Energy Management in the Greek Islands

Transcription

1 21, rue d Artois, F PARIS C6-303 CIGRE 2012 http : // Energy Management in the Greek Islands Nikos HATZIARGYRIOU 1,2 Stavros PAPATHANASIOU 2,Isidoros VITELLAS 1, Stavros MAKRINIKAS 1, Aris DIMEAS 1,2, Theodora PATSAKA 1, Kostas KAOUSIAS 1, Antiopi GIGANTIDOY 1, Nikos KORRES 2 Eleanna HATZOPLAKI 2 PPC 1, Greece NTUA 2, Greece N.Chatziargyriou@dei.com.gr, adimeas@power.ece.ntua.gr SUMMARY This paper presents the basic challenges and the goals of Public Power Corporation regarding the operation of the Greek Islands in the following years, focusing on the management of RES and the installation of new Energy Management Systems. A driving force for these changes is the new legal framework that requires the operation of an energy market. Finally some results from related studies of PPC are presented. KEYWORDS Renewable Energy Sources, Energy Management System, Transmission and Distribution Networks, Main author: Nikos Hatziargyriou ( nh@power.ece.ntua.gr) 1

2 1. INTRODUCTION Greece has 36 non interconnected islands (NII) with a peak load demand ranging from 100kW to 700MW. The primary power supply is based on various types of heavy and light fuel oil. Furthermore the RES penetration is very high in several islands, as for example in Crete which is the largest island in the Aegean Sea; the installed RES (PV and Wind) capacity exceeds 300MW. Figure 1. Map of the Aegean Sea and Existing and planned Power Stations The Greek islands have several interesting characteristics [1]. Typically they are summer peaking systems due to air conditioning and increased summer tourism. The ratio between minimum and maximum load is high. For example in the case of Crete the minimum daily loads are around 200 MW, while the maximum values often exceed 500MW. Thus, PPC must cycle its generation over a large range during the course of each month. 2

3 Figure 2. Average variable generation cost per island system (2010). Figure 3. Load and Wind Farm production in Crete system during the year 2010 The next challenge is the increase of RES penetration (Figure 4). At the moment, there is a significant interest from private investors to install large RES stations, using not only conventional technologies, such as Wind Farms and Photovoltaic Plants, but also new technologies in large scale: Hybrid Stations (Combination of Wind Farms and Pumped or Battery Energy Storage) and Concentrating Solar Thermal Power Plants (STPP). 3

4 Figure 4. Unit Commitment in a typical day with high RES penetration in Crete RES stations are typically characterized by power intermittency. In small isolated systems, the penetration of intermittent power sources in the generation mix is limited due to technical constraints introduced by the conventional units, including increased spinning reserve requirements, respect of technical minima of thermal plants, frequency control and stability considerations. With limited control capabilities, operators are obliged to follow conservative procedures, rejecting part of the available resources. To overcome this limitation, advanced management systems with effective control capabilities need to be implemented. An important challenge for the following years is to operate an energy market in the islands, according to the EU and Greek national legislation. A critical actor for the energy market operation is the island System Operator, whose obligations encompass, among other things, management of the generation, operation and financial clearing of the Market and management of the island networks. The island Operator is also responsible to ensure the adequacy of generation capacity, the reliability and quality of supply to the customers and for the efficient operation of the market. The operator is also responsible to maximize RES penetration and minimize the variable generation cost, as well as the total generation cost, on a long-term basis. PPC plans to install an advanced Energy Management System (EMS) in the noninterconnected islands [2]. The EMS will have a semi-distributed architecture. It will include a central control center to be installed in Athens, together with several Local Control Centers (LCCs) installed on each island. The central control center will implement the day-ahead planning and monitoring functions, including electricity market functions, relying on load and generation forecasts or power/energy bids for all types of RES stations (wind farms, hybrid stations, CSP plants and PV systems). 4

5 2. THE CURRENT INFRASTRUCTURE The new EMS is designed to create the technical infrastructure to allow a substantial increase of renewable penetration (mainly wind and solar power) in the autonomous Greek islands systems. Currently, the operation of the Greek islands is based on mostly outdated infrastructure, e.g. in the islands of Crete and Rhodes the energy control centers rely on old SCADAs, based on Unix/VMS systems installed at the mid-80s. The operators are equipped with real time monitoring of generation units, wind farms and load feeders, but the main operating decisions are taken based on their experience. During operation, the main constraints are the instantaneous RES penetration (max 30% of the load), the penetration level determined by the technical minimum of dispatched thermal units, the spinning reserve (N-1 reserve plus approximately 50% of RES power) and additional network constraints. In the smaller islands, the control and system operation center is located inside the main thermal power station. In general, SCADA systems are installed only for the power station itself and the island system is operated by the staff of the control centers. The operators monitor and control the WFs, but there is limited information about the loads. The technical constraints are similar to larger systems and the same policy regarding spinning reserve is adopted. 3. ARCHITECTURE OF THE NEW EMS The main idea behind the system architecture is to monitor, control and manage the power systems of all non-interconnected islands. The solution studied corresponds to a partially Centralized Control Center architecture as illustrated in Figure 4. Figure 4 Illustration of the partially distributed architecture. The central system will be installed in Athens and will monitor and manage isolated systems of different degrees of complexity, in terms of market environment, presence of transmission network, types of RES stations and levels of renewables penetration. This central system will be part of the Control System of the Non Interconnected Island System Operator (NIISO). Local Control Centers are planned for the larger islands of Crete and Rhodes. 5

6 The Control Center of NIISO, to be located in Athens, will have generation planning functions together with monitoring tasks. Local control centres will provide a back-up solution in case of central system or communication unavailability. 4. ENVIRONMENTAL GOALS The deployment of Smart Grids in the Greek Islands aims at creating the technical conditions to allow the increase of the share of renewable generation in the Greek Islands. The island operator has made several studies regarding the necessity of Smart Grids in the islands. Some key results from the island of Crete are provided next. The island population in 2009 was close to inhabitants and the electricity demand reached 2732,7 GWh. This demand was mainly supplied by traditional light and heavy fuel oil power stations, with some contribution from wind parks and PV systems. Using traditional tools, the integration of renewables, especially volatile resources as wind and solar power, is limited because the power system of Crete operates in an isolated mode and larger amounts of renewables would require traditional generation capacity to provide increased regulation and reserve. With the installation of control centers, the technical and operational conditions will allow a rapid increase of renewable generation in the current decade. By 2025, it is expected that the total RES energy will amount to 1727,0 GWh, corresponding to 42,8% of the annual load energy demand. In the absence of control centers, RES penetration would not exceed approximately 19%. Table 2 provides an overview of the expected benefits due to the increase of RES penetration Annual RES contribution (GWh) 304,6 387,5 481,3 585,6 704,4 Energy from PV (GWh) 192,1 244,4 303,1 369,3 444,2 Energy from WF (GWh) 112,5 143,1 177,5 216,3 260,1 Table 2. Expected increase in RES penetration. 5. WIND GENERATION CURTAILEMENT Wind generation needs to be occasionally curtailed during periods of high-wind and low-load for reasons of network security and other generator constraints. A predominant curtailment rule established by PPC is that wind generation cannot exceed 30% of the hourly load demand. PPC data was studied to determine the impact of adding more wind generation and the resulting impact on curtailed (dumped) wind energy by the application of this rule. For this study [3], hourly average load and total wind generation values were computed using the actual minute-by-minute telemetered data of PPC. For each hour, one can determine the maximum amount of allowable wind (30% of the load), and any wind generation above this value that would be curtailed. During the 37-month study period (September 2006 through September 2009), the actual wind energy had the following characteristics: Average Actual (Curtailed) Wind Generation = 42.8 MW 6

7 PPC estimates that 14% of the wind generation was curtailed, which equates to 7.0 MW. Without curtailment, the average total Wind Generation would have been = 49.8 MW Average Installed Wind Capacity over the study period = MW Actual (Curtailed) Capacity Factor = 42.8 / = 31.4% Estimated Non-curtailed Capacity Factor = 49.8 / = 37% In a next step, the wind generation was scaled up to simulate increased installed wind generation capacities (195, 260 and 325MW). On an hour by- hour basis, any wind generation above 30% of the load was curtailed. The following table summarizes the results, including the actual wind generation numbers presented above. Note that the non-curtailed wind capacity factor is assumed conservatively to be 37%--wind speed data suggest new wind generators could easily achieve a 40% capacity factor. The sample calculation that follows further clarifies the methodology and the results that were obtained. At hour 04:00 of October 19, 2008, the average actual hourly load was 150MW and the average hourly wind power was 40MW, while the installed wind capacity was 100MW. If wind capacity doubled to 200MW, wind generation would double to 80MW. Since permissible wind penetration is 30% of the load, i.e. 150 * 0.30 = 45 MW, = 35 MW of wind power would be curtailed during that hour. This calculation is repeated for every hour of the 37-month study period. Table 3: Wind Energy Curtailment as Wind Capacity Increases As the amount of installed wind capacity increases, the Average curtailed Wind Generation increases from the current 14% to 39.9%. This reduces the Effective Curtailed Capacity Factor from the present value of 31.4% down to 22.2% (against an un-curtailed wind capacity factor of 37%). This will prohibit the installation of additional wind generation on the island of Crete, unless the current wind penetration constraints are relaxed. For this purpose wind parks would have to provide dependable power (implying a much more reliable wind forecasting service) and the wind generators would need to contribute actively to primary and secondary regulation of the system. A more effective option would be the introduction of energy storage, in the form of Hybrid Power Stations. 6. CONCLUSIONS The operation of the Greek island presents many challenges. The installation of an increased percentage of renewable generation including new RES technologies as well the operation of the energy market will complicate this operation further. PPC plans to install new Energy Management Systems to help the island system operator to operate the systems in the most 7

8 economical and secure way maximizing at the same time RES penetration. Work is on-going aiming at preparation of the technical requirements of the new EMS. Valuable experience has been gained from its participation in several EU funded project such the CARE, MORE CARE [4], Anemos.plus [5] and Safewind [6]. 7. REFERENCES [1] Smart Grids in the Greek Islands I. Vitellas,. A. Dimeas Keynote Speech ISAP September 2011 Hersonissos Crete, Greece (in Greek). [2] Adequacy, economic viability and environmental requirements for autonomous island power systems. I. Vitellas, PPC S.A. ENERTECH September 2009 Athens Greece. [3] Assessment and Economic Analysis of Wind Generation on the Ancillary Services and the Unit Commitment Process for an Isolated System A. Papalexopoulos, I. Vitellas, N. D. Hatziargyriou, C. Hansen, T. Patsaka, A. Dimeas, IEEE ISAP September 2011 Hersonissos Crete, Greece. [4] Security and Economic Impacts of high Wind Power Penetration in Island Systems, N.D. Hatziargyriou, A. Dimeas, D. Georgiadis, A. Tsikalakis, J. Stefanakis, A. Gigantidou, E. Thalassinakis, CIGRE, Paris, 30 August-3 September [5] Anemos.plus EU funded research project. Web Page: [6] Safewind EU funded research project. Web Page: 8