Solar techology 101: Inverters
Vail, CO, Colorado
Today’s home solar electric power systems are a remarkable technology spinoff of the space age of the 1950’s and 60’s, initially developed to produce electricity needed by earth-orbiting satellites and deep space probes when no other fuel source was practical or available. Solar photovoltaic cells are the only technology that can produce large quantities of energy with no moving parts.
But how do they work?
In most modern solar modules, particles called photons that are emitted by the sun strike a layer of silicon quartz that has been treated to make it rich in electrons. The photons strike the electrons, which then develop electricity. In bright light, many cells wired together deliver a usable source of energy.
The energy delivered by a solar module is DC, or direct current. This type of energy is perfect for powering satellite electronics and charging batteries, but to easily use it in our homes and businesses we have to convert the DC power into conventional alternating current, or AC, power.
In order to develop useful AC electricity from solar modules, an inverter is connected between the DC from the solar array and the incoming AC grid. Today’s inverters are typically solid state switching power supplies which chop the DC into a high frequency wave, then match the output to the incoming grid voltage and frequency, and then shape the output into a wave acceptable to the grid operators.
The electric grid fails from time to time. Solar power systems tied to the grid sense these failures immediately, since they sample the grid power constantly in order to synchronize their energy’s phase with it. When the incoming power fails, the inverter shuts down immediately to prevent injury to the line personnel who will have to restore the utility’s power. Once grid power returns, the inverter checks it for proper voltage and frequency, waits a minute or two to make sure it doesn’t fail again, and then resumes selling its energy to the grid.
If a solar power plant owner desires, he or she can add a bank of batteries to a system and, using an inverter designed to use them, power a home or business during grid power failures. These battery-backed inverters sense a grid failure and immediately switch their loads to the power they continue to make while simultaneously cutting off any power transmission to the grid itself. When the grid power comes back on, loads are switched to the grid and energy selling resumes.
Many industry and utility managers believe that battery-backed systems will become more popular in coming years, as the grid itself is increasingly supplied by large-scale wind and solar systems, which, by nature, are intermittent. Until it is redesigned to better accommodate nature’s variances, the coming “greener grid” may have to shed loads as the wind slows and clouds shade solar panels.
Battery-backed solar plants distributed across the grid will ensure our homes and businesses remain fully powered at all times.
Today’s solar electric systems are efficient, long-lasting and are a proven way to fix ever-rising energy costs. Properly designed, they can help assure a continuation of today’s lifestyle in a future that promises to be more expensive and perhaps even more chaotic than today’s world.
Bill Sepmeier is chief technical officer and Matthew Charles is the design and sales manager for Grid Feeders in Eagle-Vail. Contact them at 970-688-4347.