Contemporary innovation in the field of energy seems to be all about finding power in sources that are all around us, such as the sun and wind. Researchers at Pennsylvania State University have taken that idea one step further having found a way to harness electricity from thin air.

More specifically, the scientists have developed a method to harness electricity from ambient magnetic fields generated by everyday household appliances.

Reporting in the journal “Energy and Environmental Science,” they note home devices, and especially the cords that supply electricity to them, generate small magnetic fields that otherwise dissipate into the air around them.

The scientists have developed a new mechanism capable of harvesting this wasted magnetic field energy and converting it into enough electricity to power next-generation sensor networks for smart buildings and factories.

One of the study’s co-authors, Shashank Priya, professor of materials science and engineering and associate vice president for research at Penn State, says the device he and his colleagues developed “allows for achieving high power density under low amplitude magnetic fields.”

He and his team designed paper-thin devices, about 11/2 inches long, that can be placed on or near appliances, lights or power cords. They used a composite structure by layering two different materials together. One of these materials is magnetostrictive, which converts a magnetic field into stress, and the other is piezoelectric, which converts stress, or vibrations, into an electric field. The combination allows the device to turn a magnetic field into an electric current.

The devices have a beam-like structure with one end clamped and the other free to vibrate in response to an applied magnetic field. A magnet mounted at the free end of the beam amplifies the movement and contributes toward a higher production of electricity.

In testing, when placed 4 inches from a space heater, the device produced enough electricity to power 180 LED arrays, and at 8 inches, enough to power a digital alarm clock.

According to the scientists, the technology has implications for the design of smart buildings, which will require self-powered wireless sensor networks to do things such as monitor energy and operational patterns and remotely control systems.

Public support for solar power is strong and growing, but it’s not always strong enough to overcome the high upfront costs of installation. To help home and business owners make that initial investment towards utilizing solar power, Philadelphia re-opened its popular Solarize Philly program.

In April, Solarize Philly began accepting to new applications. The last phase closed in November 2019 after 2,068 signups. The program has helped 6,200 customers since its launch in 2017.

Program participants benefit from group-buying discounts and consumer protections. Installers are kicking off the new phase by providing free remote solar assessments.

The program is run by the Philadelphia Energy Authority (PEA), an independent municipal authority chartered by the city in 2010 to provide targeted expertise and focus to city efforts to reduce energy consumption and expense.

The authority offers other financial incentives that are available to Solarize Philly participants. The Philadelphia Solar Rebate offers a one-time rebate incentive of 10 cents/watt to commercial and 20 cents/watt to residential projects. The rebate comes to about $1,000 for homeowners.

Fees generated by Solarize Philly also support the PEA's Solar Savings Grant Program, which provides grants plus financing to low- and moderate-income households to go solar at no upfront cost. Grants cover up to half the cost of the project, and utility bill savings start in the first year.

To participate in Solarize Philly, homeowners complete a sign-up form and are then connected to one of the city's approved installers. An installer will provide a free project proposal tailored to the home’s specific needs, based on roof space, electricity usage and other factors.

After the owner approves and signs a contract, the installer handles all permitting and engineering requirements and works with the local utility, PECO, to manage the interconnection process before the installation.

The city says Solarize Philly is also helping create jobs. Darell Clarke, city council president, said “of all energy projects, rooftop solar creates the most jobs per dollar invested.”

The PEA references a study conducted for the authority by the American Council for an Energy Efficient Economy, which found that 15 living wage jobs are created for every 100 solar installations. PEA also leads Bright Solar Futures, a partnership with the School District of Philadelphia to establish Pennsylvania’s first vocational solar program for high school students.

Is the fire alarm too loud? If you’ve ever been asked this question, you may have wondered whether the questioner had a point or not.

First I reviewed the Underwriters Laboratories (UL) listed horn available on the market today. Currently, the standard commercial horn sounds at a measured decibel output (by UL) in the ranges of 87 dBA to 95 dBA measured at 10 feet from the sound source in the UL anechoic chamber (no reverberation). All of these appliances sound at a frequency of approximately 3,000 Hertz (Hz).

Based on research over the last 10 years, the very young and the very old have difficulty hearing that frequency level. That research also showed that hearing a fire alarm signal at 520 Hz was equally heard by the very young, the very old and those who needed awakening at night. Based on that research, the code changed the requirements for audible alarm appliances in all sleeping rooms to be at that frequency.

Keep in mind the requirement for audibility in these areas remains at 75 dBA measured at the pillow level in the bedroom. To awaken occupants the audible appliances must produce a low frequency alarm signal that complies with the 520 Hz requirement. The Annex A information also provides guidance for areas “intended for sleeping and in areas that might reasonably be used for sleeping. For example, this section requires a low frequency audible signal in a bedroom of an apartment and also in the living room area of an apartment as it might have sleeping occupants.”

The annex does advise us that it is not required to use the low frequency signal in the hallways, lobby and other tenantless spaces. For example, in hotels, the guestrooms would require use of the low-frequency signals, but other spaces that might require audible signals could use any listed audible appliances regardless of the frequency content of the signal.

The code requires a minimum of 15 dBA above the ambient sound levels present in the space. The bottom line is the audible signals are not too loud but must be loud enough to move the occupants to take action.

Still you may come across customers who are concerned that the volume of an alarm could negatively affect their hearing. For example, I have been asked by a principal of a K-12 school what her response should be to parents who are worried the alarm signal is so loud it will injure children’s hearing.

To answer the principal’s questions, first I turned to the information provided in the annex of NFPA 72-2019, National Fire Alarm and Signaling Code. Annex A for Section 18.4.1.2 discusses the maximum sound pressure level of 110 decibels (dBA) permitted in a space. In the 2007 edition, this was reduced from 120 dBA in previous editions.

According to NFPA 72, “the change from 120 dBA to 110 dBA was made to coordinate with other laws, codes, and standards. In addition to the danger of exposure to a high sound level, long-term exposure to lower levels could also be a problem.”

For example, when occupants must traverse long egress paths to exit or technicians test large systems over extended time, the exposure to loud alarm signals could cause damage to their hearing.

The issue is the code is silent on how long a person can or should be exposed to an audible notification system. The limit of 110 dBA has been set as a reasonable upper limit by the code for the optimal performance of a system.

The annex goes on to say, “For workers who could be exposed to high sound levels over the course of a 40-year employment history, OSHA has established a maximum permitted dose before a hearing conservation program must be implemented. A worker exposed to 120 dBA for 7.5 minutes a day for 40 years might be in danger of suffering a hearing impairment. The OSHA regulation includes a formula to calculate a dose for situations where a person is exposed to different sound levels for different periods of time. The maximum permitted by the regulation is an 8-hour equivalent dose of 90 dBA. It is possible to calculate the dose a person experiences when traversing an egress path where the sound pressure level varies as he/she passes close to, then away from, audible appliances. Table A.18.4.1.2 depicts OSHA permissible noise exposures.”

I used the above information to assure the principal that the short duration of the students’ exposure to the alarm signal was not going to cause hearing damage. In addition, the sound pressure levels in the hallways of her school did not come close the maximum of 110 dBA allowed by the code.

All in all, you can tell your customers that alarm systems are loud by design. The uncomfortable volume during egress should be short-lived and well worth it to help as many occupants as possible be spared more serious injury or harm.