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Research Papers

Increasing Efficiency in the Extraction of Solar Heat Stored Underground With Perturb-and-Observe Control

[+] Author and Article Information
Carlos R. de Nardin

Center of Excellence in Energy and
Power Systems,
Federal University of Santa Maria,
Avenida Roraima, 1000,
CT 7—Sala 490,
Santa Maria 97.105.900, Brazil
e-mail: denardin@gmail.com

Felipe T. Fernandes

Center of Excellence in Energy and
Power Systems,
Federal University of Santa Maria,
Avenida Roraima, 1000,
CT 7—Sala 490,
Santa Maria 97.105.900, Brazil
e-mail: felipetfernandes83@gmail.com

Adriano J. Longo

Center of Excellence in Energy and
Power Systems,
Federal University of Santa Maria,
Avenida Roraima, 1000,
CT 7—Sala 490,
Santa Maria 97.105.900, Brazil
e-mail: longoaj@hotmail.com

Luciano P. Lima

Federal Institute Sul-Rio-Grandense,
Avenida das Indústrias, 1865,
Venâncio Aires, Rio Grande do Sul 95.800-000,
Brazil
e-mail: lucianolima@ifsul.edu.br

Felix A. Farret

Center of Excellence in Energy and
Power Systems,
Federal University of Santa Maria,
Avenida Roraima, 1000,
CT 7—Sala 490,
Santa Maria 97.105.900, Brazil
e-mail: fafarret@gmail.com

Dário R. Cruz

Federal Institute Sul-Rio-Grandense,
Avenida das Indústrias, 1865,
Venâncio Aires, Rio Grande do Sul 95.800-000,
Brazil
e-mail: dariocruz@Ifsul.edu.br

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received June 22, 2016; final manuscript received November 16, 2016; published online December 22, 2016. Assoc. Editor: Jorge E. Gonzalez.

J. Sol. Energy Eng 139(2), 021014 (Dec 22, 2016) (7 pages) Paper No: SOL-16-1291; doi: 10.1115/1.4035329 History: Received June 22, 2016; Revised November 16, 2016

This paper describes a perturb-and-observe (P&O) control aiming to increase the heat exchange between solar heat stored underground and the ambient of a single conditioned room without any heat pump. This P&O control increases or decreases the water flow rate through an underground hosepipe heat exchanger. With this purpose, two power converters were used to activate, respectively, a low power water pump and a fan coil so as to keep the room within the limits of a reference temperature range (between 18 °C and 24 °C). Outside these limits, the P&O control searches for the best heat exchange between the ambient room and the underground soil and, when inside these limits, the water pump and fan coil are turned off. Two identical experimental rooms, referred in this study as “reference” and “test” rooms, had their temperatures measured every 1-min during winter and summer. For comparison purposes, the reference room was left at its natural conditions without any air conditioning. The experimental results show a remarkable improvement in the heat exchange and a considerable reduction in power demand when using the P&O control. As a result, it was obtained an energy saving of approximately 45% in one summer day and 22% in one winter day. It is important to point out that this paper refers, strictly, to the description of a P&O control for heat exchange systems involving solar heat stored underground in a single room.

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References

Figures

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Fig. 1

Block diagram of the heat transfer system

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Fig. 2

Block diagram of the P&O control for the air conditioning prototype

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Fig. 3

Flowchart control of the water pump

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Fig. 4

Temperature in the reference room compared with those of the test room with heat exchange system turned off and the external ambient

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Fig. 5

Action of the P&O control with heat exchange system on (June 5th, 2014)

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Fig. 6

Temperature in the reference room compared with those of the test room without P&O control and the external ambient (Jan. 19th, 2013—summer cooling mode)

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Fig. 7

Temperature in the reference room compared with those of the test room with P&O control on and the external ambient (Oct. 29th, 2014—summer cooling mode)

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Fig. 8

Power of the water pump and fan in the test room (Oct. 29th, 2014—summer cooling mode)

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Fig. 9

Temperature in the reference room compared with those of the test room without P&O control and the external ambient (July 10th, 2013—winter heating mode)

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Fig. 10

Temperature in the reference room compared with those of the test room with P&O control on and the external ambient (June 9th, 2014—winter heating mode)

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Fig. 11

Power of the water pump and fan in the test room (June 9th, 2014—winter heating mode)

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