I posted this a week ago on r/feedthebeast, getting a few posts but not much beyond that. So, I’m leaving it here for a more topic focused group.
I have a few energy generation ideas aiming for the mid-game but can be expanded for end-game, ranging from the upgraded forms of existing generators to new sources of fuel.

Wind Turbine, MV
A bigger and more efficient wind generator, the wind turbine is a multi-block tower structure that raises a larger rotor off the ground. Like the wind-mill, it is affected by altitude but due to safety concerns it is not affected by weather. The rotor uses three wing shaped blades made from either lower power but cheap aluminum or higher power but expansive carbon fiber (made from lots of coal).

Natural Gas, MV
Underground Natural Gas deposits are semi-common happening in clusters with a greater occurrence in “flatland” and “dry” biomes, only the core sample drill can detect if there is a deposit. All that is needed to access the deposit is a tapper well, the deposit is under pressure thus no power is needed for extraction. Natural Gas is burned in a turboshaft turbine generator outputting 1024 rf/t, without any need for refining. However, just like any other burnable resource, the supply is finite. And yet unlike other finite resources it can be extended by using an Injector Well with a mix of water, plant oil (or lubricant if Immersive Petroleum is installed), and energy to frack the deposit with 3x to 4x the max amount while active. Fracking may have unexpected side effects to the surrounding area, like tainted water (reduced pump speeds), broken bedrock, and sinkholes (uses stone over air to detect caves to collapse, will break any multi-block structures caught by it, think black decay from Mystcraft).

Geothermal, MV to HV
Another underground resource that have a greater occurrence in “ocean” and “cold” biomes, that comes in two types; the rare saturated thermal layer and the common porous thermal layer:

• A saturated thermal layer only needs to be tapped, with a tapper well, to produce steam that is sent into a steam turbine generator for constant MV (1024 rf/t) power. It easier to find as it causes a physical manifestation in the world, Prismatic Hot Spring when on land and Hydrotherapic Vents when underwater producing a column of bubbles.
• A porous thermal layer however requires a core sample drill to find. It needs an Injector Well to inject water down to the thermal layer before producing steam. The returning "dirty steam" is full of turbine damaging contaminates thus needs to pass through a heat exchanger to convert (up to 1-3/8 per well) water to "normal" steam for use in a turbine, with the rest dissipated and the contaminates dropping out the bottom (sand, clay, a random grit, etc.). If 4 nearby wells are tapped this way, a fifth turbine can be used to maintain the injectors leaving 4 turbines for combined HV power production @ 4096 rf/t.

Hydroelectric, LV to HV
This by far would be the hardest to pull off in a balanced and lag suppressed way, so this is my concept: the hydro turbine will use the detected volume of water within a defined range. There is no change to the volume of water other than being detected, just like wind generators making energy when Minecraft has no wind. There are several rules for it to function properly:

• Energy output is dependent on the total detected water source blocks behind it within a Y range multiplied by a config set number, normally a very low value like .05rf/t per cubic meter. The base range is 3 (small) or 5 (large) blocks high, from the (bottom) intake to the top of the generator, but this can be extended by adding more intake blocks to the base intake at a 1 to 1 (small) or 4 to 1 (large) rate.
• Hydro Turbines comes in two sizes, Small that is limited to MV voltages and Large that can handle HV voltages.
• The generator base must be above Y level 70 to prevent players from "damming" the sea and to make it only truly viable in hilly or mountainous biomes. But the level can be changed in the config.
• More than one generator can share a volume, but ALL generators will divide the total potential energy evenly, even if a generator is at a different level, range coverage and/or size. A volume will always produce a set value of energy, no more, it’s how that energy is divided that counts.
• The Hydro Turbines only has 1 energy connector point but has the potential to produce more energy than the connector can carry. For large dams, getting the most out of the energy potential, or for the purposes of limiting voltage levels it’s best to use multiple Hydro Turbines.
• There must be water behind the intake pipe(s) to detect the intended water volume. If the pipe is blocked, it can’t detect the volume thus no power is produced!
• To keep server/client stress low, it only detects once formed, wacked with a hammer, after a short time of being loaded, and every config set time period looking for any changes to the volume (question: will converting detected water into self-reporting reservoir water help?) There is also a config set volume limit.
• Whacking HydroGen with a hammer redetects the water volume and outputs the range size, volume detected, energy potential, and current energy production in chat. If energy production is greater than the possible energy output MV or HV, than more HydroGens may be needed.
• A regular pipe can be placed on the turbine “out” pipe(s) to recycle the water for other uses, otherwise while active it’ll place a water flow block(s) if it can.

I tried making the rules as realistic yet practical as posable. But knowing Minecraft players, someone is bound to make a massive tank of water to farm. Although this may be a necessary in skyfactory modpacks.

Multi-Block Structures
I’m not very good at designing multi-block structures, but that doesn’t mean I won’t try:

• Wind Turbine Tower: a 3x2x3 base for energy connectors, Redstone control, and tower foundation, the tower is aluminum sheet metal with treated fences on all four sides, and the top is 3x3x5 with heavy engineering blocks core and generators on the back, shrouded by aluminum sheet metal blocks/slabs
• Tapper Well: 2x3x2 a pump over a pipe with a pipe leading off, aluminum scaffolding supporting a Redstone valve controller.
• Injector Well: 3x3x3 a pump over a pipe with four pipes leading into the pump, steel scaffolding supporting the pipes and heavy engineering blocks in the corners. Needs 256 rf/t to continuously inject its content(s) underground.
• Turboshaft Turbine Generator: 3x4x6 for 4 blocks on one side is heavy engineering blocks core contained in light engineering blocks, and steel scaffolding supports on either end, generator blocks on the side with a steel sheet metal covering the shaft. Note: very loud, high pitched noise.
• Heat Exchanger: 4x5x3 steel sheet metal forming the thermal transfer tank held up by treated fence posts with steel sheet metal (upper) slabs, and a hopper in the center. 1 fluid input and 1 fluid output on top, 1 fluid input and 1 fluid output on either side, and an item output below. It can even use lava as the heated fluid, 1,000mb out putting 1,000mb of steam and one cobblestone. Or any other hot fluid from other mods.
• Steam Turbine Generator: 3x3x6, a >< shape is formed to get the maximum energy out of the steam with a few generator blocks on one end allowing up to 3 connectors.
• Small Hydro Turbine Generator: The generator itself is 3x4x4. Treated wood base and back wall except for the lower “out” pipe and the "intake" block on one side feeding into the 3x1x3 heavy engineering blocks water turbine and the 3x1x3 generator blocks, and 1 generator block with steel sheet metal slabs on top of it. max output: 1024 rf/t
• Large Hydro Turbine Generator: The generator itself is 6x6x7. Concrete base and back wall except for the lower 4 “out” pipes and the 4 "intake" blocks on one side feeding into the 6x2x6 heavy engineering blocks around 2x2x2 steel blocks forming the water turbine and the 4x2x4 generator blocks surrounded by steel sheet metal, and 4 generator blocks with steel sheet metal slabs on top of it. max output: 4096 rf/t

Items/Fluids

• Aluminum Rotor: lots of aluminum plates and ingots, bound together by aluminum wire. Used to make 3 rotor wings and the rotor core, for the rotor. Can be arc furnaced for 90% recycled ingots. 340 rf/t at the highest level, 20 rf/t at the lowest (bedrock).
• Carbon Fiber Rotor: crushed coal, pressed 9 into 1 (can’t be crafted), arc furnaced, and pressed again 4 into 1 (can’t be crafted). Used to make 3 rotor wings and the rotor core, for the rotor. 512 rf/t at the highest level, 30 rf/t at the lowest (bedrock).
• Natural Gas: Tapper Well over a deposit, used in the Turboshaft Turbine Generator for MV energy.
• Steam: Tapper Well over a saturated thermal layer or heat exchanger from water, used in the Steam Turbine Generator for MV energy. I know that BluSunrize isn’t to keen on steam generation, however most thermal based power plants relay on steam for energy production. Look at it this way, if you leave in place a steam turbine generator other modders can make add-ons for other forms of fuel and/or make it more compatible with other mods that use steam.
• Dirty Steam: Tapper Well over a water injected porous thermal layer, 1,000mb used in the heat exchanger to produce 1,375mb of steam. Can be feed directly into a steam turbine, but eventually, given time, that turbine will catastrophically fail with an explosion destroying itself and anything near it.
• Intake Pipe: 8 steel plates surrounding a pipe. 1 for small and 4 for large, will increase Hydro Turbine Generator’s detection range up by 1.

I think most of these would fit better as addon mods. If I knew more about modding I would take a crack at one, but as it stands I have very little experience with it (though I am learning).