ONSETHOBO UX100-003 Temperature Logger for Building-Phase Change Material Temperature Monitoring

ZGF Architects used Onset temperature loggers to demonstrate the bioeffectiveness of phase change materials in regulating temperature fluctuations in a large University of Washington building.

overview

Whether in the form of dirt or blocks, stone, brick, or concrete, large-scale architecture has been ubiquitous throughout history. These building materials have been used in native homes in the American Southwest, in Egyptian pyramids, and in medieval castles and churches, keeping interior temperatures cool even on the hottest days.

Although it is known that the quality can help improve comfort, these materials are used primarily because of their easy availability and understanding by designers and builders. Construction has changed dramatically over time due to developments in building materials, construction techniques, and cultural changes in the workplace. The advent of steel, Portland cement, float glass, elevators and air conditioning led to tall glass-filled buildings that despite the environment and cut off visual connections to the outside world.

challenge

We progress to an increasingly knowledge-based economy, technology advances at work, and living densities increase. The combination of a paradigm shift in construction and the workplace has resulted in buildings using a significant amount of energy, together accounting for 41% of the United States' annual energy demand, and 75% of the United States' electricity demand. In addition, energy consumption is closely linked to greenhouse gas production, and reducing energy use directly reduces the release of greenhouse gases into the environment.

The focus on low-energy buildings has disappeared in recent history, with each update adding more tools to the toolbox. The OPEC crisis in the early 1970s spawned a short-lived sustainable movement that was once in favor of large-scale building, but abandoned as fossil fuels became available.

At this time, encapsulated phase change material solutions were introduced to the construction industry, but were unreliable due to the limited number of heating and cooling cycles as well as poor packaging with a tendency to leak. Over the past decade and a half, high-performance buildings have come back to the forefront due to concerns about national security, energy independence, and climate change.

Significant differences between the sustainable movement of the 1970s and the technologies used today to develop and veterinarily effective solutions. Create complex building energy models to account for the benefits or harms of low energy and employ typical associated strategies that significantly reduce risk to the solution. Essentially, we demonstrate that by using high-performance software solutions that have been used successfully for centuries are still relevant in the modern world.

So, how and why does mass help maintain comfort, and then if it's such a good job why do we even need phase change materials?

Energy always flows from high to low or hot to cold, and masses need coolers than spaces that absorb heat from occupants, equipment and sunlight. The high density of the mass, combined with the temperature difference, creates a reservoir of "coolness" that absorbs heat gained from the interior with minimal temperature increase to the surrounding space.

The absorbed heat can be released at night to help warm the space, or rejected to cool air at night, giving mass and restarting the cycle the next day. In climates with nighttime temperatures that drop well below daytime highs, the mass can be recharged simply by opening the windows during the cooler evening hours and closing the windows when temperatures start to rise.

Concrete is ubiquitous in modern architecture and benefits can provide a large number of structures common to ancient buildings. But even in green building design, exposed concrete interior surfaces are often the exception rather than the norm.

Often, carpet, drywall, acoustic ceilings, and other finishes are used to hide concrete building elements and effectively remove the heat benefits of using concrete as the building's primary structure. Since we have this resource hidden, can we use thermal storage in a way other than every exposed concrete surface?

solution

A company called Phase Change Energy Solutions has developed a biological phase change material (PCM) called BioPCM, which uses the concept of large-scale heat storage and release by harnessing energy with changing phases, UX100-003 temperature Recorder.

Materials change phases when transitioning from solid to liquid, vapor and liquid. More energy can be absorbed or released from the change in material alone in the heating or cooling phase, requiring less volume to achieve the same heat capacity. An inch of phase change material is as effective as 12 inches of concrete, and can be easily placed on interior walls and ceilings.

Phase change materials in architecture can be the equivalent of ice in an ice chest. The ice absorbs heat and melts, changing phases from solid to liquid, while keeping the contents of the chest at a constant temperature close to the freezing point of water. The ability to absorb heat by melting ice is far greater than the heat capacity of cold water, and expands the effectiveness of water as a cooling medium. Once the ice is completely melted, the water begins to warm as well as the contents of the chest. When refrigeration was first developed, ice was used to cool early New York skyscrapers and still newer green buildings such as the Bank of America building in Bryant Park.

BioPCM uses palm and soybean oils instead of water as the medium and has a melting point at 72°F, a temperature more suitable for people than cold beverages. In the ice chest, the temperature inside the chamber will be maintained at 72°F, the melting point of the oil, until the capacity for phase transition is exceeded, and all the oil is melted.

With phase change materials, the need for cooling can be reduced and the effectiveness of natural ventilation strategies can be extended. Unlike ice, due to its relatively high melting point, PCM can be charged the next day when exposed to cool nighttime air.

The large sheet produced by BioPCM with fat is encapsulated in a pocket similar to a sheet of raw ravioli. Sheets can be nailed to the wall for assembly or laid on the suspended ceiling for assembly.

The University of Washington's Molecular Engineering and Science Research Laboratory building is comprised of open offices for graduate work spaces, and faculty offices. Due to the different usage and spatial regulation strategies required, the laboratory components are separated by the glass walls of the offices. Standard laboratory conditions mean frequent ventilation changes to remove airborne contaminants.

It is the first building built by ZGF Architects with phase change materials applied to the walls and ceilings. PCM is not a cooling solution alone, but plays an important role in the overall natural ventilation strategy of the space.

The office area is ventilated by operable windows and natural ventilation stacks that draw heat away from people, equipment, and the sun. Even though Seattle's climate is mild, a cushion is needed to ensure comfort is maintained on warm days. Phase change materials were used to extend the capacity of natural ventilation strategies, and most of the concrete covering in the building was completed to suit the research facility.

The combination of reduced energy use and natural ventilation strategies resulted in a nearly 98% reduction in fan and office cooling energy compared to conventional cooling systems. The laboratory space is more energy intensive, resulting in an expected energy saving of 32% for the entire building compared to a conventional baseline.

Because BioPCM is an innovative product new to the market, a protocol was developed to monitor the temperature of the PCM over time to verify that the PCM performed as expected. Being able to understand the full benefits of PCM is limited due to the lack of real controls and experimental conditions. ZGF did not want to create a sacrificial space completely devoid of PCM control purposes and run the risk of affecting driving comfort.

Instead, the PCM is housed in a stud bay cavity in the office and a section in the ceiling. The aim is to use the data collected for an area without PCM as an area compared, and extrapolate to understand the larger impacts of the environment. The Vagabond U12 data logger from Start, a Massachusetts-based company, was placed on the wall next to the cavity and without the PCM, likewise on the ceiling.

result

UX100-003 temperature logger temperature every 15 minutes. Using the included HOBOware® professional graphing and analysis software, ZGF found initial data demonstrating that the BioPCM solution effectively moderated temperature fluctuations within the space.

In Washington, electricity is cheap relative to most of the United States. Where energy is more expensive, the use of phase change materials in combination with complementary strategies such as natural ventilation has the potential to provide life savings in operating costs, without compromising driving comfort.

For example, if nighttime temperatures are cooler, an expensive afternoon peak cooling can be offset by this free cooling technology capturing and storing the PCM in the previous night. If building usage prohibits opening windows during nighttime hours, the building ventilation system can blow cool air through the space, using off-peak electricity to charge PCM and offset cooling during peak hours.