Source:JASE-W Japanese Smart Energy Products & Technologies

https://www.jase-w.eccj.or.jp/technologies/index.html

E-44

Keywords

Y2

deviceZ4

electricity

S5

renewable energy

E29electrical machinery
Yokogawa Electric Corporation

Yokogawa’s CENTUM VP Utilized at World’s Only Fully Operational
Ocean Thermal Power Generation Facility
Okinawa Prefecture’s efforts to achieve a low carbon society
Okinawa Prefecture is promoting clean energy with the aim ofbecoming a low-carbon society in the 21st century. Ocean thermalenergy conversion (OTEC) technology is particularly well suited forthis purpose, and is expected to both reduce the environmental
impact that power generation has in the prefecture and lessen theprefecture’s dependence on imported fossil fuels.

To prove the viability of this technology, Okinawa Prefecture has built an OTEC demonstration facility at its
Deep Sea Water Research Center on Kume Island, which lies approximately 100 km west of Okinawa
Island. The island enjoys a subtropical, temperate climate throughout the year, with an average temperatureof 22.7° C. In addition to the generation of electricity, the cold water from this facility is used in agriculture,aquaculture, and other industrial applications.
OTEC, a renewable energy source for the future
An OTEC system utilizes the temperature differences between warm surface seawater and cold deep
seawater to generate electricity. Chlorofluorocarbon (CFC), a low-boiling-point working fluid, is pumped into an
evaporator, where the transfer of heat from the warm surface seawater (normally 25 °C - 30 °C) to the working
fluid causes the fluid to vaporize. The vapor drives a turbine to generate electricity. Then, the vapor istransferred to a condenser where it is returned to a liquid state as the result of the transfer of heat to cold
seawater that has been taken up from ocean depths of 600 - 1,000 meters and is 5 °C - 7 °C. This OTEC
technology is regarded as one of the most effective methods for utilizing the ocean’s thermal energy, and it ismost suitable in tropical and subtropical regions, where the temperature differences between deep seawaterand surface seawater is the greatest.
There is considerable interest in capitalizing on OTEC’s potential as a clean, renewable source, and rapid
progress in the research and development of practical applications of this technology is being made in Japanand other countries. According to a Renewable Energy Technology White Paper prepared by the Japanese’s
government’s New Energy and Industrial Technology Development Organization (NEDO), total installed OTEC
capacity worldwide is expected to reach 510 MW by 2020, 2,550 MW by 2030, and 8,150 MW by 2050.

The world’s only fully operational OTEC plant
The demonstration facility on Kume Island has an initial maximum output of 50 kW (expandable to 100 kW)
and its dimensions are 9 m x 8 m x 8 m. CFC is used as the heat medium. All electricity generated by thisfacility is used by the research center.
The goals for this facility are to obtain data that will show how reliable the technology is and predict its
performance in a commercial scale operation, and to demonstrate its ability to operate continuously for long
periods of time. Data is also being collected on the fluctuations in output caused by changes in air and watertemperature. The insights gained through the analysis of these results will be used to improve the designs ofcommercial-scale plants.

Background of CENTUM VP installationTogether with IHI Plant Construction Co., Ltd. and Xenesys Inc., Yokogawa Electric Corporation submitted
a proposal for the Okinawa prefectural government’s Fiscal Year 2012 Experimental Deep Seawater Power
Generation Project. Upon attaining project approval, Yokogawa successfully delivered, installed, andcommissioned the CENTUM VP production control system (PCS) and a variety of field instruments for thisdemonstration facility.

Role of CENTUM VP and result of the installation
To most effectively utilize the heat energy stored in the ocean
water, the operation of the OTEC facility’s water intake, wastewater, heat exchanger, and generator equipment must be carefully
monitored and controlled. The CENTUM VP PCS and field
instruments installed by Yokogawa help to keep this facility
operating stably and generating power at peak efficiency.
As this is an experimental facility, the control strategy must
continually be refined while the plant is in operation. Changes tomultiple PID control loops also necessitate frequent softwarechanges. With CENTUM VP, it is possible to do this without
disrupting the operation of the facility.
The acquisition of data and its analysis are also important. CENTUM
Human machine interface station
VP not only facilitates the collection of this data, it automaticallywith specialized keyboard
saves it in standard format files for use in the analysis process.
Testimonials "Okinawa Prefecture is mainly dependent on imported fossil fuels. In order to promote the useof clean energy and improve its energy self-sufficiency, the prefectural government is carrying out these fieldtrials on Kume Island to demonstrate the practicality of ocean thermal power generation. We are also
exploring multiple uses for deep seawater. I hope that ocean thermal power plants can enter commercial
use, and that other industrial uses can be found for the deep seawater, thereby promoting the developmentof industry. That is the Kume Island Model."Katsuya Furugen and Motohiro Nagamine of the Okinawa Prefectural Government, Department ofCommerce, Industry Policy Division"Ocean thermal energy conversion is the core element of the Kume Island Model. In the future, we plan to relyon ocean thermal power generation to meet baseload power demand, and aim to develop solar and wind
power so that we can meet 100% of our energy needs with renewable energy. That’s why we are engaged inthis experiment. In addition, we are looking for other ways to make efficient use of deep seawater. For example,
even after it is used to generate power, it is still cool enough to be used to chill soil and enable the growth ofspinach and other kinds of produce. As declared at our "Island Yuntaku" conference, we will continue toengage in activities by which we will benefit from our ocean resources and create a bright future for our island.""When we first used CENTUM VP, we were immediately impressed with how easy to use it was. Using thekeyboard, we could quickly call up the screens we wanted to see, and could easily access other screensfrom the alarm message screen. Operating the demonstration facility was stress free. We hope to keep
working on such projects with Yokogawa Solution Service Corporation. We want to play a leading role inspreading the use of the OTEC technology.”

Effects or Remarks
This OTEC system utilizes the temperature difference between warm surface seawater and cold deep
seawater to generate electricity.
So less CO2 emission and this is environmental friendly system. And this generates electricity regardless ofday and night without any using fossil fuel. This is a new technology for saving energy.
And this technology contributes to not only generating electricity but also growing new marine industry using
deep seawater and spread of local employment.
Contact:

Yokogawa Electric Corporation
Renewable Energy, Power & Water Business Center, Energy & Sustainability Business Headquarters
Tel: +81-422-52-5637
E-mail: GPSC-CONTACTUS@yg.jp.yokogawa.com
URL: https://www.yokogawa.com/industries/power/E-44