Research Papers

Determination of Heat Transfer Characteristics of Solar Thermal Collectors as Heat Source for a Residential Heat Pump

[+] Author and Article Information
Maarten G. Sourbron, Nesrin Ozalp

THELES—Thermal and Electrical Systems
Research Laboratory,
Faculty of Engineering Technology,
KU Leuven,
Sint-Katelijne-Waver 2860, Belgium

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 December 2, 2015; final manuscript received April 8, 2016; published online May 25, 2016. Assoc. Editor: M. Keith Sharp.

J. Sol. Energy Eng 138(4), 041011 (May 25, 2016) (8 pages) Paper No: SOL-15-1409; doi: 10.1115/1.4033595 History: Received December 02, 2015; Revised April 08, 2016

With reducing energy demand and required installed mechanical system power of modern residences, alternate heat pump system configurations with a possible increased economic viability emerge. Against this background, this paper presents a numerically examined energy feasibility study of a solar driven heat pump system for a low energy residence in a moderate climate, where a covered flat plate solar collector served as the sole low temperature heat source. A parametric study on the ambient-to-solarfluid heat transfer coefficient was conducted to determine the required solar collector heat transfer characteristics in this system setup. Moreover, solar collector area and storage tank volume were varied to investigate their impact on the system performance. A new performance indicator “availability” was defined to assess the contribution of the solar collector as low temperature energy source of the heat pump. Results showed that the use of a solar collector as low temperature heat source was feasible if its heat transfer rate (UA-value) was 200 W/K or higher. Achieving this value with a realistic solar collector area (A-value) required an increase of the overall ambient-to-solarfluid heat transfer coefficient (U-value) with a factor 6–8 compared to the base case with heat exchange between covered solar collector and ambient.

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Fig. 1

(a) Possible connections of a solar thermal collector in a residential heat pump system for SH and hot water production, (b) investigated series system setup for SH

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Fig. 2

Equivalent thermal network for flat-plate solar collector with (left) and without (right) solar radiation (adapted from Ref.[10])

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Fig. 3

Solar heat pump system comprising solar thermal collectors, electrical back-up, heat pump, storage tank, and residence (with indication of measurement points)

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Fig. 4

COP of the modeled heat pump

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Fig. 5

Residence monthly heating energy use

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Fig. 6

Electrical energy use for heat pump compressor and back-up as function of global solar collector heat loss coefficient

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Fig. 7

Availability of solar heat as low temperature heat source to the heat pump

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Fig. 8

Heat pump system SPF1

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Fig. 9

Heat pump system SPF2

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Fig. 10

SPF2 as a function of collector area and storage volume

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Fig. 11

Availability (%) of the solar heat as low temperature heat source to the heat pump as a function of collector Usc value (for a collector area of 12.5, 25, and 37.5 m2 and a storage volume of 500 l)

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Fig. 12

(a) Availability (%) of the solar heat as low temperature heat source to the heat pump and (b) SPF2 as a function of the solar collector (UA)sc value (for a storage volume of 250, 500, and 750 l)



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