The 37 megawatts Microsoft will be getting from GE's new Tullahennal wind farm in County Kerry, Ireland, will bring the total amount of energy the company is getting through renewable generation around the world to 600MW. But its power purchase agreement in Ireland to supply data center energy, announced earlier this month, is about much more than that.
The project is a pilot designed to understand how much energy storage the hyper-scale cloud operator needs to fully run on renewable energy, Brian Janous, Microsoft’s general manager of energy, said in an interview with Data Center Knowledge.
Like other renewable energy sources, wind is intermittent, which makes it inferior to coal or gas-fired power plants in terms of predictability of output. That means regardless of how many wind turbines or photovoltaic panels you string together, you still need conventional generation capacity online to supplement the supply whenever the weather is not optimal for renewable generation. As more and more renewable sources contribute to the overall energy mix, the industry is looking for ways to even out the peaks and troughs without relying on fossil fuel.
The most common technique today is pumping water used by a hydroelectric power plant uphill overnight, when demand is low. Also common are using that cheap off-peak energy to compress air and store it in the caves of old salt mines and storing heat absorbed by solar facilities in molten salt, using it to drive turbines overnight.
Microsoft and GE are taking a simpler and smaller-scale approach, pairing each wind turbine with an integrated battery. The idea is to use GE’s industrial analytics solution, Predix, to combine weather forecasts and a “digital twin” of the turbine (GE’s name for the totality of data available about an industrial asset, which includes things like sensor data, service information, and reports from other turbines) to predict how much power each turbine is going to generate.
If a turbine produces more power than the grid needs, the excess gets stored in the battery; if it doesn’t produce as much power as predicted because the wind speed has fallen, the battery can top up the output. That makes the wind farm’s power output more consistent and predictable (a must for a data center energy supply) and brings it online more quickly when there’s demand.
That sounds so logical, you might wonder why it’s not already common. This is the first production wind farm in Europe with integrated batteries, although GE has been selling hybrid wind turbines with battery cabinets since 2013 and can retrofit batteries to existing turbines, while rival Vestas tested a lithium ion battery on a turbine in Denmark the same year. (This is also Microsoft’s first renewable energy project outside the US.)
Predictive analytics has become much more powerful in the last few years – and batteries are dropping in price. “Part of the reason that it hasn’t generally been done is that batteries on the whole are expensive,” Janous told us. “We’re getting to the point now with the cost decline in batteries that this is the beginning of what I expect to be a longer-term trend with the integration of renewables and storage.”
The Tullahennal wind farm has what he calls a relatively small amount of short-term storage. “With this pilot, what we’re really trying to do is show the viability of this solution to do the integration of wind and batteries. The focus we have is proving that the technology can work in the field. We have other projects where we’re working on longer-duration batteries, like flow batteries, but there’s still some work to be done on discovering what does the electrical grid actually need in terms of storage and how best to integrate it; so we’re casting a relatively wide net right now.”
How Much Energy Storage is Enough?
There are still some fundamental questions about what storage is needed for renewables. One of them has to do with the amount of storage you need. “People think that if you put 400MW of wind or solar on the grid … you need 400MW of storage to integrate that, and you really don’t. You need something far less than that, because there’s a tremendous amount of variation on the grid, in terms of demand and variability.”
Because the battery is topping up rather than replacing the output of the wind turbine, you don’t need to store an hour’s worth of energy to be able to guarantee output over the course of an hour. In Australia, Vestas is working with Tesla to build a combined 60.2MW wind and solar farm with 4MWh of lithium ion battery storage to even out the 43.2MW of wind power and 15MW of solar.
Microsoft already has wind power generation in the US and will be commissioning its first solar project there in a couple of weeks, Janous told us. “We’re technology-agnostic when it comes to how we get energy. To date, wind has been the largest contributor of clean energy in our portfolio because of the cost advantage it’s had, but we’ve seen significant declines in cost of solar in the last couple of years, and we expect that to make a larger contribution in the future. We’re also looking at other resources and other types of baseload, like biomass. These tend to be a lot harder to do at scale, but we’re doing some investigations to see if it will be a viable solution for us for data center power.”
While the long-term goal is to have its data centers fully supplied by renewable energy, demand for Azure in Ireland is pushing Microsoft to install 16 gas-powered generators that could supply 18MW for the four new data centers it’s building in Dublin, because of concerns that the local grid can’t meet all that demand. “That’s a temporary solution to potentially address some of the gaps we have with capacity; it was never intended to be a long-term solution for us,” Janous said, noting that Microsoft continues to look at other generation projects in Ireland.
Those might include selling surplus energy to the grid. His team hopes to build an “integrated system behind our meter, which includes backup power generation and storage as part of the grid.” The vision is to make data centers active grid participants by using energy storage and controlling the amount of load they place on the grid. “If we’re making those investments, let’s invest in things the grid can use that provide value in terms of efficiency and cost.”
Placing data centers is a balancing act, and Dublin is attractive because of low-latency connectivity and EU data sovereignty requirements. “Part of my remit is to look at power as part of the entire solution, not in a silo,” Janous said. “I work with the data center team to see where can we site data centers that optimize for low-cost, abundant clean power, and also latency requirements for our customers.”