Solar Domestic Hot Water Heater Performance: Effect of Changing Annual Load and Average Use Profile

Singh-Chhabra, Mohit

Graduate Thesis Or Dissertation

Solar Domestic Hot Water Heater Performance: Effect of Changing Annual Load and Average Use Profile Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/kh04dq07h

Abstract

The objective of this research is to understand, using computer simulation, the effects of changing domestic hot water load and usage patterns on the system performance of active and passive solar domestic hot water (SDHW) systems. Annual hot water load, mains water temperature, daily hot water load profile shape, and daily hot water load were the parameters varied to simulate variations in load and usage patterns that we expect would occur in a household. The effect of changing these parameters was quantified by studying change in annual solar fraction and annual system efficiency.Active and passive SDHW system construction was first defined. The system components of both active and passive system solar hot water systems simulated were determined by market research. The components were sized adequately using accepted component sizing guidelines. Daily hot water draw profiles developed at NREL (National Renewable Energy Laboratory) were used as the base draw profiles. The base profile has morning and evening hump and a daily hot water load of 60 gallons on weekdays and 75 gallons on weekends. The annual simulations were conducted in TRNSYS using a five minute time-step.Active (glycol) systems show greatest variation in simulated performance due to large changes in annual load. Passive (ICS) systems display high sensitivity to hot water profile shape. This difference between the two systems is due to the presence of a well-insulated solar storage tank in the glycol system.The glycol system shows less variation in performance due to variation in draw profile than the ICS system due to the presence of an appropriately sized and insulated solar storage tank in the glycol system. The solar storage tank helps glycol systems meet the demand for hot water during hours of low sunlight (early morning and late evening). ICS systems show higher sensitivity to profile shape as they cannot meet hot water load during morning and evening times; this morning and evening hot water load is met by the auxiliary heating tank.

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