PV-powered auto manufacturing: GM's Rüsselsheim PV project

by Solar Server International Correspondent Christian Roselund
September 9th, 2012

Image source: GM
Image source: GM

Rooftop PV and automobiles

In a world where the oil industry and the car culture that it fuels are cast as opposing forces to the development of wind and solar in the public discourse, solar photovoltaic (PV) generation and automobile manufacturing can seem an unlikely pairing.

However, that is just what General Motors is doing at subsidiary Opel's manufacturing facility in Rüsselsheim, Germany, which hosts 8.15 MW-AC of PV generation on four roofs at the sprawling complex, powering production of Opel models for the global market.

The impressive scale of this project, this seemingly unlikely combination of industries, and GM's history of commissioning very large PV plants were all factors in Solar Server choosing the Rüsselsheim PV project as its September 2012 Solar Energy System of the Month.

 

Zaragoza, Kaiserslautern and Rüsselsheim

This is not GM's first foray into PV at its European factories. Spurred by an attractive feed-in tariff, in 2008 the company built a 12 MW PV plant on the roof of its factory in Zaragoza, Spain. GM has also installed a 2.5 MW PV plant at its facility in Kaiserslautern, Germany.

These plants were not only two of the five largest rooftop PV plants in the world when built, but provided GM with real-world experience in hosting large PV plants on its substantial rooftop real estate.

Following on this impressive project list, GM moved on to its Rüsselsheim factory, operated by Opel.

Rüsselsheim has been described as one of the more technologically advanced auto factories, following a renovation in the late1990's. However, the factory complex is an expansion of Opel's original auto manufacturing facility in the city, which dates back to 1906. As such, the complex is a mix of the old and the new, including historic pre-war buildings.

Opel's main portal and side building in Rüsselsheim, with factory of founder Adam Opel in the foreground; Image source: public domain
Opel's main portal and side building in Rüsselsheim, with factory of founder Adam Opel in the foreground; Image source: public domain

GM originally contracted with Solon SE to build a 1.45 MW PV plant on the roof of building K170, which it began work on in February 2010. Solon completed the plant, which is comprised of its crystalline silicon (c-Si) PV modules, in September 2010.

The next Spring, in May 2011, GM arranged with Wattner AG to build PV plants on three more roofs at the facility, K40, M55 and K65. Construction lasted from May through December 2011. Overall, the PV modules in the four plants cover 225,000 square meters of total roof area, the equivalent of 32 European football fields.

 

Module choices: CIGS and stability

For these projects, Wattner and GM chose to use both REFUsol c-Si and Solar Frontier copper indium gallium diselenide (CIS) thin-film PV modules, mounted on aluminum mounting systems.

Threlkeld states that the choice of modules was ultimately Wattner's call, as Wattner owns the PV plants, but notes that GM had an interest in experimenting with thin-film technologies.

The PV plants include a mixture of thin-film and c-Si technologies; Image source: GM
The PV plants include a mixture of thin-film and c-Si technologies; Image source: GM

"We're really agnostic to the technologies, we leave that to the developer and owner of the systems as to what works best with the facility," explains GM Global Manager, Renewable Energy Rob Threlkeld.

"Though we've been curious as to how the technology works in different regions of the world. Obviously thin-film has worked better than crystalline in some cases."

While maintaining technology agnosticism, Threlkeld does cite the importance of stability in the choice of module suppliers.

"This is done from working from a robust engineering perspective, to ensure that these installations will last the full 20 years, and that we have the support of the company that will stand behind it," states Threlkeld. "It's important to ensure that you've got someone who you can work with for the long run."

 

Roofs and structural loads

Threlkeld also notes that the pending installation of these modules prompted a re-roofing of some of the roofs at the facility, to assure that they would last the full lifetime of the PV plants.

Ironically, the older buildings posed fewer challenges.

"(With) the older buildings, the nice thing that comes across is that structural roof load issues don't seem to be a problem," notes Threlkeld. "The older buildings were definitely built in an era when you built things more robustly than now, when we value-engineer construction to break it down to a lowest-cost possible."

Dollars and cents of rooftop PV

As GM does not own these plants, it required developers to be able to use its roof space and supply electricity in a formula that works for the company.

"It needs to be at least cost neutral; to not cost GM anything to put a solar array at a facility," notes Threlkeld. He also notes that this is more challenging for a single project like the Rüsselsheim factory, as opposed to big-box stores which can commission multiple similar projects through one request for proposals.

Threlkeld notes that the greatest challenge was completing the plant in time to beat feed-in tariff cuts; Image source: GM
Threlkeld notes that the greatest challenge was completing the plant in time to beat feed-in tariff cuts; Image source: GM

The project represented a EUR 20 million (USD 26 million) investment, and Threlkeld states that the greatest challenge was assuring completion in time to beat feed-in tariff cuts which took place on July 1st, 2012.

The plant provides electricity for the factory's production floor, used to assemble automobiles in the Opel line, with excess electricity supplied to the city grid. Threlkeld notes that the PV plant's production is matching expectations.

 

Ambitions for 125 MW of wind, solar

The Rüsselsheim PV plant fits into larger ideas at GM about energy and sustainability, and the company has developed substantial renewable energy goals of 125 MW of wind and solar by 2020.

"We were one of the first if not the only auto manufacturer to do so," notes Threlkeld.

The 1.8 MW PV plant at GM's transmission factory in Toledo, Ohio is currently under construction; Image source: GM
The 1.8 MW PV plant at GM's transmission factory in Toledo, Ohio is currently under construction; Image source: GM

As part of this goal, GM is currently installing 1.8 MW of PV at a transmission plant in Toledo, Ohio, United States, a 350 kW PV array at its Orion Assembly Plant in Orion Township in the U.S. state of Michigan, and "Solar Tree" PV tracking systems by Envision solar at two other locations in Michigan. GM has already completed the first 600 kW phase of the Toledo project.

GM states that it is currently looking at other locations to build in the United States, as well as potentially building PV plants at both new and pre-existing manufacturing facilities in China, towards its goal of 125 MW of wind and solar by 2020.

In this, GM is truly a 21st century automobile manufacturer. The company's Chevy Volt was the best-selling electric vehicle in the first half of 2012, and GM has unveiled other designs for pod-like electric-networked vehicles for crowded cities.

Through both is automobile designs and its renewable energy goals, GM is actively looking at a world beyond fossil fuels. But not without cars.

The factory will produce Opel's Ampera hybrid vehicle; Image source: GM
The factory will produce Opel's Ampera hybrid vehicle; Image source: GM