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Sources - Solar
Technology
Solar photovoltaic (PV) panels utilise
light to produce DC current suitable for charging batteries or direct
connection to certain DC appliances such as fans and pumps.
There are three types of panel available;
| Mono-crystalline: |
High
quality and most expensive these are manufactured from thin
slices of silicon wafer. |
| Polycrystalline: |
Manufactured
from off-cuts of silicon wafer these are slightly cheaper than
mono-crystalline but with not quite such good performance. |
| Amorphous
or thin film silicon: |
Cheaper
to buy but performance will fade with time. |
The panels can be mounted in one of two
ways, (i) static, fixed angle facing due south, or (ii) tracking, where
the panels point at the sun all day (used more commonly in sunny
climates). In the UK it may be more cost effective to purchase a greater
number of panels instead of mounting them on moving frames.
 Mono-crystalline
Proven (http://www.almac.co.uk/proven/)
state that a 75W panel will give approximately 70kWh per annum. This
figure increases to over 100 kWh when installed in sunny climates. In
low light these panels do not perform as well as the Polycrystalline
variety.
Polycrystalline
Polycrystalline panels have a greater longevity than the other panels
available. These panels are reliable and provide good performance in low
light conditions on cloudy days, etc. However, in hot climates
performance is reduced.
 Amorphous
Amorphous panels are cheaper and unbreakable. However, a larger surface
area of panels is required to produce less concentrated energy
production.
 The
photovoltaic panels can be incorporated into a variety of different
systems, as listed below:
Grid Connected
The most popular type of solar PV system for homes and businesses in the
UK. The solar system is connected to the local electricity network
allowing any excess solar electricity produced to be sold to the
utility. Electricity is taken back from the network outside daylight
hours. An inverter is used to convert the DC power produced by the solar
system to AC power needed to run normal electrical equipment.
Grid Support
The solar system is connected to the local electricity network and a
back-up battery. Any excess solar electricity produced after the battery
has been charged is then sold to the network. Ideal for use in areas of
unreliable power supply.
Off-Grid
Completely independent of the grid, the solar system is directly
connected to a battery which stores the electricity generated and acts
as the main power supply. An inverter can be used to provide AC power,
enabling the use of normal appliances without mains power.
Hybrid System
A solar system can be combined with another source of power - a biomass
generator, a wind turbine or diesel generator - to ensure a consistent
supply of electricity. A hybrid system can be grid connected, stand
alone or grid support.
In relation to non-renewable energy
sources the advantages are obvious. Photovoltaic panels have no moving
parts and are therefore less susceptible to malfunction, they do not
require large industrial infrastructure and, unlike other energy
sources, silently perform their task. As a renewable energy, solar does
not contribute to Carbon Dioxide emissions.
Although prices vary between suppliers,
solar photovoltaic systems range between £6,700 to upwards of £20,000
(www.solarcentury.co.uk).
However, the government has recently offered grants of up to 50 per cent
for photovoltaic systems. Further information can be found on the Energy
Saving Trust website at http://www.est.org.uk/solar/index_solar.html.
In terms of financial savings, once
operational, photovoltaic systems save between £60 and £92 a year for
an average size household (BBC News May 2002, www.news.bbc.co.uk).
 It
is not always necessary to convert solar energy into electricity. It is
also possible to harness the suns radiation to generate heat. Energy
from the sun can be used to heat water for general use.
Solar panels, also known as
"collectors", can be fitted to a building's roof (image top
left). They use the sun's heat to warm water, or another fluid, which
passes through the panel. The fluid is then fed to a heat store (eg a
hot water tank) and helps provide hot water or central heating for the
building. The panels work throughout daylight hours, even if the sky is
overcast and there is no direct sunshine. Active solar panels can also
be used to heat swimming pools (image bottom left) or to provide heat
for agricultural and industrial processes. As with Photovoltaics, such
systems can be mounted on either a fixed or tracking frame. Hagbourne
Primary School in Oxfordshire installed eight solar panels to provide
their water heating requirements and now saves £500 a year on energy
bills.
Costs
 According
to www.greenenergy.org.uk
the cost of installing a solar hot water heater is between £500 and
£1500 for a DIY system, to £2500-£4500 for a commercially installed
system. These prices however, are dependent on the size of the system. A
typical installation in the UK has a panel of 3m2 to 4m2 with a storage
tank of 150-200L. However, the optimum size will depend on actual hot
water use.
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