Data centres are high energy users, consuming significant amounts of electricity for their operations and in parallel require cooling for optimal performance. The high energy usage also means they potentially have high carbon emissions. These factors make data centres an interesting new frontier for combined heat and power technology. Or as there is a primary requirement for cooling rather than heating – combined cooling and power (CCP) – using absorption chillers to convert surplus heat to cold water that can be utilised in their process.
Data centres went through many significant developments in the last decades. In accordance to Moore‘s law, the number of transistors has doubled approximately every two years. However, since global data traffic and number of people connected to the World Wide Web steadily increased, the capacity of data centres grew in tandem. Depending upon the expected data traffic and equipment to fulfill certain uptime requirements, data centres can either occupy a room or be as large as an entire building, with up to 25,000 servers and a power draw of tens of megawatts of electricity.
Data centres are high electric energy consumers, resulting in very high electric power costs. They require high-quality energy in terms of reliability to ensure continuous operation. Future challenges for data centres are electric load densification and an increase in thermal dissipation of the servers. Thus assessing the energy usage and energy efficiency is crucial and achieved by measuring metrics such as power usage efficiency (PUE), meaning the ratio of total facility power to IT equipment power, and water usage effectiveness (WUE). PUE and WUE are especially important, since a data centre’s capacity is usually limited by the performance of cooling system and the total electricity cost rather than by the processor performance.
Data centres are distinguished by their availability classified by tiers: The higher the tier, the more robust and continuous is the data centre’s operation. The uptime requirements rise from 99.671% (Tier 1) to 99.995% (Tier 4). This induces a higher redundancy of the installed components to reach higher tiers. The global amount of digital information created doubles every two years, implying an at least likewise increase in required data centre infrastructure. Thus, it is a must for data centres to be most flexible in terms of expansion and hardware upgrade. In conjunction with upcoming green energy initiatives, high efficiency and a reliable, modular infrastructure are inevitable prerequisites for state of the art data centres.
Data Centre Power Consumption
It has been estimated that the UK data centre industry requires approximately 3 GW of energy each year, making it one of the largest consumers of energy in the economy. The banking and finance sector currently accounts for the greatest percentage of overall UK data centre energy use, closely followed by IT services, media and telecommunications. The UK is the third largest consumer of data centre-related energy in the world behind the US and Japan.
Another important consideration for data centres is the decline in the UK’s spare reserve capacity which is forecast to push electricity supply margins into the negative according to the National Grid data published in late February. Britain will be forced to rely on imports and costly emergency measures to prevent blackouts.[i] This mismatch could result in the National Grid calling for capacity through the short term operating reserve (STOR) or supplemental balancing reserve. This situation is set to continue into the medium term with the delivery of the Capacity Market. The implication for data centres is the National Grid is becoming less reliable and the possibility of black-outs is more likely. The case for self-generation of electricity and cooling on site therefore becomes more attractive to prevent against supply interruptions.
First Data Centre CCP Project in the UK
In October 2014 Citibank developed a data centre CCP project in London, one of the first in the UK to utilise gas engine technology to deliver a CCP plant for a data centre. These innovative energy efficiency measures means the datacentre’s energy use can be reduced by 10%. The CCP plant, now installed and complete, is able to provide 71% of the electricity needed to power the data centre.
This high profile project was supported by the Green Investment Bank fund manager Sustainable Development Capital (SDCL) – a key acknowledgement of the important of this technology in helping reducing datacentres’ carbon foot prints.
The Chief Executive of the UK Green Investment Bank commented ‘The IT industry is one of the most energy intensive sectors globally, second only to aviation. Energy can represent up to 80% of the cost of running a data centre, so they provide an important opportunity for energy efficiency measures.’[ii]
With a total project investment level of £5.2million the 2.8MWe CCP project deploys a range of energy efficient technologies delivered through a turn-key project by Clarke Energy including absorption chillers, and two of GE’s J420 Jenbacher gas engines.
In summary data centres are realising the potential benefits of deploying gas-fuelled combined cooling and power plants in the UK. This technology enables the data centre to reduce operational costs, carbon emissions and in parallel generate stable supplies of power that can be relied upon.
[i] Telegraph (2016) UK energy supply forecasts ‘into the red’ for first time next winter https://www.telegraph.co.uk/news/earth/energy/12175367/UK-energy-supply-forecasts-into-the-red-for-first-time-next-winter.html
[ii]Green Investment Bank (2014) UK data centre to cut energy usage in first of a kind project https://www.greeninvestmentbank.com/news-and-insight/2014/uk-data-centre-to-cut-energy-usage-in-first-of-a-kind-project/