Meeting global growth in power demand for Data Centres with green energy
The world’s hunger for data and computer power is accelerating rapidly. Every time anyone accesses the internet, applications are run on one of millions of servers, increasingly centralised into thousands of data centres. Data centres vary in size from small cabinets to huge warehouse-type facilities of many hundreds of thousands of square metres in area. Reliable power supply is critical to data centres, not just for the server functions, but also for essential infrastructure such as cooling. Estimates of power consumption by data centres vary widely – from 200 to 500 TWh. Compare this to the UK’s total power consumption of 288 TWh in 2020 and it is apparent that data centres represent a significant draw on global power generation capacity. There is also an increasing awareness of the potential impact of this ever-growing demand for data and connectedness on global carbon emissions – particularly in nations where primary energy supply is from fossil-fuels, most notably coal and oil. There has been a growing trend to site new data centres nearer to sources of renewable energy to cut emissions, but even in these cases, they require back-up power supplies (UPS or utility protection systems) to ensure continuity of service, which are fuelled by diesel generators.
Data centres comprise facilities to support the efficient operation of the servers, data storage and networking equipment within. This includes cooling and air conditioning, power distribution, back-up power facilities, lights and fire extinguishing. The power demand of the peripheral infrastructure means that the total power required by the data centre is higher than just for the servers – expressed as the “Power Usage Effectiveness” or PUE, this is a factor greater than 1 and typically ranges from 1.1 to 3, with an industry average of 1.67 reported in 2019. This means that an average data centre consumes 67% more power than is required just by the servers, data storage and networking. Combine that with typical power generation efficiencies of the order of 35%, transmission line losses and PUE, it is not unsurprising to find fuel-to-server efficiency of only 15-20%. Thankfully, server utilisation and power consumption per TB data traffic and PUE trends are improving steadily over time, tempering what would otherwise have been an exponential growth in data centre power consumption. However, these trends could be threatened by presently unquantified impacts on existing data centre utilisation and new centre construction from increased use of data-driven machine learning and artificial intelligence across many sectors. Growing use of renewable energy sources by siting data centres in countries such as Scandinavia and Iceland, with high proportions of hydroelectric and geothermal power, is also helping to limit the carbon emissions growth rate. However, this positive trend is also under potential threat due to an increasingly urban global population with the result that the distance of these ‘green’ data centres from the consumers is impacting network response time.
Local Power Generation for Data Centres.
Most major data centre owners have adopted renewable power purchase as part of their corporate Environmental and Social Governance (ESG) policy to limit carbon emissions from their operations. However, these renewable energy sources are often located far from the data centre, so there is still lower overall system efficiency due to transmission losses. Most geographies have at least one viable renewable source of energy, whether that is solar, wind, hydro, geothermal, others. The main issue is the variation of generation – throughout the day and across seasons. If the issue of variability can be solved through innovative storage techniques, there is no reason that data centres could not be powered by locally generated renewable energy, simultaneously improving both fuel-to-server efficiency and eliminating transmission losses.
CREAS CHP21zc “Combined Heat and Power for the 21st Century with Zero Carbon emissions” concept.
CREAS Energy Consulting has developed a concept for a modern zero-carbon emissions technology configuration that enables stable power supply to data centres (and other major power consumers). It can operate from a range, even a hybrid mix, of variable renewable energy sources and has the advantage that there is no requirement for a fossil-fuel based UPS system in parallel.
As the figure above shows, the concept makes use of green hydrogen generated in a water electrolyser using existing renewable energy sources, which would be sited at or near to the data centre location. The renewable power consumption would be more than the normal power demand of the data centre to generate a surplus that would be converted into green hydrogen. The hydrogen is stored locally to provide a buffer for periods when renewable energy production is lower – during the night in the case of solar power for example. A high efficiency hydrogen fuel cell is also located at the data centre, which generates power from the stored hydrogen when the renewable energy supply is lower ensuring the continual power supply required in all conditions. In case of any extended periods with lower renewable energy production than normal, import facilities can be provided to top up the local hydrogen storage.
Oxygen produced as a by-product from the electrolyser can also be stored for use in the fuel cell, and water produced as a by-product in the fuel cell can be recycled to the electrolyser, thus making the entire system highly efficient, with zero carbon emissions.
CREAS estimates that, with no direct consumption of renewable energy by the data centre, the electrolyser/fuel cell combination would generate power at 35-40% efficiency. If the fuel cell is in operation for 50% of the time, and the remainder was direct renewable power supply at 90%+ efficiency, the average efficiency of the system (source-to-server) would be of the order of 60-65%, which compares very favourably with various analysts estimates of 15-20% fuel-to-server efficiency from conventional fossil-fuel power generation approaches, quoted earlier.
To conclude:
· The global population is becoming increasingly data-hungry, which is driving up power demand from thousands of data centres.
· While there has been great improvement in server utilisation and in reducing power consumption per unit of data, the sheer growth in data volume is outpacing these efficiency gains.
· Global data centre power consumption was of the order of 1 to 2 times the total power consumption of the United Kingdom in 2020.
· Many data centres are in areas where the primary power supply is from fossil-fuels, which threatens to increase global carbon emissions and exacerbate climate change.
· Efforts have been made to locate data centres nearer to sources of renewable energy, with a primary focus on continuous power sources, such as hydroelectric and geothermal.
· Variability of widely available renewable energy sources, such as solar and wind, makes these more difficult to use for power offtake applications that require a continuous, steady production.
· CREAS Energy Consulting has developed a concept named CHP21zc (Combined Heat and Power for the 21st Century with zero carbon emissions), which integrates these variable renewable energy resources with the generation of green hydrogen by water electrolysis and the use of a hydrogen fuel cell to provide a continuous power supply that would be suitable for data centre and other similar applications.
For more information about CREAS Energy Consulting services or our CHP21zc concept, please contact us at enquiries@creas.co.uk or consulting@fuelcellsworks.com.