TECHNOLOGY AND INNOVATION CENTER

――How did you become involved in micro-hydroelectric power generation systems?

Suhara: Since entering the company, I have always been involved in the development of products other than air conditioners. In 2011, the Great East Japan Earthquake occurred, and energy became a concern to society. This prompted me to reassess my contribution to the company and society.   While solar and wind power rely on natural conditions that can be unstable, I turned my attention to hydroelectric power generation, which can provide stable energy regardless of the time or weather.

In fiscal year 2013, we applied for the Ministry of the Environment's “Enhanced Inducement-Type Technology Development and Demonstration Project for Reducing CO2 Emissions.” Our project was selected, marking the development start of micro-hydroelectric power generation systems with an output of less than 100 kW. Over the course of three years in this project, we developed two micro-hydroelectric power generation systems, each with different capacities, and conducted demonstrations in two different regions.

――What challenges did you face in developing micro-hydroelectric power generation systems?

Suhara：First, as a target for micro-hydroelectric power generation systems, we focused on the pipelines in waterworks facilities. These pipelines are internal pipes filled with water, and since the flowing water does not come into contact with air in these pipelines, we could expect significant power generation output based on the pipe pressure and water flow. Unfortunately, with no prior experience in developing low government projects, we lacked knowledge of waterworks and facilities. This became our initial hurdle. We proposed a concept of developing a low-cost, space-saving system while collecting public information from waterworks providers and conducting on-site interviews.

My own responsibility was in control software, whereas the mechanical aspects were handled by members from the Oil Hydraulics Division. Naturally, none of us had experience with turbines, so we began by gaining knowledge of turbine operation along with their energy efficiency and characteristics. We concurrently developed performance testing equipment to investigate these aspects. However, the installation conditions at waterworks facilities varied in terms of flow rate and drop height, and operations also differed subtly. Therefore, we had to consider how to meet these different requirements and accomplish the project, including design, manufacturing, demonstration testing, and equipment removal, within a short three-year period. It was a truly challenging situation at the time.

――What system did you develop specifically?

Suhara: We developed a micro-hydroelectric power generation system designed to maximize the utilization of untapped energy in the pipelines of waterworks facilities. The overall system consists of a highly efficient variable-speed (permanent magnet synchronous) generator, a vertical inline pump reverse turbine, and a power generation controller, among other components. The power generation controller is integrated with the generator to minimize installation space and achieve cost-effective solutions for both deployment and maintenance. Furthermore, we utilized the motor and inverter technology that Daikin had developed over the years in the fields of air conditioning and hydraulic equipment to achieve high efficiency.

In principle, the system operates by harnessing the power of water flow in a pipeline to rotate a turbine. The shaft of the turbine is connected to the generator via a coupling, which converts the rotational energy of the generator into alternating electrical energy. This energy is then transformed into direct current using the power generation controller (converter). Furthermore, it is converted back into alternating current using a grid-connectable inverter within the system control panel, making it usable as a commercial power source.

――What are the key features of Daikin’s micro-hydroelectric power generation system?

Suhara: The biggest feature is its significantly lower cost compared to conventional systems. Substantial cost savings was achieved by using off-the-shelf components for a grid- connectable inverter that connects to the grid and by repurposing pumps to serve as the turbine. Initially, we designed custom runners, but they turned out to be cost-prohibitive, so we opted to use commercially available runners. Traditional turbines were typically custom-made, contributing to the high costs associated with hydroelectric power generation and being one of the reasons the system failed to gain wide acceptance.

The generator and control controller were integrated into a single unit, which was placed on top of the turbine, allowing us to minimize the installation footprint by configuring the system vertically and making it easier to install the system in tight spaces within existing waterworks facilities. We also devised a cooling mechanism to handle the heat generated by the system. Notably, we utilized the water from the waterworks facility itself for the water cooling mechanism.

Furthermore, conventional hydroelectric systems require complex mechanisms to maintain a constant rotation speed of the turbine, and guide vanes are used to adjust the flow rate.  Our micro-hydroelectric power generation system utilizes motor and inverter technology to control flow while varying turbine speed. This allows us to convert previously wasted water energy into electricity and maximize the electrical output. Control software, which incorporates new functions to control flow and pressure, also plays a crucial role. Generator control follows the desired flow rates of the waterworks facility by applying reverse torque during regenerative operation.

For the demonstrations, we developed 22 kW and 75 kW hydroelectric systems and selected waterworks facilities in Minami-Tonami City, Toyama Prefecture, and Soma City, Fukushima Prefecture, as installation sites. Demonstration results confirmed sufficient power generation capacity and performance within the existing waterworks facilities with no disruptions to operations for trouble-free, stable power generation.

――What are your thoughts on the commercialization of the research and development project you worked on.

Suhara：Within Daikin, it has been quite rare for newly developed projects to lead to commercialization. Experiencing the entire process of “Can it truly be profitable, and can it become a viable business?” was extremely valuable to me.

――Looking back, what can you say about the culture and environment of conducting research at TIC?

Suhara: TIC has an environment where skilled professionals from various fields come together. Even when faced with something unknown, I can quickly seek the advice of an expert. My case may be unique in that I've also worked with colleagues outside of TIC, so I feel at ease consulting with people from other departments at TIC. In any case, Daikin has a culture where someone will always lend a helping hand when another colleague is confronting difficulties. I believe that effective communication with various people can make work progress more smoothly.