Bringing compute to the edge driven by solar power

Edge data centres are on the rise, driven by the requirements for low latency local compute resources. While they offer many advantages there is a concern that the small scale of these facilities will not allow them to take advantage of the economies of scale that have driven sustainability into their larger counterparts. However, in Australia one company, Edge Centres, pursuing the edge data centre market has come up with a solution to this sustainability challenge, marrying data centres with solar power.

The initial premise to combine data centres with solar power came about in Australia and was born out of expediency rather than the desire to use renewable energy. In such a fast-moving market it was crucial for a facility to be up and running as soon as possible. However, having found a new location for a data centre there was at least a six-month delay for the power to be connected. “We decide that if we installed solar power, we could run the data centre until the power went in,” Jonathan Eaves, Founder, Edge Centres, says. “Because obviously, if you want to roll up multiple centres quite quickly, you aren’t able to do if there is a six-month stock gap at each site.

“So, to try and launch eight facilities, which is our goal for 2021, we would not have been able to do that. We worked this concept through with the electrical engineers and soon realised there was an opportunity if we could increase the size of land required, we could introduce a lot more batteries, and run this as a fully off grid facility. That is effectively what we have achieved.”

In a volte-face to the traditionally power system design for a data centre once the location is connected to the grid that will be the back-up solution in case of any problem with the solar power or batteries. It is always primary solar, secondary battery, and tertiary utility.

The search for the appropriate technology

Armed with the initial plan from his electrical engineers it was not simply a matter of placing orders and starting the build. “The news that we could go all solar was a surprise and a disappointment at the same time,” Eaves adds. “We had this we can do this moment then when you try and find the relevant vendor to purchase the appropriate equipment you discover that they do not exist.

“We have investigated different battery types and vendors. Inverter choice is also very important, and the way the inverters talk to the batteries is equally as important. If you get an inverter type that does not like certain battery or battery management system, you can lose between 20 or 30 per cent of capacity on a battery, which for us, every percent counts.

For the solar engineers we met, they were used to grid or energy storage systems. When you try and explain that there is a constant 50-100 kW IT load plus air conditioning on 24/7, and you are not using utility, it was more challenging. Then you then go into the world of copious amounts of batteries and the relevant storage. Then depending on whether you use power trackers or use paralleling for the strings of the solar, determine your charge rate throughout the day.”

For the battery choice Eaves eventually settled for lithium-ion, as that was the most cost-effective per kilowatt price that come in at around $150 per kilowatt hour. Each battery cell is warrantied for ten years, and they are all 10 kW/hr modules. For the inverters the final choice was a brand that has independent and redundant modules internally. “A lot of the inverters are a single unit, and if it fails, you lose the unit,” Eaves explains. “On our inverter we stack 3 kW modules and if we lose a single module, we only lose the 3 kW not the entire inverter stack.”

It is clear from this experience that aside from the hyper scalars, who will struggle to achieve the required 100 MW of power from a solar farm, data centres can run even with just a small solar load and batteries. “You can run all of your lights, fire systems, access control and all of periphery equipment, quite happily for 24 hours within any budget,” Eaves continues. “I think it will be good to see companies start with that to actually start moving if not the critical loads or the critical equipment, but some of the non-critical loads on to solar is relatively simple.”

Where sustainability is a competitive advantage

Whether of not the move to solar powered data centres have given Edge Centres a competitive edge is unclear at present, but it has certainly generated a lot of interest. “We have had inquiries from all over the world, including Mexico, Panama, and Japan, so obviously we are going to build there,” Eaves says. “It has enabled us to get better involved with different technologies that will enable us to develop this further. As we go through this year, with different panels and different inverter types, we can now better progress this system. In Australia, because we produce so much self-solar, we have also become a power station. 

“I am effectively as much a utility now, as I am a data centre provider. Even though I only use the power myself I have had to obtain a power station licence to produce that amount. Then that allows me to create green credits, which annually then we can sell off to other companies, potentially even other data centre providers to offset their carbon, so a sustainable business supporting its own industry. Clearly obtaining a licence adds another layer of complexity and it is something the government takes quite seriously. It is about a 22-week process.

Where the sun does not shine

Around the world the efficiency of solar power varies dramatically based on the daily hours of sunshine and other environmental factors such as high dust levels that can adversely affect performance. “What we are looking for now is companies that own solar farms that we could add data centres to that will increase our speed to market,” Eaves says. “If there are providers out there that are generating power to the grid, there is obviously quite often excess capacity available that we would be able to tap into for data centre use.”

The current strategy is to have 20 facilities online by the end of 2022 and there are plans for expansion in Japan with two facilities in the country. Eaves cites Japan, Philippines, and Vietnam as the next areas for growth. “When we look at the world in Asia, the hyper scalers have obviously hit Australia, New Zealand, Korea, Japan, China, Indonesia, the Philippines, and Vietnam. By creating an edge facility or carrier hotel in these regions would be a good opening for us.”

With the number of edge data centres predicted to grow exponentially over the coming years and sustainability a growing imperative for users, these small, solar powered data centres look set to meet that requirement.

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