Different types of solar energy systems provide power for specific applications. Among these types of solar power are passive and active solar, as well as concentrating and nonconcentrating solar. To clear up some of the confusion regarding the types of solar energy systems and their respective applications, check out the breakdown below.

Passive Solar Energy – passive solar energy is used to convert sunlight into usable heat, cause air-movement for ventilation or cooling, or store heat for future use. Passive solar works best and proves to be most cost effective with building designs that are intended to effectively capture the sun’s heat and light. A simple example of a passive solar energy system is a greenhouse.

Key features of passive solar energy systems include:

• No conversion of solar energy into electricity – the energy is simply collected and used or stored
• Site selections and building placements maximize synchronized heating & lighting
• Windows are placed in south-facing walls
• Vents and ducts are moved to capture heat through the building
• Trombe walls – dark, south-facing walls that absorb light and heat
• Wide eaves
• Heat-storing slabs
• Superinsulation

Active Solar Energy (Photovoltaic or Thermal) – active solar energy captures the sun’s energy in order to store or convert it to thermal or electric power. In active solar energy systems, there is an active and intentional collection and redirection of energy.

There are two main types of active solar energy:

• Thermal – used to generate heat for hot water, cooking, heating, melting, steam engines, etc.
• Photovoltaic – used to generate electricity for both grid-tied and off-grid systems

Photovoltaic solar energy systems work by allowing light to hit the specific molecular structure, which consistes of a semiconductive substrate (usually silicon) that has been “doped” with chemical additives that create opposing positive and negative layers (known as the P and N types). When the photons of light strike the surface of the substrate, this causes electrons to move from P layer to N layer. This movement of electrons creates the electric current that powers many solar homes and buildings, as well as orbiting satellites.

Concentrating & Nonconcentrating Solar

While nonconcentrating solar does not involve the use of mirrors or other means to directly focus the sun’s light, concentrating solar uses mirrors to either focus sunlight on a PV array or to heat water or other fluids to create steam that drives turbine generators.

Concentrating solar is more complicated to build & manage, which translates into higher cost. Furthermore, concentrating solar involves moving parts, resulting in more maintenance. Accordingly, concentrating solar is more often used in larger-scale, centralized systems at commercial energy plants that tend to serve upwards of tens of thousands of homes and businesses.