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close this bookEco-restructuring: Implications for sustainable development (UNU, 1998, 417 pages)
close this folderPart I: Restructuring resource use
close this folder7. Photovoltaics
View the document(introductory text...)
View the documentIntroduction
View the documentThe technological potential of PV
View the documentPV costs
View the documentA PV market diffusion strategy
View the documentPossible PV adoption and diffusion scenarios
View the documentConcluding remarks: PV and eco-restructuring
View the documentNotes
View the documentBibliography


1. The PV cell conversion efficiency is normally defined as a ratio:
(electric power produced by the cell)/(light power arriving on cell surface under standard conditions)
The standard conditions are: air-mass (AM) = I (no clouds); temperature (T) = 25°C; incident light power density = 1 kW/m2.

2. The energy payback time is the time required for the energy system to "repay" the energy needed for its construction.

3. As far as quantitative results are concerned, it was assumed that PV substituted for electricity produced by the European mix of supply sources, and the thermal energy recovered substituted for heat produced by natural gas.

4. Including consumer indoor applications and large tax-subsidized grid-connected government demonstration projects.

5. Prices in constant 1994 US$.

6. This was announced at the 1st PV World Conference, Hawaii, December 1994.

7. For 1 ECU = US$1.2.

8. The potential for this application sector has been estimated at 300 MWp for Switzerland alone. This potential market is five times the present total world PV market.

9 Summer electricity consumption due to air-conditioning systems has increased heavily in recent years in both industrialized countries and developing countries. To mention just a few European cases: Greece's newly installed air-conditioning capacity increased nine-fold between 1987 and 1990 while in Italy, Spain, and Portugal the use of air-conditioning has been growing at a rate of 20 per cent per year (Ambiente Italia 1995).

10. Assuming 1,800 kWh/m2 annual average insolation and a 6 per cent real discount rate. In the longer term, some thin-film or concentrator technologies can be expected to supply electricity at 3.5-7.0 cents/kWh (Kelly 1993). PV electricity costs of course depend on several factors, some of them being technology specific (module and system efficiencies, lifetimes, and installation costs), others being site specific (insolation) or economic, such as capital cost discount rates.

11. Many of these issues also require an international cooperation effort (never before seen) to define international standards and rules tackling global environmental issues.

12. It is worth remembering that, within OECD countries, the average per capita available surface on roofs alone has been estimated to be 10 m2 (van Brummelen and Alsema 1994). Were such an area available for every person worldwide, even with present PV technology available on the market today, this would correspond to an installed capacity of around 5,500 GWp and yearly electricity production of about 9,300 TWh/y. This value exceeds present total world electricity demand.

13. Several other scenarios were taken into account and adapted to extrapolate worldwide PV diffusion WEC (1994), TERES (1994), NREL (1990), Johansson et al. (1993). The mean installed PV capacity was always calculated from annual electricity by considering a daily mean insolation of 4.6 kWh/m2/day.

14. By assuming regional solar energy demand shares as indicated in the WEC (1994) scenario.

15. Hydrogen storage is currently the major technological issue in hydrogen energy technology.