Solar Energy Primer

Solar energy in a general term that refers to any kind of technology, mechanism or construction method that converts sunlight into usable energy. The ‘usable energy is almost always electricity or heat.  Because this page is a general page about how solar works, it will not differentiate between home uses and commercial or utility uses.  The major difference is that some technologies do not make financial sense in small-scale operations, which makes them unavailable of less viable for homes.

However, since our comparison supports decisions for how we power our homes as well as how we vote and support technologies at the larger level, we consider all of this understanding to be useful.

Solar energy to create electricity:

Sunlight can create electricity directly using photovoltaic cells (PV), also called solar panels, or indirectly (below) by collecting heat and using the heat to run generators.

Direct production: Photovoltaic (PV) cells

In any PV system, the power that can be generated is proportional to the amount of sunlight that can be collected.  Since there are efficiencies of scale for large applications, utilities and businesses use many PV cells together, called an array.  This is what it means to hear ‘solar array’ or ‘array of solar panels.

There are major and minor differences from one PV system to another.  Here are the major variables:

Panel position:

Fixed: Panels that remain in one place and do not more are called ‘fixed’.  This is less expensive to set up but does not produce as much power when the sunlight is not direct.

Tracking: Panels that ‘follow’ the sun by moving throughout the day.  These are more expensive and complex but produce more power.

location (not moving) or tracking (follows the sun).

Solar Concentration:

Typical solar panels, whether fixed or tracking, absorb the sun’s energy directly.  Some systems ‘collect’ light from a large area and concentrate it.  A panel that is directly facing the sun can absorb, at most, 1 ‘sun’ – essentially ’1 sun’ means a panel is collecting all it can for its size.  A panel that concentrates light from an area larger than itself has more than 1 ‘sun’ worth of light being used.  The number of suns represents the area of sunlight collected compared to the panel.  For example, if 2 square meters of light are focused on a 1 square meter panel, the panel is working at ’2 suns’.

2m^2 light / 1m^2 panel = 2 suns

Solar Panel Material:

Solar panels are made from different types of material, with different costs, efficiencies, operating characteristics and performance history.

Panel integration (Building Integrated Photo Voltaic)

Many commercial arrays and some home arrays are placed on the ground, and are basically non-integrated.  In some areas that are otherwise suitable for PV, the space isn’t available.  Also, non-integrated arrays require dedicated support structure (the physical structure that holds it in place).  Putting arrays on a rooftop address the first issue by preserving ground space but still requires its own support structure.

Building Integrated Photo Voltaic addresses all of these issues by 1) using space on a building that does not displace area usable for anything else (like a rooftop), 2) serving the original purpose of the material it displaces serves to ‘fund itself’ by offsetting another existing cost.  E.g. roof tiles that generate electricity.

Indirect Electricity Production

tbd