The embodied energy refers to all of the energy expended in the manufacture and delivery of a commodity. The embodied energy payback time is the amount of time it takes for generating capacity to generate the same amount of usable energy that was used to create it.
The energy payback time for a solar panel in Australia can be much less than one year, and the term for a complete rooftop solar system can be less than two years.
To guarantee a net energy gain, the embodied energy of renewable energy technologies must be considered. To be successful, a solar cell’s embodied energy must be less than its total energy output.
Many processing stages are required to assemble a solar cell, and the embodied energy should be kept to a minimum. The following sections explain some of the most significant steps of embodied energy in silicon solar cells.
To make metallurgical grade silicon, carbothermic reduction of quartz sand (silicon dioxide) is used. This method uses 20 kWh per kilogram of metallurgical grade silicon produced.
Metallurgical grade silicon must then be refined to electronic grade silicon via a 300 °C hydrochloric acid reaction followed by a 1100 °C hydrogen gas process. This method uses 100 kWh of electronic grade silicon per kilogram.
This silicon is then melted and crystallized at 1400 °C, requiring 290 kWh/kg of silicon single crystal. This type of silicon is appropriate for use in solar cells. After accounting for material losses at each stage, these processes incorporate 460 kWh of energy into each kg of silicon single crystal.
Solar Cell Production
A multiwire saw is used to split a single crystal of silicon into wafers, resulting in a 40% to 50% loss as dust. After that, a series of high temperature diffusion, oxidation, deposition, and annealing processes are carried out.
This increases the stored energy of the solar cell by 120 kWh/m2.
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The module is then constructed from a glass front panel, an encapsulant, a solar cell, copper ribbon, a foil back cover, and an aluminum channel. During assembly, 190 kWh/m2 of embodied energy is introduced.
After that, the module is usually installed in a field or on a rooftop. The module must be sustained in the field by concrete, cement, and steel. Construction and components increase embodied energy by 500 kWh/m2. Rooftops already have a support system, lowering energy to 200 kWh/m2.