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Open Access Publications from the University of California

Design and Performance Evaluation of Building Integrated Solar Technology for Greywater Recycling and Thermal Gain

  • Author(s): Kagey, Henry
  • Advisor(s): Hermanowicz, Slawomir W
  • et al.

Developing sustainable building technologies to confront the growing pressure of

essential resource scarcity is an important task for civil and environmental

engineers in the 21st century. This dissertation describes the design,

experimentation, and performance modeling of a multi-physics, building integrated,

solar-powered panel system for on-site greywater recycling and thermal gain for

interior climate conditioning. The hybrid CORE (Cylindrical Optical Reactive

Cylinders) panel type is novel in itself, using wave-guides to support titania

photocatalyst and distribute UV light for inactivation and mineralization of

contaminants, which has not been studied to date, particularly in a multi-scale


Several research directions are detailed, from determining the potential for

interception mechanics in the cylinder bank of waveguides, to the use of

mathematical optimization for performance analysis. In chapter II, Finite Element

Analysis on the micro-scale is used to develop a new correlation for particle capture

of cylinder banks in non-creeping laminar flow. In chapter III laboratory

experimentation on a CORE prototype is detailed in order to estimate reaction rates

under solar conditions and determine the efficacy of the optical waveguides for

stimulating mass transfer in a turbid medium. In chapter IV the NSGA-II algorithm

for multi-objective optimization is employed to assess the influence of multiple

parameters on the mass and heat transfer performance of the panel.

A novel correlation for particle interception in cylinder banks at moderate flow is

given, as well as a simplifying rule of thumb for engineering design purposes.

However, it is also shown that particle interception does not contribute

meaningfully to disinfection in the CORE panel. The reaction rate for the CORE

panel type is determined in the lab: the results show pseudo-zero order kinetics and

an over all slow reaction proportional to the Reynolds number on the order of 1e-4.

A correlation for reaction potential of individual cylinders developed via Chilton-

Colburn analogy from Žukauskas’ work on heat transfer in cylinder banks is shown

to compare well with the experimental results, matching exactly at Re 350. It is also

shown that the photocatalytic response is predominantly due to the effect of

waveguide UV transmission.

The performance evaluation of the CORE panel in the pilot scale simulation in

Berkeley, CA. using the NSGA-II genetic algorithm for the multi-objective studies on

efficiency and output showed tendency for maximizing cylinder diameter and thus

solid fraction, tilt generally pushed towards a 45 tilt from the vertical, and that

CORE could function with a relatively thin over all profile of about 5cm. The

maximum daily output of recycled greywater for a 1m2 panel over a year was 87L, a

relevant contribution to reuse of an individual’s daily grey water production. The

panel system functions best as building added system on the roof, but could function

as building integrated with specific modifications to the catalyst to increase

photosensitization. Further research is required in the direction of multi-parameter

optimization both to incorporate more parameters and design constraints (such as

the effect of flow rate and solid fraction on energy return) and as a design tool to

estimate context dependent design requirements.

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