Issues in PV systems applied to rural electrification in Brazil

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser

Issues in PV systems applied to rural electrification in Brazil a,⁎

a

a

MARK a

b

L. Roberto Valer , Alex. R.A. Manito , Tina B. Selles Ribeiro , Roberto Zilles , João T. Pinho a

Instituto de Energia e Ambiente, Universidade de São Paulo, Av. Prof. Luciano Gualberto 1289, CEP 05508-010 São Paulo, Brazil Grupo de Estudos e Desenvolvimento de Alternativas Energéticas (GEDAE), Universidade Federal do Pará (UFPA), Campus Universitário do Guamá, CEP 66025-772 Belém, Brazil b

A R T I C L E I N F O

A BS T RAC T

Keywords: Rural electrification Solar home systems Solar micro-grids

In Brazil, the access to electricity is a right of all their citizens. The Brazilian government has endeavored to extend the electric grid wherever technically and economically feasible. For the remaining sites, PV systems can be a feasible option that is enforced by federal laws, standards and subsidies. For this reason, unlike other countries where renewable energy systems are donated or commercialized by NGOs and other entities, in Brazil these systems are mainly installed by utilities, making the country a unique case for study. This paper analyzes the main problems faced by PV systems for rural electrification. The methodology is based on field observation and literature survey. As a result, several issues of demand to be supplied, installation, operation and maintenance, and post-installation were identified. From these observations, it is clear that a greater attention should be payed to the management of the whole electrification project, by clearly delimiting the goals and the responsibilities of each stakeholder, and ensuring that the goals are met.

1. Introduction Access to electricity is closely associated with human development. The potential benefits that may arise from rural electrification projects are many, and have strong influence on increasing the Human Development Index (HDI) of a community in the early stages of its development [1]. Despite this, a considerable portion of the world's population still lacks access to electricity and the benefits it can bring. According to the World Energy Outlook 2012 [2], at that time almost 20% of the world's population did not have access to modern energy and still used traditional energy sources such as wood, kerosene, and candles to meet their energy needs. In Brazil, although access to energy is a right of all citizens established by law 10,438 [3], according to the last census [4], around 716,000 homes did not have access to electricity. Brazil started addressing rural electrification mainly through conventional grid extension, prioritizing those locations closer to larger cities from which the grid could be easily extended. This was done due to reasons such as the lower average marginal cost of providing the service, and the higher expertise of the utilities with this type of service. Connection to the existing grid, however, is not possible for many remote and isolated communities, due to logistic, environmental and geographic factors. Isolated communities also often have low load density, not justifying the costs and environmental impacts of the grid extension.

⁎

To address this issue, some alternatives have been proposed, such as the use of diesel generators or on-site electricity production with renewable energy sources. The former, despite the relatively low initial investment, presents some difficulties associated with fuel transportation logistics, sensitivity to oil price fluctuations, and high life cycle cost. Renewable energy sources, in this case, seem to be the most appropriate, constituting not only a less expensive option (when the whole life cycle cost is taken into account), but also a more environmental friendly solution. The fact that it avoids the logistics of fuel transportation is a feature that reduces not only financial costs, but also simplifies the project by being more dependent on on-site resources. Moreover, the renewable energy systems usually have decreasing costs as the technologies become more widespread. Unlike other countries where renewable energy systems are donated or commercialized by NGOs and other entities, in Brazil they are currently installed mainly with funds from the Brazilian government through its electrification program called Luz para Todos (Light for All). As the grid extension reaches its feasible limit, alternative solutions for the supply of small isolated communities become more important in rural electrification. The utilities have experienced high grid extension costs [5,6], and in many cases grid extension is not feasible at all. In this context, photovoltaic (PV) systems are considered one of the main technologies for electrification of isolated sites as presented in [7]. It is already a mature technology, and although a lot of research on

Corresponding author. E-mail addresses: [email protected] (L.R. Valer), [email protected] (A.R.A. Manito), [email protected] (T.B.S. Ribeiro), [email protected] (R. Zilles), [email protected] (J.T. Pinho).

http://dx.doi.org/10.1016/j.rser.2017.05.016 Received 12 December 2016; Received in revised form 11 April 2017; Accepted 4 May 2017 1364-0321/ © 2017 Elsevier Ltd. All rights reserved.

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

83/2004 [18] by the Agência Nacional de Energia Elétrica - ANEEL, the Brazilian regulatory agency for electric energy. This normative regulated the use of renewable energy systems called Sistemas Individuais de Geração de Energia Elétrica com Fontes Intermitentes - SIGFI (Individual Electric Energy Generation Systems with Intermittent Sources), which could be defined mainly as SHS. In 2009, the MME and ELETROBRAS published the Manual de Projetos Especiais (Special Projects Manual) [19] to address situations in which grid extension was not possible due to peculiarities of the site to be electrified. That document establishes the technical requirements and responsibilities of the utilities. By then, it was clear that universalization could not be achieved by grid extension alone, and other measures needed to be taken to support alternative solutions. The use of micro-grids was considered in that document, among other strategies. In 2012, ANEEL published RN 493/2012 [20] which updates RN 83/2004 [18], and also includes regulation for isolated micro-grids called Microssistema Isolado de Geração e Distribuição de Energia Elétrica - MIGDI (Isolated Microsystem for Electric Energy Generation and Distribution). Before 2012, solar micro-grids were installed as pilot projects, mainly in the Amazon region. According to [21], nine solar micro-grids were installed in Brazil between 1996 and 2008. Between 2011 and 2012, twelve solar micro-grids were installed in the state of Amazonas, and four solar micro-grids in state of Pará [22]. Although the goal of electrification for all citizens had not yet been met, important results were achieved. Fig. 1 presents the connections made by the LpT program from 2004 to 2014, as published in the 2015 Statistical Year Book of Electricity, an annual report published by the MME [23]. There is a decreasing trend in the number of connections to be made under the LpT program. The data also shows that only the Northern and North-eastern regions still have a relatively high number of connections to be made. At the end of 2014, when the program was postponed, the Brazilian government estimated that 207,000 families still lacked access to electricity, 30,000 of which live in isolated sites [24] in which grid connection would be difficult to implement, usually due to difficulties in reaching the remaining sites.

its use in rural electrification projects is reported in several papers, such as [8–12], there are still many challenges concerning project implementation, due to some peculiar situations, which make experience sharing still important. This paper addresses problems encountered by PV systems installed in Brazil as an alternative to rural electrification, and attempts to provide some insights into risk points. Many of the PV systems that have been installed encountered problems of different types. There seems to be a gap between the potential benefits of PV systems applied to rural electrification and the actual results. Issues faced by solar home systems and micro-grids, as well as elements that proved to be good approaches to the management of such systems are presented and discussed. Although it is difficult to establish a single formula to address the problem, the insights commented here may constitute important points in the decision making process. The methodology is based on field observation and literature survey. Although the paper focuses on PV systems, many of the conclusions could be useful to other renewable energy systems. The paper is organized as follows: first, the history of rural electrification with PV systems in Brazil is briefly summarized in Section 2; common configurations for PV systems are described in Section 3; and in Section 4, risks with PV systems are discussed. Finally, discussion and conclusion sections of this work are presented in Sections 5 and 6. 2. Rural electrification with PV in Brazil The first significant use of PV systems for the electrification of homes, schools and community centers in Brazil dates back to the mid1990s when many systems were installed by power distribution companies, public bodies and NGOs. The Programa de Desenvolvimento Energético de Estados e Municípios – PRODEEM (Program for Energy Development of States and Municipalities), during its six phases (1996–2001), installed 5,914 SHSs, 2,449 PV pumping systems and 379 PV lighting systems. Accounting for a total of 5.2 MWp of installed capacity, the PRODEEM was an important initiative for the dissemination of renewable energy sources such as PV systems, helping the understanding of some peculiarities of SHSs in the Brazilian territory. Nevertheless, issues such as lack of funds for spare parts, inadequate plans for monitoring and maintenance, and low coordination with other policies for promoting the development of the national industry hampered the results of the program [13,14]. In 2004, the Ministério de Minas e Energia - MME (Ministry of Mines and Energy) launched the Revitalization and Training Program [15] in order to diagnose problems in the installed systems, repair them and empower local users and technicians to keep those systems running. Other programs, including “Luz do Sol”, “Eldorado”, “Luz solar” and “Produzir”, installed more than 34,000 systems until 2002 [16]. In 1999, the Programa Luz no Campo (Light in the Countryside Program) was created, which provided electricity to 700,000 rural families. The majority of these connections were made by grid expansion, although some experiments were also carried out with SHS. For instance, according to [17], 3,144 SHSs were installed in the state of Bahia. In 2002, the Brazilian Law 10,438 [3] established access to electricity as a right of all citizens. According to the referred law, every citizen who requested electricity service should be supplied without being charged for the connection. One year later, Decree 4873 introduced the Luz para Todos program (LpT) with the objective of supplying 100% of the Brazilian population until 2008 (The LpT program did not achieve its goal by 2008, and has been postponed three times. Currently the deadline for the program is 2018, and it is restricted to the electrification of isolated communities via off-grid systems). Although the LpT approach mainly involved grid extension in its first years, the need for alternative solutions was already an official concern in 2004, with the publication of the normative resolution RN

3. Types of supply in Brazil and common configurations In Brazil, the obligations of the utilities may vary with the type of consumer to be supplied. The consumers addressed in this paper are those located in what is called “The Remote Regions of the Isolated Systems” (RRIS), which are defined as small groups of consumers located far from urban centers and characterized by low population density and lack of economy of scale. Table 1 presents the conditions of supply for this group, as stated in RN 493/2012 [20], and also those for consumers supplied by grid extension, in order to compare their main differences and contrast some of the rights of rural dwellers in the Brazilian context. One of the main differences presented in the table is energy supply availability between the two classes of consumers, which can restrict the use of electric energy for consumers in the RRIS.

Fig. 1. Number of connections of LpT over the years (adapted from [23]).

1034

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

Table 1 Summary of RN 493/12 [20] and RN 414/10 [25]. Source: ANEEL Supplying of the individual systems and micro-grids (RN 493/12)

Energy supply Energy availability

Daily number of hours of supply Metering Meter reading interval

Billing Payment interval Consumer Unit Interruption Duration CUIDI Load upgrade request

Individual system

Micro-grid

Only AC or Mixed (DC and AC) Limited by power installed

Only AC (pure sinewave)

Conventional supply (RN 414/10)

Only AC (pure sinewave)

The utility can place a limiting mechanism according to the projected values for each household Eight hours at minimum but the utility must justify why a 24-h supply is not possible Optional It could be made at intervals up to 12 consecutive cycles

The utility can issue payment slips with the first delivery of 12 billing cycles Can be monthly, every two months or quarterly, according to consumer choice Monthly: 216 h (9 days) Annual: 648 h (27 days) This can be done once a year and only to the extent of an individual system or micro-grid whose monthly availability of energy is a maximum of 80 kWh

Solar home systems and micro-grids are two commonly used options for rural electrification. Both options are now regulated by RN 493/2012 and are supposed to offer the same service with the same quality, making the option for one alternative over the other dependent on the particularities of each case (such as capacity to be installed and feasibility for installation). Several works present technical-economic comparisons between SHS and solar micro-grids i.e. [26,27]. The following subsection presents the two options for electrification with PV to be addressed in this paper in more detail.

There are no limitations; however, the protection system must be in accordance with the contracted demand 24 h Mandatory Monthly. But in rural areas it can be made at intervals up to 12 consecutive cycles if the consumer informs the reading. Otherwise, the utility must perform the reading every three consecutive cycles Monthly Monthly Monthly: 4–52.7 h Annual: 16–104.34 h It can be requested anytime

Source 1

Source 2

3.1. Solar Home Systems (SHSs)

Source 1

DC coupling

Power conditioning unit

AC coupling

Source 2

Source N

Source N

Battery bank

Load

Fig. 3. SMG common configuration.

SHSs are basically composed of PV modules, electrochemical storage systems (batteries), charge controllers and inverters. Fig. 2 presents a schematic of the described system. The PV modules generate the energy which is stored in the batteries or used by the loads. When the primary resource is not available, the batteries supply the load. In households far from urban centers or in widely scattered communities, SHSs avoid transmission losses in distribution, and the construction and maintenance of transmission lines and distribution grids. The modularity and simplicity of these systems make them a suitable choice for the electrification of single households.

renewable energy technologies, are flow-based rather than stock-based, a dispatchable backup source is desirable to increase reliability. Fig. 3 presents the configuration of a generic SMG. SMGs are more complex than SHS due to the magnitude of the system; however, they can benefit from demand factors (the installed power of the system can be smaller than the sum of the powers of individual intermittent systems, due to non-simultaneous use of the loads), increased efficiency of the employed equipment, better levels of reliability, and smaller generation costs than individual systems.

3.2. Solar Micro Grids (SMGs) 4. Issues in the supply of isolated locations The Solar Micro Grids (SMGs), as defined in this paper, are electricity distribution grids powered partially or totally by PV generators. Among the several topologies with different types of sources and couplings (DC-coupled, AC-coupled, or both), a common configuration employs a grid forming inverter, a maximum power point tracker, batteries, and a dispatchable energy backup source (for instance, a diesel generator). Since PV systems, as well as other

Communities have different characteristics, such as habits, cultures and values. It is hard to generalize and prepare a unique project to perfectly suit them all. It is necessary to observe the peculiarities of each community and to understand how energy would satisfy their demand. However, some degree of standardization should exist, to simplify the implementation and institutionalization of the procedures by the service providers. Thus, finding the optimum point between simplicity and quality of service is one of the great challenges of rural electrification projects. Rural electrification projects deal with risks due to the uniqueness of their situations. It is noteworthy that rural electrification has characteristics that go beyond the mere choice and dimensioning of components involved in generation and distribution, and is influenced even by the culture of the community that is to receive the service. Therefore, the minimal expenditure point of view cannot be the only

Fig. 2. SHS common configuration.

1035

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

aspect pursued in decision making. Doing so assumes idealized scenarios which most often do not take place, and allows little flexibility to provide the service in the face of difficulties. Due to all the risks involved and the cost and time associated with maintenance, rural electrification needs to be effective rather than just efficient. The whole project should be seen as a network of related processes (some in series and some in parallel) with clearly assigned responsibilities. Understanding how the processes are interconnected is of utmost importance before the actual implementation. Thus, the funding, personnel, spare parts, and even modularity for eventual increases should be accounted for in the whole project from its very beginning. For instance, three isolated SMGs in the state of Pará, Brazil are addressed in [28], where the main difficulties reported were the maintenance of the systems, especially after the end of the funding period from the development agencies, which demonstrates the issue of project management. Putting the system into operation is one step, but keeping the system running is just as important and relatively more difficult. A lack of sustainability may result in systems with a false appearance of success. At the system level, sustainability would guarantee the operation and the continuity of the service year-round, during the system's life. It is unrealistic to think that the system will not face any problems during its entire lifetime, since many issues influence the choice, dimensioning and actual implementation of the electricity generation system, and the risks should be accounted for in each of these aspects. The following subsections present risk points found during field observation and in the literature review. The issues presented refer to the demand to be supplied, installation, and postinstallation issues of PV systems installed mainly in Brazil.

Table 2 Energy supply according to RN 493/2012 (adapted from [20]). Guaranteed monthly energy (kWh/month)

Daily consumption (Wh/day)

Minimum autonomy (h)

Minimum inverter power (W)

13 20 30 45 60 80

437 670 1,000 1,500 2,000 2,650

48 48 48 48 48 48

250 250 500 700 1,000 1,250

electrification programs in the world i.e. [8–12], if a project aims to receive funds from the Conta de Desenvolvimento Energético - CDE (Account for Energetic Development - a fund for the universalization of electricity supply) it currently needs to provide a minimum of 45 kWh per consumer per month. This amount is based on the assumption that it would be the minimum required for the service provider to supply at least lighting, communication and refrigeration demands. Since generating energy through PV is expensive and the consumers in isolated communities have low capacity for paying for the service, the systems are, on many occasions, dimensioned to meet a particular demand, with little flexibility for load increase. This feature, however, represents a high risk. Load increases can be quite high and hard to evaluate, even when surveys to estimate consumption are conducted before the actual system implementation. Moreover, in rural electrification, there is mutual influence between demand and supply. When electrification comes, communities may experience a transient phase in which their energy requirements may change considerably due to the purchase of new appliances, the transition of traditional end-uses to electricity powered ones, and even the displacement of new settlers to the community. The relatively small population also presents challenges by producing large variations in the load on a daily basis. In the case of SHSs, for instance, the purchase of a single new appliance may render the generation system unsuitable. In such a context of uncertainty, being able to respond quickly to changes in demand is just as important as estimating the actual demand, and the modularity of the system plays an important role to allow lower expenditure in the face of adequacies to unaccounted situations. PV is a technology with many modular solutions of generators available on the market. These solutions support the addition of generation capacity without having to change the whole system in the case of SMGs. In the case of SHSs, the limitation in the modularity is the inverter's rating capacity. Usually, stand-alone inverters for small systems cannot be connected in parallel. One solution could be oversizing the inverter and adding PV modules and batteries based on demand needs. In addition to increasing generating capacity, other approaches can be used to maximize the available resources, such as matching the generation with the load, the use of efficient appliances, or reducing conversion losses. However, these approaches should be carefully evaluated, so as not to present more of a problem than a solution. Keeping the project as simple as possible to reduce risk is a good practice. In the case of load shifting, certain activities such as water pumping can be shifted to match periods of abundance of the primary resource. However, there is some degree of time-shifting possibility for certain activities, since it is not possible to match the generation to the load at all times. Usually, the best options for load shifting are those that do not influence the daily activities of the households (for instance, water pumping or ice production). The use of more efficient appliances, and even DC appliances, to avoid conversion losses, depend on their availability in the market. Currently in Brazil, such a practice would represent more of a risk than a solution. The systems should be sized to supply the appliances more likely to be available in the market. There is a high risk that consumers

4.1. Demand to be supplied Consumers in urban areas and those supplied by SHSs or SMGs have different views on the use of electricity. The former seem to be more concerned about their monthly bill than with the supply, since for them the supply is virtually infinite. The latter, however, are more concerned about supply, since it is limited. Determining the amount of electricity that would satisfy energy needs while being sustainable and price affordable for remote communities is a challenge, and marketbased solutions are limited because many rural consumers cannot afford the real energy costs. There is great diversity of electricity needs among rural consumers, even within the same community, resulting in oversized systems for some, and unsatisfactory systems for others. It was noted in the field that most consumers have low consumption profiles, while a small portion have high consumption, even comparable to those of costumers in urban centers. These profiles are also reported in [29], which states that the consumption of a particular community has a similar behavior to a Gamma distribution. It is possible to find studies in the literature reporting a wide range of different needs and consumption levels. For instance, [29] shows that only 10 kWh would be enough to supply most consumer units in certain communities, and [30] comments that 60% of the SHS consumers in three Amazonian communities consume less than 7 kWh per month. In one of these communities, half the population consumes less than 2 kWh per month on average. However, 13 kWh would be insufficient for other consumers, for the use of some appliances such as motors and pumps, designated for special demands, such as food refrigeration and productive uses [31,32]. According to [33], a monthly availability higher than 30 kWh is needed to power refrigeration appliances, considering the climatic conditions expected in warm areas like the Amazon. Table 2 presents the monthly availability of energy and system autonomy that systems installed by utilities have to meet according to RN 493/2012 [20]. Despite the minimum Brazilian energy availability (13 kWh/month) being higher than that established by other rural 1036

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

accounted for to avoid bottlenecks. On many occasions it is necessary to count even on the support of local people to transport the equipment. Fig. 5 shows the transportation of equipment to an isolated community in the state of São Paulo, Brazil. In isolated sites the cost of the generated energy is more influenced by other factors (such as maintenance and fuel transportation), aside from the purchase of the components of the generation system itself. In such cases it is more important that the system be robust to avoid failures as much as possible, since the allocation of resources tends to increase with the isolation. In systems located in very remote places, the quality and robustness of the installation is of great importance. Maintenance trips to remote locations are very costly and savings can be achieved by reducing the failure rate by providing better services. In PV systems, the components that offer the most risk during transportation are the batteries. Although they are modular, they are usually heavy, fragile and cannot be stored without use for long periods (months), requiring proper coordination from the purchase phase to the operation phase. Other components, such as the PV modules, power conditioning equipment, distribution poles and transformers (in the case of SMGs) do not depreciate as fast as the batteries, but still face problems during transportation. In the case of SMGs, which usually use diesel generators, the price and transport of diesel also pose a risk to proper operation.

will replace efficient technology, when it fails or wears out, with conventional technology [34]. For instance [35], found that it is possible to use a 30 kWh SHS with an imported high efficiency refrigerator. However, the author recommends the use of a 45 kWh SHS with refrigerators available on the national market, even if they are less efficient, due to the lower risks regarding maintenance and market availability. The use of DC appliances also offers the risk at an informational level, since the final user has to be informed that the conventional technologies more likely to be found on the market cannot work with the DC power source. Previous experiences [30,36] show that DC appliances are not available in most rural regions in Brazil. 4.2. Installation, operation and maintenance problems Brazil should not be seen as a homogeneous country. Regional differences affect the availability of professionals and equipment, which usually need to be hired/purchased in the South-eastern region, incurring extra costs of transportation and lodging. It is unlikely that the implementation capacity and maintenance of a project in different places be the same, if there is a gap in the technical knowledge of the professionals and the availability of equipment in the local markets. This creates different boundary conditions, which may mean different results for similar projects. Indeed [26], reported that the maintenance costs associated with isolated systems were about three times more expensive than the estimated value, for a project in the state of Acre. According to that work, the additional costs are attributed to factors such as the high number of technical visits, organizational issues, and insufficient training of local staff. This creates a gap between the estimated and the actual operation cost of isolated systems, and renders the system unsustainable according to the estimated budget during the planning phase. The following subsections address site access, capacity building, equipment quality and installation standards.

4.2.2. Capacity building According to the World Bank report from 2010 [37], the proper and effective design of rural electrification programs requires technical and management skills that are not always present. Therefore, countries committed to expanding access to electricity need to go through an initial process of developing strategies and training. Each stage of a project needs professionals with specific training and resources to perform the required activities, and supervision capacity to verify whether the activities are conducted properly is also needed. It is useless to spend large amounts of money without qualified personnel to perform the tasks, having qualified technicians who lack the resources to perform their activities, or even a skilled team that can meet only a small portion of the demand. Projects designed this way are usually doomed to failure and resources are inefficiently spent. Each professional involved should act in a coordinated manner, which increases the chances of success and the service provided per unit cost. In addition, the consolidation and institutionalization of the capacity building process makes the provision of the service more robust to personnel changes and other interferences. When it comes to PV systems, the technical teams from the utilities are usually unfamiliar with its specificities. This situation creates a bias regarding which kind of system is to be used, increasing the risk of using technologies that would otherwise be the most unsuitable. This lack of skilled labor to work in the sector is one of the obstacles for PV systems deployment in Brazil. This is not restricted to the operation of SHSs and SMGs; even grid connected systems still face some issues. However, in isolated systems this problem is aggravated by factors such as the increased number of components involved, difficulties due to the use of equipment from different manufacturers and difficulty in maintaining/bringing specialized personnel in/to remote areas. Moreover, the consequences of the systems not working in rural electrification are more severe, for this represents the loss of the service itself. The lack of professionals in remote areas creates a barrier to the system, especially during the operation phase. Some papers refer to people from the community itself performing some tasks and helping with the assemblage and maintenance of the generation system [38]. Although it is desirable to have a person from the community to perform some simple tasks, the use of non-trained personnel can be a dangerous approach, both for the person and the system itself, and the person in charge needs to have proper training, even for simple tasks. It should also be borne in mind that from the household supply point of

4.2.1. Site access Many communities are located hundreds of miles away from urban centers. On many occasions, these sites are difficult to reach, making the grid extension approach less suitable and, in some cases, not viable at all. In rural electrification projects, the access logistics needs to be thoroughly evaluated, since it directly influences the costs of installation, maintenance, operation and monitoring of the systems. Reaching isolated sites often involves multimodal transportation and requires a large amount of time (sometimes days), which implies a higher expenditure of personnel and resources per household to be electrified. The site access logistics can be viewed as a problem involving displacing personnel and equipment over a physical environment during a period at a particular time. Accounting for this time is necessary, since some access routes may not be available along the year. The transport of personnel and equipment frequently needs the displacement of boats and other vehicles, warehousing and lodging, which may vary significantly from case to case, resulting in different generation costs for similar generation systems. The transportation of equipment has a big impact on the costs of isolated systems installed in Brazil. Moreover, the response time for solving problems is also increased for isolated sites. Fig. 4 presents similar SHSs in two different seasons of the year. In the wet season, the system can only be accessed by boat. The lack of infrastructure and particularities of a region, especially in the Amazon region, imposes additional difficulties and risks. These sites are largely unserved by roads and even when they exist, they sometimes cannot be relied on. Transportation often needs to be improvised due to the lack of infrastructure for the most commonly used vehicles. In some parts of the journey, the weight and volume of equipment, as well as the weight and volume of the vehicles, need to be 1037

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

Fig. 4. Views of SHSs in an Amazon community during the dry and wet seasons.

Fig. 5. View of community people helping transport the equipment.

habits, education, and the proper training of the personnel in charge of dealing with the local population. The absence of interaction between service provider's personnel and final users can cause risk or negative perceptions of the PV System [40], resulting in barriers to sustainability. 4.2.3. Equipment quality The use of poor quality equipment to lower costs in the short term may result in huge expenditures on maintenance, to the point of practically reinstalling the system on some occasions. Several projects implemented in Brazil [13,26,30,41] and in other countries [42,43] reported problems related to the bad quality or inadequate use of some components. In PV systems the components that pose the highest risk are the batteries. They are expensive and have a relatively short lifetime, which is directly affected by the average depth of discharge. [42] states that the batteries represented the highest proportion of the total system cost in an evaluation of several isolated systems. Performing quality tests on the components of isolated PV systems, except for the PV module itself, is not mandatory in Brazil. However, the utilities can demand (and in the case of funding from the CDE they must demand) i.e. [44,45] that the equipment meets the specifications in document RAC 004/2011 [46], which evaluates conformity against specific criteria. The equipment to be tested, as referred to in the above mentioned document, are batteries, charge controllers, off-grid inverters (between 5 W and 10 kW), and PV modules. Bidirectional inverters are not yet considered in the tests, although efforts are being made to create standardized tests for these components. The tests address normal operation as well as stress conditions (such as overloads or harsh environments). Currently, six Brazilian and three foreign laboratories are certified to conduct the tests. Table 3 shows the number of components that have a registration with the Instituto Nacional de Metrologia – INMETRO (National Metrology Institute). Since only the tests for PV modules are mandatory, and they are also used in grid-connected systems, there are many available models compared to the other components. The lack of components is also attributed to the number and the type of tests that the RAC 004/ 2011 demands for charge controllers and off-grid inverters. For

Fig. 6. Burned connector in a PV module connection box.

view, the system is not different than the urban grid (the voltage magnitude is the same), and some components, especially the batteries, need to be handled carefully by trained technicians. Fig. 6 shows a case of poor installation seen in field, in which the PV module cable was not properly tight and created a hot spot, burning the contact. Capacity building is not restricted to the technicians hired to install and maintain the system. The interface with the final user needs to be properly addressed at every channel available between the final user and the utilities, including the call centers that deal with requests from the consumers. For instance, in the state of São Paulo there are cases in which the attendant is not prepared to deal with a situation on a remote island, not understanding the user's claim, which results in long delays and causes frustration [39]. The systems have a better chance of success, if their capabilities and use are understood by the final user. Although the interaction of the final user with the generation system should be kept to a minimum, guidelines on how to use the system correctly (e.g. not beyond its limitations) are of utmost importance. A better dissemination of information depends on local specificities such as culture, values, 1038

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

sional, with less disturbance to the project from personnel replacement. The lack of standards, however, creates greater deviation around what to expect from a system's configuration and makes them harder to be evaluated. When it comes to PV systems for rural electrification, there is no set of standards exclusively written for this purpose in Brazil, and each utility has its own guidelines for installation and commissioning. Nevertheless, some national standards may apply fully or partially to rural electrification projects, such as NBR 15389 [48], which deals with lead-acid batteries, and NBR 16274 [49] that, despite being thought of for grid-connected systems, can be partially used for commissioning. Where there are no national standards, international standards may serve as guidelines, such as the IEEE std 1526 [50], the IEC 62257 [51] series, and the IEC 62124 [52]. In addition to the electrical installation of the PV system itself, the electrical installations in the consumer units should also be considered by the utilities. In field observations, it is not uncommon to encounter poorly made installations, which offer risks to the users and to the system itself. In many communities it was noted that the electrical installations of consumer units did not have switches, circuit breakers, or any protection devices, which is a hazard, and inefficient energy use. Fig. 7 shows electrical installations found in the field, where it is possible to see precarious conditions. A common practice in particular, found in many households, is the use of plastic bags as insulating tape, as shown in Fig. 7. The utilities seeking to use funds from the CDE must provide electrical installations for the consumer unit. These electrical installations need to have a minimum of three lighting points and two power outlets. However, one must notice that a lesser number of outlets and lighting points will not keep the final user from using appliances and will even encourage users to modify their electrical installation. The lack of outlets also encourages the use of outlet multipliers and extensions, like the ones depicted in Fig. 7, which may put much stress on a single part of the electric circuit. Norm NBR5410 (the Brazilian norm for low voltage electrical installations) [53] recommends at least one lighting point per room and one outlet, where the area of the room is smaller than 6 m2. Where the area of the room is larger, there should be one outlet per 5 m or fraction of the perimeter. Providing a good installation inside the consumer unit can be seen as an investment in the system itself. In this way, the utility can lower risks due to poorly executed installations.

Table 3 PV components with the Programa Brasileiro de Etiquetagem - PBE (Brazilian Labeling Program) label (adapted from [47]). Equipment

Models

Companies

PV modules Off-grid inverters Solar batteries Charge controller

504 2 25 –

183 2 2 –

instance, it requires that off-grid inverters have efficiencies higher than 80% for any load condition and higher than 85% for loadings above 50%. However, low efficiency of the converter does not represent a problem itself (although it could represent a higher energy price), since the designer only has to account for it in the dimensioning of the batteries and PV generator to provide the desired levels of energy and power. Less efficient equipment should be phased out only when there are superior products available on the market, which can be easily found off-the-shelf. The tests should thus focus mainly on safety and robustness as a first stage, and then increase the requirements as more equipment is brought onto the market. The lack of models with active registration increases the possibility of low quality or inappropriate equipment being employed in systems. For example, stationary batteries for solar applications are not available in remote regions, and other types of batteries, such as automotive, are sometimes used to replace them. Moreover, equipment that meets the quality standards lower risks, because the designer at least has a notion of what the equipment can withstand and how it would perform in the field, given the design conditions. In addition to the quality of the equipment itself, and its price, other aspects should be taken into account in the purchase phase, such as the existence of technical support from the manufacturer, and availability of the equipment in the country, to avoid situations in which products must be ordered months in advance because they are not readily available. Lack of availability on the national market should be avoided as much as possible to lower risks during operation and simplify maintenance. Moreover, the use of standardized topologies facilitates the acquisition of spare parts for the systems and may decrease the price of the purchase due to economy of scale. Although it is true that the lack of flexibility to address certain unique situations represents a problem, the total lack of standards in the approaches increases the risks. 4.2.4. Installation quality and applicable standards In order to make the project more robust, the adoption and even the creation of technical standards is necessary. Technical standards are based on the expertise of a community of professionals and are thought to deal with the most common situations in the most suitable (or at least in the most agreeable) way. Standards consolidate some of the expertise needed to conceive a project that would otherwise be the responsibility of an individual or a small team, and can even make the implementation less dependent on the expertise of a particular profes-

4.3. Post-installation In order to keep the system running, the post-installation phase must be carefully considered. The strategies that the service provider adopts will affect the operation and maintenance costs of the system. The suitability of the strategies employed may vary greatly, depending on the peculiarities of the system and the site of installation. The next subsections discuss the monitoring and the billing of isolated PV systems.

Fig. 7. Modifications in internal installations made by some SHS users.

1039

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

Table 4 Advantages and disadvantages of billing types (adapted from [55]). Billing types

Advantages

Disadvantages

Fixed Tariff

1. Low implementation cost 2. Operational simplicity

Metering

1. Low implementation cost 2. Electricity consumption is regulated trough the user´s payment capability 1. Consumption can be adjusted depending on user needs 2. Possibility to purchase extra credits 3. Operational cost reduction through the use of smart meters 4. No payment default

1. Low control against excessive electricity consumption 2. High rates of payment default when the person in charge of the collection is a member of the community 1. High operational costs (energy meters reading, disconnection and reconnection, billing)

Prepaid

1. High implementation cost 2. Need for special infrastructure for operation (sales agents for credits recharge, mobile communication services for remote sale, etc.)

curve, when it comes to the probability of a failure occurring, postinstallation assessment is necessary to find problems that may have passed unnoticed during the installation phase. After the initial stage, the system enters more stable operation, and the probability of failure diminishes until it increases again due to the natural wear of the equipment.

4.3.1. Monitoring Monitoring allows improved preventive maintenance, better planning and improved response time for maintenance in the case of a system failure, which could save resources in the long term. Through monitoring, the utility can evaluate whether the systems still perform the way they were conceived, and even gain improved knowledge about their operation, whereas the lack of monitoring can result in premature failure of a system due to suboptimal operation or abnormal deterioration. Monitoring can also be a way of measuring whether the goals are being met or whether they were properly selected (meeting the goal does not mean solving problems). In Brazil, the only obligation of the utilities regarding system monitoring is the collection of data that would eventually be transformed into the CAIDI (Customer Average Interruption Duration Index) indicator for the sake of evaluating the utility itself, concerning the service it provides [20] (this index is called Duração de Interrupção Individual por Unidade Consumidora - DIC in Brazil). Table 1 presents the requirements of service quality that should be delivered by the systems installed by the utilities in Brazil. However, this index is hard to be realistically evaluated. Interruption only begins to be accounted for when the user reports it to the utility, but the interface between the consumers and the utility is, on many occasions, precarious and hard to use [31,39]. Monitoring of isolated sites is difficult, due to the lack of infrastructure present on site and, depending on the parameters to be monitored, it can also be expensive. Monitoring often cannot be performed continuously, due to the lack of media to transmit data or the expensive cost of a possible solution. In those cases, the data collection should be done during the scheduled preventive maintenance or payment collection. In SHSs, the equipment that needs monitoring the most is the battery bank, and most of the parameters of interest can be acquired from the charge controller. In bigger systems, like SMGs, it is a good practice to acquire several parameters from the system, which are usually provided by the bidirectional inverters. The objectives of the monitoring must be thoroughly evaluated to transform the data into useful information. Algorithms to quickly process the data and evaluate the situation of the system according to some objective are necessary, otherwise the amount of data could be cumbersome to work with, resulting in no actual benefit from the monitoring. A good practice is the use of an algorithm to run most of the analyses but also record the raw data, so that in the case of uncommon situations this data can be analyzed more deeply by specialists. By analyzing the data, many elements can be evaluated before having to spend resources on trips to the locations, and may even discover what is affecting the performance of the system, which could result in a trip with improved chances of solving the problem. This feature would have a direct impact on the reliability of the system and the maintenance costs. Monitoring is especially important immediately after the installation of the system. Since installations follow a trend called the bathtub

4.3.2. Billing In [54] it is stated that adequate billing and metering are essential to the sustainability of rural electrification projects. However, billing also represents cost to the utilities, and enforcing payment is not always cost effective. Moreover, enforcing payment can also present difficulties. In situations in which billing is too cumbersome, the utility often prefers not to charge and leaves the systems unsupervised. According to [55] three types of billing are applied by utilities in Brazil: fixed energy tariff, billing according to energy consumption, and prepaid systems. In fixed energy tariff, a value is set by the utility to be paid during a period, disregarding consumption. In the second type of billing, the amount to be paid is based on the energy consumed, which can be either estimated or actually metered according to the utility criteria. The third type, prepaid systems, is not officially allowed yet, but was implemented in three projects. In this case, the consumer purchases a card to be used in the energy meter, which enables a certain amount of energy to be consumed [55,56]. Table 4 presents the advantages and disadvantages of each type of billing. In systems installed by other agents, such as NGOs, other strategies can be applied. For instance, in the Aiucá community, electrified via SHS, billing was a contribution to a fund agreed to be paid by the community for spare batteries and other equipment, managed by the community itself. According to [32], this case faced problems in buying new batteries, due to debts and mismanagement. Most isolated communities cannot pay the real costs for the electricity service. As a result, social tariffs are available in Brazil for low-income consumers [57]. These tariffs allow discounts of 65% of the electricity bill for families whose consumption is less than 30 kWh per month, 40% for families with consumption between 30 and 100 kWh per month, and 10% for families with consumption less than 220 kWh. A special case is that of Indian tribes and quilombola communities, where the discount can be up to 100%. For these reasons, rural electrification projects are usually not profitable. However, billing in this case can play a different role. It can act as an instrument of control to avoid excessive or inefficient use, thus protecting the system itself. The amount to be paid should be set to a point that does not keep the final user from using the energy, but at the same time creates some responsibilities regarding its use. The complete lack of charges leads to energy waste, which is aggravated in the cases of SMGs, in which the energy is shared among all consumers in a community. One solution could be to allow an amount of energy for free, and charge the excess, not limiting those that consume more (and usually can pay more) and not penalizing those who consume little. Billing could coincide with preventive maintenance and monitor1040

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

schedule. Moreover, without mechanisms to monitor and ensure whether or not the goals are met by each stakeholder, all the documentation regarding service quality and rights of the consumers is no better than a manual of good practices. Since rural electrification is usually cumbersome for some of the stakeholders, solutions based on market approaches are limited and enforcing the law is even more necessary, for it is the only mechanism that would protect the consumer.

ing, to lower resource expenditure. According to RN 493/2012 [20], the utilities in Brazil can use electricity limiting devices to keep users from consuming above a stipulated limit. However, field observations showed that the imposition of this limit and the consequent denial of the service, in the case of SMGs, has consequences such as illegal connections to the distribution grid, which can result in the premature collapse of the generation system, by making it work constantly beyond its normal design conditions.

6. Conclusion 5. Discussion By making access to electricity a basic right of all its citizens, Brazil has promoted several rural electrification programs in recent decades, and created some specific regulations. A large number of new connections were made by extending the power grid, but due to the problems already mentioned the new facilities were to be made using locally available sources. PV systems are a proven technology and one of the most suitable for the supply of remote communities, due to their modularity and resource availability. However, the lack of profitability, which is usually a characteristic of rural electrification projects, imposes risks which cannot be disregarded. Denying, or not dealing with such risks creates a negative perception of PV systems to the society, and may even represent large and inefficient expenditures of resources. This paper addressed some issues found in field observations of PV systems for the supply of remote communities. This is a reality far from being restricted to the Brazilian case. The specialized literature presents many papers that report rural electrification projects in other countries, which faced similar problems to those found in Brazil. Problems such as system costs [61], premature failure [59], abandoned systems [43], issues in site access logistics [59], poor or unavailable maintenance [59,62,63] and unrealistic cost estimation [42,64] are some of the most reported issues. Furthermore, it is noteworthy to mention that a successful electrification program will not necessarily lead to development. The increase in life quality depends on several issues of multidisciplinary nature, and the electrification system may be just a part of it. Some studies [59,65] suggest that without a broader approach, mere electrification generates little or no development at all. It is clear from these observations that greater attention should be paid to the management of the whole electrification project, by clearly delimiting the responsibilities and the goals of each stakeholder, and ensuring that the goals are met. It is important to note, however, that despite the problems observed in the field, the Brazilian rural electrification program is one of the most ambitious in the world, and has several merits, having already reached the majority of the rural population. In this regard, many of the related problems may be solved by the improvement of current standards, and the demand of society and specialized entities for proper enforcement of these aspects.

In a context where there is little or even no profitability for the enterprise, clear, feasible and enforceable regulations are necessary to guarantee the provision of a service. If rural communities could afford the electricity service, then rural electrification would be a supplydemand issue [58], which would probably be solved by itself. In most cases, however, systems need to be installed in an environment not empowered to pay for the service, which in turn creates an impasse between service quality and system cost. Many problems in rural electrification projects can be found via observation in the field, especially related to the non-sustainability of the enterprise. Even with subsidies from the Brazilian government, the utilities are required to optimize costs, and little attention is paid to the sustainability of the entrepreneur. Although optimization is desirable, it is much more important to account for the risks and the uncertainties of the enterprises. Reducing the uncertainty for technology designers and decision makers is important, and without information, it can only be done by increasing the robustness of the system, or improving the response time to address problems which, in turn, usually represent higher investments. Currently, systems usually have little flexibility to operate under adverse conditions, which are likely to happen during the whole project's lifetime. [59] states that it is useless to refine the dimensioning of the systems in a scenario of complete uncertainty. Proper optimization needs proper and realistic assumptions, which on most occasions cannot be made due to the lack of studies for that purpose. It is important not to base a project on idealized scenarios that are not likely to occur, because doing so is more expensive due to excessive maintenance and sometimes even results in the complete replacement of the system. For instance [42], reports that the underestimation of maintenance cost is a cause of failure of projects in rural electrification programs. In such situations, the systems need to be robust rather than efficient, as mentioned above. Current Brazilian legislation places too much importance on the implementation of the systems and little focus on the operation phase. Operation costs, even with PV systems that demand relatively low maintenance, are comparable to that of the installation of the systems and, depending on the level of isolation, can be even higher. It is also important to properly delimit and define the goals of the project and the roles of the stakeholders. The objectives of the stakeholders are different, due to different interests, and they should not be confused. Doing so leads to a blurred attribution of responsibilities, poor accountability and poorly achieved results. For instance, in Brazil, the view that utilities take regarding the electrification of isolated communities is usually that they are providing electricity to such communities according to the current regulations. The utilities do not see this as bringing development. As pointed out by [60], they are utilities, not development agencies, and aside from the obvious fact that this is not profitable, the utilities also lack the expertise and experience to perform such a multidisciplinary task. The goals of each stakeholder should be inputs for subsequent phases in a coordinated manner, which will eventually lead to the goal of the project. The regulations should be feasible and enforceable. Feasibility should be a real concern; it is important not to set unrealistic schedules that cannot be fulfilled by the utilities. Doing so results in systems that lack quality and sustainability and are designed mainly to meet a

Acknowledgements This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Grant Number 573997/2008-0). References [1] Gómez Maria F, Silveira Semida. Rural electrification of the Brazilian Amazon – achievements and lessons. Energy Policy 2010;38:6251–60. http://dx.doi.org/ 10.1016/j.enpol.2010.06.013. [2] IEA (International Energy Agency). World Energy Outlook 2012. 2013. Available at: 〈http://www.worldenergyoutlook.org/weo2012/〉, [accessed 13 April 2016]. [3] Governo Federal, Lei 10348 04/26/2002. Brazil. Available at: 〈http://www. planalto.gov.br/ccivil_03/leis/2002/L10438.htm〉, [accessed 15 May 2016]. [4] IBGE (Instituto Brasileiro de Geografia e Estatística). 2010 census. Available at:

1041

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al. 〈http://www.censo2010.ibge.gov.br/〉, [accessed 4 July 2016]. [5] Andrade Celia Salama, Rosa Luiz Pinguelli, da Silva Neilton Fidelis. Generation of electric energy in rural isolated rural communities in the amazon region a proposal for the autonomy and sustainability of the local populations. Renew Sustain Energy Rev 2011;15:493–503. http://dx.doi.org/10.1016/j.rser.2010.09.052. [6] Gómez Maria F, Silveira Semida. Delivering off-grid electricity systems in the Brazilian Amazon. Energy Sustain Dev 2012;16:155–67. http://dx.doi.org/ 10.1016/j.esd.2012.01.007. [7] Nerini Francesco Fuso, Howells Mark, Bazilian Morgan, Gomez Maria F. Rural electrification options in the Brazilian Amazon. A multicriteria analysis. Energy Sustain Dev 2014;20:36–48. http://dx.doi.org/10.1016/j.esd.2014.02.005. [8] Cabraal Anil, Cosgrove-Davies Mac, Schaeffer Loretta. Best practices for photovoltaic household electrification programs: lessons from experiences in selected countries. World Bank Technical Paper number 324, Asia Technical Department Series; 1996. [9] Nieuwenhout FDJ, Van Dijk A, Lasschuit PE, Van Roekel G, Van Dijk VAP, Hirsch D, Arriaza H, Hankins M, Sharma BD, Wade H, Cabraal Anil, Cosgrove-Davies Mac, Schaeffer Loretta. Experience with solar home systems in developing countries: a review. Progress Photovolt: Res Appl 2001;9:455–74. http://dx.doi.org/10.1002/ Pip.392. [10] Debajit Palit. Solar energy programs for rural electrification: Experience es and lessons from South Asia, Energy for Sustainable Development, Volume 17, Issue 3, June, Pages 270-279, ISSN 0973–0826, http://dx.doi.org/10.1016/j.esd.2013.01. 002; 2013. [11] Miguel Carrasco Luis, Narvarte Luis, Lorenzo Eduardo. Operational costs of a 13,000 solar home systems rural electrification programme. Renew Sustain Energy Rev 2013;20:1–7. http://dx.doi.org/10.1016/j.rser.2012.11.073. [12] Baurzhan Saule, Jenkins Glenn P. Off-grid solar PV: is it an affordable or appropriate solution for rural electrification in sub-Saharan African countries?. Renew Sustain Energy Rev 2016;60:14051418. http://dx.doi.org/10.1016/ j.rser.2016.03.016. [13] Marco A. Galdino, Jorge H. G. Lima. PRODEEM – The Brazilian program for rural electrification using photovoltaics.RIO 02 World Climate & Energy Event, Rio de Janeiro, 2002; 1: p. 77–84. [14] Tribunal de Contas da União. Avaliação do TCU sobre o Programa Energia das Pequenas Comunidades / Tribunal de Contas da União. – Brasília: TCU, Secretaria de Fiscalização e Avaliação de Programas de Governo. 22p. (Sumários Executivos/ TCUSEPROG; 10); 2003. [15] Ministério de Minas e Energia. Plano de Revitalização e Capacitação do PRODEEM. 2004. [16] Winrock International Brazil. Trade Guide on Renewable Energy in Brazil. U.S. Agency for International Development; Bureau for Economic Growth, Agriculture and Trade (EGAT) Office of Energy; Energy Program USAID/Brazil, Brazil, 2002. [17] Hugo Machado Silva Filho. Sistemas Fotovoltaicos: universalização do serviço de energia elétrica na Bahia. Eduneb; 2012. [18] Agência Nacional de Energia Elétrica. Resolução normativa N° 83. 2004. [19] Ministério de Minas e Energia. Manual de projetos especiais. 2009. [20] Agência Nacional de Energia Elétrica. Resolução normativa N° 493. 2012. [21] Pinho, JT. et al. Sistemas Híbridos. Soluções Energéticas para a Amazônia. Ministério de Minas e Energia; 2008. [22] Pinho JT, Galdino MA. Manual de Engenharia para Sistemas Fotovoltaicos. CRESESB; 2014. [23] Ministério de Minas e Energia, Statistical YearBook, 2015. Available at: 〈http:// www.epe.gov.br/AnuarioEstatisticodeEnergiaEletrica/Anu%C3%A1rio%20Estat% C3%ADstico%20de%20Energia%20El%C3%A9trica%202015.pdf〉, [accessed 15 April 2016]. [24] Programa Luz para Todos. Official website. Available at: 〈https://www.mme.gov. br/luzparatodos/Asp/o_programa.asp〉, [accessed 7 September 2016]. [25] Agência Nacional de Energia Elétrica. Resolução normativa N° 414. 2010. [26] Guilherme Fleury Wanderlay Soares, Leonardo dos Santos Reis Vieira, Marco Antonio Esteves Galdino, Marta Maria de Almeida Olivieri, Eduardo Luis de Paula Borges, Claudio Monteiro de Carvalho, Alex Artigiani Neves Lima. Comparação de custos entre sistemas fotovoltaicos individuais e minicentrais fotovoltaicas para eletrificação rural. III Congresso Brasileiro de Energia Solar, Belem, Brazil; 2010. [27] Chaurey A, Kandpal TC. A techno-economic comparison of rural electrification based on solar home systems and PV microgrids. Energy Policy 2010;38:3118–29. http://dx.doi.org/10.1016/j.enpol.2010.01.052. [28] Luis Carlos Blasques, Silvio Bispo Vale, Alternativas para a Sustentabilidade de Sistemas de Geração de Energia com Fontes Renováveis em Comunidades Isoladas. VI Encontro Nacional sobre Edificações e Comunidades Sustentáveis. Vitória, 2011. [29] Morante Federico, Zilles Roberto. Electric consumption in SHSs in rural communities of Brazil and Peru and recommendations for sizing. Progress Photovolt 2008;16(2):171–9. http://dx.doi.org/10.1002/Pip.790. [30] Bispo do Vale Silvio, Blasques LuisCarlosMacedo , Carvalho CláudioMonteirode, Borges Eduardo Luisde Paula, Nascimento Maia Felipe, A experiência obtida com os projetos de geração com fontes renováveis de energia na região norte do Brasil: do PRODEEM aos Projetos Especiais das concessionárias. IV Congresso Brasileiro de Energia Solar; 2012. [31] Andrade Cristiane Brito. Qualidade do fornecimento de energia elétrica em sistemas isolados segundo o parâmetro de continuidade DIC. MSc. thesis. Programa de Pós-graduação em Energia. Instituto de Energia e Ambiente, Universidade Federal do ABC; 2011. [32] Valer L Roberto, Mocelin Andre, Zilles Roberto, Edila Moura A, Nascimento Claudeise S. Assessment of socioeconomic impacts of access to electricity in Brazilian Amazon: case study in two communities in Mamirauá reserve. Energy Sustain Dev 2014;20:58–65. http://dx.doi.org/10.1016/j.esd.2014.03.002.

[33] Márcia Ramos, Leonardo Vieira, Marco Antônio Galdino, Marta M.A. Oliveiri. Avaliação de sistemas fotovoltaicos isolados tipo SIGFI alimentando refrigeradores. In: Proceedings of the XXIII Seminário Nacional de Produção e Transmissão de Energia Elétrica. Foz de Iguaçu, 2015. [34] Simon Rolland, Guido Glania. Hybrid mini-grids for rural electrification: lessons learned. Alliance for Rural Electrification (ARE), Brussels, Belgium, 2011. Available at: 〈https://www.ruralelec.org/sites/default/files/hybrid_mini-grids_for_rural_ electrification_2014.pdf〉. [35] Gustavo Pires da Ponte, Gabriel Malta Castro, Thiago Ivanoski Teixeira, Danilo de Brito Lima. Avaliação do suprimento através de SIGFI30 e SIGFI45 em função do atendimento a cargas de refrigeração em regiões remotas. In: Proceedings of the XXIII Seminário Nacional de Produção e Transmissão de Energia Elétrica. Foz de Iguaçu, 2015. [36] Roberto Valer L., Tina Bimestre Selles Ribeiro, André Mocelin, Roberto Zilles. Lições aprendidas no processo de implantação de sistemas fotovoltaicos domiciliares em duas comunidades rurais. Revista Brasileira de Energia Solar, 5 (2014) pp. 18-26. [37] World Bank. Addressing the Electricity Access Gap. 2010. Available at: 〈http:// siteresources.worldbank.org/EXTESC/Resources/Addressing_the_Electricity_ Access_Gap.pdf〉, [accessed 15 April 2016]. [38] Rahman Md Mizanur, Paatero Jukka V, Poudyal Aditya, Lahdelma Risto. Driving and Hindering Factors for rural electrification in developing countries: lessons from Blangadesh. Energy Policy 2013;61:840–51. http://dx.doi.org/10.1016/j.enpol.2013.06.100. [39] Ribeiro Tina Bimestre Selles. Sistemas fotovoltaicos e a experiência do programa Luz para Todos em São Paulo [Doctoral thesis]. Programa de Pós-graduação em Energia. Instituto de Energia e Ambiente, Universidade de São Paulo; 2015. [40] Karakaya Emrah, Sriwannawit Pranpreya. Barriers to the adoption of photovoltaic systems: the state of art. Renew Sustain Energy Rev 2015;49:60–6. http:// dx.doi.org/10.1016/j.rser.2015.04.058. [41] Zilles Roberto, Lorenzo Eduardo, Serpa Paulo. From candles to PV electricity: a four-year experience at Iguape–Cananéia, Brazil. Prog Photo: Res Appl 2000;8:421–34. http://dx.doi.org/10.1002/1099-159X(200007/08)8:4 < 421::AID-PIP323 > 3.0.CO;2-J. [42] Luis Miguel Carrasco, Luis Narvarte. Operational cost and reliability in a large rural electrification programme based on solar home systems. In: Proceedings of the 28th European Photovoltaic Solar Energy Conference and Exhibition, pp 3831– 3835. http://dx.doi.org/10.4229/28thEUPVSEC.2013-5DO.13.6; 2013. [43] Hong George Willian, Abe Naoya. Sustainability assessment of renewable energy projects for off-grid rural electrification: the Pangan-an Island case in the Philippines. Renew Sustain Energy Rev 2012;16:54–64. http://dx.doi.org/ 10.1016/j.rser.2011.07.136. [44] ELETROBRAS. Especificações técnicas dos programas de atendimento às Regiões Remotas dos Sistemas Isolados no âmbito do programa Luz para Todos. Ministério de Minas e Energia, 2015. [45] Companhia Energética do Ceará. Especificação Técnica ET-194/2014 R-00 Sistema individual de geração de energia elétrica com fonte intermitente - SIGFI 2014. [46] INMETRO. Requisitos de Avaliação da Conformidade. 2011. [47] Instituto Brasileiro de Metrologia. Website. Available at: 〈http://www.inmetro.gov. br/consumidor/pbe/sistema-fotovoltaico.asp〉, accessed 07/05/2016. [48] Associação Brasileira de Normas Técnicas. NBR 15389 – Bateria chumbo-ácida estacionária regulada por válvula - Instalação e montagem. 08/07/2006. [49] Associação Brasileira de Normas Técnicas. NBR 16274 – Sistemas fotovoltaicos conectados à rede — Requisitos mínimos para documentação, ensaios de comissionamento, inspeção e avaliação de desempenho. 06/03/2014. [50] Institute of Electrical and Electronic Engineers. IEEE Std 1526 – IEEE recommended practice for testing the performance of stand-alone photovoltaic systems. 2003. ISBN 0-7381–3828-2 SH95177. [51] International Electrotechnical Commission. IEC 62257 – Recommendations for renewable energy and hybrid systems for rural electrification. 2012. [52] International Electrotechnical Commission. IEC 62124 – Photovoltaic stand-alone systems – design verification. 2004. [53] Associação Brasileira de Normas Técnicas. NBR 5410 - Instalações elétricas de baixa tensão. 09/30/2004. [54] Niez A. Comparative study on rural electrification policies in emerging economies— keys to successful policies. International Energy Agency; 2010. [55] Blasques Luis Carlos Macedo. Otimização de sistemas híbridos para a eletrificação de minirredes com fontes renováveis: aspectos de projeto, operação e gestão. Doctoral thesis. Programa de Pós-graduação em Engenharia elétrica. Instituto deTecnologia, Universidade Federal do Pará; 2014. [56] Claudomiro Fabio de Oliveira Barbosa, João T. Pinho, Marcos André Barros Galhardo, Diego Pereira Cruz, Rodrigo Guido Araújo. The experiences with the application of the first electricity prepayment system in Brazil installed at an isolated community in the Amazon Region. In: Proceedings of the IEEE Transmission and Distribution Conference and Exposition: Latin America, 2004, São Paulo, Proceedings USA: IEEE, 2004. p. 663–668. [57] Governo Federal. Lei 12212. 01/20/2010. Brasil. Available at: 〈http://www. planalto.gov.br/ccivil_03/_Ato2007-2010/2010/Lei/L12212.htm〉, [accessed 6 April 2016]. [58] Lahimer AA, Alghoul MA, Yousif Fadhil, Razykov TM, Amin N, Sopian K. Research and development aspects on decentralized electrification options for rural households. Renew Sustain Energy Rev 2013;24:314–24. http://dx.doi.org/10.1016/ j.rser.2013.03.057. [59] Fedrizzi Maria Cristina, Ribeiro Ferrnando Selles, Zilles Roberto. Lessons from field experiences with photovoltaic pumping systems in traditional communities. Energy Sustain Dev 2009;13:64–70. http://dx.doi.org/10.1016/j.esd.2009.02.002.

1042

Renewable and Sustainable Energy Reviews 78 (2017) 1033–1043

L.R. Valer et al.

10.1016/j.rser.2015.06.043. [63] Taele BM, Mokhutsoane L, Hapazari I, Tlaili SB, Senatla M. Grid electrification challenges, photovoltaic electrification and energy sustainability in Lesotho. Renew Sustain Energy Rev 2012;16:973–80. http://dx.doi.org/10.1016/ j.rser.2011.09.019. [64] Wamukonya Njeri. Solar home system electrification as a viable technology option for Africa's development. Energy Policy 2007;35:6–14. http://dx.doi.org/10.1016/ j.enpol.2005.08.019. [65] Christophe de Gouvello, Yves Maigne. Descentralized rural electrification. An opportunity for mankind, techniques for the Planet. Systèmes Solaires; 2002.ISBN: 2913620140.

[60] Rudi Henri Van Els, João Nildo de Souza Vianna, Antonio Cesar Pinho. The Brazilian experience in the rural electrification in the Amazon with decentralized generation – the need to change de paradigm from electrification to development Renew Sustain Energy Rev, 16; 2012. p. 1450-1461 doi: 10.1016/j.rser.2011.11. 031. [61] da Silva Pereira Edinaldo José, Pinho João Tavares, Galhardo Marcos André Barros, Macedo Wilson Negrão. Methodology of risk analysis by Monte Carlo Method applied to power generation with renewable energy. Renew Energy 2014;69:347–55. http://dx.doi.org/10.1016/j.renene.2014.03.054. [62] Chauhan Anurag, Saini RP. Renewable energy based off-grid rural electrification in Uttarankhand state of India: technology options, modelling methods, barriers and recommendations. Renew Sustain Energy Rev 2015;51:662–81. http://dx.doi.org/

1043