Page 111 - Applied Photovoltaics

x solar powered vehicles (e.g. golf carts, solar cars, boats on reservoirs where
petroleum products and noisy motors are restricted)
x lighting (e.g. billboards, street and garden lights, security lighting, emergency
warning lights)
x remote monitoring (e.g. weather, pollution, highway conditions, water
quality, river heights and flow rates)
x remote meter reading
x gas flow metering
x direct drive applications (e.g. ventilation fans, toys)
x electric fences (e.g. to keep dingos and kangaroos out or stock in)
x remote gates
x remote community power supplies
x remote homestead and household power supplies (usually in a hybrid system)
x power for residential or commercial use where there is grid connection
x power for sectionalising switches along remote sections of electricity grids
x ‘distributed photovoltaics’—numerous appropriately-sized arrays feeding into
distribution power grids at dispersed sites
x central power plants.

Some of the main applications will be discussed in more detail in the following
chapters.

The majority of the above are stand-alone systems, with a wide range of loads, sites
and required availabilities, making system design a complex exercise. In some
applications, even estimating the load can be quite a difficult task. Grid-connected
applications are of increasing interest and have now overtaken stand-alone systems as
the main market for photovoltaic modules worldwide. Some options for grid-
connected and stand-alone power supply systems are illustrated in Fig. 6.1.
The high cost of extending the electricity grid to customers has meant that many
communities, properties and households around the world rely on diesel, petrol or
renewable energy-based power supply systems. This applies particularly to countries
such as Australia where there are large remote areas and difficult terrain. Photovoltaic
systems offer an attractive option or supplement to the older technologies. They are
widely used in small systems, and are being used increasingly in larger systems.

The cost-effective region for using a stand-alone system, versus connecting to the
grid, varies with load, distance from the grid and the stand-alone system chosen. For
instance, in Australia in the 1980s, for a grid-connection cost of A$40,000 the annual
load would need to be at least 6000 kWh for the grid to be more cost-effective than a
stand-alone system (Harrington, 1986). For smaller loads, say less than
3000 kWh/year, a stand-alone system would have been more cost-effective once grid
connection costs exceeded about $A20,000 (Ibid.). The Australian Greenhouse Office
(2003a) indicates that current grid-connection costs are typically A$10,000 per
kilometre of line and, although electricity prices have dropped over the last two
decades, PV and hybrid system prices have also fallen by up to 40% in real terms
(Watt, 2004).

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