Grantee Research Project Results

2014 Progress Report: Heating Attic Air for Space Heating and Dryer Applications Using Solar Thermal

EPA Grant Number: SU835329
Title: Heating Attic Air for Space Heating and Dryer Applications Using Solar Thermal
Investigators: Tam, Kawai , Brisk, Philip , Alcaraz, Christian , Rolf, Julianne , Mak, Samantha , Schoeman, Ryan
Current Investigators: Tam, Kawai , Vu, Samantha , Leyva, Juan , Coria, Vanessa , Rodriguez, Giancarlo , Sanders, Brandon , Parker, Jonathan , Kim, Ji Hwan
Institution: University of California - Riverside
EPA Project Officer: Hahn, Intaek
Phase: II
Project Period: August 15, 2012 through August 14, 2014 (Extended to August 14, 2017)
Project Period Covered by this Report: August 15, 2013 through August 14,2014
Project Amount: $89,933
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2012) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Awards , P3 Challenge Area - Air Quality , P3 Challenge Area - Sustainable and Healthy Communities , Sustainable and Healthy Communities

Objective:

The solar thermal closet is an alternative unit for drying clothes and space heating and runs solely on solar energy (thermal and electric). Ambient air is drawn through piping in the attic to be preheated and is funneled through a solar thermal collector on the roof which consists of metal pipes that are exposed to the sun through a transparent tempered glass covering. Using a series of in-line duct fans, the hot air is channeled to the bottom of the solar thermal closet to rise vertically through the closet, where it dries the clothes and then escapes from the top of the closet to either the exterior or used for space heating when required for the home interior. The system will be automated with microcontrollers to provide clothes drying and space heating needs through a user-friendly LCD interface. Additionally, data is logged in the microcontroller to provide the user with information on the energy saved for a set period of time.  The objectives in Phase 2 include building and testing the dryer closet at Victory Gardens in Moreno Valley, CA, continued data collection of the system throughout the different seasons, optimization of the unit for both clothes drying and space heating through design features such as drying efficiency, safety, ergonomics and implementation of touch-screen user-friendly controllers. 

Progress Summary:

The current team took over this project from the previous team in June 2012. After familiarizing themselves with the Phase 1 design and prototype that was at Victory Gardens, the team began to determine ways to improve the prototype and design the next generation of the solar thermal closet dryer.  The first year of the project was spent researching and designing the new closet dryer to be ready to apply for the permit. During the second year, solicitations for bids were made to select a new contractor after the previous contractor declined the project due to personal reasons. The new contractor is CV Construction, a local construction company located in Riverside, California. Preliminary blueprints were submitted to the city of Moreno Valley and the city requested additional drawings. After several, successive attempts at providing the city with new and more detailed drawings, Moreno Valley has not yet permitted the building privileges at Victory Gardens. The team is moving forward by getting the drawings completed by an architect and stamped by a professional engineer to guarantee that the drawings are accepted. The Phase 1 prototype that was installed at Victory Gardens was removed as requested by the city of Moreno Valley so temperature and humidity data mining was suspended. Construction of the new closet dryer began at CV Construction so that the closet could be installed in the designated home in Victory Gardens as soon as the permit was received. This would allow for the testing of the completed dryer immediately. During the months spent waiting for the permit, the team worked on designing tests and optimizing the system. One of these improvements is the inclusion and placement of a filter. A filter will be added to the point of entry of the ambient air to the system to prevent dust and debris from getting into the collector and the ductwork.  Two bathroom fans and an inline fan were purchased and installed in the closet dryer at CV Construction for preliminary testing.

To test the fans in the closet, an anemometer was used to measure the air flow at the bottom of the closet, where the air enters and at the top of the closet, were the two bathroom fans pull the air out of the closet. A picture of the solar thermal closet connected to the solar collector on site is shown in Figure 1. The two chosen fans are rated at 50 cfm and include a light bulb that can be wired into the closet. This design was selected to mirror a normal closet with a light bulb feature. The air flow was found to be minimal, meaning new fans needed to be selected to optimize the closet. Car fans rated at 180 cfm were purchased and will be installed and tested to ensure that enough air is blowing through the closet to dry the clothes in a comparable amount of time. In addition, the temperature readings from the air blowing into the closet were found to be approximately 100°F. This is a lower temperature than the desired temperature of 150°F because the solar thermal collector is still not installed to face the sun at an optimal exposure angle in its current location. Additional testing will be done once the closet is installed to measure the new flow rate and the temperatures in the system once the closet is insulated. The sensors to measure the temperature and humidity sensors as well as the fans will be powered by renewable energy; more specifically solar panels that charge batteries so that the closet dryer can be used even when the sun is not shining on the collector. 

Figure 1. Heated air from the solar collector is pulled into the closet by the interior dryer closet fans while closet doors (white) on the right are closed.

The Solar Thermal Closet system consumes approximately 300W in order to run optimally. This is a major constraint since the system is completely off the grid and runs solely on solar energy using a solar panel system. All components were specified for this power consumption and function in a 12V system. To ensure that the system runs correctly and safely, relays and fuses are used to keep components separated and safe. The electricity is budgeted and the components are managed through the use of a Raspberry Pi Microcontroller.

The fan system used in the Solar Thermal Closet system is connected to a series of relay circuits that connect to Raspberry Pi PWM pins in order to control the fans on or off. This is to ensure that the hot air delivered to the closet is at a constant desired temperature. The Raspberry Pi determines the fan controls by receiving temperature and humidity inputs from thermocouples and a humidity sensor respectively. The fans are controlled to reach the optimal drying/heating temperatures set by the user by inputting information through a mini-LCD screen. The Raspberry Pi also has an additional input for a motion sensor. The motion sensor is used to avoid dangerous situations that may arise when the unit is installed in a residential home.

The safety parameters for this closet are targeted to limit the possibility of unwanted heat exposure towards children and small animals. The main safety hazard scenario involves young children or animals getting stuck in the closet while the dryer is being used. The safety features to limit this risk involve lock-free doors and the implementation of a motion sensor. The motion sensor will be placed an inch above the flooring and will have a linear scan radius to only monitor movement at ground level, prohibiting any triggering from shifting clothes during drying. The sensor device will be wired to the Raspberry Pi microcontroller to signal the fan to shut off if movement is sensed. The closet doors will not be locked. In the event that someone does happen to get inside the closet, they will be able to push the doors open and exit. The closet doors will still be well-sealed and insulated without a lock in order to achieve maximum temperatures within the closet.   Other safety features target health concerns such as allergens and dust. As stated before, there will be a filter placed before the air inlet in order to prevent allergens and dust from entering the closet and system.  The temperature inside the closet will be regulated to the optimal drying temperature of 150ᵒF using the Raspberry Pi. All of the electrical aspects of the closet will be reviewed by a contractor and engineer.

The closet will continue to be developed at the Victory Gardens community in Moreno Valley. The contractor for the project is Chuck Vahovich of CV Construction, Riverside. The second closet is designed to accommodate the new safety features and new microcontroller system. The closet frame and insulation have been completed and our next step is to implement the system at the community. We are currently in the process of getting city approval. As stated before, the blueprints are now being reviewed and drafted by an architect and will be submitted to the City of Moreno Valley for construction approval. A photo of the interior of the closet is provided in Figure 2 with clothes hung up for drying in the new dryer closet. The skeletal frame of the closet fits in more naturally to the home and provides a much large space to hang clothes as well as bed sheets. Adjustable shelving for delicate fabrics will be added in the future to increase the versatility of the solar thermal dryer closet to dry an assortment of items. The combination of all these features make the new closet more safe, efficient, user friendly, and aesthetically pleasing.

Figure 2. Interior of the closet with an assortment of clothes hung inside for drying.

Future Activities:

As the senior students of the team have graduated, a new team of sophomore and senior undergraduate students have been formed with knowledge from the chemical engineering, environmental engineering, mechanical engineering and computer engineering disciplines. This multidisciplinary team of sophomore and senior students have already become acclimated to the project goals and details. The junior member of the previous team is now a senior and her knowledge provides some continuity in the project. The multidisciplinary nature of the new team provides constructive and insightful perspectives when designing and working on the component parts of the solar thermal closet including updated drawings and designs, optimization of the microcontroller systems, appropriate sizing and rating of the fans in the closet and of the solar photovoltaic and battery system, and performing the experimental work. Select homes in the development of Victory Gardens in Moreno Valley have been identified and our team is ready.  Once the building permit is granted by the city of Moreno Valley, building and testing on site at Victory Gardens can commence.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this project

Supplemental Keywords:

Process control, PYTHON software, sustainability, conventional dryer, alternatives, residential, home improvement, green construction, innovative technology, pollution prevention, ambient air, renewable, public good

Progress and Final Reports:

Original Abstract

2013 Progress Report

2015 Progress Report

2016 Progress Report

Final Report

P3 Phase I:

Heating Attic Air Using Solar Thermal Energy for Space Heating and Drying Applications  | Final Report