significant enough to worry about.  (but this also puts someones complaint about "don't pay road tax to heat your space" into perspective- I bet that %50 of the cost of diesel per gallon is taxes of various forms, and that the percentage for propane is a lot closer to %10.)

Which brings us to other factors:
-- Overall system performance.  Is one more effective than the other?  In both cases you can get on demand hot water, hydronics systems and forced air heating.
-- Operational Risk -- eg: in an accident, or results of a leak
-- Quality of the results - Not sure if there can be a difference here, forced air heat should be the same quality since in both cases.

When designing your own system what did you choose and why?   I started this post thinking the economics heavily favored diesel, and that the safety factor did as well.  Turns out I was wrong on the economics.   I still worry about how I will mount a propane tank on my box truck... while I think a small diesel tank in an underbody box would be perfectly safe (and I'd be comfortable with that.)

Thoughts?

[1] http://hypertextbook.com/facts/2006/TatyanaNektalova.shtml
http://hypertextbook.com/facts/2002/EricLeung.shtml


[2] https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=W_EPLLPA_PRS_NUS_DPG&f=W
https://www.eia.gov/petroleum/gasdiesel/

 

[MrAlvinDude]

To my mind, diesel is a "dirty" fuel, meaning: It can hold many contaminates and still function, but the burn process leaves many undesired components.

Gases are usually cleaner, and typically burns cleaner as well, so there will be much fewer undesired components in the air you breathe, when being close to the exhaust.

But this is just my gut feeling.

 

[Weight]

I can't stand the smell of diesel fuel. The exhaust makes me ill. The components are very much more expensive than propane equipment and requires more maintenance.

 

[John61CT]

Carrying and using propane on a boat is **very** inconvenient and difficult to do safely.

In a land vehicle, not so much.

The density issue is a lot more important if you are an offshore liveaboard, but water usually requires vandwellers to visit civilization more frequently than topping up a BBQ bottle.

Or if you do decide to carry an 80-gallon tank, it's not going to endanger your life by upsetting the boat designer's carefully thought out capsize ratios.

All that said, yes, if you can stand the smell, great quality diesel cookstoves, lanterns, space and water heating can certainly be found and installed in a van.
Not my choice though.

 

[tx2sturgis]

I'm assuming that in both systems they are equally capable of converting a liter of their fuel into heat at the same efficiency.  Does anyone know the relative efficiency of force air heating with diesel vs propane in BTU/kWh per liter terms?

So propane is only %10 more expensive per kWh and that more than justifies using it if it makes sense for you, while the savings for diesel looked at here are not significant enough to worry about.  (but this also puts someones complaint about "don't pay road tax to heat your space" into perspective- I bet that %50 of the cost of diesel per gallon is taxes of various forms, and that the percentage for propane is a lot closer to %10.)

I don't know the exact numbers but I think typical propane furnaces (in RVs) are in the neighborhood of about 50-70% efficient. 
A lot of the heat is blown right out the exhaust port. But for a typical diesel bunk heater the efficiency is higher, I think around 90%. The waste heat is just a small trickle coming out the exhaust port, and yet the heated space is nice and toasty. 

And I'm that 'someone' who gets on the diesel road tax soapbox often, it's the same thing with using gasoline in a generator, or a dual fuel lantern, or a lawnmower for that matter, but most of us only use a few gallons a year (or less) in those.

Heating with diesel for many seasons in a vehicle would use a lot more road taxed fuel. 

It's around 40c to 50c per gallon for diesel, depending on what state you buy from. BTW, when a tractor trailer driver fills up a reefer trailer fuel tank (which is diesel) the road tax is not applied to 'reefer fuel'....again, burning diesel for other than running the main engine to go down the road.

My intention is to inform you guys, and my intention is NOT to dissuade you, I just want you to be aware. We pay enough damn taxes as it is.

 

[wagoneer]

What makes sense to me is the diesel tank in my truck is about 30 gallons I fill it about every 500 miles or so. I would love to use diesel as a heating fuel
does anyone have somewhat clear idea of how to and which one to look into buying? My propane heater is a hog and I never use it.

 

[tx2sturgis]

I would love to use diesel as a heating fuel

{snip}

does anyone have somewhat clear idea of how to and which one to look into buying? 

They are often called 'bunk heater' or 'parking heater'.

They are expensive. And the installation is complicated. They burn between a half a gallon to a gallon of fuel per night (on really cold nights) and you can double that for 24 hour (cold weather) use. They also require DC from your batteries for the electronics, the blower, and the dosing pump. 

But they are safe, they work well, and they have automatic temperature setting, set and forget. You can upgrade some of them to a timed controller, but most RV's would not need that feature. 

Google these for more info:

Airtronic, Webasto, Espar.

 

[user 15857]

What makes sense to me is the diesel tank in my truck is about 30 gallons I fill it about every 500 miles or so. I would love to use diesel as a heating fuel
does anyone have somewhat clear idea of how to and which one to look into buying? My propane heater is a hog and I never use it.

Several years ago I looked at buying a van with a diesel engine and researched diesel heaters, stoves, etc. for the living compartment.  To me the decision is simply one of having only one fuel on board, ie: the K.I.S.S. attitude.  I don't have the links to resources but there were quite a few people who did outfit their living area with diesel components and it wasn't all that difficult IIRC.

 

[wagoneer]

I have been looking at recirculating hot water systems using a radiator with small fan for heat and perhaps showering etc. but the water consumption would be prohibitive
plus my horizontal propane tank is about 15 years out of date and have been refused refiling .

 

[Surly Biker]

What makes sense to me is the diesel tank in my truck is about 30 gallons I fill it about every 500 miles or so. I would love to use diesel as a heating fuel
does anyone have somewhat clear idea of how to and which one to look into buying? My propane heater is a hog and I never use it.

Many MB Sprinter van builds use diesel "bunk heaters" e.g. Espar D2. Tap into the fuel tank and combustion exhaust vented outside.
I installed one in my build and they are great.

 

[grummy]

Many MB Sprinter van builds use diesel "bunk heaters" e.g. Espar D2. Tap into the fuel tank and combustion exhaust vented outside.
I installed one in my build and they are great.

I'm with you. I love my old Espar D1, and will not hesitate to pull the trigger on a new one when the time comes. I see them out there lately for about $850. Super efficient, will burn ALL the fuel from a tank rather than often returning gas in the tank just because you are low... They will burn diesel or Kero. No smell, no fuss, no muss. Extremely easy to fit an adequate tank on even a gas truck. The only thing I will do perhaps before buying another is research the details of the gas equivalent just for fuel convenience.

If I NEVER have to stand waiting for a cashier to open up the 20lb tank exchange bin, if I NEVER have to stand out in the cold waiting for some shmuck to fill a 20-30lb'r or crawl under my truck to fill a horizontal tank, I'm down with that. Nothing to me is worse than having to buy bulk propane. After running out mid grilling session too many times combined with the hassle, along with some of the poorest lasting guts, I swore off "Gas Grilles" years ago as well.

My cooking is done sometimes with 1lb propane bottles, but, I also will use Butane, buying either in bulk when on sale. Simple, easy. If I am out of either, I have a microwave and when really in a bind... a Stainless Kelly Kettle that I should really use more often.

 

[ZacLee]

Propane has unlimited shelf life without need for chemical preservatives while diesel will only last a few years even with preservatives. Diesel has much longer shelf life than gasoline though.

 

[debit.servus]

I think about all the uses of the fuel. Is there a diesel stovetop? Is there a diesel water heater? Can I plumb fuel lines to these appliances? I like kerosene, however finding kerosene for a reasonable price (below $5 a gallon) is harder than finding someone to fill a horizontal underbelly RV propane tank (at least in the SF Bay Area). That leaves gasoline, available everywhere, but are there gas versions for all the appliances.

That is what I think about when designing a rig with non-propane appliances.

 

[deadwood]

If I had a diesel engine I think I would have gone with the espar as my heater. But I have a gas engine so I opted to put a propane tank mounted under the van. It's 7.8 gallons so lasts quite a long time. I use it for cooking and for my propane heater (Dickinson fireplace). I'm not usually in a very cold climate so for cooking the tank will go all summer. In the winter the fireplace is only run for a while to take the chill out of the air.

If I ever make it to a cold climate I'm sure it would run a lot more. Even if I had to fill it once a week during a cold winter that would be no big deal.

 

[John61CT]

Every type of heating appliance is available fueled by diesel/kerosene.

And Espar etc also make gasoline fueled versions of their heaters

 

[Technomad]

I don't know the exact numbers but I think typical propane furnaces (in RVs) are in the neighborhood of about 50-70% efficient. ... A lot of the heat is blown right out the exhaust port. But for a typical diesel bunk heater the efficiency is higher, I think around 90%. ... Heating with diesel for many seasons in a vehicle would use a lot more road taxed fuel. ... It's around 40c to 50c per gallon for diesel, depending on what state you buy from. ... We pay enough damn taxes as it is.

I mentioned the road tax issue because I think it is highly relevant and had never thought of it until I saw one of your posts.  I disagree about the level of taxation, I think its' closer to $1.50 on a $3.00 gallon of diesel, because there's a lot of taxes at the federal level that should be included as well as overall costs and hidden taxes (diesel is so highly regulated, that's a kind of tax to my mind.) 

In fact, if the taxes were only about 40 cents, that's about %13, meaning the difference in efficiency between propane and diesel is more than enough to cover that tax and still be %20 cheaper. (since Propane is about %10 more expensive per watt.) 

But moving on, is it possible to avoid this tax by buying heating oil?  (EG I understand homes in the northeast are heated in this manner)  Or an alternative approach, is pure biodiesel taxed at the same level?  Since our government wants to be environmental most of the time, did they boost the biodiesel industry by cutting its taxes?

Worst case scenario we can all get together and buy a box car of canola oil and brew our own biodiesel.  (kidding!)

I have been looking at recirculating hot water systems using a radiator with small fan for heat and perhaps showering etc. but the water consumption would be prohibitive
plus my horizontal propane tank is about 15 years out of date and  have been refused refiling .

I'm not sure why you would say the water consumption would be prohibitive-- recirculation means the water (better to use coolant) that goes out from the heater comes right back in.  Below I'll describe the setup I'm contemplating, might make it clearer.

I'm with you. I love my old Espar D1, and will not hesitate to pull the trigger on a new one when the time comes. I see them out there lately for about $850. 

Where do you see Espars for sale?  I would really like to be able to buy these things, but never find them in my stomping grounds (which is basically amazon, alas, they give me 12 months %0 so it's hard not to buy everything there.)

 

[Technomad]

Here's the setup I'm contemplating, or would build if I had to pull the trigger right now:

Get the Hydronic M2 12 (or whichever one I can afford) as described here:
https://www.eberspaecher-na.com/fil...a/pdf/EB_Hydronic_M-II_WEB_READY_01_26_15.pdf

First thing to note is that I'm building box van, the box will be aluminum, and inside the box ,I am building a frame the same dimensions as the box out of 80/20.  80/20 is extruded aluminum.  check it out here: http://8020.net

Here's a picture to give you an idea:
 

Now the reasons for this kind of shape is its easy to bolt to and to adjust down the line.  But those slots would be perfect for running the coolant hose thru in a hydronic system (hell if I wanted to get fancy, I could run the coolant directly thru the center hole, they have support for pressurizing these, but I doubt I'll do that as it is likely unnecessary. 

The coolant will transfer heat to the aluminum the aluminum is an excellent conductor of heat, and the air will be heated.   But I expect that might not be enough, so I will also attach aluminum heat sinks on top to more quickly radiate heat out of the hose.   It may turn out that the hoses, being plastic, are too poor at conducting heat, but it would easy to replace them with aluminum pipes for long sections..... though I would rather a perfect length of hose with one end going into the heater input and the other to its output and no cuts or joins that could fail. 

The main thing that draws power with forced air heating, in my suspicion, is the motor that has to force air thru a radiator. 

Heat sinks are cheap and plentiful, since they are used in the electronics industry, and supremely efficient-- they are extruded aluminum designed to maximize surface area --- literally to exchange heat with the air.   And since I don't need to be space conserving (I'm not putting all of my air heating in a one cubic box like most RVs) I can spread the system out. 

I am going into detail here because this is the result of rethinking things from the beginning (and it doesn't matter if I use propane to heat the coolant, same principle applies.)

We have to use RV and marine equipment out of necessity, but we don't have to do so in the same fashion the RV and boat makers do, as their primary goal is to move a boat to a couple who isn't paying too much attention but wants to checkbox every item on their list.

 

[rm.w/aview]

^ Your post had me think of this system, https://www.truma.com/us/en/home/index.html , which provides hot water along with radiant heat via a pump instead of a heater fan, and probably eliminates the moisture associated with propane heat. A while back I had an oil burner for heating a house, #2 diesel I think, which at that time was the less expensive option providing good clean heat. Once or twice a year, depending on winter's severity, delivery was made which brings the viewpoint made by debit.servus in his post to light.

 

[rm.w/aview]

Also found this video of a build using the 8020 aluminum

 

[Technomad]

By the way, apparently this site is a directory of where you can buy off road diesel and avoid $0.40 of the taxes: https://cfnfleetwide.com


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