S. Pester_How PV Systems Work
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Transcript of S. Pester_How PV Systems Work
How PV Systems Work
Steve Pester
Principal Consultant
BRE
Photovoltaics (PV)
PV panels generate electricity from sunlight
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")
Common Types of PV System
Tiles
Flat roof
Retrofitted to
pitched roof
Façade
Large PV Façade
PV Shading Applications
Sun shades integrated into blinds or glazing
Car
Parks
Cells, Modules, Arrays
Cell
Module (Panel)
Array
Cell Appearance
• Monocrystalline Silicon
• Polycrystalline Silicon
• Thin film
PV Cell Layers
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
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
Typical Domestic Installation
Commercial Buildings use 3-Phase Power
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
Batteries (normally only in off-grid systems)
• Very high short circuit currents
• Acid spills
• Heavy weights
• Possible hydrogen gas
2 Million Amp-hour battery
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
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?