Photovoltaic power station

A photovoltaic power station, also known as a solar park, solar farm, or solar power plant, is a large-scale grid-connected photovoltaic power system designed for the supply of merchant power. They are different from most building-mounted and other decentralized solar power because they supply power at the utility level, rather than to a local user or users. Utility-scale solar is sometimes used to describe this type of project.
This approach differs from concentrated solar power, the other major large-scale solar generation technology, which uses heat to drive a variety of conventional generator systems. Both approaches have their own advantages and disadvantages, but to date, for a variety of reasons, photovoltaic technology has seen much wider use., about 97% of utility-scale solar power capacity was PV.
In some countries, the nameplate capacity of photovoltaic power stations is rated in megawatt-peak, which refers to the solar array's theoretical maximum DC power output. In other countries, the manufacturer states the surface and the efficiency. However, Canada, Japan, Spain, and the United States often specify using the converted lower nominal power output in MW_AC, a measure more directly comparable to other forms of power generation. Most solar parks are developed at a scale of at least 1 MW_p. As of 2018, the world's largest operating photovoltaic power stations surpassed 1 gigawatt. At the end of 2019, about 9,000 solar farms were larger than 4 MW_AC, with a combined capacity of over 220 GW_AC.
Most of the existing large-scale photovoltaic power stations are owned and operated by independent power producers, but the involvement of community and utility-owned projects is increasing. Previously, almost all were supported at least in part by regulatory incentives such as feed-in tariffs or tax credits, but as levelized costs fell significantly in the 2010s and grid parity has been reached in most markets, external incentives are usually not needed.

History

The first 1 MW_p solar park was built by Arco Solar at Lugo near Hesperia, California, at the end of 1982, followed in 1984 by a 5.2 MW_p installation in Carrizo Plain. Both have since been decommissioned. The next stage followed the 2004 revisions to the feed-in tariffs in Germany, when a substantial volume of solar parks were constructed.
Several hundred installations over 1 MW_p have since been installed in Germany, of which more than 50 are over 10 MW_p. With its introduction of feed-in tariffs in 2008, Spain briefly became the largest market with some 60 solar parks over 10 MW, but these incentives have since been withdrawn. The USA, China, India, France, Canada, Australia, and Italy, among others, have also become major markets as shown on the list of photovoltaic power stations.
The largest sites under construction have capacities of hundreds of MW_p and some more than 1 GW_p.

Siting and land use

The land area required for a desired power output varies depending on the location, the efficiency of the solar panels, the slope of the site, and the type of mounting used. Fixed tilt solar arrays using typical panels of about 15% efficiency on horizontal sites, need about /MW in the tropics and this figure rises to over in northern Europe.
Because of the longer shadow the array casts when tilted at a steeper angle, this area is typically about 10% higher for an adjustable tilt array or a single axis tracker, and 20% higher for a 2-axis tracker, though these figures will vary depending on the latitude and topography.
The best locations for solar parks in terms of land use are held to be brown field sites, or where there is no other valuable land use. Even in cultivated areas, a significant proportion of the site of a solar farm can also be devoted to other productive uses, such as crop growing or biodiversity. The change in albedo affects local temperature. One study claims a temperature rise due to the heat island effect, and another study claims that surroundings in arid ecosystems become cooler.

Agrivoltaics

is using the same area of land for both solar photovoltaic power and agriculture. A recent study found that the value of solar generated electricity coupled to shade-tolerant crop production created an over 30% increase in economic value from farms deploying agrivoltaic systems instead of conventional agriculture. A 2023 study published in Sustainability highlighted Canada's significant potential for agrivoltaics, a dual-use land strategy that integrates solar energy production with agriculture. According to the study, installing agrivoltaic systems on just 1% of Canada's agricultural land could generate between 25% and 33% of the country's electricity needs, depending on the photovoltaic technology used. The authors emphasize that agrivoltaics presents a promising approach to help Canada meet its climate targets while preserving farmland and supporting rural economies. Policy incentives, technical research, and pilot projects are recommended to scale implementation across provinces.

Solar landfill

A Solar landfill is a repurposed used landfill that is converted to a solar array solar farm.

Co-location

In some cases, several different solar power stations with separate owners and contractors are developed on adjacent sites. This can offer the advantage of the projects sharing the cost and risks of project infrastructure such as grid connections and planning approval. Solar farms can also be co-located with wind farms.
Sometimes 'solar park' is used to describe a set of individual solar power stations, which share sites or infrastructure, and 'cluster' is used where several plants are located nearby without any shared resources. Some examples of solar parks are the Charanka Solar Park, where there are 17 different generation projects; Neuhardenberg, with eleven plants, and the Golmud solar park with total reported capacity over 500MW. An extreme example would be calling all of the solar farms in the Gujarat state of India a single solar park, the Gujarat Solar Park.
To avoid land use altogether, in 2022, a 5 MW floating solar park was installed in the Alqueva Dam reservoir, Portugal, enabling solar power and hydroelectric energy to be combined. Separately, a German engineering firm committed to integrating an offshore floating solar farm with an offshore wind farm to use ocean space more efficiently. The projects involve "hybridization", in which different renewable energy technologies are combined in one site.

Solar farms in space

The first successful test in January 2024 of a solar farm in space—collecting solar power from a photovoltaic cell and beaming energy down to Earth—constituted an early feasibility demonstration completed. Such setups are not limited by cloud cover or the Sun's cycle.

Technology

Most solar parks are ground mounted PV systems, also known as free-field solar power plants. They can either be fixed tilt or use a single axis or dual axis solar tracker. While tracking improves the overall performance, it also increases the system's installation and maintenance cost. A solar inverter converts the array's power output from DC to AC, and connection to the utility grid is made through a high voltage, three phase step up transformer of typically 10 kV and above.

Solar array arrangements

The solar arrays are the subsystems which convert incoming light into electrical energy. They comprise a multitude of solar panels, mounted on support structures and interconnected to deliver a power output to electronic power conditioning subsystems. The majority are free-field systems using ground-mounted structures, usually of one of the following types:

Fixed arrays

Many projects use mounting structures where the solar panels are mounted at a fixed inclination calculated to provide the optimum annual output profile. The panels are normally oriented towards the Equator, at a tilt angle slightly less than the latitude of the site. In some cases, depending on local climatic, topographical or electricity pricing regimes, different tilt angles can be used, or the arrays might be offset from the normal east–west axis to favour morning or evening output.
A variant on this design is the use of arrays, whose tilt angle can be adjusted twice or four times annually to optimise seasonal output. They also require more land area to reduce internal shading at the steeper winter tilt angle. Because the increased output is typically only a few percent, it seldom justifies the increased cost and complexity of this design.

Dual axis trackers

To maximise the intensity of incoming direct radiation, solar panels should be orientated normal to the sun's rays. To achieve this, arrays can be designed using two-axis trackers, capable of tracking the sun in its daily movement across the sky, and as its elevation changes throughout the year.
These arrays need to be spaced out to reduce inter-shading as the sun moves and the array orientations change, so need more land area. They also require more complex mechanisms to maintain the array surface at the required angle. The increased output can be of the order of 30% in locations with high levels of direct radiation, but the increase is lower in temperate climates or those with more significant diffuse radiation, due to overcast conditions. So dual axis trackers are most commonly used in subtropical regions, and were first deployed at utility scale at the Lugo plant.

Single axis trackers

A third approach achieves some of the output benefits of tracking, with a lesser penalty in terms of land area, capital and operating cost. This involves tracking the sun in one dimension – in its daily journey across the sky – but not adjusting for the seasons. The angle of the axis is normally horizontal, though some, such as the solar park at Nellis Air Force Base, which has a 20° tilt, incline the axis towards the equator in a north–south orientation – effectively a hybrid between tracking and fixed tilt.
Single axis tracking systems are aligned along axes roughly north–south. Some use linkages between rows so that the same actuator can adjust the angle of several rows at once.