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Pakistan-US Science and Technology Cooperation Program                                                            
Phase 4 (2009 Deadline)

A Hybrid Solar Water Heating System Using CO2 as Working Fluid 

Sumathy Krishnan and Samee Khan, North Dakota State University
Nasrullah Khan, COMSATS Institute of Information Technology (CIIT)
Pakistani Funding (HEC):  $76,566
US Funding (Department of State): $164,115
Project Dates: November 15, 2010 - November 14, 2012 (Extended through Dec 30, 2013)

Project Overview

This two-year project is intended to show how solar energy can be harnessed effectively and efficiently for heating purposes even in solar-adverse regions like the Gilgit-Baltistan area of northern Pakistan. Given the area’s climate, hot water is an essential commodity during the winter, but low winter temperatures and wind chill remain key limiting factors preventing effective and extensive use of solar energy there. However, recent developments in solar collector technology with CO2 (R-744) as a working fluid suggest potential for utilizing solar energy as a reliable heating source. Therefore, the research team involved in this joint project will work to integrate a solar collector using CO2 as its working fluid with a direct-expansion heat pump to ensure continuous and efficient operation even in harsh subfreezing conditions. The researchers hope that the project will result in a system that will work even in the absence of abundant sunshine and that will be cheap and practical, costing only about $300. With the current energy crisis facing Pakistan, this project will provide an environmentally-friendly alternative for meeting the heating and cooling needs of citizens in the underdeveloped region of Gilgit-Baltistan, lessening their current reliance on the unstable electricity supply or firewood.

Quarterly Update

Experimental testing of the solar CO2 hot water heater models in the U.S. and Pakistan were completed and data from the testing compared with modeling studies. Modeling results indicated the prototype could perform in all seasons including harsh winter weather conditions in North Dakota. However, experimental data showed this model was effective during the spring-summer-fall seasons and during harsh winter conditions required a compressor. To-date, this project resulted in 2 journal publications with 4 additional submitted and 5 conference presentations by the researchers. Educational impacts included development of two courses: a renewable energy technology course (NDSU) and a post-graduate level course in solar power generation (CIIT). Many graduate students worked on this project with three (1 female) at NDSU and two (1 female) at CIIT.

The solar water heating (Thermosyphon) unit containing 6 evacuated glass tubes was fabricated at the NSDU Mechanical Engineering workshop and methods in filling CO2 were studied. Preliminary testing confirmed that CO2 can be a potential candidate for solar water heaters but initial testing was hampered by harsh winter weather conditions in Fargo suggesting that seasonal variation might affect the overall performance requiring further seasonal testing.

Progress Reports

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