Ocean Thermal Energy: Principles and Applications

MECH 4354 ENERGY & ENVIRONMENT MECH 4384 RENEWABLE ENERGY TENGKU NORDAYANA AKMA BINTI TUAN KAMARUDDIN © E1-5-2.14 [email protected]...

MECH 4354 ENERGY & ENVIRONMENT MECH 4384 RENEWABLE ENERGY TENGKU NORDAYANA AKMA BINTI TUAN KAMARUDDIN © E1-5-2.14 [email protected] 1  Week 8: OCEAN THERMAL ENERGY Principles OTEC system OTEC types Advantages Disadvantages OTEC development 2 OCEAN THERMAL ENERGY CONVERSION [OTEC] 3  - World’s oceans = natural reservoir for receiving & storing the energy of the sun incident on earth INTRODUCTION - Water near the surface of tropical seas is maintained by this solar radiation at higher temperatures than the water at greater depth or higher altitudes - OTEC utilises the temperature difference between the warm surface ocean water and cold deep ocean water to generate electricity 4 Principles For OTEC to produce a net output energy, the temperature difference between the surface water and water at a depth around 1000 m needs to be about 20 °C. OTEC = a heat engine that operates at the modest temperature differential available. Using ammonia as the working fluid, because it vaporises and condenses at the available temperature of the ocean. 5 OTEC System Tc = cold temperature Th = Tc + ∆T = hot temperature A working fluid circulates in a closed cycle and takes up heat from the warm water through a heat exchanger. As the fluid expands, it drives a turbine, which in turn drives a generator. The working fluid is cooled by the cool water and the cycle continues. 6 Po = Power given up from the warm water Q = ( V / t ) = volume flow rate of warm water passes into the system at temperature Th and leaves at Tc Real engines do not follow the carnot cycle but may operate closer to the ideal Rankine cycle The maximum output of mechanical power that can be obtained from the heat flow, Po is The ideal mechanical output power is 7 Example: 8  OTEC TYPES 1. Closed Cycle Uses a working fluid with a low boiling point (e.g. ammonia) Main components: evaporator, turbine, condenser, pump Process: - Warm surface seawater evaporates the working fluid in the evaporator - Vaporized working fluid drives a turbine connected to a generator - Cold deep seawater condenses the vapor back to liquid in the condenser - Pump recirculates the liquid working fluid back to the evaporator 9  10 OTEC TYPES 2. Open Cycle  11 OTEC TYPES 3. Hybrid Cycle OTEC ADVANTAGES: OTEC produces electricity without burning fossil fuels, resulting in no carbon emissions or other harmful byproducts. It utilizes the vast thermal energy stored in the oceans, which is continually replenished by solar heating. Unlike intermittent renewable sources such as solar or wind, OTEC can provide continuous power 24/7 and year-round. This makes it suitable for baseload electricity needs, especially for tropical islands with small electricity networks. OTEC systems can produce several valuable byproducts in addition to electricity: Fresh Water: Open-cycle OTEC systems can produce desalinated water as a byproduct. Cooling: The cold deep seawater can be used for air conditioning and refrigeration. Aquaculture: Nutrient-rich deep seawater can support fish farming and seawater-cooled greenhouses. The oceans cover more than 70% of Earth's surface, storing an enormous amount of thermal energy. Estimates suggest that OTEC could potentially generate 3-5 terawatts of baseload power, about twice the global electricity demand. 12  OTEC DISADVANTAGES: OTEC systems require significant upfront investment for construction and deployment, particularly for offshore installations. This can make it economically challenging, especially for developing nations. OTEC is only viable in regions with a temperature difference of at least 20°C between surface and deep waters, limiting its application primarily to tropical areas. OTEC systems are complex and require specialized engineering expertise. They involve large turbines, extensive piping systems, and the need to pump large volumes of cold water from great depths. While generally environmentally friendly, OTEC systems may have some impacts on marine ecosystems. Due to the relatively small temperature difference between warm and cold water, OTEC systems have low thermal efficiency compared to conventional power plants. Offshore OTEC plants may face challenges related to power transmission to shore and could potentially interfere with ship navigation. 13 OTEC Development The world's largest operational OTEC power plant is located at the Natural Energy Laboratory of Hawaii Authority (NELHA) in Kailua-Kona, Hawaii. Has an annual power generation capacity of 100kW, enough to power approximately 120 homes in Hawaii Was connected to the US grid in August 2015 Provides baseload power, generating electricity 24 hours a day, 365 days a year 14  Location: São Tomé and Príncipe (African island nation) Global OTEC's Planned capacity: 1.5 MW Expected completion: 2025 Dominique Notable features:Will be the first commercial-scale OTEC platform Project Designed to provide nearly 17% of the nation's entire energy consumption 15 TIDAL ENERGY Tidal energy is a renewable power source that harnesses the natural rise and fall of ocean tides to generate electricity. Here's a summary of its key aspects: Tidal energy systems typically use one of three methods: Tidal Barrages: Dam-like structures across estuaries that use the difference in water levels to drive turbines. Tidal Stream Generators: Underwater turbines that capture energy from tidal currents. Dynamic Tidal Power: A theoretical method using long dams extending from the coast into the ocean. 16  17 TIDAL PROJECTS WAVE ENERGY Wave energy is a renewable power source that harnesses the kinetic energy of ocean waves to generate electricity Wave energy converters (WECs) are devices placed in the ocean to capture wave motion and convert it into electrical or mechanical power. Various designs exist, including floating platforms with internal gyroscopes, oscillating water columns, point absorbers, overtopping devices 18 WAVE PROJECTS Mutriku Wave Power Plant, Spain. Capacity: 300 kW. Uses oscillating water column technology Perth Wave Energy Project, Australia. Located off the coast of Garden Island. Aims to integrate wave energy into the national grid Okinawa Wave Energy Plant, Japan. Designed to withstand typhoons while harnessing wave power. Demonstrates Japan's commitment to exploring various renewable energy sources 19 THANK YOU 20