Parametric and Cost Comparison of Thermal Storage Technologies
Table AIV.1
Typical Parameters of Thermal Energy Storage Systems
| TES System | Capacity (kWh/t) | Power (MW) | Efficiency (%) | Storage Period (h, d, m) | Cost (€/kWh) |
| Sensible (hot water) | 10-50 | 0.001-10 | 50-90 | d/m | 0.1-10 |
| PCM | 50-150 | 0.001-1 | 75-90 | h/m | 10-50 |
| Chemical reactions | 120-250 | 0.01-1 | 75-100 | h/d | 8-100 |
Table AIV.2
Economic Viability of TES Systems as a Function of the Number of Storage Cycles Per Year
| TES type | Cycles Per Year | 5-Year Energy Savings (kWh) | 5-Year Economic Savings (€) | Investment Cost (€/kWh) |
| Seasonal storage | 1 | 500 | 25 | 0.25 |
| Daily storage | 300 | 150,000 | 7500 | 75 |
| Short-term storage (3 c/day) | 900 | 450,000 | 22,500 | 225 |
| Buffer storage (10 c/day) | 3000 | 1,500,000 | 75,000 | 750 |
Table AIV.3
State of Development, Barriers, and Main R&D Topics for Different TES Technologies
| Technology | Status (%) Market/R&D | Barriers | Main R&D Topics |
| Sensible Thermal Energy Storage | |||
| Hot water tanks (buffers) | 95/5 | Super insulation | |
| Large water tanks (seasonal) | 25/75 | System integration | Material tank, stratification |
| UTES | 25/75 | Regulation, high cost, low capacity | System integration |
| High temperature solids | 10/90 | Cost, low capacity | High temperature materials |
| High temperature liquids | 50/50 | Cost, temperature < 400 °C | Materials |
| Latent Thermal Energy Storage (PCM) | |||
| Cold storage (ice) | 90/10 | Low temperature | Ice production |
| Cold storage (other) | 75/25 | High cost | Materials (slurries) |
| Passive cooling (buildings) | 75/25 | High cost, performance | Materials (encapulation) |
| High temperature PCM (waste heat) | 0/100 | High cost, mat. stability | Materials (PCM containers) |
| Thermochemical Energy Storage | |||
| Adsorption TES | 5/95 | High cost, complexity | Materials and reactor design |
| Absorption TES | |||
| Other chemical reactions | |||
Table AIV.4
Estimated Cost of 3600 MWht Two-Tank/Thermocline TES System (Approximately 12 h of TES for 100-MWe Plant)
| Indirect Storage System | Direct Storage Systems | ||
| Component | Two-Tank | Two-Tank | Thermocline |
| Solar field HTF, type | Therminol | HitecXL | HitecXL |
| Outlet temperature (°C) | 391 (736 °F) | 450 (842 °F) | 450 (842 °F) |
| Storage fluid, type | Solar salt | HitecXL | HitecXL |
| Fluid cost, (k USD) | 51,200 | 71,200 | 26,000 |
| Filler material, type | NA | NA | Quartzite |
| Filler cost, (k USD) | 0 | 0 | 8700 |
| Tank(s), number | 3 Hot, 3 Cold | 2 Hot, 2 Cold | 2 Thermocline |
| Tank cost, (k USD) | 23,400 | 18,200 | 12,100 |
| Salt-to-oil heat exchanger, (k USD) | 9000 | 0 | 0 |
| Piping/solar field heat tracing | 0 | 10,600 | 10,600 |
| Total (k USD) | 91,900 | 108,900 | 62,000 |
| Specific cost (USD/kWht) | 26 | 33 | 19 |
| Development status | Early commercial | Prefeasibility study | Prefeasibility study |
Sources: Thermal Energy Storage Technology Brief, IEA-ETSAP and IRENA© Technology Brief E17, 2013 (www.etsap.org—www.irena.org); Assessment of thermal energy storage for parabolic trough solar power plants (http://www.nrel.gov/csp/troughnet/pdfs/kearney_tes_overview.pdf).
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