Question

Explain how these forms of energies are formed with their advantage and disadvantage?
a) ocean thermal energy
b) wave energy
c) tidal energy

Answer 1

a) Ocean Thermal Energy Conversion (OTEC) is a process that can produce electricity by using the temperature difference between deep cold ocean water and warm tropical surface waters. OTEC plants pump large quantities of deep cold seawater and surface seawater to run a power cycle and produce electricity.

Advantages

OTEC sounds immensely attractive: it's clean, the green renewable energy that doesn't involve burning fossil fuels, producing large amounts of greenhouse gases, or releasing toxic air pollution. By helping to reduce our dependence on fuels such as petroleum, OTEC could also help to reduce the "collateral" damage the world suffers from an oil-dependent economy—including wars fought over oil and water pollution from tanker spills. It could also provide a very useful source of power for tropical island states that lack their own energy resources, effectively making them self-sufficient. As we've already considered, open-cycle OTEC can play a useful part in providing pure, usable water from ocean water. OTEC can also be used to produce fuels such as hydrogen; the electricity it generates can be used to power an electrolysis plant that would split seawater into hydrogen and oxygen, which could be bottled or piped ashore and then used to power such things as fuel cells in electric cars. The waste cooling water used by an OTEC plant can also be used for aquaculture (growing fish and other marine food such as algae under controlled conditions), refrigeration, and air conditioning.

Disadvantages

The biggest problem with OTEC is that it's relatively inefficient. The laws of physics (in this case, the Carnot cycle) say that any practical heat engine must operate at less than 100 percent efficiency; most operate well below—and OTEC plants, which use a relatively small temperature difference between their hot and cold fluids, have the lowest efficiency of all: typically just a few percent. For that reason, OTEC plants have to work very hard (pump huge amounts of water) to produce even modest amounts of electricity, which brings two problems. First, it means a significant amount of the electricity generated (typically about a third) has to be used for operating the system (pumping the water in and out). Second, it implies that OTEC plants have to be constructed on a relatively large scale, which makes them expensive investments. Large-scale onshore OTEC plants could have a considerable environmental impact on shorelines, which are often home to fragile, already threatened ecosystems such as mangroves and coral reefs.

b) Wave power is the transport of energy by wind waves, and the capture of that energy to do useful work – for example, electricity generation, water desalination, or the pumping of water (into reservoirs). A machine able to exploit wave power is generally known as a wave energy converter (WEC).

Advantages

It’s highly predictable: The wave arrival pattern is highly predictable. They arrive day and night and harbor more energy than other renewable sources like wind and solar. Wind energy and solar energy, on the other hand, are highly unpredictable. Wind speeds die down unexpectedly, which affects the generation of electricity. Solar energy depends upon exposure from the sun, which means cloud coverage and night hours significantly reduce this exposure leading to less efficiency.

It’s a renewable form of energy: Renewable means it’s an endless resource. It does not need man’s intervention to continue existing. No one has dared to suggest that the oceans and seas will disappear someday. Humans will continue harnessing it to the very end. This aspect makes wave energy a reliable and efficient energy resource.

Wave energy is eco-friendly: Wave energy is a completely clean energy source, which means, it does not emit dangerous greenhouse gasses to the atmosphere. Fossil fuels, for instance, oil, coal and natural gas contribute mightily to environmental pollution because they release dangerous greenhouse gasses including carbon dioxide, nitrous oxide, methane, and ozone to the atmosphere.

Creation of green jobs: Communities living in remote areas and declining industries like the ship building industry bear the biggest brunt of unemployment and economic unsustainability due to lack of electricity. The wave energy sector has the potential to create numerous green opportunities to remote and urban population alike because remote areas that are not able to be reached by conventional electricity supply are well catered by wave power.

Exponential growth of remote areas: The wave energy harnessed can to channelled to remote locations, and this means springing up of industries and businesses. These remote areas will witness strong economic growth moving forward.

Security of energy supply: Setting up a strong wave energy infrastructure can enormously help a country from overdependence on fossil fuels. The fossil fuel market is largely volatile and could hurt a country’s economy if shortage occurs. Wave energy is the surefire way to bridge this volatility gap since it’s cheap, reliable and efficient.

Land remains undamaged: Wave energy plants can be situated offshore alleviating any risk that comes along with these plants situated onshore like soil pollution. Also, the land remains in its natural state unlike fossil fuel extraction, which requires high levels of excavation that leaves land heavily damaged.

Disadvantages

High upfront capital costs: Construction of wave energy plants requires huge capital outlay. Energy plant maintenance, connection to power grid, wave resources, expected drop in energy costs once the infrastructure is up and running and shelf life of the technology are just some of the variables driving up the cost of wave energy. Determination of actual cost is also difficult since wave energy is in its early stage of development.

Variability in wave magnitude can damage equipment: The wave magnitude is so unpredictable in the seas. Sometimes it comes with a vengeance and could cause heavy wear and tear to the wave energy generation turbines. Damage to these equipment can be costly in terms of repair. It would also mean stalling of electricity supply.

Damage to sea life ecosystem: Offshore wave energy projects are a lot more sophisticated than onshore ones. The projects include platforms, cables, turbines, interconnections, dredging and much more. From ecological standpoint, shallow waters are fertile breeding and resting grounds for most marine life. So, activities from construction and operation of the wave energy plant greatly affect marine ecosystem. Accidental leaks or spills emanating from hydraulic fluids in the plants could potentially pollute the water resulting in marine life deaths.

Disadvantage of location: The downside to wave energy is the location. Individuals or towns in proximity to oceans and seas will enjoy the fruits of wave energy. Because the source of wave energy is restricted to oceans and seas, it can’t be relied upon to serve the entire population of a country. This means that towns, cities, and countries not close to such water bodies don’t get to enjoy the fruits of wave energy.

Environmental concerns: Although wave energy is a clean energy source, the sound produced by the plant generators could prove unbearable to some local residents. The plants also interfere with the natural aesthetic look of the ocean. However, the noise of the waves, in most occasions, equalizes the noise produced by the generators.

c) Tidal power or tidal energy is a form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity. Although not yet widely used, tidal energy has the potential for future electricity generation. Tides are more predictable than the wind and the sun.

Advantages

Tidal energy is a renewable energy resource because the energy it produces is free and clean as no fuel is needed and no waste bi-products are produced.
Tidal energy has the potential to produce a great deal of free and green energy.
Tidal energy is not expensive to operate and maintain compared to other forms of renewable energies.
Low visual impact as the tidal turbines is mainly if not totally submerged beneath the water.
Low noise pollution as any sound generated is transmitted through the water.
High predictability as high and low tides can be predicted years in advance, unlike wind.
Tidal barrages provide protection against flooding and land damage.
Large tidal reservoirs have multiple uses and can create recreational lakes and areas where before there were none.

Disadvantages

Tidal energy is not always a constant energy source as it depends on the strength and flow of the tides which themselves are affected by the gravitational effects of the moon and the sun.
Tidal Energy requires a suitable site, where the tides and tidal streams are consistently strong.
Must be able to withstand forces of nature resulting in high capital, construction and maintenance costs.
High power distribution costs to send the generated power from the submerged devices to the land using long underwater cables.
Intermittent power generation only generates power ten hours a day during the ebb and flow of the tides
Changes to estuary ecosystem and an increase in coastal erosion where the tides are concentrated.
Build up of silt, sediments and pollutants within the tidal barrage from rivers and streams flowing into the basin as it is unable to flow out into the sea.
The danger to fish and other sea-life as they get stuck in the barrage or sucked through the tidal turbine blades.