For a long time in the data centre industry, the BAT (Best Available Technique) for large-scale embedded generation has been widely accepted as Combined Cycle Gas Turbines (CCGT), maximising electricity generation. With the recently released emissions drivers from the Environment Agency, there is increasing need for new, emerging technologies that provide an inflated rate of efficiency. That solution could be Combined Cooling, Heat and Power (CCHP); technology providing electricity, heating and cooling with significantly higher fuel efficiency.
What is CCGT (Combined Cycle Gas Turbines)?
In many industries, CCGT is the widely used technique for efficient power generation – it utilises waste heat through exhaust gases which pass through a Heat Recovery Steam Generator, boiling water into steam. This can then drive a second turbine and generator. While it is thought that the efficiency of these systems have an efficiency rate of around 50-60%, we are starting to see that this may be incorrect – to maintain N+2 availability, a generation system has to operate with significant spinning reserve to absorb instantaneous IT load spikes and cooling system transients. This results in a CCGT configuration operating continuously at 60-75% to maintain this reserve margin.
Due to these conditions it’s likely that the CCGT thermodynamic efficiency would collapse, bringing the efficiency rate down to below 45%. The nature of CCGT also demands starting and stopping the units to follow load curves, which results in a huge amount of fuel burn without generation, furthering damaging its efficiency rate. Furthermore, CCGT is incredibly sensitive to temperature and generally has a much lower optimal operating window compared to a RICE unit used as a distributed generation asset in CCHP configurations.
The new and improved solution – CCHP (Combined Cooling, Heat and Power)
While CCHP systems (an example of which is Reciprocating Gas Engines and Organic Rankine Cycle (ORC) systems) are not new, they have barely been introduced within data centre infrastructure. Generating more and more interest, it’s technology that could increase the overall efficiency rate of the data centre it’s embedded in and maximise fuel usage.
Using advanced medium-speed reciprocating gas engines integrated with a high-capacity ORC thermal recovery system, the technology is designed to operate for 8,760 hours a year, running continuously in the background. Building on the foundations of CHP (Combined Heat and Power), this technology produces three useful outputs – electricity, heat, and cooling – via the waste heat generated from the combustion of the single fuel source used. The waste heat can also be used to provide hot water for heating the data centre, and this can further be used for space heating in surrounding buildings.
This addition of cooling capability is a valuable one. Cooling systems are essential but consume a high amount of energy, at times accounting for up to 40% of total energy consumption of the data centre. Reducing this energy consumption is a strong benefit of CCHP, allowing for the necessary output while reducing carbon footprint.
Water consumption is a huge problem that CCHP can tackle. Data centres deploying a CCGT system require large quantities of water for condensing, and this is becoming unsustainable environmentally, as well as generating public backlash. CCHP on the other hand, operates on entirely closed-loop refrigerants and utilises dry air radiators. This results in continuous generation water consumption dropping to almost zero, providing an enhanced Water Usage Effectiveness (WUE) that CCGT can’t compete with.
The necessity of new technological solutions
CCHP is becoming a hot topic in the data centre industry for a widely known reason – the Environment Agency (environmental regulator for data centre development) now requires a stricter focus on accountability for energy consumption and efforts to improve a facility’s carbon footprint.
Data centres are increasingly investing in on-site generation due to the grid constraints experienced throughout Europe, and reporting requirements therefore award them greater responsibility for managing their energy consumption conscientiously. They are also required to include their energy use and carbon emissions data in annual reports as part of Streamlined Energy and Carbon Reporting (SECR), and this requires operators to document what they’ve actually done to improve their energy efficiency.
In considering CCHP as a solution, it’s important to note that CCGT is currently accepted as the BAT (Best Available Technique) – techniques that are the most environmentally effective and economically and technically viable for the prevention and control of emissions – but that as part of the Industrial Emissions Directive 2.0 (IED) alternative techniques that ensure “at least an equivalent level of environmental protection” are accepted. This is where CCHP comes in.
Utilising waste energy, Combined Cooling, Heat and Power can bring the overall fuel efficiency of a data centre up to 70-80% in some cases, solidifying it as a technique that surpasses the environmental protection that CCGT provides. Capable of lowering carbon emissions, it maximises the fuels already being used in the generation of independent power for microgrids.
Putting it in action
While not seen commonly in data centre infrastructure yet, this is something that we will likely see on the horizon. Microgrids are fast becoming a valid, replicable source of power generation for data centres, with our project with Pure Data Centre Group leading the way. The rise of on-site generation may consequently catalyse the rise in CCHP, as sustainability and energy efficiency are coming into sharper focus during the process of data centre design. This is something data centre operators should not bypass – innovative solutions are the way forward.