jamius.com

folypers wrote:Yeah I know, but 80 gallons shouldn't weigh to much? I'm not talking tons of it.

Close to 700lbs.

If the water was heated to 90degC from 20degC the amount of energy stored would be:

E = (4.2KJ/kgdegC)(90 - 20degC) (300L)(1.000kg/L)

= 88200 kJ = 24.5 KWH


Not much energy storage.... I would go with propane.

30lbs propane cylinder = 649,980 BTU capacity = 190KWH

Almost 8 times the energy in 20 times less mass.

A propane system would not be autonomous enough, there would be too much refueling involved. Refueling stations are relatively common in the US, but they're sparsely spreaded in Europe and everybody uses different adapters and tank sizes.. Your calculations are good and indeed show that water can't store energy as dense as propane, but you only used fuel weight as an argument in system considerment. I'm worried about having an engine and putting a generator under my house, let alone a propane tank. I just don't like the idea of using propane, and I don't like propane itself, maybe because I've seen two people get seriously injured and other ones get hit by "schrapnel" when a propane tank exploded at the campground when I was a kid. Yes, I also use emotional parameters that's why I want a bus conversion instead of a truck conversion (which is easier). A truck as a house is lame, in my subjective point of view. And that's about the only reason I'm against it. But to get back to propane, I'd hate working with the system so I'd probably hire somebody or something, which I don't want to do. The BTU capacity of propane also decreases with outside temperatures, but I'm not sure if I remember right. Diesel burns cleaner in any temperature and more reliable at low temperatures (again, I'm not completely sure).Diesel does have a higher relative BTU than propane. The latitude of my country is comparable to the New York region, so it's something really essential. I could use electric/heat pumps and solar heating when conditions allow. And I'm researching if tubes on the belly of the bus could be used for cooling. There's always need for cooling when a hydronic system is in operation. So if you do the thinking, I'm covered in a lot of climates. A propane system also can't pre-heat the engine (better for the engine and more fuel efficient) and it's harder to use excess heat from the engine for warming. Isn't it also easier to use thermostats with a hydronic system? Because I really want a thermostat in the storage bay, to prevent freezing. But as I said: you're definitely right, dense energy is a true attribute for an autonomous vehicule. And thanks for the energy storage formula, I've seen it in school but lost track of them! Just need my constants and I'm rolling


edit: i found specs of a hydronic system for mobile application

The Oasis system provides 50,000 BTU/h of diesel powered heat, supplemented by two 120VAC electric elements that provide another 10,500 BTU/h,

I recently saw something that said propane could get too cold to burn. I am not sure where, but it surprised me.

Possibly enthalpy related? It could be that there's not enough 'starting energy' to start the combustion.