Dan S. Ward

Solar absorption cooling feasibility

Abstract The feasibility of small scale solar absorption cooling systems is dependent upon its technical and economically competitive position with respect to other cooling systems alternatives. Technical feasibility can be shown by comparisons of the thermodynamic efficiency of solar absorption cooling with conventional vapor-compression cooling equipment and by reference to numerous experimental evaluations. Economic feasibility is heavily dependent upon the financial parameters assumed (in particular the inflation rate of conventional fuel costs). In particular cases, i.e. particular assumptions of the financial parameters, economic feasibility of solar absorption cooling can be demonstrated.

Design and construction of a residential solar heating and cooling system

Abstract The first integrated system providing heating and cooling to a building by use of solar energy has been designed and installed in a residential-type building at Colorado State University. Solar heated liquid supplies heat to air circulating in the building and to a lithium bromide absorption air conditioner. Service hot water is also provided. Approximately two-thirds of the heating and cooling loads are expected to be met by solar energy, the balance by natural gas. The paper contains details of design and principles of operation. A breakdown of actual costs of the equipment and its installation is also provided.

Cooling subsystem design in CSU solar house III

Abstract The use of cool storage in conjunction with residential lithium bromide absorption chillers allows for improved operating conditions of the cooling subsystem. Significant performance degradation in the absorption cooling capacity is evident whenever the chiller cycles on and off during periods of low cooling demand. The capability of providing storage for the chiller out-put prevents short-term cycling of the absorption machine and significantly improves the seasonal average coefficient of performance of the cooling system. Cool storage can also be utilized to allow for a lower cooling capacity of the absorption unit (lower tonnage), without decreasing the ability of the subsystem to meet the cooling demands of the building. The size of cool storage can, in fact, be optimized by evaluating the ability of the cool storage component to minimize cycling of the absorption machine and in meeting the cooling demands on a smaller tonnage chiller.

Intergration of evacuated tubular solar collectors with lithium bromide absorption cooling systems

Abstract By surrounding the absorber-heat exchanger component of a solar collector with a glass-enclosed evacuated space and by providing the absorber with a selective surface, solar collectors can operate at efficiencies exceeding 50 per cent under conditions of ΔT H T = 75° C m 2 /kW ( ΔT = collector fluid inlet temperature minus ambient temperature, H T = incident solar radiation on a tilted surface). The high performance of these evacuated tubular collectors thus provides the required high temperature inputs (70–88°C) of lithium bromide absorption cooling units, while maintaining high collector efficiency. This paper deals with the performance and analysis of two types of evacuated tubular solar collectors intergrated with the two distinct solar heating and cooling systems installed on CSU Solar Houses I and III.

Operational modes of solar heating and cooling systems

Abstract This paper emphasizes factors associated with the subsystems that are required to extract heat from solar collectors, store this heat, and deliver it to the loads upon demand. While minimum use of auxiliary energy is the general objective, it must be sought with due regard to safety, convenience and cost. Subsystem alterations that improve energy efficiency typically come at added cost in terms of installation and maintenance. In some cases, the advantages of a specified component or arrangement of components are immediately evident. In other cases, such options are less decisive and will require longer periods of comparative operation to arrive at accurate assessments. The Colorado State University Solar House I allows for such comparative operation in several experimental modes. These selected modes of operation provide for different methods of solar heat transfer and employ different arrangements of system components and control functions. The principles underlying these modes as well as results of these studies are presented. In addition, the methods of operation found necessary for efficient and reliable performance are discussed. While this evaluation is an ongoing process, the initial “start up” and “break in” periods have been experienced and serve as a basis for several recommendations concerning subsystem components and component arrangements.

Preliminary performance of CSU Solar House I heating and cooling system

Abstract The NSF/CSU Solar House I solar heating and cooling system became operational on 1 July 1974. During the first months of operation the emphasis was placed on adjustment, “tuning”, and fault correction in the solar collection and the solar/fuel/cooling subsystems. Following this initial check out period, analysis and testing of the system utilizing a full year of data was begun. This paper discusses the preliminary performance of the heating and cooling system. During the period 1 August 1974–31 January 1975, approximately 40 per cent of the cooling load was provided by solar energy. Solar heating over the same period of time provided 86 per cent of the space heating load and 68 per cent of the domestic hot water heating load. These percentages represent a total solar contribution of 33,996 MJ delivered to load (8061 MJ to the cooling unit; 20,687 MJ to heating; 5248 MJ to hot water). Natural gas accounted for 22,442 MJ, total. In addition, preliminary analysis has provided several significant results associated with the operating characteristics of the solar system and the individual components.

Design of a solar heating and cooling system for CSU solar house II

Abstract This paper describes the design of a solar air heating and night/day exchange cooling system with emphasis on the operational modes. In this type of system the collector absorbs solar energy and converts it to heat for space heating and domestic water heating. Cooling is accomplished by using the cool night air available in dry climates) to cool a pebble-bed storage unit and subsequently using the cool pebbles to lower the air temperature in the building during the day. Circulation is from the solar system to the building in the same manner as most modern heating and air conditioning units but uses air as the medium for heat transfer. The air system is particularly suited for climatic regions where heating loads are high and cooling requirements are moderate. The system utilized in Solar House II operates in either the heating or cooling mode as selected through a seasonable change-over switch. Solar preheated hot water is furnished for domestic use in either mode.

INTEGRATION OF EVACUATED TUBULAR SOLAR COLLECTORS WITH LITHIUM BROMIDE ABSORPTION COOLING SYSTEMS

ABSTRACT By surrounding the absorber-heat exchanger component of a solar collector with a glass-enclosed evacuated space and by providing the absorber with a selective surface, solar collectors can operate at efficiencies exceeding 50% under conditions of δT/HT = 75°C·m2/Kw (δT = collector fluid outlet temperature minus ambient temperature, HT = incident solar radiation on a tilted surface). The high performance of these evacuated tubular collectors thus provides the required high temperature inputs (70–88°C) of lithium bromide absorption cooling units, while maintaining high collector efficiency. This paper deals with the performance and analysis of two types of evacuated tubular solar collectors integrated with the two distinct solar heating and cooling systems installed on CSU Solar Houses I and III.