Heat-transfer fluids and heat pipes: Unit economics
Cheap to store, costly to carry far
What this tab covers What it costs to move a unit of energy this way: capital and operating costs, tariffs, utilisation and how it compares with the alternatives.Heat carriers are cheap to store but costly to move far. Molten salt storage cost about USD 26 to 40 per kWh of heat in 2020, but each lorry of stored heat carries only a few MWh.
Key costs
| Measure | Value | Note |
|---|---|---|
| Molten salt storage installed cost | 26.1 to 40 (2020); 21.8 to 25.8 expected by 2030 USD per kWh of heat4 | IRENA estimate (2020 report) |
| Sensible thermal storage cost | about 35, falling to about 25 by 2030 USD per kWh4 | IRENA, 2020 |
| Lorry deliveries needed for one college | about 364 a year (calculated: 910 MWh demand / 2.5 MWh per unit) trips per year10 | WärmeEngel, 16 km route |
| Demonstration funding | 1.5 million EUR10 | WärmeEngel mobile heat project, 2026 |
Where the money goes
| Item | Share or amount |
|---|---|
| Oil-to-salt heat exchanger in oil-based solar plants | significant, not quantified; avoided if salt is used as the field fluid2 |
| Thermal oil inventory | described as an immense cost in solar fields2 |
The cost structure explains where each carrier is used. Pipes and pumps dominate the cost of moving heat in fluids, so fluids stay inside a plant or town. Stores are cheap per kWh, so heat is stored where it is made and used later, rather than shipped. A trucked store competes with a district heating pipe only where demand is small and scattered: one 2.5 MWh unit needs a lorry trip, compared with a pipeline that runs all year.
Sources
- Molten salt suitable heat transfer fluid for concentrating collector fields solarthermalworld.org, 2021
- Innovation Outlook: Thermal Energy Storage IRENA, 2020
- Waste heat is transported to the customer by truck Bayern Innovativ, 2026