CPD Programme
Technology Thin film Crystalline water based
Amorphous Cadmium Cl(G)S a-Si/m-Si Monocrystalline Multicrystalline
silicon (a-sl) telluride (CdTe)
Cell Efficiency at 5–7% 8–11% 7–11% 8% 16–19% 14–15%
STC*
Module 13–15% 12–14%
Efficiency
Area needed 15m
2
11m
2
10m
2
12m
2
app. 7m
2
app. 8m
2
per kW** (for
modules)
* Standard testing conditions: 25C, light intensity of 1,000W/m
2
, air mass = 1.5
** kW = kilowatt. Solar PV products and arrays are rated by the power they generate at Standard Testing Conditions
Figure 4 Efficiency of various PV modules
European Standard consumed during production. The energy
Photovoltaic modules
EN 5316-4-6:2007 (E) payback time is determined from a life cycle
This constitutes the specific part related to
Inverter
analysis of energy.
building integrated photovoltaic systems, of These exercises show that the energy
To utility
the set of EN 15316 standards on methods for
company
intensity of typical solar photovoltaic
calculation of system energy requirements technologies is rapidly evolving. In 2000 the
and system efficiencies of space heating energy payback time was estimated as eight
Junction box
Distribution
systems and domestic hot water systems in
board
to 11 years, but more recent studies suggest
buildings. This European Standard presents
Data collection unit
that technological progress has reduced this
a method for calculation of the electricity to 1.5 to 3.5 years for crystalline silicon PV
Display unit
production of building integrated photovoltaic systems.
systems. Thin film technologies now have energy
Figure 5 Commercial building application of PV
Building-integrated photovoltaics (BIPV) pay-back times in the range of 1 to 1.5 years
are increasingly incorporated into new in southern Europe. With lifetimes of such
domestic and industrial buildings as a systems of at least 30 years, the EROEI is
principal or ancillary source of electrical
If the energy input to
in the range of 10 to 30. They thus generate
power, and are one of the fastest growing
produce and maintain the
enough energy over their lifetimes to
segments of the photovoltaic industry. reproduce themselves many times depending
Typically, an array is incorporated into the
panel is higher than the
on what type of material, balance of system
roof or walls of a building, and roof tiles with
output it produces it can be
and the geographic location of the system.
integrated PV cells can now be purchased.
considered environmentally
The development work has resulted in
Arrays can also be retrofitted into existing modules that require very low maintenance
buildings; in this case they are usually fitted
more harmful than
and are highly reliable with a good level of
on top of the existing roof structure.
beneficial
predictability in its output/performance.
Alternatively, an array can be located Latest module design incorporates:
separately from the building but connected by input to produce and maintain the panel is • reliability
cable to supply power for the building. Figure higher than the output it produces, it can be • improved efficiency
5 is an example of photovoltaic installation considered environmentally more harmful • added safety features, conforming with
for a commercial type building. Depending than beneficial. This should not be confused IEC61215, 2nd edition
on the PV output and the building demand, with the economic return on investment, • environmentally friendly with lead free
electricity will be supplied by the PV system which varies according to local energy soldering.
completely, or topped up from the grid, prices, subsidies available and metering © Terry Welch
delivered completely by the grid, or supplied techniques.
to the grid. Another factor to consider is the placement References
of photovoltaic arrays. If they are located CIBSE TM25, 2000, Understanding building
Environmental and economic where photosynthesizing plants would integrated photvoltaics
performance normally grow, they simply substitute one Ref 1, Earth Policy Institute, www.earth-policy.
Unlike fossil fuel based technologies, solar potentially renewable resource (biomass) for org/index.php?/indicators/C47/Mitsubishi
power does not lead to any harmful emissions another. It should be noted, however, that the Electric – Photovoltaics PV-TD185MF5
during operation, but the production of the biomass cycle converts solar radiation energy British Standard, BS EN 15316-4-6:2007(E),
panels leads to some amount of pollution. to chemical energy (with significantly less Part 4 – 6, Heat generation systems,
This is often referred to as the energy input efficiency than photovoltaic cells alone). The photovoltaic systems.
to output ratio, or the energy returned on energy payback time is the time required to AJ Specification, 01, 2007, Powerful
energy invested (EROEI). If the energy produce an amount of energy as great as that arguments for solar roofing.
www.cibsejournal.com January 2010 CIBSE Journal 61
CIBSEjan10 pp59-62 cpd.indd 61 17/12/09 16:30:13
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