Drives motors A guide to using variable-speed drives motors in data centres
The power behind the data Private public businesses, from banks to supermarkets, to telecommunications companies internet providers depend on data centres for gathering, storing managing vast volumes of data in a reliable, efficient secure way, powering everything from online shopping transactions through to storage retrieval of hospital records. Any form of data loss can have a disastrous impact on the business. As such, data centres suffer high operating maintenance costs. Not surprisingly, they require massive amounts of power to keep them running smoothly efficiently. The everincreasing dem for computing power has a significant impact: with the new technologies, between 20-22 kw of power is required for each single rack, compared to 4-5 kw normally needed in the past. In the future, these environments will become one of the main consumers of power in the world. With the continued growth of the internet electronic banking, the need to deliver data storage solutions that also help improve energy efficiency the levels of power used within such a centre has never been greater. All of which affects plant costs: the electrical mechanical aspects of a new office building are usually equal to 15 percent of the investment, but with a data centre this value increases to 70 percent. Cutting the power overhead It is estimated that IT applications, including data centres, consume 2 percent of all electrical energy produced. The EU estimates that the power consumption of data centres is set to rise to 93 TWh by 2020. Most of this power consumption is represented by the IT load, accounting for 40 percent, while the cooling system runs a close second at 35 percent, with the UPS lighting accounting for a further 25 percent. Power Usage Effectiveness, or PUE, is the most commonly used method of determining the energy efficiency of a data centre. This ratio is the total power entering the data centre divided by the power used by the IT equipment. PUE = Total facility power IT equipment power The average data centre has a PUE of 2.0. This means that the facility uses one watt of overhead power for every watt delivered to IT equipment. Improving this ratio means reducing overhead power use, mainly by cutting the percentage of power used by the cooling system. This can most readily be achieved by using variable-speed control to reduce the speed of motors driving pumps fans. 2 The power behind the data l A guide to using variable-speed drives motors in data centres
Because many pump fan systems run at less than full capacity for much of the time, VSDs can produce huge savings. If a 100 kw fan is throttled by 20 percent, for example, the investment in a VSD will have a payback of typically six months based on continuous operation. Benefits of variable-speed drives Commercial Reduced energy consumption from 20 to 50 percent Fast payback from six months Reduced CO 2 emissions CRC Energy Efficiency Scheme (CRC) UK Government s matory initiative to reduce carbon dioxide (CO2) emissions from organisations meeting certain qualification criteria. Enhanced Capital Allowances UK Government s programme of tax relief for companies investing in equipment that meets energy saving criteria Variable-speed drives Data centre running costs can be significantly reduced from 20 to 70 percent with VSDs. These devices control the flow of pumps air conditioning fans to eliminate the energy waste that is common with conventional pump fan control methods. Typical savings Typical data centre may have approx. 70 fixed speed motor applications Average power per motor is 7.5 kw Typical motor power could be > 0.5 MW Typical running costs could be > 450 k per annum Typical financial savings could be > 20 percent i.e 90 k per annum Payback < 2 years How variable-speed drives work Many existing pump fan systems are based on throttling arrangements: the motor is driven at full speed then the flow of liquid or air is regulated by dampers, valves, vanes or similar throttling mechanisms. Throttling the output in this way, wastes energy. A VSD can increase the system s efficiency by adjusting the motor speed to the correct operation point eliminating the need for throttling. A small reduction in speed can make a big difference in energy consumption. A centrifugal pump or fan running at 80 percent speed consumes only half as much energy as a unit running at full speed. This is because the power required to run a pump or fan changes with the cube of the speed. Technical Lower maintenance costs Starting, stopping braking can easily be programmed to reduce stress on mechanical equipment Increases equipment life reduces maintenance requirements for pumps, motors pipework Easily retrofitted into an installation Real time clock Can easily set up programmes with different running speeds at different times or on different days Low harmonic solutions available as part of installation design Financial controller Significantly reduced energy bills Rapid return on investment Qualify for Enhanced Capital Allowances Lower maintenance costs Substantial contribution to environment by lower CO 2 emissions Facilities manager Gain control of air conditioning costs Easily retrofit VSD to installation Maintenance engineer Reduced maintenance on pumps fans, hence lower costs Adjusting speed according to dem saves wear tear on pumps, fans motors The power behind the data l A guide to using variable-speed drives motors in data centres 3
Data centre applications for variable-speed drives Challenges facing air conditioning As the servers are always operating around the clock, one of the highest operating costs is the air conditioning, which is normally set to 20 C requires one watt per watt used in computing functions. Air conditioning is used to control the temperature humidity in the data centre. The recommended temperature range is between 20 to 25 C (68 to 75 F) humidity range of 40 to 55 percent with a maximum dew point of 17 C as optimal for data centre conditions. The electrical power consumed by the servers heats the air in the data centre. Unless the heat is removed, the ambient temperature will rise, resulting in electronic equipment malfunction. By controlling the air temperature, the server components at the board level are kept within the manufacturer s specified temperature/humidity range. Air conditioning systems help control humidity by cooling the return space air below the dew point. Too much humidity, water may begin to condense on internal components. In case of a dry atmosphere, ancillary humidification systems may add water vapour if the humidity is too low, which can result in static electricity discharge problems which may damage components. ABB s electrical solutions for data centres Low voltage switchboards ipdus (Power Distribution Units) Active filters Power factor correction ipdus (Power Distribution Units) Remote power panel Power measurement Automation switchboards Variable-speed drives PLCs Control gear Air-isolated medium voltage switchboards Dry-type transformers i-bus EIB/KNX High-efficiency motors Variable-speed drives 4 Data centre applications for variable-speed drives l A guide to using variable-speed drives motors in data centres
Supply fan (A) Room air quality is controlled by changing the speed of the supply fan according to the CO 2 content of the exhaust air. The outdoor air damper will be opened when the fan is started. Operation is enabled when the damper is fully open (damper end switch). Accurate control to keep desired air quality/co 2 content Reduced maintenance of mechanical equipment such as belts bearings due to reduced operating speeds AC drive soft starting stopping Easier to maintain low noise levels Approximately 30 percent reduction in CO 2 emissions Return fan (B) Room pressure is controlled by changing the speed of the return fan according to the exhaust duct pressure. Return fan keeps up constant pressure in the exhaust duct by using PID control. Exhaust air dampers will be opened when the fan is started. Operation is enabled when damper is fully open (damper end switch). Accurate control to keep desired duct pressure Reduced maintenance of mechanical equipment such as belts bearings due to reduced operating speeds AC drives soft starting stopping Easier to maintain low noise levels Approximately 30 percent reduction in CO 2 emissions C Liquid cooler fans (C) Liquid cooler fans are controlled according to the temperature of the condenser water outlet. Condenser water temperature is kept constant with PID control. To prevent unnecessary cooling, liquid cooler fans are not started until the condenser water pump exceeds maximum speed. If water temperature falls too low, circulation can be stopped with a solenoid valve. Fans can also be programmed to run fixed speed for a certain time, for example once a week, to avoid condensation in the motors. B Easier to maintain low noise levels Accurate control to keep desired condenser water temperature Approximately 15 percent reduction in CO 2 emissions A Data centre applications for variable-speed drives l A guide to using variable-speed drives motors in data centres 5
Condenser water pump (D) Condenser water pump is controlled with a PID controller according to the temperature of the condenser water. Operation is enabled when the chilled water pump the chiller compressor are running. Accurate control to keep desired condenser water temperature Elimination of water hammer due to soft starting stopping Reduced pump pipe sizes Approximately 25 percent reduction in CO 2 emissions Chilled water pump (F) Chilled water pump circulates chilled water in a cooling coil according to the temperature of the supply air. Operation is enabled when the duct temperature rises above a preset level chiller compressor is running. Accurate control to keep desired duct temperature Elimination of water hammer due to soft starting stopping Reduced pump pipe sizes Approximately 25 percent reduction in CO 2 emissions Chiller compressor (E) The need for chilled water or CO 2 cooled racks can lead to space problems for one square metre of technical space, one square metre of plant space is required plus two square metres of ancillary accommodation space. This excludes any main substation(s) that may be required. An AC drive optimizes compressor motor speed to actual cooling dem. The compressor is controlled according to the temperature of the chilled water. The compressor s minimum speed is 60 per cent of its normal speed. Operation is enabled when chilled water pump condenser water pump are running. Approximately 20-50 percent energy reduction E F D Reduced peak dem charges Elimination of water hammer or hydraulic shock due to soft starting stopping Increased chiller life Tighter chilled water temperature control Reduced maintenance dem Approximately 20 percent reduction in CO 2 emissions 6 Data centre applications for variable-speed drives l A guide to using variable-speed drives motors in data centres
Expertise at every stage of the value chain Pre-purchase Order delivery Installation commissioning Operation maintenance Upgrade retrofit Replacement recycling Training learning Technical support Contracts The services offered for ABB s VSDs span the entire value chain, from the moment a customer makes the first enquiry through to disposal recycling of the drive. Throughout the value chain, ABB provides training learning, technical support contracts. All of this is supported by one of the most extensive global VSD sales service networks. Pre-purchase ABB provides a range of services that help guide the customers to the right products for their applications. Examples of services include correct drive selection dimensioning, harmonic survey EMC assessment. Order delivery Orders can be placed through any ABB office or through ABB s authorised value providers. Orders can be placed tracked online. ABB s sales services network offers timely deliveries including express delivery. Installation commissioning While many customers have the resources to undertake installation commissioning on their own, ABB its authorised value providers are available to advise or undertake the entire VSD installation start-up. Operation maintenance With remote monitoring, ABB can guide the customer through a fast efficient fault-finding procedure as well as analyse the operation of the VSD the customer s process. From maintenance assessment to preventive maintenance reconditioning of drives, ABB has all the options covered to keep HVAC installations operational. Should corrective maintenance of drives be needed, ABB offers on-site workshop repair, fully backed up by the most extensive spare holding. Upgrade retrofit An existing ABB VSD can often be upgraded to the latest software or hardware to improve the performance of the application. Existing installations can be economically modernised by retrofitting the latest drive technology to mechanical control equipment, such as inlet guide vanes or dampers or older generations of VSDs. Instead of replacing an entire VSD or system, it is often more economical to modernise the old installation by reusing all relevant parts of the original equipment purchasing new where necessary. Replacement recycling ABB can advise on the best replacement VSD while ensuring that the existing one is disposed in a way that meets all local environmental regulations. Entire value chain services The main services available throughout the value chain include: ABB s Bristol Training Centre offers product application training in the classroom. ABB also offers training courses at customer sites on the Internet. Technical support At each stage of the value chain, an ABB expert is available to offer advice to keep the customer s process or plant operational. Contracts DriveCare contracts other types of agreements, from individual services through to complete drive care covering all repairs even drive replacements, are available. Life cycle support l A guide to using variable-speed drives motors in data centres 7
Contact us ABB Limited Daresbury Park Daresbury Warrington Cheshire WA4 4BT Tel: +44 (0) 1925 741 111 Fax: +44 (0) 1925 741 212 www.abb.co.uk/energy Notes: We reserve the right to make technical changes or modify the contents of this document without prior notice. With regard to purchase orders, the agreed particulars shall prevail. ABB does not accept any responsibility whatsoever for potential errors or possible lack of information in this document. We reserve all rights in this document in the subject matter illustrations contained therein. Any reproduction, disclosure to third parties or utilization of its contents in whole or in parts is forbidden without prior written consent of ABB. Ref: Data Centre brochure/july 2014 Copyright 2014 ABB All rights reserved Printed in UK (07.2014)