Japan breaks ground on its largest binary geothermal plant

Overview

Updated Yesterday

In 1998, Kyushu Electric Power drilled a survey well near Mt. Eboshi and confirmed the site held geothermal resources. The plant built on that discovery finally broke ground on October 9, 28 years later.

The 4,990-kilowatt facility is Japan's largest binary-cycle geothermal plant. Binary systems vaporize a low-boiling-point working fluid with geothermal heat, letting them tap cooler resources than conventional steam plants. The Kirishima plant will reinject all steam and hot water underground and supply roughly 32 million kilowatt-hours a year, enough for about 10,600 households.

Kyuden Mirai Energy, a subsidiary of Kyushu Electric Power, is building the plant as its ninth geothermal facility. Commercial operation is targeted for fiscal 2028. The company began the Environmental Impact Assessment for a second binary plant, the 9.5-MW Yutsubo project in Oita Prefecture, earlier this year.

Why it matters

This plant tests whether binary technology can unlock Japan's underused low-temperature geothermal resources at commercial scale.

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Key Indicators

4,990 kW

Installed capacity

Output of the Kirishima Ebishodake binary-cycle geothermal plant.

~32 million kWh

Annual power output

Planned yearly generation, equivalent to ~10,600 households.

~15,000 t-CO2/year

CO2 reduction

Estimated annual emissions avoided versus Kyushu's grid average.

Geothermal plants for Kyuden Group

Kirishima is the ninth; Kyuden Mirai currently operates eight totaling 227 MW.

~22,000 m²

Construction site area

National forest land in Kirishima City's Taguchi area.

Voices

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People Involved

Koji Mine

President and CEO, Kyuden Mirai Energy

Leading the company's geothermal expansion

Shinichi Nakashige

Mayor of Kirishima City

Mayor overseeing the project's local approvals

Kenji Fujimoto

Geothermal Development Department Manager, Kyuden Mirai Energy

Overseeing the Kirishima and Yutsubo projects

Organizations Involved

Kyuden Mirai Energy

Energy utility subsidiary

Project developer and operator of eight existing geothermal plants

The Kyushu Electric Power subsidiary developing the Kirishima Ebishodake binary geothermal plant.

Kyushu Electric Power

Regional electric utility

Parent company; drilled the original 1998 exploration well

The regional utility that confirmed the Mt. Eboshi geothermal resource in 1998 and later transferred geothermal development to its subsidiary.

Timeline

1998 October 2026

4 events Latest: 3 days ago

Tap a bar to jump to that date

October 2026
Groundbreaking ceremony held for Kirishima plant
Latest Construction

About 40 officials and contractors attend the ceremony marking the start of main construction.
3 days ago
October 2024
Site preparation work announced
Construction

Kyuden Mirai Energy announces start of site preparation at the Kirishima location.
October 24th, 2024
April 2022
Kirishima City consents to power station
Regulatory

City delivers consent under its ordinance on geothermal power businesses, a required approval.
April 14th, 2022
1998
Kyushu Electric confirms Mt. Eboshi geothermal resource
Exploration

Drilling of an exploration well near Mt. Eboshi identifies viable geothermal resources.
1998

Scenarios

Kirishima plant starts commercial operation in fiscal 2028

Likely Resolves by Q1 2029

Discussed by: Kyuden Mirai Energy's own projections; FNN and KTS reporting

Construction proceeds on schedule and the 4,990-kW plant begins selling power to the grid in fiscal 2028, matching the company's stated target. This outcome would make it the largest binary-cycle geothermal plant in Japan and a reference case for the technology.

Construction delays push startup past fiscal 2028

Possible Resolves by Q1 2029

Discussed by: Geothermal industry observers noting frequent schedule slips in Japanese projects

The original plan already slipped once, from fiscal 2026 to fiscal 2028. Geothermal construction in Japan frequently encounters drilling and reservoir surprises, and the national forest site adds logistics complexity. A delay would push commercial operation into fiscal 2029 or later.

Project halted or canceled

Unlikely Resolves by End of 2028

Discussed by: No major analysts predict this; a low-probability tail risk

A technical failure in drilling, reservoir underperformance, or an unresolved community dispute halts the project before completion. The city's formal consent and the 28 years of prior work make this outcome unlikely, but geothermal reservoirs can disappoint once production drilling confirms them.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

1966

Matsukawa Geothermal Power Station (1966)

Japan's first commercial geothermal power station began operating at Matsukawa in Iwate Prefecture, built by Japan Metals and Chemical. It proved that Japan's volcanic geology could generate grid-scale electricity from underground heat.

Then

The plant established geothermal as a viable domestic power source in Japan.

Now

Despite an enormous resource base, Japanese geothermal grew slowly; hot spring owners' opposition and complex permitting pushed most development to remote areas. Matsukawa's startup was followed by only a handful of plants over the next 50 years.

Why this matters now

The Kirishima project's 28-year development path reflects the regulatory and social friction that has throttled Japanese geothermal since Matsukawa. The binary plant's approval only came after years of formal consent from a hot-spring town.

July 2012

Japan's 2012 feed-in tariff expansion

After the Fukushima nuclear disaster, Japan introduced a national feed-in tariff for renewable energy that included geothermal. The guaranteed pricing made small and mid-sized geothermal projects financially viable for the first time.

Then

Developers including Kyushu Electric Power began advancing geothermal projects that had been uneconomic under earlier pricing.

Now

The tariff created the economic conditions for binary-cycle plants, which have lower output than conventional steam plants but can use cooler, more accessible resources.

Why this matters now

The feed-in tariff is the policy backdrop that made the Kirishima binary plant economic. Without it, a 4,990-kW facility generating only 32 million kWh a year would struggle to justify a 28-year development effort.