UC Researchers Receive Nearly $3.5 Million from DOE to Reduce Water Footprint

By:       Ashley Duvelius
Date:    April 26, 2016     

CEAS researchers, Raj Manglik and Milind Jog, have been awarded nearly $3.5 million by DOE ARPA-E to develop an innovative air-cooling system for thermoelectric power generation that eliminates the need for local water resources, therefore greatly reducing our water footprint.

Walter M. Higgins combined-cycle gas-burning electric generating station in Primm, Nevada (near Las Vegas, NV), with the dry, and water-scarce arid terrain in the background

Walter M. Higgins combined-cycle gas-burning electric generating station in Primm, Nevada (near Las Vegas, NV), with the dry, and water-scarce arid terrain in the background.

Every year, some 580 billion cubic meters of freshwater are withdrawn for energy production, which makes up about 15% of the world’s total water withdrawal, second only to agriculture. One of the primary culprits of this whopping water footprint are water-cooled thermoelectric power plants as they withdraw 60 billion to 170 billion gallons of freshwater from rivers, lakes, streams, and aquifers—on a daily basis.

First of all, it is important to differentiate between withdrawal and consumption in regards to energy production via power plants. Withdrawal is the total amount of water a power plant takes in from a source such as a river, lake, or aquifer, some of which is returned. Consumption is the amount lost to evaporation during the cooling process. Of the 60 to 170 billion gallons of freshwater that power plants withdraw daily, 2.8 to 5.9 billion gallons are consumed and therefore, wasted.

And that is where the University of Cincinnati comes in. Out of the ten projects selected to be funded by the Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E), College of Engineering and Applied Science (CEAS) Department of Mechanical and Materials Engineering professors, Raj M. Manglik, PhD and project PI, and Milind A. Jog, PhD and project co-PI, were awarded the largest grant support with nearly $3.5 million to develop their “Enhanced Air-Cooling System with Optimized Asynchronously Cooled Thermal Energy Storage.” Through this project, Manglik and Jog will develop an enhanced air-cooled condenser and cool storage system that will eliminate the need for power plants to draw from local water resources, significantly reducing our water footprint.

Raj Manglik, PhD

Raj M. Manglik, PhD

How will this work? Well currently, power plants are operating at about 40% efficiency while the remainder of the energy is converted to low-grade waste heat that must be removed to maintain the plant’s efficiency. Most power plants use water from nearby rivers, lakes, or the ocean for cooling. The water may pass directly through tubes inside the plant's steam condenser, and then be returned, warmer, to the original source, or it may be cooled by allowing some evaporation in a cooling tower so as to carry off the heat in water vapor. You know that smoke you see rising out of power plant towers? That’s not smoke at all—it’s evaporated water.

And in areas with limited water or under drought conditions, dry-cooling systems use air to remove heat from the plant's condenser so as to condense the steam inside. However, present dry-cooling technology reduces the power plant's efficiency and requires costly equipment.

Manglik explains, “Just look at Lake Mead, it has been losing water for over a decade and is currently at about 40% capacity. With water supplies becoming increasingly strained in many areas, especially in California, Arizona, Nevada, and Utah, economical dry-cooling approaches that do not reduce the efficiency of power plans are critically needed. Innovative methods are needed to allow cooling below the daytime ambient air temperature and improve heat exchange between air and the plant's recirculating condenser water will provide the keys to ensuring the continued efficiency of power generation while decreasing the burden on water supplies.”

Milind A. Jog, PhD

Milind A. Jog, PhD

Manglik and Jog’s dry-cooling system, featuring an enhanced air-cooled condenser and a novel daytime peak-load shifting system (PLSS), will enable dry cooling for power plants even during hot days. The team will transform a conventional air-cooled condenser by incorporating flow-modulating surfaces and modifying the tubular geometry of the system, both of which will reduce heat transfer resistance and increase the thermal surface area. Whenever the air temperature becomes too high for the air-cooled heat exchanger to be effective, the PLSS will cool the air inlet temperature back down to acceptable temperatures. This inlet air-cooler technology removes heat from the incoming air and stores it in a thermal energy storage (TES) system that incorporates phase-change materials, which can store and release heat over a range of temperatures. During periods when the ambient air is cooler, the TES will release the stored heat to the atmosphere or to another waste-heat recovery system.

Manglik continues, “If successful, our enhanced air-cooled condenser and cool storage system will enable more efficient dry cooling, even in the hot, desert-like temperatures we have in Nevada and Arizona. Power plants can maintain energy efficiency by using our air-cooling technology instead of water cooling when water use is restricted. And since this design results in no net water consumption for cooling, the need to draw on local water resources will be eliminated.”

Air-cooled steam condenser at the Higgins Plant

An air-cooled steam condenser at the Higgins Plant.

Additionally, UC's heat exchanger and pre-inlet air-cooler are designed to be very compact and occupy a smaller footprint, which helps to lower the technology's cost to the point where it would be immensely commercially attractive.

Manglik reflects, “Our team once visited a large power plant out in the desert in Nevada, near Las Vegas, and I still remember vividly how evident the water scarcity was for that region. Simply looking at the barren terrain was shocking and reaffirmed the need for our air-cooling system. It also validated the Water-Energy Nexus: we truly need to further evaluate and reframe our relationship between energy and water resources. Our future depends on it and I couldn’t be more pleased to be a part of that conscientious forward-thinking path.”

About DOE ARPA-E

The Advanced Research Projects Agency-Energy (ARPA-E) advances high-potential, high-impact energy technologies that are too early for private-sector investment. ARPA-E awardees are unique because they are developing entirely new ways to generate, store, and use energy.