Rooftop photovoltaic power station
A Rooftop photovoltaic power station is a system which uses one or more photovoltaic panels, installed on rooftops of residential or commercial buildings, to convert sunlight into electricity. The various components in a rooftop photovoltaic power station include photovoltaic modules, mounting systems, cables, Solar inverters and other electrical accessories.
The urban environment provides a large amount of empty rooftop spaces and can inherently avoid the potential land use and environmental concerns. Estimating rooftop solar insolation is a multi-faceted process, as insolation values in rooftops are impacted by the following:
- Time of the year
- Weather conditions
- Shading from adjacent buildings
- Shading from overhanging vegetation
- Roof slope
- Roof aspect
- Shading from adjacent buildings and trees
There are various methods for calculating potential solar PV roof systems including the use of LiDAR and orthophotos. Sophisticated models can even determine shading losses over large areas for PV deployment at the municipal level.
Visual-SOLAR is a Geographic information system (GIS) tool being developed that uses high-resolution Light detection and ranging (LiDAR)-derived Digital Surface Models to accurately recreate the earth’s surface, including building rooftops. LiDAR is an optical remote sensing technology that can measure the distance to, or other properties of a target by illuminating the target with light, often using pulses from a laser. Downward-looking LiDAR instruments fitted to aircraft and satellites are used for surveying and mapping. Digital surface models (DSM) depict the elevation of the top surfaces of buildings, trees, towers, and other features located above the bare earth. The tool processes upward-looking hemispherical view shed algorithms to calculate insolation for each location on the digital elevation models. The calculation evaluates the above the canopy against other algorithms for insolation under canopy locations. The framework considers only the insolation that falls on building rooftops, not on the ground. The method accounts for adjacent structures/trees, slope, aspect, elevation, latitude, temporal and atmospheric factors. Currently, the tool simply reports the total amount of insolation falling on a given rooftop and could be enhanced to provide an energy estimate.
Feed-in tariff mechanism
In a grid connected rooftop photovoltaic power station, the generated can be sold to the grid at a price higher than what the grid charges for the consumers. This arrangement provides payback for the investment of the installer. Many consumers from across the world are switching to this mechanism owing to the revenue yielded. The FIT as its commonly known has led to an expanision in the solar PV industry worldwide. Thousands of jobs have been created through this form of subsidy. However it can produce a bubble effect which can burst when the FIT is removed. It has also increased the ability for localised production and embedded generation reducing transmission losses through power lines.
A rooftop photovoltaic power station (either on-grid or off-grid) can be used in conjunction with other power sources like diesel generators, wind turbine etc. This system is capable of providing a continuous source of power.
- Installers have the right to feed solar electricity into the public grid and hence receive a reasonable premium tariff per generated kWh reflecting the benefits of solar electricity to compensate for the current extra costs of PV electricity.
- An electrical power system containing a 10% contribution from PV stations would require a 2.5% increase in load frequency control (LFC) capacity over a conventional system. The break-even cost for PV power generation is found to be relatively high for contribution levels of less than 10%. Higher proportions of PV power generation gives lower break-even costs, but economic and LFC considerations imposed an upper limit of about 10% on PV contributions to the overall power systems.
The Jawaharlal Nehru National Solar Mission of the Indian government is planning to install utility scale grid connected Solar Photovoltaic systems including rooftop photovoltaic systems with the combined capacity of up to 20 gigawatts by 2022.
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- List of rooftop photovoltaic installations
- Photovoltaic power plant
- Solar Energy Generating Systems
- Building-integrated photovoltaics
- Solar inverter
- Solar cable
- Maximum power point tracker
- Solar tracker
- Solar shingles
- "Prediction of Energy Effects on Photovoltaic Systems due to Snowfall Events"