A sophisticated heat exchanger solution saves energy in New York

The Bank of America Tower in midtown Manhattan - a LEED certified building, features some of the most sophisticated heating and air conditioning equipment in the world. Among many sustainable and energy-efficient solutions, the building uses Alfa Laval heat exchangers for free cooling, ice thermal storage and combined heat and power generation. The heat exchangers operate in close conjunction with an absorption chiller located three stories below ground.

Free cooling and thermal ice storage

During the five months of the year when outside temperatures are low enough, a cooling tower produces chilled water for cooling purposes. Alfa Laval plate heat exchangers transfer the free cool to the air conditioning system. No or very little mechanical refrigeration is required, which cuts the use of electricity dramatically. In summer, the system switches to an ice thermal storage solution. At night, when the price of energy is low, the absorption chiller cools a closed ethylene glycol loop, which produces ice for storage in huge tanks. During daytime, the cycle is reversed and water from the melting ice is used to cool the building’s air conditioning system. Alfa Laval plate heat exchangers are used to separate the glycol, water and air conditioning loops.

Heat recovery in a combined heat and power plant

The building is also equipped with a combined heat and power plant that uses Alfa Laval heat exchangers to distribute the heat throughout the entire building, while generating 75 percent of the total electricity used. The hot exhaust gas from a turbine engine is recovered in a boiler that produces steam. The turbine generates electricity, while the steam is used to heat the building during winter and to run the absorption chiller during the rest of the year.

Substantial energy savings

By combining three modern technologies – free cooling, ice thermal storage and combined heat and power generation, Bank of America greatly reduces its use of energy and emissions of CO2. As an example, the heat recovery system is able to capture 70% of the energy contained in the natural gas used – compared to only 30% in a typical utility plant.