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- All Subjects: engineering
- Genre: Masters Thesis
Description
In this thesis the performance of a Hybrid AC System (HACS) is modeled and optimized. The HACS utilizes solar photovoltaic (PV) panels to help reduce the demand from the utility during peak hours. The system also includes an ice Thermal Energy Storage (TES) tank to accumulate cooling energy during off-peak hours. The AC runs continuously on grid power during off-peak hours to generate cooling for the house and to store thermal energy in the TES. During peak hours, the AC runs on the power supplied from the PV, and cools the house along with the energy stored in the TES. A higher initial cost is expected due to the additional components of the HACS (PV and TES), but a lower operational cost due to higher energy efficiency, energy storage and renewable energy utilization. A house cooled by the HACS will require a smaller size AC unit (about 48% less in the rated capacity), compared to a conventional AC system. To compare the cost effectiveness of the HACS with a regular AC system, time-of-use (TOU) utility rates are considered, as well as the cost of the system components and the annual maintenance. The model shows that the HACS pays back its initial cost of $28k in about 6 years with an 8% APR, and saves about $45k in total cost when compared to a regular AC system that cools the same house for the same period of 6 years.
ContributorsJubran, Sadiq (Author) / Phelan, Patrick (Thesis advisor) / Calhoun, Ronald (Committee member) / Trimble, Steve (Committee member) / Arizona State University (Publisher)
Created2011
Description
This study introduces a new outdoor accelerated testing method called “Field Accelerated Stress Testing (FAST)” for photovoltaic (PV) modules performed at two
different climatic sites in Arizona (hot-dry) and Florida (hot-humid). FAST is a combined
accelerated test methodology that simultaneously accounts for all the field-specific stresses
and accelerates only key stresses, such as temperature, to forecast the failure modes by 2-
7 times in advance depending on the activation energy of the degradation mechanism (i.e.,
10th year reliability issues can potentially be predicted in the 2nd year itself for an
acceleration factor of 5). In this outdoor combined accelerated stress study, the
temperatures of test modules were increased (by 16-19℃ compared to control modules)
using thermal insulations on the back of the modules. All other conditions (ambient
temperature, humidity, natural sunlight, wind speed, wind direction, and tilt angle) were
left constant for both test modules (with back thermal insulation) and control modules
(without thermal insulation). In this study, a total of sixteen 4-cell modules with two different construction types (glass/glass [GG] and glass/backsheet [GB]) and two different encapsulant types (ethylene
vinyl acetate [EVA] and polyolefin elastomer [POE]), were investigated at both sites with
eight modules at each site (four insulated and four non-insulated modules at each site). All
the modules were extensively characterized before installation in the field and after field
exposure over two years. The methods used for characterizing the devices included I-V
(current-voltage curves), EL (electroluminescence), UVF (ultraviolet fluorescence), and
reflectance. The key findings of this study are: i) the GG modules tend to operate at a higher temperature (1-3℃) than the GB modules at both sites of Arizona and Florida (a lower
lifetime is expected for GG modules compared to GB modules); ii) the GG modules tend
to experience a higher level of encapsulant discoloration and grid finger degradation than
the GB modules at both sites (a higher level of the degradation rate is expected in GG
modules compared to GB modules); and, iii) the EVA-based modules tend to have a higher
level of discoloration and finger degradation compared to the POE-based modules at both
sites.
ContributorsThayumanavan, Rishi Gokul (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Phelan, Patrick (Thesis advisor) / Calhoun, Ronald (Committee member) / Arizona State University (Publisher)
Created2023
Description
Due to decrease in fossil fuel levels, the world is shifting focus towards renewable sources of energy. With an annual average growth rate of 25%, wind is one of the foremost source of harnessing cleaner energy for production of electricity. Wind turbines have been developed to tap power from wind. As a single wind turbine is insufficient, multiple turbines are installed forming a wind farm. Generally, wind farms can have hundreds to thousands of turbines concentrated in a small region. There have been multiple studies centering the influence of weather on such wind farms, but no substantial research focused on how wind farms effect local climate. Technological advances have allowed development of commercial wind turbines with a power output greater than 7.58 MW. This has led to a reduction in required number of turbines and has optimized land usage. Hence, current research considers higher power density compared to previous works that relied on wind farm density of 2 to 4 W/m 2 . Simulations were performed using Weather Research and Forecasting software provided by NCAR. The region of simulation is Southern Oregon, with domains including both onshore and offshore wind farms. Unlike most previous works, where wind farms were considered to be on a flat ground, effects of topography have also been considered here. Study of seasonal effects over wind farms has provided better insight into changes in local wind direction. Analysis of mean velocity difference across wind farms at a height of 10m and 150m gives an understanding of wind velocity profiles. Results presented in this research tends to contradict earlier belief that velocity reduces throughout the farm. Large scale simulations have shown that sometimes, more than 50% of the farm can have an increased wind velocity of up to 1m/s
at an altitude of 10m.
at an altitude of 10m.
ContributorsKadiyala, Yogesh Rao (Author) / Huang, Huei-Ping (Thesis advisor) / Rajagopalan, Jagannathan (Committee member) / Calhoun, Ronald (Committee member) / Arizona State University (Publisher)
Created2015
Description
About 20-50% of industrial processes energy is lost as waste heat in their operations. The thermal hydraulic engine relies on the thermodynamic properties of supercritical carbon dioxide (CO2) to efficiently perform work. Carbon dioxide possesses great properties that makes it a safe working fluid for the engine’s applications. This research aims to preliminarily investigate the actual efficiency which can be obtained through experimental data and compare that to the Carnot or theoretical maximum efficiency. The actual efficiency is investigated through three approaches. However, only the efficiency results from the second method are validated since the other approaches are based on a complete actual cycle which was not achieved for the engine. The efficiency of the thermal hydraulic engine is found to be in the range of 0.5% to 2.2% based on the second method which relies on the boundary work by the piston. The heating and cooling phases of the engine’s operation are viewed on both the T-s (temperature-entropy) and p-v (pressure-volume) diagrams. The Carnot efficiency is also found to be 13.7% from a temperature difference of 46.20C based on the measured experimental data. It is recommended that the thermodynamic cycle and efficiency investigation be repeated using an improved heat exchanger design to reduce energy losses and gains during both the heating and cooling phases. The temperature of CO2 can be measured through direct contact with the thermocouple and pressure measurements can be improved using a digital pressure transducer for the thermodynamic cycle investigation.
ContributorsManford, David (Author) / Phelan, Patrick (Thesis advisor) / Calhoun, Ronald (Thesis advisor) / Shuaib, Abdelrahman (Committee member) / Arizona State University (Publisher)
Created2020