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Promising power

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Read about how ECEs are improving the efficiency of photovoltaic cells through better control systems in The New Solar.

ECE 4304: Design in Power Engineering

The energy lab is being built by students taking ECE 4304. The course is a capstone design elective for EE students and a technical elective for CPE students. It is typically offered both fall and spring semesters.

Catalog description: Study principles in electric power engineering and apply them in design problems including: machine control and design, IT and Internet applications in power, expert systems and AI applications, power system protection and digital relaying, communication, and data transmission, solar and wind energy, computer-aided design and GUI, data over power lines.

Building an energy lab with spare parts and creativity

Ozen, Brennan, Saunders, Gebre (Photograph by Christina O'Connor)

Yigit Can Ozen, Michael Brennan, Mark Saunders, and Messeret F. Gebre

ECE students [and professors] are creating their own outdoor laboratory to study alternative energy issues. With funding from the engineering fee, students in ECE 4304 Design in Power Engineering are pouring concrete to support their equipment, building their systems, and repurposing old technology. A visit to the laboratory reveals a couple of highly reflective parabolas — former satellite dishes that have been converted into solar collectors.

“Students want to do hands-on work with alternative energy,” says Virgilio Centeno, an associate professor of ECE and the course supervisor. “We’re now giving them the chance.”

For several years, student design teams had tried working with solar panels installed at various locations on campus, but had to stop due to safety and access concerns, according to Centeno. This past year, the ECE department was able to allocate some dedicated outdoor space just off campus, with some shared interior space for equipment and other needs.

The first major effort involved renovating and installing an abandoned 3-meter satellite dish for use as a solar collector. A local resident donated the dish, but the students dug it up and installed it themselves. Although the white dish could collect enough energy to boil water, the students installed a reflective film (later upgraded to polished steel) to increase its solar gain.

PV array (Photograph by Christina O'Connor)

Power design students have converted an abandoned satellite dish into a thermal collector that tracks the sun each day. The controller is powered by a solar panel nearby.

Professor Tim Pratt, an old hand with using the dishes for communications research, guided the team as it created a system to allow the dish/solar collector to track the sun. The mechanism that moves the dish is powered by solar panels that were donated by the College of Architecture and Urban Studies, so the entire operation uses only alternative energy sources. With the last minutes of sun each day, the dish moves itself back to reset for the next day.

The students have been very enthusiastic about the repurposed dishes, according to Centeno. “There are a lot of abandoned satellite dishes, if we can find a cheap way to reuse them, that’s wonderful.”

The course enrolls about 20 students each fall and about 30 each spring. The semester-long projects are limited, but many teams choose to build on efforts from prior semesters, or to establish new systems for future classes.

For spring 2010, three senior ECE students are assembling two solar systems. One is a 500W (in midday sun in June) photovoltaic system that charges a battery. Mentored by Pratt, the students are measuring how much energy can be collected by a typical, commercially available photovoltaic system and comparing the cost to electricity bought from American Electric Power (AEP). According to Pratt, “it’s usually cheaper to buy from AEP.”

Steam coming from a thermal collector (Photograph by Christina O'Connor)

The thermal collector can easily boil water.

The second system is a hot water generator that uses heating tubes and a heat exchanger. Such systems can be used to preheat water for household use or to heat swimming pools. The hot water can be used to store solar energy for use at night.

Another group of students is studying some of the problems with the solar panels. Dirt and pollen building up on the panels significantly affect their ability to capture energy. One possible way to take care of this is to run water constantly over the solar panels, but the running water also takes energy and needs to be supplied by the panels. This group will soon know if it’s worth it.

A third group is working on a solar tower, which operates like a greenhouse to heat the inside air, which then rises through a central chimney to power turbines. Only three of these towers are in use in the world today: one in Spain, one in Australia, and one in Texas.

A fourth project, mentored by Jaime De La Ree, associate professor and assistant department head of ECE, explores the question of whether solar energy needs to be converted into electricity at all. “There is a lot of waste in converting solar energy into electricity and if the end use is something other than electricity, that conversion is wasted,” says De La Ree. The students are exploring using the reflective dishes directly for heating and air conditioning, which represent major uses of electricity around the world.

Jaime De La Ree explains how the dish works (Photograph by Christina O'Connor)

Jaime De La Ree, associate professor and assistant department head of ECE

“Converting solar energy into heat is much more efficient than converting it to electricity, which is then converted again to heat,” he says. Cooling is a bit trickier. The students are investigating the use of an ammonia-cycle chiller used in off-grid refrigeration systems. When water and ammonia are mixed, heat is absorbed. If the reaction takes place inside a vessel, the outside gets colder and air moving across it gets cooled. For continuous cooling, however, the cycle needs to be repeated.

“We’re trying to build a closed system, so we need to boil the mixture to separate it into water and ammonia again.” The students are calculating the energy needed for the flame, and seeking ways to increase the temperature without boiling, because of pressure concerns in a closed system. They also are measuring the amount of energy lost as heat on the dish itself. If there is a significant amount, that heat can also be captured and used.

About these projects, De La Ree says, “If it works, great! If not, all our students will still know more about control systems, alternative energy, and thermal power.”