Testing the Limits of Solar Power

The company sold devices with a total capacity of 120 MW in 2006, and last year this number rose to 188 MW. In 2008 Sputnik plans to sell inverters with a total capacity of 275 MW.

“In Port we have an industry building with a surface area of 1,800 square meters. The largest part will be used for manufacturing central inverters and components for data communication. In this year we want to produce the seven-thousandth central inverter,” said Michel Castelletti, production manager for Sputnik.

The company is providing its inverters for two projects that are involved in testing the physical limits of solar energy technology.

In the Swiss Alps, the research station at Jungfraujoch is 3,500 meters above sea level. It offers researchers from all over Europe the opportunity to conduct scientific experiments at high altitudes. Currently, physicians from the University of Munich are researching the practical treatment of high altitude pulmonary edema, the Swiss Confederation is monitoring radioactivity in the air and scientists from the Belgian Institute for Atmospheric Research are investigating the chemical composition of the atmosphere.

Since January 11, 2008 the world's highest solar power plant has been helping to power this research. Swiss company sol-E Suisse AG integrated 82 square meters of solar modules into the facade of the research station. By 2009 the company plans to build two or three more systems on other parts of the station. When complete, the system will have an output of approximately 25 kilowatts. The research facility also has solar engineers at work.

“Here we are researching how the atmospheric conditions, the altitude, the temperature and the air density have an effect upon a photovoltaic system,” said Sebastian Vogler from sol-E Suisse parent company, Swiss energy provider BKW FMB Energie AG. “The data are relevant for the SolarImpulse project from Bertrand Piccard.”

Solar Airplane 

Bertrand Piccard's goal is to fly around the world in 2011 using only solar energy to power the flight. SolarImpulse will be the first manned solar airplane that will remain in flight under the cover of darkness. The success of the project depends largely on how efficiently solar energy can be utilized at high altitude. Along with providing sponsorship money for the project, Sputnik Engineering is an official supplier of SolarImpulse and is using its expertise in MPP tracking to help in the project.

“This partnership is a new important step for the creation of the solar airplane which will fly around the world in 2011,” the company said in a press release. “For the solar airplane Solar Impulse, the MPP tracking technology controls the voltage adjustment between the solar cells and the batteries. It is optimized with the support of Sputnik Engineering AG. We are proud to count Sputnik Engineering AG as one of our official suppliers.”

Piccard and his team will only be able to get the maximum output from the solar cells with good MPP tracking. MPP trackers adapt, in the inverter, the operating voltage of the solar generator to the maximum power point. In other words, they consist of a DC converter that is connected before the inverter unit. In the case of the SolarImpulse plane, the trackers will be integrated into the battery management system.

“At the Jungfraujoch [research station] one can effectively investigate the ambient conditions that the solar airplane has to endure,” Vogler said.

The observed values from the research station are compared by BKW FMB Energie AG with the data from solar units in Swiss midland areas. The three-week test operation has already confirmed that the specific energy yield of the solar unit on the Jungfraujoch is about 70 percent higher than comparable units in the Swiss midland. At the Jungfraujoch four new SolarMax 3000 S devices are operating.

“They are the most suitable for this project: the devices have to be able to endure extreme fluctuations in temperature, to be reliable and to deliver a good yield. We have had good experience with SolarMax inverters,” said BKW representitive Antonio Sommavilla.

The alpine climate puts a load on the devices. The wind blows at more than 200 kilometers/hour. The temperatures reach –35° Celsius. The SolarMax inverters were designed to work at ambient temperatures from 20 to 60° Celsius. The solar units also benefit from the alpine climate.

“At 3,500 meters high we have less haze. The air is thinner and purer. The permanent reflection of the snow provides for a high irradiation intensity. In addition the efficiency of the silicon cells is raised by the low temperatures,” Vogler said.

Since the weather at the altitude of the Jungfraujoch can change quickly, the inverters must have good regulating characteristics. This is where, according to Sputnik, the MPP tracking ability of the SolarMax inverters pays off. When the irradiation conditions change quickly, the devices can find the maximum power point of the solar generator at any given time.