The Energy-Saving Potential of Cogeneration

By Eric Gabriel

Cogeneration, also called combined heat and power, is a process that harnesses electrical and heating systems in a building to conserve and produce energy by increasing energy efficiency and lowering the demands on electrical and heat utilities.

A cogenerations system produces electricity and heat simultaneously through an onsite microturbine housed in a cabinet the size of a large refrigerator, and is fueled by natural gas provided by a local gas utility. In winter, the heat produced supplements building heating systems; in summer, the electricity produced reduces peak loads during periods of high demand for air conditioning. In many cases, electrical utilities offer discounted rates for buildings with cogeneration systems because such buildings temper demands placed on the electrical grid.

Notwithstanding these benefits, not all buildings should implement a cogeneration plan. These systems are appropriate for buildings with a high electrical load, especially residential buildings with at least 100 dwelling units. Given significant gains in electrical efficiency and reduction in energy costs, cogeneration is especially attractive in areas, such as the northeast, where electrical rates are high.

This concept might seem innovative and cutting edge, but cogeneration has actually been used since the earliest days of commercial power production, ca. 1882, and is now common in modern commercial power plants. In fact, the first commercial power plant in the world, in lower Manhattan, operated using cogeneration. Steam turbines created electrical power, while excess steam was captured to heat neighboring businesses.

A typical modern cogeneration system was installed in 2017 during renovation of a 139-unit residential tower the Bronx, New York City, a project for which GTG provided monthly construction monitoring and field observations. The system works in tandem with new gas-fired steam boilers supplying the cogeneration turbine to produce electrical power, while a heat exchanger harvests excess energy from the heating system and transfers it to the domestic-hot-water system, further enhancing overall energy efficiency.

According to the building’s owner, an analysis comparing energy expenditures in 2013 (pre-renovation) to spending in 2017 (post-renovation) identified whopping decreases in overall energy expenditures of 57% and electrical expenditures of 52%. While these eye-popping results are higher than average, they nonetheless illustrate the significant potential savings realized by these systems. Such cost efficiencies demonstrate that owners of larger projects can rapidly recoup upfront costs of system installation, and sustain long-term savings through the life of these systems.


Project Highlights

Hanac Corona

An affordable senior residential building, containing almost 70 units in eight stories, this project in Queens, New York uses an array of passive-design features, such as airtightness and elimination of thermal bridging, to reduce energy use and increase residents’ comfort. GTG provided pre-construction review and construction monitoring services on behalf of the equity investor and construction lender.

One Theater Square

This project is a mixed-use building containing 245 apartments and a ground-floor retail space. Located in Newark, neighboring the New Jersey Performing Arts Center, it also features a wealth of amenities, such as a fitness center, game room, and business center. GTG provided pre-construction review and construction monitoring services on behalf of the construction lender.

Francis of Assisi

Located in the San Francisco Bay area, this project entails a complete renovation of a 5- and 6-story senior apartment building. The site features many amenities, including an activity room, dining room, offices, and lounge, to name a few. GTG provided pre-construction review and construction monitoring services on behalf of the construction lender.

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