Development of Residential Fuel Cell "Ene-Farm Mini"
Authors: Ando Daiki , Shirai Yoshikazu , Ito Takuya , Yoshida Hideki , Watanabe Takayuki , Itsuki Hisayuki , Ito Kentaro 
Published: December 2020

Tokyo Gas Co., Ltd. has launched residential distributed power generation system “ENE-FARM” which is a micro-CHP system in 2009. The number of cumulative sales reached 300,000 in Japan and 130,000 in Tokyo Gas in FY2019. In order to further spread of “ENE-FARM”, the world's smallest residential fuel cell "ENE-FARM mini" manufactured by Kyocera Corporation was released in October 2019.
“ENE-FARM mini” has been developed with the concept to minimize the system size, optimize the rated power of the system with ensuring the power generation efficiency, add the function of continuous power generation during blackout, utilize the IoT technologies, and reduce the cost for installation work.
To minimize the system size, the SOFC system integrated of the cell stack and the reformer was adopted. The cell stack’s size was reduced by lowering the rated power to 400 W. The lowered power is also suitable to the recent energy demand decreasing by the spread of energy saving house. The system was introduced to minimize the size of the hot water tank to 20 L, much smaller compared to the conventional “ENE-FARM”. As a result, the size of the whole system is minimized to the point of the smallest in the world, as small as the size of the air conditioner outdoor unit. It is expected to meet more demands from the customers who were not able to afford the large space for the installation due to the limited space available in their residences.
In order to lower the rated power to 400 W power with securing the power generation efficiency, it is challenge to secure the heat required for power generation. Hot Box covering the cell stack was designed to achieve high thermal insulation by reducing the heat dissipation loss. As a result, the high power generation efficiency of 47% (LHV) was achieved due to maintain high-temperature conditions.
Moreover, the function of continuous power generation during blackout was introduced to “ENE-FARM mini”. Although the blackout occurs during power generation, it is capable to supply the power to the emergency outlet and the boiler, as long as the city gas lines are operating. Therefore, it is possible for users to operate some of the household appliances through the emergency outlet. The hot water supply system and the floor heating system can be functional if the water lines are operating.
“ENE-FARM mini” was compatible with the IoT system. Many features such as the usage amount of gas, electricity, water and utility costs can be easily checked on the user’s smartphones. The users also can remotely control many systems such as the hot bath and the floor heating system. Additionally, the usability was improved by implementing the smart speaker compatibility.
It is the critical challenge to reduce the cost for installation work. The minimized and weight saved system made it possible to carry the whole assembly with a subcompact car. It only requires two persons to carry and install the system even in a narrow space with a depth of 500 mm. Because the center of gravity point was set to be lower, the base components could be compact and lightweight. The typical weight of the base components was about 27 kg which consists of two components of 13.5 kg. Therefore, the base components can be carried by only one person. It leads to simplify the installation work and reduce the cost for installation.
We will continue to contribute to the comfortable living of customers, the preservation of the global environment, and the enhancement of resilience through the spread of "ENE-FARM".

Figure 1