Shining more light on solar panels

Improving low concentration photovoltaics

Thermal radiation readings on panels help Joshua Pearce and his research team better understand ways to improve low-concentration photovoltaic systems.
Credit: Joshua Pearce, Michigan Tech

Solar panels are the beacon of renewable energy, yet they are not getting as much light as they could be. Joshua Pearce from Michigan Technological University and a team from Queen's University in Canada have found a way to get more sun to shine on the panels and crank up the output by 30 percent or more.

"We expend a lot of blood, sweat and tears to make solar panels as efficient as possible," Pearce says. "We work so hard to get a fraction of a percent increase on the module level; double digit returns on the systems level was relatively easy."

Such a large increase of efficiency at the system level then could greatly change how solar panels are installed, and with the economic payback, it could even mean major retrofits for existing solar farms.

"We're looking at this from a systems perspective," Pearce says, who is an associate professor of materials science and engineering and electrical and computing engineering. He explains that the research focused on the system rather than individual panels mostly because the current set up for ground-mounted solar panel arrays is "wasting space."

The iconic flat-faced solar panels installed in large-scale utility solar farms are spaced apart to prevent shading. As the sun shines on a photovoltaic system, sending electricity into the grid, a fair amount of that potential energy is lost as the light hits the ground between rows of panels. The solution is simple, says Pearce: Fill the space with a reflector to bounce sunlight back onto the panels and use the light-reflecting mathematical models of videogames and action movies to avoid temperature swings.

Source by: http://www.sciencedaily.com/releases/2015/10/151022141718.htm

‘World’s Most Efficient Rooftop Solar Panel’ Revisited

World-record claims of this nature, absent actual distribution, yield and volume data, are mostly bluster and stunt specmanship.

by Eric Wesoff 
October 13, 2015

Earlier this month, SolarCity made the claim that solar panels coming off of its 100-megawatt Silevo pilot production line were setting world records for solar module efficiency as "the world’s most efficient rooftop solar panel, with a module efficiency exceeding 22 percent." A week later, Panasonic claimed the crown at 22.5 percent module efficiency.

A chart might help clear things up.

SolarCity’s panel was measured with 22.04 percent module-level efficiency by the Renewable Energy Test Center. The silicon-based bifacial PV cell combines n-type substrates, copper electrodes, thin-film passivation layers, and a tunneling oxide layer that yields high conversion efficiencies.

SolarCity claims that its module will be "the highest-volume solar panel manufactured in the Western Hemisphere." Production will begin this month at the firm's 100-megawatt pilot facility, but most of the new solar panels will be produced at SolarCity’s 1-gigawatt factory in upstate New York. Full production will be between 9,000 and 10,000 solar panels per day when the Buffalo facility hits full capacity.

SolarCity CTO Peter Rive noted that the record panel was manufactured on the company's 100-megawatt pilot production line -- the Buffalo factory won't be at full production until 2017. Rive acknowledged that the 22 percent panel is "on the high end," but also noted that a majority of panels are hitting 21.8 percent.

SunPower claims its X-Series panels are the "most efficient panel on the market today" with an efficiency of 21.5 percent. The company also says demand for its X-Series product is "extremely high," with "manufacturing volume [set] to increase more than 300 percent year-over-year." Average cell efficiency across all SunPower lines was close to 23 percent during the quarter, according to the company. A reliable source at SunPower told GTM that 22 percent efficiency panels were already coming off of its line.

A SunPower spokesperson added, "As a company that is leading in providing customers around the globe with the world’s most efficient solar panels, SunPower always welcomes others to the efficiency race. It’s great that we all agree -- efficiency matters. We’re proud that we’ve been shipping the industry’s highest-efficiency solar panels for years, and some of our customers are receiving panels with greater than 22 percent efficiency."

A source suggests that there are enough SunPower panels at the factory with greater than 22 percent efficiency to build a 10-kilowatt system, starting with panel serial number J19M20279602.

Panasonic: As covered in PV Magazine, the Panasonic panel’s 22.5 percent conversion efficiency was verified by Japan’s National Institute of Advanced Industrial Science and Technology "and builds upon the 25.6% efficiency record the company set in 2014 at cell level."

World-record claims of this nature, absent actual distribution, yield and volume data, are mostly bluster and stunt specmanship.

An anonymous source suggested, "In solar, cost is king. Energy is a commodity, after all. With [balance-of-systems] costs declining, efficiency has less leverage on total system cost."

In any case, SolarCity's pilot production line holds the title for now.

source by:https://www.greentechmedia.com/articles/read/Worlds-Most-Efficient-Rooftop-Solar-Panel-Revisited

Solar panels on a garage near a house in Marshfield.

By Lorne Bell

Across the state, solar company sales representatives are marching door to door, offering installation contracts that seem hard to refuse: solar panels for no money down, with no maintenance, and electricity at prices significantly below those of utilities.

So, is it a good deal?

These contracts are known as power purchase agreements and they are largely responsible for the boom in residential solar panels here and across the country. Of the 189,000 residential solar units installed in the United States last year, more than 70 percent were power purchase agreements, according to Cory Honeyman, senior analyst with Boston-based GTM Research, which provides data and consulting for the green tech industry.

Power purchase agreements offer an alternative to buying and installing residential solar panels, which cost about $21,000 for a typical 6,000-killowatt-hour system, according to GTM. Instead, solar companies purchase, install, and maintain panels on customers’ homes at no cost for a contractual period of 20 to 25 years.

In return, homeowners pay the solar company for the energy produced by the panels, usually at discounts up to 25 percent lower than utility rates. The contracts also fix annual rate increases to offer predictability in the erratic energy market.

Residential solar systems can produce anywhere from 40 to 95 percent of a home’s electricity, and they can lower overall electric costs by 10 to 20 percent, says Jonathan Bass, spokesman for SolarCity Corp. of San Mateo, Calif., the nation’s biggest residential solar company. SolarCity has about 15,000 customers in Massachusetts.

For homeowners who cannot afford or do not want to pay the upfront costs of solar panels, power purchase agreements offer immediate savings and cleaner energy. Still, said Honeyman, consumers should carefully weigh their options.

“There is a lot of fine print in those contracts,” he said, “and there are important risks and considerations to keep in mind.”

The first consideration is the 20- to 25-year contract. That commitment means that if a homeowner sells his home, he must buy out the remaining years or transfer the contract to the new owner.

The balance owed when a contract ends early is based on projected solar electricity rates, average usage, and remaining time on the contract. In a typical contract charging 13 cents per kilowatt hour, for a typical home consumer 6,000 kilowatt hours a year, buying out the last 10 years could cost more than $8,000.

Solar companies say that in nearly all cases — SolarCity estimates 98 percent — homeowners transfer their contracts to the buyers.

Another consideration: the falling price of solar panels could make buying a solar power system more attractive than a power purchase agreement. The average cost to install residential solar power has plunged 73 percent since 2006, according to the Solar Energy Industries Association, a Washington trade group, and those costs are expected to decline further.

For those who can afford to buy or finance solar panels outright, owning a system can provide additional financial benefits. For one, instead of paying a solar company for the electricity produced on the homeowner’s roof, that energy is free.

Owning the panels also allows residents to reap state and federal tax credits and other incentives, which under purchase agreements, go to the solar companies. A typical $20,000, 6,000-kilowatt-hour system could generate $1,200 to $1,800 annually through the incentives — enough to cover the cost of loan payments, said Josh Mailloux, sales manager at Boston Solar of Woburn, which installed nearly 800 residential systems in Massachusetts last year. Most were purchased by homeowners.

“It’d be nice if people had some idea of what they’re giving up” with power purchase agreements, Mailloux said.

As panel prices slide, analysts expect the market share of power purchase agreements to shrink and more homeowners buy systems outright. SolarCity, which has relied almost exclusively on these agreements, recently added a loan program, called MyPower, to finance residential purchases.

Whether homeowners buy panels or enter a power purchase agreement, residential solar could face a challenge in 2017, when the 30 percent federal investment tax credit is set to expire for homeowners and fall to 10 percent for solar companies. Analysts expect residential solar installations to accelerate over the next two years as homeowners and solar companies seek to take advantage of the program before it expires.

Congress could extend the tax credits. But if lawmakers don’t, the pace of solar installations will slow, analysts said. For the time being, said Honeyman, power purchase agreements still offer a good deal for many low- and middle-income homeowners who can’t afford the upfront costs or don’t want the maintenance and other hassles of ownership.

“The case for [power purchase agreements] is still viable,” he said. “In the end, there are meaningful savings opportunities.”