Grantee Research Project Results

2016 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 , Milbes, Huda , Evans, Reginald , Riehn, Robin , Mohammed, Shahid , Morales, Sergio , Nguyen, Julie , Rolf, Julianne , Tan, Patrick , Tatyanich, Anna , Leyva, Juan , Coria, Vanessa , Hsieh, Jeffrye , Lara, Alex , Ngo, Ellyn
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, 2015 through August 14,2016
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 objective of this project is to reduce energy demands of households by providing an alternative and efficient way to dry clothes. The origin of this project began with the idea of creating a solar-powered thermal closet with the ability to space heat and dry clothes. A full-scale demonstration of this idea is currently in construction on a model home in Victory Gardens in Moreno Valley, CA. A separate prototype is also being built on our school campus tofacilitate the collection of data and testing of the unit. The system consists of two inline fans, a solar thermal collector, aluminum ducts, and a filter.

Figure 1: Air flow through the solar thermal closet dryer

With the use of an inline fan, ambient air is drawn and heated by a solar thermal collector (Figure 1 - Steps 1 & 2). Once the ambient air passes through the solar thermal collector, the heated air will then travel through an air filtration system before entering the dryer closet (Figure 1- Step 3). This will prevent dirt from contaminating the clothes inside the closet. Hot air will then enter the closet dryer from the bottom center, allowing the hot air to rise uniformly and dry clothes. An outlet fan located at the top of the closet will simultaneously draw the air out of the unit to improve the dryer’s efficiency. Finally, the humidified air will be exhausted back into the atmosphere (Figure 1- Step 4). Humidity and temperature sensors are installed throughout the entire system, which all lead to a single microcontroller to record data.  Uniquely, the closet can be turned on with the sole purpose of space heating a home. This is useful because, hot air that would be exhausted back into the atmosphere can now be redirected into a home for space heating. However, space heating is not included on the model in Victory Gardens due to time constraints for issuance of an amended building permit. We will test the potential of space heating using the data collected from the temperature sensors in our on-campus prototype.

Figure 2: IAS prototype on campus

The on-campus prototype is called the Integrated Appliance System (IAS). It is constructed at an agricultural facility known as the R’ Garden located on campus at the University of California, Riverside (Figure 2). The IAS takes into account an additional system that is intended to reduce the energy consumption of water heaters by preheating water with the use of solar thermal energy. The water-heating system consists of solar-heating coils, two electric water heaters, PEX piping, a solenoid valve, and an electric pump. The process begins with city water being drawn towards the first electric water heater, which is mainly used as a water storage tank (Figure 3 - Items 1 & 2). The electric pump then draws water from this tank, and pumps the water through the solar coils (Figure 3 - Item 3). After the water is heated by the solar-heating coils, it will then be split into two streams (Figure 3 - Item 4). One stream will lead back to the same storage tank (Figure 3 - Item 2) for recirculation and further heating while the other stream will lead to the second electric water heater (Figure 3- Item 5) when the water meets temperature specifications. Hot water can then be drawn from the second water heater for the consumer’s desired use. According to the article “Residential Water Heater Temperature: 49 or 60 Degrees Celsius?”,  the hot water temperature needs to be at least 50°C but the desired temperature is 60°C. This is because at 60°C, bacteria in the water is killed and at 50°C, there is no bacterial growth (Levesque et al. 2004).  In addition, the second water heater includes safety precautions that will activate the heater to prevent the water from going below 50°C. The solenoid valve (Figure 3 - Item S) will be used to stop the water from entering the second water heater after sunset when there is no more  sunlight to heat up the water. This will prevent contamination of the water in the water heater. The solenoid valve will reopen in the morning after both water heaters have a water temperature of 60°C.

Figure 3: Water flow in the IAS prototype

Progress Summary:

Construction of the model at the resident’s home in Victory Gardens began after receiving a building permit from the city. This model only includes the dryer closet system. Currently, the fans, ducting, insulation, and the solar collector have been installed, as shown in Figure 4. Unfortunately, the model is not fully constructed yet. The scheduling for an inspection from a city inspector to check the electrical wiring took longer than expected, adding delays to the team’s schedule. The hired contractor has resumed work and should be done with the construction within a month. Temperature and humidity sensors will be installed inside the closet to ensure the functionality of the appliance. The team will use the resident’s feedback to improve the system’s performance and to make adjustments to improve the interface of the controller, which is seen by the resident.

The IAS, consisting of a closet dryer and water heater system at the R’ Garden is also near construction completion. Both systems are inside a tool shed insulated with a 2.5-inch R-Tech sheathing, providing an R-value of 16.7, similar to that of a house. The interior of the closet dryer is shown in Figure 5. Five temperature/humidity sensors have been installed within the air system of the IAS. Two of which, have been installed inside the ducting to take measurements of the air before and after passing the solar thermal collector. The temperature difference between the two sensors will be evaluated to measure the performance and limitations of the solar thermal collector. Two air sensors have been installed inside the closet and the last sensor is inside the ducting for the exhaust. The temperature and humidity readings from those three sensors will indicate the performance of the closet dryer. The model at Victory Gardens and the IAS both do not contain the space heating system, where hot air is exhausted into a room. Instead, the team will evaluate the potential of space heating by using temperature readings from the two air sensors near the solar thermal collector in the IAS. Using the temperature, we will calculate the closet dryer’s space heating opportunities when applied to a room.

The IAS contains an additional five water temperature sensors within the PEX piping. The first sensor is used to measure the city water temperature. The second sensor measures the temperature of the recirculating water and the city water mixed together before entering the first water heater. The third sensor is installed after the electric pump, before water enters the solar coils. The fourth sensor is installed at the “T” tubing where the stream splits so that we may determine how hot the water temperature has reached after passing through the solar coils. The fifth sensor is installed after the solenoid valve to record the temperature of the water before it enters the second water heater. From this, we can calculate the efficiency of the solar coils and make readjustments for better performance.

A challenging factor about the IAS is that it is in a location where power is inaccessible. Therefore, a photovoltaic system must be installed to supply power to the fans, electric water heaters, electric pump, sensors, and microcontrollers. It has been estimated that the energy demand of the unit will be 4.7 kWh/day. According to our calculations, four lithium batteries, two inverters, and eight solar panels are required to accommodate the load. The calculation for the number of solar panels required considers the worst possible weather conditions that the prototype can encounter. Two important factors that vary monthly are peak sun-hours and temperature losses of the panels. Peak sun-hours dictate the amount of solar energy available. According to the article “High-Confidence Prediction of Energy Production from High-Efficiency Photovoltaic System”, high temperature losses yield better solar panel efficiency (Rose et al., 2010). September has low temperature losses and the lowest peak sun-hours, resulting in the highest amount of PV Array Watts needed for a given month. From our calculations, the photovoltaic system needs to supply 1.71 kW PV Arrays. This will be achieved with eight 265W solar panels. The team is now in the process of purchasing all of the necessary materials.

The programming of the microcontroller in the IAS is completed and capable of collecting data. The team tested three temperature and humidity sensors and the microcontrollers, which were powered by a temporary portable battery. Note that the portable battery was not able to power the fans. Therefore, our temperature and humidity levels were nearly constant throughout our data collection. Once the photovoltaic system is installed, the IAS will be fully functional and we will start collecting full temperature profiles thereafter. 

Figure 4.  Model in Moreno Valley

Figure 5. Interior of Closet Dryer at R’ Garden

Future Activities:

Our main goal is to make households less energy demanding by replacing the traditional electric tumbler dryers with our solar-thermal closet dryer found in the Victory Gardens and IAS models on campus. In addition, the IAS takes it even one step further by pre-heating water to reduce the energy usage of water heaters. Both prototype models are nearly ready, with the installation of the photovoltaic system at R’ Garden and the contractor making final adjustments at Moreno Valley. Once the models are fully functional, the team will be able to get feedback from the resident and record data for the system’s energy efficiency throughout the year. We envision the Integrated Appliance System to be assimilated with other appliances in the future to develop a green home powered by renewable energy sources.

References:

• Lévesque, Benoît, Michel Lavoie, and Jean Joly. "Residential Water Heater Temperature: 49 or 60 Degrees Celsius?" The Canadian Journal of Infectious Diseases.
• Rose, Doug, Oliver Koehler, Ben Bourne, Davis Kavulak, and Lauren Nelson. "High-Confidence Prediction of Energy Production From High-Efficiency Photovoltaic Systems ." (n.d.): n. page SunPower Corporation. 2010. Web. Pulsus Group Inc, 2004. Web. 11 Nov. 2016.

Journal Articles:

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

Supplemental Keywords:

Alternatives, residential, home improvement, green construction, innovative technology, pollution prevention, ambient air, renewable, public good, cost-benefit

Progress and Final Reports:

Original Abstract

2013 Progress Report

2014 Progress Report

2015 Progress Report

Final Report

P3 Phase I:

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