A novel multi-tank thermal energy storage (TES) was evaluated experimentally and numerically. The multi-tank storage is based on the interconnection of standard hot water storage tanks by a single charge flow loop. Each tank is charged through a thermosyphon loop and natural convection heat exchanger (NCHE). Both series- and parallel-connected configurations were investigated and results show that high degrees of stratification can occur. To predict the performance of the series- and parallel-connected multi-tank TES, a numerical model was developed and implemented in the TRNSYS simulation environment. Laboratory tests were also conducted to measure the unit’s performance under charge conditions representative of combinations of clear and overcast days. The effects of rising and falling charge loop temperatures and power levels on storage temperatures and heat transfer rates were studied and indicated that sequential stratification was achieved in the series-connected storage. Under certain conditions, reverse flow through the thermosyphon loops was identified, leading to destratification and carry-over of heat to the downstream storage tanks. Consequently, a new model was developed and showed to model reverse thermosyphon operation. A subsequent analysis showed that these effects could be minimized by careful system design. To quantify the relative benefits of the sequentially stratified TES, values of exergy stored versus time were determined and compared against fully stratified and fully mixed storages. Results show that the series configuration closely matches the exergy level attained by a perfectly stratified storage. Finally, annual simulations conducted for a typical multi-family installation showed that the multi-tank storage performed at a level comparable to a single, fully stratified, storage. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2009-06-24 00:13:01.142

[pt] Esta dissertação analisa aspectos da utilização da energia solar para aquecimento de água. Dois são os aspectos abordados: O primeiro é quanto à utilização de valores médios mensais ou diários de temperatura e insolação utilizados por diversos métodos de dimensionamento ou simulação de sistemas de aquecimento solar, e o segundo é a utilização de múltiplos tanques de armazenamento de água quente ao invés de um único reservatório de maior volume. Assim, este estudo tem como objetivo formular, simular e analisar diferentes cenários de configurações de sistemas de aquecimento solar de água, variando-se o número de reservatórios térmicos para um mesmo volume total do sistema. Tem-se por finalidade atender um mesmo padrão de consumo de água quente, condicionado a um mesmo perfil climático, visando otimizar a contribuição da energia solar ao sistema e consequentemente minimizar o consumo de energia auxiliar elétrica. / [en] This dissertation examines aspects of the use of solar energy for water heating. Two aspects are handled: The first is regarding the use of average monthly or daily values of temperature and insolation used by different scaling methods or simulation of solar water heating systems, and the second is the use of multiple hot water storage tanks instead of a single larger volume reservoir of water. Thus, this study aims to formulate, simulate and analyze different configurations of solar water heating systems scenarios, varying the number of thermal reservoirs for the same total volume of the system. It intends to satisfy the same standard of hot water consumption, under same climatic conditions to optimize the contribution of solar energy to the system and consequently minimize the consumption of electric auxiliary energy.