Active vs. Passive Solar Energy

Passive solar: absorbing or blocking heat from the sun, without use of mechanical/electrical equip.

• Using sun’s heat to cook food in a solar oven.

• Orienting building design to block sunlight in warmer months and allow sunlight during colder months.

  • Double paned windows, southern facing windows with roof overhang, deciduous shade trees, skylight to decrease electrical use, dark colored sunlight orbs, floor.

Active solar: use of mechanical/electrical equip to capture sun’s heat (solar water heaters or CST-concentrated solar thermal), or convert light rags directly into electricity (PV cells).

• Solar water heaters capture sun’s heat in water or circulating fluid and transfer heat to warm water for home - in place of electric/gas water.

Photovoltaic Cells (PV)

• Aka “solar panels”; contain semiconductor (usually silicon) that emits low voltage electrical current when exposed to sun.

• Photons (particles carrying energy from sun) cause separation of charges between two semiconductor layers; electrons separate from protons and flow through circuit to load, delivering energy (as electricity).

  • PV cells on a roof can directly power the building, or send excess electricity back to the grid for other users (earning you a credit from your utility company - SRECS)

Community (solar farm) vs. Rooftop Solar

Large-scale solar “farms” can generate lots of electricity, but do take up land and cause habitat loss/fragmentation.