Solar thermal energy feasibility in a commercial building in Sacramento

In recent years, the demand for air conditioning systems due to the demand of higher comfort conditions has led to a significant increase for primary energy resources such as solar energy for cooling. Solar cooling (SC) is getting more and more readily available and cost effective. SC is environmentally friendly and decreases 〖CO〗_2 emissions thus reducing the greenhouse effect. Currently, one of the most frequently used solar cooling systems is the water absorption chillers. Most traditional air conditioning systems use compression technology for their chillers. The absorption chillers used for SC usually combine with flat plate or an evacuated tube collectors. These types of SC are relatively young and are still being developed. In this paper, a two story building that has an area of 2796 square meters and a max cooling load of about 211 kWh (60 RTh) is analyzed. Case Study 1 uses three of these buildings, Case Study 2 uses six buildings, and Case Study 3 uses 8 buildings. Given the different case studies, different chillers were chosen and the number of evacuated tube collectors and storage tanks are either increased or decreased given the number of buildings. The building’s design and cooling loads were developed with conjunction with the ASHRAE Example Building for Chapter 30, Nonresidential Cooling and Heating Load Calculations, of the 2005 ASHRAE Handbook-Fundamentals [1]. For the cooling and heating load calculations the radiant time series (RTS) method was used. From the cooling loads, the collector area and the volume of the storage tank were determined. In each of these three case studies, a cost analysis was made to compare the solar absorption system versus the tradition compression chiller. This analysis is made to see if this relatively new type of SC is even feasible in the Sacramento area. Only in Case Study 1, the solar absorption system ($796,663) is more economical than the vapor compression system ($901,624) after 20 years. The cost of Case Study 2 is $1,703,456 for the solar absorption system and $1,681,408 for the vapor compression system after 20 years. Finally, for Case Study 3, which included 8 buildings, the solar absorption system cost is $2,240,643 and the cost for vapor compression system is $2,194,774 after 20 years.