2. THEORETICAL FRAMEWORK
2.7 Wind Power Costs Calculation Model
2.7.1 Cost Components and Energy Production
The cost components are assumed to be the investment costs (including possible interest during construction), operation and maintenance costs, repair costs, salvage value and social costs. Apart from the social costs, only the costs which relate to the wind turbine system up to the point of interconnection with the public transmission or distribution network are considered.
In some cases it may be necessary to reinforce the public transmission or distribution system (or to include special control devices, etc.) due to the introduction of wind power. In such cases, depending on the scope of the analysis, these extra costs (or a part of them) may be included in the analysis.
The wind energy output considered could be a) the annual net energy (ANEt) available at the wind turbine terminals, or b) the annual energy as utilised in the connected power system, i.e. the annual utilised energy (AUEt). The relation between the annual utilised energy and annual net energy can be described by:
(2.10)
Here, Klos,t is a factor relating to the electricity losses which occur between the wind turbine terminals and the electric grid where the energy is utilised, and Kutil,t is a factor which depends on how the transmitted wind energy is utilised in the power system, see Figure 30, example of an electrical system where the energy losses in the long medium voltage feeder are reduced due to the wind power production so that the utilised wind energy becomes higher than the transmitted net energy and Kutil,t > 1.
Figure 30. Example of an electrical system (Tande et al.1994: 5).
Depending on the scope and field of application, both the annual net energy output and the annual utilised energy output are recognised as adequate energy measures, and the assessor must judge which to use in each case.
2.7.2 Cost Calculation Methodology, General Approach
The measure of the estimated cost of energy adopted in this document is the levelled production cost. The levelled production cost (LPC) is the cost of one production unit (kWh) averaged over the wind power station's entire expected lifetime. The total utilised energy output and the total costs over the lifetime of the wind turbine are both discounted to the start of operation by means of the chosen discount rate, and the LPC is derived as the ratio of the discounted total cost and utilised energy output.
It is assumed that all costs are given in a fixed currency for a specified year. The currency and cost level year should be decided and clearly declared by the assessor when reporting the estimated cost of energy. In the calculations all costs are discounted to the present value, i.e. the first date of commercial operation of the wind turbine. The discounted present value of the total cost (TC)is given as:
(2.11)
The levelled production cost (LPC)is given as the ratio of the total discounted cost and the total discounted utilised energy, i.e.:
(2.12)
The annual utilised energy, AUEt, should be specified for each year by adjusting the annual potential energy output, Epot, with a number of correction factors:
(2.13)
2.7.3 Cost Calculation Methodology, Simplified Approach
In many cases it may be appropriate to assume the annual utilised energy to be constant from year to year (i.e. AUEt = AUE for t = 1 to n). In such cases, the LPC can be calculated as:
(2.14) LPC = I/(a • AUE) + TOM/AUE
a is the annuity factor as defined in the table below. I/a is the capital to be paid annually during the assumed period in order to cover both the depreciation and the assumed interest.
TOM is the total levelled annual "downline costs", i.e. all costs other than the initial investment. TOM may for simplicity be estimated as a certain percentage of the investment. The exact definition of TOMis given in symbols.
2.7.4 Calculation Method
The Calculation methodology is presented in Table 10. The calculation example is taken from Table 31. The wind turbine data is from producer D. Onshore bid prices are from producers’ offers. Offshore calculated prices are as mentioned in Table 10 on rows 26 to 33. Total investment is the sum of onshore bid price and offshore calculated price.
Operation and Maintenance costs are presented on rows 42-46Levelled Utilized Energy on row 49 is annual production multiplied with the correction factors: Performance factor Kper= 1, Site factor Ksite= 0.95, Technical availability factor Kava= 0.95, Electric transmission losses factor Klos= 0.95, Utilization factor K util = 1. The Production cost including O&M costs on row 46 can be calculated with spreadsheet calculation operator on rows 54 and 60, or, for example, manually as on row 59. The factors are: real interest: row 56; refund period: row 57; total investment: row 35; annuity factor divided by levelled energy: row 49.
Table 10. Calculation Method
1 A B C D E
2 Kilowatt Price with separate Power Plants in Euros
3 Measuring Periode on the Strömmingsbåda and Bergö Island on 22.11.97 - 26.11.1998, 4 Sources and Operators
5
6 Producer Source Turbine D
7 Rated Power (kW) Data 2000
8 Rotor D(m) Data 80
9 Hub Height h(m) Data 80
10 Weight (TON) Data 268
11
12 Onshore Bid Prices Source and Operators
13 Wind Turbine ex works 1717200 =+D13/D$13
14 Transport to Dock Bid 10000 =+D14/D$13
15 Transformer Bid incl.
16 Remote Control Bid incl.
17 Training Bid 11500
18 Accessory Bid 6100 =+D18/D$13
19 Warranty Time Service Bid incl.
20 Total =SUMMA(D13:D19) =+D20/D$13
26 Steel Foundation Figure 39 319508 =+D26/D$13*D$21
27 Transport Table 25 6487 =+D27/D$13*D$21
28 Harbour/Dock Assemblage Table 25 10485 =+D28/D$13*D$21
29 Site Work Table 25 16338 =+D29/D$13*D$21
30 Sea-bed Reseach (List of Statement) Korpinen 20000 =+D30/D$13*D$21 31 Cabling(20+5.2km,160/m,14 turbines) Chapter 5.5.4 288000 =+D31/D$13*D$21
32 Planning Estimate 10000 =+D32/D$13*D$21
33 Additional Charge Estimate 10000 =+D33/D$13*D$21
34
35 Total Investment =SUMMA(D26:D33)+D22 =+D35/D$13*D$21
36 /kW =+D35/D7
37 Investment Support 0 =+$B37*D35
38 Net Investment =+D35-D37 =+D38/D$13*D$21
39 /kW =+D38/D7
40
41 Operation and Maintenance (/year)
42 Operation and Maintenance (0,01/kWh) Chapter 2.4.3 =+D49*0.01 =+D42/D$13*D$21
43 Insurance Estimate 15000 =+D43/D$13*D$21
44 Administration Estimate 5000 =+D44/D$13*D$21
45 Total (/year) =SUMMA(D42:D44) =+D45/D$13*D$21
46 O&M (c/kWh) =+D45/D49*100
47
48 Annual Production (kWh/a) Table 23 9124506
49 Levelised Utilized Energy (0.86) Chapter 2.7.2 =+D48*0.95*0.95*0.95 50 Annual Production/Swept Area (kWh/m^2) =+D49/D58
51 Nominal Power Time (h/a) =+D49/D7
52 Capacity Factor (Cf) =+D49/8760/D7
53
54 Production Cost (c/kWh) =-(MAKSU($B56/100;$B57;D35)/D49)*100+D46 55
56 Real Interest %/Year 5 % Turbine D
57 Refund Periode Years 20 Year 2000
58 Swept Area (m^2) =+PII()*D8^2/4
59 PC=(1+0,05)^20*0,05/((1+0,05)^20-1)
60 PC=-MAKSU(0,05;20;1)