Data centers -- and the fleets of hot, always-on and power-hungry servers within them -- produce a lot of heat. Admins are constantly working to ensure equipment doesn't overheat or break down due to nonoptimal heat and humidity levels, but some data centers are reusing their heat, instead of dispelling it.
Heat from data centers can contribute to climate change, but data centers can cut down on heat or reuse it in clever, nonharmful ways. Many organizations are reusing the heat generated by their data centers to heat other facilities, homes in surrounding communities and even fish farms.
Benefits of reusing data center heat
A significant amount of the energy data centers use is to maintain temperatures. With data centers facing pressure from governments and organizations, like the International Energy Agency, to decarbonize and lower energy consumption to protect the planet, reusing data center heat might be part of the answer.
From an environmental standpoint, reusing waste heat, such as by rerouting the heat to warm nearby buildings, can help reduce energy use from other sources, like a nearby district heating system that uses a gas boiler. From an economic perspective, recycling heat can lead to superior energy efficiency, which can create significant cost savings over the long term, especially in the face of rising energy costs.
In addition, governments, like those in France and Denmark, may require new data centers to conduct feasibility studies for using excess heat to benefit local communities in order to obtain building permits. It is important for organizations to get ahead of these requirements sooner rather than later since it may also come with tax incentives and may help avoid penalties, fines and time spent navigating red tape.
Innovative ways to reuse data center heat
Instead of funneling hot air back into the atmosphere or using energy to cool it, many data centers are exploring creative ways to reuse heat, including the following:
- Heating buildings and homes in the community. Organizations often build data centers near energy grids that power nearby cities. Those cities also have heating requirements and district heating systems. Organizations could use the heat from data centers to heat up and route water into district heating systems and into homes and buildings with radiators.
- Using heat for agricultural purposes. Greenhouses require consistent heating year-round, unlike district heating systems that may have fluctuations in heat needs depending on the season. Using similar heated-water pipes, data centers could be that source of heat. This would be a good alternative to geothermal energy and biofermentation for horticulturalists, as it has a minimal impact on soil and the environment.
- Heating water for fish farms and swimming pools. Many public swimming pools rely on gas boilers to keep the water warm for swimmers, and heat from data center equipment could warm both swimming pools and other pools, like those used to incubate fish and grow vegetation.
- Manufacturing wood pellets. Wood pellets are a low-carbon alternative to coal. These pellets are burned for heat, but to achieve the optimal level of quality for burning, they need to be dried with hot air first to reduce their moisture content. Data center heat could be rerouted to provide this hot air.
Real-world examples of data center heat recovery
Let's explore some practical use cases showcasing how some organizations with data centers reuse heat.
Meta built a data center in Odense, Denmark, designed with heat recovery and 100% renewable energy in mind. The goal of this facility is to recover and donate 100,000 megawatt hours of energy annually from its servers. The heat gets rerouted to warm a local hospital and other buildings in the surrounding community via a district heating system that captures heat from the air and directs it across copper coils to heat water. It then sends the hot water to homes and buildings that use radiators for heat.
Apple has plans to expand its data center in Viborg, Denmark, to redirect heat to warm water sent to the local power station and its district heating system. This facility is powered by wind turbines, and all surplus energy goes back into the Danish grid. The expansion would involve building new infrastructure to capture even more excess heat energy for the city.
Amazon's Tallaght data center in Dublin draws heat from servers into an air-handling unit that recycles the heat to warm water. The water gets passed to an energy center outside the warehouse, where heat pumps condense it to even higher temperatures. The facility saves an estimated 1,400 tons of carbon dioxide emissions every year and heats more than 505,000 square feet of local public buildings, 32,000 square feet of commercial buildings and 135 apartments.
EcoDataCenter has detailed plans to expand its Falun, Sweden, facility to use excess heat in wood pellet production. This data center has underground pipes that carry hot water to a combined heat- and power-generating plant next door that also produces wood pellets. To remove moisture from the wood pellets, the plant lays out sawdust on 20 foot-wide mats and blows hot air over it. In place of propane gas boilers, EcoDataCenter's facility could provide 10 megawatts of waste heat to help in this drying process.
Blockheating is building technology that enables data centers to reuse waste heat to warm greenhouses. In a greenhouse, a 200-kilowatt data center can potentially heat 1 hectare, or 2.47 acres, which could support growing more than 88,000 pounds of tomatoes per month without any additional energy. The technology uses a special radiator that cools water to maintain data center temperatures. When the water is warmed, it flows to a greenhouse via a system of connected pipes.
Challenges to data center heat reuse
Reusing heat in the data center isn't as easy as flipping a switch or turning a dial on the thermostat. The primary roadblocks to reusing heat are as follows:
- Infrastructure startup costs. Many heat reuse projects operate on a huge scale, and setting up this infrastructure can require heavy capital investment. While some of this investment could come from government entities or through tax credits, that likely won't cover all the upfront expenses.
Complicating this fact is how new the technology is -- from expensive, high-end heat exchangers to new equipment that is scarce and hard to scale. The cost of heat reuse technology will likely come down in the near term as this becomes a focus area for data centers globally, and the long-term cost savings should offset the upfront investment.
- Heat and energy lost during transmission. Data centers already use a variety of tools to monitor airflow, cooling, humidity and temperature. They need even more visibility into how much heat is being transferred from one place to another, however. During this process, both heat and energy can be lost.
This requires paying close attention to energy usage effectiveness to optimize heat cycling, liquid cooling and airflow dynamics. This can ensure both sides of the heat equation are balanced: The data center environment is safe for all equipment, and the recycled heat is effective wherever it is redirected.
Loss of heat can also mean waste if it's not hot enough to power a heating system. Organizations may need to install heat pumps to further warm the air to usable levels, as warm air is difficult to store and transport, especially over a large surface area. Using pipes is often the best way to overcome this.
- Location. A data center's location may limit its ability to deploy some of these creative options. For example, if the data center is too far away from users to benefit from the waste heat or if there aren't enough users to consume all the heat being recycled, it simply may not be viable. As a result, it's vital to take heat reuse into consideration when standing up a new data center.
As data center demand continues to rise, reusing heat is key to building more efficient and more sustainable infrastructure, reducing the impact energy use has on the planet as a whole.