Solar Basic Overview
Solar History
People have been studying how plants convert sunlight into food for many centuries. Around the mid 1800’s the photovoltaic effect was discovered and developed. Copper and Selenium were the principle driving advances in solar power with nothing really changing until the early 1950’s. As vacuum tubes gave way to computer chips it became obvious to most that silicon was light/heat sensitive. Only in the last few decades-when growing energy demands, increasing environmental problems and declining fossil fuel resources made us look to alternative energy options-have we focused our attention on truly exploiting this tremendous resource. The requirement for energy in space for powering satellite systems provided a big impetus to advance the technology. NASA was really the first large scale uses of solar electric panels.
Back in the 70’s the energy crisis pushed solar PV to the forefront of energy generation choices, but the market eruption was strangled by prohibitive prices to the common customer. Today we are happy to finally see the renewable energy market explode. Despite the difficult technology, the manufacturing prices have dropped considerably. The efficiency of the solar cells has almost doubled allowing the world’s energy consumption to tap into a new and practically inexhaustible source… the sun! Not too long ago installing a solar energy system may have seemed a difficult task to accomplish.
The Fundamentals
Each day more energy falls to the Earth from the sun’s rays than the total amount of energy the planet’s 5.9 billion inhabitants would consume in 27 years. These days, thanks to major advances in solar technology, it’s quite common to see more and more people having solar panels installed on their homes or business locations. They’re proud and happy because they generate their own free and clean power!
Photovoltaic (PV) solar energy is a combination of two words: Photon (light), and Voltage (energy). Solar electricity is created by using Photovoltaic (PV) technology to convert sunlight into electricity. Photovoltaic systems use sunlight to power ordinary electrical equipment, for example, household appliances, computers and lighting. The photovoltaic (PV) process converts free solar energy – the most abundant energy source on the planet – directly into solar power. Note that this is not the familiar “passive” or Solar electricity thermal technology used for space heating and hot water production.
Solar electric systems are simple to operate and have no moving parts; however PV cells employ sophisticated semiconductor devices, many of which are similar to those developed in the integrated circuit industry.
A PV solar cell consists of two or more thin layers of semi-conducting material, most commonly silicon. When the silicon is exposed to light, electrical charges are generated and this can be conducted away by metal contacts as direct current (DC). The electrical output from a single cell is small, so multiple cells are connected together and encapsulated (usually behind glass) to form a module (sometimes referred to as a “panel”). The PV module is the principle building block of a PV system and any number of modules can be connected together to give the desired electrical output.
PV equipment has no moving parts and as a result requires minimal maintenance. It generates solar electricity without producing emissions of greenhouse or any other gases, and its operation is virtually silent.
Pieces and Parts
The components typically required in a grid-connected PV system are illustrated below.
The PV array consists of a number of individual photovoltaic modules connected together to give the required power with a suitable current and voltage output. Typical modules for a home have a rated power output of around 200 – 300 Watts peak (Wp) each. A typical domestic system of 4 – 5 kWp may therefore comprise some 20-25 modules covering an area of between 40 – 50 m2, depending on the technology used and the orientation of the array with respect to the sun.
Most PV modules deliver direct current (DC) electricity at 12 volts (V), whereas most common household appliances run off alternating current (AC) at 120 V. An inverter is used to convert the low voltage DC to higher voltage AC.
Other components in a typical grid connected PV system are the array mounting structure and the various cables and switches needed to ensure that the PV generator can be isolated both from the building and from the mains. Again, good suppliers and installers of grid-connect PV systems will be able to offer advice on these aspects of the PV system.
Finally, a utility meter will be required to ensure that the system owner can be credited for any PV power fed in/out to the mains supply.
How does solar electric power work?
The sun light hits the surface of the solar electric panels (1). PV stands for Photo Voltaic which means they are able to transform the sun light energy (Photo) into electrical energy (Voltaic).
The electricity generated from the solar panels flows in one direction only and we call it Direct Current or DC power. DC Power is the same type of power you will find in most cars, boats, or RV batteries. DC power is safe, easy to work with, and can be stored over long periods of time.
From the solar panels this DC power is harnessed by a device called an inverter (2). The inverter transforms the Direct Current DC power into Alternative Current or AC power which is compatible with the power we get from our utility. Most inverters have a display window to highlight the DC energy produced from the solar panels.
The energy generated is then sent as AC electricity through your main service panel (3) as well as your utility meter. This electricity is recorded by one or a combination of several methods: a wall mounted device, a separate meter, or a device that sends the information out over the internet. This energy data can be logged-in via the internet and accessed with an ID and password.
This power will be used primarily throughout the property right away. This is done through a breaker hookup into the main service panel. Any excess energy is fed back into the utility network grid (4). You neighborhood is receiving your green, clean, friendly power. As your solar electric system generates power, it has the capability to spin your utility meter backwards. So now every time there is light outside, your solar energy generating system will be generate electricity for your benefit.
