Power considerations for data centre development

1) I'm interested in how district cooling is achieved when data heat centres are a net generator. What is the mechanism?

Waste heat (hot water, steam, exhaust gas) can be used instead of electric compression in a refrigeration cycle. Sorption chilling is the process that can be used. Once chilled water is produced it can be distributed to consumers in a district cooling network like hot water can be distributed in a district heating scheme. 

Essentially, waste heat (depending on the temperature and quantity) can replace offset electrical load for the electric compressors in a traditional cooling system. 

2) Is modular hydrogen generation an option? 

Possibly, but the source of 20+ years of reliable supply of H2 at these scales is not available in all markets. Hydrogen fuel cells can efficiently convert H2 into electricity, but the technology is yet to be implemented at this level of scale. Some gas turbines are capable of running on H2, but due to the nature of the combustion NOx emissions increase significantly. Gas turbine OEMs are working on developing 100% low NOx emissions combustion systems. This may be an option in the near future. 

3) Are there newly developed mission-critical substation equipment solutions specifically designed to support data centres, as opposed to conventional major substation equipment?

Yes. The core equipment is largely the same, but the configuration of busbars, switchgear and containerised solutions have and continue to be developed to increase reliability and availability. Along with the development of protection and control systems to complement this.

4) What is the process to use waste heat for nearby homes? 

Generally, the waste heat can be captured via heat exchanges to a secondary hot water circuit. The hot water circuit can feed an underground pipeline that feeds each house with a separate branch line. The house will include a heat exchanger (in the location where a traditional gas boiler might sit) that takes heat from the district heating circuit and uses it to heat the radiators or other heating system in the house. 

5) Is battery storage technology currently sufficient to act as the sole backup power source for a data centre? 

Potentially, but the size may be prohibitive. Typically, at least 24 hours of back-up power is required. For a 200MW data centre, then 200MW x 24 hours is a 4.8GWh battery. From a cost and a physical size perspective this could be a challenge. 

6) Any solution against lead time for GT and recips?

Yes, but it comes down to the economics. The real shift is that power equipment procurement is now a first-order design decision, which flips the design workflows and deliverables.

7) Can renewable energy power data centres?

Renewable PPA’s can work, but only if there is a grid to provide the power. Off-grid solutions are unlikely to have solely renewable power since it would not meet the availability requirements. Renewable power can certainly be part of the off-grid power solution mix, but it will likely come down to the payback period of the energy solution and any regulations that have to be followed. Hence the suggestion for the data centre developers, regulators and grid operators/owners to develop power solutions that are more sustainable and mutually beneficial.  

Some governments are also mandating that data centres submit development proposals with Power Purchase Agreements in place with renewable energy companies. In Australia, data from the industry body indicates that renewable energy accounts for 80% of the energy supply to data centres. The issue is the availability of energy, as renewable energy schemes themselves come under increasing social license issues.

8) Do data centre developers have a preference for grid connection voltage and/or battery limit to interface with new connection infrastructure that is required to be built? 

It can vary significantly from location to location. In general, the data centre developers would prefer to focus on the data centre and not the power. So, a conventional grid connection with step down transformers to the specific data centres preferred voltage would be the simplest solution for the data centre developer.

9) When it comes to power - what are demand profiles, particularly in terms of load intensity and variability? And to what extent is demand flexibility realistically achievable (e.g. separating latency-sensitive vs non-latency-sensitive workloads such as AI training vs inference), as seen in some Google and hyperscaler initiatives in the US? Specifically, can portions of load be shifted or scheduled to align with periods of lower electricity prices? 

This is an area undergoing rapid change. For traditional data centres and cloud data centres, the loads are fairly smooth and predictable. With the use of onsite generation, load shifting from the grid can be done. For the AI training data centres, load shifting likely can be planned to some extent, but there are less predictable millisecond load swings that need to be managed across all scenarios. For AI inference data centres, the load shifting may be managed in a similar way to traditional data centres by transferring the load to onsite behind the meter generation at times of peak grid demand or in times of high electricity prices. The key part is early-stage communication between the developer and the grid operator/owner to get systems designed that suit both parties. 

10) What "believable" steps are being taken to counteract the overall heating impact (referring to global warming)? 

There are a number of steps, but if we focus on one: Hyperscalers are now some of the largest global buyers of renewables, directly funding new wind and solar through PPAs. Importantly, data centres are often the financial underwriters that make large-scale renewable projects viable. They provide the long-term, bankable demand needed to unlock investment and provide energy for the data centre as well as the broader community. 

11) BESS connection with grid is also a very long process as BESS is treated as generation/FCAS. In this case Grid-BESS-Data centre trio can also create another planning, approval issue?

There are many complications with this model, but in the long run it may benefit both sides to buffer issues on either side. Further development work needs to be done on this concept to prove it out.

12) What electrical technology is the preferred (and why) by DC to cope with grid stability and fault ride through requirements? 

The preferred solution is an FRT-capable UPS with integrated battery storage (BESS). For hyperscale AI data centres, this is increasingly being supplemented by STATCOMs and grid-forming inverters to improve voltage stability, meet grid-code requirements, and keep the facility online during normal and abnormal network disturbances. 

13) What are the main differences do you see between typical solar/BESS inverters vs data centre inverters?

There is little difference in the technology behind the designs, full four quadrant, synchronous inverters are common for BESS and DC, where solar sites may be asynchronous in their power sizing.  DCs and some batteries have grid forming qualities where they have control and designs that can generate, stabilise and protect their own grids for voltage, frequency and faults rather than grid following alone. 

14) Why would we not ask all applications bringing their own power to use 100% renewables?

While great conceptually, the issue is the scale of power required, the extremely high reliability requirements, the cost and the ability to plan, approve and develop renewable energy projects at scale. 

15) Before the data centre boom, it felt like diesel generators and DRUPS systems were becoming a bit of a dying breed. Now they're in massive demand again because of data centres. Where do you see the industry heading over the next 10–20 years? Are there any new technologies or innovations that could change the role of standby generators? And for the more traditional generator companies, do you think they'll continue to do well, or is there a risk they'll get left behind? What are some ways those businesses can innovate and stay relevant as the industry changes? 

There does appear to be a shift towards BESS, UPS, Fuel Cells, 800V DC systems and renewables in various combinations to try and move away from back-up diesel generators, but in the short-medium term this looks unlikely to cover all data centres. The high availability of these units and quick start capabilities make them attractive as back-up systems. Going forward, integrated packages that include a reduced number of back-up diesel generators mixed with BESS and renewables may be more attractive to reduce fossil fuel consumption without negatively impacted availability. Overtime, the advancement of fuel cells technology and a shift from chemical to solid state batteries may enable the back-up diesel generators to be removed from the system.

16) With the current increase in building data centres, do we see more fossil fuel-based electricity generations to see those demands or renewables?

There is going to be an increase in fossil fuel-generated power, because it is available. However, as renewable energy schemes develop off the back of PPAs, the reliance on fossil fuels will reduce.  See Q10, more for more information.

17) How do data centres impact the power quality and harmonic contributions? How do you plan data centres locations with respect to grid demand? Likewise, how do you address inertia requirements vs sensitivity for faults when installing Syncons? 

AI data centres can challenge the grid through large, rapidly changing power demands that affects voltage stability, system strength and possibly frequency control; therefore, they are best located on strong transmission networks with high fault levels, using a combination of synchronous condensers, STATCOMs and grid-forming BESS to maintain power quality without creating excessive fault current and associated disturbances.  Interestingly if STATCOMs were used to support the supplying network, voltage management and its control could enhance better network performance and its granular voltage controls with accurate reactive power support.

18) What is the typical fault current that the data centre expects to generate in the event of a problem? And any black start requirements? 

This varies significantly depending on the data centre design and if there is any behind the meter generation. This needs to be assessed and considered as part of any grid connection.  

Black start requirements would vary depending on the site. If the data centre is islanded (or installed prior to the grid connection) then the site would need to be capable of black starting itself. Black starting of the local grid would be dependent on the specific grid constraints and any agreement with the grid operator.

19) What are the requirements or preferences for integration of heat. There are dozens of possibilities but two illustrative examples are: (a) The data centre uses the power station's cooling circuit / cooling tower for its heat rejection or (b) The data centre uses the power station's waste heat (or steam supply) for an absorption refrigeration cycle? 

In warmer climates it is likely to be more cost effective and efficient to use waste heat from the local power station to provide cooling to the data centres (via absorption chillers) as the electrical compressor load is replaced by the absorption process. In colder climates this process is less likely to be cost effective, so utilising this to waste heat in a district heating system for external uses may be more efficient.  

The cooling circuit/cooling tower option mentioned may only be applicable if the power station has such a circuit. For small open cycle gas turbines or medium speed reciprocating engines (typical of the current behind the meter solution) the cooling circuits are unlikely to be large enough to be of benefit. 

20) Are waste heat solutions seasonal? Are district heating needs inverse to heat availability from DCs? 

Yes, absolutely, but it depends on what the end use is. 

21) What is the largest behind the meter data centre that you are aware of in terms of the demand supported without relying on a grid connection?

The largest one that GHD has worked on has an energy centre with a maximum capacity of 200MW. However, there are planned projects with multiple GWs of off grid power to data centres. 

22) Can BTB BESS displace partially backup generators and LV UPS? 

There does appear to be a shift towards BESS, UPS, Fuel Cells, and 800V DC systems and renewables in various combinations. Overtime, the advancement of fuel cells technology and a shift from chemical to solid state batteries may enable the removal of UPS, but the power quality required at the racks is the critical item that would have to be demonstrated by these types of arrangement before this will happen. See Q5 for more information.

23) Was any waste to energy plants considered anywhere in the world to supply power for data centres? 

The underlying issues are finding a community willing to accept a waste-to-energy (W2E) facility, access to a reliable waste stream and operating consent conditions of the facility, i.e., not 24 hours. So, W2E can be part of the energy mix, and a data centre can enable economic viability of a facility, but there are other matters to be considered. 

24) Can data centres improve power quality on low-loaded lines and eliminate the need for system stability equipment?

Data centres themselves are simple load cells made up of hundreds of individual assets, as such they cannot improve power quality.  However, the power supply configurations for data centres can support an improvement in power quality by smoothing voltage swings and reducing the impact on grid by utilising their power systems components such as BESS and Stacom's. These devices may also limit fault levels of the grid.