Greener Powering of Data Centre Facilities

The race to provide greener power to data centres is very much in play, however there is no one solution that appears to be taking the lead. In this article, we look at the options and opportunities to provide power and energy to achieve a lower carbon impact for data centres.

Greener Powering of Data Centre Facilities — Natural Gas as Fast Prime Power

Traditionally, data centres main source of power comes from the local utility and are supplemented by on-site support with diesel powered generation as backup in case the utility fails. This arrangement, if designed correctly, can provide the all-important overall availability of 99.999% that many end-user, colocation providers and technology companies so desire. The problem with this arrangement, from a carbon impact perspective, is you are not in control of how the utility power is generated (as it is a mix from the local or national grid) and you are defaulting to a fossil fuel-based generator for standby power. Additionally, local governments and local authorities, are having to consider the emissions (NOx and particulates) from generators much more carefully due to the risk on health, particularly in urban areas due to national environmental targets.

So, what are the alternatives?

Using natural gas to generate electricity on-site has been considered by many data centre owners. Whether using gas engines or gas turbines, they were originally considered in combined heat and power formats where the waste heat could be used to generate chilled water for cooling. Nowadays, in temperate climates, chilled water is no longer used as internal environmental conditions have widened significantly since the adoption of the ASHRAE TC9.9 2011 data processing guidelines, instead direct or indirect fresh air with adiabatic top-up for peak conditions. Using gas generation for permanent power, therefore, has to be considered on its merits for producing electricity only while still considering the impact on emissions and carbon footprint given that natural gas is a fossil fuel.

Gas generation has much lower emissions profile and is more efficient than diesel generation, but the argument is that if your utility supply is now sourced from renewable energy such as wind, solar and hydro, then it is better to use the utility instead of gas because its carbon impact is lower.[1] This now leads to the consideration of using gas generation for standby use only, utilising gas engines rather than CCGT due to their quicker start up time. This is possible, but designs have to take into account factors such as extended start up times and less stability when loads change. Given the above, in some city locations, gas powered generation is a possible option.

In most countries, gas powered generation is assumed to use natural gas that has been extracted from deep sea or land wells; however, there is legislation being proposed in many countries to move away from the dependency of gas based on fossil-fuelled natural gas. Many gas utility grid companies are now looking at alternatives, including the displacement of natural gas with “green” hydrogen, biomethane and/or abated natural gas. For example, Gas Networks Ireland have published their Vision 2050 showing they intend to have no fossil fuelled gas in their networks by 2050 [1]. While an ambitious target, it nevertheless shows the potential movement in the fuel sector.

Diesel generation still has a place and can be used because of the availability of different fuel versions and the use of selective catalytic reduction units in the exhausts. For example, hydrotreated vegetable oil or biofuel is fuel that is fossil free and has a very low carbon impact, but still must be treated in terms of emissions. While this can be combined with SCRs to reduce emissions, the cost of these measures must be considered together against alternatives.

Fuel cells are also a potential provider of power. These continue to be considered but there are various issues that must be considered such as:

• Maximum size of modules (typically 300 to 500kW)
• Spatial requirements for the fuel cells, inverters and transformers
• Heat rejection is typically 50% of power capacity
• Fuel input delivery using options like natural gas or purified hydrogen
• Using the cells for continuous or standby requirements
• Emission levels are virtually zero
• Overall high cost per kW compared to engine-based power production

To date, once all of the issues have been considered, fuel cells are usually not selected; however, it is thought that in the next 5 to 10 years, with the pressures to reduce the impact of carbon and emissions, the use of fuel cells could become more likely.

Renewables On-Site/Local Area

The ultimate goal is to provide power to data centres that has no carbon impact using "green sources." The ultimate greening of power to data centres is to use renewable energy that can be provided on or local to a data centre site. However, this can be very difficult because sites do not usually have spare open space to lay out large arrays of solar photovoltaic cells or wind turbines. To combat this challenge, data centres can team up with local providers of solar, wind or other forms of energy production. In many countries, this requires changing licensing or legal framework to allow renewable energy production sites to directly connect with data centre sites over public highways or similar. Most countries’ current licensing does not allow this to happen, although there are indications that some legislative/policy makes are considering to make this happen soon. If this changes, renewable energy combined with battery technology to smooth out the generation vs load profiles, will likely provide significant improvements in data centre carbon profiles.

Conclusions

The pressure to make power and energy usage for data centres as green as possible is on the rise. Many colocation and technology companies have already stated their ambition to be carbon neutral or adopt a net zero carbon target. For these targets to be achieved, technologies such as low carbon gas, diesel fuels in engines or alternative processes are being actively considered. Several factors such as cost, adoption, and new technology development have to be taken into account. The industry is already seeing some adoption of alternative technologies being implemented by a range of data centre operators and companies and expect to see the trend grow in coming years.