How much space does the blockchain take up per day and per hour when running bitcoinQT on my computer?
The blockchain size growth is kind of approximately linear at this time (although I wouldn't expect it to continue linearly). See the nice graph at https://blockchain.info/charts/blocks-size and particularly check the "All Time" scale option.

Over the past year, the blockchain size has grown by approximately 10 GB. On average, that would be around 27 MB per day, or 1.1 MB per hour.