scholarly journals Affects of the Cold Water Pipe Depth in Ocean Thermal Energy Converter Plants with respect to Power Generation Efficiency

2015 ◽  
Vol 2 ◽  
pp. 50-66 ◽  
Author(s):  
Helia Danielle Giordani ◽  
Matheus Lages ◽  
Miguel Medina ◽  
Jade Tan-Holmes
Keyword(s):  
Power Generation ◽  
Surface Water ◽  
Thermal Energy ◽  
Power Efficiency ◽  
Cold Water ◽  
Mechanical Energy ◽  
Heat Engine ◽  
Water Pipe ◽  
Generation Efficiency ◽  
Ocean Thermal Energy

The Ocean provides an extensive renewable energy source. It is the exploitation of the thermal gradient between the warmed surface water and the deep cold water. A heat engine was developed to use the surface water as a heat source and the deep water as a cold source in order to convert thermal energy into mechanical energy and generate electricity. This process is called Ocean Thermal Energy Conversion (OTEC). This paper presents the three different types of OTEC power plants: closed-cycle, open-cycle and hybrid-cycle, showing real and conceptual examples of each. All three systems are analyzed in terms of gross power, net power, efficiency and size. Furthermore, the depth of the cold water pipe is discussed and related to the net power generation of the OTEC plant. The power generation efficiency of the plant increases as the gross power production increases. This is due to the depth of the cold water pipe and amount of power used by the cold water pipe pump.

A Jet Condenser for Ocean Thermal Energy Conversion

1982 ◽  
Vol 104 (3) ◽  
pp. 153-157
Author(s):  
H. J. Richter ◽  
G. B. Wallis
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Cold Water ◽  
Mechanical Energy ◽  
Water Stream ◽  
Ocean Thermal Energy Conversion ◽  
Available Energy ◽  
Thermal Energy Conversion ◽  
Water Turbine ◽  
Ocean Thermal Energy

A novel idea to use a jet condenser for Ocean Thermal Energy Conversion (OTEC) plants is presented here. The jet condenser offers the advantage of a relatively simple device. It consists of a mixing section where the partially evaporated warm water and the cold water mix and condensation takes place. After the complete condensation, the water stream is employed to drive a water turbine. The basic thermodynamic principles are evaluated. Introducing realistic efficiencies for the jet condenser, about 20 to 25 percent of the available energy can possibly be expected to be converted into mechanical energy.

scholarly journals FLOW FIELD NEAR AN OCEAN THERMAL ENERGY CONVERSION PLANT

1976 ◽  
Vol 1 (15) ◽  
pp. 174 ◽  
Author(s):  
D.M. Sheppard ◽  
G.M. Powell ◽  
I.B. Chou
Keyword(s):  
Low Temperature ◽  
Shear Flow ◽  
Flow Field ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Temperature Difference ◽  
Cold Water ◽  
Water Pipe ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

The flow field in the vicinity of an Ocean Thermal Energy Conversion (OTEC) Plant is extremely complex. The plants will normally be located in an area of relatively high surface currents and the location must also be such that a large temperature difference exists between the lower layers and the surface. Locations that demonstrate this characteristic can in many cases be modeled as a two layer fluid as shown in Figure 1. A number of different designs for the OTEC plants are being considered, but they all have one thing in common, a large vertical cold water pipe. This pipe extends from near the surface to some point in the cold water layer (see Figure 1). In some designs this pipe is as large as 40 m in diameter and 460 m in length. Having such a large object penetrating the interface between the two temperature layers in the presence of a shear flow can significantly alter the character of the interface. The highly turbulent wake downstream from the pipe can drastically effect the mixing across this density interface. A conventional heat engine cycle is used in the plant with the high temperature source being the water in the upper layers and the low temperature reservoir being the water from the lower depths. \ Since the temperature difference is small for this type of plant (20° max.), vast quantities of both high and low temperature water must be used. The intake and discharge for the warm water as well as the cold water discharge will be in the upper layer; the intake for the cold water will be in the lower layer at or near the end of the cold water pipe. The flow problem is thus one of a vertical cylinder in a two layer stratified shear flow with sources and sinks located along the cylinder.

Current Developments in the Validation of Numerical Methods for Predicting the Responses of an Ocean Thermal Energy Conversion (OTEC) System Cold Water Pipe

2014 ◽  
Author(s):  
John Halkyard ◽  
Rizwan Sheikh ◽  
Thiago Marinho ◽  
Shan Shi ◽  
Matthew Ascari
Keyword(s):  
Numerical Methods ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Cold Water ◽  
Oil Prices ◽  
Model Tests ◽  
Water Pipe ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Ocean Thermal Energy Conversion (OTEC) was a subject of intense research in the late 1970s and early 1980s in response to a historical jump in oil prices from the 1973 oil embargo. The principal author for this paper first met Prof. Paulling as a participant in a National Research Council (NRC) Panel to review OTEC Technology around 1982. Prof. Pauling had authored a frequency domain program to analyze the coupled response of a platform and OTEC pipe. The author was involved in model tests to validate the program. The United States (U.S.) Department of Energy (DoE) and National Oceanic and Atmospheric Administration (NOAA) had sponsored this work, along with the development of other numerical methods. Shortly after the NRC completed its review, oil prices fell and interest in renewable energy, including OTEC, evaporated. Fast forward to the 2000s, the price of oil skyrocketed again, and OTEC research saw a rebirth. Lockheed Martin and others have been working on new OTEC designs over the course of the last several years. As was the case thirty-five years ago, the cold water pipe remains a key technical challenge. A commercial scale OTEC plant requires a pipe diameter of about 10-meter (m) and a length of 1,000m to pump about half the average discharge of the Colorado River from the deep ocean to the surface and through heat exchangers. Because of the large effective mass of the CWP and entrained water, the dynamic response of the OTEC CWP and the platform can only be considered as a coupled system. This conclusion is not new, but is worth repeating and doubly important to consider when the supporting platform is a semi-submersible as opposed to a large water plane ship shaped vessel. A new generation of software is available to analyze the cold water pipe-platform responses, including the important effect of the fluid flow inside the pipe and the local effects at the connection of the pipe to the platform. The DoE and Lockheed Martin recently sponsored a 1:50 scale wave basin model test of a commercial OTEC platform with an elastically scaled model of a 10m pipe. The purpose of the test was to validate the use of current software for the large CWP diameters in the designs of a pilot or commercial systems in the near future. This paper will briefly review past work on the OTEC cold-water pipe and present the current state of the art in numerical modeling and the results of the model tests recently completed. It will include recommendations for further experimental and numerical work to be prepared for the future design of OTEC systems.

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