WSHPDR_2013_Final_Report-updated_version

3.2.2 Japan
Motoyuki Inoue, Ritsumeikan University and Tokyo
Metropolitan University, Japan
Key facts
Population 127,368,088 1
Area 377,737 km 2
Climate Changes from tropical in the south
to cool temperate in the north 1
Topography
Rain pattern
Approximately 70 per cent of the
land is mountainous, and dividing
mountain ranges cut across the land
like a backbone. This produces
steep-gradient rivers with plentiful
flow volumes that stream from the
mountains into the sea through
alluvial fans and l plains.
Japan lies in the Asian monsoon
region and has ample precipitation.
Electrical sector overview
Japan’s energy self-sufficiency ratio is merely four per
cent, making hydropower generation a valuable,
purely domestic electricity source. In 2011,
hydropower accounted for 35 per cent of Japan’s
domestically produced energy. In proportion to the
total electric power generation, hydropower accounts
for under 10 per cent (figure 1).
Renewable energy
Hydro
Nuclear
Thermal
0.30%
8.70%
11.90%
79.10%
0% 20% 40% 60% 80% 100%
Figure 1 Electricity generation in Japan
Source: Energy White Paper 2012 2
Many existing hydropower plants are ageing and the
number of these has increased, deterioration is
accelerating and many facilities are in need of being
modernized.
According to a 2012 survey by the Agency for Natural
Resources and Energy, there were 2,708 technically
untapped hydropower sites with a total potential
power output of approximately 12 GW and potential
annual electricity production of approximately 45.8
GWh. 3 These values which concerned untapped
hydropower were based on the result of the fifth
hydropower research conducted by Ministry of
Economy, Trade and Industry in 1980. Approximately
98.6 percent of untapped hydropower sites have
power outputs of less than 30 MW and an average
output of around 4.5 MW. There is a sharp decrease in
the number of untapped sites with power output of
less than 1 MW, as many are located in remote areas
and suffer unfavourable conditions, such as relatively
high construction cost. However, since the survey
excludes mountain streams and small rivers,
presumed economically inefficient, it is possible that
many small-scale sites are not covered by the survey.
Japan enjoys a large gross theoretical hydropower
potential (718 TWh) as it has high rate of precipitation
and mountainous terrain. However, Japan’s
proportion of technically exploitable capability to
gross theoretical capability stands at a value of 19 per
cent.
Small hydropower sector overview and potential
There is no official definition of small hydropower
according to installed capacity in Japan. Following the
small hydropower definition of below 10 MW, there
were 1,369 operational small hydropower plants in
2012 (total installed capacity 3,518 MW, annual
generation 18,802 GWh). 3 And there are 2,476
untapped hydro sites with a total power output of
approximately 6,749 MW (figure 2) and annual
electricity production of approximately 27,449 GWh. 3
SHP installed capacity
SHP potential
3 518 MW
10 267 MW
0 2000 4000 6000 8000 10000 12000
Figure 2 Small hydropower capacities in Japan
Source: Agency for Natural Resources and Energy,
Ministry of Economy, Trade and Industry 3
In addition to the above, surveys on the untapped
heads of small hydropower are recently being tried by
various organizations. For example, according to the
results of a survey by the New Energy Foundation
(March 2009) on the untapped heads arising from
using existing structures such as dams, conduit, etc.,
which were not covered in the surveys described
above, analyzed that there were 1,389 sites of power
generation using untapped heads, with a combined
power output of approximately 330 MW and annual
electricity production of approximately 1.7 GWh. 4
Japan’s agricultural waterways have a total length of
approximately 400,000 km, and their gross theoretical
potential is estimated at 5.7 TWh. 5 The technically
exploitable capability of irrigation channels will
improve further with the use of power generation
through run-of-river units.
In recent years, small-scale hydropower development
has been conducted by various operating bodies other
than electricity utilities, such as municipalities, public
corporations for land improvement, private
enterprises, specified non-profit corporations and
individuals. Following the establishment of various
programmes promoting small-scale hydropower,
efforts to introduce small-scale hydropower using
various untapped water heads in existing
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