Like the rest of us, advocates for renewables can fail to spot their true friends. Fans of the recent blockbuster Avatar might imagine that ecosystems get rescued by dreadlocked tree-huggers while the film's bad guys are on the ecological frontline. Buzzcuts and heavy weaponry may jar with climate change aesthetics, but back on planet Earth, though, the US military is now spearheading the global assault on carbon emissions on a range of fronts, including solar power.

And the same goes for the motor industry, where the internal combustion engine’s environmental drawbacks seem to be spurring investment in renewables.

Certainly, the auto industry has strong incentives to step up a gear in emissions wherever it can. Almost a quarter of global oil production heads to the fuel tanks of cars and light trucks. What’s more, carbon emissions per watt from petrol-fuelled car engines outweigh those from even the dirtiest coal-fired grids, according to a 2007 study by the Electric Power Research Institute (EPRI) and the Natural Resources Defense Council (NRDC).

But solar installations must compete for the sector’s attention with a full deck of alternative green technologies. While a long-heralded transition to electric vehicles continues to sputter, global automotive brands have invested in solar, wind, biofuels and hydropower.

In Germany, an aggressive target for six million electric cars on its roads by 2030 sets a challenge for the power sector as well as its automotive industry. If this goal can be taken seriously, where are the sustainable power sources to charge all these vehicles?

Daimler is already addressing this issue by buying up wind capacity. An initial investment already delivers enough clean kilowatts to the German grid to keep several thousand E-Smart cars on the road, according to the manufacturer. If sales outpace the company’s targets, it will invest in additional renewable power sources, says the firm.

Not to be left behind, BMW has installed four wind turbines to power a factory in Leipzig where it aims to assemble electric and hybrid models. Volkswagen operates a wind farm that supplies 20 GWh each year and has signed a deal to meet 10% of its 12 German plants’ power demand with hydropower from 2013.

Audi aims to pioneer ‘e-gas’ by using wind-generated electricity to split water molecules through electrolysis. The resulting hydrogen would help to make synthetic natural gas for fuelling engines.

Meanwhile, French carmaker Renault has opened a ‘zero-carbon’ factory in Morocco powered by wind turbines and cogenerating biomass boilers.

Solar in Greener Motoring

By comparison with ‘e-gas’, solar installations could appear lacking in technological glamour. But as a mature, proven technology, solar could offer an excellent fit for the automotive industry’s power needs. A series of solar PV installations at automotive manufacturing plants are already proving this fact.

As well as rolling out its flashy wind and biomass project in Morocco, Renault has installed what it describes as the auto industry’s largest PV project. Under a deal with the developer Gestamp Solar, six French plants have been equipped with solar panels totalling 55 MW.

The solar panels cover areas corresponding to the delivery and dispatch of the plants at Douai, Maubeuge, Flins, Batilly and Sandouville as well as the staff car parkings in Cleon and Maubeuge. Construction got underway in mid-2011 and was completed in early 2012.

While this project marked a step-change for solar PV at European automotive sites, Gestamp had already participated in two other PV projects for the sector: a 1.1 MW system for Lamborghini in Italy and an 8 MW system for Seat in Spain.

The Lamborghini project, at Sant’Agata Bolognese in the city of Bologna, consisted of three phases totalling 1.168 MW on the roof of the carmaker’s factory. The project’s special challenge was to allow normal production to continue during installation. Now, in addition to providing renewable power, the completed solar field optimises the facility’s existing surface.

Near Barcelona, in northern Spain, Gestamp has been developing PV at Seat’s Martorell plant since 2008. In a first phase, a pilot plant was built on the roof of the carmaker’s headquarters. Two plants, each of 2 MW, were then installed on the roofs of assembly workshops and on the canopies that cover two parking areas for finished vehicles.

The project continued with new plants on the roofs of other workshops at the Martorell factory and on the canopies of other parking lots, to bring total output to 10.6 MW.

Shelters installed in the parking areas to support the solar panels allow Seat to protect its newly manufactured vehicles from the weather and the paint-damaging effects of UV light. As with the installations for Lamborghini and Renault, the project’s environmental impact was reduced by using land already occupied by the carmaker’s facilities. On completion, solar panels will cover six plants, six workshops and the canopies of four parking areas.

Mitsubishi has also shown solar ambitions in Europe, albeit on a smaller scale, with a 50 kW array on the roof of its UK headquarters in Gloucestershire.

Targeting Carmakers

For Ben Hill, head of Trina Solar Europe, the automotive industry’s interest in PV rests on three factors: a feel for technology combined with economic opportunities and appropriate locations.

‘Firstly, as you might expect with automotive companies, we have found that there is a widespread culture of innovation in the use of technology,’ he said.

‘This has made decision-makers more open to think of innovative ways to improve the energy efficiencies of their manufacturing base.’

‘Basic economics’ then enhances manufacturers’ interest in PV installations. ‘Car manufacture consumes relatively high levels of energy and we have found that the higher the energy use, the greater the interest is in alternative sources of energy,’ Hill said.

‘This is particularly the case as government policies to reduce carbon emissions through taxation or other fiscal measures come into place,’ he added.

Finally, many factory units are large, flat-roofed buildings, which makes them ‘ideally suited’ for solar installations – although Hill cautions that some buildings were designed with economic efficiency in mind and can only carry their own weight. ‘Installations of PV panels may therefore not be possible without alterations to the basic structure to the building,’ he added.

Trina Solar’s determination to profit from PV’s apparent benefits for automotive plants may be seen in several projects. The company supplied 55 MW of panels for Renault’s massive investment in solar power and the Chinese panel maker has also engaged in a high-profile alliance with the Lotus Formula One racing team.