Environmental Engineering Reference
In-Depth Information
proximity so that transmission losses are minimized. The totality of the installed capacity in
a microgrid is capable of supplying the local demand. Microgrids promise substantial
environmental benefi ts by facilitating the integration of renewables such as PV arrays and
small wind turbines. The microgrid principle is heavily reliant on micro-CHP generators
that are driven by the production of heat mostly during winter and PV generators that provide
electrical energy during summer. Some storage capability is also assumed. The correct
mix is obviously important but would be facilitated by the diversity of the consumer
group.
Virtual Power Stations
Virtual power stations are a new concept. A virtual power plant is defi ned by Wikipedia as a
cluster of distributed generation installations (such as micro-CHP, wind turbines, small hydro,
back-up gensets, etc.) which are collectively run by a central control entity. Concerted opera-
tion of this plant can in theory provide network services such as power balancing and fre-
quency control. The concept is a response to market mechanisms that penalize the variability
and lack of predictability of small individual generators, particularly those based on renew-
able energy sources. However, since these aggregations are expected to refl ect commercial
arrangements that might involve highly dispersed plant, rather than geographically specifi c
clusters, the operation of such virtual plants might confl ict with the requirements for local
power and voltage control. These issues are the topic of ongoing research and so far there is
no clear consensus on the value of this approach.
8.7 Conclusions [11, 12]
The nationwide and local electricity grids, metering systems and regulatory arrangements that were
created for a world of large-scale, centralised power stations will need restructuring over the next
20 years to support the emergence of far more renewables and small-scale, distributed electricity
generation [11] .
Intermittency is not a ' fl aw' or shortcoming as traditional 'reliability' concepts imply. On the
contrary, requiring a system to always deliver generation that matches a fl eeting peak load gives
rise to a set of generation and network assets that are invariably drastically overspecifi ed and
underemployed, a situation long overdue for frontal attack by innovative policy [12].
When a new process technology - wind - is 'shoe-horned' into an existing system that evolved to
support previous vintage technology, things do not work correctly. To the network operator it may
seem as plain as day that the new technology needs to morph so that it take on the characteristics
resembling the old technology. This is wasteful and foolish. Quite the opposite must happen. If
we were to effectively exploit technological progress, it is the underlying system that needs to
metamorphose and adjust to the innovation [12] .
Compared to the breathtaking speed of developments in IT, the technology of power gen-
eration and distribution is depressingly lethargic. One reason is that the natural lifecycle of
asset renewal in power systems is measured in decades rather than years. In truth, the vast
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