New technology reduces water use by up to 80 percent
This article is sponsored by Johnson Controls.
Because I’ve worked in the cooling tower industry for more than 30 years, every time I fly or drive into a city on a cool day, I’m searching for wasteful plumes.
Those are the puffs or clouds you see coming from cooling towers on cityscapes, from Seattle to New York. They’ve been around for decades, a silent reminder of the millions of gallons of water wasted each year as we seek to provide cooling for offices, factories, data centers and even power plants.
Now Johnson Controls has developed a technology that could turn the reduction in plumes into a positive signal that we’re actually saving an astonishing 25 to 80 percent of water usage in comparison to all-evaporative heat rejection systems. Working in conjunction with the National Renewable Energy Laboratory and the Electric Power Research Institute, this new technology is being tested in actual field applications.
BlueStream hybrid cooling technology
Like fanning away sweat on a hot day, open cooling towers reduce the temperature of water heated in chillers, industrial processes, data centers and other high-heat practices. Through a "wet" process, the warm water is sprayed over the fill in a cooling tower to increase the contact area, and the heat is removed through evaporation.
A constant supply of water is needed to replace the water evaporated from the cooling tower, but in many regions, continuing droughts and increasing competition for this vital resource limit water availability. Additionally, some water continuously is bled from the system to reduce the buildup of undissolved solids as water is evaporated. This generates a large wastewater stream, often containing many additional water treatment chemicals.
We are testing a new approach with very promising results: the BlueStream hybrid cooling system. Used in conjunction with a traditional cooling tower, a hybrid cooling system offers a way to not only reduce environmental impact, but also lower operating costs and increase the resiliency of critical operations.
The system offers "dry" cooling, using a thermosyphon process, in which refrigerant circulates naturally, with no need for a pump or compressor. Intelligent, web-connected controls coordinate the operation of both the wet and dry system components and adjust in all weather and thermal load conditions for optimum efficiency, using "wet" cooling when it’s hot and "dry" cooling when it’s not.
Best of all, because of the connection to building automation systems, building owners can maximize efficiency and have detailed operating information, which allows for better understanding of trends and helps forecast costs.
Certainly there are some limitations. If it’s too hot outside or if the process temperatures aren’t warm enough, it’s inefficient to use dry cooling during these times.
Intelligent buildings make decisions automatically. In addition to responding to changing weather and system load conditions, the controller adjusts the fan speeds for the wet and dry units based on the Water-to-Energy Cost Equivalence Ratio (WECER) — the ratio of water costs to electricity costs for optimum system economic savings.
Tremendous market potential
The current outlook is good in cities with high water prices, such as Atlanta and Seattle, or those with water shortages, such as Phoenix and Dallas. Whether as an add-on to an existing system or designed for new construction, thermosyphon hybrid cooling offers options for significantly reduced water usage while maintaining peak energy performance on the hottest summer days.
The potential is enormous, especially in these areas:
The compound annual growth rate of the global data center construction market is expected to grow 12.5 percent from 2016-2020, according to a 2016 Research and Markets report. Servers and other electronic components within these centers are operating at increased temperatures, which require increased cooling capacity and 24/7 reliability.
Hydropower stations and thermoelectric plants, which depend on water to generate energy, together contribute about 98 percent of the world's electricity production, according to the U.S. Energy Information Agency. Water temperature shifts and lack of fresh water due to climate change could lead to reductions in electricity production capacity in more than two-thirds of the world's power plants between 2040 and 2069, according to the International Institute for Applied Systems Analysis in Nature Climate Change. More efficient cooling drastically could affect power availability and reliability.
Complex industrial/Manufacturing plants
Although water use in U.S. manufacturing is declining, it still totals almost 16 billion gallons per day.
Central Chiller Plants
Large universities, hospitals and office building complexes that commonly handle smaller year-round base loads are ideally suited for thermosyphon cooler applications. For example, a base load of just 500 tons can require between 6 million and 9 million gallons of cooling tower make-up water annually.
While there always has been a focus on reducing energy associated with these plants, rapidly escalating water, wastewater and chemical treatment costs represent 20 to 40 percent of the plants’ total utility spend.
A 2014 study (PDF) presented at the International District Energy Association’s 27th Annual Campus Energy Conference showed that installing thermosyphon cooler systems to a 500-ton, base-loaded central plant allow the facility to reduce its annual water consumption by 1 million to 6 million gallons while simultaneously reducing its total annual utility spend by $5,000 to $50,000. Thermosyphon systems’ modular design offers the ability to add multiple units in parallel to handle a wide range of water conservation requirements.
The urgency is growing stronger to act. Businesses are concerned about their vulnerability to water restrictions, along with the accompanying operational, productivity and economic risks (PDF). And recently introduced federal legislation would direct the U.S. Department of Energy to integrate water considerations into its energy research, development and demonstration programs and projects by among other things, improving the understanding of the water required to provide reliable energy supplies.
Water is a precious resource. Through BlueStream hybrid cooling technology, we truly have the potential to make a huge difference by reducing our impact on the environment and freeing up water for more critical uses.