Energies Nouvelles et Environnment

Brief DescriptioBrief Description of the company and E.N.E. APPOLLON activities

E.N.E. (Energies Nouvelles et Environnement s.a./n.v.) was incorporated in 1976 and is one of the oldest photovoltaic companies in Europe. The Belgian company groups businessmen, engineers and scientists who are involved in photovoltaics since as early as 1975.
The head office is located in Brussels, Belgium. There are two production facilities located in Zaventem (Belgium) and in Brussels close to the head office. In Zaventem crystalline Si solar cells and modules for terrestrial applications as well as GaAs/Ge cells for space applications are produced, whereas in Brussels the polishing of Germanium wafers is performed.
E.N.E. began manufacturing its own Silicon panels in 1978, and its first solar cells in 1980. As of 1984, E.N.E. has pioneered the use of wire saws to produce homemade silicon wafers, thus completing the vertical integration of its facilities.
The company has a 20 year experienced system design team specialised in rural electrification of remote areas. For example, E.N.E. (supported by health care organisations) has equipped hospitals and farms in Africa as well as islands in the Indian Ocean with complete turnkey solar systems for providing power in places, where no power grid is available. Furthermore, E.N.E. is providing silicon cell technology and production equipment to enable third-world people to produce their own photovoltaic modules. We are proud to say: E.N.E. photovoltaic technology is saving lives since many years!
Since 1995, E.N.E. is producing space solar (see picture 1) cells by epitaxial growth of gallium arsenide on Germanium substrates in its MOCVD reactor, which is one of the largest in Europe. For these cells, E.N.E. manufactures also its own germanium substrates by utilizing its wire saw and polishing facilities, which is a unique case of vertical integration in the field of space cells.
Since 2003, E.N.E. produces triple junction solar cells with monolithically stacked GaInP on GaAs on Ge junctions.
In the APOLLON project, which concerns the development and optimisation of Point-Focus (PF) and Mirror-Based-Spectra-Splitting (MBS) photovoltaic concentration systems, E.N.E. will produce and further develop different types of concentrator cells and will provide Germanium wafers to other projects partners.

The major goals of optimisation process are:

• low cost/Watt
• high efficiency and yield at high concentrations
• high reliability

All optimisation processes need to find a balance of these goals.

In particular, E.N.E. has to produce, based on the present state of the art, 1st generation dual junction cells (designated illumination area 2 mm2) for PF-system (see picture 2) and InGaP cells (designated illumination area 58 mm2) for MBS system application. Subsequently, those types of cells shall be improved for reaching the goals as described above for a 2nd generation of concentrator cells.
Another important task is the development of triple junction cells for concentrator systems. A key element of this development is to obtain well and stable working tunnel junctions at high concentration on the whole or at least a high ratio of the wafer area. In more detail, the optimised doping of the epitaxial layers to handle ultra high current densities is difficult to achieve.
Besides the development of multi junction solar cell structures, also a proper metal grid design to minimise series resistance losses adapted to the special properties of each type of cell is a further task of the E.N.E. activities.
The different cell types as roughly described above are based on Germanium substrates, which are much more expensive as compared to Silicon substrates. So another option, especially regarding looking for lower substrate costs, is the utilisation of Silicon substrates for concentrator cells. For this reason E.N.E. shall also produce dual junction Si/Ge cells (100 mm2) for MBS system application. The results shall help to decide, whether it is worthwhile to take advantage of lower costs, however at lower cell efficiencies on the other hand.
Finally, E.N.E. has successfully developed a technology for Germanium wafer production in the past years. The technology contains the efficient wire saw cutting of Germanium crystals, as well as the polishing and the final treatment of Germanium wafers. The resulting wafers do have epi-ready surface quality as needed for MOCVD application. Within the APOLLON project, E.N.E. shall provide standard Germanium substrates (diameter 100 mm, thickness 150 μm) for the wafer demand of other project partners and its own use. In addition to that, E.N.E. shall develop and produce very thin Germanium substrates with a thickness down to 120μm.

 

Figure 1: GaAs/Ge space solar cell (about 16 cm2) produced by E.N.E.

Figure 2: Multi junction concentrator cells (each about 2 mm2) produced by E.N.E.

 

ENERGIES NOUVELLES ET ENVIRONNEMENT
SOCIETE ANONYME - NAAMLOZE VENNOOTSCHAP
AVENUE VAN DER MEERSCHEN 188 - B-1150 BRUSSELS (BELGIUM)
Tel. + Fax : +32 2 771 13 28