Our Design for the Heating and Cooling System Is Centered Upon Two Energy Storage Facilities

4.42J Design Proposal for the Sloan School of Management

Alexander Popov

Caroline Tien

1. Introduction

This proposal for a new home for the Sloan School of Management aims to create a facility that is efficient and whose innovative energy operation system is apparent from the exterior. The building will consist of planned out floors that are dependent on the function of the space. The facilities for heating and cooling will be located on top of and beneath the building, with the upper facilities carefully integrated into the aesthetic design of the building. We also plan to use the more efficient desiccant wheel, over the more traditional method of cooling and reheating, for the dehumidification system.

II. Heating and Cooling

Our design for the heating and cooling system is centered upon two energy storage facilities located on top of the building and underneath it. The storage facilities will be used for all of the cooling and partly for heating. The heating will be achieved by using a heat pump, integrated into the energy storage facility. To achieve best performance, the building will be well insulated, energy-efficient windows will be used and during the warmer months night cooling will be implemented. To save energy sensors will be installed in the rooms, so that they are conditioned only when someone is using them. A sensor measuring CO2 level will be used to make sure proper ventilation is achieved. At a later phase a photovoltaic system may be build on top of the upper energy storage facility to make use of the solar energy and help cover the need for electricity. Detailed description of the heating and cooling system follows in the next few paragraphs.

The building is divided into two areas for the purposes of the heating and cooling (diag.1). The first area includes the dining facility and IT rooms, located on the ground floor and the underground parking and auditorium. All of these need special air-conditioning as compared to the rest of the building, that’s why they use a separate heating and cooling system. The dining facility and IT rooms will need mainly cooling during the entire year because of the energy released by the equipment used inside these spaces and the larger number of people using them. The dining facility also requires better ventilation because of the smells associated with cooking. As a result its air should not be reused but rather taken out of the building. The IT rooms require lower humidity levels and will use a separate dehumidification facility. The parking will not be heated or cooled and the auditorium needs conditioning less frequently than the other rooms in the building because it will not be used so often.

The second heating and cooling area includes the classrooms, study spaces, offices and other spaces located on the upper floors. Since the classrooms and office spaces will be used mainly between 8am and 6pm, only during this period they will be constantly conditioned. After those hours, as well as during all times in the other rooms, conditioning will be provided only when someone is present in the room. This will significantly reduce the operating time of the heating and cooling systems.

The main advantage of using energy storage facilities is that they electricity can be used mainly at night, when the rates are lower and also make a good use of the lower temperature at night and in the cold months. The energy storage facilities in our case consist of a well insulated tank full of cold fluid and three pipes going through in a way that will insure good heat transfer between the pipes and the fluid (diag.2). The fluid will be water or if cost permits, a fluid that has a lower freezing point and higher specific heat coefficient. The functions of the three pipes are as follow. One pipe will act as the evaporator of the heat pump that will be used for heating the building. Another pipe will be used to move outside air through the tank, to lower the temperature of the water in the winter or at night (diag.3). The last pipe will carry air from the building that needs cooling. The energy storage system on top of the building will also have a smaller tank with warm water that will be used in the summer to provide heating in the morning after the night cooling has ended.

We will look in detail only at the upper heating and cooling system because it’s a little more complicated and the lower system functions in basically the same way. In each room there will be three pipes coming within the same duct and one pipe leaving that will carry out the exhaust air. The three pipes will bring respectively cold, warm, and outside air when needed. The cold air will come at the lower comfort temperature for the time of the year and the warm air will come at the higher comfort temperature. Depending on the temperature inside the room, the right pipe will be opened until the temperature gets to the middle of the comfort zone. The outside air pipe will be opened when CO2 level gets very high. On top of the building there will be a control station that will make sure there is enough air flow in the three pipes, that the air has the specified temperature, and that it has the right humidity (look at the section about humidity for more information about this system). On diag.4 you can see how the pipes come together and how the air moves. On diag.5 you can see the same information for the lower energy storage system.

During the night there will be night cooling. Outside air will come in through the pipe specified in the previous paragraph to cool the building. During the winter there will be only an hour long cooling for better air quality in the building.

III. Dehumidification

Controlling humidity is essential for protecting building components, optimizing productivity by maintaining an optimal comfort level, preserving human health, and minimizing mold growth. Traditionally, to control excess humidity in a building, companies employ a cooling system that cools the air in order to reduce its ability to retain moisture and then reheat it again to obtain a desired comfort level. However, this is not a very cost or energy efficient process. In addition, many buildings must be maintained at a very low temperature in order for this system to work.

There is now a way of using desiccants to produce a better, more efficient way to dehumidify a building. Many recent studies have shown that it is a very effective moisture control technique that also maintains low electric levels.

In this process, humid air is passed through a wheel, releasing its moisture to the desiccant (i.e. silica gel, titanium gel, natural zeolites). Because the moisture extraction is an exothermic process, the leaving air is usually cooled upon exiting the wheel, either by a heat exchanger or cooling coils. However, unlike in traditional dehumidifying processes, the cooling coils need only to cool the air instead of being responsible for dehumidifying as well. Because the wheel operates independently of the cooling coils, humidity is independent of temperature. Thus, the building can be maintained at a higher, more comfortable temperature than if it was using the traditional cooling/reheating technique to dehumidify.

The desiccant wheel will become saturated as it adsorbs more moisture. At this point, the wheel rotates slowly into the “reactivation air”. This is air that has been heated, and so, as it passes through the wheel, it raises the wheel’s temperature, which moves the moisture in the desiccant to the surface where it then enters the air stream. This moist air then leaves the wheel and eventually the building.

While this process of dehumidifying seems like an excellent alternative to the traditional method, it will be reviewed in more detailed in the weeks ahead to find a way to best integrate it into the proposed building’s circulation design.

1. Final Remarks

Our proposed building is centered on the idea of an economically and environmentally efficient operating system. The heating and cooling systems will be integrated into the ultimate overall architectural design of the building. In addition, to provide an optimal comfort level, a desiccant wheel will be used for dehumidification. While the building’s design has not yet been finalized, we will continue to extensively build upon our initial concepts and findings.