ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers), a leader in promoting carbon neutrality, has awarded the Obihiro Kosei Hospital the prestigious Overall Engineering Award of Excellence in its 2024 Technology Award program.
It is the first Japanese medical facility to receive this award.
ASHRAE, founded in 1894, is an international association of heating, air-conditioning, and refrigeration professionals with over 50,000 members. Its standards set the basis for design and operating standards worldwide.
Today, gas is the primary fuel for heating in the U.S. and Europe, but the shift from gas to electric heating using heat pumps is promoted to achieve carbon neutrality.
One can assume that the ASHRAE recognized the Obihiro Kosei Hospital's system for successfully reducing gas consumption and CO2 emissions.
This column will focus on this gas fuel reduction initiative and the process leading up to it.
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Many rooms and equipment in a medical facility need cooling, and the cooling system dissipates a large amount of waste heat into the atmosphere.
On the other hand, it requires a significant amount of heat for domestic hot water heating and heating system. In cold regions such as Obihiro, heat has typically been obtained using boilers and other equipment that burns gas or oil.
Top of the left figure
At the Obihiro Kosei Hospital, waste heat was considered a heating source. We used a heat recovery chiller HRC to collect heat for domestic hot water supply and heating system, reducing the need for boilers and other gas combustion.
Bottom of the left figure
This facility was the first to use all waste heat from cooling systems in Japan, where all cooling waste heat from medical equipment, refrigerators, server rooms, and electrical rooms is thoroughly utilized.
Warm indoor air is also exhausted outside and is used as a heating source to heat the incoming outdoor air.
Exhaust heat is utilized either by incorporating a sensible heat exchanger, which exchanges heat between exhaust air (returned air) from the room and outdoor air, into the air-handling units in proportion to the airflow volume, or by using a combination of multiple air-handling units with a single sensible heat exchanger. Right figure
It is an ingenious combination of existing general-purpose products, which anyone in the world can do.
This system, which "anyone in the world can do," is critical to promoting carbon neutrality for the entire planet.
The problem with operating a heat recovery chiller is that the temperature of only either the chilled water or the waste hot water supply can be fixed. Even if the chilled water supply temperature is fixed at 8 °C, the waste hot water temperature varies according to the cooling demand. Top of the right figure
In severely cold regions, unstable temperatures for water heating can cause problems. Therefore, we avoided directly connecting the waste hot water piping from the heat recovery chiller to the hot water system for heating. Instead, we indirectly connected the exhaust hot water piping from the heat pumps via a heat exchanger. Left figure
The system uses the waste hot water heat to heat the return hot water for the heating system, and the boiler heats the water when the temperature after heating is not high enough for the heating system, thereby stabilizing the boiler outlet temperature or the hot water temperature for the heating system. Bottom of the right figure
This ingenuity was assumed to be another critical point that earned recognition, for it is a "technology that anyone in the world can do."
The problem with operating a heat recovery chiller is that the temperature of only either the chilled water or the waste hot water supply can be fixed. Even if the chilled water supply temperature is fixed at 8 °C, the waste hot water temperature varies according to the cooling demand. Left of the lower figure
In severely cold regions, unstable temperatures for water heating can cause problems. Therefore, we avoided directly connecting the waste hot water piping from the heat recovery chiller to the hot water system for heating. Instead, we indirectly connected the exhaust hot water piping from the heat pumps via a heat exchanger. Upper figure
The system uses the waste hot water heat to heat the return hot water for the heating system, and the boiler heats the water when the temperature after heating is not high enough for the heating system, thereby stabilizing the boiler outlet temperature or the hot water temperature for the heating system. Right of the lower figure
This ingenuity was assumed to be another critical point that earned recognition, for it is a "technology that anyone in the world can do."
This ASHRAE World's Best Award was not the result of the author's efforts alone. Also, this "system for recovering cooling waste heat into hot water" did not achieve the prescribed performance from the outset.
Academics and energy service providers verified the operation in 2019 when the project started. Thanks to much advice and precise fine-tuning, the waste heat recovery rate for winter 2020 reached almost 100%. Right figure
Operational improvements have increased the percentage of hot water supply for the heating system from heat recovery chiller from 33% in 2019 to 58% in 2020 and preheating for domestic hot water rom 17% in 2019 to 23%. Left figure All these efforts have reaped great blessings.
This ASHRAE World's Best Award was not the result of the author's efforts alone. Also, this "system for recovering cooling waste heat into hot water" did not achieve the prescribed performance from the outset.
Academics and energy service providers verified the operation in 2019 when the project started. Thanks to much advice and precise fine-tuning, the waste heat recovery rate for winter 2020 reached almost 100%. Lower figure
Operational improvements have increased the percentage of hot water supply for the heating system from heat recovery chiller from 33% in 2019 to 58% in 2020 and preheating for domestic hot water rom 17% in 2019 to 23%. Upper figure All these efforts have reaped great blessings.
The graph below vividly illustrates that the priority base operation of the heat recovery chiller year-round efficiently provides cold and hot heat. Other heat sources supplement them when there is a shortage. This method is in keeping with the design intent of "recovering heat and reducing gas combustion." This is the result of the aforementioned fine-tuning.
As a result, gas consumption for heating and hot water supply was reduced by approximately 450,000 Nm³ annually, and CO2 emissions by approximately 800 t-CO2, which are significant rates.
The combined CO2 emissions of electricity and gas were around 0.100 -CO2/m², lower than the 0.120 t-CO2/m² emissions indicated in the data for large hospitals in Japan.
From April to October, heat recovery chiller provides more than 90% of the thermal heat for heating.
From November to March, when the average daily minimum outdoor air temperature is below 0℃, boilers and other equipment are operated along with the heat recovery chiller.
In regions with warmer climates, a heat recovery system utilizing the exhaust heat from the cooling system can supply the majority of the heat for heating and hot water preheating with little use of other heat source equipment. This method potentially contributes to achieving carbon neutrality in countries around the world.
At the ASHRAE Winter Conference in 2023, the author witnessed many people from the United States and the United Kingdom seriously discussing how to stop using gas and other fossil fuels for heating systems and domestic hot water heating systems and promote electric heating.
Upon seeing this, the author realized that our successful experience in Obihiro could be helpful, as what they were trying to promote must align with what we accomplished there. The thought motivated the author to apply for ASHRAE's technical award program.
To promote carbon neutrality in the field of building equipment, we need to stop making heat while discarding heat and minimize gas combustion. And using technology that "anyone in the world can do" is critical to achieving the goal.
Substantial waste heat exists in the world that is unused and discarded.
We hope this award will promote the use of heat recovery systems and contribute to reducing CO2 emissions.
