Draconic Evolution allows you to store HUGE amounts of power (up to 9,223,372,036,854,775,807 - 9.22 x 1018!); this multi-block structure can be upgraded and should be enough for all of your energy storage needs.
First, craft and set down an Energy Core around ten blocks above the ground; the reason for ten blocks is that as you upgrade the core, the bigger it will get in size; I would advise around 15 blocks.
Clicking into this block will allow you to set the Tier, the build guide, and if the core is active or not. The build guide (when enabled) will show you what blocks need to be up around the core for it to be valid; you will also need stabilisers.
If you are building tier 1-4, you will need four stabilisers around the core, but once you reach higher levels, you will need to make a 3x3 wall of stabilisers (advanced stabilisers as a multiblock) around the core. You can still configure and turn on the reactor as long as the stabilisers are in the correct position:
Now, these stabilisers can be set on horizontal or vertical planes:
Once the core is active, you can click the stabilisers again to see the core status, such as the transfer rate (positive or negative), amount the core can hold, and how much the core current is holding.
To transfer energy in and out of the core, you will need to place down 2 Energy Pylons. Place glass adjacent to the Energy Pylons, in the direction of the Core. Right-clicking the Blue ball will set the pylon to input or output mode. These pylons will bind to any core within a 16 block range. If there is more than one core around, it will split the energy. To check what core these around are bound to, you can right-click the pylon to send a blue bolt to the bound core. Each face of the core is limited to 2,147,483,647RF/T.