This article, by Molly Deluca, is part of a series highlighting members of the Office of Sustainability’s Experts Database. In a collaboration with instructor Hannah Monroe’s course, LSC 561: Writing Science for the Public, students interviewed campus sustainability experts and produced short feature stories.
For many of us, using energy seems as simple as flicking on a light switch, plugging a phone charger into an outlet or turning the key in the ignition of a car. Because energy consumption is so ubiquitous, it is easy to become detached from the processes underlying energy production. However, these processes necessarily consume natural resources. As a result, ever-increasing demands for energy place a growing strain on these resources.
At UW Madison, the thermal hydraulics laboratory, led by Dr. Mark Anderson, is responding to this challenge by developing engineering solutions to make energy generation more efficient. Anderson summarizes his group’s research motivation saying, “Everybody wants electricity. Everybody wants heat. So how do we do that as efficiently as possible without generating waste heat and waste electricity?”
At a high level, most systems of energy production involve generating heat, heating a fluid, and passing the resultant steam through a turbine to produce electricity. Energy lost in the conversion between heat and electricity – i.e. “waste” energy – consumes natural resources but cannot be harnessed productively. Therefore, moving and transforming heat efficiently is essential to energy generation processes that optimize consumption of natural resources. Efficient energy generation processes have the dual benefit of making energy more accessible while also reducing the environmental burden associated with energy usage.
Thermal hydraulics explores how heat can be transferred through fluids. Anderson and the thermal hydraulics laboratory study heat transfer properties of fluids and leverage these properties to both make heat storage more efficient and to minimize waste heat lost during the conversion between heat and electricity.
One avenue of research in the thermal hydraulics lab centers on using liquid salts for energy storage. Anderson explains, “the same stuff they put on the roads to melt snow. If you heat it up, they”ll turn to a liquid, and then it looks like water, and you can store heat in it.” Unlike water which has a boiling point of 100°C, liquid salts can reach temperatures of 400 – 600 °C before boiling. This increases the amount of heat that can be stored in a given volume. Like coffee remaining warm in a thermos, liquid salt in an insulated tank can store heat for several days. This heat can then be extracted as needed to power processes that require energy.
Liquid salt research in the thermal hydraulics laboratory spans all stages of development: from developing methods to produce different types of liquid salts to measuring their thermal properties to testing how these materials would perform during commercial use. Anderson describes UW Madison as a sort of “living laboratory” for energy storage research, presenting opportunities to test prototype technologies and move “from a lab bench to something that”s closer to a commercial power plant.”
Energy storage is particularly essential to the development of robust renewable energy systems where inconsistent or unpredictable access to natural resources poses a major vulnerability. For example, when relying on solar energy, Anderson explains, “if a cloud comes over, you stop generating electricity.” Therefore, being able to store energy as heat in liquid salts acts “like a battery,” ensuring that energy will always be accessible.
UW Madison has committed to net zero carbon emissions by the university’s 200th anniversary in 2048, and optimally efficient energy processes will play an essential role in enabling the university to reach this goal while still meeting energy requirements. Insight into heat transfer behavior and optimal energy storage methods have broad applicability across a range of renewable energy generation modalities including wind, solar, and nuclear, in addition to carbon-based. For Anderson, “there’s not a silver bullet” when it comes to sustainable energy generation – each method presents challenges and limitations. Rather, by making all of these processes as efficient as possible, we can “make the best use of the resources we have.”