Environmental Engineering Reference
In-Depth Information
Thin fi lm PV has the potential to deliver cheaper electricity. Amorphous silicon was the
fi rst thin fi lm to become commercially available and in recent years has managed a steady
but limited market share [6]. Unfortunately, intrinsic materials issues have limited its perfor-
mance and it is not expected to be competitive in the longer term. Currently, commercial
interest centres around thin fi lm nanocrystalline hybrid cells and the heterojunction cells
based on copper indium diselenide and cadmium telluride. Both of the latter provide reason-
ably stable effi ciencies and are expected to benefi t from improved manufacturing techniques.
There is currently a fl urry of investment activity in these technologies that includes manu-
facturing on to glass, and metal and polymer foils.
Industry experts confi dently expect that the new mass production technologies will deliver
cells capable of generating electricity competitively with conventional forms and nuclear
perhaps within the next 10 years.
Different Deployment Options
The bulk of current grid-connected PV is located on domestic building roofs. Japan and
Germany between them have installed over a million such roof systems, primarily as a result
of generous market support mechanisms. A similar programme is now planned in the USA.
Earlier installations in the main made use of traditional looking modules, although there is
now increasing use of so-called PV roof tiles. These can be laid more or less in the same
way as traditional tiles and lend the roof a more traditional appearance. Alongside domestic
roofs, commercial buildings also provide attractive locations for PV where fl at roofs and
facades lend themselves to PV installation. There are numerous examples of architecturally
appealing PV facades to be found around the cities of Europe. There are thermal issues
associated with such building integration of PV. If not carefully designed, the mounting
systems can inhibit natural ventilation of the modules, leading to overheating with possible
damage to the PV cells in conditions of high radiation and ambient temperature. Fortunately
these issues are now fairly well understood.
In contrast to the various forms of building integrated PV, large scale arrays of PV modules
can be located on dedicated, usually rural, sites. Systems of up to 10 MW are being installed
in the sunnier parts of Europe. A computer image of the world's biggest solar power plant
under construction in Walpolenz, Germany, is shown in Figure 8.6. Once fully operational
Walpolenz will occupy about 110 hectares, will be rated at 40 MW and produce 40 GW h,
approximately the annual consumption of 10 000 households.
8.3.2 Solar Thermal Electric Systems
As outlined in Chapter 2, considerable effort has gone into the development of solar
thermal electricity generating systems. These are only feasible in large scale developments
and as a result the present solar thermal installations are larger than the PV based ones.
Figure 8.7 shows the 150 MW parabolic trough plant at Kramer Junction, California.
It has been calculated that if an area of hot desert of about 250
250 km - less than 1%
of the total areas of the world's deserts - were to be covered by such thermal plant enough
energy would be produced to cover all present electricity needs. Manufacturers of such
×
Search WWH ::




Custom Search