Solar Photovoltaics

Solar Photovoltaics (PVs) Make electricity directly from sunlight without pollution, moving parts, or on site noise Sun covers the Earth with over 5,000 times as much energy as is used by all of humanity PV panels have limited efficiency and buildings have limited area for them Generally expensive Use passive designs before using solar electricity generation

PV Power Production Depends on 5 main factors – Site conditions: latitude, longitude, and local weather – Orientation and exposure of the panels to the sun – Efficiency of the panels – Available area for the panels – Power conversion electronics

Site conditions How much sunlight hits the site? – Known as “solar potential”, “incident solar radiation”, or “insolation” – Wh/m 2 x day – kWh/m 2 x year – Look at various maps available Determine how man kilowatts of energy strike the site per square meter per year to help calculate the size and efficiency of the PV you will need

Orientation More directly the sun shines on it the more energy generated Use the same angle as the latitude (in degrees) To max for winter add 15 degrees, for summer subtract 15 degrees Some are mounted on poles and follow the suns path

Efficiency (5-20%) Crystalline Silico – higher efficiency, lost performance in overcast skies Thin Film Concentrating – require full direct sun

Area Depends on the efficiency of the panels and amount of sunlight Less expensive panels require more area Typically on roofs, but over parking areas provides shade Building integrated photovoltaics are built into building products