PILOT PLANT TO DEVELOP COST EFFECTIVE PHOTOVOLTAIC MODULES
A. Moehlecke and I. Zanesco
Brazilian Centre for Development of Photovoltaic Solar Energy – CB-Solar
Faculty of Physics – Pontifical Catholic University of Rio Grande do Sul – PUCRS
Av. Ipiranga, 6681, Prédio 96A – Porto Alegre – RS – Brazil – CEP 90619-900
FAX: 55-51-3320 3616 – e-mail: [email protected], [email protected]
ABSTRACT: This paper presents a PV module pilot plant established at NT-Solar/CB-Solar in order to promote
rapid technology transferring from lab scale to production lines. The pilot plant is supported by Brazilian Ministry of
Science and Technology, through the Brazil Technology Network and the financing agency FINEP as well as three
energy companies (CEEE-GT, Eletrosul and Petrobras). Main innovations of the pilot plant are: a) technology - a
sequence process that uses low cost chemicals and gases and relies on gettering to enhance bulk lifetime; b) ambient
- the first time a complete production line, from the wafer to the module, was established in a university campus,
allowing preparation of qualified human resources for PV industries; c) management - project is managed by a
committee composed by representatives of all companies, agencies and university involved. A history of the project,
the lab infrastructure and first results are outlined in this work.
Keywords: Pilot Plant, c-Si, Manufacturing and Processing.
1
INTRODUCTION
High amounts of solar radiation reach Brazil every
month and rich and pure quartz deposits are found in its
territory. Moreover, Brazil is a leading producer of
metallurgical grade silicon. Also, the electric energy
demand is growing and ten million people do not have
access to electricity. In this context, PV systems may
play an important role.
A barrier to large application of PV systems is the
higher price of electric power when they are compared to
that produced by hydroelectric power plants. A local PV
industry may enable to reduce the price of photovoltaic
systems and consequently the use of photovoltaic solar
energy could contribute to supply the increasing electric
energy demand.
Since 1970 several solar technologies were studied at
the university or research centres [1] and in the 80’s a PV
module fabrication plant started-up.
The Brazilian government implemented a first
programme to promote rural electrification with PV
systems, the PRODEEM, (Programme for Energetic
Development of States and Municipalities), involving
several universities and state secretariates. In order to
continue the PRODEEM, the programme, Light for All
(Luz para Todos), was started in 2004. As a result of the
latter programme, some utilities are implementing rural
electrification with photovoltaic systems [2].
In 2002, the INMETRO, the Brazilian Institute for
Metrology, Standardization and Industrial Quality
(Instituto Brasileiro de Metrologia, Normalização e
Qualidade Industrial) created a working group for PV
systems, named GT-FOT as part of the Brazilian
Programme for Labelling - PBE (Programa Brasileiro de
Etiquetagem) [3]. The task force, composed by
specialists from universities, Brazilian suppliers,
manufacturers and public organizations, established the
standards for labelling PV systems and their components.
The program for PV systems was implemented due to an
agreement between INMETRO and ABEER – Brazilian
Association of the Renewable Energy Companies
(Associação Brasileira das Empresas de Energia
Renovável).
The regulations of ANEEL (Brazilian Agency for
Electric Energy - Resolução Normativa no. 83 20/09/2004), specify the conditions requested for using
Individual Stand-Alone Systems Based in Intermittent
Sources - SIGFI (Sistemas Individuais de Geração de
Energia Elétrica com Fontes Intermitentes) to supply
electric energy to Brazilian consumers in rural areas.
These regulations require that all of these systems,
including the PV systems, shall conform to the
specifications of PBE/INMETRO.
As a strategy, to promote the development of
photovoltaic applications, in 2004, the Brazilian Centre
for Development of Photovoltaic Solar Energy (CBSolar) was established at the Solar Energy Technological
Nucleus (NT-Solar) of Pontifical Catholic University of
Rio Grande do Sul (PUCRS). The partners are PUCRS,
Ministry of Science and Technology (MCT), Secretariat
of Energy, Mines and Communication and Secretariat of
Science and Technology, both of state of Rio Grande do
Sul, the Municipality of Porto Alegre and the State
Electrical Utility (CEEE) [4].
One of the first activities of the centre was to
organize, jointly with two other university research
centres (IEE-USP, Instituto de Eletrotécnica e Energia,
Universidade de São Paulo and GEDAE-UFPA, Grupo
de Estudos e Desenvolvimento de Alternativas
Energéticas, Universidade Federal do Pará) MCT and
Federal Ministry for Mines and Energy, the First
Brazilian PV Solar Energy Symposium in order to
discuss the past, present and future of this technology in
Brazil. Specialists from universities, research centres,
utilities, federal and state agencies, metallurgic grade
silicon suppliers and industries that produce BOS
components for PV systems and specialists of PV
industries as well as non-governmental organizations
participated of the symposium.
Other important activity of CB-Solar was to sign a
contract of R&D between the university, three energy
companies and a government financial agency. The goal
of the project “Pilot Plant to Produce Cost Effective
Photovoltaic Modules” is to research cost effective
technologies of industrial processes of silicon solar cells
and modules. The purpose of this paper is to present a
detailed description of this pilot plant.
In Europe, since the 80’s the development of
industrial processes of solar cells has been carried out at
IMEC (Interuniversity MicroElectronics Centre) [5].
From the research&development activities of this centre,
several success PV companies were spin-off. In 2005, the
ISE (Fraunhofer Institute for Solar Energy Systems)
published the implementation of a research unit for
applied R&D for silicon solar silicon solar cell
production, the Photovoltaic Technology Evaluation
Center (PV-TEC) [6]. The centre was created to support
the German and European photovoltaic industry with
large scale research.
2
HISTORICAL
The process to fabricate cost effective crystalline
silicon solar cells, based on phosphorus/aluminium as
dopants and low cost chemicals and gases was patented
by the University. The activities related to the
development of cost effective silicon solar cell with
efficiency of 17% was recognized and the team leader
received a national award: the Young Scientist Prize,
2002. One year after, the paper was submitted to the
XVII National Seminar on Electrical Energy Production
and Transmission was recognized with the “Best Paper
Award”.
In 2002 the design and building of a facility to
fabricate silicon solar cells and modules was started as an
initiative of the University. In this facility, the lab-scale
technology should be transferred to industry scale.
Although lab-research has been advanced in the last
years, there was not a government strategy to promote
research on cost effective technologies and industrial
development. Bearing these in mind, the Brazilian Centre
for Development of Photovoltaic Solar Energy, Brazil
Technology Network, a programme of the Ministry of
Science and Technology, the financing agency FINEP
(Financiadora de Estudos e Projetos), the PUCRS and
three Brazilian companies of the energy sector (CEEE –
GT, Companhia Estadual de Geração e Transmissão de
Energia Elétrica, ELETROSUL - Eletrosul Centrais
Elétricas S. A. and PETROBRAS - Petróleo Brasileiro S.
A.) planned and are implementing a pilot plant to
develop cost effective silicon solar cells and photovoltaic
modules.
The contract with the partners was signed in 2004,
after two years of discussions and planning. In 20052006, the installation and start up of the equipments was
ended and in August 2006 the optimization of the silicon
cells processes was started. One year later, the efficiency
of 14.8 % was achieved with simple structures and
screen-printing metallization.
3
and PUCRS. FINEP and Ministry of Science and
Technology assigned observers. Main decisions,
technical and economic, are discussed and determined
with the participation of the partners.
4
INFRASTRUTURE
NT-Solar/CB-Solar team has been researching silicon
solar cell processes, static concentrator PV modules and
sizing stand-alone systems.
The pilot plant has been implemented by using the
infrastructure of the Solar Energy Technological Nucleus
of PUCRS. This is the most modern and well-equipped
facility for photovoltaic research in Latin America,
having a total area of 950 m2 of which 212 m2 are clean
room labs (10.000 class, ISO7).
Labs are equipped with industrial and automated
equipments, to reproduce on a large scale the lab devices
as well as to develop R&D activities on high efficiency
Si solar cells.
The building is supplied with cooling air and water
and vacuum system. Waste treatment units are been
implemented. Electric energy main supply is located in a
separate building, integrated to main building by an
indoor garden.
Clean room areas are split into seven labs as Figure
1 illustrates. It was designed to produce Si solar cells
(mono and multicrystalline) and modules with different
metallization techniques (screen-printing, electroless, ebeam metal evaporation) and different ways to diffuse
impurities (conventional and rapid thermal furnaces).
The remaining area comprises nine other labs: optical,
simulation, characterization, indoor and outdoor
measurements, labelling, module assembly and
certification. These labs are used to label modules,
batteries, charge controllers and inverters, to characterize
silicon solar cells, to design, built and characterize
concentration PV modules, to carry out outdoor
measurements, to simulate solar cells, concentration PV
modules and PV systems, to analyze experimentally PV
systems, etc. Figure 2 presents details of some
laboratories.
INNOVATIVE ASPECTS
The project is innovative in three aspects: 1)
technology: the process of producing cost effective
silicon solar cells based on low cost chemicals and gases
and on gettering mechanisms [7]; 2) university-industry
relationship: the capacity of developing industrial
processes and devices in the university environment and
3) management: the project (agreement) is managed by a
committee composed by representatives of the companies
Figure 1: Plant pilot basement floorplan.
The clean room is supplied with high quality gases
distributed through labs by electropolished stainless steel
tubes. High purity water is obtained by reverse osmosis
and ion exchange equipments. The clean room was
designed to produce 4” round Si solar cells or pseudo-
square 100 mm x 100 mm wafers, but up to 6” round
wafers can be processed.
PV modules developed can be assembled and
submitted to standard test procedures as well as
monitored in outdoor conditions or integrated into PV
systems.
(paste deposition and firing) and laser edge isolation.
Measurements of minority carrier lifetime, sheet
resistance, reflectance and transmittance, contact and
metal finger resistance and I-V characteristics have been
carried out as well surface analysis by scanning
electronic microscopy.
Solar cells are soldered by an automated tabberstringer system and lamination is implemented. Then, the
module is assembled and submitted to the standard
procedures of certification.
6
RESULTS
Results of the pilot plant are: 1) development of an
industrial process to fabricate cost effective photovoltaic
modules and know-how to built up a facility to produce
silicon solar cells in scale in order to establish
photovoltaic industries; 2) qualified human resources in
undergraduate and graduate levels; 3) fabrication and
labelling of 200 photovoltaic modules; 4) implementation
of a national centre to aid Si solar cell manufacturers and
5) set up a supply chain to PV industry taking into
account Brazilian features, including local silicon
producers.
Two standard cell-processing sequences have been
developed to manufacture n+pn+ and n+pp+ cells starting
from CZ-silicon and by using screen printing
metallization. First results of n+pn+ Si cells structure are
presented in Table 1. The efficiency of 14.8% was
achieved with 4 cm2 cells. Nevertheless, the short-circuit
current density of the 62 cm2 Si cell, shown in Figure 3,
is lower, mainly due to the textured surface. We expect
to increase the efficiency in next semester.
The performance of both structures will be compared
under economic and efficiency point of view.
Table 1: Short-circuit current density (Jsc), open-circuit
voltage (Voc), fill factor (FF) and efficiency (η) of Si
solar cells processed in the pilot plant.
Area
(cm²)
Voc
(mV)
Jsc
(mA/cm²)
FF
η(%)
4
575
34.9
0.74
14.8
62
574
29.5
0.76
12.9
Figure 2: Details of the laboratories of NT-Solar/CBSolar of PUCRS.
5
BASELINE CELL PROCESS
The baseline process to produce Si solar cells has
been developed in order to analyse and optimize new
devices or processes as well as training undergraduate
and graduate student to the industry.
To achieve the complete baseline process,
simulations of Si solar cells and experimental activities
have been carried out: texture etching, wafer cleaning,
diffusion, oxide growth, AR coating, screen printing
Figure 3: Silicon solar cell fabricated in the pilot plant
implemented at NT-Solar/CB-Solar.
It is worth to comment that last year, the pilot plant
to produce Si solar cells and PV modules was awarded
with the Brazilian Innovation and Sustainability Prize.
7
CONCLUSIONS
In summary, it was the first time that a pilot plant to
develop industrial PV technology was implemented in
the university environment, combining education,
research and industrial development.
8
ACKNOWLEDGEMENTS
Authors would like to thank the staff of NTSolar/CB-Solar engaged to install and support
equipments and to process silicon solar cells.
The financial support by the Brazilian financing
agency FINEP (Financiadora de Estudos e Projetos),
CEEE-GT (Companhia Estadual de Geração e
Transmissão de Energia Elétrica), ELETROSUL
(Eletrosul Centrais Elétricas S. A.) and PETROBRAS
(Petróleo Brasileiro S. A.) is gratefully acknowledged.
REFERENCES
[1] N. G. Dhere, L. R. Cruz, P. C. Lobo, J. R. T. Branco,
R. Rüther, I. Zanesco, Proceedings ISES 2005 Solar
World Congress, (2005).
[2] A.S.A.C. Diniz, M.S.C.C. Mendonça, F.Q. Almeida,
D. Costa and C. A. Alvarenga, Progress in
Photovoltaics: Research and Applications 6 (1998)
365.
[3] M. A. Galdino, J. H. Lima, A. Novgorodcev, R.
Zilles, I. Zanesco, A. Moehlecke, A. F. Orlando, A.
Krenzinger, 20th European Photovoltaic Solar Energy
Conference, (2005) 3199.
[4] A. Moehlecke, I. Zanesco, 20th European
Photovoltaic Solar Energy Conference, (2005) 3111.
[5] F. Duerinckx, L. Frisson, P. P. Michiels, P. Choulat,
J. Szlufcik, Proceedings 17th European Photovoltaic
Solar Energy Conference, (2001) 1375.
[6] D. Biro, R. Preu, S. W. Glunz, S. Rein, J. Rentsch, G.
Emanuel, I. Brucker, T. Faasch, T. Faller, G.
Willeke, J. Luther, Proceedings 21st European
Photovoltaic Solar Energy Conference, (2006) 621.
[7] A.Moehlecke, I. Zanesco, J. P Souza, H. Boudinov
and C. del Cañizo, Proceedings 17th European
Photovoltaic Solar Energy Conference, (2001) 1873.