The Ocean for Power Generation

Posted by zichi Lorentz

 
 

Current Status: No commercial power plant using the energy from currents, tides or waves has yet been built in Japan, although large tidal-power plants do exist in other countries. Experimental wave-power generators have been set up in Yamagata, Mie, Hokkaido and locations in several other prefectures.

Potential: Even though Japan is surrounded by water, there are just a handful of sites with tides fast and wide enough to generate electricity. According to Ehime University ocean-power researcher Takayuki Nakamura, tides in the Seto Inland Sea (between Honshu, Kyushu, and Shikoku) and Kyushu's Ariake Sea could generate about 3,000 MW — equivalent to the capacity of three nuclear reactors.

Technology to exploit energy in waves is further from commercialization, but the ultimate potential is greater. Scientists have estimated that waves off the eastern coast of Japan and in the Sea of Japan to the west could generate more than 40,000 MW. The powerful Kuroshio Current — which flows from off Taiwan and then along Japan's eastern coast from Kyushu to Tokyo — could also eventually generate significant power, Nakamura said.

How it works: Researchers have experimented with many different ways of harnessing energy from waves. Some use the bobbing motion to power a pump, while others funnel water through chambers with turbines in them or force it up a channel to an elevated onshore reservoir, which then releases water back down through turbines.

Tidal generators can look like turnstiles, underwater windmills, or dams with turbines in them surrounding tidal flats. However, only certain locations have tidal ranges between high water and low water that are wide enough, or tides fast enough, to generate electricity.

Ocean current power systems — some of which resemble underwater windmills anchored to the ocean floor — are at a very early stage of development.

A fourth technology, called ocean thermal-energy conversion, uses warm surface water to produce steam, either by lowering the pressure of the water or by using it to heat another liquid with a lower boiling point, such as ammonia. The steam spins a turbine and is then cooled using water from deep below the surface.

Analysis: Ocean power has received comparatively little support or attention in Japan, and researchers still need to figure out how to make underwater turbines storm resistant and affordable.

"Not to mince words, we're losing out to Europe and the United States," Ehime University's Takayuki Nakamura said. With some technologies about five years from commercialization, researchers are lobbying to have ocean power included in the support system for new energy.

Ocean-power proponents must also negotiate with fishermen's unions, who hold usage rights over coastal areas and are generally afraid that clusters of underwater turbines could harm fish.

Currently, Nakamura is working on a system that could be installed on the seaward side of the concrete breakwaters that line most of Japan's coastline and are meant to absorb the potentially destructive energy in waves. The turbine in this system would turn that energy into electricity while avoiding any new damage to marine habitats.

Unattributed information in this article is from "Kaiyou Enerugī Riyou Gijutsu" ("Technology for Utilizing Ocean Energy"), Morikita Publishing (1996 ).

SUNDAY TIMEOUT

Powering Japan's future

By WINIFRED BIRD

Wind

By WINIFRED BIRD

Sunlight

By WINIFRED BIRD

Biomass

By WINIFRED BIRD

Geothermal

By WINIFRED BIRD

Freshwater

By WINIFRED BIRD

Distribution gridlock restricts renewables

By WINIFRED BIRD
via search.japantimes.co.jp

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Biomass Japan

Posted by zichi Lorentz

 
 

Current Status: After hydroelectric plants, biomass is Japan's renewable electricity powerhouse.

News photo
Waste not ... : A biomass power plant. KAWASAKI BIOMASS ELECTRIC POWER CO., LTD.

The country has 190 generators at municipal waste incinerators, 70 other biomass power plants, and 14 that burn both coal and biomass. In 2009, they together generated 1 percent of the country's total electricity and nearly a third of its electricity from renewable sources. More than half of that came from processing industrial waste, 40 percent from municipal waste, and 4 percent from "woody biomass" like trees and brush.

A 33 MW biomass power plant — which yields enough electricity to power 40,000 homes and is the largest of its kind in Japan — began operating in Kawasaki this February. It burns construction waste and other woody residue.

Potential: Generators have yet to be installed at 90 percent of Japan's municipal waste incinerators. While the country lacks space for growing specialty biopower crops, 14 million tons of crop residue go unused each year. Millions of hectares of unthinned plantation forests offer another potential fuel source, since small trees must be removed for forest health but have little value as building materials.

How it works: Biopower is generated by burning, gasifying, or fermenting organic matter ranging from trees to garbage. Burning biomass (or mixing it with coal and then burning it) to produce steam and turn a turbine is the most common method used in Japan. By heating biomass under pressure, it can also be turned into gas to use in gas or steam turbines, often after a refining process.

Finally, in a process called anaerobic (oxygen-less) digestion, micro-organisms are used to break down manure, garbage or sewage, producing methane that can be burned in generators. Some large livestock farms use on-site anaerobic digesters to turn the huge amount of manure from their animals into a valuable electricity sou rce (critics point out that the residue can still contaminate the environment). Methane is also produced naturally by decomposition in landfills, and has been used to fuel power plants in the United States since the 1950s.

Analysis: Until recently, burning biomass was widely seen as being more sustainable than burning coal or oil. A number of recent studies, however, have questioned that assumption.

Biopower is considered renewable because the trees, cornstalks or other organic materials that are burned (or gasified) eventually grow back and can be harvested again for fuel. Similarly, while biomass emits carbon dioxide when burned, it is reabsorbed when plants grow back (the same cycle applies to coal and gas, but takes millions of years). The cycle's sustainability, though, requires careful calculations regarding timing and land use.

A 2010 study by the U.S.-based Manomet Center for Conservation Sciences concluded that while burning trees rather than coal in electric-power plants could reduce greenhouse gasses in the long term, carbon dioxide emissions would exceed absorption for the first 30 years of forest re-growth (industry groups criticized the report because it did not consider the use of sawmill debris and other waste).

This February, a report from Japan's Internal Affairs and Communications Ministry found that of 132 government-funded biomass projects, only 2 percent had calculated their greenhouse-gas impact. When the ministry did its own calculations, it found that 20 percent had no positive impact at all (the report was not limited to electricity projects).

Another obstacle to biopower is that while sun and wind arrive free of cost, organic materials must be transported to power plants for use. Drying materials before transport and building small local power plants both help, but costs can still exceed returns from electricity sales.

Unattributed statistics in this article are from the National Institute of Advanced Industrial Science and Technology's Biomass Technology Research Center; the "Renewables Japan Status Report" (2011), published by the Japan Renewable Energy Policy Platform; and Biomass Thermal and Power, a U.S.-based trade publication.
via search.japantimes.co.jp

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