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Denmark’s Renewable Energy Island Comes of Age

By Philip Warburg

Wind turbines on the island of Samsø
Wind turbines on the island of Samsø. Photo credit: Philip Warburg

At a time when President Trump and his followers in Congress are hell-bent on dismantling the clean energy architecture of the Obama era, many Americans are looking beyond Washington, and even abroad, for solutions to our climate crisis. I recently witnessed one of these transformative gems on a visit to the Danish island of Samsø, which just passed the twenty-year mark in a campaign to supply all of its energy needs from local renewable resources. 

Home to some 3,700 year-round residents and tens of thousands of summer visitors, Samsø is a micro-scale lab for energy innovation. In 1997, the island won a national competition that set as its goal 100 percent renewable energy reliance within ten years. At the time, the island’s electricity came via undersea cable from Denmark’s grid, with coal supplying most of the power. Oil shipped from the mainland was the primary feedstock for heating Samsø’s homes and businesses, as it was for virtually all transportation on the island. 

A lot has happened since then to transform the island’s energy economy. Søren Hermansen, son of a Samsø farmer and founder of the Samsø Energy Academy, has been the guiding force behind the island’s shift to renewable energy. Gray-haired and bespectacled, he looked surprisingly youthful in his blue jeans, hoodie, and sneakers when he greeted our group of visitors—a delegation of Washington State policymakers who were exploring sustainable energy infrastructure in Denmark and Sweden. Hailing from Boston, I was the sole East Coast interloper.  

“Think local—act local” is the expression Søren uses to inspire his fellow islanders’ efforts to achieve their own brand of energy independence. It’s no surprise that wind power is a central feature of this initiative. The wind blows steadily across Samsø’s gentle terrain and the waters of the Kattegat surrounding it. To witness this power source, Søren leads us into an open field where we observe five neatly spaced one-megawatt turbines, modestly-scaled by modern standards. They are Danish-built, like so many of the turbines that have fueled the global wind revolution. 

At first the rollout of windpower had some island residents worried. Noise was one concern; the visual prominence of turbines was another. Søren recalls the discussions that ensued. Having grown up locally, his Samsø roots helped in persuading farmers to share ownership of their turbines with nearby landowners. “When we started talking as a community,” he says, “we found we could do things that we couldn’t do individually.” With a hint of mischief, he adds: “When you own part of a wind turbine, it sounds better. It looks better.”

Samsø’s onshore turbines—eleven in all—generate enough electricity to meet the island’s overall electric needs when averaged over the course of a typical year. Though wind is an intermittent energy resource, matching the turbines’ output with local power demand at a given moment isn’t necessary since Samsø retains its connection to the Danish grid. Any shortfall in local electricity is filled by grid-supplied power, and surplus windpower is absorbed by a transmission network that links Denmark to much of Europe. In this sense, Samsø differs from many islands around the world that are cut off from outside power sources and have to find their own local means of balancing electricity supply and demand. 

This same grid connection makes it easy for Samsø to offset the island’s still-high carbon emissions from the transportation sector. In the village of Tranebjerg (pop. 824), Søren shows us a 120-kilowatt solar carport that charges the Samsø island municipality’s small fleet of electric vehicles. He readily admits, though, that most cars, trucks, and buses on Samsø still rely on gasoline or diesel fuel. Dwarfing the carbon emissions from those vehicles are the diesel-powered ferry boats that regularly ply the waters between tiny Samsø and the Jutland peninsula, to the west, and Denmark’s most populous island, Zealand, to the east. While one boat has been converted to liquid natural gas and there’s some talk of switching others to biogas, these vessels remain the number-one generator of carbon emissions on the island.

To neutralize its transport-related carbon emissions, Samsø has invested in an array of ten offshore wind turbines whose primary function is to feed clean electrons into the grid. Five of these are owned by the Samsø island municipality; three are privately owned; another two are under cooperative ownership. Taking this infusion of renewable electricity into account, Søren estimates that Samsø residents have a per capita carbon footprint of minus 3.7 metric tons per year. Compare that to the 16.5 tons of carbon emitted annually by the average American, or even the 5.9 tons of carbon a year emitted by the average Dane!

And what about all those homes and businesses that were heated with oil at the outset of the energy project? Today, most islanders rely on four district heating systems that use local crop waste as their feedstock. We visited one of these plants, in a high-roofed metal shed just outside the village of Ballen, where our ferry landed.

Søren Hermansen shows American visitors straw – the feedstock for Samsø’s Ballen-Brundby district heating plant.
Søren Hermansen shows American visitors straw – the feedstock for Samsø’s Ballen-Brundby district heating plant.

Inside the shed, we stand in the shadow of giant bales of straw stacked six high. Each weighs roughly 1200 pounds. The bales are sent through a mechanical shredder and from there, via conveyor, the straw is fed into a blazing furnace. Wheat straw happens to be used in this particular plant, but barley, oat, and canola straw can also be efficiently burned. Waving a long steel probe in front of us, Søren tells us that the electronic read-out on this wand measures the straw’s moisture content, which mustn’t exceed fifteen to twenty percent.

One visitor asks: “How much straw can be taken from the fields without depleting the topsoil?” Søren has a ready answer: half of it. “Only so much organic matter can be composted in topsoil,” he tells us. Before Samsø’s district heating plants were built, farmers used to burn the excess straw in their fields—far more polluting than the combustion of straw in the carefully controlled furnaces at district heating plants. Moreover, with a ban on open burning in place, farmers welcome the chance to sell their excess straw to the heating plants. They have no other ready use for it on-island, and shipping straw for sale off-island is far too costly.


Søren Hermansen shows visitors the straw-fired furnace at Samsø’s Ballen-Brundby district heating plant.
Søren Hermansen shows visitors the straw-fired furnace at Samsø’s Ballen-Brundby district heating plant.


Hot water produced by district heating plants travels through a closed loop of steel pipes to homes and businesses that can be as much as a few miles away. Søren estimates that about a quarter of the heat energy is lost en route even though the pipes are buried and insulated. While this is significantly greater than the heat loss from a typical home furnace, Samsø’s district heating plants have vastly reduced the island’s reliance on fuel oil. Only a minority of islanders continues to heat their buildings with oil—those that are too remote to be connected to district heating or those whose owners have simply refused to give up their old oil burners. 

Two decades have passed since Samsø set its sights on a renewable energy future. To an impressive degree, that future has arrived. To be sure, using surplus windpower to offset the transport sector’s ongoing dependence on fossil fuel masks a missed step in the island’s energy transformation. Might islanders opt for electric passenger vehicles as their next car purchase? With a host of new electric vehicle models flooding the global market, perhaps, but given the recent rightward shift of Denmark’s ruling coalition, major incentives accelerating the adoption of EVs are less than likely, according to policy analysts we met. Could locally produced biofuel serve the needs of farm equipment that can’t be durably operated on electric batteries? Failed past attempts to launch a biofuel industry on Samsø don’t give much ground for hope in this regard either. Yet, even with these flaws, Samsø householders, farmers, and businesses have made their island a model—albeit imperfect—for locally-based renewable energy reliance.


About the Author 

Philip WarburgPhilip Warburg is a Non-Resident Senior Fellow at Boston University’s Institute for Sustainable Energy.  His recent books include Harvest the Wind and Harness the Sun, both published by Beacon Press. Formerly he served as president of the Conservation Law Foundation. Follow him on Twitter at @pwarburg and visit his website.