Optimization of the diesel photovoltaic isolated system installed in the Nazareth community using wind energy.

The objective of the work is the optimization of the isolated and hybridized electric power generation system with photovoltaic technology and genset, installed in the village of Nazareth belonging to the municipality of Uribia, Colombia. The optimization criteria established in this study consists of respecting what is already installed and from there propose various search spaces in HOMER Energy to find the optimal system configuration, the main idea is to minimize the consumption of diesel fuel through the inclusion of a wind system. two optimal scenarios are proposed, the first minimizes the participation of the genset to 10%, the second proposes a system of 100% renewable energy generation. Based on the results of the study, it is concluded that the system proposed in scenario C is the most pertinent alternative, It is concluded that the system proposed in scenario C is the most relevant alternative, because the system has 90% autonomy without the generator set.


Introduction
Renewable energies have currently been supported worldwide by many countries, cataloging them as a means of generating healthy energy for the planet [1].The installation of this type of technology is very flexible because it can be adapted to local conditions and is used mostly to supply power to remote places with difficult access [2].The consumption of renewable energy in the world has been increasing by 2.3% since 2015, which means that global carbon emissions associated with renewable energy remained stable in 2014, while the world economy grew [3], such favorable effects are attributed to the use of renewable energies and improvements in energy efficiency.
According to the US Energy Information Administration (EIA) International Energy Outlook 2013, the current world demand for primary energy is 546.8 quadrillion Btu (546.8 × 10 15 Btu) and is projected to reach to nearly 820 quadrillion Btu by 2040.Global energy consumption of electrical power is estimated to double in the next 15 to 20 years.China, India, Morocco, and Chile, among other countries, are projected to increase their electricity consumption in the next two decades [4].
Part of the Colombian national territory is not covered by the interconnected energy system.Most of the Non-Interconnected Zones (ZIN) meet their energy needs through Diesel generators, which implies a high cost in fuel transportation and equipment maintenance, the energy supply in vulnerable communities is only available approximately 4 hours a day [5].As pointed out by the 2012 global energy competitiveness study, conducted by the Choiseul institute and Kpmg."Power generation in Colombia is one of the pillars of economic development" [6].Colombia is a country with great natural wealth such as hydro potential, gas and coal, it also has wind and solar resources and the use of biomass, the abundance of natural resources is evident.Some studies carried out reveal the different areas of the country where there is a great variety of renewable resources, which can be used for energy production [7].
The energy demand has registered an increase since 2001 with rates that oscillate between 1.5% and 4.1% per year, the national territory has a multiannual daily solar average close to 4.5 kWh/m2, where the peninsula of La Guajira stands out with a average of 6.0 kWh/m2 and wind speeds equal to 5 m/s reaching 11m/s [8].Although Colombia has energy wealth, currently it only has one wind farm installed; Jepirachi Park, located near Cabo de la Vela in La Guajira.Public Companies of Medellín (EPM) was in charge of its installation and started up since April 2004 [9].According to a report delivered by EPM, the wind speedsof the place are favorable almost all year round, isolated winds coming from the east-west with low intensityof turbulence.The park is made up of 15 wind turbines manufactured by NORDEX, a German company, each with 1.3 MW of power, which is equivalent to 19.5 MW of total power [9].
Years ago, the community of Nazareth had a generator power generator, in 2011, the company ADES proposed to the Institute for Planning and Promotion of Energy Solutions for Non-Interconnected Areas (IPSE) a consistent solution to minimize the operation of the generator set, through the incorporation of renewable energy sources (wind and solar) in the existing system.The proposal proposed incorporating two 100 kW ADES pivoting single-blade wind turbines at a height of 20 m, a 100kW photovoltaic park with tracking, a battery bank and three generator sets totaling 250 kW of power.The system was installed, according to the local press and technical reports from the IPSE, the wind technology presented problems in its operation, currently only the photovoltaic system and the Diesel generator are operating [10].
La Guajira is a beautiful department with great natural wealth, it has great marine wealth and resources from nature such as mineral coal, natural gas, gypsum, barite, sea salt, gold, marble, clay, and limestone among others.Geographically it is the northernmost territory of Colombia and South America.It is characterized by being a border department with an area of 20,848 km2 and to the north it has 354 kilometers of coastline [11].
La Guajira is the fifth largest department in the Caribbean region, representing 15.7% of the region's area (132,083 km2) and 1.8% of the country's area (1,140,667 km2) [12].It is between 10º23' and 12º28' north latitude and 71º06' and 73º39' west longitude, with temperatures ranging between 22°C and 40°C [12].It is divided into 15 municipalities and 142 populated centers between police supervision, townships, and villages, organized into three sub-regions known as Alta, Media and Baja Guajira.Some towns belonging to Alta Guajira currently suffer from problems due to lack of electricity.Then renewable energies are a possible solution to the energy problem.Many of the rural areas are far from the urban area with complicated access roads.For this reason, there is no connection to the network and these areas do not have electricity service.Some example communities are Nazareth and Puerto Estrella, which are located in the municipality of Uribia in La Guajira, more than eight hours away by land.Over the years the population of La Guajira has been increasing considerably, studies carried out by DANE record important figures in population growth.For the year 2008, the records estimate 763,439 inhabitants, of which 351,182 were indigenous.For 2016 there is evidence of a considerable increase of 985,452 people, which is equivalent to 1.99% of the national population, with indigenous people occupying 46% of the population, Afro-descendants 8.2% and without ethnicity 45.9 % [13].
The Institute for Planning and Promotion of Energy Solutions for Non-Interconnected Areas (IPSE), is the organization that meets energy needs by identifying, implementing and monitoring sustainable energy solutions, with criteria of efficiency and effectiveness in Non-Interconnected Areas -ZNI, improving the living conditions of its inhabitants.The IPSE is a Public Institution of National Order, which provides its services in Colombia, with its own assets and administrative autonomy.

Methodology
The main objective of the study is the optimization of the hybrid system installed in the community of Nazareth, to solve the energy problem that occurs in the towns of Nazareth and Puerto Estrella, using the HOMER Legacy software as a design tool.
The hybrid system supplies energy 5 hours a day to the community, because the generator set (Diesel generator) is not in operation due to lack of fuel, which indicates that the photovoltaic array is responsible for supplying energy, the problem It lies in the lack of resources for the purchase and transfer of fuel in the system's facilities.The study focuses on the community of Nazareth.Located a few meters from the Serranía de la Macuira with a Latitude of 12.1833 and a Longitude of -71.2833 with a height of 77 meters above sea level.It is a territorial settlement 8 hours from Uribia by land with a 204 km journey.Figure 1 shows the geographical location of the town of Nazareth.The production data and the technical characteristics of the system were supplied directly by the Institute for Planning and Promotion of Solutions for Non-Interconnected Areas (IPSE), information found in its databases, subsequently, the climatological and geographical analysis of the location, information that was provided by the National Monitoring Center (CNM).

Population demand
The register of the energy demanded by the population is determined by knowing the average number of people in the place and the possible energy consumed by each dwelling.The study carried out by the National Administrative Department of Statistics (DANE) states that between the towns of Nazareth and Puerto Estrella there is an average of 2000 inhabitants [13].Based on the reports provided by the IPSE, the system installed in the community of Nazareth provides service to more than 250 users in Nazareth and 200 in Puerto Estrella, in addition, it reports the daily average of the energy demanded by the community, which is of 3,931 kWh/day as shown in Figure 2.
Therefore, to characterize the hourly demand profile, the average number of hours per day in which the installed system supplies electricity is defined.To determine the hours of operation of the system, the data compiled by the IPSE is used, where it establishes that the system supplies energy to Nazareth and Puerto Estrella approximately 5 hours a day.Once the average number of daily hours is obtained, the consumed energy profile is defined.Since the operating time of the system only goes back to an average of five hours per day, there is no total data on the energy demanded by the community.For this reason, we proceed to interpolate the actual production data of the system with the hours of operation.To determine the total demand of the population for all months.Table 1 shows the results obtained in the study, where the monthly and annual average demand is shown.

System simulation in HOMER software
For the simulation in HOMER, the following parameters were defined: the population demand profile (kW), monthly average wind speeds (m/s) and solar radiation (kwh/m2/day) for a year, altitude of the place (masl), solar panel capacity (kW), generator set capacity (kW), wind turbine power (kW), converter power (kW), storage system sizing.
Internally HOMER found the combination of components that satisfy the electrical loads, simulated thousands of system configurations, and generated analysis results for the input data.He made an energy balance for each of the 8,760 hours of the year.Comparing the electrical load with the energy that the system can deliver in one hour.In addition, it analyzed how each component of the system operates and the state of loading and unloading of the storage system.Figure 4 shows the main HOMER Energy window.

Case 1: System Description
The National Monitoring Center for research provided data on wind and solar potential for the years 2017 and 2018 of the community of Nazareth, the IPSE provided reports on the energy production of the system, the information showed the daily average of energy demanded, the which was compared with the production and the established population demand profile.The system is made up of the 320 kWp photovoltaic array, the storage system of 480 batteries each of 3350 Ah 2V, 30 Sunny Island 8.0H inverters, 28 Sunny tripower 12000 TL 10 inverters and a 364kW diesel generator set.nominal.In addition, it has a three-phase interconnection line between Nazareth and Puerto Estrella of 18.5 km and a voltage level of 13.2 kV.
The storage system is made up of the charging inverters and the battery bank, in total there are 30 inverters divided into 10 branches.Each branch is made up of three investors.Each group of inverters is connected to a circuit of two parallel battery branches, with 24 cells each (48 cells in total).Which is equivalent to a total of 20 battery strings.It should be noted that in scenario B the same system is proposed without the operation of the generator set. Figure 5 shows the electrical plan of the system proposed in scenario A, showing the dimensioning of the main components and the power distribution, achieving a complete visualization of the system in the simplest way.Knowing the configuration of the system installed in Nazareth, a search space is defined in HOMER, expanding the photovoltaic matrix to 1,735 panels, 912 batteries and three wind turbines of 100 kW each, maintaining the same Diesel generator.Table 2 shows all the components of the system, the capacity, the brand and the number of equipment.Figure 6 shows the electrical plan of the simulated system in HOMER Energy referring to scenario C, where the sizing and parts of the main components are shown, the distribution of power from the source to the utilization equipment, in order to achieve a complete visualization of the system in the simplest way.Due to the desire to reduce the use of Diesel in the system, the search space is expanded, leaving the system composed of the photovoltaic matrix system of 2,017 panels, 1,248 batteries and four wind turbines of 100 kW each.Table 3 shows the configuration, capacity and number of equipment proposed in scenario D.

Results
Through the simulation carried out in HOMER, the energy production of the system referring to case 1 is determined.In scenario A, the system has a total production of 1,636,036 kWh/year, 28% of the production is from the photovoltaic array and 72% for the generator set, supplying the total demand of the population, the excess energy evidenced is 0.39%.The generator set consumes 401,177 L/year of Diesel fuel, which is equivalent to 3,607 h/year of operation.Table 4 compares the monthly production data for scenarios A and B, broken down by component.

Optimal system, case 2
In scenario C, the total production of the system is 1,921,545 kWh/year, 32% of the total production corresponds to the photovoltaic array, 58% to the wind system and the remaining 10% to the generator set, with an amount of fuel consumed of 64,166 L/year and 603 h/year of operation, showing an excess of energy of 13%. Figure 7 shows the monthly average of energy produced by each technology discriminated by colors.As seen in figure 8, the PV and wind systems supply the demand most of the time.The generator set runs for a few hours per day, indicating that the system's reliance on diesel power has been significantly reduced.
The state of charge of the system shows 593,078 KWh/year of input energy and 511,063 KWh/year of output energy, with a range of 23.4 h and a nominal capacity used of 3,830 KWh. Figure 8 shows the hourly profile of energy produced by each system component for two days in January.In scenario D, energy production of 2,302,734 kWh/year, the wind system contributes 65% of the total production and the photovoltaic array 35%.Presenting an excess of energy of 28.4%, which represents 877,892kWh/year.Figure 9 shows the energy profile produced by components.The storage system is robust, which has an autonomy of 32 hours, with a nominal capacity of 7,408 kWh, usable nominal capacity of 5,242 kWh. Figure 10 shows the state of charge of the storage system throughout the year.

Discussion
This study proposes a solution to the energy problems suffered by the towns of Nazareth and Puerto Estrella, which focuses on the lack of resources of the municipal entity (Mayor's Office of Uribia) for the monthly purchase and transportation of Diesel fuel required by the plant for its operation.The results obtained from the simulated system in scenario A, when compared with the energy production of the system provided by the IPSE (scenario B), show a considerable energy deficit and the importance of the generator set for the optimal functioning of the system.
However, when the system is optimized in scenario C, it shows a favorable scenario to solve the problem, considerably reducing the energy production of the generator set.In scenario D, an alternative solution is proposed where the generator set only supports the system if a fault occurs.Comparing the data obtained in scenarios C and D, energy production satisfies the population's demand.

Conclusions
The simulations carried out made it possible to identify and analyze the energy problems of the communities of Nazareth and Puerto Estrella.Through the processing of wind and solar data from the location, the energy potential was satisfactorily determined, averaging 8,760 data and identifying the months and hours of the year 2017 where there is the greatest resource.It was useful to determine the population demand profile for indigenous dwellings, identifying the hours when there is the greatest energy demand.
With the optimization carried out in scenario C, the main advantage it has with respect to the system in scenario A. It is the reduction of the dependence of the system on generating energy through diesel fuel, due to the integration of wind technology, the expansion of the photovoltaic array and the battery bank.
On the other hand, the configuration proposed in scenario D is a tempting alternative, because it would not be necessary to have monthly resources for the purchase and transportation of fuel, another aspect to consider is the dimensioning of the system, which is more robust compared to the one proposed.in scenario C, the surplus of unusable energy is added to this.Therefore, the optimal configuration is the one proposed in scenario C, where the generator set only operates 603 h/year, considerably reducing fuel consumption, which leads to having few resources for its acquisition, the system has a 90% capacity.autonomy without the generator set, carrying out a controlled supply plan, the energy conditions of the towns of Nazareth and Puerto Estrella would change positively.

Figure 1 .
Figure 1.Location of the site: Nazareth, Guajira.(Taken from Google Map)

Figure 3
Figure 3 shows the population demand profile, where three energy peaks are evidenced where more energyis demanded, being between 200kWh and 260 kWh.

Figure 3 .
Figure 3. Hourly demand profile of the communities of Nazareth and Puerto Estrella

Figure 6 .
Figure 6.Single-line diagram of the simulated system at HOMER Energy, scenario C

9 Figure 7 .
Figure 7. Monthly average of energy produced by the system

Figure 8 .
Figure 8. Hourly profile of energy produced by each component of the system for two days

Figure 9 .
Figure 9. Profile of energy produced by components

Figure 10 .
Figure 10.Load status of the storage system.

Table 1 .
Monthly demand of the community of Nazareth and Puerto Estrella

Table 2 .
Description of the components of scenario C

Table 3 .
observe the configuration, capacity and number of equipment proposed in scenario D

Table 4 .
Comparison of production data for scenarios A and B