{"id":3771,"date":"2026-07-28T11:56:48","date_gmt":"2026-07-28T09:56:48","guid":{"rendered":"https:\/\/nature-o.net\/?p=3771"},"modified":"2026-07-28T11:56:49","modified_gmt":"2026-07-28T09:56:49","slug":"industrial-heat-pumps-how-cities-can-be-heated-with-waste-heat-from-data-centres-and-sewage","status":"publish","type":"post","link":"https:\/\/nature-o.net\/?p=3771","title":{"rendered":"Industrial Heat Pumps: How Cities Can Be Heated With Waste Heat From Data Centres and Sewage"},"content":{"rendered":"\n<p>Cities continuously produce enormous quantities of low-temperature heat. Servers release it while processing data, wastewater carries it away from showers and washing machines, and industrial cooling systems discharge it into the environment.<\/p>\n\n\n\n<p>Most of this energy is too cool to enter a conventional district-heating network directly. Industrial heat pumps solve that problem by raising low-grade heat to a temperature useful for heating buildings and producing hot water.<\/p>\n\n\n\n<p><strong>Instead of generating all urban heat from fuel, cities can recover energy that has already been paid for once.<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">What Is an Industrial Heat Pump?<\/h3>\n\n\n\n<p>An industrial heat pump is a large-scale system that transfers heat from a cooler source to a warmer destination.<\/p>\n\n\n\n<p>It operates according to the same basic principle as a refrigerator. A refrigerator moves heat from its cold interior into the surrounding room. A heat pump redirects that process so the useful output is the heat delivered to a building, industrial process, or district-heating network.<\/p>\n\n\n\n<p>The European Commission describes modern heat pumps as a mature technology that can typically deliver three to five units of heat for each unit of electricity consumed. Actual performance depends on the source temperature, required output temperature, equipment design, weather, and operating conditions.<\/p>\n\n\n\n<p>Large heat pumps can use energy from:<\/p>\n\n\n\n<ul>\n<li>Treated sewage and wastewater<\/li>\n\n\n\n<li>Data-centre cooling systems<\/li>\n\n\n\n<li>Industrial processes<\/li>\n\n\n\n<li>District-cooling networks<\/li>\n\n\n\n<li>Rivers, lakes, and seawater<\/li>\n\n\n\n<li>Geothermal water<\/li>\n\n\n\n<li>Underground mines<\/li>\n\n\n\n<li>Outdoor air<\/li>\n\n\n\n<li>Refrigeration plants<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">How a Heat Pump Raises the Temperature<\/h3>\n\n\n\n<p>A heat pump contains a refrigerant circulating through a closed system.<\/p>\n\n\n\n<p>First, the refrigerant absorbs low-temperature heat and evaporates. A compressor then increases the pressure of the refrigerant vapour, raising its temperature.<\/p>\n\n\n\n<p>The hot refrigerant passes through a heat exchanger and releases energy into the district-heating water. It then loses pressure, cools, and begins the cycle again.<\/p>\n\n\n\n<p>The compressor requires electricity, but most of the delivered heat comes from the surrounding waste-heat source rather than from the electricity itself.<\/p>\n\n\n\n<p>This relationship is expressed through the <strong>coefficient of performance<\/strong>, or COP. A COP of 4 means that one unit of electricity enables the system to supply approximately four units of heat.<\/p>\n\n\n\n<p><strong>The smaller the temperature difference between the heat source and the required heating-water temperature, the more efficiently the heat pump can operate.<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Why Data Centres Are Valuable Heat Sources<\/h3>\n\n\n\n<p>Almost all electricity consumed by computer servers eventually becomes heat.<\/p>\n\n\n\n<p>Data centres must remove this heat continuously to prevent equipment from overheating. Conventional cooling systems may release it into outdoor air through cooling towers, dry coolers, or ventilation systems.<\/p>\n\n\n\n<p>A heat-recovery system instead captures energy from warm water or air leaving the servers. Industrial heat pumps then raise its temperature before feeding it into a district-heating network.<\/p>\n\n\n\n<p>The International Energy Agency estimates that around 70\u201380% of data-centre heat may be recoverable with heat pumps, although the practical amount depends on cooling design, temperature, distance from heat consumers, and network conditions.<\/p>\n\n\n\n<p>Data centres have several advantages as heat suppliers:<\/p>\n\n\n\n<ul>\n<li>They operate throughout the year.<\/li>\n\n\n\n<li>Their heat production is relatively predictable.<\/li>\n\n\n\n<li>Large facilities concentrate substantial energy in one location.<\/li>\n\n\n\n<li>Modern liquid-cooling systems can provide warmer source water than traditional air cooling.<\/li>\n\n\n\n<li>Heat recovery can reduce the need for separate cooling equipment.<\/li>\n<\/ul>\n\n\n\n<p>Helen and Telia have been supplying recovered heat from a Helsinki data centre to the city\u2019s district-heating system since 2023.<\/p>\n\n\n\n<p>Fortum\u2019s cooperation with Microsoft in Finland is designed to recover heat from major data-centre sites and distribute it to homes, services, and businesses in the Helsinki metropolitan region. Fortum expects the full project eventually to cover around 40% of heating demand among approximately 250,000 district-heating users in its network area.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">How Cities Extract Heat From Sewage<\/h3>\n\n\n\n<p>Wastewater leaving homes is warmer than the surrounding ground for much of the year.<\/p>\n\n\n\n<p>Showers, washing machines, dishwashers, kitchens, commercial buildings, and industrial facilities continually add heat to the sewer system. Even after treatment, wastewater often contains enough thermal energy for heat-pump recovery.<\/p>\n\n\n\n<p>A sewage-based system usually draws heat through heat exchangers installed at a treatment plant, major sewer, pumping station, or treated-water outlet.<\/p>\n\n\n\n<p>The wastewater itself normally remains separated from the clean water circulating through the heat pump and district-heating network.<\/p>\n\n\n\n<p>This arrangement offers several benefits:<\/p>\n\n\n\n<ul>\n<li>Sewage flows are available throughout the year.<\/li>\n\n\n\n<li>Temperature is often more stable than outdoor air temperature.<\/li>\n\n\n\n<li>Treatment plants can provide large, concentrated water flows.<\/li>\n\n\n\n<li>The same installation may produce district cooling.<\/li>\n\n\n\n<li>The energy source exists close to many urban consumers.<\/li>\n<\/ul>\n\n\n\n<p>Helsinki\u2019s Katri Vala facility produces district heating and cooling using purified wastewater and other recovered heat. Helen describes it as one of the world\u2019s largest plants of its kind.<\/p>\n\n\n\n<p>The newer Eiranranta plant is designed to extract further energy from exceptionally cool wastewater that has already passed through the Katri Vala process. Its heat pumps provide about 90 megawatts of district-heating capacity and are expected to produce roughly 300 gigawatt-hours of heat annually.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Why District Heating Makes the Idea Practical<\/h3>\n\n\n\n<p>A large source of waste heat is useful only when the energy can reach customers.<\/p>\n\n\n\n<p>District heating provides this connection through insulated pipes carrying hot water to homes, offices, hospitals, schools, shops, and industrial buildings.<\/p>\n\n\n\n<p>A central heat pump can therefore serve thousands of properties without every building installing its own large system.<\/p>\n\n\n\n<p>District networks can also combine several energy sources. During mild weather, waste heat and heat pumps may provide most of the demand. During very cold periods, thermal storage, electric boilers, biomass units, geothermal systems, or other peak-load equipment can provide additional capacity.<\/p>\n\n\n\n<p>The IEA notes that district-heating systems can use low-temperature heat sources below 45\u00b0C, particularly when networks operate at reduced temperatures that limit losses and improve heat-pump efficiency.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">What Makes a Project Economically Successful?<\/h3>\n\n\n\n<p>The presence of warm water does not automatically make heat recovery profitable.<\/p>\n\n\n\n<p>The most important factor is distance. Building several kilometres of large insulated pipes can cost more than the recovered energy is worth.<\/p>\n\n\n\n<p>A strong project usually requires:<\/p>\n\n\n\n<ul>\n<li>A large and stable heat source<\/li>\n\n\n\n<li>Nearby year-round heating demand<\/li>\n\n\n\n<li>A suitable district-heating network<\/li>\n\n\n\n<li>Affordable electricity<\/li>\n\n\n\n<li>Predictable long-term contracts<\/li>\n\n\n\n<li>Space for compressors, exchangers, pumps, and storage<\/li>\n\n\n\n<li>Compatible source and network temperatures<\/li>\n<\/ul>\n\n\n\n<p>Electricity prices strongly influence operating costs. Industrial heat pumps are especially attractive when they can run during periods of abundant low-carbon or inexpensive power.<\/p>\n\n\n\n<p>Large hot-water tanks, underground caverns, or other thermal-storage systems can separate heat production from immediate demand. The heat pump can run when electricity conditions are favourable and store energy for later use.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">The Main Technical Challenges<\/h3>\n\n\n\n<p>Wastewater contains grease, fibers, sand, biological material, and other contaminants that can foul heat exchangers. Equipment therefore requires filtration, cleaning systems, corrosion-resistant materials, and regular maintenance.<\/p>\n\n\n\n<p>Data-centre projects face different challenges. Heat may be produced at only 25\u201335\u00b0C, while an older district-heating network may require much hotter water during winter.<\/p>\n\n\n\n<p>Raising the temperature through a large difference reduces efficiency and increases electricity consumption. Newer low-temperature networks are easier to integrate with waste heat.<\/p>\n\n\n\n<p>Refrigerant choice is also important. Industrial systems may use ammonia, carbon dioxide, hydrocarbons, or synthetic refrigerants depending on temperature requirements, safety rules, environmental impact, and equipment design.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Does Waste Heat Make Heating Carbon-Free?<\/h3>\n\n\n\n<p>Not automatically.<\/p>\n\n\n\n<p>A heat pump produces no combustion emissions at its installation, but its climate impact depends heavily on the electricity used by the compressor.<\/p>\n\n\n\n<p>When powered by low-carbon electricity, recovered heat can have very low operational emissions. When the grid depends heavily on coal or gas, the emissions advantage becomes smaller.<\/p>\n\n\n\n<p>The correct comparison should also include backup boilers, network losses, construction, refrigerant leakage, and the alternative use of the electricity.<\/p>\n\n\n\n<p>Waste-heat recovery does not make a data centre itself energy-free. The servers still consume electricity. It simply prevents a useful by-product from being discarded.<\/p>\n\n\n\n<p><strong>The greatest benefit comes from combining efficient data centres, low-carbon electricity, modern district heating, thermal storage, and high-performance heat pumps.<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Expert Perspective<\/h3>\n\n\n\n<p>The International Energy Agency describes urban and industrial waste heat as a significant but underused resource. It stresses that the technology for capturing it is generally straightforward, while successful deployment depends primarily on local temperature levels, proximity to demand, network access, and connection costs.<\/p>\n\n\n\n<p>European energy policy is increasingly encouraging the integration of renewable and recovered heat into district-heating systems. The revised EU Energy Efficiency Directive gradually strengthens the requirements for efficient networks and promotes a larger role for renewable energy and waste heat.<\/p>\n\n\n\n<p>In 2026, European industry associations also agreed to develop a cooperation model linking data-centre operators, energy companies, and public authorities, specifically including the reuse of data-centre heat in district systems.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Interesting Facts<\/h3>\n\n\n\n<ul>\n<li>Nearly all electricity used by servers eventually becomes heat.<\/li>\n\n\n\n<li>Sewage can remain a useful heat source even after wastewater treatment.<\/li>\n\n\n\n<li>The same industrial heat pump may produce heating and cooling simultaneously.<\/li>\n\n\n\n<li>Warmer source water usually improves heat-pump efficiency.<\/li>\n\n\n\n<li>Data centres provide heat throughout summer, when district-heating demand is lower, making thermal storage especially useful.<\/li>\n\n\n\n<li>Older high-temperature district networks are harder to supply with low-grade waste heat.<\/li>\n\n\n\n<li>Some heat-pump plants are located underground to save urban space and reduce noise.<\/li>\n\n\n\n<li>A large facility can supply tens or hundreds of megawatts of heat.<\/li>\n\n\n\n<li>Wastewater temperatures are usually more stable than outdoor air temperatures.<\/li>\n\n\n\n<li>District-cooling systems can capture heat from office buildings and transfer it into heating networks.<\/li>\n\n\n\n<li>The IEA identifies data centres, wastewater plants, and industrial facilities as important future sources of low-temperature urban heat.<\/li>\n\n\n\n<li>Waste-heat projects can reduce exposure to fluctuating fuel prices because their main operating input is electricity.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Glossary<\/h3>\n\n\n\n<ul>\n<li><strong>Industrial Heat Pump<\/strong> \u2014 A large system that moves and upgrades heat for industrial processes or district heating.<\/li>\n\n\n\n<li><strong>Waste Heat<\/strong> \u2014 Thermal energy produced by another activity that would otherwise be discarded.<\/li>\n\n\n\n<li><strong>Low-Grade Heat<\/strong> \u2014 Heat available at a relatively low temperature.<\/li>\n\n\n\n<li><strong>District Heating<\/strong> \u2014 A network that distributes centrally produced hot water or steam to multiple buildings.<\/li>\n\n\n\n<li><strong>Refrigerant<\/strong> \u2014 A fluid that absorbs and releases heat while changing pressure or physical state.<\/li>\n\n\n\n<li><strong>Evaporator<\/strong> \u2014 The heat exchanger where the refrigerant absorbs energy and evaporates.<\/li>\n\n\n\n<li><strong>Compressor<\/strong> \u2014 A device that increases refrigerant pressure and temperature.<\/li>\n\n\n\n<li><strong>Condenser<\/strong> \u2014 The heat exchanger where hot refrigerant releases useful heat.<\/li>\n\n\n\n<li><strong>Coefficient of Performance<\/strong> \u2014 The ratio of useful heat supplied to electricity consumed by a heat pump.<\/li>\n\n\n\n<li><strong>Heat Exchanger<\/strong> \u2014 Equipment that transfers heat between separate fluids without mixing them.<\/li>\n\n\n\n<li><strong>Data Centre<\/strong> \u2014 A facility containing servers and communication equipment for processing and storing digital information.<\/li>\n\n\n\n<li><strong>Liquid Cooling<\/strong> \u2014 A server-cooling method that removes heat using a circulating liquid.<\/li>\n\n\n\n<li><strong>Wastewater<\/strong> \u2014 Water that has been used by homes, businesses, or industry and requires treatment.<\/li>\n\n\n\n<li><strong>Thermal Storage<\/strong> \u2014 Storage of heat or cold for later use.<\/li>\n\n\n\n<li><strong>Peak Load<\/strong> \u2014 The highest level of heating demand during a particular period.<\/li>\n\n\n\n<li><strong>Network Temperature<\/strong> \u2014 The temperature at which water circulates through a district-heating system.<\/li>\n\n\n\n<li><strong>Fouling<\/strong> \u2014 Accumulation of unwanted material on equipment surfaces, reducing heat transfer.<\/li>\n\n\n\n<li><strong>Refrigerant Leakage<\/strong> \u2014 Accidental release of refrigerant, which may create safety or environmental impacts.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Cities continuously produce enormous quantities of low-temperature heat. Servers release it while processing data, wastewater carries it away from showers and washing machines, and industrial cooling systems discharge it into&hellip;<\/p>\n","protected":false},"author":2,"featured_media":3772,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_sitemap_exclude":false,"_sitemap_priority":"","_sitemap_frequency":"","footnotes":""},"categories":[46,60,47],"tags":[],"_links":{"self":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/posts\/3771"}],"collection":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3771"}],"version-history":[{"count":1,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/posts\/3771\/revisions"}],"predecessor-version":[{"id":3773,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/posts\/3771\/revisions\/3773"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=\/wp\/v2\/media\/3772"}],"wp:attachment":[{"href":"https:\/\/nature-o.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3771"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3771"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nature-o.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3771"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}