MAIN POINTS
  • Solar PV can achieve gigaton scale by 2020 for an investment of $2.1 trillion, creating more than 1.5 million direct jobs and enhancing energy security through distributed power generation.
  • At current growth rates solar PV is on track to abate half a gigaton CO2e by 2020 and be cost competitive with current electricity prices within the next 5 years.
  • Solar PV is already price-competitive for peak power rates in a number of markets.
  • Successful policies, grid integration, and storage are critical to scaling PV.
  • Enough rooftop space exists in the U.S. alone to achieve gigaton scale.
Download the chapter of "Solar Photovoltaics" (PDF: 1.1 MB)
Solar photovoltaic (PV) technology converts sunlight directly into electricity by means of semiconductors. To mitigate 1 gigaton of carbon dioxide equivalent emissions (CO2e) per year, cumulative solar PV installations would have to reach 1,000 gigawatts of peak power (GWp) by 2020. In 2008, cumulative U.S. PV installations reached 1 GWp, providing less than 1% of consumed electricity. Globally, installations in 2008 totaled 14 GWp. Between 2006 and 2008, the industry experienced a 50% global growth rate, with demand rising from 2 GW to 3 GW between 2006 and 2007 and to 4.5 GW between 2007 and 2008. If this growth rate could be sustained, a worldwide gigaton target would be reached by 2022. The economic slowdown of 2009 has led to a more conservative estimate for 2009 growth of closer to 15% although growth could recover with economic stability. Meeting the gigaton challenge by 2020 would require an accelerated growth rate of 46% post-2009 and capital investment upwards of $2.1 trillion. Of particular recent importance is the growth of utility-scale PV projects - some over 100 megawatts (MW) for a single solar farm - and aggressive clean energy policies, such as more serious discussions of carbon prices and the introduction of feed-in tariffs in a number of nations, and discussions at both the state and federal level in the U.S.

The costs for solar PV have been falling, and with the alleviation of a past supply bottleneck in silicon, the most common semiconductor used in today's solar cells, PV is on track to be a cost-competitive electricity source. Although PV is forecast to reach grid parity within the next 5 to 10 years and thus to be competitive with other electric power options, significant hurdles, including technical and materials constraints, must be cleared to allow rapid expansion. If these hurdles can be surmounted, PV will be a very attractive technology. Policies and regulations that have benefited PV in the past will need to be extended to support gigaton-scale ramp-up. Investment in stable policy support and expanded installations will have several benefits beyond bringing down cost. The distributed nature of PV power has security benefits, allowing those served to avoid the effects of power outages in a grid failure. PV is also insulated from fuel price shocks.

Solar PV's ability to provide peak power makes it attractive for meeting daytime power needs when electricity demand is highest. Peak power is the most costly; at peak power rates in the most expensive electricity markets in the U.S., such as California, solar PV is cost competitive today.

Without storage, solar PV is off line at night and when sunshine is unavailable, e.g., during cloudy periods. In the future, as higher grid penetration levels for solar PV are reached, this intermittency may be a concern for utilities. At current penetration levels, backup generation is not an issue, but, for high penetration levels of solar PV, the technology may need to be paired with firming generators, particularly in regions with intermittent sunshine. Back-up generation will increase system-wide costs by a marginal amount that has not yet been fully evaluated.

A major shift in markets would be needed to scale PV to the gigaton level. More than 80% of new worldwide solar PV capacity in 2008 was installed in four countries: the U.S., Germany, Japan, and Spain. Owing to the maturity of the electricity market, total installed demand in the U.S. is projected to rise by only 190 GW by 2020, meaning that the gigaton goal cannot be achieved in the U.S. solely by satisfying new demand with PV or even by replacing much of the existing capacity with solar systems. Expanding PV penetration to meet the gigaton goal would require not only expanding established markets around the world like Germany and Japan but extending deep into emerging markets like China and India. Already the bulk of solar module manufacturing capacity is in China and India although most of what is produced is exported.

A gigaton-scale expansion of solar PV would add an estimated 1.5 million direct jobs.