New Mexico State University engineering students have been assessing how a cutting-edge thermal power technology developed in the cold climes of Sweden might work in our arid environment. Their work may someday lead to an installation of the technology on campus—the first-of-its-kind in the United States and the first in a desert climate.
The project began in spring 2019 when Joshua Epel, energy advisor to NMSU Chancellor Arvizu, and Dann Epel, the U.S.-based representative for Ectogrid, a Swedish company owned by the German electric utility, E.ON., approached the NMSU College of Engineering to partner on a project. Assistant Professor Samah Ben Ayed, who teaches thermal science related courses like, thermodynamics, heat transfer, HVAC systems, and renewable energies, and does research in energy efficiency in HVAC systems, was a perfect fit for leading the project.
The company wanted to determine the feasibility of using a small thermal grid to produce energy for a group of net-zero buildings using their technology. A thermal grid performs the same functions as a traditional electric grid: thermal energy can be shared between buildings or generated at a central station for distribution to facilities equipped with heat pumps or cooling machines. Energy that isn’t used is stored for later use.
“For an electrical grid, energy would be delivered through a cable. For a thermal grid, there would be a hot-water pipe and a cold-water pipe that would deliver energy,” explained Ben Ayed.
“A net-zero energy building is a new, up-and-coming term. It’s very simple,” said Ben Ayed. “It just means that a building is producing as much energy as it consumes. It would have to be very energy efficient for the photovoltaic panels on top to be almost sufficient to provide enough energy for the building’s consumption.”
A net-zero building may produce more energy than it uses with the excess energy going to the electric grid. When customers get the bill from the electric utility, they may have to pay or they may be getting paid. It depends upon how much energy is produced and how much is consumed.
“A thermal grid connecting multiple buildings with diverse energy loads could result in a net-zero energy district, where the buildings take advantage of the district’s excess heating and cooling energy to minimize their overall energy usage and cost,” said Wayne Savage, executive director of Arrowhead Park. “The 3 MW solar array to be installed at Arrowhead Park will also provide supplemental renewable energy to reduce the need for each building to produce its own energy. This is great news for each building owner, but also gives us a unique benefit to use in marketing the park to potential developers and tenants who value energy efficiency and want to be net zero for energy.”
Ectogrid has already developed a prototype community, Medicon Village in Lund, Sweden, that supports more than 1,600 people who work in more than 120 organizations across 15 different buildings.
“They wanted to show that this technology is good and valid and efficient in different types of climates. In Sweden the most important part is heating and not cooling. Is this going to be efficient in a desert climate as well? That’s the question that we were trying to answer through this capstone project,” said Ben Ayed.
She and six engineering students set out to find the answer as their senior capstone—a culminating two-semester course that utilizes application of their engineering studies in a hands-on project. All engineering students are required to complete a capstone project for graduation.
The group began with a study of Arrowhead Park’s multi-year master plan for mixed-use development on the southern end of the NMSU campus. Plans call for the addition of a series of new facilities over the next few years, including Arrowhead Place, a new speculative office building that will provide office space for startup businesses and will be the headquarters for Arrowhead Center.
“It’s going to be a perfect framework for this kind of thermal grid,” said Ben Ayed. “Because Arrowhead is far from central university utilities, they would need to extend utilities to the area. It will likely be very expensive and not very efficient to do this so they will have to have a standalone system. It makes sense to think of this as a small thermal grid.”
During the spring 2019 semester, the students conducted a thermal and cost analysis. Because there are no specifications of the proposed buildings, they used an existing building on campus, Hardman and Jacobs, which is newer and was built with state-of-the-art insulation and construction materials. Using data provided by campus utilities, they analyzed the year-round energy, heating and cooling needs per square foot for a building in Las Cruces.
At the start of the fall 2019 semester, Ben Ayed and the students were hosted by Ectogrid to visit the Medicon Village in Sweden for five days.
“They took really good care of us. They had their crew dedicated to us for three days. They took us on a tour and we’ve seen the central system and the local mechanical rooms,” said Ben Ayed. “You can think all the theories that you want but it’s not like seeing the thing implemented. It was really good for the students and myself to see the system. We were trying to understand the thermodynamics of the system and we were also trying to come up with a model that fits this area for Arrowhead Park’s future development.
“We came back and we started to work. We started to model the existing building after the new technology. We established a dynamic model of what we need for cooling, what we need for heating, and all of the thermal properties of Las Cruces with all the sun we have. Everything was built into that compact model.”
Once they determined the annual consumption of heating and cooling, they analyzed the efficiency of the system, the capital cost of the equipment and the operational costs. The first stage analysis yielded promising findings. According to Ben Ayed, additional data needs to be considered for the rigor of the next stage analysis. Their preliminary findings indicate that initial capital costs would be recovered within the first few years of operation. Ben Ayed hopes to get approval for further analysis and eventually an installation of Ectogrid as part of the Arrowhead Park development.
Aside from working on a project that may prove useful to NMSU, the students benefitted from working on an applied research project in the role of consultants. They worked with a real client and had the responsibility of delivering information that is used in determining whether the project will be pursued further.
The students presented their final report to NMSU Chancellor Dan Arvizu and members of the NMSU Energy Cabinet. Arvizu, formerly director of the National Renewable Energy Laboratory, is very supportive of the project.
“The work performed by the students under the supervision of professor Ben Ayed exemplifies the best of NMSU: professional quality work that demonstrates the students are prepared and ready to contribute immediately in whatever engineering field they are employed in,” said Chancellor Arvizu.
“The capstone project and the planning for Arrowhead Park Extension illustrates that NMSU is poised to lead New Mexico and the Southwest in pioneering cost effective, clean energy solutions that will shape the future.”