IN THIS PART …
Understanding the fundamentals of photovoltaic (PV) systems is the key to designing and installing high-quality systems that’ll perform beyond your (and your clients’) expectations. That’s why this part provides the foundation you need to move forward with designing and installing PV systems.
Chapter 1 gives you an understanding of where PV systems started, where they are now, and where they’re headed; Chapter 2 gives you a feel for the major components used in all types of PV systems and how they relate to each other. Chapter 3 provides an overview of the electrical fundamentals that drive system designs and installations, and Chapter 4 outlines the relationship between the sun and the earth and guides you on assessing the solar resource. Rounding out the bunch, Chapter 5 walks you through the process of selecting where on a client’s property to install a PV system; it also helps you quantify the solar resource at a particular location.
Peeking into the Past, Present, and Future of PV Installations
To truly appreciate PV, it helps to have an understanding of where the technology came from, where it’s at now, and where it’s going.
The operating principles for modern PV cells were first discovered in 1839 by a French physicist named A.E. Becquerel. After that, a number of scientists played with and improved on Becquerel’s original discovery. In the 1950s, Bell Labs created the first piece of PV technology designed for use in space. This technology soon found its way back down to earth for use in telecommunications applications in remote areas. In the 1970s and 1980s, people began using PV modules to charge batteries and then used those batteries to run various lights and appliances in their remote homes. These early PV pioneers helped set the stage for today’s PV industry.
The first PV cells weren’t very efficient or widely used outside of space programs. They were also quite costly. Yet over the years, researchers and manufacturing companies increased efficiencies and reliability and managed to drive down costs drastically. All of these contributions have led to the widespread use of solar modules and their availability to you and me. In the following sections, I describe some common PV applications, a few brief pros and cons of PV systems, and the future of the PV industry.
Acquainting yourself with typical PV applications
Modern PV systems can be found in a wide variety of applications. They power calculators, pump water, help offset the energy used by floodlights along highways, and, of course, power homes and businesses.
For you and me, electricity is available nearly everywhere we go, and PV systems are able to integrate with the existing utility grid. In remote, developing areas, PV systems provide valuable energy for powering lighting systems, running refrigerators, and helping deliver clean drinking water.
Checking out PV pros and cons
PV systems have some serious advantages on their side. Producing electricity from the sun has environmental benefits because the power source is an abundant renewable resource that’s available every day (even though PV systems aren’t as effective during cloudy weather, they still produce a small amount of power on those days). PV is also a highly adaptable power source. You can use individual cells to power small electronics and individual panels to power specific loads. You can build small arrays to power homes, or you can build utility-scale projects to send massive amounts of power into the utility grid. And after PV systems are installed, they can provide many years of clean, reliable power at virtually any location on earth.
On homes and businesses connected to the utility, PV systems are considered distributed generation, a power source that produces electricity close to the location where the power is used. They’re able to offset the requirements on the central power plants sending out the electricity most people use.
PV systems aren’t the right answer for all applications. They have some disadvantages too. For example:
- The sun isn’t a continuous power source. At night, the PV modules can’t produce power, so in some scenarios, you have to use a method to store the energy for later use (adding cost and complexity to the system design and installation).
- The amount of area required to produce power is large in comparison to other sources of power. For large-scale projects, significant portions of land or roof space are necessary. Not every homeowner or business owner has access to such space.
Looking into the future of PV
Most people accept that “alternatives” to the “conventional” power sources acquired by burning fossil fuels must be developed, and so, to use a really bad pun, the solar industry has a bright future ahead of it. The worldwide demand for solar electricity continues to grow on a global level, and the amount of time, effort, and money being put into the industry is amazing. Many research and development projects are underway that will help drive down costs further, increase efficiency, and deliver better PV systems.
I’m reluctant to make any bold predictions about the future of PV technology; ideas I had just a few years ago that I wrote off as too far-fetched and nearly impossible are proving to be real solutions in the PV industry. However, I am comfortable saying that the overall acceptance of PV systems and their integration into the built environment will do nothing but increase in the years to come. Solar power is no silver bullet, though. It’ll take a movement on many fronts to make the global shift away from over-reliance on fossil fuels.
Introducing PV Components and Systems
PV systems can be ridiculously simple (connect a module to a load and use the load as you wish), but they can also seem overwhelming when you first look at them. Every time I go to design and install a PV system, I look at the whole process as a real-life puzzle that must be arranged and put together just so. Each project is unique in its own way, and that’s part of the fun.
Yet despite the differences in the details, the PV systems you connect to homes and small businesses have some specific and very necessary components (all of which have an important role to play in the system).
- PV modules: The individual units that you place in the sun to produce electricity from the sun are called PV modules. A number of modules connected together in different configurations form a PV array.
- Battery bank: Batteries provide a way of storing the energy produced by the PV array. Individual batteries connected together make up a PV system’s battery bank.
- Inverters: Devices that take power from the PV array or the battery bank and turn it into AC power used to operate loads are inverters.
- Disconnects and overcurrent protection: These components are necessary for ensuring the safety of the system and the people who come into contact with it.
Grid-direct PV systems, which send power back to the utility grid, have become the most popular type of PV system at locations where the utility grid is present. They offer increased ...