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Energy-Harvesting, Wireless Automation

Oct. 3, 2012
Batteryless systems becoming increasingly popular in building monitoring and control

2012 has been a year of blistering heat, wildfires, and drought throughout much of the United States. With the specter of climate change looming, experts believe such extreme weather events will only become more common. As temperatures increase and population grows, demands on the already strained power supply will lead to increased occurrences of brownouts and rolling blackouts.

With fossil fuels having fallen out of favor, nuclear increasingly viewed as risky, and renewable energy nowhere near the point at which it can take the place of coal, one has to wonder how the growing need for power will be met. In the minds of many, energy efficiency is a vital strategy to mitigate energy-related demand and curb the impact the rising cost of electricity has on bottom lines everywhere.

In buildings, which represent 40 percent of our total energy requirements, automation and control technologies play a key role in efforts to reduce energy consumption. Energy-harvesting, wireless systems, which require no maintenance and provide a high degree of flexibility in system planning and implementation, are becoming increasingly popular in building monitoring and control.

Cooling the Economic Engine of Growth
Nearly all of the world’s booming cities are located in the tropics. These hot and humid areas will be home to nearly 1 billion new power-consuming individuals by 2025. As population grows and temperatures rise, demand for air conditioning will grow substantially.

Scientific studies show that health improves and productivity increases significantly with cooling of indoor spaces in hot weather.

“It is true that air conditioning made the economy happen for Singapore and is doing so for other emerging economies,” Pawel Wargocki, an expert on indoor-air quality for the International Center for Indoor Environment and Energy at the Technical University of Denmark, said.

In India, air conditioning has become a cultural priority, sending scientists scrambling to invent more-efficient equipment and better coolant gases to minimize energy use and planet-warming emissions. This demonstrates the beneficial relationship air conditioning can have with economic development.

The Cost to Cool
Research shows an alarming trend with respect to air-conditioning use. In 2007, for instance, only 11 percent of households in Brazil and 2 percent in India had air conditioning, compared with 87 percent in the United States. These data reflect considerable latent demand, with current energy consumption not yet reflecting what will happen when less-developed countries have more money and more people who can afford luxuries such as air conditioning.

Optimizing Cooling With Energy-Harvesting, Wireless Automation
Used in the control of HVAC and lighting, energy-harvesting, wireless technologies can be expected to save 20 to 50 percent on energy. For example, if a sensor detects that a room no longer is occupied, lights can be switched off and the HVAC systems controlled automatically, saving an average of 30 percent compared with a non-automated system. Alternatively, if enough natural sunlight is entering a room, lights can be programmed to dim or switch off automatically.

To appreciate the broad utility of wireless sensors, consider that up to 50 percent of the energy used to heat or cool a space is wasted through open windows with the HVAC running at full power. In a typical building, hotels in particular, a sensor can be used to detect an open window or balcony door. The HVAC unit then can be signaled to reduce heating or cooling or shut off until the window or door is closed. Individual room or area temperature monitoring and control (Figure 1) can reduce HVAC energy consumption by up to 30 percent alone.

A Standard for Green Buildings
Devices that are self-powered, meaning do not require wires or batteries, collect energy from their surroundings, including from motion, indoor light, and temperature differentials. This not only eliminates complicated and costly cabling, it ensures virtually maintenance-free operation.

The EnOcean protocol, which recently became an international standard, supports self-powered devices. It is the only standard designed to support very-low-power devices and energy-harvesting applications. EnOcean-based products use little power by delivering very short data packets and utilizing frequency bands with excellent signal propagation and minimal interference.

The EnOcean standard utilizes the less-crowded 868-MHz and 315-MHz frequency bands, making it suitable for use worldwide. This provides a safeguard against other wireless transmitters, while offering fast system response and eliminating data collisions. The range of EnOcean wireless sensors is about 900 ft in open spaces, such as warehouses, and up to 90 ft inside of buildings. Signals can be extended using repeaters.

Intelligent Interconnection
With EnOcean technology, an intelligent system can be realized by interconnecting automated thermostats, window contacts, humidity sensors, occupancy sensors, carbon-dioxide (CO2) sensors, and more. For example, a room controller receives information related to temperature, humidity, window position, or CO2 from sensors and controls the opening and closing of valve actuators for radiators. At the same time, the room controller sends information to an energy controller. Demand is calculated as a function of outdoor temperature and flow temperature to control energy generation (Figure 2).

The more complex a cooling installation, the greater the amount of information needed to control it. The utilization of single-room controllers with energy-harvesting, wireless technology and self-powered, wireless sensors can reduce significantly, if not optimize, the energy needs of a modern cooling plant.

High Energy Savings and Fast ROI
Occupancy-based HVAC and lighting control and monitoring systems can help reduce building energy consumption by up to 30 percent, often with a return on investment (ROI) of three years or less. In more variable cases, such as hotel and student dormitory rooms, which typically are occupied around 10 hr a day and vacant more than 100 days a year, energy reduction can be more than 50 percent, with a ROI of less than 18 months.

Companies supporting the EnOcean standard see increasing interest, particularly within the hospitality industry, in places such as Hawaii and Texas, where warm temperatures mean an almost year-round need for air conditioning. One, a U.S.-based manufacturer of wireless, batteryless energy-management technology specializing in Internet-protocol-based building automation, is leveraging the desire for energy efficiency in Hawaii. Its key-card-based system is saving a hotel in Oahu an average of 50 percent on HVAC-related costs and 45 percent on lighting costs. Another manufacturer recently began implementing a key-card-based system for a large hotel chain in Houston. The project includes five points of in-room control and an in-depth measurement and verification plan. Even though the cost of electricity in Texas is relatively low, the hotel expects to achieve a ROI in three years, possibly two.

The Role of Building Codes
The move toward energy-wise code modification began in California with the adoption of Title 24, a set of standards with energy-saving requirements for walls, roofs, windows, insulation, lighting, and HVAC systems. The introduction of Title 24 has saved Californians billions of dollars in electrical and natural-gas expenses. Although per-capita electricity use in the United States has increased by nearly 50 percent since the mid-1970s, California essentially has maintained its per-capita electricity use.

Other states have taken aggressive approaches to developing building codes. Hawaii, for instance, recently passed legislation requiring a method of adjusting thermostat setpoints and turning off permanently installed light fixtures and outlets powering portable light fixtures and entertainment devices when a “sleeping unit” in a new hotel or resort is unoccupied. To meet this requirement, hotel owners can utilize a key-card switch or an occupancy sensor.

Energy-Related Incentives
Let’s say you want to retrofit your building with energy-efficient HVAC or lighting, but funding is elusive. Fortunately, there are strategies to pay for energy-efficiency projects by significantly lowering your tax burden. Some companies help property and facility owners leverage tax incentives to implement energy systems.

One tax benefit that can be applied to energy-efficient construction and improvements is found in Section 179D of the Energy Policy Act of 2005. Also known as the Commercial Buildings Tax Deduction, 179D includes full and partial tax deductions for investments in commercial buildings intended to increase the efficiency of energy-consuming functions. The deduction available is up to 60 cents per square foot each for lighting, HVAC, and building envelope. These deductions are applicable to buildings built or retrofitted after Dec. 31, 2005. To qualify for the deduction, a taxpayer must receive third-party energy-efficiency certification.

The Future of Wireless Is Now
Wireless, batteryless devices provide improved flexibility, enhanced occupant comfort, and reduced energy consumption and are virtually maintenance-free.

Companies utilizing EnOcean technology are driving innovative solutions in HVAC and lighting control. One, for instance, combines wired, wireless, and Web technologies to provide flexible options for interfacing EnOcean and BACnet, as well as the ability to control lighting and HVAC with one controller. Another introduced the first solar-powered, energy-harvesting-based diffuser. Collectively, the EnOcean ecosystem continues to push the limits of wireless technology, proving that energy-management devices can operate efficiently and effectively, even without batteries.

Cory Vanderpool is business-development director for North America for EnOcean Alliance Inc., a consortium of 300 companies worldwide dedicated to advancing self-powered, wireless monitoring and control systems for sustainable buildings. Previously, she founded and served as executive director of GreenLink Alliance, a non-profit organization promoting energy conservation in buildings and tax incentives for building owners. She has a doctorate in environmental science and policy from George Mason University.

Did you find this article useful? Send comments and suggestions to Executive Editor Scott Arnold at [email protected].