Electricity and energy

Electricity is flowing in our bodies to power our hearts, lightning strikes the earth roughly 100 strikes per second, and much of human productivity and also environmental destruction result from our reliance upon it. Sometimes it seems everywhere, but the reality is that there continue to be nearly a billion people without access to electricity globally. The primary issue has always been that electricity was always produced in a few select locations and then distributed out from there in an electrical grid to homes and businesses, which can be very expensive to expand. Grid-tied PV systems can be used to help reduce the environmental impacts of electricity use and off-grid PV systems can help provide energy to areas where the grid doesn’t reach as they are able to produce, store and provide energy in the form of electricity even in the most remote locations.

Right: Most power grids rely on centralized forms of generation (coal, natural gas, nuclear, large scale hydro to produce electricity that is distributed to homes through the tranmission and distribution lines. Left: Off-grid PV systems are independent of this system.

A PV system needs to be designed to match the characteristics of the electrical system in an area and the energy needs of the end-user. Not just designers and installers of off-grid systems need to understand electricity and energy thoroughly, but also users to make sure that they do not damage their system by using it beyond its capabilities. The main concepts that are necessary to understand are:

• Current
• Voltage
• Resistance

These are the building blocks of even the most complex electrical systems. The best way to begin to understand the almost always invisible force of energy is through using comparisons with water. Flowing water and electricity have a lot in common.

What is electricity?

Electricity is a force created from the basic building block of all matter - atoms. All atoms are composed of three core components - neutrons (no charge), prontons (positive charge) and electrons (negative charge). Out of these three, the only one that is able to freely move from atom to atom is the negatively charged electron. Electrons can build up in higher concentrations in some locations and create a negative charge. Or there can be a lack of electrons, which create a positive charge. Electrons desire to flow from areas of high electron concentartion to areas of low electron concentration. Not all atoms or materials have free electrons that can move around easily - most do not like wood, plastic rocks - we call these insulators. Metals and copper are good conductors as they have abundant free electrons.

The small static electric shocks that we receive from our cloths are the result of a difference in electrons from your body to that item - this difference is voltage. As the electrons pass from your body to that item of clothing a current is created.

A cross-section of a copper wire with its atoms enlarged. The electrons are flowing from atom to atom on their way from areas of high concentration to areas of low concentration.