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As we attempt to objectively research nature, we are sometimes reminded of how pure forces have an effect on us personally. We are able to sit at a desk and think about warmth in its varied types, however we is likely to be distracted if our toes are chilly! After we flip up the warmth in our houses and workplaces, we should stability our private want for heat with the worldwide affect of burning fossil fuels like oil, fuel, coal, and biomass. Anthropogenic local weather change confronts humanity with a problem: How can we preserve heat now as we attempt to stop our world from overheating sooner or later?
It’s a daunting query {that a} startup referred to as Polar Evening Vitality, within the small and chilly nation of Finland (Determine 1), is trying to reply. In a area recognized for lengthy, darkish winter nights, Polar Evening Vitality is constructing a system within the metropolis of Tampere that may warmth buildings with saved photo voltaic power — all day, all evening, and all winter lengthy. The obvious contradictions don’t finish there. In an period of complicated cleantech options, typically constructed from uncommon and costly supplies, Polar Evening Vitality’s warmth storage and distribution system consists of easy ducts, pumps, valves, and sand. The novel system reveals potential for tackling international issues in a affected person, considerate, and human-scaled means.
A Small Nation with Giant Heating Wants
Huge issues demand massive options, and there’s maybe no greater Twenty first-century drawback than local weather change. To satisfy this problem, many governments and organizations are investing in new expertise to assist reduce the usage of fossil fuels. These initiatives have largely targeted on renewable electrical energy era, distribution, and storage.
“If you ask individuals about cleaner power, they consider electrical energy,” says Tommi Eronen, CEO of Polar Evening Vitality. “However we even have to chop emissions from heating.” Out of Finland’s energy-related emissions, 82 p.c come from heating home buildings (Ref. 1). “We wish to change all of that if we’re to have any hope of assembly our international local weather objectives,” Eronen says.
Suppose Globally, Warmth Regionally
The spirit of “Suppose Globally, Act Regionally”, a mantra related to the Nineteen Sixties, lives on with Polar Evening Vitality’s staff of innovators. Their journey started with a query posed by its founders, Tommi Eronen and Markku Ylönen, once they had been college classmates: “Is it doable to construct an energy-self-sufficient and cost-effective hippie commune for engineers utilizing solely solar energy?” After commencement, the challenge they codenamed “Hippie Commune” turned Polar Evening Vitality, with Eronen as CEO and Ylönen as CTO.
What started as a lighthearted (however severe) pupil challenge led to a 3 MWh/100 kW pilot plant within the Finnish metropolis of Tampere, which started operation throughout the winter of 2020–2021. The system makes use of electrical energy to warmth air, which is then circulated by an exchanger that heats water and distributes it to a number of buildings within the metropolis’s Hiedanranta district (Determine 2).
Contained in the system, electrically powered resistive heating parts warmth air to greater than 600°C. The new air is circulated by a community of pipes inside a sand-filled warmth storage vessel. The new air then flows again out of the vessel right into a warmth exchanger, the place it heats water that’s then circulated by constructing heating methods. The sand’s warmth storage capability ensures that even when the resistive parts are cool, the circulating air continues to be sizzling sufficient to maintain the water (and buildings) heat.
“We solely have pipes, valves, a fan, and an electrical heating factor. There’s nothing particular right here!” Eronen says, laughing.
A Battery for Warmth Made out of Sand
Famous chemical engineer Donald Sadoway is quoted as saying: “If you wish to make a dirt-cheap battery, you must make it out of filth.” Polar Evening Vitality’s system faces the identical core challenges as another power infrastructure. It should ship energy to individuals once they want it, the place they want it, and at a manageable worth. Which means that storing and distributing power is as necessary as its era. Current infrastructure meets these challenges in acquainted methods. For combustion-based heating, fuels like oil and fuel are saved and moved to the place they are often burned. {The electrical} grid additionally helps the environment friendly distribution of energy and makes use of power generated by renewable means like wind and photo voltaic. The intermittent nature of daylight and powerful winds, nonetheless, is a cussed drawback. Vitality storage is required to keep up regular energy output all through the peaks and valleys of renewable inputs. However even with current advances in battery expertise, storing electrical energy stays comparatively costly, particularly on the scale required for heating buildings. What if, moderately than storing electrical energy, a “battery” might retailer warmth as an alternative?
Determine 3. Markku Ylönen with a consultant pattern of Polar Evening Vitality’s dirt-cheap warmth storage medium.
Many standard heating methods already retailer and distribute warmth by retaining and circulating heat water. Eronen and Ylönen acknowledged the advantages of water-based warmth storage in addition to its limitations. “There’s solely a lot warmth you possibly can add to water earlier than it turns into steam,” says Eronen. “Steam can effectively distribute warmth, however it isn’t actually cost-effective for large-scale storage.” To keep away from the drawbacks of storing warmth in water, they as an alternative turned to sand — 42 metric tons of it! (Determine 3) After the Solar goes down, the sand’s saved warmth is progressively launched again into the circulating airflow. This retains the air sizzling sufficient to keep up regular temperatures within the water that flows by clients’ radiators. On this means, sand allows solar energy to maintain individuals heat, even throughout the darkest and coldest Finnish nights. “Sand offers 4 instances the power storage capability of water,” Eronen says. “Sand is environment friendly, unhazardous, transportable, and low-cost!”
“We’d like predictive modeling to reply as many questions as doable, earlier than we decide to assembling all this gear—and all this sand!”
—Tommi Eronen, CEO of Polar Evening Vitality
The Subtle Evaluation Behind a Easy Answer
Value effectivity is the inspiration of Polar Evening Vitality’s worth proposition. “As quickly as we determined to pursue this concept, we had been attempting to determine how the funds appeared,” says Eronen. Of their quest to do extra with much less, Polar Evening Vitality has lengthy relied on numerical simulation instruments. Eronen and Ylönen started utilizing the COMSOL Multiphysics software program as college students and it stays integral to their design course of. For instance, Eronen mentions the specs of an expanded warmth storage system that will serve extra buildings in Tampere. The staff calculated that supplying warmth to a district of 35,000 individuals would require a sand-filled storage cylinder that’s 25 meters tall and 40 meters in diameter. How did they arrive at these dimensions? “The tough amount of fabric wanted is definitely simple to calculate, as a result of we all know how a lot warmth we are able to retailer in a cubic meter of sand,” Eronen explains. “We additionally needed to decide the house required for environment friendly warmth switch between the sand and our air circulating system (Determine 4). That’s way more tough to do! We used COMSOL to mannequin and consider totally different design choices.”
Determine 4. Tommi Eronen (foreground) and Ylönen inspecting the ductwork of a Polar Evening Vitality warmth storage vessel.
Multiphysics simulation software program helped form Polar Evening Vitality’s warmth exchanger design (Figures 5–6). Eronen says, “We constructed a selected mannequin to discover a design concept: What if we created a brilliant sizzling core of sand surrounded by heating ducts across the perimeter?” By modeling fluid circulate and warmth switch results within the COMSOL Multiphysics software program, the Polar Evening Vitality staff might quantify its design’s comparative benefits and downsides. “The simulation confirmed that the ‘sizzling core’ design was good at storing warmth for very lengthy intervals of time,” says Eronen. “However for our meant operational cycle, it makes extra sense to evenly distribute sizzling air ducts all through the sand storage vessel,” he explains.
The sheer scale of Polar Evening Vitality’s sand-based warmth storage system makes simulation software program indispensable. “We can’t presumably construct full-size prototypes to check all of our concepts. We’d like predictive modeling to reply as many questions as doable, earlier than we decide to assembling all this gear — and all this sand!” Eronen says. “It’s important for us to make use of these immensely highly effective instruments.”
Adapting New Concepts to Current Infrastructure
By separating the duty of warmth storage from warmth era and distribution, Polar Evening Vitality has made its system extra environment friendly and adaptable. There’s nice potential for retrofitting their sand-filled warmth storage and switch methods into current infrastructure (Determine 7). Tampere, an inland Finnish industrial metropolis of almost 250,000 individuals, is a perfect testing floor for this new expertise. “Tampere, like many European cities, already has a district heating system that circulates water throughout complete neighborhoods,” says Eronen. “That allows us to change many buildings to a renewable warmth supply rapidly,” he says. Polar Evening Vitality’s pilot plant in Tampere can even faucet into energy from the prevailing electrical grid, together with electrical energy generated by new photo voltaic panels. Dependable thermal storage allows town to generate or buy energy when it’s most reasonably priced after which distribute warmth when it’s wanted most.
Determine 7. A part of the warmth switch system put in by Polar Evening Vitality in Tampere, Finland. The vertical pipes at left are a part of the warmth exchanger, whereas the resistive heater parts are wrapped in white insulation at proper. Between these parts is the air-circulating radial blower.
Right this moment: Finland; Tomorrow: The World
For the reason that Tampere system started operation throughout the winter of 2020–2021, the Polar Evening Vitality staff has been gathering information to match to their fashions. “Our simulations have confirmed to be very correct, which is encouraging,” Eronen says. And because the Polar Evening Vitality staff continues to develop their concepts domestically, they’re aiming to behave globally as effectively. The identical expertise that warms Finland’s lengthy, chilly nights can even present higher power administration choices to the remainder of the world. Reasonably priced thermal storage might assist industries and cities seize warmth that’s at the moment wasted, in addition to stability the inconsistencies in wind and solar energy output. However whereas Polar Evening Vitality is raring to work immediately with potential clients, they understand that the challenges forward are too massive for them to deal with alone.
Tommi Eronen, CEO of Polar Evening Vitality.
“We wish to license this expertise. In case you function an influence plant, please contact us,” Eronen says with fun. On a extra severe notice, he provides, “We’ve to get away from all types of combustion, even biomass. We have to defend and restore forests to allow them to preserve eradicating carbon from the air. As a result of local weather change is occurring so quick, we would like our concepts to unfold as rapidly as doable.”
Reference
Statistics Finland, “Over one-half of Finland’s electrical energy was produced with renewable power sources in 2020”, November 2021.
