Denver Plans Ambitious Thermal Energy Network to Cut Emissions
Denver is moving forward with a plan to build a thermal energy network for downtown buildings, using an ambient loop of water, geothermal boreholes, and heat from sewage. The network will replace part of a gas-fired steam system built in the late 1800s, which has become leaky and inefficient. The city aims to cut greenhouse gas emissions to zero by 2040.
How the Network Will Work
The network will connect 11 city-owned buildings via underground water pipes. Each building will have water-source heat pumps to add or remove heat from the loop.
Excess heat from one building can be transferred to others on the loop.
The Cherokee Boiler House will serve as the central hub. Geothermal boreholes—hundreds of them, up to 1,000 feet deep—will be drilled under parking lots to exchange energy with the Earth. Heat exchangers in a major sewage line will capture thermal energy from warm wastewater.
Project Costs and Funding
The network is estimated to cost $280 million to $320 million over a decade. Funding will come from city dollars, a state grant, and potentially bonds or private investment.
A 2025 feasibility report states the loop is up to 75% cheaper than other decarbonization methods for those buildings.
Phased Implementation
The pilot will start with two buildings and a sidewalk snowmelt system in about two years, with nine buildings connected by 2030. Mayor Mike Johnston stated that if successful, the network could be adapted to thousands of natural gas customers.
The 2021 city ordinance requires large buildings to cut emissions.
Wastewater Heat Recovery
The wastewater utility, Metro Water Recovery, currently discharges warm treated water into the South Platte River. The city plans to siphon heat before discharge, saving the utility from having to cool it to meet future state regulations.
Dan Freedman, director of technology and innovation at Metro Water Recovery, said that widespread adoption could follow if the city-scale project succeeds.