Concentrating Solar Power Plant Investment Engineering Essay

The despatch chances provided by storage-enhanced Concentrating Solar Power workss have direct deductions on the investing determinations as non merely nameplate capacity but besides the storage capacity and the solar multiple drama a important function for the viability of the works investing. By incorporating extra proficient facets and operation schemes, this paper extends the optimisation theoretical account proposed by Madaeni et Al, How Thermal Energy Storage Enhances the Economic Viability of Concentrating Solar Power.

Subsequently, the economic value of CSP storage is analyzed via energy mold of a Spanish works location under the several sweeping market monetary values every bit good as the local feed-in duty. The analysis shows that investing inducements for CSP workss with storage demand to suitably account for the mutuality between the monetary value inducements and the works runing scheme. As the ensuing gross features influence the optimum size of solar field and storage differing operating schemes besides give rise to differing optimum works layouts. Most notable, the current Spanish support strategy offers merely limited inducements for larger thermic storage capacity.

Cardinal words:

Concentrated solar power

Storage operation

Optimization theoretical account

Research Highlight:

Dispatch chances of CSP have direct deductions on both investing and operational determinations

Valuation attack with a individual assorted whole number maximization job

Profitableness of CSP workss under the premium feed-in duty in Spain was assessed

Layout determination and storage size are influenced by wage strategy

Discuss alternate wage strategies for “ dispatchable ” RE engineerings

Introduction

Increasing portions of electricity coevals from renewables in European states raise new proficient and economic inquiries about the operation and rating of engineerings in these new energy systems. Storage solutions are one cardinal factor for the integrating of fluctuating coevals of air current and solar engineerings ( Acre, 2011, Denholm and Hand, 2011, Sioshansi et al. , 2012 ) . Among the new coevals engineerings Concentrating Solar Power ( CSP ) has the advantage of bring forthing thermic energy that can be stored in thermic energy storages ( TES ) . Using this storage during hours without radiation offers the possibility to supply dispatchable electricity.

In Europe merely Mediterranean states have a sufficiently high direct radiation potency for CSP works operation with most of the CSP undertakings being based in Spain. By spring 2012, Spain had installed a entire CSP coevals capacity of about 1400 MW. This makes Spain by far Europe ‘s largest market for CSP. Therefore, this analysis focuses on the Spanish electricity market. However, the theoretical account can easy be adapted to other electricity markets like Italy or North Africa. In future ace grid scenarios one could even see Northern demand market locations like Germany that could be supplied through electricity trading. The first commercial CSP works with storage Andasol One ( 50 MW extremum end product, 7.5 hours of thermic storage ) was commissioned at the terminal of 2008 stopping point to the metropolis Guadix in Andalusia. Today, about half of the Spanish CSP workss are equipped with thermic storage. Current programs indicate that by 2020 a entire CSP capacity of over 5000 MW will be connected to the grid. A major ground behind this development is the execution of a favourable regulative support strategy for CSP workss through a feed-in duty ( Griffiths ) . This has created a stable and changeless market environment since 2007. The agreements of this strategy give investors inducements to put in CSP workss including thermic energy storage.

A pronounced difference between authoritative renewable energy ( RE ) engineerings ( wind turbines, photovoltaic ( PV ) installings ) and CSP workss with storage is the type of operation. While the former are “ inactive ” ( non-dispatchable ) systems offering no control opportunities ( except for coevals casting ) , the latter are “ active ” ( dispatchable ) in the sense that operators can intentionally maneuver energy flows within the works and entree energy stored in the thermic storage. Given the limited control construction of non-dispatchable or inactive systems, investing determinations are a simple inquiry of efficient graduated table, energy output and entire capacity. Consequently, set uping investing inducements for these workss merely requires puting a wage strategy for each unit of capacity provided, severally for each unit of energy generated over a given clip skyline. On the other manus, the control chances provided by storage-enhanced CSP workss have direct deductions on the investing determinations as non merely nameplate capacity but besides mutualities between turbine capacity, solar field size and thermic energy storage play a important function for the viability of the works investing.

The current legal model and support mechanism in European states are extremely act uponing design and operation of CSP power workss. In the US, a quota system and revenue enhancement decreases yield different effects on CSP investings. Due to higher electricity demand during daylight hours, CSP undertakings are frequently constructed without thermic storage, e.g. , Nevada One ( Nevada ) or Martin ( Florida ) .

In Southern Europe, some states with high direct solar irradiance ( Spain, Portugal, Italy ) have decided to back up CSP power workss through feed-in duties. One of import end of the energy contrivers was to back up CSP power workss with storage to supply a market environment for flexible despatch power workss based on solar power. In Portugal, little CSP workss ( & lt ; 10 MW ) can run under a fixed FIT of 260-270 Euro/MWh which is seen as a support for little pilot power workss. In Italy, the FIT for CSP ranges from 220 to 280 Euro/MWh reflecting the usage of natural gas back-up in the CSP works ( CSPtoday, 2011 ) . Feed-in duties in these states do non match the production of the CSP with the electricity market monetary value but instead offer a fixed duty for each kWh generated. Under this support strategy, thermic storage is merely included to increase overall production per installed turbine capacity.

In Spain, the regulative model of the RD 661/2007 established a FIT for CSP investings. The RD 661/2007 had the largest impact on market creative activity of CSP in Europe due to its stable conditions cut downing investor hazard for renewable energy engineerings ( Ciarreta et al, 2011 ) . The regulative organic structure offers two different FIT options for CSP workss: a fixed and a premium FIT ( P-FIT ) . Other coevals engineerings like air current can use for similar premium FIT but with different wage. Schallenberg ( 2012 ) reports a strong addition of undertakings using for premium FIT over all engineerings, e.g. 96 % of all air current undertakings and all CSP undertakings opted for the premium FIT in 2009. The standard FIT, similar to the 1s offered in Portugal and Italy, guarantees a fixed rate of I± = 270 a‚¬/MWh over 25 old ages for each produced kWh ( I•t, electricity produced in clip T over clip period T ) . The 2nd option uses the current pool monetary value platinum from the Spanish electricity exchange plus a premium of I±p = 254 a‚¬/MWh. Entire wage is capped at = 334 a‚¬/MWh. These FITs were established in 2007 and can be formalized as follows:

The gross from a fixed FIT is lower than the P-FIT if the market monetary value is above 16 a‚¬/MWh ( see Figure 1 ) . The P-FIT therefore encourages a preferable supply from CSP power workss during times of high electricity pool monetary values ( Couture 2009 ) .

Figure: Two options of CSP feed-in duty in Spain: A fixed and a premium duty

Quantitative analyses of the P-FIT in the literature have been limited. P-FIT is regarded as more hazardous for investors and therefore may take to negative consequences for market growing of RE engineerings ( Klein et al. , 2008 ) . Gonzales ( 2008 ) highlights the minimisation of windfall net incomes with the execution of a cap monetary value. From an economic point of position, it has to be assumed that non-dispatchable coevals engineerings like air current and PV opt for the premium duty merely in instance of an expected higher mean wage. On the other manus, dispatchable coevals engineering can be operated in conformity with the P-FIT. Therefore, the rating of dispatchable generator investings needs to account for the dependence between operational picks and the wage strategy.

This paper links an optimisation theoretical account for the investing determination of the works layout and the operations scheme of CSP workss with an analysis of the influence of different duties on these picks. Section 2 reviews the related work on economic analysis of CSP engineering with storage. The optimisation theoretical account for investing and operation is presented in Section 3. Subsequently, storage operation and economic rating are carried in the context of a Spanish instance survey utilizing comparable layout and cost premises of the Andasol workss. In Section 5, different wages scenarios for CSP workss are analyzed to exemplify their consequence on both operation and investing determinations. The concluding subdivision concludes and provides an mentality on future research chances.

Concentrated solar power workss

Unlike PV solar workss which rely on the photoelectric consequence, CSP power workss convert the energy of direct solar radiation into electric power via a thermic procedure. In the solar field, solar radiation is concentrated utilizing brooding optics and captured in a focal point. Focused radiation is absorbed by receiving system tubings which transport the thermic energy through a piping system to the cardinal power block. Here, thermic energy is converted to electricity by agencies of a heat engine ( turbine ) driving an electric generator connected to the electrical grid. The system can be coupled with thermic storage armored combat vehicles via heat money changers. These storage armored combat vehicles can hive away thermic energy for several hours or yearss.

By and large, CSP storage workss are operated by direct usage of thermic power from the solar field in the turbine. Surplus thermic energy can be stored in the thermic armored combat vehicles and is discharged from the storage at a ulterior clip, e.g. , after sunset. Relloso and Delgado ( 2010 ) depict the proficient experiences with commissioning and operation of the first CSP storage works ( Andasol1 ) . As most of the CSP workss in Spain are based on parabolic trough engineering, this engineering is besides assessed in this paper. Technical layout and design of the power works can be optimized along many different parametric quantities like stuff and constituent pick, works size, procedure temperatures, operation manners or force per unit area degrees ( see Morin, 2011 ) . Significant research has been done to increase the efficiency and the energy end product of these workss and to cut down building costs.

This paper focuses on the optimum pick of two major constituents in relation to a fixed turbine size of 100 MW: the solar field size and the storage capacity. In Spain, the CSP workss are typically constructed as 50 MW workss due to a cap in the national support strategy which does non let larger turbine sizes. The solar field size ( aperture country of the used mirrors and receiving systems ) determines the sum of captured solar energy from the Sun. It is characterized comparative to the turbine size via the solar multiple ( SM ) , see Isquierdo et Al. ( 2010 ) . A solar multiple of 1 offers plenty peak energy to run the turbine with full capacity on a typical solstice twenty-four hours at midday ( Montes et al. , 2009 ) . The storage armored combat vehicles are characterized by their thermal capacity which is expressed in footings of turbine energy for one hr. For each “ storage hr ” , the turbine can be run at full capacity for one hr. Therefore, the storage volume ( in MWhth ) required for one storage hr is equal to the turbine capacity ( MWel ) multiplied by one hr and divided by the efficiency of the turbine and the heat transmittal to the turbine. In Spain most CSP workss are designed with indistinguishable storage size of about 1,000 MWh thermic energy capacity, tantamount to 7 – 8 hours of full-load turbine capacity ( Relloso and Delgado, 2010 ) . One illustration of a big storage is given by the Gemasolar tower near Servile which includes a storage armored combat vehicle with a capacity of 15 hours of turbine full-load ( Burgaleta, 2011 ) .

Another of import technological option for CSP workss is to complement solar power by firing natural gas. This gas combustion activity ranges from little sums of natural gas for anti-freeze protection to an electricity end product which is based on natural gas usage by 15 % ( hybridisation ) in Spain ( Caldes et al. , 2009 ) or up to 25 % in the US ( IEA, 2010 ) . In the hereafter, advanced engineering and operation schemes may originate due to new market chances. One hereafter option for CSP workss could be hive awaying electrically generated heat in the thermic storage armored combat vehicles. Lizzaraga-Garcia et Al. ( 2013 ) depict a proficient solution by adding little electrical warmer of 4 kilowatts each on internal perpendicular walls in the hot storage armored combat vehicle. The storage medium has to be heated uniformly and under steady conditions to avoid overheating of the salt. The presented theoretical account includes this option by presuming the handiness of an electrical warmer to hive away electricity from the grid as thermic energy in the storage armored combat vehicle. This may be an interesting operational pick if electricity monetary values reach low degrees, e.g. , during hours of high air current coevals. Extra costs for the electrical warmer system were non included in the analysis, but an economic appraisal is provided by Lizzaraga-Garcia et Al. ( 2013 ) .

The economic rating of CSP workss with storage has been discussed more often in recent old ages. From a proficient point, Garcia et Al. ( 2011 ) develop a elaborate theoretical account to demo the proficient flows of energy and to ease the anticipation of the electrical end product of a CSP storage works. Morin ( 2011 ) develops an optimisation tool for CSP workss based on the levelized cost of electricity ( LCOE ) . The disadvantage of the LCOE method is the equalisation of each kWh generated in the denominator. The point of clip at which the electricity is generated is non considered in this expression. Therefore, the value of dispatchable power workss like CSP storage workss is underestimated as their possible to respond to current market monetary value conditions is ignored. Sioshansi and Denholm ( 2010 ) develop a assorted whole number plan ( MIP ) to account for electricity market monetary values in the rating of CSP storage workss. This theoretical account determines the optimum operation of a CSP under market monetary values. Consequently, it closes a patterning spread of the SAM ( System Advisor Model, 2012 ) which does non ease a market-based rating of CSP workss. The theoretical account of Sioshansi and Denholm uses SAM ‘s energetic theoretical account for the solar field while runing the works harmonizing to the MIP theoretical account. CSP works operation reflects several parametric quantities like raging cost, efficiencies, upper limit and minimal tonss. Madaeni and Sioshansi ( 2011 ) expand the attack and analyze the CSP power workss in the US. They find that workss with storage of two to four hours feature the lowest break-even degree.

Aga et Al. ( 2012 ) compare the net nowadays value ( NPV ) of CSP workss with and without storage under the Spanish system. They underline the importance of cost lessenings for TES for CSP workss to accomplish fight with conventional power workss. Nagl et Al. ( 2011 ) present a scenario mentality for Spain with different portions of renewable energies. They conclude that CSP workss are non competitory under current investing costs. However, they besides note that CSP value will increase in future energy scenarios due to their energy storage capacity. A similar consequence is presented by Brand et Al. ( 2012 ) . They describe renewable energy scenarios for North Africa and happen that CSP dispatchability becomes more valuable if the portion of renewable energies increases.

Optimization of operation and investing determination

The optimum thermic storage size of a CSP works demands to account for the subsequent despatch determinations based on the works ‘s gross watercourse ( hourly electricity market monetary values, fixed FIT, P-FIT ) . Therefore, an hourly despatch theoretical account can be used to measure different investing options. A two-step attack for the works rating procedure was proposed by Madaeni and Sioshansi ( 2011 ) . First, an appropriate works set with over 100 different works layouts stipulating a solar multiple and storage size for each works is generated. Thereafter, the optimum operation policy for each works in the set is derived and the net nowadays values are compared.

This paper extends the attack along multiple dimensions. First, extra proficient options – use of natural gas for hybridisation and storage of electricity from the grid by agencies of an electrical warmer – are included to better reflect CSP works operations and shed visible radiation on the viability of alternate operation manners. Second, the determination theoretical account was refined: Alternatively of a two-steps attack ( for operation and investing ) , the works design picks are integrated as whole number determination variables in the despatch optimisation theoretical account. The coevals of a set of power workss is incorporated in extra restraints. These restraints are created by sing the relevant investing restraints. Following Madaeni and Sioshansi ( 2011 ) , the set of workss is spanned by sing different combinations of solar multiple and storage size. Furthermore, investors could besides see the works location if there are multiple possible sites. Input profiles for the solar thermic end product from different solar Fieldss are generated by the energetic theoretical account of SAM to find restrictions of the thermic end product of the solar field of each works design ( Figure ) . The variables and parametric quantities in the optimisation are given in Table: Variables and invariables in storage optimisation job.

Figure: MIP works rating model

Table: Variables and invariables in storage optimisation job

Constants

Decision variables

Market monetary value of supplying 1MWh of electrical energy to the grid at clip T

Sum of electricity fed into grid at clip T

Variable costs of turbine operation

Cost of firing 1 MWh of natural gas

Sum of gas burned at clip T

Cost of dumping 1 MWh of electrical energy ( waste )

Sum of energy electricity? dumped at clip T

Fixed operation costs

Purchase fee for purchasing 1 MWh from grid

Electricity purchased from grid at clip T

Specific cost of solar field

Factor for Solar Multiple ( distinct values )

Specific cost of storage

Factor for storage size ( distinct values )

Base cost ( power block and others ) independent of storage and solar field size

Terminal value

Life of power works ( old ages ) .

Thymine

Planing skyline T consists of all hours t which are optimized ( e.g. 8760 ) .

Annuity depending on involvement rate ( I ) and life-time ( Y )

Cost of burden accommodation per MW alteration

Load alteration in clip T

Energy from solar field at clip T

Power block start-up energy

Energy from solar field that is straight used in power block

Power block heat rate map

Thermal energy to power block at clip T

Parasitic map of heat procedure

Parasitic map of storage procedure

Storage degree at clip T

Self-consumption of power block at clip T

Energy to TES at clip T

Hourly losingss in TES

Energy from TES at clip T

Maximal efficiency of the turbine

( merely necessary to cipher the maximal usage of natural gas )

Efficiency of dispatching and bear downing procedure

Efficiency of thermic energy coevals from electricity

Maximum of hourly gas ingestion

Maximum of hourly electricity purchase

Maximum portion of one-year gas ingestion

The nonsubjective map ( 3 ) of the assorted whole number job maximizes the works ‘s hard currency flow ( operational net income and investing rente ) over the planning skyline T:

To simplify the fiscal rating, one-year optimized hard currency flows were considered to stay changeless over clip. An implicit in premise for this being that both solar and market conditions remain stable over clip. The theoretical account operates with perfect foresight of the electricity pool monetary value and the solar radiation over the whole twelvemonth. This is a sensible simplification as short-run prognosiss are continuously improved. The simple hard currency flow construction of the nonsubjective map contains one-year optimized hard currency flows of operational net income, terminal value by V, fixed operation costs fc and the rente of the investing.

CSP power workss are optimally dispatched in conformity with the current market and solar conditions. The nonsubjective map includes both the operation grosss and the investing costs in a individual preparation. The optimisation is capable to several restraints that reflect, among others, storage transfer, efficiency and raging conditions. These restraints follow the general attack described by Madaeni and Sioshansi ( 2011 ) , but the original theoretical account was extended by extra restraints reflecting new operation manners. The restraints are:

Solar Multiple ( SM ) :

Storage Size:

Entire thermic energy ( flux ) :

Entire production:

Net coevals:

Storage degree:

Maximal gas ingestion:

Maximal one-year gas ingestion:

Maximal purchase of electricity:

Load alteration of power block:

Constraints ( 4 ) and ( 5 ) limit the size of solar field and storage which are covered by the theoretical account. The whole number determination variables for the storage size and solar multiple are exemplarily chosen here, but the scopes need to be adapted harmonizing to the investing state of affairs at manus. Constraints ( 6 ) , ( 7 ) and ( 8 ) reflect extra operational restraints covering the usage of natural gas, hive awaying of electricity from the grid and works self-consumption. The proficient and regulative deductions of utilizing natural gas as intercrossed operation manners are covered by restraints ( 10 ) , ( 11 ) and ( 12 ) . Constraint ( 13 ) indicates the burden alteration between two clip units.

Figure illustrates the optimum operation policy of a CSP works with storage obtained from the optimisation theoretical account under electricity pool monetary values for a few selected yearss. The figure exemplarily shows how the optimisation theoretical account selects the operation scheme to maximise works profitableness. The optimum works operation is clearly driven by both, the market monetary value and the solar conditions. During the twenty-four hours the works ‘s power block generates electricity and excess solar thermic energy is transferred to the energy storage. If the monetary value is high in hours without sunlight the power works operates the power block utilizing energy from the storage. Figure 4a explains a down-ramping in the late afternoon to hive away more energy until 9pm to feed-in electricity at higher monetary values. During absolutely cheery yearss ( 4b ) the CSP works operates at full capacity from 8am in the forenoon to 1am the following twenty-four hours while a little portion of energy can non be stored in the storage ( full armored combat vehicle ) and has to be dumped. Figure 4c presents the instance of natural gas usage during the dark to avoid shutdown during dark. This besides improves raging in the forenoon to full capacity after dawn. During darks with really low electricity monetary values ( close to 0 Euro/MWh ) the works shops electricity from the grid ( e.g. , from wind power workss ) through electrical warmers in the storage from 3 to 5am ( see Figure 4d ) . These illustrations indicate that CSP workss with thermic storage offer extra potency to switch electricity coevals to times without solar radiation. Furthermore, both natural gas feed-in every bit good as direct electricity storage are feasible and relevant operation manners in certain state of affairss.

Figure: Optimum operation scheme for 4 different clip periods ( 36 hours )

( a ) 08.05. : Power block ramped down during the twenty-four hours to ease eventide production

( B ) 05.05. : Stable monetary value and high solar consumption lead to dumping during the twenty-four hours and coevals throughout the dark

( degree Celsius ) 21.10. : Gas burnt avoid nightlong coevals closure

( vitamin D ) 25.01. : Low night-time electricity monetary value facilitates buy and store scheme

Storage operation and rating – A Spanish instance survey

The MIP theoretical account for CSP works operation and investing determinations was evaluated by analyzing a CSP parabolic trough works in the Spanish market, similar to Andasol One. The energetic end product from the solar field is modelled with SAM utilizing a typical meteoric twelvemonth ( TMY file ) from Meteonorm for the country near to Guadix ( Spain ) with a direct normal irradiance ( DNI ) of 2,182 kWh/ ( mA?*year ) ( Meteonorm, 2011 ) . Cost premises by Kost ( 2012 ) for a 50 MW are included in the analysis by scaling these Numberss up to a 100 MW power workss by utilizing a decrease scale-up factor ( Kistner, 2009 ) . In table 2, the cost points for the solar field, power block and thermic storage are presented. For illustration, the entire costs of a CSP works with SM=2.8 and 8 hours of storage are 557.4 Mio Euro. The thermic storage armored combat vehicle histories for a important portion ( 15 % ) of the entire investing costs of this works. Fixed operation costs for a 100 MW works were calculated by the SAM theoretical account to 5.3 Mio Euro per twelvemonth.

Table: Cost constituents of a CSP works with a turbine capacity of 100 MW and variable solar field and storage size, based on Kost ( 2012 ) and Kistner ( 2009 )

Component

Cost

[ million a‚¬ ]

Cost of solar field ( )

120.7

per 1.0 Samarium

Cost of power block ( )

1.18

per 1 MW

Cost of thermic storage ( )

12.5

per 1 hr storage

The Net Present Value of CSP storage workss is analyzed under different wage strategies ( market monetary values, feed-in duties ) over the fiscal life-time of a power works. Due to high investing cost, no CSP works is competitory at an electricity monetary values between 20 and 60 Euro/MWh ( the Spanish mean market monetary value was 37.4 Euro/MWh in 2010, OMIE, 2010 ) . Presently, CSP workss would necessitate electricity monetary values that are 3 to 5 times higher than market monetary values as the engineering is still at the beginning of its acquisition curve where important cost decreases have non yet been realized ( see Estela /AT Kearney 2010 ) .

A generic end for any support strategy would be to make a sensible return on equity for investors while bring oning works operation in conformity with residuary burden forms. For CSP storage workss, the strategy has to particularly take into history the possible to hive away energy and utilize it at a ulterior point of clip.

The theoretical account determines the best works constellation out of 100 different SM and storage size combinations. Using 2010 market monetary value, this economic rating outputs negative values for all works constellations. On the other manus, under the current CSP support strategy ( P-FIT ) , CSP works investings are feasible depending on the involvement rate. Figure shows these consequences computation is shown for involvement rates of 10 % and 20 % . With lower involvement rates all SM / storage size combinations have a positive NPV. Naturally, this consequence strongly depends on the cost premises and the turbine size. The analysis shows that the rating differences between the storage armored combat vehicle with a capacity of 6 and 11 tantamount full burden hours are non excessively pronounced, if solar field size is chosen suitably. This suggests that proficient restraints ( armored combat vehicle volume, radius, tallness, thermic losingss, and thermic emphasis on stuff ) may be the ground that most Spanish CSP workss are equipped with eight hours of thermic storage capacity. By utilizing larger turbine sizes, proficient restraints of constituent sizes ( such as storage size ) could be lower as scalability of thermic storage capacity was increased.

Figure: Cash Flow analysis of a 100 MW CSP works under the premium FIT in Spain with electricity monetary values of 2010 with an involvement rate of 10 % ( left ) and 20 % ( right ) .

Market scenarios and their consequence on operation and layout

Investing inducements for CSP workss with thermic storage demand to suitably account for the mutuality between subsidy strategy, works design and the optimum works operation policy. Therefore, an ill-designed strategy can give rise to two inefficient results originating from optimum behavior of works investors or operators:

Inefficient storage-sizing by strategically leveraging the inducement strategy ( works design )

Operation manner choice non aligned with general market conditions ( works operation )

Clearly, inefficiency in works design is basically driven by an inefficient operation strategy. In the following the consequence of the Spanish feed-in duty on optimum CSP works operation is compared to the instance of a works operated merely reflecting the electricity pool monetary value ( market status ) by utilizing the MIP theoretical account for storage operation and investing determination. Subsequently, it is investigated whether the two governments give rise to different optimum works design picks.

The consequences are calculated for the Spanish market utilizing electricity pool monetary values of 2008 and 2010. Furthermore, German and Italy electricity exchange monetary values were used to look into the hardiness with regard to alternate monetary value scenarios. See Figure for an overview of the monetary value continuance curves of each monetary value vector. To keep comparison, the cap and floor values of the premium feed-in duties used for the German and Italian scenario were adjusted by the one-year norm of these monetary values in relation to the Spanish market monetary value of 2010.

[ Euro/MWh ]

Clairvoyance

2010

Clairvoyance

2008

GER

2010

ITA

2010

mean

37.40

68.84

44.49

64.13

South Dakota

14.41

11.01

13.97

18.37

upper limit

108.00

103.15

131.79

174.62

lower limit

0.00

29.50

-20.45

10.00

Figure: Monetary value continuance curve of Spain ( 2008 and 2010 ) , Germany ( 2010 ) and Italy ( 2010 )

The jobs of a premium FIT can be highlighted when sing the optimum usage of the storage and the optimum electricity production related to the hourly demand obtained in a pure market puting and in a PFIT scene. Both scenes are compared in the following with regard to differences in operation and optimum works design. We characterize the despatch disparity by looking at the day-to-day coevals derived function. This derived function is positive if the day-to-day end product to the grid is higher under the market government than under the P-FIT government while it is negative in the opposite instance. A zero-differential indicates yearss where the entire end product is indistinguishable under both governments. Figure: Comparison of day-to-day production of a CSP storage works under Pure Market scene and Premium Feed-in Tariff illustrates that there are important differences between the two scenarios over the twelvemonth. This is particularly true for the beginning and terminal of a twelvemonth. This seasonal consequence is due to more volatile electricity monetary values in the winter season. While a works in the market government is to the full exposed to this monetary value volatility, a works under the P-FIT subsidy is largely protected through the high monetary value floor. Clearly, storage is more valuable in a volatile than in a non-volatile market.

Figure: Comparison of day-to-day production of a CSP storage works under Pure Market scene and Premium Feed-in Tariff ( 100 MW CSP, solar multiple of 2.8, 8 hours of storage )

The hourly operation forms ( Figure ) confirm this observation. Under the P-FIT government works shut-down is more frequently avoided than under the market government – clearly seeable in the cardinal saloon in both histograms. Yet the “ binary ” works operation form under market wage is really similar to the manner a typical storage works is operated with either zero end product in times of low monetary values and maximal end product in times of high monetary values.

Figure: Distribution of hourly production of a CSP storage works under Pure Market scene and Premium Feed-in Tariff ( 100 MW CSP, solar multiple of 2.8, 8 hours of storage )

This difference between the two governments is driven by the energetic start-up costs of the turbine and the thermic energy losingss in the storage armored combat vehicles. Under a market government these energy losingss have limited value given a low market monetary value. However, under P-FIT support the energy losingss are significantly more dearly-won due to the high guaranteed floor value. Therefore, under the market regime the works is much more sensitive to the market monetary value. P-FIT consequences in significantly less storage use and coevals shut-downs than would be optimum under market conditions. As storage and reconciliation capablenesss are frequently put frontward as cardinal advantages of CSP engineering these effects may be of particular concern.

Ten

During the planning stage of a CSP undertaking, an investor evaluates different works layout options by making an economic and proficient appraisal of executable and profitable constellations. This analysis needs to account for the mutuality between works operation and works layout ( storage and solar field size ) picks. The theoretical account captures 100 different power works layout options. The optimum works layout is determined within the optimisation theoretical account by utilizing the investing model described above, presuming Spanish market monetary values from 2010, a utile investing life of 25 old ages, a terminal value of 10 % of the initial investing and an involvement rate of 6 % . As celebrated before NPVs are ever negative in the instance without a feed-in duty. Therefore, the optimum pick would be non constructing a power works at all or taking the smallest ( which would hold the least negative NPV due to take down investing costs ) possible power works. To be able to still analyse optimum works investing determinations under market based vs. P-FIT based wage an alternate attack was applied: We specify a set of fixed investing amounts ( runing from 434 to 606 million Euros ) that each has to be to the full invested in a corresponding CSP storage works. To guarantee non-singular investing sets a tolerance set of +/- 2 Mio Euro is applied and two extra restraints are introduced for the optimisation job:

Then, the most valuable ( highest NPV, i.e. least negative NPV ) works layout fiting the given investing amount is determined ( for illustration of this attack see Figure ) . By repairing the entire investing amount, different layout with tantamount costs can be compared ( see besides Figure in the appendix ) .

Figure: Three model fixed investing amounts give specific solar field and storage size combinations ( illustrations with 484, 520 and 532 Mio Euro ) . Optimum under P-Fit is market with a circle, optimum of market based operation with square.

The concluding consequences are shown in Table: . In Table: a pure market instance with electricity exchange market monetary values of 2010 ( Market instance ) can be compared to the premium feed-in duty based besides on electricity exchange market monetary values of 2010 in Spain, Germany and Italy ( P-FIT instance ) . For Spain, besides the monetary values of 2008 can be compared for both instances.

Given Spanish electricity monetary values of 2010, the P-FIT does so act upon the optimum investing determination in four of the eight instances ( shown in Grey ) . Similar effects can be seen when electricity monetary values of Germany and Italy or the monetary values of 2008 ( Spain ) are used. A more farinaceous discretization of solar field and storage size would ensue in even more mismatches. Under P-FIT investors choose smaller storage sizes in exchange for increasing the solar field. This confirms the observation of storage under-utilization in the P-FIT government. Hence, the P-FIT subsidy strategy influences both optimum works operations and optimum works design in comparing to the market instance. This consequence is besides robust to alterations of the storage and solar costs ( see Table in the Appendix ) .

Table: Optimum works design picks under market and P-FIT government for different investing volumes

Investing amount

( million Euro )

# of Layouts

434

3

460

4

484

5

508

7

520

6

532

8

556

6

606

4

Configuration

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Market instance

( ESP, 2010 )

2.2

4h

2.2

6h

2.4

6h

2.6

6h

2.6

7h

2.6

8h

2.8

8h

3.0

10h

Premium FIT

( ESP, 2010 )

2.2

4h

2.2

6h

2.6

4h

2.6

6h

2.7

6h

2.7

7h

2.8

8h

3.2

8h

Market instance

( ESP, 2008 )

2.2

4h

2.2

6h

2.4

6h

2.6

6h

2.6

7h

2.6

8h

2.8

8h

3.0

10h

Premium FIT

( ESP, 2008 )

2.2

4h

2.4

4h

2.6

4h

2.6

6h

2.6

7h

2.8

6h

2.8

8h

3.0

10h

Market instance

( EEX, 2010 )

2.2

4h

2.2

6h

2.4

6h

2.6

6h

2.6

7h

2.6

8h

2.8

8h

3.0

10h

Premium FIT

( EEX, 2010 )

2.2

4h

2.4

4h

2.4

6h

2.6

6h

2.6

7h

2.8

6h

2.8

8h

3.0

10h

Market instance

( ITA, 2010 )

2.2

4h

2.2

6h

2.4

6h

2.6

6h

2.6

7h

2.6

8h

2.8

8h

3.0

10h

Premium FIT

( ITA, 2010 )

2.2

4h

2.4

4h

2.4

6h

2.7

5h

2.6

7h

2.6

8h

2.8

8h

3.0

10h

SM = Solar Multiple

SS = Storage Size ( in hours tantamount to energy sum to run the turbine with full burden )

The inquiry is what can be done to incentivize CSP works investings that are better aligned with market demands? CSP works investings are presently non feasible without any subsidy. At the same clip the P-FIT support strategy distorts works design and operation picks compared to a strictly market based operation. This raises the inquiry whether another support strategy can vouch both sufficient investing inducements and economic works design and operation determinations. Keeping a generation-based wages construction, one could likewise conceive of dropping the base wage in exchange for increased market engagement. The market monetary value obtained by selling electricity at the electricity exchange could be multiplied with a fixed parametric quantity to vouch sensible grosss to the investors. The greater discrepancy of grosss enhances the value of storage and incentivizes market-oriented despatch. This comes at the cost of increased market monetary value volatility which renders CSP investings more hazardous and will probably increase the return required by investors. Furthermore, the subsidy payments would besides be really volatile which is extremely unattractive to investors and would lift with increasing market monetary values which is extremely unattractive to regulators. Generation-based wage strategies can therefore non guarantee market-oriented despatch every bit good as layout picks on the one manus and stable investing conditions on the other at the same clip. However, other authoritative investing subsidy strategies may besides falsify the layout and operation picks for CSP storage workss. An investing subsidy ( direct subsidy or revenue enhancement recognition ) lowers the investing cost for an investor and can take to a positive NPV of CSP workss. However, in the Spanish market investors would presently necessitate a direct subsidy of 60 to 80 % of the works investing. Such a high subsidy portion could easy give farther market deformations.

Given these problems with the assorted simple support strategies, it hast to be acknowledged that there is no silver slug for improved market integrating of CSP storage workss. Better suited support strategies should therefore include indirect wage for the proviso of dispatchable capacity for accessory or backup services. This impression resonates good with current treatments that aim to better reflect the negative outwardness imposed by intermittent coevals within the electricity market design ( Varaiya et al 2011 ) . The stipulated solutions include the constitution of capacity markets ( Creti & A ; Fabra 2007 ) to better counterbalance dispatchable power workss or the demand of adhering market committednesss by all market participants including renewable generators. The latter would necessitate to get sufficient storage capacity or enter appropriate hedge understandings to accomplish these committednesss ( Kim & A ; Powell 2011 ) . In contrast to other signifiers of renewable coevals, CSP storage workss are able to straight take part in capacity markets. Similarly, they would incur lower costs to function adhering market committednesss due to storage handiness. In drumhead, the dispatchability of CSP storage workss renders generation-based feed-in duties inadequate to guarantee market-oriented investing and operation behaviour. Future support strategies should therefore besides include an indirect wage for guaranteed handiness and capacity proviso degrees.

Decision and mentality

The operation of CSP workss with thermic storage opens the possible to supply dispatchable power to the electricity system. To reflect extra operational scenes, the CSP works optimisation theoretical account proposed by Madaeni and Sioshansi ( 2011 ) was extended. These extensions facilitate the rating of CSP storage works ratings in extra application scenarios. Using a Spanish instance survey, the relevancy of the extra operation manners is demonstrated. This analysis yields helpful penetrations for works investors, grid operators every bit good as regulators. First, the profitableness of CSP workss under the premium feed-in duty in Spain was assessed by analysing 100 possible works layouts at a location in Spain. The consequences indicate that several different works layouts are economically feasible, while in world merely a few layouts are chosen. Therefore with increasing engineering and market capacity, different sizes of storage capacities are expected to be constructed. Second, the comparing of operational forms under a premium FIT and the electricity market monetary value exhibit a different use of the storage capacity during many operation hours. Finally, investors will furthermore choose different works layouts depending on the wage strategy. These consequences signify that it would be good to set up a wage strategy which distinguishes between “ dispatchable ” and “ non-dispatchable ” renewable energy engineerings if the sum of energy from renewable beginnings should be farther increased.

To give an mentality on farther research inquiries the current developments in the energy sector are extremely interesting: More volatile electricity monetary values will increase the dispatch operation of CSP workss by utilizing their storage expeditiously. On the other manus a lessening of monetary values could look during peak hours between 1 and 3 autopsies due to big feed-in of solar photovoltaics ( see, e.g. , Germany in summer 2012 ) . A effect for CSP storage workss could be to hive away more thermic energy of CSP workss for the eventide. Additionally, demand forms could be changed to locations with higher mean electricity pool monetary values to reflect power export scenarios. Uncertainties of the investing determinations could besides be covered in farther work. The theoretical account itself can be extended by including stochastic parametric quantities for monetary values and solar resources. Other documents have besides shown the possible to supply modesty power which was non included in this paper.

Appendix

Table: CSP theoretical account parametric quantities

Maximal efficiency of the turbine

40 %

Efficiency of dispatching and bear downing procedure

1.5 %

Efficiency of thermic energy coevals from electricity

90 %

Maximum of hourly gas ingestion

300 MWhth

Maximum of hourly electricity purchase

50 MWel

Maximum portion of one-year gas ingestion

10 %

Self-consumption of power block at clip T

1.6 MWh

Hourly losingss in TES

0.031 %

Cost of burden accommodation per MW alteration

1 Euro/MW

Power block start-up energy

58.3 MWh

Variable costs of turbine operation

2 Euro/MWh

Cost of firing 1 MWh of natural gas

3.85 Euro/MMBTU

Cost of dumping 1 MWh of electrical energy

1 Euro/MWh

Purchase fee for purchasing 1 MWh from grid

1 Euro/MWh

Figure: Potential layouts under a fixed investing volume

Table: Sensitivity analysis of investing premises for solar field and storage system

Investing

( million Euro )

434

460

484

508

520

532

556

606

Components

Gross

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Samarium

United states secret service

Solar field costs +25 %

Clairvoyance

-o-

-o-

-o-

-o-

2.0

5h

2.2

5h

2.2

6h

2.4

4h

2.4

6h

2.7

6h

ESP-PFIT

1.6

6h

1.8

6h

2.0

5h

2.2*

5h*

2.2

6h

2.4

4h

2.4

6h

2.7*

6h*

Solar field costs -25 %

Clairvoyance

2.6

6h

2.6

8h

3.0

7h

3.0

9h

3.0

10h

3.0

11h

3.2

12h

-o-

-o-

ESP-PFIT

2.8

5h

2.8

7h

3.0*

7h*

3.0

9h

3.2

9h

3.2

10h

3.2

12h

-o-

-o-

Storage costs +25 %

Clairvoyance

2.0

5h

2.2

5h

2.2

6h

2.4

6h

2.4

7h

2.6

6h

2.8

6h

2.7

10h

ESP-PFIT

2.0

5h

2.6

2h

2.4

5h

2.6

5h

2.7

5h

2.8

5h

3.0

5h

3.0

8h

Storage costs -25 %

Clairvoyance

2.2

5h

2.4

5h

2.4

8h

2.6

8h

2.6

9h

2.6

10h

2.8

10h

3.2

11h

ESP-PFIT

2.2

5h

2.4*

5h*

2.4

8h

2.7

7h

2.8

7h

2.8

8h

3.0

8h

3.2

11h

Remark: tolerance set ( +/- 6 Mio Euro ) , * tolerance set ( +/- 2 Mio Euro )

“ -o- ” : no layout combination in the tolerance set ( +/- 6 Mio Euro )