Summary: Just as with the NiMH battery packs used for current hybrid propulsion systems, ultracapacitor blocks are made up of individual cells such as the BoostCap model pictured above. Hybridize that big inernal combustion engine driven bus with them and you get this ride. Ultracapacitors function similar to batteries, but store the charge in an electrostatic field
Image Dimensions: 362 x 258
Image originally found here.