Hi Pete,
Your example can be calculated, but some more information will be needed. As far as the basic power requirement, you are lifting a 30KG load 1100mm in 30 seconds. I'm going to switch to english units for a moment here to get the power - 30Kg=66.138lb=294.196N. Power (watts) is N-m/sec so you have (294.196N x 1.1m)/30sec = 10.78Nm/s which equals 10.78 watts which is around .014hp. This value is the basic power requirement - a factor of safety needs to be added to the value. You need to multiply this number by 2-4 times to account for unknowns. One very important issue - if this mechanism is to be used in a way that a failure could lead to injury or worse, you need to be very careful and possibly consult with someone who can certify your design. My input is for general information only.
To get a torque requirement, you will need to establish what rpm your motor or screw will be running. To get an rpm, you will need to select the lead (linear travel per turn) of the screw. This brings up screw selection. If you want the load to stay put once you turn the motor off (non backdriving), you will need to select a lead screw with a short lead and lower efficiency. This does not mean the screw is "bad" but rather a term for lead screws and nuts that relates to the backdriving ability. In other words, you definitely don't want to use a ball screw. In addition to being expensive, not matter how short the lead, they can backdrive on you and once you shut off the motor, the load can drift back down or come down quite rapidly depending on your lead.
As far as screw diameter, the rpm and the length of the screw between supports will determine what diameter you need. If you are running at high rpm with a long distance between supports, the screw can hit its critical speed and start to whip. I don't think you will have that problem but it's good to keep in mind. Here are some companies that make lead screws. They have very good documentation for designing a lead screw system:
Links removed....
Design guides will have examples of different support options for the screw and how it affects the operation of the screw.
Hope this helps.
Kyle