Researchers at EPFL have precisely quantified convection heat transfer in rail tunnels. Using the new model, they estimated how much energy Lausanne could save by fitting the future M3 metro line with a geothermal heat-recovery system, in what would be a world first.
Heat transfer happens in various ways in rail tunnels. For instance, when trains brake or accelerate, they produce heat that warms the surrounding air. That hot air mixes with other air in the tunnel and with heat radiating from the ground.
Until now, engineers have been unable to accurately calculate the amount of heat that tunnel air contains. Researchers at EPFL’s Soil Mechanics Laboratory (LMS) have overcome that problem by precisely estimating the convection heat transfer coefficient. Their findings have been published in Applied Thermal Engineering.
This breakthrough paves the way for innovative applications involving so-called energy tunnels that can supply energy to built environments. The team also tested its model on Lausanne’s future M3 metro line which, once complete, will carry passengers between the city’s train station and the Blécherette district to the north.
Enough heat for 1,500 apartments
“Our research shows that fitting the heat-recovery system along 50–60% of the planned route – or 60,000 square meters of tunnel surface area – would cover the heating needs of 1,500 standard 80m2 apartments, or as many as 4,000 Minergie-certified energy-efficient units,” explains Margaux Peltier, a scientific assistant at the LMS, whose Master’s research forms the basis of the article. The system also allows heat to be stored so it can be supplied to homes when needed. “Switching from gas-fired heating would cut the city’s CO2 emissions by two million tons per year,” adds Peltier. Her calculation does not include the savings gleaned from metro stations or at the planned rolling-stock depot in the north of the city, which could also benefit from the system.
As the temperature naturally stabilizes in underground tunnels, excess heat or cold is evacuated to the surface. The resulting warm airflow can often be felt at metro tunnel entrances. The idea behind the innovation is to harness this surplus warmth in addition to heat naturally present in the ground.
The system works in a similar way to a refrigerator, with plastic pipes containing heat-transfer fluid, or simply water, placed at regular intervals inside the concrete tunnel walls and connected to a heat pump. In winter, cold water will be pumped into the pipes, emerging hot at the surface. The opposite will happen in summer. According to the researchers, the system would be cheap and energy-efficient to install and would have a lifespan of between 50 and 100 years, with only the heat pumps having to be replaced every 25 years.
Heating and air-conditioning
Once equipped, heat from the tunnel would cover up to 80% of the heating needs of local apartments throughout winter, with the shortfall preferably coming from other renewable sources. But what makes geothermal systems like these unique is that they work in summer too. “The tunnel would act like a highly reliable, year-round heating and air-conditioning system,” says Peltier, adding that it would make a real difference to keeping Lausanne’s homes cool during hot weather. The system could even chill the ice rink set to be built in the city’s new Métamorphose eco-district.
“This article underscores the fact that energy-tunnel technology is mature and could be deployed at district-wide scale,” explains LMS head Lyesse Laloui. “It remains to be seen whether Swiss companies are now prepared to take the lead. Globally, we’ve only seen systems like these used on test sections so far.” The researchers have presented their findings to Lausanne’s utility agency (SIL), local public transport operator (TL), the Canton of Vaud, the prime contractor working on the new metro line, and the City of Lausanne.
Learn more: Engineering heat out of metro tunnels
The Latest on: Geothermal heat-recovery system
via Google News
The Latest on: Geothermal heat-recovery system
- Technology Triumph: Track 4A Is POWER’s Plant of the Yearon July 1, 2021 at 10:33 pm
It both delineates a marked advancement for gas turbine technology and integrates it into a larger state-of-the-art system that is ... once-through (OT) heat recovery steam generator (HRSG ...
- Decarbonization Plans to Work in Both Residential and Commercial HVAC Sectorson July 1, 2021 at 4:13 pm
Turner explains that this depends on contractors being prepared to properly incorporate potential heat recovery heat sources, which might include “groundwater, surface water, wastewater, and symbiosis ...
- Illinois University Seeking NRC License to Build Nuclear Microreactoron June 30, 2021 at 9:38 pm
The MMR Energy System is a fourth-generation nuclear energy ... s power and nearly all its heat via two gas turbines, two heat recovery steam generators, and three steam turbine generators.
- Good practice compressed air systems approachon June 30, 2021 at 6:56 am
To view more guides visit: www.ncpc.co.za. This particular feature focuses on the Compressed Air System Best Practice Guide developed by NCPC-SA Quality Manager Tanya Van Zyl. It is important to ...
- How An Engineer Designs A DIY Energy Recovery Ventilatoron June 29, 2021 at 5:00 pm
But given the detailed design of this DIY energy recovery ventilator for his home HVAC system, we’re going to go out on a limb and say he probably knows what he’s doing. For those not in the ...
- Angus Energy PLC - Half-year Reporton June 29, 2021 at 11:00 am
Geothermal The Company engaged a third ... SF05 and SF08, for a closed loop system of heat recovery by producing, and reinjecting, water from the Sherwood Sandstone water bearing layer.
- Half-year Reporton June 29, 2021 at 7:44 am
The Company engaged a third-party report from Soluzioni Hydrocarburi S.A. on the potential to repurpose two wells at the Saltfleetby Gas Field, SF05 and SF08, for a closed loop system of heat recovery ...
- Geothermal system helps home achieve net-zero energy usageon June 24, 2021 at 5:00 pm
With the WaterFurnace geothermal system, the home is designed for heating ... According to Wahl, the house also features a graywater heat recovery system in which the heat from waste water (graywater) ...
- Transsolar Designs a Mechanical System that is a Breath of Fresh Airon June 24, 2021 at 9:17 am
Bucholz McEvoy and Zas Architects' design of the building. It had a very interesting heating, ventilation, and cooling (HVAC) system developed by Integral Group and Transsolar, the innovative German ...
- Researchers receive £1.3m to develop low-carbon energy storage for buildingson June 23, 2021 at 7:47 am
THE University of Nottingham, UK has received £1.3m (US$1.8m) for a project to develop a novel, low-carbon energy storage system to supply cheap, on-demand heat for houses and buildings in UK ...
via Bing News