Green electrons go solar

By Jeanne Erdmann

The first thing Howard Barikmo will tell you about solar panels is to please call them something else. Call them solar modules. Call them photovoltaic energy systems. Just don’t call them panels. The "p-word" just reminds people that solar energy had a rough start.

Howard Barikmo has
spent much of his professional
life developing solar power

In the 1980s, in Arizona, Barikmo’s home state, most of the solar systems placed on roofs were thermal panels for heating water. But the manufacturers didn’t take into account the occasional frosty morning in the Phoenix area. There was no freeze protection in the panels; pipes broke, spilling water and upsetting homeowners.

"A bad name was given to solar industry," Barikmo says.

Then, the PV (photovoltaics) industry was in its infancy. It wanted to distance itself from the term “solar panel” by calling its products solar modules or PV.
 
Dedicated to developing solar power, Barikmo and others persevered. Over the past 30 years or so, Barikmo, an electrical engineer, has worked in many areas of the solar industry. He began in 1981 with Photocomm, Inc. of Scottsdale, Arizona, as a systems design engineer. In 1997, he joined the ASU (Arizona State University) Photovoltaic Testing Laboratory, which then had the only testing lab devoted to photovoltaics in North America. At the time, PV manufacturers in the United States of America liked to use the ASU lab because it was cheaper and faster for them than going to either of the two European labs. Most tests done by ASU’s lab were carried out either to International IEC Standards or regional UL (Underwriters Laboratories) standards.

In 2003, Barikmo left Arizona State and joined IEC TC (Technical Committee) 82: Solar photovoltaic energy systems, as Secretary. Today, he is happy to see solar power take its rightful place among wind, tides and other green energies. "Anything we can do to displace the black electrons from coal generation plants, I say, do it," he says.

A boost from tariffs

Others share that viewpoint. The growth of photovoltaics has rocketed since 2000. The Japanese began the growth, but more recently Barikmo credits European FITs (feed-in tariffs) for giving photovoltaic energy the biggest support. FITs boost the industry because governments pay an above-market price over a given time to consumers of renewable energy sources. The faster people adopt these technologies, the faster investments are recouped.

Solar power takes its rightful place among
wind, tides and other green energies

These tariffs are gaining ground worldwide. In Germany, for instance, the government paid a homeowner or farmer generating one or two megawatts around 0,59 € per kilowatt-hour. "It’s lower now for someone who is just hooking into the German grid, but it’s still a good investment," Barikmo says.

Concentrating on reflectors

TC 82 is responding to the worldwide demand for solar energy by writing standards for PV technology. It has written IEC 62108, Concentrator photovoltaic (CPV) modules and assemblies - Design qualification and type approval, a design qualification standard for solar concentrators. Concentrating solar energy onto a solar cell offers one way to make PV systems less expensive. Concentrators may use a solar parabolic reflector to concentrate the sun’s energy onto a semiconductor – just like using a magnifying glass to concentrate the sun’s rays into one pinpoint. Reflectors concentrate the direct incoming rays and increase the solar cell output. A 10x magnifier, for instance, concentrates by 10 times.

"Concentrator systems work very well in areas of the world where there is plenty of direct sunlight, such as the southwestern deserts of the United States, the Sahara of Africa, the Gobi of Asia and many other places,” Barikmo says. “Things concentrator systems don’t like are clouds – simply because they hide the sun and don’t give the required direct rays from the sun. Some manufacturers suggest their systems can generate their green electrons at less cost than flat-plate PV modules."

There are a few challenges. For most concentrator systems, designers need a precise means of tracking the sun from sunrise to sunset. With higher concentrations, say 1 000 times, the tracking system needs accuracy and stability, and materials need to withstand extra heat.

Storage and efficiency

The industry still needs an economical way of storing electrical energy generated during the day for use from late afternoon until, say, midnight. In any solar system – PV or thermal – energy storage would provide utilities with a dependable energy source for customers on their grids. Even though this is proving to be a challenge, efforts are directed this way. "Customers won’t excuse the power companies for long if the AC (alternating current) to their wall sockets goes off between sunset and sunrise," Barikmo says.

The oldest and most prevalent technology is crystalline silicon. Flat plates of this material convert 15-20 % of the sun’s energy. With 1 000 watts per square meter of solar energy illuminating one square meter (on a good, sunny day), a PV module that is 20 % efficient would convert a maximum of 200 watts into electricity. Another technology uses thin film amorphous silicon, which costs less than crystalline but converts at 9 % under the best circumstances. Cadmium telluride is another very promising thin-film material with 10-12 % conversion efficiencies and manufacturing costs of perhaps half that of crystalline silicon.

Bringing designs to consumers

In sunny Arizona testing can be
done outdoors

Before manufacturers bring a new PV module design to market, they normally submit the module to a recognized testing lab. The advantage of using a lab in Arizona, for instance, is that testing can be done in the sunny outdoors. Flash tests using sun simulators are done in laboratories where the sun doesn’t shine every day, or in factories making PV modules to cut down on production costs. The simulator output exposes the module for less than a second to light from an artificial source. Then an electronic device gives the current-voltage characteristics of the module versus load at full sun (the 1 000 watts per square-meter figure). The standard ensures that the simulator provides a reasonable spectrum that looks almost like the sun beating down and that is repeatable in other simulators used at other labs or factories. "We need to make certain the standards we write can be used for testing PV modules all over the world and come out with close to identical results," Barikmo says.

Manufacturers submit designs to labs for qualification testing and design approval as per TC 82’s two flat-plate performance standards IEC 61215 and IEC 61646, or IEC 62108 for concentrator systems. If the module passes the testing regime, manufacturers get a certificate and can then go to customers and say the design was approved. Europe requires modules to obtain either 61215 or 61646 certifications before they can become part of the generation capacity for FITs.

"The two flat-plate standards are embraced by manufacturers as a Bible,” Barikmo says. “If the module has been tested to these standards, and they’ve passed, the customer can be relatively assured that if they put these modules on their roof then it should be a good system."

In the USA, modules need to pass UL 1703. Although this is a safety standard, Barikmo says the tests are almost identical. TC 82 has written IEC 61730, also a safety standard. Worldwide, IEC NCs (National Committees) are working to have this standard accepted as their national safety standard for PV systems. The USA is in the process of approving it, with a few national exceptions.

Photovoltaics need safety standards because if things go wrong, modules can burn and shock people. With voltages upwards of 1 000 V in some systems, proper grounding, insulation and integrity are critical. If module materials degrade over time, shock hazards may crop up. If things go really wrong the module can catch fire. "That’s a no-no," Barikmo says.

The efforts of TC 82 will ensure that PV systems join the energy grid in a secure, efficient and effective way. "TC 82’s existence is to be sure that the green electrons being generated by PV systems can join the world’s energy mix and provide the planet with a sustainable future: safely, dependably and inexpensively,” says Barikmo.