Central Station in Stockholm is a bustling place, seven days a week.
More than 250,000 passengers utilize the Scandanavian rail system to commute to work; many allow some extra minutes during the day to pop into the numerous shops, cafes, and kiosks before and after their scheduled trains arrive and depart.
Central Station is the region's busiest travel hub, an often hot and sweaty place from the flux of rushed bodies hurrying through corridors to catch their rides. But after the peak hours have passed, that energy is lost... until last month.
This body heat is now being captured and transferred to heat office buildings.
This latest green energy system has been in the works for two years and was recently unveiled on April 1. It is the brain child of Sundholm, a project manager at the Stockholm real estate company Jernhusen, and Johansson, head of Jernhusen's environmental division. Jernhusen owns both the train station and the office building receiving the energy.
The colleagues hatched the idea over coffee one day as they pondered if energy created by moving human bodies could be transferred from a place of excessive heat, Central Station during commuter traffic, to a place of excessive cold, an office building near the station. 
The system works by capturing the heat generated by commuters via the train station's ventilation system. This heat warms water in underground tanks, which is then pumped through pipes to and incorporated into the main heating system of the Kungbrohuset office building, about 100 yards from the station.
The system is environmentally friendly and cost-effective. The projected energy savings for the Kungbrohuset building are 20% a year — and this for technology that only cost the firm $30,000.
The building will receive 15%-30% of its heat from this system, and stands to make its investment back in just a few years.
And of the energy source — his fellow Swedes — Sundholm says, "They're cheap and renewable."
It's also worth pointing out that utilizing body heat as an energy source for heat removes the carbon emissions that come with fossil fuel heating from the equation...
Transferring excess body heat to buildings is a concept that we've seen on U.S. soil. Minneapolis' Mall of America recycles body heat from shoppers and uses it to regulate the mall's temperature during the winter.
But the Swedish take on this concept is different because it expands transfer and transformation of energy to exist between separate buildings, still just using pipes, water, and pumps.
Stockholm's Deputy Mayor Ulla Hamilton attributes her city's energy efficiency initiative to "smart people. And that's a very good example of why Stockholm is so strong on environmental issues... because we have had politicians, we have had Stockholmers, and we have companies who actually are very much engaged in these issues. And they find smart solutions."
They're discussing energy efficiency, brainstorming green technology, and jotting down ideas on napkins during coffee breaks.
"We would like to have a green and blue city as we do today, and this is something that Stockholmers also think is important," Hamilton says.
Sundholm hopes to expand this project to one day be able to transfer body heat generated in residential areas at night to office buildings in the morning, and back again in the afternoon. This cycle would allow for efficient heating with a seemingly endless heat source supply.
You can check out more with this on-location news clip from Time.
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