Retrofitting older multi-stage steam turbines with state-of-the-art controls, single-stage compressors and other technologies can improve the performance of existing steam turbines, often at a fraction of new chiller installation costs.
As home to the largest higher-pressure district steam system in the world, New York City’s Borough of Manhattan system provides an ideal test case for upgrading the performance of steam turbines. While different optimization options exist for steam turbine chillers, this article will focus on advanced controls, replacement drives and other upgrades that improve chiller operation.
Many buildings, large industrial sites, public and private campuses, and cities use distributed high- pressure (HP) steam systems for heating and cooling. The Manhattan underground system distributes HP steam at ±175 psi, from cogeneration and boiler systems to supply a significant amount of the Borough’s steam requirements. Over 50% of the summer district steam largely used for cooling in steam turbine or absorption chillers is now cogenerated.
Cogeneration uses the by- product heat from electric generation to significantly improve fuel usage, reducing both pollutant emissions and carbon footprint. A fossil fuel cogeneration plant can be up to 75% efficient in generating electricity, as compared to 35% +/- for a typical, remote, fossil fuel electrical generating station, when one includes the plant and transmission losses. Significant incentives and good practice avoid the use of limited electricity at peak demand. Until the electric grid becomes largely supported by renewable wind and solar energy, which may not happen for decades, other strategies to reduce our fossil fuel use must be employed.
