Solar Power Beyond The Rooftop: Moving To Utility-Scale

Utility-scale solar power covers a lot of ground, in terms of size of installation (from tens of megawatts to hundreds, and even plans, yet to be realized, for gigawatt-sized power plants), and in terms of technology (there’s a world of difference between photovoltaics and concentrating solar power). But no matter how you choose to look at it, 2012 was a pretty stellar year.

For the first time, global solar power passed the 100 GW mark, with 30 GW added last year alone. Perspective on that growth: In 2010, global solar power capacity was nearly 40 GW. So, in just the past two years solar power has more than doubled.

More detail about those installations, on both the international level and in the United States, in a bit. But first, so that everyone’s on the same page in terms of the technology, let’s talk about the different ways to produce electricity from the sun.

Solar Power in Acronyms: PV versus CSP versus CPV

The majority of solar power installed uses photovoltaics. This is what most people think of when you talk about solar power, solar panels. Without getting too technical, a solar panel consists of multiple solar cells made of photovoltaic material, converting solar radiation into direct current electricity.

Silicon is the most common material used for solar cells, but other materials can also be used. Over the past three years, the price of silicon has dropped precipitously, with prices per kilogram now sitting under $20, as of the end of 2012.

Photovoltaics have a major advantage: They are easily scalable, modular — meaning that they can expand from a couple kilowatts, to megawatts, all the way to hundreds of megawatts.

The other solar power technology is concentrating (or concentrated) solar power — sometimes these are called solar thermal power plants. Here some sort of mirror system focuses sunlight onto either a central tower or decentralized tubes containing a liquid. That liquid becomes heated, turning to steam, which then turns a turbine.

It’s the same basic principle that a coal, a natural gas, or even a nuclear power plant operates on: Steam is generated, a turbine turns, creating electricity. But in concentrating solar power plants, the heat creating the steam comes from the limitless power supply of the sun. There are several different set-ups for doing this: The aforementioned mirrors focusing the sun onto a central tower (that’s the photo on the next page), parabolic mirrors focusing the sun onto a trough, fresnel reflectors, dish sterling systems.

It’s often this technology that powers the world’s largest solar installations, from the 354 MW Solar Energy Generating System in California (which consists of nine separate power plants), to the current record holder for largest single plant, a 100 MW installation in Abu Dhabi. There are a number of larger plants proposed though, including a 500 MW one in California that’s expected to come online in 2016.

From his home in New York City, Mat McDermott writes about energy and resource consumption, environmental ethics, climate change, issues of animal welfare and animal consciousness, and the response of religious communities to environmental problems. He was editor of business, politics, and energy content for TreeHugger.com from 2008 though 2012. Beyond writing, Mat is an Advisor for The Bhumi Project, a Hindu environmental organization based in the UK, affiliated with the Oxford Centre for Hindu Studies and the Alliance of Religions and Conservation. Follow him on Facebook and Twitter.