Originally Posted by DarkDuck
to turn Cobble to Lava you need 20000 MJ
An electric Engine (without upgrades) produces 5 mj/t for 12.5 EU/T
So rough maths you need 4000 Cycles of a normal electric engine to produce enough energy so thats 50,000 EU needed for 1 Lava Source Block.
1 lava block only produces 20,000 eu so you would not be able to keep up with demand.
I still point you towards a petro generator, 300,000 eu from 1 bucket of Fuel!!!
8,000 EU at 8 EU/t for Biomass
32,000 EU at 16 EU/t for Biofuel
For the Petro Generator
A bucket of Oil will make 30,000 EU at 10 EU/t.
A Bucket of Fuel will produce 300,000 EU at 25 EU/t.
The real reason to use EU (or BU for that matter) is storage. Storing MJ is a pain and is (supposedly) buggy on full conditions for the storage. Storage is also very small (600K MJ is nothing).
Converting MJ to EU is best done using the magma generator tied up to a geothermal BUT make sure you power the magma generator with a proper MJ engine (3 combustion engines using biofuel for example do a decent job and give you a little pause to pick up some more cobblestone when they empty). This gives you about 250K EU per biofuel bucket, which is much more efficient that the Bio Generator.
If you wish to convert BU (solar) to EU I would suggest solar -> BU store -> Bluelectric Engine -> Magma Generator -> Geothermal Generator. It is a bit of a pain, but if you wish to do it that would be the route for the solar panels or the thermopiles.
MJ converts to EU (in this method) at a rate of 1 MJ -> 1.25 EU (Geothermal gives 30K EU/lava for 24,000MJ input). Do NOT use Electric Engines to power a magma generator as the best you can do is 2.5EU -> 1 MJ.
So, you would get 1kW of BU becomes 1.25EU using this method. Based on the Bluelectric Engine stats you only need one engine per magma generator.
So, in theory (with a max output of 200W each) you would need something like 75 solar panels to operate the engine/magma combo continuously (15kW). A battery box would empty in something like 20 seconds (300kJ) I guess.
All in all, interesting but not efficient. I recommend Duck's fuel burning! Of course you can get more EU using the magma route (1 fuel in a combustion gives 600,000MJ -> 750kEU) but it may not be worth the pain of setting it up. It is, though, another way to remove all that cobble!!!