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Welcome to the University of Louisville Renewable Energy Applications Laboratory (REAL).

Because fossil fuel resources are limited and contribute to global climate change, the world is beginning an unavoidable transition toward renewable energy. REAL is dedicated to the development of technology to make this transition possible, and to outreach to encourage widespread adoption of sustainable practices.
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The mission of this center is to conduct research, development and outreach on renewable energy systems. Current projects are focused on active and passive solar heating, ar heating, photovoltaics, solar daylighting and novel systems for storage of solar energy.

Research projects include computer simulations and experiments with a passive solar heating system that uses heat pipes to transfer heat into the building, while avoiding losses during nighttime and cloudy days. This system has proven to be roughly twice as effective as conventional passive solar systems in moderate climates such as Kentucky. Computer simulations are also underway to evaluate the feasibility of thermochemical storage of solar energy for electric power systems.

REAL has promoted awareness and knowledge of solar energy technologies by installing and monitoring the following demonstration systems in Kentucky: 1) Pool heating system, Frankfort YMCA, 2) Water heating and daylighting systems, Ramsey Middle School and Aiken Road Elementary School, 3) Photovoltaic street light comparison, Louisville Metro, 4) 25 residential solar water heating systems across Kentucky, 5) 50kW photovoltaic system, biohazard lab, Shelby Campus, 6) Photovoltaic and water heating system, Sackett Hall. Additional outreach activities include two solar energy installer training workshops and exhibits at the Kentucky State Fair.

Renewable Energy Applications Laboratory

REAL supports the Partnership for a Green City, a collaboration of the Louisville Metro government, University of Louisville and the Jefferson County Public Schools. Its goals are to improve the environment and public health, develop holistic environmental education programs, and to create a sustainable community, saving taxpayer dollars and conserving energy in the process.

REAL is proud to have contributed to the expansion of retailers and installers in Kentucky and to increased awareness of the potential for solar systems in the state. With relatively mild winters and approximately 2/3 the solar radiation of the desert southwest, many solar technologies are viable and appropriate here. With rising energy costs and growing concern about pollution and climate change, REAL seeks to develop and transfer green energy technologies to promote a sustainable future for planet Earth.
Renewable Energy Applications Laboratory
Solar Heat Pipe Wall
Computer simulations were performed to compare the thermal performance of several conventional passive solar heating systems, including direct gain, concrete wall indirect gain and water wall indirect gain, with a novel heat pipe augmented passive solar system (Fig. 1). Heat pipes provide one-way heat transfer into the building during sunny days,
Schematic of the solar heat pipe system.
with little heat loss out of thebuilding during nighttime and cloudy days. In the evaporator end of the heat pipe, which is attached a an absorber plate, a heat transfer fluid is boiled and the resulting vapor travels up to the condenser end (Fig. 2). There the fluid condenses, transferring its energy to the interior of the building.
Schematic of a heat pipe.
 Simulations were performed for Louisville, KY, Albuquerque, NM, Rock Springs, WY and Madison, WI. Results showed that the direct gain system performed well in cool and sunny Albuquerque, but produced a net loss in cold and cloudy Madison (Fig. 3). The indirect gain systems performed better than direct gain in all locations but Albuquerque. The water wall system provided greater gains than the concrete wall in all climates. The heat pipe system performed significantly better than all other systems in all climates. The heat pipe system was especially advantageous in cold and cloudy Madison. In Louisville, the solar fractions were 22.4%, 30.8%, 38.8% and 50.7% for direct gain, concrete wall indirect gain, water wall indirect gain and heat pipe systems, respectively. These performance values were better than those in Rock Springs, which is sunnier but colder, and considerably better than Madison, which is colder but only slightly cloudier. Though Louisville receives less solar radiation during the winter than Albuquerque and Rock Springs, it remains a favorable climate for solar heating because of its mild winter temperature
 Comparison of the thermal performance of several passive solar heating systems.
Tracking Solar Water Heating and Photovoltaic System
The University of Louisville Speed School of Engineering has been tapped to lead the Commonwealth of Kentucky's research endeavor into alternative and renewable energy. A prominent symbol of this endeavor is the tracking solar panel located on the roof of Sackett Hall. With a computer controlled dual-axis tracking system, its advanced features are intended for research, development and education, while supplying a portion of the building's electric and hot water loads. Two solar thermal collectors provide nearly 100% of the hot water in the summer, and less during the winter when colder temperatures reduce collector efficiency. Ten photovoltaic panels feed enough electricity into the grid to meet the needs of the building's computer laboratory. Current projects are focused on developing instrumentation and protocols for instructional laboratory experiments utilizing the system, and a real-time performance monitoring system. Check back in the coming months for updates.
Solar Thermal Collectors
Solar Water Heating in Schools
 Two elementary schools were recently constructed with identical architectural design and size. One incorporates solar energy systems, while the other does not, so that energy use differences between the two schools can be assessed. The solar water heating system on one school uses eight collectors by Heliodyne, model Gobi 410 for a total collector area of 320 square feet (Fig. 1) . A propylene glycol-based antifreeze mix transports the heat to a solar tanks located in the school’s basement adjacent to existing hot water tanks. The four 48-gallon solar storage tanks (Fig. 2) were manufactured by Heliodyne, Helio-Pax 32 (192 gallons total capacity). An external double-walled copper heat exchanger is located on top of each tank. A differential controller automatically starts both a collector and a storage side pump when the collector outlet temperature exceeds the tank temperature by 18o F. The tanks are interconnected and piped through a mixing valve to the school’s hot water tanks. All of the system components are certified and meet standards established by the Florida Solar Energy Center (FSEC). Evaluation of the performance of these two schools is in progress.
Solar Water Heating Rebate Program
To promote the use of solar energy in Kentucky, and to stimulate growth of solar industries in the state, a rebate program was established to support the installation of solar water heating systems on homes across the state. Guidelines were developed to ensure adequate solar access, freeze protection, system reliability and safety. Industry standard SRCC-rated collectors were required. Each system design was reviewed and installed systems were inspected. Twenty five $500 rebates were awarded throughout the year 2006. This program was a significant boost to awareness of solar energy in Kentucky and helped startup several new companies.
The Heliodon- Helping Architects Build Greener Homes
A heliodon is a device used to simulate the movement of the sun relative to the earth’s surface. Our heliodon, completed for display at the 2006 Kentucky State Fair, has helped students, professionals and the community understand how the sun moves through the sky and how proper design for a particular climate can improve the performance of passive solar heating systems.
The heliodon is relatively lightweight and portable. The heliodon can simulate the movement of the sun with adjustments for latitudes from near 0 (the equator) to 65 (mid Alaska) and for the full range of declination (summer solstice to winter solstice). The light source swings through an entire day with hour angles from sunrise to sunset. It uses a Fresnel lens to simulate the virtually parallel rays of the sun and supports up to an approximately 18”w x18”d x 12” tall model.
Solar Streetlights
Solar streetlights collect solar energy with photovoltaic cells and store the energy in batteries to be used during the night to light the street. During the summer of 2006, units from three different manufacturers were installed on Market Street between 6th and 7th in downtown Louisville. The site was chosen for its solar access to the south, which can be a challenge in city locations. Though the lights could be configured to use conventional electricity as backup. these systems were independent of the grid. Key to the evaluation was performance during December, when day lengths are the shortest, providing the least solar energy to the systems, and when temperatures are cold, which degrades the capacity of the batteries. One system provided light throughout every December night, while the other two had just a few nights (after several days of consecutive cloudy weather) when they ran out of power before sunrise. These tests showed that solar streetlights are a viable option for reducing energy costs and offsetting the environmental impacts of conventional energy production. Solar streetlights can be an economical solution, particularly in remote areas with difficult access to conventional electricity sources.
Solar Daylighting in Schools
A study was conducted to compare the performance of three designs for daylighting in classrooms. The three systems included:

1. 16” wide shelf—a prototype light shelf (Fig. 1) was built using box aluminum channels with a reflective mylar film (2 mm thick, 90% reflectance).

2. 24” wide shelf—a similar prototype constructed of box aluminum frame and reflective mylar film.

3. LightLouver System—A unit of angled, reflective blades similar to a fixed venetian blind. The patented, passive optical design redirects daylight deep into a room while eliminating all direct sunlight penetration onto work surfaces. The angled blades reportedly reflect up to 76% of direct sunlight into a room, and on overcast days they are said to throw around 54% of the available light inside.

The first two systems were fabricated locally, while the third system was purchased directly from the manufacturer. All three systems were installed in adjacent rooms, with a fourth room used as a control. A grid of light measurements were taken in the fall and early winter on cloudy and sunny days, during the morning, midday, and afternoon (Fig. 2). The light levels were analyzed to determine which system provided the most light gain. The conclusion of this study was that the 16” light shelf provided the most light gain through these windows.

Thermochemical Storage
Solar energy is abundant and virtually inexhaustible, however, its availability is not continuous and can be unreliable in some locations. Therefore, a practical method for storing solar energy is needed to meet demands for energy that occur when the sun is not shining. Stored solar energy may also be delivered at locations remote from the collection point. So far, photovoltaically generated electricity (from solar cell arrays) stored in banks of lead acid batteries is the most common method for solar energy storage. The aim of this project is evaluate an alternative means of storage based on a reversible chemical reaction. Computer simulations will be utilized to establish the thermodynamic performance of the cycle in a solar application, and its economic and practical advantages and disadvantages will be compared to battery storage and other storage mechanisms.
Methane reformation was chosen as a promising thermochemical storage method mainly due its proven record in other applications, the relative ease in handling the reactants (methane and water) and the end result (syngas) as well as the relatively low temperature required. The process may be described by the following chemical reaction, where the heat to drive the endothermic reaction is supplied by a parabolic dish concentrator (Fig. 1). The reaction products, syngas, can be stored indefinitely. When electricity is needed, heat from reverse reaction operates a Stirling engine-powered generator.

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