A standard audio CD requires approximately 650 MB in uncompressed WAV files which comes down to about 10 MB per minute. I assume you are encoding 16 bit 2-channel audio with a sampling rate of 44.1 kHz.

If you are compressing the files with a lossless compression algorithm such as FLAC (Free Lossless Audio Codec) or Apple Lossless, you would only need have the capacity without incurring any sound quality loss. If you want to archive high-resolution 24-bit files, you need a bit more space.