Why do low-voltage data centers use so much power and how to calculate the power consumption?

It is common knowledge that server rooms are known to consume a significant amount of electricity. Currently, the electricity consumption of large data center computer rooms in China is significantly behind that of advanced countries. The electricity distribution in server rooms is as follows: IT accounts for 44%, cooling accounts for over 38% (with some reaching as high as 50%), and the remaining power and lighting account for about 18%. Clearly, cooling electricity consumption is the main factor affecting the PUE value, with cooling systems being the main culprit for energy consumption in server rooms.

Here's the formula for calculating the server room's area:

A (main room area) = F area per rack 3.5～5.5㎡ / rack (using the median value of 4.5) × N total number of network racks

Main room area = 4.5 (㎡/rack) × 30 racks = 135㎡

(1) The power consumption of equipment in the server room is calculated as follows: If 30 network cabinets are planned, each consuming 3KW, the total power consumption will be 3KW * 30 = 90KW.

(2) The power consumption of other equipment in the server room (fire protection, monitoring, emergency lighting) is approximately 8000W. The basic capacity of the Uninterruptible Power Supply (UPS) system can be calculated using the following formula:

E ≥ 1.2P

Where

E - Basic capacity of the UPS system (excluding redundant UPS equipment)

P - Calculated load of electronic information equipment [(KW/KVA)]

P = 1) + 2) = 90KW + 8KW = 98KW

E ≥ 1.2P

E ≥ 1.2 * 98 KW

E ≥ 110.4KVA

Considering that the optimal operating range for UPS is between 60% and 70%, it is recommended to further increase the above calculation result by dividing it by 0.7.

110.4KVA / 0.6 ≈ 184KVA. According to the model manual, select a model close to the power, so a 200KVA UPS is chosen. For the safety and reliability of the power supply, it is recommended to use a 1+1 redundant UPS configuration, so two 200KVA UPS units are needed.

Therefore, in the selection: Choose two 200KVA UPS units for 1+1 parallel operation.

The experience method of "power and area" is used to calculate the cooling load of the server room.

Qt = Q1 + Q2

Where, Qt - Total cooling capacity (KW)

Q1 - Indoor equipment load = UPS power consumption × 0.8

Q2 - Environmental cooling load = 0.12～0.18KW/㎡ × server room area

Therefore, the cooling capacity of the server room is:

Q1 - Indoor equipment load = 200KVA * 0.8 = 160KW

Q2 - Environmental cooling load = 0.15KW/㎡ * 251 ㎡ = 37.5KW

Qt = Q1 + Q2 = 160KW + 37.5KW = 197.5KW

So: The required cooling capacity in the server room is 197.5KW, it is recommended to have a 40% redundancy in cooling capacity. Use a 320KW cooling air conditioner (4 units of 80KW cooling air conditioners)

The actual total power consumption includes the power used by the UPS, air conditioning, lighting, and other equipment.

UPS equipment power consumption: 200KVA = 200KW

Precision Cooling System power consumption: Cooling capacity / 2.5 = 320KW / 2.5 = 128KW

Lighting: P (lighting power per square meter) * S (server room area)

20W * 251 square meters = 5KW Other equipment: 10KW

Actual total power consumption = (200KW) + (128KW) + 5KW + 10KW = 343KW

When constructing the server room, a safety margin of 25% is usually considered, resulting in an actual total power distribution of 450KW

(1) Floor area occupied by workstations, storage, etc. in the server room: 135.5㎡

(2) Floor area occupied by UPS, power distribution, and batteries

For a single UPS system with a delay of 30 minutes, 32 pieces of 12V-200AH batteries are required, and for two systems, 64 pieces are needed.

The total area occupied by the equipment is 28㎡, excluding maintenance space. The maintenance space typically requires an area 2-3 times the size of the equipment footprint. So the floor area occupied by UPS, power distribution, and batteries is about 70㎡.

(3) Floor area occupied by air conditioning

Four air conditioners are selected, each with a floor area of 2.1㎡. Since the air conditioners are fully front-maintained, the actual floor area is about twice the size of the air conditioner itself, which is about 4㎡. Four air conditioners total 16㎡.

(4) Total area of the server room

Floor area occupied by workstations, storage, etc. in the server room: 135㎡ + Floor area occupied by UPS, power distribution, and batteries: 70㎡ + Floor area occupied by air conditioning: 16㎡ = 221㎡

The fire protection area is 30㎡.

The total area of the server room is approximately: 251㎡

To achieve energy saving in power consumption, the first step is to conduct power consumption testing in the server room and accurately grasp the power consumption in the server room. Most mobile base stations are unmanned, but the various electronic devices in these communication rooms need to operate in a certain temperature environment (the national standard GB50174-93 for server room environment stipulates that the annual server room temperature is 18℃～28℃) to run normally for a long time. To achieve the standard environmental temperature in the server room, each communication room is equipped with about two air conditioners, which are in operation all year round, so the power consumption of the server room is a significant part of the consumption.

To accurately measure the power consumption of server room equipment, you can use power measurement devices or management software, such as power meters, UPS systems, or PDUs. For individual equipment, we can connect a three-phase meter ourselves and estimate the power consumption using the formula P = I × V. However, this can only measure the instantaneous power consumption. If the power consumption of the equipment is not a fixed value, it is impossible to count, analyze, or convert it into power consumption (kilowatts × hours). Moreover, the operation and connection method are also more complicated.

It should be noted that the numbers related to the power consumption of the equipment are effective power (watts) and total power consumption (volt-amperes). Usually, the power consumption we refer to, or the indicator used by Taiwan Power for electricity billing, is the effective power. The power consumption statistics (kilowatt-hours) counted by the substation are also calculated using effective power, so they can be directly converted into electricity bills. However, according to the data provided in the instruction manual of this equipment, the error between the statistical results of power consumption and actual electricity bills is about 0.5% to 2%. However, this detection method is only applicable to detecting one piece of equipment at a time and cannot be used with centralized management software for analysis and statistics. Therefore, if you want to know the power consumption of multiple machines at the same time, you still need to use specialized power management equipment for statistics, such as uninterruptible power supply (UPS) or PDU power distributor.

Using power measurement equipment or management software can comprehensively grasp the power consumption situation of server room equipment, and management is also easy, but the one-time cost is high, usually over tens of thousands of yuan, which is more suitable for large server rooms or environments with many devices. The power measurement meter designed for a single product is only a few thousand yuan, and if the number of devices that need to be monitored is small, this type of product can be used, and the value can be recorded manually.