Peltier junctions are flat and very efficient heaters as they heat from 2 sources, the wattage u put in and the heat pump action. You will need a finned heatsink & a fan to spread the heat around though.
You need a 12-16VDC supply to do it.
If u want to run off mains....use a series of higher wattage ceramic block resistors or wire wound resistors. For a 120V supply, which gives an rms of 120V * .7071 = 84.85 V. Power = VI.
I=P/V =30/84.85 = .354 A
V=IR, so, R= V/I, = 340 Ohms of resistance required.
For best radiant action get a number of 5W resistors....perhaps 11 , 30 - 33 Ohm units, string 'em in series, paint 'em black. Array them in a grid to radiate the heat from the bottom of the space. Job done.