Discussion on cross-border cooperation led by IDC waste heat recovery innovative technology practice

1 background

In 2020, the country officially announced the dual-carbon strategic goal: "Strive to reach the peak of carbon dioxide emissions by 2030, and strive to achieve carbon neutrality by 2060." As a large consumer of electricity, the power consumption of data centers has exceeded the total power consumption of the country. It is estimated that the total power consumption will reach 4.05% in 2025. However, with the development of information technology, society’s requirements for computing power are getting higher and higher, and the limit of computing power that can be provided by the unit power of IT facilities is gradually approaching. This means that if you want to produce more computing power, you can only have more computing power. Supply energy. For the data center, this is tantamount to dancing with fetters, which not only provides a lot of computing power but also conforms to the national dual-carbon strategy.

With the introduction of a large number of relevant policies to regulate the energy use of data centers, major factories and related upstream and downstream enterprises are looking for various energy-saving and emission-reducing solutions, and waste heat recovery technology is one of them.

2 What is waste heat recovery

Waste heat recovery refers to the technology that recovers the sensible heat and latent heat that have not been rationally used in the original design in the energy-consuming devices of industrial enterprises that have been put into operation due to the limitations of historical, technological, and conceptual factors.

The essence of server computing is the transmission of power to the device, which produces computing power and heat. As a large power user, data centers generate a lot of waste heat in their calculations. How to recycle this waste heat is a relatively important issue.

The HVAC system is the most power-consuming part of the electromechanical system in the data center. The return water temperature of the cooling water loop is only 38-40 degrees Celsius, and the heat recovery conditions are poor. In recent years, due to the gradual tightening of PUE requirements for newly-built data centers by policies, the industry has gradually formed a consensus that the energy consumption of IT equipment will become higher and higher in the future, and the heat dissipation capacity of air-cooled systems cannot support high-density computing power infrastructure requirements , Immersion liquid cooling will become the mainstream solution for high-density computing. Due to the high heat dissipation efficiency of the liquid, the temperature of the liquid cooling loop can be set relatively high, and the return water temperature on the primary side (cooling water side) can even reach 40-50 degrees Celsius. Therefore, with the wide spread of immersion liquid cooling, the environment for waste heat recovery will be more friendly.

3 IDC waste heat recovery practice

This article will use OPPO Cloud Intelligent Computing Center as a reference to analyze the energy-saving and emission-reduction capabilities of the waste heat recovery program from various aspects. After reaching a conclusion, this technology will diverge and explore the possibility of cross-border cooperation with other industries. First of all, the water temperature after heat recovery in the data center is approximately 40 degrees Celsius. After the secondary heating by the water source heat pump or the boiler, it can be used for the domestic hot water supply in the large bathhouse or the domestic hot water supply in the large park.

In order to select the most suitable OPPO cloud intelligent computing center technology, three solutions are listed below for reference and comparison:

3.1 Benchmark plan, gas boiler plan

Directly use atmospheric gas boilers to heat municipal water. Taking domestic hot water as an example, the heating temperature rises to 30-40 degrees Celsius, which is a common mode of traditional public buildings, and there is no energy-saving technology such as heat recovery. Energy costs are affected by local gas prices, gas calorific value and weather. The technology is relatively mature and is currently used on a large scale in the existing construction field. According to calculations, the cost of producing one ton of domestic hot water is about 15.91 yuan.

3.2 Scheme 1 Water source heat pump scheme

The cooling water of the submerged liquid-cooled cluster can be heated to 41 degrees Celsius after the heat exchange with the fluorinated liquid, and the high-temperature cooling water is connected to the water source heat pump as the heat source for heat pump transportation. After passing through the water source heat pump, the municipal water can be heated by 30 to 40 degrees Celsius. This heat recovery scheme is a heat recovery technology that has been commonly used in recent years. Since the total heat transported is the same as the boiler scheme, it is not strictly heat recovery. According to estimates, the cost of the water source heat pump scheme to produce 1 ton of domestic hot water is about 6.88 yuan.

3.3 Scheme Two board exchange + water source heat pump scheme (applicable to air-cooled and liquid-cooled composite data centers)

First, the higher temperature and high level liquid-cooled cooling water preheats the municipal water at room temperature through plate exchange, and raises it to the highest possible temperature (40 degrees Celsius). The pre-heated municipal water (40 degrees Celsius) flows through the water source heat pump. Secondary heating to meet the temperature requirement of domestic hot water at 55 degrees Celsius. The evaporating side of the water source heat pump is connected to the cooling water loop of the air cooling system, and the cooling water of lower temperature and low level is used as the heat absorption medium. The close evaporating side and condensing side temperature can improve the energy efficiency of the water source heat pump and further save energy. This solution is more suitable for large-scale data centers with both air-cooled and liquid-cooled layouts. Both types of waste heat can be fully utilized. However, the system has not been used on a large scale and is a new technological innovation. According to economic calculation, the cost of producing 1 ton of domestic hot water is about 2.95 yuan.

Program Summary

According to simple economic calculations, the energy cost of the new heat recovery technology of Option 2 is only 40-50% of that of the water source heat pump heat recovery solution of Option 1, and only 10%-20% of the energy cost of the traditional boiler solution (without heat recovery).

In actual use, due to different business requirements, the industry tends to use traditional air cooling for storage and other low-density and low-intensity server areas, and use immersion liquid for high-intensity and high-density business server areas such as GPU AI training. Cool down. At the same time, most companies are in the exploratory stage of immersed liquid cooling, and tend to reserve a small part of the space in the data center for pilots of immersed liquid cooling. Therefore, many data centers are air-cooled and liquid-cooled composite projects.

Compared with other solutions, the new heat recovery solution of Option 2 has the following advantages:

1. The heat recovery of the air-cooled and liquid-cooled cooling water loop is fully carried out, so that the two systems are integrated. The liquid-cooled waste heat is used for municipal water preheating, and the air-cooled waste heat is used for water source heat pump water supply.
2. Significantly save the power consumption of the waste heat recovery system, save 60% of energy costs compared with traditional water source heat pump heat recovery solutions, and save 80% of energy costs compared with traditional gas boiler systems (refer to the calculation table).
3. The electromechanical area added by the renovation project is very small, and the existing water-cooling system pipes/cooling towers/water pumps can be directly used for renovation. The amount of engineering is small, the renovation cost is lower, and the renovation resistance is small.
4. Increase the bypass to achieve free heating in summer.

According to the actual situation, the provision of 5 conventional 30-story apartments/talent rooms is tentatively provided. The following table is a simple economic calculation based on the OPPO Cloud Intelligent Computing Center. It can be seen that Option 2 has huge energy-saving advantages and a short payback period.

4 Cross-border cooperation

4.1 Thermal power plant cooperation:

Thermal power plants and data centers are both major carbon emitters. At the same time, power plants and data centers also play a complementary role. On the one hand, power plants can provide data centers with affordable and reliable energy; on the other hand, the waste heat of data centers can be used as flue gas heat from thermal power plants. The recycled preheating makes the high and low waste heat use more efficient. Selecting the location of the data center next to the thermal power plant will have the following advantages:

1. Close to the power source, single line reliability is high.
2. Thermal power plants have a large amount of high-temperature and high-level waste heat that can be used. After the data center preheats the municipal water at room temperature, it can be transported to the thermal power plant to use its flue gas waste heat to further increase the temperature of the water supply. The available range of heat recovery is wider.
3. The cost of direct power supply from power plants is lower than that of grid power supply.

risk:

1. Policy and business are difficult to satisfy, and the power grid is still strong at this stage.
2. Another incoming line is connected to the network to ensure high availability of the data center.
3. The power plant itself is also a risk point.

In general, the cooperation with thermal power plants is a long-term process throughout the life cycle. Starting from the location of the data center, it not only requires the cooperation between the power plant and the data center, but also relates to the government's municipal planning, so this cooperation It is advisable to push forward slowly for a win-win cooperation.

4.2 "Big Bathhouse" Cooperation

"Big bathhouse" is only a synonym, and all facilities that require heat sources for heating are potential beneficiaries of heat recovery. According to preliminary calculations, only the small pilot heat recovery of the liquid-cooled cluster in Building A of the OPPO Cloud Intelligent Computing Center can serve at least five 30-story talent apartments. If the liquid-cooled cluster is deployed, the economic benefits that can be generated are huge.

1. For example, domestic hot water supply in restaurants, apartments or talent rooms in the OPPO park.
2. Pre-heated water supply for municipal heating in the north/park heating supply.
3. Preheating of high-temperature hot water for absorption air conditioners.

4.3 Open source and reduce expenditure in the carbon trading market

Through heat recovery, the amount of combustion gas for heating or domestic hot water is saved, and carbon emissions are also reduced to a certain extent. In a mature trading market, the total carbon emissions of this data center can be reduced. If the carbon emissions indicators are sufficient, the excess carbon emissions can even be reinvested in the carbon trading market to obtain additional income.

5 Conclusion

1. According to economic calculations, waste heat recovery technology can produce more economic benefits. In the future, the data center may even become a regional energy station part-time.
2. In the past, data centers were large consumers of electricity and produced more low-level waste heat. Now the liquid-cooled cluster will be rolled out, and the external environment for waste heat recovery will become better.
3. The current waste heat recovery technology basically replicates the experience of past public construction, and has not made customized technological innovations for data centers, especially for composite IDCs that have been deployed for air-cooled and liquid-cooled.
4. The low-level waste heat of the data center can be used to preheat the waste heat recovery in multiple scenarios, and there is imaginative space for cross-border cooperation with other industries.

Disclaimer: The data calculations and information in this article are derived from past experience data and Internet searches, and are only for learning and exchange. It is not recommended to directly transport without reviewing calculations as a basis for decision-making. At the same time, if the content of this article involves infringement, please contact to delete it.

Author profile

Alan OPPO IDC Engineer LEED AP BD+C

Mainly engaged in IDC infrastructure technology and innovation work

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