Hard drive and power consumption of current Time Capsule
Since it's a 2TB or 3TB storage you can be sure it's HDD, since the price is 'only' 299$ or 399$. There are for the moment no (commercial) 2TB SSD drives or maybe one or two which are really really expensive. On the product page is also stated that the Time capsule is ussing a Hard drive, otherwise there would be stated Soild State drive or similar.

The enviromental report, including energy usage can be found here: https://www.apple.com/environment/reports/docs/AirPortTimeCapsule_PER_feb2014.pdf