Using Wasted Thermal Energy to Improve Home Appliances Performance and Reduce Electric Power Consumption

Currently, Puerto Rico faces an energetic and economic crisis. The cost of kWh ranges from 26 cents to 29 cents; with the average household consumption of energy being about 908 kWh monthly. This means the average household in the island is currently paying about $263 a month on their electricity bill. While the Electric Power Authority of Puerto Rico sets the monthly cost per kilowatts; the amount consumed can be up to the client. Home appliances such as the refrigerator, heater and air conditioning unit are essential household equipment that tend to consume the most energy. Some household appliances, struggle to work within high ambient temperatures like those experienced in Puerto Rico. Refrigerators, for example, canâ??t work properly if the ambient air around the condenser is not at least ten degrees lower than the condenser so that the energy can be given off as radiant heat. If the maximum temperature is exceeded the appliance will struggle to keep the temperature on the inside down and would run constantly or at least for longer periods of time. This could cause overheating, breakdowns and higher energy consumption.
After analyzing this problem, students of the Electrical Engineering Department of the Polytechnic University of Puerto Rico develop a Thermal Energy System that could help to reduce the electrical energy consumption. The objective of this researchâ??s work itâ??s to improve the thermal system built by the electrical engineering students; in order to accomplish this, it was proposed to use the wasted thermal energy of the system to improve home appliances performance and reduce electric power consumption. The first phase of this research consisted on finding an optimum working fluid for the system and the second phase was to design a heat exchanger network that use the wasted thermal energy and install the same in the electrical engineering thermal prototype.
The electrical engineer students were originally using water as the systemâ??s fluid in order to cool down the inside prototypeâ??s temperature; as result they only drop down the same one °F at some hours of the day, but it wasnâ??t constant all day and at some peak hours it was even higher than the control prototype. The chemical engineer students proposed a coolant as an optimum fluid. Two coolants were tested: ethylene glycol and propylene glycol at three different concentrations each. Experimentally was proven that ethylene glycol 50% reduced the temperatures inside the prototype two to three times more than only water and the effect was even through the whole day, so electrical appliances inside a house that has this system would consume less electrical energy. In the second phase, two heat exchangers were added so the heat removed from the prototype was transferred to a heater and air conditioning, in order to them use less electrical energy and work with wasted thermal energy as well. Scaling this work to run an average house could save people money on their monthly electric bill while, helping the environment with an ecofriendly house system.