Battery requirements for energy storage in data centers in the new energy era

According to research by ICT Research Consulting, the number of data centers in China is about 56,000 in 2016, with a total area of about 16.5 million square meters. It is estimated that by 2020, the number of data centers in China will exceed 80,000, and the total area will exceed 30 million square meters.

Correspondingly, energy consumption is rising year by year. According to data from the China Data Center Energy Conservation Technical Committee, the total power consumption of China's data centers exceeded 110.8 billion kWh in 2016 and reached 12-130 billion kWh in 2017. This figure exceeds the annual power generation of the Three Gorges Dam in 2017 (97.605 billion). The sum of kilowatt hours and the power generated by Gezhouba Power Plant (the power generation of Gezhouba Power Plant in 2017 was 19.05 billion kWh).

According to statistics, electricity expenditure accounts for more than 60% of data center operating expenses, so how to reduce data center electricity expenses? This paper discusses the business model of energy storage data center.

The author believes that the development of electrochemical energy storage technology can gradually subvert the traditional data center's power management model, and will also subvert the traditional investment model in this field. This kind of subversion is a favorable subversion.

In recent years, the development of energy storage, especially electrochemical energy storage, has been in full swing and is in full swing. However, behind the excitement, there are many sighs and "there are thousands of sails that are not exhausted helpless.

The author has always believed that under the existing power system, it is difficult to continue to stabilize profits by simply relying on the peak-valley spread to make a fuss. The development of the energy storage industry is inseparable from a reasonable payment mechanism or a combination of specific application scenarios, to find a specific value point and income point, in order to develop.

Many industry colleagues have asked the author, before the reasonable payment mechanism has been formed, what are the specific application scenarios?

This article tries to use the data center to develop energy storage to create a rich profit model and business model as the entry point, and to discuss with everyone.

The status quo and problems of data center development

The data center consists of a computer system and its associated equipment, as well as redundant data communication connections, environmental control, monitoring and various security devices. It is the center of data transmission, computing and storage. Along with the explosive development of China's mobile communications, big data, cloud computing, network payment, artificial intelligence and other services, and the accelerated penetration of "Internet +" into the industrial field, the rapid growth of Internet data transmission, computing and storage needs has been promoted. This in turn stimulates the need for infrastructure such as data centers.

According to research data, in 2010-2016, China's IDC (Internet Data Center) market grew by nearly 7 times, with an average annual growth rate of 39.19%. After 2017, the market size of China's data centers continued to grow rapidly, with an expected 2019. In the year, the market size of China's data centers will exceed 180 billion Yuan, of which about 70% will be new data centers.

The data center obtains revenue by providing customers with services such as cabinet rental, bandwidth lease, and server proxy operation and maintenance. For the data center, ensuring safe and reliable power and network supply is the most basic two functions of the data center, so the data center is equipped with an uninterruptible power supply (UPS). The uninterruptible power supply consists of two parts: the UPS main unit and the battery. When the mains supply is normal, the UPS supplies power to the load after “filtering the mains impurities” and charges the battery. When the mains supply is abnormal (interruption of power supply), the battery is discharged. The power supply is guaranteed by the UPS supply load. This traditional data center power backup mode has the following application pain points:

1. High electricity bills. After the data center is completed, its main operating costs come from electricity bills. Statistics show that electricity bills account for more than 60% of data center operating expenses. Take the medium-sized data center with 2,000 cabinets in Jiangsu as an example. If the average power of the cabinet is 5 kW, the power consumption of the cabinet for only one year is 2000*5kW*24h*365 days=87.6 million kWh, the average of Jiangsu Province. The electricity price is about 0.68 Yuan, and the electricity bill generated by only one cabinet is as high as 59.57 million Yuan. The power consumption of other power equipment such as air conditioners, UPS power supplies, and lighting has not been counted here. Therefore, how to reduce data center electricity expenses is crucial to improve the profitability of data center enterprises.

2. High battery investment. Moreover, the battery does not discharge during the use period, which wastes resources and is a sunk cost. China produces more than 200GWh of lead-acid batteries every year, and a large proportion of them are used in the data center for backup. The life of these batteries is usually about 5 years. To ensure the safety of standby power, it is necessary to replace one batch every five years. At present, the power supply reliability of most regions in China is over 99.9%, and since the data center usually adopts dual-channel power supply guarantee + 2N mutual backup structure, the battery rarely has a chance to discharge, and is in a long-term idle state, resulting in a large resource waste.

3. The battery is in a floating state for a long time, and the state of health is unknown. As mentioned above, due to the high reliability of data center power supply, the battery has been in a floating state, and it is not charged once a year. Some data centers even need to pass regular dummy load tests to verify the performance of the battery. Expenses are also quite expensive.

Understanding the pain points of data center operations and UPS power usage helps us understand how to solve existing problems. Thanks to the development of energy storage technology in recent years, the construction of energy storage data centers has become an important means to solve the above application pain points.

Data center energy storage requirements for batteries and UPS hosts

There is a dynamic balance between grid power generation and user electricity consumption. In order to improve unit utilization rate during power consumption, reduce power generation costs, and increase efficiency and reduce emissions, China began to implement peak and valley electricity price system in 1993. The design of this system original intention is to use economic means to guide the society to use peak electricity. The existence of peak and valley price gaps provides arbitrage space for energy storage through “low storage and high incidence”. However, due to energy storage cost constraints, it is difficult to obtain sustainable profitability for simple peak-filling and valley filling projects. The construction of the data center itself requires a large amount of battery and UPS host investment, which provides the necessary conditions for peak and valley arbitrage, but needs to solve the battery cycle life and the function of the energy storage type UPS host.

1. Data center energy storage requirements for batteries

The traditional ordinary lead-acid battery cannot meet the requirements of the user's peak-filling mode to the long cycle life of the battery. It is imperative to develop a new type of circulating battery. Thanks to the incentives and guidance of the Obama Clean Energy Program in 2006, a global research boom in lead-carbon batteries has been launched and products have been launched. The so-called lead-carbon battery, on the basis of not changing the electrochemical system of the lead-acid battery, through the addition of carbon by the negative electrode and the life extension technology of the positive electrode and the electrolyte, the cycle performance of the lead-acid battery is greatly improved, and the cycle life is ordinary lead 3-5 times the acid battery. The solution to the problem of battery cycle performance has created a prerequisite for the construction of energy storage data centers.

In the data center energy storage application, in addition to peaking and filling the battery, the battery must also ensure the power backup time. Therefore, the battery discharge depth is generally controlled at about 50%, and about 50% of the remaining power is used to ensure the backup time. As we all know, the deeper the battery discharge depth, the shorter the cycle life, the depth of discharge of about 50%, just to meet the requirements of the data center for the battery life (10 years), but also to ensure a better peak clipping Benefits, performance and requirements fit perfectly.

2. UPS energy storage requirements for UPS host

The amount of electricity that can be discharged by the electrochemical power source is affected by the discharge rate. The smaller the discharge rate, the more electricity can be discharged, and vice versa. For example, for a lead-acid or lead-carbon battery, if discharged at a rate of 0.1 C (A), it can be discharged for 10 hours, and the total capacity discharged is 1 C (AH); but if it is discharged at 1.5 C, it can only be discharged for about 15 minutes. The total discharge capacity is 0.375C (AH), and large rate discharge will seriously affect battery life. In the case of peak clipping and valley filling, the larger the discharge amount, the more profit, because the peak price electricity time, that is, the discharge time (usually 8 hours) is long enough, so it is possible to select a small rate discharge method that meets the discharge characteristics of the lead-acid battery. To run, this requires the UPS host to have the function of powering the mains and battery.

In the conventional data center, because the reliability of the power supply is very good, the battery is rarely discharged, and even if there is occasional discharge, the charging time is long, so the power can be replenished in time. According to the distribution of current peak and valley periods in China, the price of electricity in the valley is generally only 8 hours. In order to ensure the recharge of the battery after discharge, the UPS host must have a charging capacity of 40% or more.

Through the communication with the mainstream UPS host manufacturers, technically solve the above problems, there is no obstacle at all, and the added cost is very limited, which removes technical obstacles for building energy storage data centers.

The page contains the contents of the machine translation.