s. pester_how pv systems work
TRANSCRIPT
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How PV Systems Work
Steve Pester
Principal Consultant
BRE
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Photovoltaics (PV)
PV panels generate electricity from sunlight
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PV Origins
• Principle discovered in 1839 by Edmund Becquerel in
France
• Solar panels were used for the first time in 1958 to
generate electrical power (0.1 W) for the US Vanguard
spacecraft
1.47 kg aluminum sphere
dia = 165 mm (6.4")
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Common Types of PV System
Tiles
Flat roof
Retrofitted to
pitched roof
Façade
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Large PV Façade
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PV Shading Applications
Sun shades integrated into blinds or glazing
Car
Parks
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Cells, Modules, Arrays
Cell
Module (Panel)
Array
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Cell Appearance
• Monocrystalline Silicon
• Polycrystalline Silicon
• Thin film
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PV Cell Layers
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How PV Works
Photons deliver enough energy to liberate carriers which are then accelerated through the
field and on to the contact terminals
0 10
Amps
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Most PV systems in the UK are
“Grid Connected”
• No batteries required
• Very low maintenance
• Export of surplus power
• Future-proofs property
against energy price
rises
• Earns income from
Feed-In Tariff
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Typical Domestic Installation
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Commercial Buildings use 3-Phase Power
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Standalone PV system for a building
(i.e. not grid-connected)
Controller
Storage Battery e.g.
lead acid deep cycleDC loads
Inverter
AC loads
External
PV array
More Batteries to
suit design load and
generation
Other generators:
E.g. diesel
Wind
Hydro
Normally found on remote buildings
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Batteries (normally only in off-grid systems)
• Very high short circuit currents
• Acid spills
• Heavy weights
• Possible hydrogen gas
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2 Million Amp-hour battery
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Safety – Why PV has Special Safety Issues:
• Beware High Voltage DC Electricity – Dangerous! few electricians are familiar with DC
• The PV modules cannot be switched off (upstream of the DC isolator)
• Fuses are not likely to blow under short circuit conditions
• Combination of hazards in fires: Falling glass, high voltages during daylight
• Micro-inverters (next presentation) may reduce some of the risks
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Summary
• PV technology is simple in principle
• It is widely used in many countries with few real problems
• There are potential hazards, but these are minimised by
using good products correctly installed (MCS)
• High voltage DC electricity is a special hazard
• Batteries are a hazard on off-grid systems
• Questions?