Page 165 - Applied Photovoltaics

x acceptance by transport authorities, particularly on the grounds of safety
x standardised, reliable designs (although this is rapidly evolving)
x consumer acceptance
x mass-produced low-weight solar panels
x regenerative braking, which is necessary to maintain efficiency where
frequent stopping occurs (this is now well developed and being used
commercially in hybrid petrol-electric cars)
x establishment of recharging stations (which could themselves be powered by
photovoltaics).

Targets for zero or low emission vehicles, such as in California, accelerate the
development and use of electric cars in urban environments. This could stimulate the
use of photovoltaics in everyday commuter vehicles, to either directly power vehicles
through integration into the car panels or else be mounted at local photovoltaic
powered charging stations or at individual households (Ingersoll, 1992).

A critical component of solar powered cars is the battery. It must allow deep cycling,
yet have a longer life than present car batteries. Self-discharge rates are not critically
important but the charge capacity-to-weight ratio is. The availability of solar
recharging facilitates the inclusion of additional small loads on the battery, such as
ventilation fans in cars, which previously could not be accommodated during periods
of non-use, owing to battery discharge. Both amorphous and crystalline silicon-based
solar battery recharging kits are available as small modules that plug into car cigarette
lighter sockets.
At present, the design procedure for the photovoltaic array and electrical components
is less well defined than for the battery. Consequently, battery and photovoltaic
selections are typically made independently of each other. As with all photovoltaic
systems, user education is important. For solar cars, efficient driving is important to
ensure optimal use of the batteries and the solar input.

8.13 LIGHTING
In the USA alone, there are thousands of photovoltaic-powered lighting systems
installed (Ball & Risser, 1988; Florida Solar Energy Center, 1998). The majority of
these (80%) are in the 200–400 W p range. In most remote areas of the world,
photovoltaic-powered DC lighting is now quite cost-effective compared with
kerosene lamps, batteries, candles, or diesel or petrol generators, and far more
economical than grid extensions. Even in urban areas, photovoltaic lights are often
used to avoid the high cost of running either underground or overhead power lines.
Such items as off-the-shelf garden lights, which can be installed without an
electrician, are gaining popularity.
Some of the current applications for photovoltaic lighting include:
x billboards
x security lighting
x public transport shelters
x emergency warning lights
x area lighting (e.g. race tracks, streets)

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