Environmental Engineering Reference
In-Depth Information
regions to meet growing urban demand. One source estimates current alternative energy
“farm” proposals would cover 2.3 million acres.*
The grid, even if new variants are pronounced “smart” by promoters, remains a resource-
export technology (see Chapter 29). In the 1920s, as the Rural Electrification project, it
was a marvel of engineering. At that time, there were few technologies for clean, small-
scale, on-site electric generation. But today's photovoltaic and wind-electric (and recently
announced fuel cell) technologies are efficient at small scales, and their main advantage is
that they can generate electricity
at the point of use
, bypassing transmission and its many
associated problems. Those problems include
• Transmission losses between generation and use due to voltage drop. Step-up and
step-down transformers also lose some energy at each transformation. The energy
is not actually “lost,” but converts to heat.
• Complete lack of energy-storage capacity. Almost all “alternative” energy
generating systems incorporate storage, by necessity. The grid only simulates
storage, by shunting energy around the grid for slightly later use. This actually
increases the overall transmission losses, which are distance-dependent.
• Costs (in materials, money, land, and fuels) of constructing, operating, and
maintaining a far-flung linear system. Routed through undeveloped areas, the grid
requires access roads, costly both in financial and environmental terms. Because
the grid is linear, breaks and failures can occur anywhere along its length, and can
be difficult to locate or access for repair. By contrast, on-site generation involves
many points of generation, but each is self-contained, almost always served by
existing roads, at a known location and of a small size, making diagnosis and
access relatively easy.
• Massive site impacts of “farms” covering hundreds of acres with solar panels or
300-foot-tall wind turbines.
• Large differences (two or more orders of magnitude) in voltage for generation,
transmission, and use. Centralized generating plants operate at high voltage; long-
distance transmission requires even higher voltage; but consumers (except for a few
industrial users) require rather low voltages (110 or 220). Dispersed on-site systems
generate at voltages near those that are actually used; inversion (from DC to AC)
is required primarily because the grid has made AC standard. When a dispersed
generator is “grid-tied” to sell energy back to the grid, it is typically generating at low
voltages (6-48 V), which are inefficiently coupled into higher transmission voltages.
• Dificulty matching generation to demand. Demand for electricity varies daily
and seasonally, but large power plants are not easily or quickly adjustable. Many
such plants are oversized in order to meet peak demand, greatly increasing overall
wastefulness. Because generation is out of sight and mind, centralization arguably
encourages thoughtless consumption. Local generation, by contrast, enforces
planning and conservation.
• Vulnerability. Centralized systems are very exposed to disruption by terrorism,
sabotage, or natural disaster; widespread disruption of on-site generators would
be difficult.
*
http://www.solarpowerninja.com/solar-power-government-industry-news/solar-energy-sparks-desert-real-
estate-boom/ (accessed March 2, 2010).
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