Fwd: Geothermal energy from subways

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Art Hunter

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Aug 17, 2025, 2:20:58 AM8/17/25

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There is even a far more massive geothermal heat harvesting system that is NOT used. The pipes that carry potable water to every building in a city and the waste disposal pipes that move that same water to a recycling facility. Just notice the manhole covers the next time you are out for a walk. They are everywhere. They tell us exactly where these pipes are located.

Water Distribution and Wastewater Collection Systems map. Information includes the locations of watermains, hydrants, valves, manholes, pipes, inlets/outlets, associated facilities and related details.

Wastewater Energy Transfer (WET) refers to the capture and use of heat found within sewer systems. Using heat exchanger technology, energy can be drawn from wastewater to provide low carbon heating and cooling solutions for individual buildings, new developments, and even whole communities.

Community heating strategy | City of Ottawa

Some enterprises produce waste heat which if captured can be used for building heating. These opportunities are typically unique but may prove to be highly feasible.

An example is the use of waste heat from the Kruger Paper mill in Gatineau being used to heat the Zibi development at Chaudière Falls(link is external). Although waste heat sources can be lucrative, care should be taken to ensure that prospective sources of waste heat will continue to be available over the long term.

District energy systems distribute thermal energy to multiple buildings in an area or neighbourhood. Low carbon systems do so by utilizing energy sources which produce low or no greenhouse gas emissions.

These systems typically consist of a heating and cooling centre and a network of thermal pipes connected to a group of buildings. The source of thermal energy can be from a variety of sources. In order to be low carbon, it is expected that either geothermal or WET technologies will be the most common sources.

Low carbon district energy systems are beneficial for several reasons, including:

They can enable solutions that may not be economical on smaller scale
One system can be used to replace many individual gas appliances
They can enable capturing surplus/waste heat from one building to be shared with another

Experience in North American cities suggest that district energy becomes feasible when roughly 1,000,000 square feet of building space is seeking heating and cooling. This is subject to analysis of heating and cooling loads and the architecture of the area seeking an energy system. Typically, district energy systems benefit from economies of scale and being able to exchange energy between locations which need heating or cooling at different times.

Relating this to the community level, district energy systems have good potential to support sustainable thermal supply by growing beyond the area where they are initially established to service existing buildings which are currently employing a combustion-based heating system.

Ottawa has several District Energy System in place and under development today, although not all of them are low carbon. Newer systems are often planned as low carbon from the outset, while older systems require upgrades to transition to low carbon heating fuels. Examples of district energy systems can be found below.

Federal District System

This system, which has been operational since 1918, serves areas of downtown and Tunney's Pasture, primarily serving Federal Government buildings, including the Parliament Buildings. The system provides heat for 80 buildings, and cooling for 67 buildings. The original system is powered by fossil natural gas.

Significant plans are underway to transition to low carbon by 2030. More details can be found on the National Capital District Energy website(link is external).

Zibi

The Zibi Community Utility District Energy System(link is external) – an equal partnership between Hydro Ottawa and Zibi – currently provides net-zero carbon heating and cooling for all Zibi tenants, residents and visitors in the 34-acre riverfront city. Low-grade waste industrial heat is recovered from the neighbouring Kruger tissue mill and injected into the system. In summer, heat is rejected directly or via chillers into the Ottawa River to efficiently produce chilled water to cool the buildings. The plant, which came online in December 2021, currently services three residential buildings and three office buildings totalling 615,00 square feet.

Carleton University

Carleton University’s buildings are served by a district energy system, using steam generated at a central heating plant. The central heating plant is powered by fossil natural gas. In 2018, the process to install a 4.6-megawatt cogeneration system began, with the aim of providing both heat and electricity to the campus.

Carleton University’s Energy Master Plan(link is external) outlines the institution’s plans to achieve carbon neutrality by 2050, as electric boilers will provide low temperature hot water to buildings across the campus.

University of Ottawa

The University of Ottawa’s downtown campus is served by a district heating and cooling loop. The University aims to be a carbon neutral campus by 2040(link is external).

---------- Forwarded message ---------
From: Bloomberg Green <nor...@news.bloomberg.com>
Date: Sat, Aug 16, 2025 at 12:50 PM
Subject: Geothermal energy from subways
To: <art....@gmail.com>

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Today’s newsletter explores an unexpected source of energy: parking garages, subways and other manmade underground spaces. You can read and share a full version of this story on Bloomberg.com. For unlimited access to climate and energy news, please subscribe.

Untapped potential

By Miquéla V Thornton

The heat held in New York's underground labyrinth of infrastructure, from hundreds of miles of subway tunnels to parking garages and malls, is a clean energy gold mine. Now, a Swiss startup wants to tap it to heat and cool buildings, all without drilling a single borehole.

Globally, heating accounts for nearly half of all energy consumption. That makes it a big business, with the potential to become a half-trillion-dollar market, according to a BloombergNEF analysis. Using the Earth’s heat offers one route to cut emissions, but traditional geothermal projects can be costly and require space to operate drilling equipment, making it a poor fit for cities.

Startup Enerdrape’s system uses energy-harvesting panels in manmade underground spaces, though, which could allow it to gain a toehold in cities. The Swiss company focuses on older multifamily buildings, which are harder to decarbonize than newer builds. In New York, residential structures built before 1960 make up over 64% of the housing stock, though not all of it is well-suited for the panels.

Enerdrape’s panels in an underground parking garage. Photo courtesy of Enerdrape

“There really aren’t many companies doing this,” said BNEF analyst Stephanie Diaz. “They are truly a novel approach in how to decarbonize buildings,” though the company will have to figure out how to scale its technology to work with a wide variety of buildings.

Enerdrape’s technology is the product of decades of research spearheaded by Lyesse Laloui, a professor at the Swiss Federal Institute of Technology at Lausanne. A five-time startup founder, he’s spent the last 15 years tackling the question of how to turn underground structures into energy sources.

Initially, he created a solution for new construction, but realized that was a small part of the decarbonization puzzle compared to existing buildings. He and his team developed a prototype heat-exchanging panel in 2015.

The startup’s panels affix to concrete infrastructure, which can hold large stores of heat. (Think of how hot a subway station gets in the summer, for example.) Enerdrape taps that heat using a system of prefabricated panels that absorb geothermal energy from the ground or the air. Even when the subway and other underground spaces aren’t sweltering, the ground temperature, at several feet of depth, stays relatively constant throughout the year.

During the summer, Enerdrape’s system uses the underground as a heat sink to absorb a building’s heat and cool it. In the winter, it does the opposite, using the ground like a battery to warm things up.

The system requires installing one panel for roughly every 110 square feet (10 square meters) of a building’s floor area. The panels are connected to heat-transferring fluid, working in tandem with one or more heat pumps.

“Enerdrape moves heat from where it’s not needed to where it is,” co-founder and Chief Technology Officer Alessandro Rotta Loria said.

The company, which launched in 2019, has projects across Europe, including with Switzerland’s largest retailer, Coop Immobilier, small businesses like a dental office in Spain, utilities and multiple Swiss cities.

It also teamed up with Engie, one of Europe’s largest gas and renewable energy suppliers, to provide energy to 72 homes with Paris Habitat, France’s largest affordable housing provider. Enerdrape said its 145 panels provide 70 megawatt-hours of heat per year and cover 25% of homes’ domestic hot water needs while avoiding 15 tons of carbon dioxide emissions annually. However, the startup faces some challenges.

Heat pump adoption is higher in parts of Europe, and Enerdrape will have to contend with slower adoption in the US due to cost. Upfront cost, which includes panel installation and heat pump connection, is typically between $100,000 and $500,000, depending on a building’s available surface area that can be activated as a heat source. Political headwinds in the US are another issue, with President Donald Trump curtailing federal support for heat pumps.

The system can cut electricity costs, though. According to the company, it can deliver energy at 3 to 4 cents per kilowatt hour, compared to the average US gas price of 17 cents per kWh. Enerdrape says its solution is cheaper in Europe, where fuel costs are 3 to 5 times higher than in the US.

The system also won’t help with larger buildings, which are some of New York’s biggest energy users. “We’re not going to be able to do much” with a 60-floor high-rise, Rotta Loria said.

The majority of New York City residential buildings covered by the law are pre-war construction of six stories or less, according to the Urban Green Council. That provides plenty of opportunities for technology like Enerdrape’s.

Read the full story. Subscribe for more news on greener living.

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