I'm thinking of creating infinite lava source and I found a way but it's efficient at all. Actually not "not at all", it's not efficient. Magma Crucible can turn cobblestone into lava at the cost of 24000 MJs. But at the same time a bucket of lava can produce only 18000MJs. So we lost 6000MJs. And also to keep Magma Crucible filled with cobblestone we need cobblestone generator and a Block Breaker. A Block Breaker uses 96 MJs to break a block. So that means to create 1 bucket of lava we use 6096MJs. Not efficient but if you need lava for something else, now you have it.
Or you can power Magma Crucible and Block Breaker with Redstone Engines. But you will need at least 301200 engines. And also there is %5 power loss per block and I'm not even getting into this.