IHI Corporation announced that it has developed a system that efficiently and economically converts all previously discarded surplus direct current (DC) power　at solar power plants into carbon-free steam. IHI together with Soma City launched pilot operations for this system known as the Renewable Energy Thermal Utilization System in April this year at the Soma City Sewage Disposal Plant in Fukushima Prefecture. Work thus far has demonstrated stable system performance.

Solar power generation is susceptible to producing surplus electricity due to the variability of solar radiation throughout the day. Harnessing the potential to produce surplus electricity without wasting any is a vital step towards achieving a carbon-neutral society. IHI was inspired to develop this system that economically and flexibly converts renewable electricity into thermal energy (P2H: Power to Heat).

Renewable Energy Thermal Utilization System Benefits
1. Producing low-cost, carbon-free energy : A low-cost thermal-storage electric boiler converts surplus DC power from a solar power plant into carbon-free steam, storing it for later use.

2. Efficient energy conversion: The system captures DC power that exceeds power conditioners rated capacity (see note 1), which would otherwise be discarded (i.e. power generation loss), storing it in the form of heat for later use.


Test Overview
The Soma City Sewage Disposal Plant consumes up to 240 kilowatts of alternating current (AC) electricity every year. IHI installed a 300-kilowatt solar power plant and a 200-kilowatt power conditioner at the site to generate up to 200 kilowatts of AC electricity. It additionally installed seven JOKIGEN (see note 2) thermal- storage electric boilers from manufacturer IHI Inspection & Instrumentation Co., Ltd., to create a Renewable Energy Thermal Utilization System that absorbs up to 189 kilowatts (27 per unit) of DC power (see Figure 1).

Since the demonstration operations began in April, it has been confirmed that the Renewable Energy Thermal Utilization System can efficiently use all generated electricity and operate stably. In June, the plant consumed 23,160 kilowatt-hours of AC power and 11,860 kilowatt-hours of DC power. Figure 2 illustrates an example of daily electricity usage data for June 29, indicating that system consumption sometimes exceeded 200 kilowatts which is the capacity of power conditioner, peaking at 250 kilowatts.

IHI expects to see market expansion for on-site Renewable Energy Thermal Utilization Systems like the one in Soma City. This system is anticipated to address the issue of surplus electricity and help increase the adoption of renewable energy.

IHI has undertaken various initiatives to foster the local production and consumption of renewable energy to help decarbonize the economy. The company aims to commercialize this Renewable Energy Thermal Utilization System and increase its contributions to customers who require both electricity and heat.

Notes
1. A power conditioner is essential to convert DC electricity (which solar power plants generate) into AC electricity for power distribution and consumption.
2. The JOKIGEN thermal-storage electric boiler from IHI Group subsidiary IHI Inspection & Instrumentation employs inexpensive AC power to store heat and supply it during peak demand. IHI modified it slightly to operate with both DC and AC power for this Renewable Energy Thermal Utilization System.
Product information (in Japanese only): https://www.iic-hq.co.jp/library/035/pdf/035_13.pdf

IHI is conducting this trial with a subsidy from the Fukushima Prefecture Renewable Energy Commercialization Demonstration Research Support Program.

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