You can almost feel a gentle tugging at your skin. There’s a warm draft.

  “Why shouldn’t we use it?” asks Klas Johansson, who works for Jernhusen, the state-owned developer of the project. “If we don’t use it it’s just going to be ventilated away.”

  Citizen lamplighters, citizen furnace-stokers—antique corps of volunteers fill my imagination. All cheap and renewable. This ultragreen design works dramatically well in Sweden, a land of soaring fuel costs, ecologically minded citizens, and a legendary arctic winter becalmed by few hours of daylight and a horizon-hugging sun. Night blankets the city in stellar darkness by midafternoon. Offset as the night may be with cozy lantern-lit streets, candle-lit windows, and the luminous green ribbons and dancing halos of the northern lights, when cold clambers up the bones, more heat is the sole comfort. But fuel can take many forms, from fossil to solar energy, oil and gas to the residue left in paper mills, or Central Station’s . . . well, what shall we call it? As a technology it needs a catchy name, something sociable. Maybe “Auraglow,” “Beradiant,” “EnsnAired,” or “FriendEnergy”?

  The design of heat recycling works like this: first the station’s ventilation system captures the commuters’ body heat, which it uses to warm water in underground tanks. From there, the hot water is pumped to Kungsbrohuset’s pipes, covering a third of its fuel needs per year. Kungsbrohuset’s design has other sustainable elements as well. The windows, angled to allow in maximum sunlight during the winter, also block the fiercest rays in summer. Fiber optics whisper daylight from the roof into dark stairwells and other nonwindowed spaces, where lazy buildings would need to pay for electricity. In summer, bone-chilling lake water flows through the veins of the building. If you can’t cool off regularly by dunking in the lake, at least you can enjoy a sort of dry plunge.

  Part of the appeal of heating buildings with body heat is the delicious simplicity of finding a new way to use old technology (just people, pipes, pumps, and water). It’s worth noting that the buildings can’t be more than two hundred feet apart, or too much heat would be lost in transit. The essential ingredient is a reliable flux of people scuttling to and fro each day to tender the heat, so the design only works in high-traffic areas. Perhaps, on low-volume days, children might be invited to use the space as a gym for high-energy sports.

  “Be a joule,” the Public Service billboards for EnsnAired heating might urge, noting in fine print: “A person radiates about 350,000 joules of energy per hour, and since 1 watt equals 1 joule per second, one person can effortlessly illumine the darkening world with the energy of a 100-watt lightbulb. A city of 2.25 million people can light 22,500 lamps.” Linger with that image for a moment—a multitude of lamps, each one sparkling, but together providing a great cloak of light. Paraphrasing a proverb attributed to Peter Benenson, founder of Amnesty International, it might say: “It’s better to become one lightbulb than to curse the darkness.”

  Widening their vision to embrace neighborhoods, Jernhusen engineers talk of finding a way to capture excess body heat on a scale large enough to warm homes and office buildings in a perpetual cycle of mutual generosity. Heat generated by people at home at night would be piped to office buildings first thing in the morning, and then heat shed in the offices during the day would flow to the residences in the late afternoon. Nature is full of life-giving cycles; why not add this renewable human one?

  In this Golden Rule technology of neighbor helping neighbor, we would all share heat from the tiny campfires in our cells—what could be more selfless? Just by walking briskly, or mousing around the shops, you can stoke the heat in someone’s chilly kitchen. Possibly a friend’s, but not necessarily. I’ll warm your apartment today, you’ll warm my schoolroom tomorrow. It’s effective and homely as gathering together in a cave. Sometimes there’s nothing like an old idea revamped.

  It’s hard not to admire the Swedes’ resolve, but it wasn’t always this way. During the 1970s Sweden suffered from pollution, dying forests, lack of clean water, and an oil habit exceeding any other in the industrialized world. In the past decade, through the use of wind and solar power, recycling of wastewater throughout eco-suburbs, linking up urban infrastructure in synergistic ways, and imposing stringent building codes, Swedes have axed their oil dependency by a staggering 90 percent, trimmed CO2 by 9 percent, and reduced sulfur pollution to pre–World War I levels. It was Sweden that in 1968 proposed a U.N. conference to focus on how we’re using and depleting the environment, and when it came about, in 1972, Stockholm hosted it. Billed as the first United Nations Conference on the Human Environment, it stressed that human and environment are no longer separate entities, because we’ve reached the stage where “man is both creature and moulder of his environment.”

  In addition to harvesting human warmth with élan, the Swedes excel at coaxing energy for their cities from other renewable sources. Greeting visitors, the world’s largest energy storage unit lies beneath Arlanda, Stockholm’s airport, where an underground reservoir over a mile long heats and cools the five million square feet of terminals.

  On the windswept coast of Sweden, Joakim Byström’s company, Absolicon, has developed the world’s first solar concentrator that produces electricity and heat at the same time. Made of iron and glass, its shiny tents track the sun like parallel rows of flowers atop Absolicon’s roof, fueling its factory. A world away, in a remote region of Chile’s Patagonia National Park, twenty of Absolicon’s solar collectors fuel the hotels where hikers can overnight in comfort. Lodged atop a hospital in Mohali, India, the company’s panels produce heat, electricity, and steam.

  In their own sociable way, the small Swedish eco-city of Kalmar and its neighbor towns (a population of nearly a quarter of a million) are making a dramatic change—switching from oil, gas, and electric furnaces to recycled fuel. Heavily forested, the historic port city nestles partly on the Swedish mainland, edging the Baltic Sea, and partly on islands connected by weblike bridges. An important trading city since the eighth century, it combines cobblestone streets with state-of-the-art chic offices and museums. In winter it’s hard to tell the shards of ice floating on the sound from the jagged spires of Kalmar Castle, whose reflection mingles with them in the water. With the plentiful forests comes timber, and from it, sawdust and other wood waste, which can be used to create shared district heat, in which superheated water is piped through an underground network. Ninety percent of the region’s electricity needs are met by hydroelectric, solar, nuclear, and wind power. City-owned cars and buses run on gas made from such pickings as chicken manure, wastewater sludge, household compost, or ethanol. Hybrid cars and trucks patrol the streets, bicycles abound, and low-energy streetlights glow warmly in the dark. Without stinting on warmth or abandoning their cars, the people of Kalmar are proudly drawing 65 percent of their energy from completely renewable sources.

  To achieve this, the changeover is happening at every level, in big companies and in small kitchens and living rooms. Many homes and other buildings rely on environmentally friendly district heating. The Soda Cell wood pulp mill, previously known for making oil heaters, switched to renewable furnaces and heat pumps (doubling its sales in the process). Before, the company used to dump its hot wastewater into cooling ponds and release vast clouds of steam into the frosty air. Now it harnesses the steam to drive turbines and the hot wastewater to fill furnace pipes—providing electricity and heat, not only to its own plant, but to twenty thousand homes in a nearby town.

  Ideally, every home in the city would have solar panels and electric cars. Kalmar’s lofty goal, a community project, is to rid itself of all fossil fuels by 2030. Then, relying on gas, diesel, and oil will be a bygone folly. That’s a practical dream with pipes, not a pipe dream, even if it won’t happen overnight. “It’s important to have small victories,” says Bosse Lindholm, who manages Kalmar’s sustainability efforts. “It’s more important to go in the right direction at a slow speed than in the wrong direction at high speed.” Lindholm feels sure t
he Kalmar model would work elsewhere, “because the challenge isn’t technological, it’s changing the way people think.”

  Not far from Kalmar, a dazzling otherworldly mirrored dish perches aloft like a UFO, its landing legs extended. As if to kindle a giant bonfire or torch distant ships, Ripasso Energy has erected the parabolic mirror to catch and magnify the sun, which drives the pistons of a Stirling engine that, as the company’s spokesman explains, is “a contraption invented by a Scottish priest in the early 1800s and then further developed by Swedish submarine manufacturer Kockums.” The result is a world-record-setting blast of solar energy, the most efficient thus far. Comparing this design to China’s Three Gorges Dam, the largest hydroelectric plant in the world, Tore Svensson from Ripasso points out that Three Gorges requires a thousand times more land to generate the same amount of energy. Ripasso’s plants produce a hundred thousand gleaming sun-catching mitts a year, which provide as much energy as five nuclear power plants.

  I’m spotlighting the Swedes because they’re working with such limited raw material, wickedly little sun, and yet they’ve cooked up all sorts of brilliant designs. The lesson is: you don’t need bright sun if you have bright ideas and a culture that promotes them.

  Central Station’s heat sharing and the eco-hubs in the countryside are just pieces of Sweden’s larger sustainability jigsaw puzzle, in which a particularly striking piece is how the country handles its waste. In Sweden, a whopping 99 percent of household refuse is recycled or used to generate energy. Only a dash of it goes into landfills; the rest is scrupulously collected and burned in incinerators with state-of-the-art filters, which generates electricity for a quarter of a million homes and furnishes heat for 20 percent of the country’s heating grid. There’s just one problem. The Swedes aren’t producing enough waste to keep the generators burning. The odd-sounding solution is that Sweden imports eight hundred thousand tons of trash each year from Norway and elsewhere in Europe. Norway pays Sweden to dispose of its trash, and Sweden reaps more electricity and heat. Norway’s trash isn’t always pristine (whose is), so, not wanting to add pollutants to its shores, Sweden captures toxic chemicals and metals from the ashes and ships those back to fill Norwegian landfills. Germany, the Netherlands, and Denmark also import waste from other countries to keep their incinerators churning out electricity.

  We’re just beginning to explore the frontiers of harvesting novel sources of fuel. Consider skimming energy from train travel, based on the principle of the pinwheel. As trains pass, a sirocco of hot, jumpy winds follows, spinning up dust devils and chasing newspapers down the platform. They might be blowing from North Africa across the Mediterranean to Southern Europe. I could do something with that tugs gently at the mind, in the same spirit that some ancestor, inspired by how an animal track holds water, thought I could use one of those. Leveraging the wind, three South Korean designers, Hong Sun Hye, Ryu Chan Hyeon, and Sinhyung Cho, have found a way to use the whoosh of trains to power cities. Their “Wind Tunnel” is a network of underground subway lines that capture the wind roiled up by passing trains and funnel it to turbines and generators embedded in the subway walls. Above ground, there’d be less traffic coughing and guzzling if more commuters relied on trains, and below ground, in the arterial hum of the city, Wind Tunnels would flute electricity to apartments and offices.

  China, home to a vast network of high-speed trains, is also tempted by wind-catchers. If the idea fits well there, it may be because pinwheels have figured in Chinese culture and temples for thousands of years as powerful symbols of turning one’s luck around by casting out bad fortune and gusting in good. Hidden between the railway ties, wind turbines would funnel electricity into a well for the energy grid, which the trains tap, completing the circle.

  Or here’s another way to reuse train power: bank it. As I drive around town in my aging Prius, I know that whenever I push on the brakes it banks electricity into its battery. During low-speed driving, it milks the stored power, and it burns gas only at high speed on the highways. This spending and saving balances well, and I rarely buy gas. In Philadelphia, the Southeastern Pennsylvania Transportation Authority joined forces with Viridity Energy to create hybrid subways with the same thrift. Each time a train brakes around a curve or entering a station, it deposits energy into a big battery connected to a shared grid.

  Worldwide, in such ways, the outdated idea of travel serving only to carry people from one place to another is gradually melting into the notion of piggybacking and recycling—transportation with bonuses. This pertains to cars and buses, of course, with companies aiming for ever greater mileage on ever less fuel of a preferably renewable sort such as hydrogen or electricity. A new twist on that is the Green Apple concept car, so named because it’s designed for use as a taxi in New York City, offering “street hails” in all five boroughs. Not adding to the carbon footprint, it could actually erase part of it. A three-seater shaped like an aerodynamic space helmet, it’s powered by turbines that whip in polluted air and purify it before exhaling it back onto the street. A snarky air-scrubber. Remember riding on the vacuum cleaner Mom or Dad propelled? Yes, the air could be called what it is, “recycled waste,” but where’s the fun in that?

  Speaking of fun, some wind-harvesting ideas look like they’ve sprung from either an aviary or pages of sci-fi. I have several favorites at the moment. One is Windstalk, created by the New York firm Atelier DNA to provide clean energy for Masdar City, Abu Dhabi. A work of “land art,” it aims to provide wind energy while fluttering, oscillating, vibrating, and generally behaving “as chaotically as possible,” and also being beautiful. The gentle, incantatory winds of an otherworldy oasis infuse the designers’ description with irresistible hints of lounging and longing:

  Our project starts out as a desire, a whisper, like grasping at straws, clenching water. Our project takes clues from the way the wind sways a field of wheat, or reeds in a marsh. . . . Our project consists of 1203 stalks, 55 meters high, anchored on the ground with concrete bases. . . . The top 50 cm of the poles are lit up by an LED lamp that glows and dims depending on how much the poles are swaying in the wind. When there is no wind . . . the lights go dark . . . When it rains, the rain water slides down the slopes of the bases to collect in the spaces between, concentrating scarce water. Here, plants can grow wild. . . . You can lean on the slopes, lie down, stay awhile and listen to the sound the wind makes as it rushes between the poles. But our project isn’t just desire.

  Another of my favorites, in contrast, won’t sing and dance in the desert like Windstalk. It’s more like a sweaty air-cooled wallflower. On the lawn at the Technology University in Delft, I spy what looks for all the world like a time portal, a large sleek steel rectangular window frame hovering in the air, but not quivering in the cool spring breeze. Because it stands outside the Electrical Engineering, Mathematics, and Computer Science building, you’d be forgiven for thinking it resembled a dot-matrix zero. It might be a futuristic sculpture. Yet it’s a bladeless, bird-friendly, bat-friendly wind turbine, designed by TU Delft and Wageningen UR, the architecture firm Mecanoo, and a consortium of others as part of a government alternative-energy project. At this stage only a pioneering prototype, it promises a way to reshape wind power into electricity, despite having no moving parts, casting no intermittent shadows, creating no bone-twitching vibrations, and making none of the risen-zombie sounds reported near traditional three-bladed wind turbines coating the flanks of Andalusia or Cape Cod. No wonder passing students stare and instinctively smile, perhaps thinking as I do: How did you say again that works?

  Fortunately, Dhiradj Djairam and Johan Smit, two Delft professors who helped design the technology, can tell me. Technically, it’s a windmill, designed to produce power by milling the wind, a famous part of Dutch tradition—but without moving blades. “Wind energy is converted to electrical energy by letting the wind move charged particles against the direction of an electric field,” Djairam explains.

  A fluid steel frame e
ncircles horizontal tubes, arranged like venetian blinds, that create tiny electrically charged water droplets. As the droplets are born and rapidly blown away by the wind, they scratch out an electrical current that can flow into a city’s energy grid. Round, square, or rectangular, standing alone atop a tall wind-whipped building or in regimental rows along the coast, these “ewicon windconverters” may become vanishingly familiar the way TV aerials do, but for a while anyway they’ll appear wondrous as giant bubble-blowing wands. Or as time portals to a future where, by entangled logic, you remain yourself with all of your individual quirks and foibles, plus the savvy and ignorance of our age, and yet sense how future Earthlings live, surrounded by and largely oblivious to a phantasmagoria of techno-wonders that are as commonplace to them as ours seem to us. What sources of renewable energy will they have mastered? How will they corral the wind and drive the chariots of the sun?

  Imagine Olivine, our future geologist, standing on the shore of a sea, in the heart of a metropolis or in low orbit, and looking back at our age. Those early Anthrops, she thinks. How did they live with so much illness, and so many natural disasters, while polluting all over themselves? And why did it take them so long to discover—here you can fill in the blanks—the heliocopter, the bladeless wind-thresher, the hydrogen Coupe de Ville?