I will admit THIS IS NOT MY DESIGN, I saw it on Direwolf20's Lets Play and wanted to see how it worked... (It was build by Zeldo who made Teleport Pipes For Buildcraft)
Anyway showing the design..
This is a tiny bit over a quarter of the max size of this design, but it is extremely efficient.
Surprisingly, only one quarter of the max power is a whooping 820EU! The secret of the huge size is in tin cables, and how power works in IC2. I know you are thinking "Tin Cables can only hold 3EU, how are you passing 820EU through it??" It is true tin cables can only hold 3EU packets before melting, but they can hold an UNLIMITED amounts of packets. They cant hold one 32EU packet, but they can hold 820+ packets of 1EU. Also, tin cables are very cheap, and can extend 40 blocks before lossing EU. The only problem is that after 40 Blocks, you lose 1 EU per packet, which in the case of solar power, you get no power at all!
Solar Array can be VERY big!
Tin Cables are cheaper than copper cables, and you dont need rubber for the cables.
Easily can get over 2000EU/s with a full array.
No batboxes are needed, other than one MFSU in the middle.
Can't Have tin cables over 40 blocks.
Has to built during night to avoid extreme lag spikes.
Is very CPU Hungry.
Hope you guys like this Design!