Tense in summary chapter of a thesis
It's not really about if you have mentioned the work before (don't get confused by the instructions), but that the work itself was done before.  So stick with the past tense for the situation here.

In general*, the past tense is safer than present or future.  Probably 95%+ of the time you should be in past tense when writing a technical report.  And if debating, past or present (either might work), you are usually better off going with the past.  Only do the present or future if you know what you are doing as a writer and have a strong reason to change the tense.  

*Caveat.