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Energy payback time is the time it takes for a module to produce the amount of energy that was spent while producing the module. Currently the energy payback time of REC modules is about 1 year. The modules are given a 25 year guarantee, so the last 23 years (or more…) will give a net energy gain.
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All solar modules produce electric current in essentially the same way. The main differences seen by the customer are in price, appearance, life time and efficiency. In general, thin film cells are cheaper, but less effective than crystalline cells, and have a shorter life time. Which type is most cost effective is then a question of the interest level, electricity price, whether you use a tracking system or not, and whether you have a limited area available for the modules.
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The cost of electricity generated by a PV system is in principle a function of the investment cost and the financing cost divided by the total electricity production over the lifetime of the system. The investment cost is largely dependent on the cost of the PV module which is largely dependent on the cost of solar grade silicon. The cost of PV modules is constantly falling due to high degree of competition and technology improvements throughout the value chain. In most markets the cost of electricity is increasing. When solar cells can produce electricity at the same price as the electrical energy you can buy off the grid (or cheaper), without including subsidies or feed-in tariffs, the market is at “grid parity”. From then on, it is expected that it will be cheaper to buy a solar system than to buy electricity from the grid. Grid parity will be reached first in areas with lots of sun and high electricity prices, like Italy and California.
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In remote areas with low density of possible customers and long distance to existing grid or power plant, off-grid solutions is often the only practical and economical solution for electricity supply. This can either be systems for a single house, or may be micro-grids supplying a village from one or several connected PV-systems. These systems need storage capacity such as batteries and/or some other power generating technology.
The advantages of on-grid are that there's no need for a battery, that you can sell surplus current and get current from the grid during nighttime.
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The major share of the PV power is fed into the low voltage grid, only a minor share is fed into the medium voltage grids. This decentralized structure combined with the fact that PV power is mainly generated during peak-load periods of the grid, makes PV power economically attractive. German studies shows that PV and wind power can cover peak-load demand and 30 GW distributed capasity may be introduced without grid-problems. 50 GW is also acceptable and then also base-load is replaced by PV and wind. No additional grid-capacity is needed. Cumulative installed PV-capacity in Germany by 2008 was 5,3GW.
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Yes, it can. The annual production is dependent on a range of parameters such as the size of the PV-array, orientation and sloping of the roof, irradiation (latitude, local weather conditions), efficiency (module type, temperature). In ideal conditions, with high quality solar modules installed, a rooftop installation can cover the typical electricity for a residential house.
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When a cell is shaded, it produces less current. Because the cells are connected in series, the total energy production of the module is reduced to a level determined by the most shaded cell. Solar modules should therefore never be mounted in a way that leaves them partially shaded much of the day (chimneys, antennae etc…).
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Both FBR and the old Siemens process perform the same job; turning silane gas (SiH4) into solar grade silicon (99.99999% pure Si). In the Siemens process, the Silane gas is sent into big reactors, with hot rods where the silane splits into silicon, which sticks to the rod, and hydrogen gas. In order to avoid silicon being deposited on the walls of the reactor, these have to be cooled continuously. This cooling means a lot of energy is leaving the reactor without doing any useful work. When the rods reach a certain size, the reactor has to be stopped, cooled down, and emptied. Again, a lot of energy (and time) is used to make the reactor ready for a new batch.
In the FBR, the silane gas flows up through a "Fluidized Bed" of silicon particles, where the temperature is so high that the silane gas splits up, and the silicon sticks to the particles. The total surface of all the particles is more than 1000 times the surface of the rods in the Siemens reactor, so the deposition is much faster. When the particles grow sufficiently big, they fall out of the reactor. In this way the reactor never needs to stop, it works faster, and it does not need cooling - all reducing the energy consumption.
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Several production units are being built in Singapore; there will be a wafer plant, a cell plant and a module plant. Inside these plants again there are a number of process steps. On the wafer side, the recently introduced technology in the two latest wafer plants going online in Norway in 2009 is being implemented also in Singapore, with only modest adjustments. In the cell and module plants there are a few major changes from existing lines in Norway and Sweden, while most of the processes mainly have been improved through continuous improvement work.
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We have only been producing modules since 2003. Because no type of accelerated testing can accurately duplicate 30-40 years of actual use, there is no way we can predict this exactly. REC uses standard components also used by our competitors, so the differences should not be significant. What we can say is that crystalline solar cells in general show very long life times compared to thin film cells. Solar modules that were produced more than 30 years ago are in general still producing current at close to their original efficiency.