Project Help!!

[KrisBlueNZ]

Cool, so it does!
These look like they would work, assuming the magnetic characteristics are enough for your application. They are rated for 24VDC operation. The one with -030 in the part number has the lowest power consumption, 10W. At 24V the current will be:
I = P / V = 10 / 24 = 417 mA. The circuit I suggested should be able to supply it as shown. It will work from 24VDC. Use a decent sized battery - a battery of C cells at least, preferably D cells, or even larger.
Can you get those electromagnets in small quantities?

 

[Marsell4k]

I'm not planning on using this exact one, but would require something like a small (apx 15x10mm) plate. The magnet would only need to be strong enough to hold the door closed and resist around 10-15kgs of force whilst locked (natural, non energised state). Can't find a magnet or company yet that does something similar. Could you give examples of how to generate the 24 volts with C & D cell batteries? Wouldnt that take a lot of them?

 

[KrisBlueNZ]

Yes, you'll need sixteen cells (24V divided by 1.5 volts per cell is 16 cells). You connect them in series (nose to tail in a line). You can probably get six-cell and four-cell holders. Alternatively you could use four 6V "lantern" batteries connected in series. These are modular batteries, base about 2" square and about 3" high, with two springs on the top. They're made from four E cells, I think. They're often used in large lanterns (flashlights).
I just noticed that the data sheet for those solenoids recommends driving them with constant current. This requires a few small changes to the design. Also, the circuit I posted most recently will not work from 24V because the maximum gate voltage for Q2 will be exceeded.
I've attached an updated schematic assuming you'll be using the Magnet-Schultz part. Let me know when you've chosen your solenoid, as I may need to update it again.
Kris