Analysis of Economic-Technical Potential of Renewable Power Sources for the Establishment of National Renewable Energy Center in Ninh Thuan Province, Vietnam

Currently, Vietnam‘s energy source structure is being changed by which renewable energy sources play more important role to meet the electricity demand and reduce greenhouse gas emissions from fossil energy sources. Vietnam’s energy development strategy determines to build some renewable energy centers, of which Ninh Thuan is the first province designated to become a national renewable energy center. This is based on Ninh Thuan’s endowment as a province having the largest renewable energy potential in Vietnam. Development of a large renewable energy center allows power system planners to overcome the mismatch in timescales associated with developing transmission power grid and renewable energy generation. Besides, renewable energy center can facilitate a significant pipeline of large-scale renewable energy and storage projects. However, Ninh Thuan province is far away from the major load centers of Vietnam so the calculation and analysis of economic indicators need to be studied. This paper will present the results of the analysis of economic indicators of major renewable electricity sources in Ninh Thuan (onshore wind power, offshore wind power, solar power) to provide scientific arguments for developing a renewable energy center in Vietnam. Also the paper addresses the problem of the large-scale penetration of renewable energy into the power system of Vietnam. The proposed approach presents the optimization of operational decisions in different power generation technologies as a Markov decision process. It uses a stochastic base model that optimizes a deterministic lookahead model. The first model applies the stochastic search to optimize the operation of power sources. The second model captures hourly variations of renewable energy over a year. The approach helps to find the optimal generation configuration under different market conditions.


Introduction
The overall global renewable power capacity increased to around 2,378 GW by the end of 2018 and achieved more than 33% of the world's total installed power generating capacity [1]. An estimated new renewable power capacity of 181 GW was installed worldwide in 2018, in which, the total capacity of solar power accounted for 55% of renewable capacity additions, followed by wind power (28%) [1]. The power system can receive a large proportion of renewable energy without using fossil fuels and nuclear power with the role of running "baseload", based on the flexibility of the electricity system, power grid connection, advanced technology solutions such as ICT (Information and communications technology), power storage systems and virtual power plants. It is not only helping to balance the change in the electricity generation stage but also optimizes the power system and reduces generation costs. As a result, some countries successfully control peak loads or surpassing the target of 100% of electricity produced from renewable energy.
There is a huge difference between renewable energy centers (wind and solar power) and traditional power centers such as a thermal power center in a national power system.This is because the peculiarities of its primary energy source. When developing a thermal power center, the preferred conditions for choosing a location are near large load centers or strong power grid or infrastructure (coal ports, for example). In the case of the renewable energy (RE) center, the preferred condition is the geographical areas with high solar radiation or good wind speed and efficiency in land use. This leads to the challenges of synchronizing and optimizing the transmission and distribution grids so that RE resources can be fully utilized in the considered geographical areas to reduce transmission losses as the load centers are usually far from the RE source. Vietnam's energy development strategy determines to build some renewable energy centers, of which Ninh Thuan is the first province designated to become a national renewable energy center as the province has the largest renewable energy potential in Vietnam. The national renewable energy center established in Ninh Thuan will play an important role in supporting the development of the renewable power industry in Vietnam.
However, Ninh Thuan province is distanced from the major load centers of Vietnam so the calculation and analysis of economic indicators need to be studied. This paper will present the results of the analysis of economic indicators of major renewable electricity sources in Ninh Thuan (onshore wind power, offshore wind power, solar power) to provide scientific arguments for developing a renewable energy center in Vietnam.

Geographical site
Ninh Thuan, located in the southern part of Vietnam Central Coastal region, borders Khanh Hoa in the north, Binh Thuan in the south, Lam Dong in the west, East sea in the East.
The province has total natural surface of 3,360 sq. kilometers, 7 administrative units including 1 city and 6 districts. The city of Phan Rang -Thap Cham, as provincial city, constitutes a political, economic and cultural center of the province, distant from Hochiminh City by 350 km, from international Cam Ranh airport by 60 km, from the city of Nha Trang by 105 km and from Da Lat by 110 km with favorable conditions for circulations in service of socio-economic development.

Solar energy potential
Ninh Thuan is located in an area with the annual average solar radiation of about 5.5 kWh/m 2 .day, the average number of sunshine hours is about 2,600-2,800 hours per year (equivalent to 200 sunny days/year), and a total solar power installation scale of about 1,500 MW. In Ninh Thuan, the area of Ninh Phuoc district and Thuan Nam district where having large solar energy potential can be effectively exploited [13].

Wind energy potential
Ninh Thuạn province also has the largest wind power potential in Vietnam with the annual average wind speed of about 7m/s at the height above 65m. The whole province has 14 potential wind regions with about 8,000 ha, concentrated mainly in three districts of Ninh Phuoc, Thuan Nam and Thuan Bac. Especially, storms in Ninh Thuan is not much and the wind blows steadily for 10 months at a speed of 6.4 -9.6 m/s, ensuring stability for wind power development. The technical wind power potential and the highly feasible area of Ninh Thuan are 1,442 MW with 21,642 ha [14].

Methodology
In this study, the electricity of solar farm is calculated by using PVSYST program [16, 17] while the output from wind turbine is determined by using design data of wind farm projects in planning of wind power development in Ninh Thuan [14]. The economic potential was determined by considering the annualized investment costs and the annual O&M costs. The goal is the calculation of the minimum Feed in tariff (FIT) level. Currently, the level of FIT can be calculated on the basis of a calculation of the levelized cost of electricity (LCOE) produced from renewable energy (RE) projects [19]. By which, the investor can recover the different costs (capital, O&M, fuel, financing) while realizing a return on his investment that depends on the assumed financing costs. LCoE has been utilized to assess the average lifetime costs of providing one MWh for a range of power production technologies or power savings. The cost elements comprising the LCoE include investment costs, fuel costs, operation and maintenance costs, environmental externalities and system costs for solar and wind power plants. LCoE is given by the following formula: (1) In which: I t : investment cost by the year t M t : Operation and Maintenance cost by the year t F t : Fuel cost by the year t E t : Electricity production by the year t r: discount rate n: project lifetime (year)

Results
The key parameters are used for the calculations are shown in Table 1. The LCOE or minimum FIT of major renewable electricity sources in Ninh Thuan (onshore wind power, offshore wind power, solar power) is evaluated in Table  2.  Figure 5 presents the comparison results between minimum FIT of onshore wind power, offshore wind power, solar power projects in Ninh Thuan with existing Vietnam FIT of these projects in Vietnam. The min FIT of onshore wind power in Ninh Thuan is closer with Vietnam FIT than solar power and offshore wind power.

Generation expansion planning
The planning models are the traditional tool to analyse future developments in the energy sector. The capacity planning problem in the power systems has been divided into demand forecasting, distribution expansion The GEP models can be classified according to time horizon (static and dynamic), handling of uncertainties (deterministic and stochastic), network topology (the single-node or centralised and network constrained), and market structure (regulated and deregulated) [20].
The GEP is usually an optimisation problem in which the aim is to distinguish the optimal size, type of generation unit, and commitment time of new generating facilities so as to satisfy the power demand at least cost over a planning horizon [20].

Generation expansion planning with high share of renewable energy
The RE resources create for the power systems' operation some operational challenges for GEP due to the following feature of their stochastic nature [24-26]:  RE variability requires flexible generation that can ramp up and down quickly,  The intermittency makes the output from RE sources uncertain.
 Power quality and voltage stability issues connected with RE variability that needs to be assessed, controlled, observed and mitigated appropriately, These three aspects (variability, intermittency, and grid stability issues) necessitate a paradigm change in GEP models that assess the impact of increased penetration of RE [27][28][29]. Traditional GEP models have mostly focused on the conventional power plant whose