The sun's heat and light provide an abundant source of energy that can be harnessed in many ways. Photovoltaic power systems convert sunlight into electricity directly. Research and development efforts are under way to improve efficiency and reduce cost of photovoltaic power systems in applications ranging from roof-top residential to large industrial or electric utility sites. Topics covered include:

• The solar resource: irradiation, tracking or fixed installations, concentrators, site evaluation (NREL PV Watts performance calculator), economics of PV systems
• Applications: standalone residential, grid-connected residential, industrial, utility
• Technology of photovoltaics: monocrystalline and multicrystalline silicon wafers, thin film solar cells, models and voltage-current characteristics
• Power electronics in photovoltaic systems: system architectures, DC-DC converters, peak power tracking, batteries and charge controllers, DC-AC inverters and grid interface

Semiconductor material absorbs photons and converts photons having sufficiently high energy into hole-electron pairs. A standard electrical circuit model consists of a photogeneration current Io proportional to solar irradiation in paralel with a diode. The cell short circuit current Isc is proportional to the number of absorbed photons. The cell open-circuit voltage Voc depends on the semiconductor diode characteristic. The maximum output power is obtained when the cell operates at the peak power point (Vpk, Ipk).