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 Luis Carlos Macedo Blasques, Edinaldo José da Silva Pereira, João Tavares Pinho
 GEDAE/UFPA – Grupo de Estudos e Desenvolvimento de Alternativas Energéticas
                             Universidade Federal do Pará
         P.O. Box 8605, Zip Code 66.075-970, Phone/Fax: 55 91 3201-7299
          e-mails: lblasqs@ufpa.br, ejspereira@oi.com.br, jtpinho@ufpa.br

Abstract: The main objective of this paper is to present positive and negative points
of the two phases of the implantation of the Tamaruteua PV-wind-diesel hybrid power
system, comparing them to other experiences gained from other systems previously
installed by GEDAE. The main experiences acquired at Tamaruteua, positive and
negative, both of technical and management types, were the preference for a
modular inverter system, the need for better adjustments of the automatic control
system, and the need for the establishment of new management models, integrated
to the pre-paid metering system, aiming at maximizing its benefits. This is important
to guarantee the system’s sustainability and to minimize the use of the diesel
generator-set, reducing the operational costs and the environmental impacts. This
work also presents as contribution the suggestion of some points that can be
determinant to the implantation of more reliable and efficient hybrid power systems,
regarding the present reality of the Amazon Region and Brazil.

The first hybrid power system of Tamaruteua was installed in 1999 and kept in full
operation until 2002. Problems associated with the maintenance and replacement of
imported equipment and parts, especially the power inverters, lack of economic
resources and the absence of an efficient management system resulted in the
impossibility of the system’s prompt complete recovery. At the end of 2006, with
support of the Brazilian Federal Government, the system was revitalized.
The main changes at the new system’s configuration (Fig. 1) were the duplication of
the PV system’s capacity, the substitution of the three imported power inverters,
directly responsible for the first interruption of the system functionality, by a national
equipment, more robust and with full availability of specialized technical assistance in
Brazil, the substitution of the first battery bank for a new one, with 64 185 Ah/12 V
batteries, the installation of a new 40 kVA diesel generator-set, with a control system
that automatically operates the diesel generator during low battery conditions,
stopping it and operating the inverter when the battery bank voltage returns to a
satisfactory level, and the installation of a pre-paid metering system.

        Figure 1 - Tamaruteua system’s configuration after the revitalization.

GEDAE had several difficulties during the installation and operation of Tamaruteua’s
system, such as the geographic isolation, the difficulty of access, the costs of
installation and replacement of some equipments, the culture of the local inhabitants,
the high costs associated with the operation of the diesel generator-set, the system’s
configuration, the replacement of lamps and other domestic equipment by the users,
the metering system, the great distance from the manufacturers and suppliers, the
choice between national and imported equipment, the system management, the
online supervision, etc. Those difficulties are quite common for almost all isolated
power systems in the Amazon Region, and some of them have to be overcome for all
installed systems. Problems like the choice between national and imported
equipment, mainly for the metering and storage systems, and the best configuration
of the system, mainly related to the inverter system, were particularly serious at
Tamaruteua, and is discussed with more details in the following sections.
With more than 10 years of experience with power generation systems with
renewable sources, GEDAE had installed 5 decentralized generation systems, with
inverter systems from 4 to 18 kW. Imported power inverters were installed at four of
the five systems: Tamaruteua (first phase), Praia Grande, Mota and Caxiuanã (first
and second phases), mainly due to the unavailability of national equipment at the
time of the installations. A total of seven power inverters were installed at the four
systems, with individual sizes varying from 4 to 5.5 kW. Two 4 kW single-phase
inverters were installed at Praia Grande; at Tamaruteua three 5.5 kW single-phase
inverters were installed and synchronized to form a three-phase system. Five of the
seven inverters presented some kind of fault, which made three of the four systems
inoperative (only the inverter of Mota did not present any fault). Problems associated
with the lack of local technical assistance for those equipment, high repairing costs,
and the long time needed to send them for repair were the main motivational factors
for the change to national equipment.
After approximately four years of inactivity, a national power inverter was chosen
when the Tamaruteua system was revitalized. The experience with national
equipment was introduced at the fourth hybrid system installed by GEDAE, at the
community of São Tomé. Later on, with the possibility of revitalization and expansion
of the Caxiaunã PV system, a national inverter was also used. The two main
advantages of the national inverters are the easier maintenance, considering time
and costs, and the lower acquisition costs. It is expected that the initial costs will be
lower with the increase of the demand, but until now the demand is still low.
The main disadvantage is that the national technology of powers inverters for
electricity generation systems is still immature. Its basis is the industry of no-breaks
for backup systems, already consolidated in Brazil, but also needing some specific
adaptations to perfectly act as inverters for generation systems. This disadvantage is
directly connected to the difficulty to find suppliers that guarantee the product quality,
which lead GEDAE to establish an informal partnership with one company. The first
national power inverter manufactured by this company and installed at São Tomé
presented several problems, mainly associated with the action of saltpeter in the
electronic components of the equipment, that required some improvements
developed by the manufacturer. The inverter of Caxiuanã also presented some
problems, but the substitution of a few components made the equipment more
reliable, standing on full operation for the past 18 months. Finally, the inverter of
Tamaruteua, the last to be developed, is the most complex, but presented good
results during the first year of operation. A problem, possibly associated to an over-
current on the distribution grid made the inverter inoperative since December 2007.
Due to the lack of financial resources, the problem is still unsolved.

GEDAE installed its second pre-paid metering system in isolated power systems at
Tamaruteua. The first one, installed at São Tomé, was manufactured by the
association of two national companies, and presented several problems in almost all
of the 65 meter-manager sets. The end of the association prevented an appropriated
maintenance/improvement of them and the sets are now useless. Presently, there is
no national company with proved experience in the development of this kind of
equipment. GEDAE chose imported meters for its second experience with pre-paid
metering systems, at Tamaruteua. One hundred meters imported from India were
acquired, presenting a failure percentage of 20% since 2007, when the meters were
installed. Besides this, the pre-paid metering system of Tamaruteua presents two
main advantages in comparison to the national system: the presence of only one
equipment that combines the functions of meter and manager, which makes the set
more reliable and reduces failure probabilities, especially with communication; and
low costs (approximately 50% lower than the national sets). The main disadvantage
is the lack of local maintenance. This problem can be solved with the implantation of
an industrial branch of the Indian company in Brazil, that is already expected.

The Brazilian market still does not present great advantages for the use of solar
batteries, mainly based on the cost/benefit relation between the conventional
batteries and the solar batteries used for power systems applications. The still high
costs of the PV batteries are mainly associated with the unavailability of national
manufacturers. The majority of the projects developed by GEDAE have cost
restrictions that can compromise the system acquisition and its performance. The
initial costs of the solar batteries make its use prohibitive, but its larger useful life can
postpone the need of financial support over the system’s lifetime, reducing the
operation and maintenance costs. However, this is usually not accepted by the

GEDAE experiences lead to the conclusion that there some progress has been
achieved with small hybrid systems installed in the Amazon Region. For more than a
decade GEDAE has been installing and monitoring hybrid systems of different
configurations, and testing several actions in order to solve or minimize the problems.
All the applied solutions, always focusing the local inhabitants’ welfare, were
compromised most of the time by the lack of financial support along the useful life of
the systems. Anyway, it is possible to show some feasible and important actions,
common for most of the hybrid systems in the Amazon Region, that can help make
them more reliable. These are:
- The use of a pre-paid metering system, that can avoid many problems with the local
inhabitants because they pay only for what is really being consumed;
- The use of a modular and reliable national inverter system. This action depends on
an urgent development of the national industry. Inverters coming from other
countries, despite their high quality, are always expensive to acquire, repair or
- The national industry must offer solar batteries which can guarantee a low
acquisition cost and a large lifetime;
- The acquisition costs of the system, particularly inverters, PV modules, wind
generators and batteries have to go down. The use of renewable energy cannot grow
in Brazil while such costs are not reduced.
All these actions, however, depend on the regulation of the installation and operation
of renewable energy systems with micro-grids in Brazil, which is presently being
done by the government, but still very humbly.
Table 1 shows a brief analysis of the 5 decentralized renewable generation systems
installed by GEDAE, focusing the problems related to the inverters, metering and
storage systems, and presenting some possible solutions for future development.
     Table 1 - Problems and solutions of renewable systems installed by GEDAE.
                 Inverter    Metering       Storage                                Suggested
   System                                                  Main Problems
                 System      System         System                                  Solutions
                 3 single-                               Faults on two of the
 Tamaruteua        phase                                   inverters, with
                             Fixed fees      solar
  (1st phase)    imported                                    difficulty of
                 inverters                                  maintenance
                 1 single-
                   phase                                      None. No
    Mota                       None       conventional
                 imported                                 residential supply
                 2 single-                                   Faults on the       - Adoption of a
    Praia          phase                                    inverters, with     modular national
                             Fixed fees   conventional
   Grande        imported                                     difficulty of     inverter system;
                 inverters                                   maintenance          - Pre-paid
                 1 single-                                   Faults on the      metering system
  Caxiuanã                                  National
                   phase                                    inverters, with     with integrated
 (1st and 2nd                  None       conventional
                 imported                                     difficulty of      manager and
   phases)                                  batteries
                  inverter                                   maintenance            meter;
                 1 three-                                                       - Use of national
                                            National     Small faults on the
  Caxiuanã        phase                                                           conventional
                               None       conventional    inverter, but with
 (3rd phase)     national                                                       batteries, but the
                                            batteries    easy maintenance
                 inverter                                                       development of a
                 1 three-    National                                             national solar
                                            National       Faults on the        batteries industry
                  phase      pre-paid
 São Tomé                                 conventional     majority of the         is expected.
                 national    metering
                                            batteries      metering sets
                 inverter    system
                                                          Small faults on the
                                                         inverter and meters,
                 1 three-    Imported
 Tamaruteua                                 National           with easy
                  phase      pre-paid
  (revitaliza-                            conventional   maintenance for the
                 national    metering
     tion)                                  batteries        inverter and
                 inverter     system
                                                          complicated for the

[1] Pinho, J. T., Barbosa, C. F. O., Pereira, E. J. S., Souza, H. M. S., Blasques, L. C.
M., Galhardo, M. A. B., Macêdo, W. N., “Sistemas Híbridos: Soluções Energéticas
para a Amazônia”, 1st edition, Brasília, Ministério de Minas e Energia, 2008.
[2] Pereira, E. J. S., Pinho, J. T., Vale, S. B., “Revitalização do Sistema Híbrido
Eólico-Fotovoltaico-Diesel de Tamaruteua, Município de Marapanim, Pará”, I CBENS
– I Congresso Brasileiro de Energia Solar, Fortaleza, Brasil, 2007.
[3] Blasques, L. C. M., Vale S. B., Pinho, J. T., “Sistema Solar Fotovoltaico para
Geração de Eletricidade na Estação Científica Ferreira Penna do Museu Paraense
Emílio Goeldi, Caxiuanã – Pará”. I CBENS, Fortaleza, Brasil, 2007.