BERLIN—From 200 miles above, Canadian astronaut Chris Hadfield looked out a window of the International Space Station at the shimmering lights below and snapped a photo of Germany's capital.

At night, the city's streetlamps trace the roads splaying from the city center like a spiderweb. The lights and the darkness in between chronicle the city's modern history.

In the photo, you can see where the Unter den Linden boulevard meets the Brandenburg Gate at the edge of Tiergarten, which appears as a black oval with a golden skewer through it. The other dark circle in the center of the photo is Tempelhof Airport, now a park, where American C-47 cargo planes brought in food, coal and medical supplies during the Soviet blockade of West Berlin.

But the most conspicuous relic of the once-divided city is in the lights themselves.

"Amazingly, I think the light bulbs still show the East/West division from orbit," Hadfield wrote in a Facebook post last year.

On the left side, corresponding to West Berlin, the lights show up as grayish-blue compared to the amber-colored lights in the eastern part of the city. Where they meet traces the path for the 12-foot-high, graffiti-coated concrete barrier that divided Berliners for 29 years.

Though the wall itself fell beneath sledgehammers and bulldozers, reduced to a two-brick-wide memorial running through the city, the ghost of a divided country still haunts Germany's energy systems.

From power plants to transmission lines, Germany has spent the last 25 years erasing the differences between east and west, pouring billions into energy infrastructure.

Among the world's most ambitious CO2 cuts
However, the country as a whole is now aiming for some of the most aggressive climate and energy targets in the world under the "Energiewende," or energy transition. Germany's goal is to switch off all of its nuclear reactors by 2022 and generate 80 percent of its electricity from renewables by 2050. At the same time, the German government set a greenhouse gas emissions reduction target of 80 percent from 1990 levels by 2050.

The unification process offers some insight into how the country can achieve its ambitions: Under the German Democratic Republic, East Germany annually mined 300 million tons of lignite, or brown coal. Lignite is much dirtier to extract and burn than harder coal varieties, but it's cheap and abundant in Germany, and the GDR fulfilled 70 percent of its energy demand from it, including electricity, heat and even transportation.

Another 10 percent of the energy supply came from Soviet-designed nuclear reactors. The grid was centralized, with large plants distributing power to population and industrial centers throughout the east. The Communist GDR government planned and managed the energy system from the top down.

All of this crumbled along with the wall.

Right after unification, officials shut down all East German nuclear reactors and halted construction on a new one, citing safety concerns. A new utility formed in the east to carve up the remaining carcass of the GDR's energy industry, buying up state-owned generators and transmission lines at cheap prices.

"After this liberalization of the market overnight, a big chunk of the lignite industry went bankrupt," explained Felix Matthes, research coordinator for energy and climate policy at the Institute for Applied Ecology (Öko-Institut) in Berlin.

Many of the old East German power stations could not compete on the open market and went offline. Redundant systems were scrapped and power generation moved away from centralization toward distributed municipal utilities, many of which decided to build their own gas-fired cogeneration plants.

Over time, Cold War-era coal plants yielded to new, cleaner, more efficient coal-fired generators as investment drawn in by favorable tax breaks poured in from western Germany and around the world. The German government, however, paid for cleanup and rehabilitation of open-pit lignite mines.

It took a few more years for the transmission grid to unite. West Berlin remained an electrical island until the city installed interconnects in 1995. The grid operator in eastern Germany, 50Hertz, did not respond to requests for comment.

Riding the highs and lows of solar
Meanwhile, the first iteration of the country's renewable energy feed-in tariff, which passed the Bundestag in 1991, went into effect. Solar and wind energy found a comfortable home in the east because some cities saw their populations plummet as local factories closed due to stiff market competition.

This left an overbuilt, costly energy system with little revenue going to big energy companies to support upkeep, let alone upgrades. Communities in the new eastern Länder, or federal states, responded with energy cooperatives, building wind turbines, installing rooftop solar panels and constructing biomass generators to meet their own needs.

Clean energy only ramped up further when Germany's Renewable Energy Act (EEG) passed in 2000, and as solar manufacturing took hold, East Germans rode the highs and lows of the industry's boom, bust and renewal. The region is also home to one-third of Germany's wind energy capacity.

Though renewable energy supplied 28.5 percent of electricity consumption throughout the whole country in the first half of this year, the share rose above 40 percent in the former GDR.

Shuttered factories, decommissioned fossil power plants, increasing renewable energy penetration, efficiency upgrades and a declining population all added up to a big cut in greenhouse gas emissions in the east. During the decade after reunification, German carbon pollution fell 15 percent. In the eastern Länder, power-sector emissions declined by 43 percent between 1990 and 1995.

These advances exacted a dear price from the reunited nation. "It has not been free of charge," Matthes said. "It has cost the German taxpayer €1.5 trillion up until now."

East Germans, in particular, suffered when their state-subsidized electricity rates tripled, rising to the market price that West Germans paid. The gross domestic product in the region shrank by one-third in the two years immediately after the wall fell.

Some of the investment in East German energy also had unintended consequences, since they arose before climate change entered the public conscience. The coal power plant fleet is much newer in the east, meaning it still has decades to spew more carbon dioxide, while many fossil power plants in the west are coming up for retirement, opening up the possibility of replacing them with something cleaner.

Energy companies still mine roughly 80 million tons of lignite in the east. This summer, mining companies received approval to expand open-pit operations, sparking international protests (Greenwire, Aug. 25).

Managing high levels of intermittent power
Nonetheless, the overall German economy has grown over the past two decades and is now the largest in Europe. And despite the high levels of intermittent renewable energy, the Council of European Energy Regulators found that Germany has the most reliable electric grid on the continent.

"In a way, eastern Germany is an interesting case for the German Energiewende, because on one hand, you do have a lot of coal, but on the other hand, you have a lot of renewables," said Patrick Graichen, executive director of Agora Energiewende, an energy think tank in Berlin. "If you want to understand how to manage a fluctuating [renewable energy] system, eastern Germany is already at high shares."

Like reunification, the Energiewende arouses a sense of solidarity among Germans, despite the fact that the costs fall to the ratepayer (ClimateWire, Oct. 22).

And public officials are not backing away from their lofty objectives, even though the rest of the European Union agreed last month to a weaker target of a 40 percent reduction in emissions by 2030. Last week, the German environment ministry announced it is considering plans to shutter some coal-fired power plants to curb greenhouse gas emissions.

As for Berlin's lights, the distinction may fade as the city replaces mercury and sodium-vapor lamps with more efficient LEDs. The German capital is also home to nearly 44,000 gas lamps, more than half of those remaining in the world, and activist groups like Gaslicht-Kultur are lobbying to keep them lit. With some of these fixtures dating back to the 19th century, the lights illuminate a part of the country's history that Berliners don't want to forget.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500