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Is gas the future of data centre standby power?

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Data centre expansion will add over one and a half million tonnes to Ireland’s carbon emissions by 2030, according to the Irish Academy of Engineering. With emissions on the rise, using gas to power standby gensets could help reduce harmful pollutants generated by data centres. Here, Martin Byrne, sales manager for Gas Power Solutions at energy and transportation expert Finning UK & Ireland, explains why gas is the future of data centre standby power, and what operators must consider.

Critical facilities like data centres require optimal uninterrupted power 24 hours a day. Any lapse in power is an issue – it can result in files being lost or corrupted, mainframes malfunctioning, and money being lost. Backup generators provide vital standby power, keeping the site online during outages.

Data centres can produce power themselves using prime gas gensets or as part of combined heat and power (CHP) systems.

Generating electricity on site is preferable to relying entirely on what can be a flexible network connection. For these sites, gas is cheaper and more efficient than running a diesel prime generator.

However, many data centre operators use diesel to power their standby gensets because these machines can accept significant load steps quickly after an outage. The priority is keeping the system running to prevent outages that cost customers money.

Diesel generators offer long runtimes and require minimal maintenance because they don’t have carburetors or spark plugs, meaning that operators can be confident that the site will keep running at minimal cost. Nonetheless, there are signs of a growing trend towards using natural gas to power backup generators as well as prime.

Reducing emissions

One reason gas is becoming a more attractive option for data centres is the demand for clean energy. The Irish Government has set itself the ambitious goal of cutting greenhouse gas emissions each year and becoming carbon neutral by 2050. For data centre operators, this may mean selecting a more environmentally friendly fuel to power their generators.

As previously mentioned, gas is already being used for prime and continuous power generation. In 2017, a major computing company announced it would install 16 gas-powered gensets to provide up to 18 megawatts of electricity to one of its sites in Dublin. However, these sites might still use diesel to power backup generators – emitting harmful pollutants.

Installing gas generators for standby power will make it easier for companies to comply with emissions standards. For instance, under the UK climate change agreement (CCA) scheme, data centre operators have been expected to reduce their power usage effectiveness (PUE) by 15%. While natural gas is a greenhouse gas — methane — it produces fewer pollutants than diesel when burned.

According to Clean Energy Fuels, natural gas emissions produce 99% less sulphur oxide (SOx), 80% nitrogen oxide (NOx) and 40% less carbon dioxide (CO2) than diesel.

Capacity market

The trend towards gas is also being driven by the grid. Data centres are power hungry, which can put significant pressure on the surrounding network. Because of growing power demand, companies and sites in the UK, including data centres, are being offered flexible contracts where they agree to provide supplementary power to the grid or self-generate their own power.

In 2020, a UK Government consultation proposed making it easier for companies to bid for these contracts by reducing the minimum capacity threshold from 2 MW to 1 MW.

Like diesel models, gas generators can synchronise with the grid, generating on site power in conjunction with the incoming supply. They can do this by producing a constant output and providing a base load that is potentially cheaper than power from the network. If the site purchases its power from the grid, gas gensets can provide additional capacity when required. Either way, by generating supplementary power on site, data centres can help balance out the grid when it reaches its limits.

As the capacity market grows along with the incentives to generate power on site, it will be easier for data centres to make the switch to gas standby systems, because sites will have already installed the required infrastructure, such as gas mains valves. Consequently, the jump will be far smaller than if operators were making a clean break from, say, diesel prime.

Engineering and maintenance

While it may be tempting to switch straight from diesel to gas, it’s not as simple as converting a generator. Operators will need a new machine with low hours that has been designed to run on gas. Another consideration is how the gas standby genset will fit into the data centre. It could require a different uninterruptible power supply (UPS) design than a diesel generator, meaning that some ancillary parts may need replacing before the genset can function.

There is also size to consider – the power-to-weight ratio is lower for gas gensets, meaning that the machine will often be larger than a conventional diesel model.

Sizing is critical because oversizing a system can increase costs.

The genset will take up more space, have higher operating costs and consume more fuel than a smaller machine. Undersizing will result in inadequate backup power supply, meaning the genset could stall or fail to start.

To address the balance between space and power, engine manufacturers have released products with high power densities. Power density measures the number of kilowatts produced in relation to size – the higher the power density, the higher the output from the plant room. The trend towards gas will gradually drive manufacturers to produce machines with good power-to-size balances, as supply catches up with demand.

When designing a generator for a data centre, consider fuel alternatives early because the fuel will often determine maintenance regimes. For instance, servicing is crucial for gas generators because of the mains supply that is fed into the machine. Sometimes, these gensets might need to be checked weekly. If operators are unsure about servicing requirements, they can consult the manufacturer’s recommendations.

While Ireland’s data centre expansion is forecast to contribute over one and a half million tonnes in carbon emissions, an early trend towards gas standby gensets looks promising for the reduction of harmful pollutants. If it is a trend, it’s being driven both inside the data centres with the reduction of greenhouse gases and outside from the grid.

Could gas be the answer for your data centre’s power needs?

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