Geothermal Gives Back

How Southeastern Louisiana University is saving on their energy costs with their recently completed housing facilities

by Ryan Faulk, AIA, NCARB, CSI

Since 2004, Southeastern Louisiana University has made a commitment to sustainability and energy efficiency in a time where energy costs were increasing, and funding was dwindling.  The latest addition campus is no exception with the recent completion of Ascension and Twelve Oaks Residential Halls.

These on-campus housing buildings total 169,000 sq. ft. and save the University a projected $107,500 per year in operational cost compared to their older on-campus housing stock.  This represents a projected 25% decrease in their energy costs achieved primarily by a unique air conditioning system using hybrid geothermal energy. 

Recently completed Ascension & Twelve Oaks Halls at Southeastern Louisiana University. 4 Story, 553-bed facility with amenity filled community spaces.

Photo Credit: University Communications and Creative Services Photographer Randy Bergeron

History

Southeastern Louisiana University began developing an energy strategy in 2004 to lower operational costs, starting with more responsive and centralized HVAC control for all university facilities and experimentation with various alternative energy sources, coupled with creative methods to reduce energy usage. 

In an effort led by Physical Plant director Byron Patterson, Southeastern established their Sustainability Center in 2012, which is currently led by Alejandro Martinez, and which leads initiatives such as solar hot water systems, conversion to LED lighting, biodiesel production for maintenance vehicles, and most recently a push to develop a biomass generator to convert landscaping waste material into electricity. 

Technology

Traditional geothermal HVAC systems simply use the stable ground temperatures to transfer heat between the building and the ground. No ground water is removed or introduced into the earth in this process; instead, water is circulated through the well field and building piping to either heat or cool the building.

This process is more efficient than air transfer of heat utilized in typical heat pump systems, such as an outside condensing unit, which rejects heat to the air.

Average ground temperatures

A Southern Twist

South Louisiana’s climate, like many areas of the southeastern United States, has many more days that require cooling rather than heating due to the relatively mild winters and long summers (cooling is needed for approximately 70% of the year). However, during the majority of the year, the building will need less than 80% of the full cooling load required. Additionally, traditional geothermal systems in this type of climate loose efficiency over time because the ground becomes overcharged with heat during the summer months.  This excess heat cannot be fully dissipated during the relatively short winter period and results in a system life expectancy that is less than that of the building they serve. 

Annual mean total cooling degree days

The Project team of Southeastern Louisiana University, Holly & Smith Architects and Salas O’Brien, in partnership with Metro Mechanical, Inc., developed an approach that merged traditional commercial HVAC system components with those of a geothermal system to create a hybrid that is uniquely suited to the climate and soil conditions of the Project site.  The resulting system maintains the traditional geothermal system components but adds a high efficiency cooling tower (fluid cooler) and boiler coupled with an energy management system. 

Geothermal System Diagram

Metro Mechanical, Inc., a regional mechanical contractor with a significant body of work at Southeastern, has been developing this type of geothermal system approach commercially for more than 10 years.  However, the implementation of this approach to a dormitory building is more complex than typical commercial applications and is reported to be the second-largest hybrid geo-thermal system in the United States [Climate Masters 2018].

System and Function

The system can handle a maximum cooling load of approximately 290 Tons.  During peak cooling times, the system is designed for the geothermal wells to address 80% of the cooling need, with the remaining 20% carried by the cooling tower which is typically run at night when heat transfer is most efficient to discharge excess heat from the system and pre-cool the earth when necessary for the next day. Diversity of the heat load within the buildings also serves to increase efficiency.  This diversity primarily occurs due to sun exposure (one side of the building in sun, while the other is in shade), but also results from the comfort level of different individuals (one person prefers 75°, while another prefers 70°).

Another benefit of utilizing a hybrid geo-thermal system was the ability to phase the construction of the project.  Half of the geothermal well field was located in an area occupied by an existing dormitory building, which could not be demolished until students were moved into the new Ascension and Twelve Oaks Residential Halls.  Because only 45% of the well field could be installed at the time the buildings were occupied, the hybrid geothermal system allowed the required project phasing to successfully occur by utilizing the cooling tower to fill any spikes in the cooling load in the late summer, and the boiler to address any spikes in the heating load during the winter.

Well field diagram with wells at 20'-0" on center

Energy Use

With less than half of the well field active, the resulting energy savings are impressive. 

The new facility (shown orange above) averages approximately 24% less electricity usage per square foot when compared with current existing student housing on site (shown in blue).

The new facility (shown orange above) averages approximately 55% less natural gas usage per square foot when compared with current existing student housing on site (shown in blue).

The Energy Use Index is a metric combining all energy use for a given building (kBtu/sqft/yr). Based on the actual energy usage, this facility is within the top 8% of buildings of similar type within our approximate climate zone.

The $107,500 annual savings realized so far have been achieved using less than half of the total designed well field, and the system is projected to pay for itself in approximately 9 years. 

Since the remainder of the geothermal wells came online in May 2019, we expect to see Southeastern Louisiana University achieve better efficiency and some additional savings over the coming months…..STAY TUNED!

H/S EXPERIENCE

 Holly & Smith Architects is pleased to be part of this successful project. We have worked closely with the University to address all of the needs discussed herein. We are proud to say that it has been an honor to be a part of this process.  

As human beings, we spend our personal and professional time within the built environment. As Architects, we are privileged to create spaces where people can gather, live, learn, work, eat, sleep and worship. Therefore, it is incumbent that we design spaces that enhance the quality of life and nurtures a greater passion for living. Our design approach is influenced by the environment, culture and community in which architecture exists. To take it further... We Design for Life.