Environmental Engineering Reference
In-Depth Information
5.5
Utilizing Solar Power with Photovoltaics: the Rooftops of New York versus Space
Satellites
One of the questions on many aspects of solar and renewable energy is the optimum
scale of the device or system. We have seen in Figures 5.4 and 5.5 concentrating solar
thermal installations on the scale of 11MW and 25 kW, respectively, with a good
indication that the present ef
ciency of the smaller installation is nearly twice that of
the large installation. (It is not clear what the cost in $/W comparison is, but it
probably favors the large system.) It has been argued above that much higher
ef
ciency than the present 15% should be available in the solar tower systems with
advances in engineering and in materials. We will see later that arrays of small
concentrating solar cells built into panels are commercially available using small
plastic Fresnel lenses (as suggested in Figure 5.1) and in a miniature form of the
parabolic reflector as shown in Figure 5.5. A long-standing suggestion has been for
concentrating arrays above the earth in space, with transmission of power to earth by
microwaves. The cost has so far been prohibitive. A large but small mass parabolic
mirror in space might be constructed cheaply from aluminum foil, or aluminized
mylar, to be unfurled after reaching orbit. The positioning of such power satellites
above large cities would avoid the dif
culty of building new power lines on earth. In
principle, an array of power satellites, following the lead of the GPS satellites, might
provide power 24 h. Many large cities are coastal or on large lakes, where the receiving
units could be located on barge arrays with underwater DC power lines to land.
The City of New York has recently carried out a careful mapping assessment of the
solar power capacity of its one-million-plus rooftops [57], concluding that 66.4% of
the buildings of the city had roof space suitable for solar panels. It was concluded that
5.847 GW could be generated putting solar panels on hundreds of thousands of
buildings. It was concluded that 49.7% of the citys peak power usage could be
generated from solar power and 14.7% of the citys annual electricity use, taking into
account typical weather conditions. David Bragdon, director of the Mayors Of
ce of
Long-Term Planning and Sustainability said the city could realistically add
thousands of megawatts in solar power. The city would likely establish a uniform
approach and presumably would negotiate with a company like First Solar to do the
installations. The budget of the city is $65.7 billion for 2012. Nominally, the
installation would cost around $5.8 billion that over 10 years would be 0.9% per
year of the city budget.
Such a project would be a large-scale deployment of small installations, and would
be in the power of the city tomandate. The article states that U.S. nationwide installed
solar capacity is 2.3GW, less than half the rooftop potential of New York City. We will
return in Chapter 11 to some of the issues regarding the deployment of renewable
energy resources, which on the national level is made dif
cult by the sway of vested
fossil fuel interests over the Congress. The existence of the Mayors Of
ce of Long-
Term Planning and Sustainability, able to obtain city funding of $450 000 for the
aerial survey, is in itself encouraging, and suggests that large cities may be an avenue
toward rational implementation of renewable energy systems.
