EG2220: Power Generation, Environment and Markets Balancing challenges for a close to 100% Renewable Power System

Transcription

1 EG2220: Power Generation, Environment and Markets Balancing challenges for a close to 100% Renewable Power System Lennart Söder Professor in Electric Power Systems, KTH

2 Price development for coal and Swedish Electricity Price

3 Development of gas prices

4 Development of gas prices (up to May 2016)

5 Current (2016) challenges in Sweden and many other countries 1.Low Power Prices 2.Depends to high extent on low costs on fossil fuels 3.Difficulties to fund existing power plants, e.g., nuclear and other

6 Eight challenges at high share of wind power in Sweden 1. Mechanical inertia 2. Balance regulation 3. Surplus situations 4. Transmission capability 5. Peak capacity 6. Larger needs of flexibility 7. Responsibilities and market design 8. Yearly control of hydro power

7 Some high varaible renewable challenges 1.High share of variable renewables 2.The 3 balancing challenges 3.Transmission challenge 4.Pricing challenges 5.Balancing in the heat sector

8 Results from new Swedish studies on larger amounts of wind power Lennart Söder, KTH

9 4 editions : Studies of a Swedish power system with close to 100% renewables wene.194/full

10 Swedish production: Total: 145,6 TWh (same as 2011) Other

11 Three challenges at large amount of variable renewables (solar/wind) C1: Handling of the continuous balance. C2: Low wind and solar power production and high power consumption. This issue is called capacity adequacy issue. C3: High wind and solar power production and low power consumption.

12 Three challenges at large amount of variable renewables (solar/wind) C1: Handling of the continuous balance. There must be a ramping capacity which is high enough Forecasts are uncertain so there must be enough online units to follow the net-load Larger interconnected areas reduces the overall variation, but requires enough grids.

13 Three challenges at large amount of variable renewables (solar/wind) C2: Low wind and solar power production and high power consumption. This issue is called capacity adequacy issue. There must be enough capacity (production, flexible demand and/or import) during these situations This may happen very rarely which is a challenge for the economy of these resources. More transmission reduces the need.

14 Three challenges at large amount of variable renewables (solar/wind) C3: High wind and solar power production + HVDC infeed and low power consumption. There must be enough inertia in the system in order to keep the frequency 100 % wind and solar instant power supply, means really high challenges concerning keeping voltage and frequency! There must be enough primary and secondary reserves in these situations.

15 Keep the balance in a power system

16 Real initial phase of a power system outage Time steps: A. Disconnection of Swedish 1050 MW nuclear station B. Primary control starts C. Primary control has increased with 1050 MW

17 Frequency drop after 3 real outages in Sweden Outage New unit Rate of change of frequency Depends on system inertia which can be low at large amounts of wind power

18 Keep the balance in the power system Different time steps: 1. Inertia (seconds) 2. Primary control (minutes) 3. Secondary control(quarter) 4. Tertiery control (quarter) 5. Intra-day-trade (hours) 6. Day-ahead-trade (day) 7. Weekly planning (week) 8. Yearly planning (year) Security Uncertianty Technology Economy

19 Inertia example: hydro power Contribution: Hydro power stations (larger) use synchronous machines which are directly connected to the grid. This means an important contribution to the needed inertia. Challenges: More slimmed constructions may reduce the inertia contribution. A challenge in power systems with, e.g. large amounts of solar power, wind power or HVDC infeed, which do not contribute with inertia. But there are technical solutions!

20 Three challenges at large amount of variable renewables (solar/wind) C1: Handling of the continuous balance. C2: Low wind and solar power production and high power consumption. This issue is called capacity adequacy issue. C3: High wind and solar power production and low power consumption. Lennarts view: Solve C2 and C3 needed resources. Then probably there is enough resources to handle C1

21 Current (2011) Swedish Power System Source TWh Energy % Hydro 66,0 44, Nuclear 58,0 39, Wind 6,1 4, Solar CHP-Ind 6,4 4, CHP-distr. 9,4 6, Condens 1,01 0, Total 146, MW-capacity

22 Studied Swedish Power System Source TWh Energy % MW-max Hydro 64,9 44, Nuclear Wind 46,7 32, Solar 12,6 8, CHP-Ind 6,4 4, CHP-distr. 13,9 9, Other 1,3 0, Total 139,

23 Simulation method (Sweden isolated) 1: Preliminary simulation a. Wind + solar + CHP: hourly time series: MWh/h b. Wind + solar: max 83% of load ( surplus ) c. Load = total prod ; Hydro min level ; CHP min level: Otherwise decrease wind+solar larger surplus d. If CHP + solar + wind + max-hydro load: difference = deficit e. requested hydro power production

24 x 10 4 C2: high load situation Need of more capacity MWh/h Consumption Hydro power Wind power Solar power CHP Consumption from 14 January to 30 January High wind decrease in CHP

25 C2: Need of more capacity (0,9% of all energy) 5000 Energy level [MWh/h] Max level: 5081 MW Number of hours with need: 765 h Energy: TWh Number of hours with need of more production Assume only OCGT (gas turbines) extra cost of 0,17 Eurocent/kWh

26 C3: Surplus situation Consumption Hydro power Wind power Solar power CHP MWh/h Consumption from 1 August to 10 August Not OK because of 83% limit, hydro minimum limit (1875 MW) and CHP min-level

27 C2: Surplus situation resulting operation Consumption Hydro power Wind power Solar power CHP MWh/h Consumption from 1 August to 10 August Wind+solar decrease because of 83% limit, hydro minimum limit (1875 MW) and CHP min-level

28 C2: Surplus during a year (2,7% of prod.) Max level: 9510 MW Number of surplus hours: 860 h Energy level [MWh/h] Energy volume: 1.63 TWh Number of hours with surplus/possible export

29 Hydro power: Duration curves (test ) Energy level [MWh/h] solar-wind scenario Number of hours with hydro power < certain energy level Min level: 1875 MW: Needed during 860 hours Max level: MW: Needed during 765 hours

30 Simulation method (Sweden isolated) 2: Detailed simulation a. Simulate one week with details of Swedish hydro system (256 hydro power stations, details of flow time, court decisions, inflow etc) b. Assume wind+solar+chp from preliminary simulation as fixed c. Formulate a linear optimization problem (deterministic) d. Problem has equations and variables

31 Hydro Power challenges in Sweden Varying inflow per point Rivers link the stations hydrological coupling Water court decisions: Min. flow and res. content Cm/day change of reserviors Max. flow and res. content Season dependent. etc

32 Simulation method (Sweden isolated) 2: Detailed simulation a. Objective function: b. where H spill (k)= hydro spillage during hour k, V spill (k) = Wind spillage during hour k, EXP(k) = extra export during hour k, IMP(k) = extra import during hour k, K = number of hours in the studied period (=168).

33 Preliminary simulation for a January week x 10 4 MWh/h Elförbrukning Vattenkraft Vindkraft Solkraft Värmekraft Förbrukning från 1 november till 7 november

34 Example: Result after detailed simulation (normal inflow) x MWh/h Consumption Hydro power Wind+solar Other prod. Förbrukning Vattenkraft Vind + sol Övrig produktion Timme under studerad vecka Result: Possible for hydro power to meet expectation, except for hour 119

35 Example: Result after detailed simulation (160% of normal inflow) x MWh/h Förbrukning Vattenkraft Vind + sol Övrig produktion Timme under studerad vecka Result: Many hours with need to export (or spillage)

36 Results from detailed simulation Two weeks tested (normal inflow): C3: High load + low wind week C2: High wind + low load week For both weeks it was possible in the detailed simulation to follow the requested operation. Reports (in Swedish) available from:

37 Surplus during a year Max level: 9510 MW Number of surplus hours: 860 h Energy level [MWh/h] Energy volume: 1.63 TWh Number of hours with surplus/possible export

38 Transmission challenges in a future with large amounts of variable renewable power.

39 General transmission challenge A. Voltage stability limits between areas B. Q-control important C. More transmission required, but low utilization time D. Challenge to identify future transmission capacity with less nuclear E. Detailed hydro simulation takes 10 minutes per week.

40 Surplus situation (August 1-10) Wind Power production

41 Surplus situation (August 1-10)

42 Surplus situation (August 1-10)

43 Transmission situation (Jan 21 Feb 1) Wind Power production

44 Transmission situation (Jan 21 Feb 1)

45 Transmission: Yearly duration : today 7000 MW

46 On transmission needs A. Increase production in receiving end (= thermal, currently OCGT) B. Capacity is available, small energy increase for first GW. C. Since limit is voltage stability, SVC may be enough D. Discussion on exchange of AC to DC E. Optimization approach may be interesting

47 Pricing challenges in the future Nordic Power Market with large amounts of renewable low marginal cost units.

48 Nordic Power Supply TWh 2012 Country Nuclear Hydro Fossil Wind Bio Total Norway 0 142,9 2,4 1, ,8 Finland 22,1 16,6 17,9 0,5 9,9 67,7 Sweden 61,2 77,7 4,6 7,1 10,8 161,6 Denmark 0 0,02 16,3 10,2 2,3 29,4

49 Nordic hydro power In 2012 the Nordic hydro power production was 237 TWh. This corresponds to an inflow of around 4,5 TWh/week A heavy rain every second week implies 9 TWh

50 Pricing in power systems Thermal power systems: Price is set by marginal cost Hydro power: Price is set by the water value = the expected marginal cost in the future to which the water could be stored. Wind power: Price is set by marginal cost = negative subsidy, since subsidy is only obtained at production (e.g. -2 Euro-cent if certificate price is 2 Euro-cent.)

51 Pricing in power systems: Norway Nearly only hydro power (97%) Price is set by the water value = the expected marginal cost in the future to which the water could be stored. Price is not set in Norway!

52 Pricing in power systems: Sweden Hydro + Nuclear + wind (90%) Large part of the rest is CHP (industrial and distr. heat) Price is set by the water value = the expected marginal cost in the future to which the water could be stored. Price is not set in Sweden!

53 Pricing in power systems: Denmark 2020: High wind power (50%) A part of the rest is CHP (industrial and distr. heat) When it is windy, then the prices will be low High prices are often not set in Denmark!

54 Pricing in power systems: Finland Nuclear + hydro + wind (58%- now) CHP + more nuclear in the future At wind and low demand, then the prices will be low Prices are then often not set in Finland!

55 Pricing in future Nordic power systems: Much more often: Prices are not set by Nordic power plants. At wind and low demand, then the prices can be really low There is then a challenge to get prices that are high enough to finance all power plant. Enough transmission to high MC areas essential

56 Identified wind power projects in Sweden: Identified wind power projects: MW ( 100 TWh/year) Today capacities: Hydro Power: MW ( 65 TWh) Nuclear power: 9000 MW ( 65 TWh) total of MW

57 Using district heating system for use of surplus from wind and solar. Lennart Söder

58 C2: Surplus at 55 TWh wind+solar Different assumptions on wind/solar 70-90% of consumption Effektnivå [MW] Exempel 2a ej fjärrvärme Exempel 2a med fjärrvärme Exempel 2b ej fjärrvärme Exempel 2b med fjärrvärme Exempel 2c ej fjärrvärme (no nuclear) Exempel 2c med fjärrvärme Max ca 90 percent of consumption - No distr. heat. - surplus: - 0,61 TWh/year Solution: - Export - District heating - Other head - El. vehicles - Etc - Inertia? Antal timmar som överskottsproduktion i Exempel 2a-2c överskrids

59 Model of CHP and district heating a. In Part 2 there is the assumption that one can use surplus electricity (MC=0) in the district heating instead of spillage. b. In Part 3 there is the assumption that one can use surplus electricity (MC=0) to replace CHP instead of spillage. c. Reality is probably both with some limitations.

60 Model of district heating [MW] Stockholm fjärrväremeleverens under 2012 a. Total district heating in Stockholm during 2012 per hour (City-Söder, including Söderenergi and Nordvästra including E.ON Järfälla)

61 Model of district heating januari februari mars april maj juni juli augusti september oktober november december 8000 Effektnivå [MW] Timme på året med nivå över 75 procent av förbrukning a. Amount of excess of wind+solar > 75% of deman.

62 Model of district heating - 3 Assumptions: a. Swedish yearly disstrict heating same profile as in Stockholm b. Same level of fuel waste as today (18%) which is not replace (negative MC) c. Heat spillage or rökgaskondensering not replaced with electricity.

63 Model of district heating [MW] Spillvärme Avfallsförbränning Värmebehov under 2012 a. Result for the potential of heat replacement

64 Model of district heating [MW] Möjlig elförbrukning (trappstegskurva) och tillgänglig elproduktion a. Result for the replacement: 1.2 TWh used (out of 3,0 TWh available surplus)

65 Model of CHP ,00 Data-Kraftvärme: 1 Januari - 31 December 4000, , , , , , ,00 500,00 0,00 a. Yearly CHP production in 2011

66 Model of CHP - 2 Model: a. 50% more CHP than today (from Profu report) b. It is possible to decrease CHP down to 25% of its original value during each hour c. But the total amount of hydro + CHP muast be 17% of production (synchronous machine requirement) d. Excel sheet available to change these data.

67 Model of CHP- 3 x MWh/h Elförbrukning Vattenkraft Vindkraft Solkraft Värmekraft Förbrukning från 14 januari till 30 januari a. Example of resulting CHP decrease:

68 Model of CHP ,00 Resultat-kraftvärme-minskning: 1 Januari - 31 December 2000, , ,00 500,00 0,00 a. Resulting CHP decrease: 0,79 TWh = 5,4%

69 Model of CHP Resultat-kraftvärme-minskning: Varaktighetskurva; Max= 2267 MW; Energi= 0,79 TWh a. Resulting CHP decrease: 0,79 TWh = 5,4%

70 Questions on CHP + District heating a. Amount of waste etc (MC <0) in future? b. How much can one decrease CHP? c. How fast can one decrease CHP? d. Electric boilers in district heating? e. Uncertainties on amount of CHP/district heating in future?