The LOEWE Centre "emergenCITY - The Resilient City" deals with the question of how the functionality of cities with their digitally networked infrastructures can be ensured in extreme situations, crises and disasters. The solution concept is interdisciplinary and includes modern information and communication technology as well as the historical, legal, social and structural aspects of urban planning. 

LOEWE-emergenCITY task: Build a lemon battery that can be used to generate electricity 

Building instructions: You will need a juicy lemon, a pair of headphones, two small cables, a zinc washer, a copper coin, and two copper paperclips. 

First, the zinc disc and the copper coin are wired. To do this, you have to remove a small piece of the cable sheathing at both ends. Then use the paperclips to connect the zinc disc and the copper piece to the two cables. Now cut two slits in the lemon, one to two centimeters apart. The wired zinc disc is inserted into one slot and the wired copper piece into the other. Wrap the free ends around the contacts of your headphones. Wrap one wire around the top contact and the other around one of the two bottom contacts. With the headphones you can now check whether the current is flowing. A faint crackle should be heard. 

LOEWE-emergenCITY additional task: lemon bill. 

Assuming that your apartment uses 10,000 Wh of electricity in one day. And suppose the lemon battery can generate 0.0025 Wh of electricity. 

Have fun & good luck with the solution!