Grantee Research Project Results

Final Report: A Novel Dual Purpose Solar Collector Design

EPA Grant Number: SU839340
Title: A Novel Dual Purpose Solar Collector Design
Investigators: Yu, Yao , Eichholz, Ben , Xiang, Junlong , Wood, Mark , Sammartino, Rhys , Miao, Rui , Tangpong, Siwakorn , Hu, Xiaoou , Zhang, Yan
Institution: North Dakota State University Main Campus
EPA Project Officer: Page, Angela
Phase: I
Project Period: February 1, 2018 through January 31, 2019
Project Amount: $14,999
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2017) RFA Text |  Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Air Quality , Sustainable and Healthy Communities

Objective:

A Flat Plate Solar Collector (FPSC) is a commonly used device to harvest solar energy. An FPSC is typically covered on top with a single-pane glass, known as a glazed FPSC. A conventional glazed FPSC is generally used only for heat collection. The purpose of this project is to develop an innovative design of a dual purpose glazed solar collector that is able to utilize sustainable energy, i.e., solar heat and night sky cooling, to accomplish heat and cold collection. In this proposed collector, a double-pane “window” will be used on the top of an FPSC to replace the conventional single-pane glass cover, which allows water or other liquid flowing in the space between the two glazing panes to lose its heat through both long-wave radiation and convection. Specifically, the objectives of this project include: 1) developing a working prototype collector; 2) performing the feasibility analysis of this type of solar collector; 3) investigating the applicability of this solar collector by using computer simulations and lab experiments; 4) identifying the potential difficulties and problems when developing and using this type of collector; and 5) evaluating and optimizing the efficiency and/or performance of the collector through computer simulations and lab experiments.

Summary/Accomplishments (Outputs/Outcomes):

The collector has been successfully developed in a lab with the use of the clear twin wall polycarbonate sheet as the double-pane cover, which is lighter than a single-pane glass with a higher thermal resistance and similar solar transmissivity, and thus it may effectively block the escape of the heat from the top cover but at the same time allow a large amount of solar radiation going through. In addition, the reduced weight of the cover panel contributes to the reduction of shipping costs of the collector, and the high emissivity of the polycarbonate sheet allows the heat carried by the fluid in the double-pane cover to be effectively radiated out to the surrounding environment, especially to the cold sky during summer nights. The successful establishment of the prototype collector allows the research team to carry out the necessary experiments and measurements in order to quantify the thermal performance of this collector, especially for its cold collection feature. The measurement results show that the cold collection capacity of the collector is about 150 Btu/hr/ft 2 and 200 Btu/hr/ft 2 when the inlet water flow rates are 2.7 GMP/collector and 4.2 GMP/collector, respectively, given that the surrounding temperatures (ambient air and average surrounding surfaces) are near 60 o F and the typical design water temperature is 95 o F from a refrigeration cycle (e.g., a water-source chiller) as the inlet water temperature for the collector. Additionally, the successful development of the calibrated simulation model in COMSOL allows the in-depth study on the impacts of various environmental parameters, such as the temperatures of the inlet water, the ambient air, and the surrounding surfaces (or the sky), on the cold collection capacity of the collector. The simulation results indicate that the average cold collection capacity of a collector with the size of 8’ by 4’ and assumed to be used in the city of Fargo, North Dakota, during summer, is around 4,500 Btu/hr (i.e., 140 Btu/hr/ft 2 ) with the range between 2,500 and 6,000 Btu/hr. A problem in terms of leaking has been identified at the connections between the cover panel and the manifold, and the research teams will work together to solve it and look for a way to avoid it from a design perspective in the future study. In addition, the fabrication of the manifold is another challenge, especially when the channels of the double- pane cover are too close to each other, so that it is difficult to fabricate a copper or plastic manifold with such small distance between the small tubes/channels.

As an educational tool, the prototype collector of this research was used as an example in one of Dr. Yu’s undergraduate courses at NDSU, CM&E 421 Electrical and Mechanical Construction. The intent is to teach students sustainability concepts and principles and then to encourage their engagement in sustainability practices.

Conclusions:

In this project, a dual purpose solar thermal collector was successfully developed and established for system performance measurement as well as feasibility analysis. This research project aims to use the new type of collector to replace cooling towers or dry coolers and thus has the potential for reducing or even avoiding the negative effects of cooling towers or dry coolers, such as the unnecessary waste of condenser water, the urban heat-island effect, the threat of Legionnaires' disease, etc. Therefore, this proposed project encourages the use of renewable energy, improves human health, protects the environment by effectively and efficiently using water and energy, and reduces the associated greenhouse gas emissions. The wide utilization of this type of collector may increase its economic competitiveness in the market because of its dual functions of both heating and cooling in a single unit compared to the individual use of conventional FPSC(s) and cooling tower(s) for the same purposes.

Both of the measurement and simulation results indicate that this type of collector is superior to the conventional unglazed FPSCs for cold collection. This innovative design concept of this type of collector is relatively easy to understand and could be widely accepted by most engineers and designers, which contributes to its wide adoption and deployment. It also has the potential for the integration with different HVAC (Heating, Ventilating, and Air Conditioning) units to maximize system efficiency and performance and to achieve more energy savings. For example, this type of collector may be integrated with heat pump units and underground loops/storage tanks to carry out daily or seasonal heat and/or cold storage. Hence, it deserves long-term research and development in order to ensure or improve its feasibility and reliability in integration with a variety of building HVAC systems.

References:

[1] ASHRAE Research. 2013. ASHRAE Handbook-Fundamentals. I-P Edition. ASHRAE, 1791 Tullie Circle, N.E., Atlanta, GA, 30329.
[2] Anderson, T.N., Duke, M., Carson, J.K. 2011. Performance of a building integrated collector for solar heating and radiant cooling. Solar 2011, the 49th AuSES Annual Conference, November 30th – December 2nd, 2011.
[3] Anderson, T.N., Duke, M., Carson, J.K. 2013. Performance of an unglazed solar collector for radiant cooling. Australian Solar Cooling 2013 Conference, Sydney. Page 19
[4] Man, Y., Yang, H., Spitler, J.D., Fang, Z. 2011. Feasibility study on novel hybrid ground coupled heat pump system with nocturnal cooling radiator for cooling load dominated buildings. Applied Energy, 88, 4160-4171.
[5] CM&E 421. https://www.ndsu.edu/pubweb/rr/curricula/2013/engr/cme.pdf (accessed: Jan. 29, 2019).
[6] LEXAN Thermoclear Multi-wall Polycarbonate Sheet. http://www.sdplastics.com/thermoclear/LTCTechnicalManual.pdf (accessed: Jan. 29, 2019).
[7] Comsol Multiphysics. https://www.comsol.com/ (accessed: Jan. 29, 2019).
[8] Comsol Multiphysics - Heat Transfer Module. https://extras.csc.fi/math/comsol/3.5/doc/ht/htmodlib.pdf (accessed: Jan. 29, 2019).

Journal Articles on this Report : 2 Displayed | Download in RIS Format

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Other project views:	All 2 publications	2 publications in selected types	All 2 journal articles

Publications

Type	Citation	Project	Document Sources
Journal Article	Miao R, Hu X, Zhang Y, Wood M, Olson G. Experimental study of a newly developed dual-purpose solar thermal collector for heat and cold collection. ENERGY AND BUILDINGS 2021;252(111370).	SU839340 (Final)	Full-text: ScienceDirect - Full Text HTML Exit
Journal Article	Miao R, Hu X, Uu Y, Zhang Y, Wood M, Olson G, Yang H. Evaluation of cooling performance of a novel dual-purpose solar thermal collector through numerical simulations. APPLIED THERMAL ENGINEERING 2022;204(117966)	SU839340 (Final)	Full-text: ScienceDirect - Full Text HTML Exit

Supplemental Keywords:

solar collector, solar thermal heating, radiation cooling, night sky cooling, renewable energy, energy savings.