Solar Absorption Cooling and Heating System in the Intelligent Workplace

Author(s):  
Ming Qu ◽  
David H. Archer ◽  
Hongxi Yin ◽  
Sophie Masson

A solar thermal driven absorption cooling and heating system has been installed in Carnegie Mellon University’s Robert L. Preger intelligent Workplace, the IW. The purpose of this solar installation is to investigate the technical and economic aspects of using high temperature solar thermal receivers driving a two stage absorption chiller to cool and heat a building space. The solar system consists primarily of 52 m2 of single-axis tracking parabolic trough solar collectors (PTSC), and a 16 kW double effect absorption chiller driven by either a fluid heated in solar receivers or by natural gas fuel. The receivers convert solar radiation to thermal energy in a heated fluid; the chiller then uses this energy in summer to generate chilled water. In winter, the thermal energy is directly used for heating. A performance analysis was carried out to estimate the conversion efficiency of the PTSC based on mass and energy balances and heat transfer computations programmed in Engineering Equation Solver (EES). The performance of the overall solar cooling and heating for the IW has been programmed in TRNSYS modeling system. This solar energy system has been estimated to provide 38–50% of the cooling and 9–30% of heating energy depending upon orientation, insulation and storage capacity for 245 m2 of space in the IW. Experimental data are now being collected and will be used for validating the solar collector model. The solar system model will be used in interpreting the data yet to be obtained on the system performance. The primary purpose of this research program is the development of systems which reduce the energy requirements for the operation of buildings by a factor of two or greater, and the provision of techniques and tools for the design and evaluation of such systems.

Solar Energy ◽  
1984 ◽  
Vol 32 (2) ◽  
pp. 181-187 ◽  
Author(s):  
R.K. Suri ◽  
K. Al-Madani ◽  
S. Ayyash

Author(s):  
Ming Qu ◽  
David H. Archer ◽  
Hongxi Yin

The center for building performance and diagnostic (CBPD) at Carnegie Mellon University has successfully designed, installed and tested a solar cooling and heating system to assess the feasibility of solar cooling for small scale commercial buildings or residential buildings with aspects of technology and energy efficiency. This solar cooling and heating system is primarily comprised of parabolic trough solar collectors, PTSC’s and a 16 kW dual energy source double effect (2E) absorption chiller. The 2E absorption chiller driven by PTSCs was tested to produce chilled water or hot water throughout a number of clear days in summer and winter. The analyses of the experimental data defined the system performance: the efficiency of the solar collector, the capacity and COP of the chiller, and the heat transfer coefficient of the heat recovery exchanger, by using a statistical approach, based on the energy balance equation. In the solar cooling tests during July 2007 in Pittsburgh, PA, the average efficiency of PTSCs was 35% when they were operated at about 155°C for driving the 2E absorption chiller and the chiller was able to provide 8 to 14 kW cooling with COP in the range 1.0 to 1.2; the overall system efficiency is in the range 0.35 to 0.41. In the near future, this solar absorption cooling and heating test system and its operation will be integrated with the cooling, heating and ventilation units for long term utilization.


Author(s):  
Yin Hang ◽  
Ming Qu ◽  
Fu Zhao

Solar absorption cooling and heating (SACH) systems currently still stay at development and demonstration stage due to the nature of the complex system. It is critical for practitioners and engineers to have a correct and complete performance analyses and evaluation for SACH systems with respects of energy, economics, and environment. Optimization is necessarily involved to find the optimal system design by considering these three aspects. However, many assumptions made in the optimization are sensitive to the energy, economic, and environmental variations, and thus the optimization results will be affected. Therefore, the sensitivity and uncertainty analysis is important and necessary to make optimization robust. This paper uses a case study to explore the influence of the uncertainties on the SACH system optimization results. The case is a SACH system for a medium size office building in Atlanta. The one parameter at a time (OAT) sensitivity analysis method was applied firstly to determine the most sensitive inputs. Monte Carlo statistical method was utilized to generate the data sets for uncertainty analysis. The optimization problem under uncertainty was then formulated and solved. Due to the uncertainty associated with system inputs, the optimization solutions were found with certain types of the distributions. In addition, the scenario analysis on electricity price does not show large sensitivity to the objectives.


Author(s):  
Stephen M. Smith

A 35,000 ft2 [3,251 m2] Creative Arts instruction building is being constructed on the campus of Haywood Community College in Clyde, NC (∼25 miles [40 km] west of Asheville). The building’s HVAC system consists of a solar absorption chiller, two parallel back-up electric chillers, and radiant floor heating with condensing boiler back-up. Hot water is to be heated by 117 solar thermal panels with thermal energy storage in a 12,000 gallon [45,000 liters] insulated tank and service to both the absorption chiller and the radiant under-floor heating system. Peak cooling loads and unfavorable solar conditions are to be handled by parallel electric chillers, operated in sequence to achieve maximum performance. Emergency radiant under-floor heating hot water back-up is to be handled by gas-fired condensing boilers in the event of unavailable solar heated hot water. This paper will examine the extensive modeling process required of the system as performed in EnergyPlus, how preliminary modeling results influenced the control and design strategy, the annual behavior of the system and the importance of controllability.


Author(s):  
Yin Hang ◽  
Ming Qu

Solar absorption cooling has been an intriguing research subject since 1970. However, it is not widely applied because the first cost of the system is high, the commercial hot water absorption chiller is not mature, the site demonstration and evaluation are not adequate and the price of conventional fossil energy sources is relatively low. This paper investigates the commercialization potentials of solar absorption cooling and solar heating system by comparing the life cycle cost between it and the conventional electrical chiller cooling and gas-fired boiler heating system. A computational model has been programmed in the Engineering Equation Solver (EES) to analyze the economical performances of the two systems applied to a dedicated building. The model considers the cost of capital, installation, operation and maintenance, the discount rate, the fuel prices, and the inflation rates. The result of the model indicated that given the present fuel cost, the solar absorption cooling and heating system is not as economic as the conventional system especially when its size is small. However, according to the sensitivity analysis carried, the solar absorption cooling and heating system could compete with the conventional cooling and heating system when the electricity price and fuel inflation increase.


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