Denver has a plan to heat and cool buildings without fossil fuels. It involves… sewage!
Denver plans to heat and cool a cluster of downtown buildings using a thermal energy network, which will repurpose the city’s old steam system into an “ambient loop” of interconnected buildings. The network will utilize water-source heat pumps, geothermal energy, and excess heat from sewage to provide efficient and sustainable heating and cooling. The pilot project, starting with a few buildings, aims to decarbonize the downtown core and serve as a model for other cities. Read on for more.
Denver is developing an innovative plan to reduce climate pollution by replacing fossil-fuel- based heating and cooling in downtown buildings with a cleaner thermal energy network powered by water, geothermal energy, and even sewage heat. Buildings are Denver’s largest source of greenhouse gas emissions, largely because of the natural gas used for heating and cooling skyscrapers.
At the center of the project is the old Cherokee Boiler House, a historic steam plant near downtown Denver. Although the building currently appears abandoned and outdated, city officials see it as the future hub of a modern low-carbon energy system. Denver aims to eliminate greenhouse gas emissions by 2040 while also lowering long-term energy costs for taxpayers. The city plans to replace parts of its aging steam heating system — one of the oldest continuously operating commercial steam systems in the world — with what is called an “ambient loop.” The current steam network is inefficient, expensive to maintain, and dependent on fossil fuels. Costs for customers have risen sharply over the last decade due to maintenance needs and rising fuel prices.
The new thermal network will connect buildings through underground pipes filled with water circulating at moderate temperatures. Individual buildings will use highly efficient water-source heat pumps to either extract heat from the loop for warming or dump excess heat into it for cooling. Because all the buildings are connected, waste heat from one building can help warm another, improving efficiency across the system.
Initially, the project will connect 11 city-owned buildings, beginning with a smaller pilot involving two buildings and a snowmelt sidewalk system. By 2030, Denver hopes to expand the network to nine buildings and eventually many more.
To keep the circulating water at the proper temperature, Denver plans to use geothermal energy by drilling deep underground boreholes beneath parking lots. Water pipes will exchange heat with the Earth, creating a renewable energy source that functions somewhat like a thermal battery.
One of the project’s most unusual features is its use of sewage heat recovery. Warm wastewater from showers, laundry, and sinks contains large amounts of thermal energy. Denver’s wastewater utility currently releases treated water into the South Platte River while it is still warm. By installing heat exchangers inside major sewer lines, the city hopes to capture some of that wasted heat and feed it into the thermal loop.
The project is expected to cost between $280 million and $320 million over the next decade, but city officials believe it could become a national model for decarbonizing dense urban downtowns.
Read the entire article with photos from NPR at the website below: