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Chapter 3

/kWh]

2005

Levelized Cost of Energy [UScent

30

28

26

24

22

20

18

16

CSP, USD2005

7,300

CSP, USD2005

6,650

CSP, USD2005

6,000

14

12 34

35

36

37

38

39

40

41 42 43 Capacity Factor[%]

/kWh]

2005

Levelized Cost of Energy [UScent

30

28

26

24

22

20

18

16

CSP, Discount Rate = 10% CSP, Discount Rate = 7% CSP, Discount Rate = 3%

14

12

34

35

36

37

38

39

40

41 42 43 Capacity Factor[%]

Figure 3.21 | Levelized cost of CSP electricity generation, 2009. Upper panel: Cost of CSP electricity generation as a function of capacity factor and investment cost1,3. Lower panel: Cost of CSP electricity generation as a function of capacity factor and discount rate2,3. Source: Annex III.

Notes: 1. Discount rate assumed to equal 7%. 2. Investment cost for CSP plant with six hours of thermal storage assumed at USD2005 6,650/kW. 3. Annual O&M cost assumed at USD2005 71/kW, lifetime at 25 years.

plots show the sensitivity of the LCOE of CSP plants with six hours of thermal storage with respect to investment cost (Figure 3.21, upper) and discount rates (Figure 3.21, lower) as a function of capacity factor.

The learning ratio for CSP, excluding the power block, is given as 10 ±5% by Neij (2008; IEA, 2010b). Other studies provide learning rates according to CSP components:Trieb et al. (2009b) give 10% for the solar field, 8% for storage, and 2% for the power block, whereas NEEDS (2009) and Viebahn et al. (2010) state 12% for the solar field, 12% for storage, and 5% for the power block.

Cost reductions for trough plants of the order of 30 to 40% within the next decade are considered achievable. Central-receiver technology is less

Direct Solar Energy

commercially mature than troughs and thus presents slightly higher invest- ment costs than troughs at the present time; however, cost reductions of 40 to 75% are predicted for central-receiver technology (IEA, 2010b).

The US DOE (2011) states its CSP goals for the USA in terms of USD/kWh, rather than USD/W, because the Solar Energy Technologies Program is designed to affect the LCOE and includes significant storage. The specific CSP goals are the following: 9 to 11 US cents2005/kWh by 2010; 6 to 8 US cents2005/kWh (with 6 hours of thermal storage) by 2015; and 5 to 6 US cents2005/kWh (with 12 to 17 hours of thermal storage) by 2020 (USD2005, assumed 2009 base). The EU is pursuing similar goals through a compre- hensive RD&D program.

3.8.5

Solar fuel production

Direct conversion of solar energy to fuel is not yet widely demonstrated or commercialized. Thermochemical cycles along with electrolysis of water are the most promising processes for ‘clean’ hydrogen production in the future. In a comparison study, both the hybrid-sulphur cycle and a metal-oxide-based cycle were operated by solar tower technology for multi-stage water splitting (Graf et al., 2008). The electricity required for the alkaline electrolysis was produced by a parabolic trough power plant. For each process, the investment, operating and hydrogen produc- tion costs were calculated on a 50-MWth scale. The study points out the market potential of sustainable hydrogen production using solar energy and thermochemical cycles compared to commercial electrolysis. A sen- sitivity analysis was done for three different cost scenarios: conservative, standard and optimistic (Table 3.6).

As a result, variation of the chosen parameters has the least impact on the hydrogen production costs of the hybrid-sulphur process, ranging from USD2005 4.4 to 6.4/kg (Graf et al., 2008). The main cost factor for electrolysis is the electricity: just the variation of electricity costs leads to hydrogen costs of between USD2005 2.4 to 7.7/kg.The highest range of hydrogen costs is obtained with the metal oxide-based process: USD2005 4.0 to 14.5/kg. The redox system has the largest impact on the costs for the metal oxide-based cycle. The high electrical energy demand for nitrogen recycling influences the result significantly.

A substitute natural gas can be produced by the combination of solar hydrogen and CO2 in a thermochemical synthesis at cost ranges from 12 to 14 US cents2005/kWhth with renewable power costs of 2 to 6 US cents2005/kWhe (Sterner, 2009). These costs depend highly on the opera- tion mode of the plant and can be reduced by improving efficiency and reducing electricity costs.

The weakness of current economic assessments is primarily related to the uncertainties in the viable efficiencies and investment costs of the various solar components due to their early stage of development and their economy of scale as well as the limited amount of available litera- ture data.

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