It’s been nearly a century since anyone in the U.S. has experienced anything like it: On August 21, the moon will pass between the earth and the sun, effectively blocking some or most of the sunlight that reaches the earth across a large swath of the United States. Starting above Salem, Oregon and ending above Charleston, South Carolina, this is the first eclipse in 99 years that spans the entire continent. While only lasting about two minutes in each location, the output of photovoltaic (PV) power plants across the U.S. will dramatically decrease.

Studying the Impact

The National Renewable Energy Laboratory (NREL) conducted a study of the Western Electricity Coordinating Council (WECC) territory, which covers the vast majority of the Mountain and Pacific Time zones including 14 Western states. In these areas, the eclipse will occur between 8:00 a.m. and noon. Researchers have already examined potential impacts of the eclipse on generation from power plants and rooftops. It is estimated that both sources provide the WECC with PV capacity of approximately 25 gigawatts (GW), utility scale accounting for two thirds of that. Total PV power installed across the U.S. is estimated to be over 44 GW today.

Examining the WECC as a whole, and assuming the worst case scenario—a bright and sunny day—the rolling effects of the eclipse are expected to have the biggest impact at approximately 10:30 a.m., when PV output is projected to drop 5 GW below typical generation levels. This represents the amount of energy needed to power approximately 1 million homes and, if not already anticipated, could create difficulties for portions of the grid network that use solar to meet a significant fraction of electricity demand during the day. The burden of compensating for the lost energy from solar generators will fall mostly on natural gas powered turbines, which are able to ramp up ahead of the eclipse. Hydro generation—power created from flowing water—will also help to fill the void of solar output, though conservation constraints in the West will prevent it from compensating for all of the lost generation. NREL’s modeling is expected to enable utilities to pass through this eclipse without completely disconnecting any PV, to maximize the production of solar electricity.

Preventing Future Issues

Research funded by the SunShot Initiative’s systems integration subprogram is helping to mitigate impacts of the August 21 eclipse and will continue to help utilities plan for weather events that are harder to predict. Solar forecasting technologies allow grid and solar power plant operators to predict when, where, and how much electricity will be produced—thus developing the best strategy for balancing supply and demand. SunShot funding allows NREL to conduct forecasting simulations on two large PV arrays located at a field test site near Denver. As the eclipse happens, those arrays will be monitored to verify the simulations. Denver will experience a 92% eclipse, so the impact is significant and will benefit solar producers during future eclipses.

Systems Integration

The systems integration subprogram enables the widespread deployment of secure, reliable, and cost effective solar energy on the nation’s electricity grid. Learn more

SunShot is working to develop certain energy storage solutions that are scalable, secure, reliable, and cost-effective. As more solar energy continues to be added to the grid, storage would play an important role in mitigating the intermittency of solar, which is currently not capable of meeting energy demand around the clock. These projects would enable solar generated electricity to be dispatched when and where it’s needed. Austin Energy is already beginning to integrate energy storage technology into its management tools and will soon have the capability to divert grid-connected solar to storage facilities. This work will serve as a benchmark reference for any utility to optimize its solar resources at all times.

As parts of the country prepare to experience darkness in the middle of the day, the SunShot Initiative is doing its part to help develop a more reliable and resilient electric grid, regardless of the time of day.

Learn more about SunShot’s resources on the eclipse and visit NASA’s eclipse website.

Office of Energy Efficiency & Renewable Energy

August 9, 2017

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Home » Solar Power Does What? 4 Unusual Uses of Photovoltaic Technology

It’s becoming more common to find solar panels on rooftops, but that’s just one of thousands of places where they are generating power. As costs drop and energy production rises, we expect to see many more places where solar technologies are put to work—providing unleashed, inexpensive electricity.

Here are four unusual places where solar technologies are being used today:

Windows that incorporate photovoltaic cells are being developed by SunShot awardee Next Energy Technologies to increase the energy efficiency of commercial buildings. 

Paul Wellman/Next Energy Technologies

Solar Windows

New solar electric window technologies allow visible light to shine through glass panels while simultaneously collecting the invisible rays contained in sunlight and transforming them into electricity. These applications are still exploratory, but one company is working with SunShot to make the technology practical across large sheets of glass, so the windows of commercial buildings can serve dual purposes.

This ARCO Solar Sunroof was marketed to vehicle manufacturers and aftermarket suppliers in the 1980s as a way to optimize air conditioner capacity. 

ARCO Solar

Solar-Powered Car Surfaces

While there are solar-powered charging stations for electric vehicles in numerous U.S. cities, solar technology is making its way directly into the body of some cars. The 2010 Toyota Prius featured a solar panel on its roof, but the generated electricity only helped to power the car’s climate control system. An updated version of the same car, now being manufactured in Japan, connects the solar panel directly to the car’s battery, increasing the efficiency and reliability of the electrical system. This is a far leap from the first semi-transparent solar sunroof technology developed in the 1980s that augmented the car’s ventilation.

Solar vaccine refrigeration has come a long way—much more efficient configurations are available that are easier to transport and also make ice. 

NESTE Advanced Power Systems

Vaccine Refrigerators

In developing countries, 24-hour electricity isn’t guaranteed, and in many cases, there is no electrical grid. In places with a grid, the infrastructure is often so poor that chronic power outages occur daily. Private companies have been manufacturing solar-powered vaccine refrigerators so healthcare workers in remote areas can administer critical medication to those who need it. This technology solution has been saving lives for more than four decades.

Sunlight can make streetlights function in the evening, and in some cities, internet-linked cameras and sensors already allow them to do even more. 

Robert Ashworth

Smart Solar Cities

Solar-powered streetlights are currently used all across urban areas. The sun charges a battery during the day so streetlights, now primarily utilizing light-emitting diodes (LEDs), can shine at night. Some cities, like San Diego, California, are using streetlights to optimize infrastructure. The Smart City San Diego Initiative is incorporating smart sensors into streetlights that have the ability to direct drivers to open parking spaces and help first responders during emergencies. Combining internet-linked sensors with solar powered streetlights saves both time and money.

Learn more about the SunShot Initiative’s photovoltaic research and development.

Photo of Charlie Gay, Solar Energy Technologies Office Director
Charlie Gay

Dr. Charlie Gay is the Solar Energy Technologies Office Director for the Office of Energy Efficiency and Renewable Energy (EERE) of the U.S. Department of Energy (DOE).

What’s the difference between the installed capacity and electricity generation of energy sources?

It’s a good question and one that’s commonly misunderstood.

In the energy world, these two terms are often used to describe the growth of energy resources in the United States.

Take wind or solar, for example.

According to the EIA, around 1% of U.S. electricity generation came from solar energy in 2016.


There might be an article about wind making up 8% of all energy generation capacity. Or, that solar will make up 1% of electricity generation in a specific year.

So what’s the difference? Let’s break it down for you.

What is Capacity?

The U.S. Energy Information Administration (EIA) refers to capacity as the maximum output of electricity that a generator can produce under ideal conditions. Capacity levels are normally determined as a result of performance tests and allow utilities to project the maximum electricity load that a generator can support. Capacity is generally measured in megawatts or kilowatts.

Let’s look at an example.

According to EIA, wind turbines accounted for 8% of U.S. installed electricity generation “capacity,” as of December 2016. This means under ideal conditions, utilities would be able to supply 8% of the country’s electricity needs with wind power, but this won’t necessarily be the actual amount of electricity produced.

According to EIA, wind turbines accounted for 8% of U.S. installed electricity generation capacity as of December 2016.


What is Generation?

Electricity generation, on the other hand, refers to the amount of electricity that IS produced over a specific period of time. This is usually measured in kilowatt-hours, megawatt-hours, or terawatt-hours (1 terawatt equals 1 million megawatts). To understand the unit of megawatt-hours (MWh), consider a wind turbine with a capacity of 1.5 megawatts that is running at its maximum capacity for 2 hours. In this scenario, at the end of the second hour, the turbine would have generated 3 megawatt-hours of energy (i.e. 1.5 megawatts X 2 hours).

If the wind was not blowing strongly enough for the turbine to operate at its maximum capacity, and the same turbine was only producing 1 megawatt of power for 2 hours, the total energy generation would be 2 megawatt-hours (i.e. 1 megawatt X 2 hours). This simple thought exercise demonstrates how calculations of generation take into account the fact that not all generation sources are operating at their maximum capacity at all times, such as when the sun isn't shining or when the wind isn't blowing.

Where Can I Learn More?

The EIA has a roster of Frequently Asked Questions on electricity usage and every other energy topic under the sun.

Learn more about recent advancements in wind energy and solar energy.

Inkjet-printed perovskite solar cells with efficiency above 16%.

Dr. Maikel van Hest, National Renewable Energy Laboratory

Did you know there are alternatives to standard silicon solar panels? Or that someday soon, you might be able install a solar panel that is 50% more efficient than the average silicon photovoltaic (PV) solar panel?

That’s exactly what Iris Photovoltaics, Inc. (Iris PV) is aiming to produce. The Berkeley, California-based company is working to modernize how silicon solar panels are manufactured. In addition, they are attempting to increase the efficiency of PVs to a range of 25-30%.

The U.S. Department of Energy (DOE) Small Business Vouchers (SBV) program award recipient’s technology adds a crystalline metal-halide perovskite layer to coat standard silicon solar panels, which produces additional electricity from infrared light. This is then layered on top of traditional silicon solar cells to create a “tandem” solar panel. These “tandem” solar panels, composed of two materials instead of one, generate a greater amount of electricity per panel.

From Manufacturing Floor to Rooftops

Iris PV is receiving technical assistance from researchers at the National Renewable Energy Laboratory (NREL) through SBV as part of DOE’s Office of Energy Efficiency and Renewable Energy Technology-to-Market program. Iris PV cofounders Colin Bailie and Chris Eberspacher are working with NREL researchers to manufacture the technology at scale and accelerate the adoption of solar with their high-efficiency PV products.

“Through the SBV program, we are addressing critical manufacturing challenges so that production facilities can be built,” said Bailie.

“Commodity silicon solar cells are mired in the 18-22% efficiency range. The theoretical maximum for combining two solar cell materials is 46% efficiency, though we’re aiming to fly a little less close to the sun and hit 30-35% efficiency.”

Compared to today’s standard solar panel, Iris PV’s design minimizes costs for manufacturers and is compatible with most existing PV technologies. It could also save individual homeowners thousands of dollars in upfront costs and utility bills compared to current technology. Once this technology is commercially available, we hope to get an enthusiastic response from both solar installers and homeowners,” said Bailie.

Overcoming Manufacturing Challenges

Today’s metal-halide perovskite solar cells have manufacturing limitations. Specific manufacturing techniques, such as spin-coating, limit the size of individual glass panels. The spin-coating process deposits thin layers of solvents or coating materials, like silicon wafers, using centrifugal force. This process also requires additional patterning in solar cell production, adding to overhead costs.

With the technical assistance of NREL’s researchers, Iris PV is overcoming these limitations using inkjet printing. Inkjet printing can uniformly coat large areas and complete patterns by dispensing single drops with controlled print design. Because inkjet printers are more precise than spin-coaters, the production process is more efficient and uniform.

According to Iris PV, inkjet printing allows for rapid prototyping and low-cost custom products down the road, including the Iris PV form factor. To date, the project has printed single-junction perovskite cells with efficiencies of more than 16%, on par with devices made using other scalable technologies. And another benefit to Iris PV’s tandem panel design: Because it will be compatible with existing manufacturing tools and methods, costs for current solar manufacturers to switch technologies will be minimal.

Iris PV’s next step is to demonstrate the technology’s scalability. If they are able to print perovskite films on a 6” x 6” area, the demonstration will be considered a success.

As for Bailie and Eberspacher, their team especially valued the support of NREL researchers who helped through the SBV program--Maikel van Hest, Rosie Bramante, and James Whitaker.

“The development of inkjet-printed perovskite photovoltaics would not have been possible without the support provided by the Department of Energy’s Small Business Vouchers program,” said Bailie.


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