Modeling and Testing of a Liquid Desiccant Dehumidification System Regenerated with Solar Thermal Energy

Hatt, Michael Andrew

Graduate Thesis Or Dissertation

Modeling and Testing of a Liquid Desiccant Dehumidification System Regenerated with Solar Thermal Energy Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/qf85nb56b

Abstract

A computer simulation model for a liquid desiccant and PV/T system was examined in this thesis. The model was calibrated using data from an experimental system installed in Orlando, Florida, developed by the the National Renewable Energy Laboratory, in conjunction with several other companies. The experimental system uses a warm-air cross-flow absorber/regenerator and a 11.2kW PV/T array that provides hot air to regenerate the desiccant.The data gathered from the experimental system was used to validate the accuracy of the PV/T array temperatures, along with the effectiveness of the desiccant and regenerator in the simulation model. An expanded simulation model uses a previously validated model for a cross-flow absorber and cooling tower, along with the newly modeled regenerator and PV/T system. The combined system was modeled for various absorber, regenerator, tank, and PV/T sizes to determine appropriate component sizing to meet a given ventilation load. The simulations were used for seven different locations, including: Orlando, Houston, Atlanta, Washington DC, Phoenix, Guam, and Honolulu. Performance characteristics were examined, along with the potential energy savings of using a PV/T-desiccant system for dehumidification instead of standard air-conditioning.Results of the simulations show that the largest amount of absorption achieved is at high flow rates at lower PV/T outlet temperature set-points. However, the highest PV percentage (ratio of PV panels to thermal collector modules) provides the most energy savings, because less fan and pump energy are required and more electrical energy is being generated. Temperature set-points above 40℃ were found to be acceptable for regeneration, which also allows for a higher air flow rate than would be permitted at higher regeneration temperatures. Meeting the full latent load at the ASHRAE minimum outdoor air ventilation rate was shown to not be possible for most multi-story office buildings, because the PV/T array sizes required are typically too large for the building roof . However, operating a PV/T-desiccant system to meet a 50% load allow for much smaller array sizes, even at higher PV percentages. When meeting the half load, climates in the very hot-humid zone 1A and hot-humid zone 2A achieved savings of 22-49% when compared to using standard air-conditioning to meet the latent load. More energy is obviously saved when the PV/T-desiccant provides more dehumidification than the standard air-conditioner.

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