Air-conditioning systems driven by solar energy have can save primary energy and reduce peak power consumption, which is particularly important for utility providers in the summer months. Additionally solar cooling is a promising application of solar thermal technology since the cooling load is well correlated to the overall solar availability. Liquid desiccant air-conditioning, which uses a salt solution to dehumidify air, can be used in a thermally driven air-conditioning system and offers many benefits for solar applications including the ability to store solar energy in the form of concentrated liquid desiccant. The current work focuses on the Queen’s University Solar Liquid Desiccant Cooling Demonstration Project. In previous work, a pre-commercial Liquid Desiccant Air Conditioner (LDAC) was installed and experimentally characterized using a gas-fired boiler to provide heat. As part of the current study a 95m2 solar array was added as a heat source. The Solar LDAC was tested for 20 days in the summer of 2012 to evaluate performance. The solar LDAC was found to provide between 9.2kW and 17.2kW of cooling power with an overall thermal Coefficient of Performance (COP) of 0.40 and electrical COP of 2.43. The collector efficiency was 53%, and 40% of the required thermal energy was provided by the solar array. A model was developed in TRNSYS to predict the performance of the solar LDAC and simulation results were compared to the experimental results with reasonable accuracy. The validated model was then used to simulate the annual performance of the solar LDAC in Toronto, Ontario; Vancouver, British Columbia; and Miami, Florida. The highest performance was achieved in Miami, where an overall thermal COP of 0.48 was predicted. It is proposed that additional improvements be made to the system by replacing inefficient pumps and fans, adding desiccant storage, and improving the control scheme. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-10-29 16:34:02.906

With the need to reduce CO2 emissions in the energy sector, ensure electric grid stability and reduce future cost uncertainties for process cooling, solar cooling can be an interesting solution. This report describes the comparison of solar cooling with either a photovoltaics system or a solar thermal system using a thermally driven chiller. The application investigated was industrial process cooling, for three load profiles and three locations in Europe. The method of comparing was by simulations in TRNSYS and calculation of the global levelized cost of cooling, taking into account the total cost of covering the whole cooling demand. The results for the global levelized cost of cooling showed that solar thermal cooling was not economically competitive compared to the reference system or the photovoltaic cooling system for any of the investigated boundary conditions. The general trend was that the global LCOC for the solar thermal cooling increased with the solar cooling fraction. The photovoltaic solar cooling system global LCOC was in parity with the reference system for low SCF of 20 % to 30 %, and even up to 60 % for some boundary conditions.

During the last 10 years solar cooling systems attracted more and more interest not only in the research area but also on a private and commercial level. Several demonstration plants have been installed in different European countries and first companies started to commercialise also small scale absorption cooling machines. However, not all of the installed systems operate efficiently and some are, from the primary energy point of view, even worse than conventional systems with a compression chiller. The main reason for this is a poor system design combined with suboptimal control. Often several non optimised components, each separately controlled, are put together to form a ‘cooling system’. To overcome these drawbacks several attempts are made within IEA task 38 (International Energy Agency Solar Heating and Cooling Programme) to improve the system design through optimised design guidelines which are supported by simulation based design tools. Furthermore, guidelines for an optimised control of different systems are developed. In parallel several companies like the SolarNext AG in Rimsting, Germany started the development of solar cooling kits with optimised components and optimised system controllers. To support this process the following contributions are made within the present work: - For the design and dimensioning of solar driven absorption cooling systems a detailed and structured simulation based analysis highlights the main influencing factors on the required solar system size to reach a defined solar fraction on the overall heating energy demand of the chiller. These results offer useful guidelines for an energy and cost efficient system design. - Detailed system simulations of an installed solar cooling system focus on the influence of the system configuration, control strategy and system component control on the overall primary energy efficiency. From the results found a detailed set of clear recommendations for highly energy efficient system configurations and control of solar driven absorption cooling systems is provided. - For optimised control of open desiccant evaporative cooling systems (DEC) an innovative model based system controller is developed and presented. This controller consists of an electricity optimised sequence controller which is assisted by a primary energy optimisation tool. The optimisation tool is based on simplified simulation models and is intended to be operated as an online tool which evaluates continuously the optimum operation mode of the DEC system to ensure high primary energy efficiency of the system. Tests of the controller in the simulation environment showed that compared to a system with energy optimised standard control the innovative model based system controller can further improve the primary energy efficiency by 19 %.

Anthropogenic activities are responsible for the impact of global climate change because of burning fossil fuels releasing harmful gases into the environment. As a result, the global temperature has risen about 1.18 °C since 1880, causing the global sea level to rise by 178 mm over the past century. This is a threat to countries that are closer to the ocean, especially the low-lying countries such as the Maldives. It is predicted if the sea level keeps rising, most of these islands could be below sea level by 2030. The Maldives has a tropical climate requiring cooling to achieve thermal comfort. Electricity is used to provide cooling which is generated by burning fossil fuels. Due to the need for more buildings and the effects of global warming, the demand for cooling has increased, ultimately increasing the emissions. Therefore, this paper investigated the methods to minimize the building cooling demand by creating a building model of a school in Feydhoo, Addu City, Maldives using DesignBuilder software. Also, to analyze the potential of using solar technology in providing cooling for the building, a clean energy source reducing emissions. The base model of the building showed that annual electricity consumption for cooling would be about 200.14 MWh. Based on the base model, multiple building models were created to understand the best option that can lower the cooling demand of the building. The results showed that having a super-insulated timber construction could be a better option by using improved double-glazed low-E windows and an improved cooling system with a COP of 3.2. This lowered the cooling energy demand to about 103.71 MWh. Based on these results, a solar thermal cooling system was simulated using Polysun software which shows that solar thermal collectors were not able to provide the required cooling to run the chiller system. Hence, another option was explored where DesignBuilder software was used to model a solar PV array system to provide cooling for the building. But by using a better air conditioning system (VRF system coupled with a DOAS) to provide fresh conditioned air into the building, improving the indoor air quality. The results showed that the new PV array system was able to provide the electricity required not for cooling but for other electrical requirements (total of 163.31 MWh). It also resulted in a surplus of 1 MWh of electricity exported to the utility grid, achieving a net-positive energy building.