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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 sold with a 25 year guarantee, so for 24 years the module will give a net energy gain.
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All solar modules produce electric current in essentially the same way. The main difference from a customer point of view is the approximately 30% higher electricity production per area achieved with crystalline silicon modules. With reasonable module prices and lower installation costs, crystalline silicon modules generally represent the most economically attractive installation. For some commercial large area solar parks where the area used is of no concern, thin film modules can be an economically competitive alternative.
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"Grid parity" is the point in time when a solar systems can produce electricity at the same price as the electricity you can buy off the grid (or cheaper) without subsidies or feed-in tariffs. Grid parity will be reached first in areas with lots of sun and high electricity prices. In a very few niche markets, like Hawaii and parts of California, grid parity has been reached already. We are expecting to reach grid parity in many important markets over the next three to five years.
Until grid parity has been reached, the solar industry will rely on policy support and incentive schemes. The price of PV has been halved over the past five years as the industry gradually is reducing the production costs by focusing on technology improvements across the value chain.
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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.
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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 capacity 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 the end of 2010 was about 17GW.
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Yes, it can. In well-suited conditions, with high quality solar modules installed, a rooftop installation can cover the typical electricity for a residential house. 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).
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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 that 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, 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 operates continuously, it works faster, and it does not need cooling - all reducing the energy consumption.
- What is the technical lifetime of our modules vs other modules (after the warranty)?
We have 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 employs high quality materials and strict quality controls, and we expect that the technical lifetime is competitive. Solar modules that were produced more than 30 years ago are in general still producing current at close to their original efficiency.