The biggest heat pumps

Currency typo in article

• Commenters quickly spot and discuss a BBC typo: €200m was shown as $2.3m instead of ~$235m; it was later corrected.
• Some note that with inflation the incorrect figure might accidentally become true in future.

Why river water is useful for heat pumps

• The Rhine isn’t “warm” in absolute terms, just warmer than winter air and well above absolute zero, so usable as a heat source.
• Water’s high thermal mass and constant flow make it more efficient than air and less limited than ground-source systems, which can over-chill local soil.
• River water changes temperature more slowly than air, making it a good buffer for winter peaks and even a “cold source” in summer.

Thermodynamics and environmental concerns

• Heat pumps move heat from colder water to warmer buildings, analogous to pumping water uphill.
• Discussion about how far below 0°C moving or pressurized water can go before freezing, and design issues like avoiding ice buildup or “icebergs” at outlets.
• Concerns that fish removal and other interventions might have hidden ecological downsides, even if modeled river temperature change (<0.1°C) seems negligible.

Heat pump economics and regional adoption

• Large heat pumps costing ~€500k/MW are noted as roughly in line with domestic units on a per‑kW basis.
• Nordics report very high adoption: most houses use heat pumps; most apartments use district heating, often driven by big heat pumps.
• Reasons cited: cheap or relatively cheaper electricity, weak gas grid, long familiarity with the tech.
• In Germany, heat pumps have become politicized; some media pushed the narrative they “can’t work” in local winters.
• Commenters contrast Norway/Sweden/Finland’s wealth and energy mix with countries where gas is cheap and electricity dear (e.g. UK, parts of Germany), making heat pumps less financially attractive.

Retrofit challenges and building stock

• Retrofitting older homes can require new radiators, thicker pipes, higher insulation, and sometimes electrical upgrades; costs quoted range from “no‑brainer vs oil” to €40k in Germany.
• Some argue new builds should be mandated to use heat pumps to avoid retrofit pain.
• UK/Ireland anecdotes: varied building quality, single glazing in older stock, some external waste piping; improved standards in newer homes.

Cold‑climate performance and skepticism

• US Northeast commenter says local contractors discourage heat pumps and claims they lose efficacy below ~‑4°C/25°F.
• Nordic responses: many systems are ground‑source; modern cold‑climate air‑source units maintain high efficiency far below freezing when sized correctly.
• Clarification that COP can fall toward 1, but never below pure resistive heating; worst case, it behaves like an electric heater.

District heating: popularity and drawbacks

• District heating is dominant in the Nordics and used with large heat pumps, waste heat, and in some nuclear histories.
• In the Netherlands, district heating is viewed more skeptically: monopoly supplier, mandatory minimum purchases, and weak competitive or maintenance incentives.

Costs, regulation, and DIY / small systems

• Air‑to‑air mini‑splits are presented as cheap and effective in many places; several people describe DIY installs with basic tools and vacuum pumps.
• Others mention “push‑through” alternatives to vacuuming that are simpler but don’t test for leaks.
• German commenters highlight high “soft costs”: overregulated metering cabinets, mandatory smart‑meter infrastructure, and local utility standards driving multi‑thousand‑euro upgrades.

Comparison with nuclear and energy policy

• Some compare 162 MWth of heat pump capacity (~€235m) to multi‑billion‑euro, gigawatt‑scale nuclear plants, arguing nuclear plus resistive heating would be several times more expensive per unit of delivered heat.
• Others counter that nuclear generates both electricity and thermal energy and can supply district heat directly if sited close enough.
• Debate over Germany’s nuclear phase‑out: critics say wasteful given past capacity and potential to feed district heating; defenders point to past reliance on Russian fuel, though others argue uranium supply is diversified and cheap.
• Broader pessimistic/humorous asides about Europe’s long‑term energy choices and over‑reliance on fossil fuels.

Other large installations and waste heat use

• Examples from Vienna, Stockholm, and Helsinki: multi‑hundred‑MW heat pump plants using river water or treated sewage; some also feed district cooling.
• Commenters discuss data centers and AI facilities as potential future district heating sources, though no concrete projects are cited.

Misc technical ideas

• Curiosity about using solid‑state heat pipes instead of pumped water, especially for geothermal.
• Notes about nuclear plants and enrichment facilities historically providing low‑grade waste heat for greenhouses and similar uses.