Page 211 - Applied Photovoltaics

Figure 10.9. Possible placement of a PV station in a grid prone to thermal
overload.

By generating electricity locally, the amount of power to be transmitted along the
distribution line is reduced, delaying the need for upgrading. In addition, just by
reducing the current through a transformer prior to its peak load, its lower
temperature allows it to carry a higher peak without overheating (Wenger et al.,
1994).
PV can also be used for demand side management, to the benefit of both the utility
and customer. For instance, PV systems on the rooftops of large electricity users can
reduce peak load energy and demand. With lighting accounting for up to 40% of the
electricity requirement of commercial and light industrial buildings, PV assisted
lighting systems could be a simple and feasible means of reducing summer peak loads
(Berg & Wieghagen, 1991).

The distributed utility concept is becoming more attractive as planning becomes less
dominated by the concept of economies of scale (Iannucci & Shugar, 1991). In
modern utilities, cost minimisation relies also on such aspects as generator placement,
line losses, transmission upgrade costs and reliability. Central power stations can
therefore be integrated with modular, strategically placed, distributed generation to
increase the system’s sustainability, efficiency, strategic power delivery and customer
service. The central stations would then be used to supply the base load, for which
they are best suited, while customers would be provided with a more reliable and
higher quality power supply, tailored to meet local demand. More flexibility in
customer supply could also be incorporated, with such options as DC supply, load
management and storage (Ibid.). Suitable metering systems and tariff structures are
needed to facilitate such options.

New utility planning tools are required to assess these concepts, as well as to
incorporate consideration of such issues as:
x environmental, social or other externality values of renewable energy sources
x benefits of fuel diversity
x security value attributed to the risk of investment in plant requiring
indigenous vs non-indigenous fuels
x reduced risk inherent in incremental, rather than large step changes in supply
infrastructure

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