I heard a lecturer from the neighborhood university earlier this month discuss blue energy. The subject caught my attention because I’ve been looking at alternatives to fossil fuels for electricity sources. Being from Florida, I’m also attracted by the big ocean in front of me.
How can the ocean be used to generate clean energy?
Bill Baxley, the chief engineer of Florida Atlantic University’s (FAU) Harbor Branch, gave a talk on blue energy titled Power from the Gulf Stream: The Potential and Challenges of Developing Blue Energy. Bill has carried out a number of studies to develop the science and technology of collecting energy from the ocean’s renewable resources while working with the Southeast National Marine Renewable Energy Center (SNMREC) at Florida Atlantic University.
The energy of moving seawater is represented by ocean tides, currents, and waves. Even though it is abundant, clean, and sustainable, ocean energy still needs to be turned into electricity before it can displace more conventional energy sources. Technology machines of some type are needed to accomplish this.
Bill uses cutting-edge technology to eliminate barriers one at a time in an effort to extract usable energy from the water, similar to many other blue energy engineers. He claims that although a technology may appear to be intuitive at times, you must also demonstrate it in order to make new technologies suitable to a variety of applications. Data patterns are required for funding in order to devote resources to it.
WHAT EXACTLY IS BLUE ENERGY? Technologies that harness renewable energy from the oceans, excluding wind, are referred to as blue energy, also known as ocean energy. There are several ways to harvest ocean energy:
Wave energy: A function of wave height, speed, and length as well as water density Tidal stream power produced by the water flowing through confined channels Tidal barrages, also known as tidal range technologies: Utilize the difference in surface height in a bay or estuary that has been dammed. Utilizing the differential in temperature between surface and deep water, ocean thermal energy conversion produces energy. Power of the salinity gradient: depends on the salinity differential between salt and freshwater When creating blue energy, there are several factors to take into account. For instance, the height of the tides increases with distance from the equator: 3 feet in Florida, 30 feet in Maine. Renewable energy must also be produced relatively close to where it will be used by a human population in order to be a viable energy source.
Ocean currents and offshore thermal resources that are accessible to the Southeast US are given special attention by the SNMREC.
Observations of the Florida Current’s structure at a large scale show that there is a core of relatively fast (2 m/s) flow near the surface around 20 km off Florida’s southeast coast. The Florida Current’s core is of particular interest to energy developers because the power that can be extracted from a flowing fluid is proportional to the cube of the fluid’s speed, even though most of the water in the Florida Straits flows northward on average.
Since ocean thermal energy operates similarly to conventional electrical power plants, the premise behind it is relatively straightforward.
High-pressure steam is produced by boiling a working fluid (water) with a heat source, such as burning coal. Electricity is generated by turning a turbine and a generator using the high-pressure steam. In conventional power plants, once the steam has passed the turbine, it is cooled back to liquid water using a cold source, typically air. The Rankine Cycle is the name of this procedure. Ocean thermal energy conversion frequently uses a Rankine cycle, in which a working fluid evaporates at the higher temperature and re-condenses at the lower temperature, to drive the temperature differential between warm surface seawater and the cold water near the ocean bottom. Whether it is water or another substance, the generated steam can power a turbine, generator, or other mechanical conversion device.
Consequently, the difference in temperature between the ocean’s surface and deep waters turns into a source of blue energy, or ocean thermal energy.
Possibilities for blue energy are currently present in the Florida Straits. The erratic speed and location of the Florida high-speed core are less fully understood. The community working on ocean energy is very interested in this variability, hence SNMREC has started an observational program employing long-term acoustic current profiler deployments. Similar to how radar uses radio waves in the atmosphere, these devices rely on underwater sound waves.
To determine the current speed and direction throughout the water column, place an upward-looking acoustic current profiler close to the bottom. Every half-hour, these current profiles are measured; utilizing a number of profiling techniques, fluctuations across both time and space can be deduced, analyzed, and evaluated for their potential impact on marine renewable energy recovery.
Aside from acoustic profiling system locations, SNMREC has also set up shore-based radar systems that employ backscattering from the ocean’s surface to infer the surface current over a sizable offshore area. These two methods together offer a more thorough analysis of the Florida Current and its minute fluctuations than was previously possible.
If there is a temperature difference between the surface and deep waters of at least 20C, ammonia/water mixes can be employed as the working fluid at oceanic temperatures. Offshore of southeast Florida, there is potential for ocean thermal energy conversion (OTEC) because to the Florida Current’s consistent supply of warm, tropical water and the Florida Straits’ bottom water’s persistently lower temperature.
What and where are the questions?
SNMREC has started a program of temperature measurements using a typical conductivity-temperature-depth (CTD) equipment that is deployed from a small research vessel to answer this topic. On a monthly basis, cross sections from Miami, Fort Lauderdale, Lake Worth, and Stuart are repeated to measure temperature as a function of depth, or the temperature stratification.
According to preliminary findings, the Miami Terrace, a bathymetric feature that extends from about North Miami to Boca Raton, contains cold water that is present at the bottom of the Florida Straits and is 200 meters deep or closer to the surface.
Due to constancy and minimal influence from Florida or the Bahamas, devices are best positioned near the middle of the Florida Straits.
Sand is used in multibeam mapping to survey a section of the ocean floor. The same data is then replicated using the base map by underwater robots. A habitat map is then created to determine whether any creatures or the seafloor would be harmed.
OCEAN CURRENT GENERATING SYSTEMS IN THE OPEN The relationship between open-ocean current generating systems and the physical environment may be the best example of interactions, especially when commercial-scale deployments are taken into account.
It should be clear that the flow will be impacted in some way if a sizable portion of the kinetic energy of the Florida Currents is removed in order to produce electricity. However, the same cannot be said for the specifics of the flow and its changes. It is possible to claim that the large-scale mechanisms causing the Florida Current will not change, and as a result, the overall amount of water moved northward across the Florida Straits will not alter.
On the other hand, the design of arrays of systems and even the design of individual components like rotors will need to take into account very small-scale variations of the specifics of the flow (i.e., a single turbine system’s wake).
The deep water, the distance from the shore, the ongoing strong flows, the prime flow near the surface, and tropical storms provide difficulties for blue energy study in the Florida Straits.
Given the high cost of real tests, computer simulation is frequently the most effective method for solving these issues. Modern ocean circulation models are being used by SNMREC and the Center for Ocean Atmosphere Prediction Studies (COAPS) at Florida State University to study these interactions. During the procedure, correlations between the power present in the Florida Current and the overall mass transported through the Florida Straits are being discovered. This information will help architects of future strategies.
Author: Southeast National Marine Renewable Energy Center
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