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When a rooftop solar array became part of the plans to modernize the Edith Green-Wendell Wyatt Federal Building, the project team encountered an unexpected challenge.

The electrical grid the downtown Portland building is plugged into is designed to send out power, but isn’t set up to receive power flowing in the reverse direction. This made it impossible for the newly renovated office building, completed in 2013, to participate in net metering.

Net metering is a process that allows buildings that generate their own power through solar panels to feed excess electricity that occupants aren’t consuming back into the grid. The electricity meter for such buildings can run backward and provides credit toward power consumed when demand exceeds the solar system’s production.

Instead, if Edith Green’s 13,000-square-foot solar array produces more electricity than the building is consuming, the panels are rigged to shut off. This is mostly a power company safety precaution to protect the surrounding high-density power grid, but it’s also a missed opportunity, said Scott Bevan, an electrical engineer with PAE.

鈥淥ur challenge is to harvest as much of the sun’s energy as we can,鈥� Bevan said. 鈥淯sing the grid as a battery is something you hear all the time. Your building could be importing energy back to the grid.鈥�

The realization that the Edith Green building’s central city location meant it couldn’t utilize any excess solar energy it produces has spawned an effort led by Portland design and building industry professionals to raise awareness of the issue. Bevan was among several industry professionals who spoke last week about the topic at an event titled 鈥淣et Metering in Downtown Portland鈥� hosted by the Cascadia Portland Collaborative. The group is affiliated with the International Living Future Institute, which administers the Living Building Challenge, a stringent green building that requires net-zero energy usage.

鈥淭he genesis of this was the shocking revelation about net metering and potentially why it wasn’t happening (in downtown Portland),鈥� said Steve Clem, vice president of preconstruction with Skanska.

The limitations of Portland’s central city electrical grid to support power flow in two directions could impede development of more net-zero buildings, said Lisa Petterson, an associate principal with SERA Architects and an International Living Future Institute board member. This flies against carbon reduction goals set by the city of Portland and Multnomah County in its draft 2015 Climate Action Plan, she said. The plan, an update to a 2009 version, sets goals of promoting new construction and retrofit projects that achieve net-zero energy usage. City officials also hope to raise awareness and promote the Living Building Challenge and other green building certifications that have more stringent energy efficiency requirements than the U.S. Green Building Council’s Leadership in Energy and Environmental Design program.

A lack of net metering downtown would also present a significant hurdle to Portland attracting a large commercial project similar to Seattle’s Bullitt Center, Petterson said. Earlier this month, the Bullitt Center officially became the first office building to earn Living Building certification.

A large contributor to the Bullitt Center’s success is that through net metering, the building can use the grid as a battery when it produces more electricity from the solar panels on the roof than the occupants use, Bevan said.

It wasn’t until SERA staffers designed the Edith Green modernization project together with Cutler Anderson Architects that the project team found out this wouldn’t be possible in downtown Portland, Petterson said.

鈥淚t was really the Edith Green-Wendell Wyatt building that engaged us in this conversation 鈥� that it was not possible simply because of where it was located,鈥� she said.

Devices called network protectors are installed in Portland’s central city grid to stop electricity from traveling in the reverse direction, Bevan said. The devices help prevent failure of the high priority grid, but are the main reason why net metering is impossible downtown, he said.

When the Edith Green project team approached Portland General Electric about returning electricity to the grid, they were told it would be too dangerous, Petterson said.

鈥淧GE wanted a factor of safety with the equation that they would never get a surge back into the grid because what would happen is it would essentially shut down the grid in that part of the city,鈥� she said.

The design team explored several options for using the excess energy in other ways, such as setting up an electric car charging station or transferring power to another building, but none panned out, Petterson said.

The Edith Green project team eventually decided to pursue a LEED platinum designation for the building, which was received earlier this year.

At this point in time, the one feasible option for a larger commercial Living Building Challenge project in Portland would be to construct it outside the downtown core where the electrical grid is less complex and can accommodate net metering, she said.

鈥淪o far, that’s the only solution we’ve been able to come up with,鈥� Petterson said.