Years ago (back in the 70s) I recall a study about harvesting energy from sunlight which compared PV cells, heating water passing down black pipes, reflecting sunlight to a focus point to heat water.... and the most efficient (though probably not scalable easily) one tried was similar to this.
1) Put some plates of wet glass in the sun** and wait
2) Scrape off the algae that forms for free, put the glass plates back
3) Ferment the algae with some yeast to make (mostly) ethanol & water
4) Use sunlight to help distil off the ethanol
5) Burn ethanol to release energy
[and since this is Slashdot 6) ??? 7) Profit ]
Now the wet glass plates were used for ease in the experiment; scraping the slime off shallow ponds may be easier (and you have the bonus of a pond to use as a heat sink). Old bottles work as well, if not better than glass sheets, as evaporation losses are lower, but scraping out the green slime is harder.
Most of the process (algal growth, fermentation....) is self sustaining and doesn't need much in the way of handling.
** doesn't need strong sunlight-- the experiment was done in the UK