Photovoltaics

Photovoltaic modules are solid-state devices that convert sunlight directly into electricity with no rotating equipment. Photovoltaic systems can be built in any size, are highly reliable, and require little maintenance.

World-wide photovoltaic sales are about 100MW annually. The major problem limiting the widespread use of photovoltaics is the cost of manufacturing the sheets of semiconductor materials needed for power systems.

At today's efficiencies a piece of desert land about 2 miles square could host a solar electric generating plant with the power production capacities of a large nuclear or coal plant.

Despite their high costs, photovoltaic systems are cost-effective in many areas remote from grids, where another sources are impractical or costly. For grid-connected distributed systems, the value of photovoltaic electricity can also be high because the electricity is produced during period of peak demand, thereby reducing the need for conventional peaking capacity. Photovoltaic equipment may be installed close to the sites where it is consumed, thereby reducing transmission and distribution expenses together with increasing reliability. Small, grid-connected photovoltaic systems may be competitive today where distributed generation has particularly high value. Many such niche applications will provide early markets for photovoltaics systems. As photovoltaic prices fall, markets will expand rapidly.

Photovoltaic prices have fallen sharply since the mid 1970’s although prices have stabilised over the last few years because demand has grown faster than supplies. There is, however, good reason to be confident that prices will fall substantially by the turn of the century. There are several alternative paths by which costs can be reduced. Systems based on thin films of materials such us amorphous silicon alloys, cadmium telluride, or copper indium diselenide are particularly promising, both because they are well suited for the application of mass-production techniques and because the amounts of active materials required are small. Another strategy calls for concentrating sunlight on small, highly efficient photovoltaic cells using inexpensive lenses or mirrors.

Assumptions

A projection of the cost of PV systems assumed in this analysis is given in Table 9 [11].

YEAR 1995 2000 2005 2010 2015 2020
             
Conversion Efficiency (%) 13 15 17 18 19 20
Module Cost (/Wp) 3 2.5 2.0 1.5 0.8 0.7
Power Conditioning Cost (/Wp) 0.5 0.4 0.3 0.2 0.15 0.1

Table 9: Future cost of PV systems in /Wp [11].

Other assumptions are:

  • Solar Insolation: 700kWh/m2
  • Discount rate: 8%
  • PV-Cladding lifetime: 30 years

The avoided costs are (Cladding costs-(Wiring + Fixing) costs):

Cladding costs

  • Standard glass curtain-wall with double glazing: 400/m2 to 450/m2.
  • Standard glass curtain-wall with single glazing: 300/m2 to 350/m2.

Wiring costs: 25/m2

Fixing costs:

  • Wall cladding: 25/m2
  • Curtain Wall : 175/m2

The cost of the PV electricity

The cost of the electricity can be predicted in p/kWp as[11]:

YEAR AVOIDED COSTS (/m2)
  -50 0 100 250
         
1995 47 43 33 19
2000 34 31 22 9.2
2005 27 23 16 4.2
2010 19 15 8.1 -2.4
2015 15 12 5.4 -4.6
2020 13 10 3.7 -5.7

Table 10: Avoided cost of PV electricity, in /m2 [11].

Solar Resource

All calculations have been done for the daytime period: 9:00-17:00 hs

Solar input:

  • Commercial buildings: 107MW/km2
  • Industrial buildings: 76.1MW/km2
  • Residential high rise buildings: 42.7MW/km2
  • Housing: 38.4 MW/km2

Site availability

CATEGORY 1995 2020
     
Commercial Sites:    
Land Area (m2) 578 578
Unsuitable Buildings (%) 38 24
Fenestration (%) 33 33
     
Industrial Sites    
Land Area (m2) 1426 1711
     
Residential Sites:    
High Rise-Land Area (m2) 129 N/A
High Rise-Fenestration (%) 25 N/A
Housing-Land Area (m2) 8230 9053
     
Photovoltaic Modules:    
Conversion Efficiency (%) 13 20

Table 11: Site availability for PVIB in m2 [11].

 

Total generating capacity between 9:00 and 17:00.

  1995     2020    
Building Power Total Electrical Power Total Electrical
Capacity Capacity Power Energy Capacity Power Energy
  Per m2 Capacity per year Per m2 Capacity per Year
  in MW in GW in TWh in MW in GW in TWh
             
Commercial 107.1 8.0 26.4 131.3 15.2 49.9
Industrial 76.1 14.1 46.3 76.1 26.0 85.5
             
Residential            
High Rise 42.7 0.72        
Housing 38.4 40.4 132.7 38.4 69.5 228.3
             
TOTAL         110.7 363.7

Table 12: Present PVIB generating capacity in the UK [11].

And the total generating capacity in GW for 2020 between 9:00 and 17:00., for different times of the year is

Premises Annual April December
  (Average) -September  
       
Commercial 15 23 3.7
Industrial 26 39 6.3
Domestic 70 103 17
TOTAL 111 165 27

Table 13: 2020 PVIB generating capacity in the UK, in GW [11].

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