The sun provides a virtually unlimited, clean, and free fuel at a price that never changes. Solar farms take advantage of that resource, with large-scale arrays of hundreds, thousands, or in some cases millions of photovoltaic (PV) panels. They operate at a utility scale like conventional power plants in the amount of electricity they produce, but dramatically differ in their emissions.
Solar farms can be found in deserts, on military bases, atop closed landfills, and even floating on reservoirs, deploying silicon panels to harvest the photons streaming to earth. Inside a panel’s hermetically sealed environment, photons energize electrons and create electrical current—from light to voltage, precisely as the name suggests.
Bell Labs debuted silicon PV technology in 1954. At that time, photovoltaics cost more than $1,900 per watt in today’s currency. Since then, public investment, tax incentives, technology evolution, and brute manufacturing force have chipped away at the cost of creating PV, bringing it down to sixty-five cents per watt today.
In many parts of the world, solar PV is now cost competitive with or less costly than conventional power generation. In tandem with other renewables and enabled by better grids and energy storage, solar farms are ushering in the clean energy revolution.
life cycle emissions [vs.] coal plants: Schlömer, S., et al. “Annex III: Technology-Specific Cost and Performance Parameters.” In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, and New York: Cambridge University Press, 2014.
outdoor air pollution…premature deaths: WHO. Burden of Disease from Ambient Air Pollution for 2012. Geneva: World Health Organization, 2014.
utility-scale…additions to solar PV capacity: IRENA. Letting in the Light: How Solar PV Will Revolutionize the Electricity System. Abu Dhabi: International Renewable Energy Agency, 2016.
[proposed] Chernobyl…solar farm: Vidal, John. “Chernobyl Could Be Reinvented as a Solar Farm, Says Ukraine.” The Guardian. July 29, 2016.
Bell Labs…“solar battery”: Perlin, John. Let It Shine: The 6,000-Year Story of Solar Energy. Novato, California: New World Library, 2013.
“the beginning of a new era”: “Vast Power of Sun is Tapped by Battery Using Sand Ingredient.” New York Times. April 26, 1954.
At that time…$1,900 per watt: Mathiesen, Karl. “What is Holding Back the Growth of Solar Power?” The Guardian. January 31, 2016.
use [by] the oil industry: Perlin, Shine.
sixty-five cents per watt today: Weiser, Matt. “Here Comes the Sun: US Solar Power Market Hits All-Time High.” The Guardian. June 28, 2016.
cost competitive with…conventional power: IRENA, Solar PV.
bid[s]…at pennies per kilowatt-hour: Dipaola, Anthony. “Cheapest Solar on Record Offered as Abu Dhabi Expands Renewables.” Bloomberg. September 19, 2016.
panels rotate…generation can improve: Greentech Media. “Solar Balance-of-System: To Track or Not to Track, Part I.” November 28, 2012.
annual carbon dioxide savings [from PV]: IRENA, Solar PV.
20 percent of global energy needs by 2027: Farmer, J. Doyne, and François Lafond. “How Predictable is Technological Progress?” Research Policy, 45 (2015): 647–665.
solar PV…in Italy…Germany and Greece: REN 21. Renewables 2016 Global Status Report. Paris: REN21 Secretariat, 2016.
Deletion: [...] which tends to pick up at night.
Project Drawdown defines solar farms as: utility-scale solar photovoltaic (PV) systems for electricity generation. This solution replaces conventional electricity-generating technologies such as coal, oil, and natural gas power plants.
Since 2010, the photovoltaic market has grown tremendously. At least 227 gigawatts of total solar PV capacity were installed worldwide by the end of 2015, and in the same year the global PV market added a record 50 gigawatts of grid-connected capacity (IEA PVPS, 2015). In many regional markets, newly installed capacity came primarily from utility-scale installations rather than distributed or rooftop PV panels. Most adoption scenarios in the literature predict low, single-digit percentages of total electricity for solar photovoltaic generation by the mid-point of the century, but some, such as the Greenpeace Energy [R]evolution scenarios, envision it holding a much larger share of future electricity generation (near 20 percent of the electricity generation mix) (Greenpeace, 2015). These projections are based on increases in solar cell efficiencies and rapid declines in costs for PV installations, making them competitive with conventional generating sources in many parts of the world.
To capture the appropriate level of agency, the solar PV market was split between rooftop solar (representing households and building owners) and utility-scale solar (i.e. solar farms).
Total Addressable Market 
The total addressable market for solar farms is based on projected global electricity generation in terawatt-hours from 2020-2050, with current adoption  estimated at only 0.5 percent (113 terawatt-hours) of generation (IRENA, 2016). With no definitive estimation of the type of future solar PV adoption, it is assumed that rooftop installations represent around 40 percent of the market, with utility-scale solar capturing the remaining 60 percent (US DOE, 2012; IEA, 2014; SEIA, 2014).
Adoption Scenarios 
Impacts of increased adoption of solar farms from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels
- Plausible Scenario: This scenario is based on the evaluation of five optimistic scenarios from the EU project AMPERE (2014),  the 2°C Scenario of the International Energy Agency’s Energy Technology Perspectives (2016), and the Greenpeace Energy [R]evolution Scenario (2015) using a high growth trajectory.
- Drawdown Scenario: This scenario is aligned with the Greenpeace Advanced Energy [R]evolution Scenario. 
- Optimum Scenario: Like the Drawdown Scenario, this scenario is aligned with the Greenpeace Advanced Energy [R]evolution Scenario.
To capture the rapid decrease of costs seen in recent years, the low boundary of data collected on installation costs is assumed, which results in a total first cost of US$1,445 per kilowatt.  A customized learning rate of 19.66 percent was developed, accounting for independent impact on PV modules and balance of systems; this has the effect of reducing the installation cost to US$692 per kilowatt in 2030 and to US$483 in 2050, compared to US$1,923 per kilowatt for the conventional technologies (i.e. coal, natural gas, and oil power plants). An average capacity factor of 22 percent is used for the solution, compared to 55 percent for conventional technologies.
Through the process of integrating solar farms with other solutions, the total addressable market for electricity generation technologies was adjusted to account for reduced demand resulting from the growth of more energy-efficient technologies,  as well as increased electrification from other solutions like electric vehicles and high-speed rail. Grid emissions factors were calculated based on the annual mix of different electricity generating technologies over time. Emissions factors for each technology were determined through a meta-analysis of multiple sources, accounting for direct and indirect emissions.
Comparing the results from the three modeled scenarios to the Reference Scenario allows us to estimate the climate and financial impacts of increased adoption of utility-scale PV systems. The Plausible Scenario projects 10.33 percent of total electricity generation worldwide coming from utility-scale solar by 2050. In the Drawdown and Optimum Scenarios, the market share reaches 15.1 percent and 15.8 percent, respectively.
The Plausible Scenario results in the avoidance of 36.9 gigatons of carbon dioxide-equivalent greenhouse gas emissions between 2020-2050, with US$80.60 billion in savings from associated net first costs. Nearly US$5 trillion of net operating savings are projected over the same period, principally because utility-scale PV does not require any fuel inputs. Both the Drawdown and Optimum Scenarios are more ambitious in the growth of utility-scale PV technologies, with impacts on greenhouse gas emissions reductions over 2020-2050 of 64.6 and 60.5 gigatons of carbon dioxide-equivalent, respectively.
Solar photovoltaic has seen unprecedented levels of growth around the world since 2005, due primarily to advancements in technology and declines in costs. Only modest advancements in production are needed before utility-scale systems are cost-competitive with fossil fuel generation around the world. As a result, utility-scale PV is likely to continue its rapid growth in many regional markets and will play an increasingly important role in future global electricity supply, regardless of climate mitigation goals. If utilities and project developers, spurred on by local and national governments, accelerate the adoption of utility-scale solar over the next 30 years, the world will reap major benefits in terms of greenhouse gas emissions reduction, as demonstrated by our results. The rapid deployment of utility-scale PV will result in significant reductions in greenhouse gas emissions (and corresponding atmospheric concentrations) by displacing emissions associated with coal and natural gas. Solar has an incredibly promising long-term potential, as solar resources are plentiful and widespread, and future advances in both battery and photovoltaic technologies should continue to drive the adoption of this technology, even without specific policy interventions. The financial benefits of rapid utility-scale PV adoption will also be considerable, and these can help jumpstart adoption. There are significant investment costs associated with accelerated adoption, but this is an opportunity to generate wealth and economic growth, as the return on investment is also substantial.
The accelerated installation of new utility-scale PV capacity will not be without challenges, however, as traditional electricity markets and grids are in many cases not primed for a high penetration of intermittent, renewable energy. There will be economic, policy, and social hurdles to overcome on the pathway set out in our scenarios, and some of these will require significant changes to the way we buy, sell, and even use electricity. But given the immense climate and financial impacts of global utility-scale PV adoption, it is imperative that we take on these challenges in order to realize the benefits.
 For more about the Total Addressable Market for the Energy Sector, click the Sector Summary: Energy link below.
 Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.
 To learn more about Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Energy Sector-specific scenarios, click the Sector Summary: Energy link.
 The adoption from the 450 scenarios of three AMPERE models (GEM E3, MESSAGE, and IMAGE) was used.
 It represents an ambitious pathway towards a fully decarbonized energy system in 2050, with significant additional efforts compared to the Energy [R]evolution Scenario. The Advanced Energy [R]evolution Scenario needs strong efforts to transform the energy systems of all world regions towards a 100 percent renewable energy supply.
 All monetary values are presented in US2014$.
 For more on Project Drawdown’s Energy Sector integration model, click the Sector Summary: Energy link below.
 For example: LED lighting and heat pumps.