Bachelor's thesis Sidney Schamel

 

Development and construction of solar thermal test bench

Diagram of the solar thermal test bench Copyright: EBC Diagram of the solar thermal test bench

With 87 % of the energy demand of a single-family home ascribed to heating and warm water, solar thermal energy offers a solution to increase renewable energy coverage and conserve resources through an easy integration in existing water heating systems. When designing such water heating systems, it is necessary to have a deep understanding of the yield forecast associated with solar thermal energy collectors.

During the course of this work, an existing solar thermal test bench was developed further, in order to allow for the recording of the absorbed energy by different collectors. The design of a controller, which regulates the volume flow through a bypass and henceforth the cooling power, enables the fulfilment of repeatable inlet temperatures. A comparison between experimentally determined efficiency rates and those calculated through coefficients supplied by the manufacturer reveal only a partial accordance. A slight overcast sky results in a deviation of 6,28 % while a clouding over to an increase of up to 35,26 % leads.

  Graphical comparison between experimentally determined efficiency and through performance coefficients estimated efficiency Copyright: EBC Graphical comparison between experimentally determined efficiency and through performance coefficients estimated efficiency

An Assessment of the Modelica flat plate collector model found in the HVAC library of the E.ON ERC leads to similar results. Through comparing experimentally obtained outlet temperatures with simulated studies of the same environmental conditions, an increase in deviation is observed as the fraction of diffuse light increases. When observing constant inlet temperatures, experimentally obtained and through simulation estimated outlet temperatures diverged less than 5 % under slightly overcast skies. A clouding over led to an increase in deviation to 104 %. Transient experiments with changing inlet temperatures increased these to 75 % under slightly overcast skies and 195 % in cloudy weather. A validation and verification of the model is therefore not possible.