Solar energy:

Solar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP). CSP systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. PV converts light into electric current using the photoelectric effect.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What does a concentrated solar power system use?
lenses or mirrors and tracking systems