Workshop Energy is Young Cosenza, 15-22 October 2007 ___________________________________

1. Workshop “Energy is Young” – Cosenza, 15-22 October 2007___________________________________ Renewable energy sources - Fonti di energia rinnovabili Ocean Thermal Energy Conversion - OTEC

2. “The more we use renewable energy, the more we benefit the environment, strengthen our energy security, create jobs locally, and help improve our economy. “

3. Why this topic? Interesting engineering idea Interesting history Very young technology, a lot of place for further research Something YOU can get involved in Sustainable, environmental-friendly process Promising technology

4. Benefits of OTEC: 1. Clean energy production  OTEC has remarkably little adverse environmental impact, especially compared with other energy sources of comparable size.  OTEC is inherently not exothermic, so it does not adversely contribute directly to global warming, as do, for example fossil fueled and nuclear plants.  Nearly all human energy requirements can be supplied from this one source without significantly affecting the overall temperature structure of the ocean.  Since the cold or mixed water will be discharged at depth, impacts on the atmospheric temperature or concentration of carbon dioxide, a greenhouse gas, will be minimal;

5. Benefits of OTEC: 2. Fresh water production  OTEC plants can produce fresh water as well as electricity.  Open-cycled and hybrid plants can directly produce fresh water as well as electricity and closed-cycle plants can produce similar volumes by condensation from the atmosphere.  This is a significant advantage in island areas or deserts were fresh water is limited;

6. Benefits of OTEC: 3. Continuous power Unlike most other sources of renewable energy which vay with weather and time of day, OTEC power plants can produce electricity 24 hours a day, 365 days per year.  Since the ocean doesn't change temperature at night, the solar energy stored in the seas is always available;

7. Benefits of OTEC: 4. Energy independence  OTEC plants built on the coast or moored offshore could provide enough power and water to make tropical areas independent of costly fuel imports;

8. Benefits of OTEC: 5. Aquaculture enterprises  Deep seawater discharged from an OTEC plant is cold, rich in nutrients, relatively free of pathogens, and available in large quantity.  This is an excellent medium for growing phytoplankton (microalgae), which in turn can support the production of a variety of commercially valuable fish and shellfish.  Suitable mixing of the warm and cold water discharges, can provide large volume flows of seawater at any temperature between those of the surface and deep seawater, allowing temperature optimization throughout the growth cycle of cultured organisms -merely by turning a valve;

9. Benefits of OTEC: 6. Air-conditioning/refrigeration The deep-ocean cold water can be used as a chiller fluid in air-conditioning systems.  For example, only 1 m3 s-1 of 7°C deep ocean water is required to produce 5800 tons (roughly equivalent to 5,800 rooms) of air conditioning.  This will typically require a pipeline about 1 m in diameter and the pumping power required will be about 360 kW, compared to 5000 kW for a conventional AC system.  The investment payback period for a stand-alone air-conditioning system can be as little as 3 to 4 years, depending on the specifics of the pipeline installation.  Combining the air-conditioning with OTEC and/or aquaculture systems can make the technology even more attractive.   Implementation of the first Sea Water Air Conditionning system (SWAC) at the InterContinental Bora Bora Resort & Thalasso Spa Space cooling is by far the most economically valuable use of deep cold seawater available now;

10. Benefits of OTEC: 7. Mineral extraction OTEC systems could not provide the opportunity to mine for some of the elements in the ocean water solution.  In the past, most economic analyses showed that mining the ocean for trace elements dissolved in solution would be unprofitable because so much energy is required to pump the large volume of water needed and because it is so expensive to separate the minerals from seawater.  However, because OTEC plants will already be pumping the water, the cost of the extraction process is the only remaining factor.  Investigations are underway to determine the feasibility of combining the extraction of uranium dissolved in seawater with ocean energy production [20]. 

11. OTEC Integrated System – “The big picture”

12. OTEC Drawbacks: Low efficiency High capital costs for initial construction Potential ecological consequences Siting considerations Must operate in a corrosive marine environment

13. Find your place…

14. Further reading & References Books Ocean Thermal Energy ConversionISBN: 0-471-96009-8Publishers: John Wiley & Sons, 1996Authors: Patrick Takahashi, Andrew TrenkaThis book is part of the UNESCO Energy Engineering Series, a distance learning package. It provides a good overview of OTEC and other ocean energy technologies. It has sections on economics as well as OTEC thermodynamics. This 75 page "booklet" is recommended to anyone who wants to get a quick overview, which also has some in-depth material. Decently priced. Renewable Energy from the OceanA Guide to OTECISBN: 0-19-507199-9Publisher: Oxford University Press, 1994Authors: William H. Avery, Chih WuThis is the "bible" in OTEC technology. Written by two very qualified professionals, an in-depth study of OTEC. This book supposedly is getting a bit long in the tooth, but gives unrivaled background and in-depth information on the subject. Not cheap, but worth it. References A lot of material, complete list available by request…

15. Questions & Comments… Thank you!