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Comparison between Photovoltaic (PV) cells and
Concentrating Solar-Thermal Power (CSP) systems
Photovoltaic (PV) cells directly convert sunlight into electricity using semiconductor materials, while Concentrating Solar-Thermal Power (CSP) systems use mirrors to concentrate sunlight to create heat, which then drives a turbine to generate electricity.
Operating Principle
- PV cells convert sunlight directly into electricity through the photovoltaic effect, generating direct current (DC) that is then inverted to alternating current (AC) for use.
- CSP systems use mirrors or lenses to concentrate sunlight onto a receiver that heats a fluid to produce steam which drives a turbine to generate electricity, producing AC indirectly via thermal energy conversion.
Energy Conversion and Efficiency
- PV panels'' efficiency ranges around 17-20% commercially, with potential for higher efficiencies in advanced designs. They convert light directly and work in diverse weather conditions without needing direct sunlight.
- CSP systems generally require direct sunlight and operate best in sunny, arid regions. They convert solar energy to heat then electricity, with efficiency dependent on temperature and concentration ratio of sunlight.
Energy Storage and Dispatchability
- CSP plants often integrate thermal energy storage, allowing electricity generation during non-sunny periods or at night, improving grid dispatchability.
- PV systems lack inherent thermal storage, relying on battery systems for electricity storage, which can be costly and less efficient at scale.
Scale and Installation
- PV systems are highly scalable and modular, functioning well from small rooftop installations to large solar farms.
- CSP plants require large-scale installations with significant infrastructure (mirrors, towers, turbines), and are economically viable mainly at large capacity levels (e.g., 100 MW or more).
Site Requirements
- PV can operate efficiently under various conditions, including diffuse solar radiation and cloudy weather.
- CSP requires high direct normal irradiance (DNI), limiting siting to sunny regions like deserts.
Cost and Economic Considerations
- PV technology costs have decreased rapidly, making it cost-effective for many applications. Cost depends on panel technology, scale, and installation.
- CSP historically has higher upfront capital costs due to complex infrastructure but benefits from thermal storage capabilities which can enhance value.
Environmental and Practical Considerations
- PV systems have relatively low environmental impact during operation with no water consumption.
- CSP plants may require significant water for cooling and carry risks like bird mortality due to intense solar flux near receivers.
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Aspect
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Photovoltaic (PV)
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Concentrating Solar Thermal Power (CSP)
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Conversion Method
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Direct light to electricity (DC, then AC)
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Solar energy → heat → steam → electricity (AC)
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Efficiency
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~17-20% commercially
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Higher potential efficiency with heat storage
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Storage
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Limited, battery-based
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Thermal energy storage enables dispatchability
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Scale
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Highly scalable, small to large
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Large-scale only (>100 MW)
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Site Requirement
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Works in diffuse and direct sunlight
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Requires high direct normal irradiance (sunny)
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Cost
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Lower upfront cost, rapidly declining
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Higher upfront capital cost, benefits from storage
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Environmental Impact
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Low, minimal water use
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Water use for cooling, some wildlife impact
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Weather Sensitivity
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Less sensitive to clouds
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Sensitive to cloud cover
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