Much of the space are likely to be taken up by batteries, as the air-cond unit takes up the space where the battery pack normal goes on the E40H. Also, I expect the E50H has more batteries as well, in order to cater the heavy power duty.
其實都有電池的問題，只係少 d 咁解....
如果 n 年後電巴電池體積可以細到同油箱差唔多，柴油巴士消失都好難避免....
There are other options. One is recharge hybrids, for which about 13 E40Hs will be on trial in London imminently and the system shall be similar to the one in Milton Keynes. Volvo also trial a very similar system in Gothenberg with pretty good success as well. However, by far the biggest issue is infrastructure costs, and I can't see HK operators picking up the bill sadly.
The other, IMO a much more viable option for HK in short term is flywheel hybrid. This system does not give as much benefit as battery/recharge hybrids, but is much cheaper, and have negligible weight and space penalty. Both ADL and Wrightbus have been offering them onto their single decker products and this can well be a better solution in short term.
