EME 812
Utility Solar Power and Concentration

1.3 Utility Scale Power


1.3 Utility Scale Power

There are two main solar technologies that are being considered for large scale power generation: (1) Photovoltacs (PV) and (2) Concentrating Solar Power (CSP). Another type - concentrating photovoltaic (CPV) is currently not a major player, but there are a few large facilities that use CPV technology. PV and CSP are pricipally different in the type of energy conversion and type of solar resource they rely on. We are going to review the basics of those technologies and their current state in energy market in this lesson before considering more technical details further on.

Photovoltaics (PV)

Reading Assignment

So, what do we mean by the Utility-Scale Solar Power?

Please read the introduction on the website of the Solar Energy Industries Association (SEIA) and watch the video below to get the basic idea about utility-scale photovoltaic systems.

Click for a transcript

PRESENTER: All right, we all know that the sun's energy creates heat and light. But it can also be converted to make electricity and lots of it. One technology is called solar photovoltaics, or PV for short. You've probably seen PV panels around for years. But recent advancements have greatly improved their efficiency and electrical output. Enough energy from the sun hits the Earth every hour to power the planet for an entire year.

Here's how it works. You see, sunlight is made up of tiny packets of energy called photons. These photons radiate out from the sun. And about 93 million miles later, they collide with a semiconductor on a solar panel here on Earth. It all happens at the speed of light. Take a closer look, and you can see the panel is made up of several individual cells, each with a positive and a negative layer-- which create an electric field. It works something like a battery.

So the photons strike the cell, and their energy frees some electrons in the semiconductor material. The electrons create an electric current, which is harnessed by wires connected to the positive and negative sides of the cell. The electricity created is multiplied by the number of cells in each panel and the number of panels in each solar array. Combined, a solar array can make a lot of electricity for your home or business. This rooftop solar array powers this home. And the array on top of this warehouse creates enough electricity for about 1,000 homes.

OK, there are some obvious advantages to Solar PV technology. It produces clean energy. It has no emissions, no moving parts. It doesn't make any noise, and it doesn't need water or fossil fuels to produce power. And it can be located right where the power is needed, in the middle of nowhere, or it can be tied into the power grid. Solar PV is growing fast. And it can play a big role in America's clean energy economy-- anywhere the sun shines.

Understanding the limitations in efficiency of solar energy conversion and taking into account the demands of centralized power generation, the technology scale-up is one of the important issues being developed by the government agencies in order to build sustainable energy future.

Obviously, there is a strong push for large-scale systems from the government and industry. But, along with the promise, the scale-up process brings new challenges to the energy conversion system design. Some of those challenges are:

  • lower than desired efficiency (theoretical limits suggest it can be much higher);
  • high up-front cost of materials and equipment;
  • energy storage (electricity or heat);
  • power distribution and transmission.

All these issues deserve more attention and will be covered in more detail in further lessons of this course. In this lesson, we are not yet digging into any technical details of the considered technologies but, rather, taking a plunge into the context.

The following materials will give you an idea of the current state of utlility scale solar market in the US.

Reading Assignment

Industry Report: U.S. SOLAR MARKET INSIGHT, 2018 year in review, Executive summary, SEIA, Wood Mackenzie Power and Renewables, Published March 2019. (You can access the executive summary of the Report in this Lesson).

The SEIA 2018 Market Report provides a general outlook of the role of PV solar technology at the scale of national energy development. In the year of 2018, additional 10.6 GW (DC) of PV capacity was installed, again showing continuing penetration of solar into the national energy market. Residential solar market grew by 7% in 2018, at the same time, from the reported data, we can observe the tug-of-war situation between photovoltaic and natural gas utility plants, which resulted in some contraction of utility scale solar share, which might also be due to uncertainties associated with solar tarifs.

In more detail, photovoltaic technologies will be studied in Lessons 4-6.

Cencentrating Solar Power (CSP)

The other prominent technology developed on the utility scale in the US and worldwide is Concentrating Solar Power (CSP). While CSP is currently outpaced by PV on the global and domestic market, this technology may be advantageous in the areas with high annual insolation.

Watch this 2-min video to overview the utility-scale Concentrating Solar Power (CSP) systems:

Click for a transcript

Ok Take the natural heat from the sun, reflect it against a mirror, focus all of that heat on one area, send it through a power system, and you've got a renewable way of making electricity.

It's called concentrating solar power, or CSP. Now, there are many types of CSP technologies. Towers, dishes, linear mirrors, and troughs. Have a look at this parabolic trough system. Parabolic troughs are large mirrors shaped like a giant "U." These troughs are connected together in long lines and will track the sun throughout the day. When the sun's heat is reflected off the mirror, the curved shape sends most of that reflected heat onto a receiver. The receiver tube is filled with a fluid. It could be oil, molten salt, something that holds the heat well. Basically, this super-hot liquid heats water in this thing called a heat exchanger, and the water turns to steam. Now, the steam is sent off to a turbine, and from there, it's business as usual inside a power plant. A steam turbine spins a generator and the generator makes electricity. Once the fluid transfers its heat, it's recycled and used over and over. And the steam is also cooled, condensed, and recycled again and again.

One big advantage of these trough systems is that the heated fluid can be stored and used later to keep making electricity when the sun isn't shining. Sunny skies and hot temperatures make the southwest U.S. an ideal place for these kinds of power plants. Many concentrated solar power plants could be built within the next several years. And a single plant can generate 250 megawatts or more, which is enough to power about 90,000 homes. That's a lot of electricity to meet America's power needs

Reading Assignment

Web article: 2018: The Year Sees Explosive Expansion of Concentrated Solar Power Capacity Globally, HELI SCSP, Accessed: April 2019.

While PV system significantly outpaced CSP in growth over the past decade, there is still a significant economic potential for converting solar thermal energy into power in a number of locations around the globe.  

I hope these materials give you a clear idea what kind of systems will be the subject for learning in this course. The following self-check questions allow you to iterate the basics once more before we move ahead.

Check Your Understanding - Essay Question 9

List the key technologies that have been involved in utility scale solar power generation:

Check Your Understanding - Essay Question 10

How is the utility scale power different from the distributed generation power?

Check Your Understanding - Essay Question 11

What were the top-3 ranked states for installing PV solar energy systems?