BFRL: Heat Transfer and Alternative Energy Systems Group

Heat Transfer and Alternative Energy Systems Group

Building Sensor Evaluation Lab

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Technologies

Wireless Sensor Node.

Wireless sensor networks: Wireless technology is gaining a foothold as a means of communicating data through buildings. One exciting application of wireless technology is the implementation of wireless sensor networks. The need to run wires through buildings to transmit sensor signals from the sensing location to a data collection point or to other sensors or controls is costly and cumbersome. Wireless radios can eliminate this need. BFRL has recently implemented a wireless sensor network in a residence to monitor the performance of a heat pump, the efficiency of a water heater, and the hygrothermal condition of an exterior wall. This sensor network was based on mesh technology, in which sensors not only communicate with a central collection point but also have the capability of communicating with each other. This added ability adds robustness to the sensor network since messages can be routed through different nodes to reach their intended destination. The sensor network also self-configures, allowing for easy expansion to monitor different quantities in a building. Methods are being developed to speed the adoption of wireless sensor technology into the building community by ensuring that tools exist to allow for plug-and-play operation of wireless sensors in buildings.

Key efforts are currently underway to allow for easier deployment of wireless sensor technology in buildings. Wireless technology has eased the burden of physically deploying sensors in a building for either short-term monitoring or for integration into a building control system, but the ability to deal with such a vast amount of data may prove to be intractable. One effort aims to allow for easy identification of sensors for building applications by standardizing terminology for identifying such sensors. Another research area aims to develop a testbed to measure the performance of wireless sensor networks in buildings to aid building professionals in making decisions about sensor deployment and to give sensor vendors a target to which they can design their systems.

The other focus of wireless sensor networks is on homeland security applications. BFRL is currently working with other researchers around NIST to develop methods for integrating sensor networks at the building level with information from sensor networks on a regional level such as those associated with weather forecasting or alert systems for Chemical, Biological, or Nuclear hazards. By encouraging interoperability among the different sensor networks, better information will be made available to emergency personnel and regional decision-makers to prepare for and deal with catastrophic events.

Ultra-Wideband Radar: Ultra-Wideband (UWB) Radar is being investigated as a technique for moisture detection in walls. UWB radar differs from conventional radar in that broadband pulses of very low power are emitted instead of a continuous signal with constant frequency. The radar has been aimed at various building materials, and the reflections have been analyzed to determine any dependence of the reflections on moisture content. The broadband signal of the UWB radar promises to provide more information on the structure than can be obtained in a narrow band signal. An additional benefit of UWB is the fact that a number of manufacturers are planning on mass-producing the necessary hardware for use in wireless communications equipment. If these plans come to fruition, the hardware needed to sense moisture in buildings would be quite affordable. Preliminary results have shown the potential for using UWB to distinguish the moisture contents of different layers within a wall. Additionally, the radar unit has been meshed with special software that creates a 3-dimensional image of the moisture level within a wall. This research has resulted in a patent issued to NIST for a moisture detection system in walls. Further work could be undertaken to identify the best parameters for operation, the potential resolution, the performance under field conditions, and the limitations of the technique.

Optical fiber RH sensor within sheathing placed on wood sample.

Fiber optic RH sensors:
In conjunction with a private company, NIST investigated the viability of fiber-optic relative humidity sensors for determining the moisture content and surface relative humidity in wall cavities. The main advantage of optical fiber-based technology is the small size of the sensors. The sensor has a diameter of approximately 250 micrometers, enabling it to fit into places where ordinary sensors might leave an excessively large footprint. The fiber is quite durable, and multiplexing techniques promise the ability to string a web of sensors within the envelope with relative ease.

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Radar unit aimed at a sample wall section. 3-D image of moisture level within a sample wall. A moist patch was placed on the outside of the OSB, and this image identifies the location of that wet spot in the wall.

NIST is an agency of the U.S. Department of Commerce

Last updated: 1/16/2008