Solar highway facts and fallacies
It’s good to listen to the younger generation, even if they are not engineers. My two nephews recently brought to my attention a Solar Highway concept they had encountered while communicating with their usual sites and contacts on the internet. Thanks guys!
The Solar highway or solar roadway is a complex concept of solar energy architectures around and in the highway, road and street infrastructure including adjacent areas along the side of the highways and on bridges and other associated structures. Opponents think that there is no reliable way to drive on a solar-paneled surface, that the Right-of-way (ROW) cannot be imposed upon, and many more misconceptions that this article will clarify.
It seems that solar energy is one of the top renewable energy hopes for a greener environment. There are efforts by the U.S. Department of Transportation1 (U.S. DOT) to help reverse global climate changes in the area of transportation vehicles that cause greenhouse gas (GHG) emissions on the nation’s intricate network of highways and roads.
There are many challenges with trying to find enough surface area to put solar panels in place, especially in large metropolitan areas. But the concept of using highway “right-of-way (ROW) could be an untapped area for this endeavor.
The highway ROW is not without its challenges however. There are potential legal and political issues, plus ecological and economic uncertainties regarding the practicality of this idea.
In 2008, the Oregon Department of Transportation (ODOT) was the first organization in the US with a solar photovoltaic project design that was able to light an interchange in the highway “right-of-way”. See Figure 1.
Figure 1: The ODOT Solar Highway Demonstration Project. The Solar design consists of 594 solar panels to make up a 104 kWDC ground-mounted solar array system. (Image courtesy of Oregon DOT)
Oregon partnered with Portland General Electric (PGE) and located the project at the Interstates 5 and 205 in Tualatin, OR. SunWay1, a company managed by PGE, owns and operates the system and the ODOT purchases that electricity at the same rate it pays for regular power from the grid.
After this prototype, the ODOT and PGE used the highway ROW on seven acres of ROW next to the Baldock Safety Rest Area on Interstate 5. A 1.75 MW DC solar array with 6.996 250W panels was installed. See Figure 2.
Figure 2: ODOT’s Baldock Safety Rest Area Solar Highway Project (Image courtesy of Gary Weber, ODOT)
It’s not just the U.S. that has launched such an effort; Germany is developing a 2.8 MW solar highway project near Aschaffenburg. The German Unity Motorway Planning and Construction Company constructed this German project. Solar cells have been installed in noise barriers along highways like this one in Germany and also in the UK, Netherlands, Switzerland, Austria, and France. See Figure 3.
Figure 3: A 2.8 MW solar array was constructed on the roof of a 2.7 km long noise-barrier tunnel on the A3 highway near Aschaffenburg, Germany (Image courtesy of Ralos New Energy)
One problem in the U.S., is that this type of installation would be limited by the AASHTO Roadside Design Guide. No structures of any sort are allowed to be placed on top of or directly behind guardrails or median barriers (unless the barrier is specifically designed to be crash-worthy). See FHWA Office of Infrastructure's Clear Zone and Horizontal Clearance website for more information.