If I missed it, please let me know where...

 

If not, does anyone have a conversion of Endurance to Joule (J) or have suggestions to design one that does a reasonable job of making energy expenditures consistent?

 

i.e. size solar from panels to charge a space station vs an exotic material battery 

 

That's a bit too much detail for the Hero System. But as a ballpark figure -- a really big ballpark -- I believe I've seen the figure 50 Joules of energy makes 1 Damage Class of Killing Damage, and double the energy requirement for every +1 DC. So 2d6 Killing Damage is 6 DC, five doublings is 32, 32 times 50 Joules is 1600 J.

Normally I would disagree with you about it being "too much detail" for the system.  If that level of detail is what a particular table enjoys, they should be able to go for it!

Unfortunately, in this case, it IS too much detail for the system to support.  Especially when it comes to things like vehicles and the size/mass needed for vehicular components, the system totally breaks down. :-(

The amount of work performed for a given amount of input energy is dependent on many factors, including the efficiency of the mechanism doing the work. A robot is going to achieve a different result than a human or a pack animal. A low-efficiency engine will do a lot less work than a high-efficiency engine. There is no single conversion metric that would work realistically for all applications and contexts.

Years ago our forum colleague "Bartman" posted his table converting Hero System Damage Classes to joules, foot-pounds, and amounts of TNT, along with examples of famous explosions for comparison, and a summary of his methodology. I saved that post as a Document file and have attached it below for anyone who might find it a useful reference.

DC Conversion (Bartman).doc

What LL has put up is probably the closest anyone has ever tried.

 

The problem is that in HERO, the basic unit of energy is the Endurance Pip.

 

The problem with converting directly to a specified unit of energy is this:

 

Mini Man, who shrinks down the size and mass of a vintage Star Wars action figure by Kenner.  When he does so, he gains several powers, including thirty inches of Flight.

 

Gargantu-Juan the Human Tank activates his power and grows to a height of twelve feet as his body turns to solid steel.  He also has thirty inches of Flight.

 

Professor Technical has built a diesel-powered rocket capable of attaining low-earth orbit.  This mighty manned missile majestically moves it's entire thousand-ton mass with thirty inches of Flight.

 

No matter which character you are using, barring other modifiers to the power, they all use the same amount of END to power their thirty inches of Flight.

 

 

Now that is _not_ to say that you can't work something up such that one END is equal to X joules, and enforce that by requiring larger characters to spend more END to do the same thing as a less massive character, etc.  If that is what you want to do, then by all means, go for it.  I heartily endorse do,kering with the rules, after all.

 

I am simply saying that there is nothing in the exiating system that lends itself easily to what you are doing.  Honestly, even the END rules are wonky, when you realize that the energy used to power a human being for one day wont keep a lightbulb burning for more than a moment or two.

 

 

Duke's identified the issue of playability vs logic and realism, i.e. making a system that's balanced and consistent across a wide range of SFX that should, logically and realistically, alter the system's parameters. In most heroic-level Hero games that don't feature magic, those inconsistencies are generally minor, or easy to rationalize, e.g. vehicle END is a different scale from character END because the two almost never affect each other.

 

For genres like high-fantasy magic or supers, we're already breaking the laws of physics, so sweating those details is rather counter-intuitive.

Short Answer:

My group did this many, many years ago. (Some time in the late 1980s) We came up with 5 points is 200 Joules.

 

Caveats:
I’m just relying on memory here. Since I’m pretty sure all our calculations disappeared over two decades ago.
We did not use the Strength, Lifting or Throwing tables. They are geometric progressions. 
We decided to work with Strengths of 5 to 25. 
We got pretty good agreement with stabbing, gunfire, fire, electricity, and flight.

We had no way to calculate Mental Powers.

Long Term Effects:

Eventually we dropped using Hero points for spaceships and just used the 200J as a standard.

We ended up using two systems. Hero System for people and aliens and personal weapons. 200J for ships. 
The two very rarely crossed paths.
I think one time we had a boarding party cutting through a ship’s hull. At which point the GM said, “Your ship’s engineer calibrated the explosives for this type of hull. You’re inside.”

By the way,

We were playing Klingons v Klingons using the Hero System.

That’s when I knew that Hero could do just about anything.