BY JERRY BUSH
U
nrecovered waste heat is, well, just wasted, and an expensive waste to pay to heat the sky or pour down the drain. So, wouldn't you say this remarkable source of "free" energy is worth capturing and repurposing? Waste heat recovery is the process of identifying an accessible source of waste heat, implementing a heat recovery system and applying the recovered energy back into the system(s) or facility. Waste heat can be found and potentially harvested anywhere that humans produce and or consume energy. Of all the energy that we produce, we unintentionally waste about 70 percent of it. Where does waste heat come from? Waste heat sources include industrial processes and energy production, mechanical equipment cooling, warm water discharged into the environment, hot gases discharged into the atmosphere (in other words, from industrial processes and boilers), ventilation/ building exhaust discharged into the atmosphere, municipal wastewater and so on. The quality of the waste heat varies by situation and is typically measured by the temperature of the waste heat, accessibility, economic ability to recover and consistency of supply. Data centers, for instance, require a significant amount of energy, 24-7, to maintain an optimal server environment, offering remarkable heat recovery opportunities. Moreover, the investment in data center heat recovery can produce an additional source of income for the data center provider. In addition to renting rack space for servers, the heat that the servers produce can be harvested and sold to a nearby campus, facility or district energy system. For example, the primary source of heat for the Amazon headquarters in downtown Seattle, along with the iconic Spheres, is waste heat sourced from a large data center across the street. The rejected heat is harvested via a large heat exchanger in the data center facility. The data center's hydronic cooling system made this approach possible and effective. The recovered heat from the heat exchanger is conveyed through piping under the street to the building's mechanical spaces. Saving 4 million kilowatt-hours of electricity each year, this relatively small district energy heat recovery system supports the buildings and even an environment that houses more than 40,000 exotic plants inside the glass spheres. It's an outstanding example of what can be done with recovered waste heat.
New tech and regs
While waste heat recovery is not a new concept, new technologies are emerging as a result of the urgency to conform to new code and policy changes, battle climate change and keep up with the world's ever- increasing energy demands. For example, many jurisdictions in the U.S. are proposing or have already implemented policies that reduce and/or ban fossil fuels in certain new and renovated buildings. Combined with customer demand, these policy and code pushes are prompting additional investments in technology and system innovations to offset our current reliance on fossil fuels. Furthermore, some jurisdictions, such as Seattle, are now requiring heat recovery in high-rise residential buildings, with further codes on the way for heat recovery in commercial buildings. Heat pumps are a key go-to system when fossil fuels are not an option. While not commonly thought of as heat recovery units, heat pumps, by design, utilize waste heat by transferring heat in one area of a facility/campus with a cooling demand to another area with a heat demand. Indeed, the economy of scale from sharing reclaimed waste heating among several connected
Of all the energy that we produce, we unintentionally waste about 70 percent of it.
Waste Not, Want Not
GREEN SYSTEMS
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phc May 2022 www.phcppros.com
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