A 1,600-foot steam line, constructed as a joint venture between Hennepin County and NRG Energy Center, Minneapolis, supplies steam produced at the Hennepin Energy Recovery Center (HERC) to NRG Energy Center's downtown district heating system and Target Field.

The steam line supplies the equivalent annual natural gas needs of 1,500 households to downtown Minneapolis and Target Field.

How does the steam line work?

Solid waste, which is considered a renewable source of energy, is burned at HERC to produce high-pressure steam. Most of this steam is used to turn a turbine that produces electricity. A portion of the steam is diverted to the steam line that connects with the NRG Energy Center’s downtown district heating system.

Benefits of the steam line

  • Producing steam from a renewable and sustainable resource reduces the use of fossil fuels, such as fuel oil and natural gas, to heat and cool buildings. One-third of the steam will be distributed by NRG into the county's district heating system to heat and cool hospital and government buildings.
  • Diverting some of the steam directly to provide heating and cooling - instead of converting it to electricity - improves efficiency of the energy produced at HERC.
  • The steam line creates an interconnected district heating system with energy supplied from multiple sources, increasing the reliability and redundancy of the downtown district heating system and providing a reliable back-up.

The steam line partners

HERC

HERC is located in downtown Minneapolis and burns 365,000 tons of solid waste annually to generate enough electricity to power 25,000 homes. The benefits of energy produced at HERC include:

  • Reducing greenhouse gas emissions. Since opening in 1990, HERC has prevented the release of three million tons of carbon dioxide emissions.
  • Providing valuable renewable energy. The facility helps meet the state’s renewable energy goal of 25 percent of energy from renewable sources by 2025.

NRG Energy Center, Minneapolis

NRG Energy Center’s downtown district heating system provides steam and hot water for space heating, domestic hot water and humidification, and chilled water for air conditioning to more than 100 buildings covering 130 square blocks of downtown Minneapolis through six miles of steam piping and four miles of chilled water piping. The benefits of district heating include:

  • District heating adheres to stricter emission standards than do individual buildings, leading to less air pollution, and can more easily transition to renewable energy sources than can individual buildings.
  • When steam, hot water or chilled water arrives at a building, it is ready to use and 100 percent efficient. Energy produced by burning natural gas or fuel oil on-site is about 80 percent efficient.
  • Individual buildings do not have to store or use fuels, chemicals or refrigerants on-site, making the building safer and more environmentally sound.
  • Individual buildings do not have to install and maintain boilers and chillers, which reduces up-front costs, saves money on maintenance and frees up space that the equipment would otherwise occupy. District energy systems also have the flexibility to use a variety of fuel sources to keep costs down.
  • District heating systems, with built-in interconnections and back-up systems, are typically 99 percent reliable.