The ever-growing demand for data storage warrants the construction of more powerful, larger data centers that threaten to overwhelm the Earth’s limited surface land. Underground data centers serve the same functions as their above-ground counterparts while using less land.
This article explores the advantages and disadvantages of underground data centers, their design, environmental impact and construction requirements, as well as real-world examples.
Pros of underground data centers
An underground data center can operate more efficiently, consume less energy and have a lower carbon footprint than above-ground facilities.
Boost construction speed
Underground structures can be repurposed for data centers. Repurposed structures are usually old mines or bunkers that have been renovated as an empty shell — a space that can be filled with data halls. This method is significantly cheaper and faster than constructing a new data center above ground.
Limit surface land use and community impact
Above-ground data centers take up anywhere from 100,000 square feet for an average-sized facility to millions of square feet for the largest of hyperscale data centers. This takes away from valuable uses of land, like farming and nature preservation. Construction of above-ground data centers leads to deforestation and excessive noise that affect the environment and local communities.
Underground data centers use significantly less surface area, enabling the preservation of Earth’s limited available land. Underground facilities also produce less noise pollution, as construction is faster in a preexisting environment, and noise from operating facilities is absorbed through the data center’s insulation and the earth that surrounds it.
Provide low latency
The physical distance between data centers and users impacts data latency. Due to land restrictions, traditional data centers might be located further away from users than is ideal, which can affect the quality of service. Underground data centers, however, can be more strategically located, making it easier to place the facility near users to enhance response time and reduce delay.
Use sustainable energy
Many data centers are moving to sustainable energy sources to power their operations. Underground data centers are prime candidates for geothermal energy use, which involves using natural heat from under the Earth’s surface to power turbines that produce electricity. This method provides an on-site source of renewable and clean energy generation that decreases dependence on the grid and can be performed at any time of day.
Underground data centers can also reuse and recycle waste heat to warm nearby communities and buildings above ground.
Naturally cooling environment
Underground facilities avoid unexpected temperature fluctuations, like heat waves. Since the earth provides insulation and cooler temperatures at depth, underground data centers can expect stable, consistent and predictable temperatures. An underground environment can provide more granular control of cooling and better cooling efficiency, making it easier to maintain an optimal environment for data center equipment.
Consume less energy
With proper ventilation, the naturally cool environment of underground data centers enables less energy consumption than above-ground facilities. Lower energy use indicates energy savings, manageable operational costs and less strain on the grid.
Secure from physical threats
Data centers that store highly sensitive and valuable information might be the target of physical attacks and bad actors. Underground data centers provide a defensive advantage against such attacks, as no part of the structure is externally facing. Underground facilities can also avoid natural disasters like tornadoes, hurricanes, floods and wildfires.
Cons of underground data centers
Underground data centers do have some disadvantages, such as location restrictions, the need for advanced humidity control and limitations to expansion.
Location challenges
There are many considerations to analyze before choosing a location for an underground data center. Preexisting underground facilities, such as mines and bunkers, might not be readily available or are in remote locations that don’t offer a latency advantage. Other considerations include the structural integrity of the space, the distance from power grids and environmental safety concerns. Building near faults and volcanoes can trigger earthquakes, while building near water sources increases the risk of leaks and dampness.
Expensive to build
It can be more expensive to construct a new underground data center than an above-ground facility, especially without access to an underground cavern, pocket or other open environment. Higher construction costs are due to the complexity of building underground.
Construction requires drilling and creating a shell strong enough to withstand air and soil pressures. It also involves extensive insulation installation for waterproofing and reinforcements to maintain structural integrity in the face of environmental challenges, such as earthquakes and plate movement.
Proper ventilation and humidity concerns
While underground facilities might not consume as much energy for cooling as above-ground facilities, they typically consume more energy to maintain air quality and humidity levels. Heat and pollutants build up quickly in enclosed spaces, and high humidity levels endanger sensitive equipment. Intricate ventilation systems, humidity control systems and advanced monitoring tools are necessary to optimize the data center’s environment for continual operation and safety.
Difficult to expand
Expanding an underground data center is difficult and potentially dangerous. Extensive drilling and blasting might be necessary, threatening seismic activity or a cave-in. An expansion could have layout constraints, leading to workarounds that might not be ideal for mechanical and electrical equipment placement. This can affect the data center’s organization and efficiency.
From a time, cost and safety perspective, scaling an underground data center is often not feasible unless the facility was specifically designed for future expansions.
Limited access
Underground facilities typically have fewer access points than above-ground buildings. This makes it easier to secure the facilities, but it can also make it difficult for staff to enter or exit promptly. This is a particular concern in emergencies, but it can also pose logistical challenges for construction and maintenance.
Underground data centers in use today
Data centers have grown worldwide, but underground data centers are a mere fraction of the total. That said, some notable examples exist today.
Iron Mountain has underground data centers in Kansas City and Western Pennsylvania. These facilities are more than 200 feet below the surface, are surrounded by natural limestone, and use an underground lake for natural cooling. The year-round ambient temperature hovers around 52 degrees Fahrenheit, offering energy efficiency advantages.
Bluebird Fiber has an underground data center in Springfield, Mo., more than 85 feet below the surface in a limestone cavern. The facility enjoys a constant year-round temperature of 64 to 68 degrees Fahrenheit and a fixed humidity point, which reduces energy consumption and operational costs.
Data Journey has an underground bunker facility in Houston, Texas, with over 40,000 square feet of data center floor space. The Bunker, as it’s called, was originally built as a nuclear fallout shelter to house 300 people for an extended period. Its 3-foot-thick concrete walls create an ideal data center environment.
Green Mountain has a data center in Rennesøy, Norway, that features six halls, each with two-story concrete buildings built within a mountain. Built in 2013, the data center was repurposed from a former ammunition storage facility designed to withstand nuclear bombs and natural disasters. It’s located near a fjord for natural cooling and uses 100% renewable hydropower.
Underground data centers are not as prevalent as traditional facilities, but the trend is gaining momentum. While there are some considerations to weigh, the design and functionality of underground data centers are evolving rapidly, making it an area worth watching for those looking for more secure and sustainable locations to house their computing equipment.
Jacob Roundy is a freelance writer and editor with more than a decade of experience specializing in a variety of technology topics, such as data centers, business intelligence, AI/ML, climate change and sustainability. His writing focuses on demystifying tech, tracking trends in the industry, and providing practical guidance to IT leaders and administrators.
