Question

Pick one of the following topics on energy. Report back to class with a 3 to 5 paragraph mini-report in essay format on what you found including your own thoughts as to the time frame of if/when the energy source may become more commonplace. Your mini-essay should also contain a paragraph relating your alternate energy source to the chemistry concepts we've learned in lecture material, for example - discuss a balanced reaction, the chemical structure of the materials involved in the energy source, etc. Comment on two other postings. Only 2 people may choose the same topic but have different "takes" on the energy source. If you'd like to propose your own topic, please obtain approval from your instructor first. Please use as current sources as possible. Highlight your discussion post with a picture if you can find one! Don't forget to include the source for your picture as well. Use the discussion thread "Topic Selection" to make sure your topic hasn't been taken! If you don't see a "topic selection" thread, start one! Burning garbage for fuel Hydrocarbon fuels from algae Using excess heat or movement/vibrations to generate energy (up to 4 people can choose this topic as long as the focus is a completely different technology) Modifying our road/highway system to generate electricity from movement Thorium based nuclear energy Generating electricity from rain Using wood waste as a biofuel Ocean hydroelectric power "Paintable" solar-cells Geothermal Power Hydrogen to power vehicles sky windmills

Answer 1

Ocean thermal energy conversion (OTEC)

OTEC is actually one of the simplest types of renewable energy.

OTEC uses the principle of a heat engine. It works by converting a temperature difference into energy. This means the difference in temperature between the warmer water on the surface and the cooler water in the depths of the ocean can be converted into electricity.

OTEC can be sorted into two different types; both generate electricity using the thermal, or heat, energy of the oceans but do it in different ways.

Closed cycle system. The first type is known a closed cycle system. The warmth of the sea water from the surface causes a liquid with a lower boiling point than water, for example ammonia, to boil and turn to vapour. This vapour then drives a turbine which turns a generator, creating electricity.

Then the cold sea water from the depths of the ocean is used to cool the ammonia vapour back into a fluid. It is then recycled back through the system again.

Open cycle system. The second type is an open cycle system. The open cycle system uses the warm water from the surface, instead of ammonia used in the closed cycle system.

The water from the surface is put into a near vacuum. A near vacuum is a container which has had most of the air sucked out of it. This allows the water from the surface to turn into steam, because when water is in a near vacuum its boiling temperature is lower.

The steam goes on to drive a turbine, which is connected to a generator, making electricity just like in the closed-cycle system.

The steam is cooled back into a liquid using the cold water from the depths of the ocean in a condenser. The steam is now almost pure fresh water and has lost all its salt.

If the cooled steam can be kept separate from the cold sea water, it can be used for drinking water or even irrigation. However, if the cold sea water and cooled steam mix, the result is salty water. The salty water produces more electricity compared to fresh water, but has to be returned to the ocean and cannot be used for drinking water.

If both the open and closed systems are combined together, a hybrid system is created. This improves the amount of electricity and fresh water produced.

Advantages of OTEC

 Has the potential to generate large amounts of electricity

 Can create cold fresh water, which can be used for air-conditioning or drinking water.

 Has no emissions

Disadvantages of OTEC

 Large temperature difference required, therefore limited to tropical regions

 Not particularly energy efficient

 Getting water from the depths of the ocean is a difficult engineering challenge

 Have to transmit electricity large distances to get it onshore