How do solar cells work?
Solar cells utilize a physical phenomenon called the photoelectric effect to produce an electric current. Albert Einstein won a Nobel prize in 1905 for detailing this amazing effect.
In simple terms, there are certain materials that produce electricity when they are exposed to light. This occurs when the light knocks some of the electrons loose from their host atoms. When we attach conducting material to the positive and negative sides of the material to form a circuit, we can channel this electrical energy.
The very first solar cell was built by Bell Labs over 50 years ago. The first serious use of solar cells was by the space industry as it was a very convenient way to power satellites. Today, the cost of solar panels are low enough for residential use.
How efficient are solar cells?
The efficiency of a solar cell refers to how effectively it can convert the light that hits its surface into electricity. With current technology, the efficiency can be anywhere from 6% to 44%. Common residential solar cells have an efficiency range between 15%-20%.
When manufacturers measure the efficiency of their solar cells, the must do so under standard test conditions (STC) to ensure that everyone is playing by the same rules. The STC’s correspond to a clear sunny day with a temperature of 25 degrees Celsius.
Even though the solar cell efficiency is an important factor, most people value the $/watt criteria more than the efficiency. The cost of solar cells increase exponentially as the efficiency rises so the key is to find a good balance between economy and efficiency.
Is it a solar cell, panel, or array?
A typical solar cell consists of a glass or plastic cover, an anti-reflective layer, a front contact to allow electrons to enter a circuit, a back contact to allow them to complete the circuit, and the semiconductor layers where the electrons begin and complete their journey.
When you put a bunch of solar cells together you get a solar panel (see image on left). If you connect a collection of solar panels then you get a solar array.
A complete solar photovoltaic system includes a solar array, a power center that feeds a DC-to-DC converter as well as a DC-to-AC converter (called in inverter), and either a battery system or a tie-in to the city’s power grid.
What's the latest in renewable technologies?
Here are the latest developments.