PDF Publication Title:
Text from PDF Page: 008
TABLE 2: Techno-economic results for ideal-gas PTES and sCO2-PTES Performance Ideal-gas PTES sCO2-PTES Tmax °C 570.0 563.0 Tmin °C -53.7 20.0 Pressure ratio - 3.6 3.1 Maximum pressure bar 25.0 250.0 Hot storage fluid Molten salt Nitrate Nitrate Cold storage fluid - Methanol Water Work ratio - 3.5 11.0 Heat-to-work ratio - 4.5 8.5 Energy density kWhe/m3 16.3 7.6 Coefficient of performance - 1.3 1.2 Heat engine efficiency % 43.9 45.4 Round-trip efficiency % 58.2 52.6 Cap. Cost per energy discharged $/kWhe 311.3 ± 86.4 719.0 ± 303.8 LCOS $/kWhe 0.14 ± 0.03 0.27 ± 0.10 Design assumptions for a nominal PTES system are shown in Table 1, and corresponding results for an ideal-gas PTES and sCO2-PTES cycle are shown in Table 2. Note, that a high heat exchanger effectiveness is chosen. Using a high effectiveness is crucial to achieve reasonable round-trip efficiencies, and while this leads to higher capital costs, a better round-trip efficiency typically leads to a lower LCOS. The results in Table 2 indicate that ideal-gas PTES outperforms sCO2-PTES in terms of both efficiency and cost. The lower sCO2-PTES efficiencies are primarily the result of larger losses in the heat exchangers: the ideal gas has an almost constant heat capacity so that temperature differences in the heat exchangers are quite small. On the other hand, the variable heat capacity of sCO2 leads to pinch points and larger temperature differences in some parts of the heat exchanger, thereby leading to larger losses. The ideal-gas PTES has a larger temperature difference between the hot and cold storage. This has been shown to lead to higher efficiencies [2], as well as larger energy densities which therefore reduces the storage volume and the cost. The capital cost and LCOS of sCO2-PTES is nearly double the ideal-gas PTES values. This may be attributed to the lower energy density and the higher costs of developing new technologies for sCO2 power cycles. However, there may be some scope of cost reductions as these technologies are advanced and commercialized. On the other hand, ideal-gas PTES cycles are based on existing technologies such as gas turbines, and there may be more limited opportunities for cost reductions in these well-developed components. The costs in Table 2 account for the cost of all components in the PTES cycles and do not consider the additional value that is achieved by sharing several components (discharging turbomachinery, hot storage, recuperators) between the PTES and CSP systems. Further analysis is required to understand the full benefits of ‘generation-integrated electricity storage’. THE “TIME-SHIFTED” RECOMPRESSION SCO2 POWER CYCLE A second method of hybridizing PTES concepts sCO2 power cycles for CSP is presented in this section. Rather than using the heat pump to charge the high temperature molten salt storage, in this concept, the heat pump charges a lower temperature storage. 5 This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.PDF Image | Supercritical CO2 Heat Pumps Concentrating Solar Power
PDF Search Title:
Supercritical CO2 Heat Pumps Concentrating Solar PowerOriginal File Name Searched:
77955.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)