Grantee Research Project Results

2015 Progress Report: Biowall’s Impact on Indoor Air Quality and Energy

EPA Grant Number: SU835730
Title: Biowall’s Impact on Indoor Air Quality and Energy
Investigators: Hutzel, William J , Dana, Michael N , Mietusch, Reinhardt , Rajkhowa, Bhargav , Maupin, Chelsea , Cord, Caleb , Newcomer, Heather , Babb, Terrance , Caron, Mikaela , Pennock, Callum , Leuner, Hannes , Boiquaye, Edith , Fister, Alex
Current Investigators: Hutzel, William J
Institution: Purdue University
EPA Project Officer: Hahn, Intaek
Phase: II
Project Period: August 15, 2014 through August 14, 2016
Project Period Covered by this Report: August 15, 2014 through August 14,2015
Project Amount: $90,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2014) Recipients Lists
Research Category: P3 Challenge Area - Sustainable and Healthy Communities , Sustainable and Healthy Communities

Objective:

With the rise of energy efficient homes, indoor air quality (IAQ) poses a difficult challenge between balancing energy conservation and the need to maintain a healthy indoor air environment. Maximizing house insulation and making a residence airtight are basic approaches to reduce energy consumption for heating and cooling. However, this can create stale air inside ae house that needs to be supplemented with fresh air at regular intervals. Standards such as ASHRAE 62.2 (Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings) came into place to define the minimum ventilation requirements based on the building’s square footage and the number of its occupants. Natural ventilation, mechanical ventilation, and energy recovery ventilation (ERV) are common technologies used to introduce fresh air while conserving energy. But, in spite of adapting ventilation standards and using a proper ventilation system to improve IAQ and conserve energy, it has not completely eliminated indoor air pollution (ASHRAE 2013). 

Progress Summary:

Indoor Air Quality (IAQ) Challenges

IAQ is still a serious issue in buildings, as the environmental protection agency (EPA) classified the problem as one of the top health concerns in the U.S. (EPA 2009). According to William Fisk from Lawrence National Laboratory, asthma, sick building syndrome (SBS), allergies, and other respiratory illnesses were highly associated with poor indoor environments.  Health risks are not the only part of indoor problems, productivity was also found to be negatively affected in polluted indoor air environments, which costs the U.S. up to $150 billion a year (Fisk 2000). The main contributors to the pollution in indoor air are the volatile organic compounds (VOCs) that are emitted from many household products and construction materials. For instance, adhesives and paint can emit Toluene and Benzene, while new clothing and carpets off-gas formaldehyde, and these are just some examples of many other VOCs found in buildings (Spengler & Chen 2000). Therefore, proper ventilation systems or indoor air-cleaning devices have become essentials in residential buildings, especially the airtight ones. 

Studies have shown that plants can eliminate VOCs both in their rhizosphere and phyllo sphere through phytoremediation. This is why a Biowall (BW), where plants grown hydroponically are used to maximize the plants’ phytoremediation ability, is being designed to address these challenges. The medium in which the plants are grown allows for adequate moisture content to keep the plants healthy and is also porous enough to allow air to flow through it without creating a significant increase in fan energy consumption.

Figure 1 illustrates the problem of poor IAQ. It shows how an airtight home which minimizes the interaction of cold outdoor air (OA) with warm indoor air (IA). But due to VOC emissions from various sources the IA between becomes stale and polluted. The BW, which would be installed in the return duct of the home’s HVAC system would clean the air and then send it back through the home’s Air Handler (AHU).

Figure 1 VOC concentrations in air tight homes can contribute to poor indoor air quality Summary of Outputs/Outcomes

This EPA P3 project has built a new biowall test apparatus, conducted experiments on its air cleaning potential, and is currently deploying a “next generation” biowall into a research home: 

Improved Biowall Test Apparatus

In the fall of 2014 a new BW test apparatus was built and used to carry out a series of tests to help refine the design of the BW. It allowed students to look specifically at the interaction between the plants/growth media and the ventilation air for a house using a single vertical plenum with plants placed in a horizontal box with growth media. The test apparatus, which was placed in an environmental chamber (EC), was used to test various growth media compositions and select one which would keep the pressure drop across the BW at a minimum and also maintain sufficient moisture in the filter bed to ensure satisfactory plant health. 

After a detailed study of various growth media that could be used, the students settled on a mixture that was a combination of Coco Coir (CC), growstone and activated carbon (G/AC). This was because CC, which has the high water holding capacity needed to keep the plants healthy, and the G/AC mix, whose high air porosity would allow sufficient airflow across the BW while minimizing the pressure drop across it, would complement each other well and thus provide the conditions necessary for satisfactory plant health.    

The image on the left in Figure 2 is of the BW’s test apparatus and the one on the right is a graph of the pressure drop across the BW for every centimeter of filter bed thickness. All tests were carried out at a Volumetric Water Content (VWC) of 20% as most plants require a (VWC) of 532% (Wang 2010) to survive and 20% was seen as a satisfactory mean. The face velocity across the BW was varied and the pressure drop then recorded. The horizontal axis indicates the percentage of coco coir in the mixture with the rest of the mixture containing growstone. The vertical axis is for the Pressure drop per centimeter of thickness of the various growth media tested.

Figure 2 Test apparatus position in the environmental chamber and pressure drop per cm. of thickness.

After noticing the effects of the pressure drop on fan energy consumption and the water content in the BW on the health of the plants, the students came to the conclusion that a growth media mixture that contained 50 % of CC, 32 % of growstone and 18 % of AC by volume would serve the BW’s needs the best.

Having selected this growth media composition the students carried out a series of tests in the spring of 2015 to test the endurance of the BW’s plants. In order to carry out these tests, the fan attached to the BW’s test apparatus was run at various duty cycles. This meant that the test apparatus’s fan would mimic the way in which the fan in a residential air handler would operate. The temperature and relative humidity both across the BW and in the environmental chamber were monitored and recorded. The pressure drop across the BW was also recorded at regular intervals. 

The health of the plants during each duty cycle was also closely monitored. Reports summarizing plant health during each duty cycle were written and would be used for future reference and analysis. The species of plants tested during these endurance tests were golden pothos, philodendron and spider plant. Simultaneously, the BW’s potential as a food growing source was also explored by propagating spearmint, rosemary and thyme in the filter bed during endurance testing. 

The data obtained from these tests will be used to:

• Optimize the irrigation strategy for the BW. 
• Develop a suitable control sequence to operate the BW. 
• Select plants which would maximize the BW’s air cleaning and food growing capacity.

With most residences in the U.S. being maintained at a particular temperature set point during summer and winter, the environmental chamber will be maintained at a summer and winter time set point and the endurance of the BW will again be tested for the various duty cycles. This would allow the students to observe the health of the plants in conditions which mimic those found in an actual home and thus further refine the design of the BW.  

Air Cleaning Evaluation

For their senior design project, a gas dispersal system was developed by the students from Electrical Engineering Technology to introduce VOCs into the environmental chamber in a controlled and safe manner. The rate at which the VOC is removed will be determined by continual monitoring of the VOC level in the chamber. Once the VOC removal rate of the BW has been established the residual VOCs in the environmental chamber will be exchanged with fresh air, and this will be circulated through the BW and monitored for the challenge gas to determine how much, if any, desorption of the challenge gas occurs.

Figure 3 illustrates the VOC dispersal system’s operation. The dispersal rate and overall concentration of the VOC will be controlled by the programmable syringe pump and introduced into the chamber via an atomizing nozzle fixed to the syringe. Conditions in the environmental chamber will be monitored and all acquired sensor data will be displayed and recorded using a data logging software developed specifically for this purpose.

Figure 3 VOC dispersal system operational flowchart.

Biowall in Research Home

Efforts have also been made to integrate the BW into the Retrofit Net-zero Energy Water and Waste (ReNEWW) House. The ReNEWW house is an on-going project sponsored by Whirlpool which is looking at fully-efficient residential homes and is located near the Purdue University West Lafayette campus. After optimizing the design of the BW in the lab it will be added to the ReNEWW home. This allows the team to evaluate BW air cleaning and endurance characteristics in a net zero home. The data collected will then be used to make further improvements to the BW’s design.

Figure 4 presents the Whirlpool ReNEWW house and the location of the BW in it. The image to the left is of the external view of the ReNEWW house and the image to the right shows the location of the BW in the living room.  The biowall will be installed by January of 2016.

Figure 4 Whirlpool RENEWW house with BW location

Community Outreach

Various summer camps had been held in the Applied Energy Laboratory, the current location of the BW. These camps informed high-school age adolescents of the benefits of alternate and renewable energies, as well as the impact they can have on their surroundings. 

STEM fields are growing increasingly popular, and several of these camps were aimed at populations that are considered frequent minorities within STEM fields. The goal was to promote engineering and technology, while showing specific advancements in the field to generate student interest. During their time in the laboratory, the students were given opportunities for hands-on activities that helped to instill knowledge of the concepts of efficiency, sustainability, and net-zero energy. 

Activities included measurements that were taken in the environmental chamber of the Applied Energy Laboratory, which houses the BW’s test apparatus. Students measured air velocity through the apparatus while a ducted fan was running, while simultaneously recording values for differential static pressure for a comparison. This sought to show the simple relationship between static pressure drop and air flow. 

Students were also introduced to concepts involving green sustainability, and reducing the carbon footprint left by society on a daily basis. Presentations were given to camp students detailing the impact the BW has on a home, as well as other alternatives for energy sources and approaches for reducing energy consumption, including solar power.

Figure 5 shows images of students in a summer camp targeted toward females in the engineering/technology discipline. This camp was hosted on July 21, 2015, for two separate sessions. As shown in the image on the right, students were given opportunities to investigate a mock test apparatus, measuring air velocity as it passed through a growth media combination similar to what will be used in the future BW. 

Figure 5 Students hosted by the Applied Energy Lab for one of Purdue Polytechnic Institute’s summer camp programs

Future Activities:

The design of the BW has undergone significant changes in the past year with the plants being grown in a hydroponic medium instead of an aeroponic one. The newer optimized design of the BW will first be tested in a laboratory setting where both its air cleaning and humidification characteristics will be evaluated in a controlled environment. The VOCs that will be introduced into the environmental chamber will be done at a controlled rate and their levels would resemble VOC levels commonly found in a home. This would provide greater clarity on the Clean Air Deliver Rate (CADR) that the BW can provide for an energy efficient residence. With humidity levels in a home being fairly low in the winter, the endurance of the BW in dry conditions and its ability to act as a humidifier will also be evaluated in the next phase of testing. The data collected from the controlled tests in the environmental chamber will be used to improve and alter the design of the BW so as to ensure a smooth and trouble free operation in the Whirlpool RENEWW home. The student camps were very successful in promoting interest in STEM and sustainability and will continue next summer as well.

References:

• ASHRAE. (2013). ASHRAE Standard 62.2: Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential. Atlanta: American Society of Heating Refrigeration and Air Conditioning Engineers.
• U.S. Environmental Protection Agency (EPA). (2009, August).Residential Air Cleaners, second edition. A Summary of Available Information, EPA 402-F1-09-002.
• Fisk, W. J. (2000). Health and Productivity Gains from Better Indoor Environments and their Relationship with Building Energy Efficiency. Annual Reviews of Energy and the Environment, 25, 537-66.
• Spengler, J. D., & Chen, Q. (2000). Indoor air quality factors in designing a healthy building. Annual Review of Energy and the Environment, 25(1), 567-600.
• Z. Wang, Characterization and performance evaluation of a full-scale activated carbon-based dynamic air filtration system for improving indoor air quality, Syracuse 2010.

Journal Articles on this Report : 2 Displayed | Download in RIS Format

Publications Views

Other project views:	All 6 publications	2 publications in selected types	All 2 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	Newkirk DW, Hutzel WJ, Dana M, Qu M. Energy modeling of a botanical air filter. ASHRAE Transactions 2015;128(1):8.	SU835730 (2015) SU835730 (Final)	Abstract: Purdue Abstract HTML Exit
Journal Article	Newkirk D, Evans JS, Alraddadi OS, Kelemen CG, Mietusch R, Xue Y, Rajkhowa B. Plant-assisted air-conditioning systems for a better tomorrow. IEEE Potentials 2015;34(1):11-17.	SU835730 (2015) SU835730 (Final)	Abstract: IEEE Abstract HTML Exit

Supplemental Keywords:

Phytoremediation, clean air delivery rate (CADR), VOC

Progress and Final Reports:

Original Abstract

Final Report

P3 Phase I:

Biowall’s Impact on Indoor Air Quality and Energy  | Final Report