Marc Edwards, the Charles P. Lunsford Professor of Civil and Environmental Engineering in the Virginia Tech College of Engineering, originated the efficiency study of the systems as part of an undergraduate design class six years ago. After a thorough analysis, the class concluded the claims as false, and that it “was thermodynamically impossible for these systems to save energy as claimed,” said Edwards.
. The results are presented in a paper published in the most recent issue of Journal of Green Building.
Brazeau, now an assistant professor of environmental science at Metropolitan State University of Denver, examined the energy and water savings of continuous hot water recirculating systems in a comparative, direct test versus traditional hot water systems in which consumers often wait for the cold water to flush down the drain before the water warms to a comfortable temperature for showering.
She found that the recirculation systems used 20 percent more energy even in the best possible scenario in which the water pump was only on for a few seconds before use, and in scenarios where the pump was always on, the recirculation systems could require more than double the energy to operate. The consumer pays for this extra energy in higher electric and fuel bills.
“Randi demonstrated that when all energy costs are accounted for, including that necessary to run the pump, the hot water recirculating systems always used much more energy than the conventional systems,” said Edwards.
A previous U.S. Department of Energy report and certain manufacturers claimed the recirculation devices would not only eliminate wait times, but also would save both water and energy. It also was assumed that because consumers did not need to wait for water to warm, the hot water recirculation systems would at minimum save water from being wasted. But that claim did not consider that it takes water to make energy, said Edwards.
The research found that the “so-called green” hot water recirculation systems used more net water than the conventional systems after accounting for water needed to produce the extra energy. “These are really consumer comfort and convenience devices, a luxury really, masquerading as ‘green’ or environmentally conscious devices,” Edwards said.
Other findings: On-demand electric systems operate with nearly 100 percent energy efficiency, but cannot be used in many circumstances dependent on scaling and incoming water temperature, and may require expensive upgrades to home electrical systems and use of low or ultra-low flow showerheads.
In many cases, hot water recirculating systems touted as “green” are not just a consumer choice, but required in some new homes and businesses in the United States, said Brazeau. But their energy savings, and therefore lessened environmental impact claimed by manufacturers “do not hold water,” she added.
Brazeau and Edwards calculated that a typical consumer with an electric water heater would pay as much as $158 more annually compared to systems without recirculation. More research, though, is necessary to better inform policy and decision-making by regulators, public health officials, manufacturers, and consumers, Edwards and Brazeau said.
Steven Mackay | Newswise
Producing electricity during flight
20.09.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
Solar-to-fuel system recycles CO2 to make ethanol and ethylene
19.09.2017 | DOE/Lawrence Berkeley National Laboratory
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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