olar power has made an impressive leap over several decades from being economically viable only for space applications to becoming the cheapest electricity source in history. According to the International Energy Agency, building new utility-scale solar projects supported by effective government policies is now cheaper than building coal-fired power plants. This undoubtedly marks a seismic shift in the global energy industry and promises the accelerating transition from fossil fuels to green power.
Even though solar power is gaining popularity among residential users, large-scale solar power plants are still the main driver of the industry: they provide more than 60% of all annual PV capacity additions globally and apparently are going to grow in number. The total generation capacity of operating utility-scale solar power plants exceeds 37,000 megawatts in the US alone, with another 112,000 MW on their way.
Types of solar power plants
The two main technologies utilized by large-scale solar plants are photovoltaics (PV) and concentrated solar power (CSP). Concentrated solar power plants use mirrors to concentrate sunlight onto a specific point, where it is converted into heat. Photovoltaics, on the other hand, directly transforms sunlight into electricity using the photovoltaic effect - a process that creates an electric current in a PV cell when it is exposed to sunlight.
A few decades ago, concentrated solar power used to be much more popular, because CSP power plants were cheaper and easier to build, while PV projects relied on expensive solar panels. But with the development of solar PV technology, PV power stations proved to be as good if not better than CSP plants, since they could work under lower irradiance and were not as demanding in terms of location (e.g. didn’t require access to water). Besides, they promised great potential given that PV technology was developing at a rapid pace and becoming cheaper. Today global concentrated solar power installed capacity is about 6.5 gigawatts (GW), while solar PV capacities have already reached the mark of one terawatt. Now let us look at a PV plant in a little more detail.
Dominant technologies for large-scale PV
A solar project is typically considered large-scale if it has a power generation capacity of at least 10 megawatts. The two commercially available PV technologies utilized by large solar projects are crystalline and thin-film.
Solar PV based on crystalline silicon has dominated the global solar market since the mid-20th century. Silicon makes up almost 28% of the Earth's crust which makes it the second most abundant element on the planet. It serves as an excellent semiconductor material for solar due to its low cost and high efficiency.
Crystalline solar is the most commonly used technology for PV power plants to this day. Crystalline solar cells are made from wafers – thin sheets cut from silicon ingots. These wafers can be mono- or polycrystalline: monocrystalline cells are manufactured from a single silicon crystal, while polycrystalline are made from several silicon fragments melted together. Both technologies are widely used in photovoltaic plants, but monocrystalline cells are preferred as they are slightly more efficient.
Thin-film solar is a second generation technology that holds great promise for large-scale applications. Thin-film panels are produced by depositing a thin layer of photovoltaic material onto a glass or plastic substrate. This layer can be up to 350 times thinner than conventional crystalline cells, which makes thin-film modules lightweight and flexible. They aren’t normally suitable for residential use as they require a much larger area than traditional panels, but their low cost and easy installation process make them a viable choice for a large solar power park.
Components of a PV power facility
A solar photovoltaic plant generally needs the same basic components as a residential PV project: solar PV modules, inverters, switchers, junction boxes, and cabling, However, mass-scale energy generation requires quite a lot of additional equipment. For example, utility-scale solar plants include step-up transformers used to increase the voltage of the generated energy to make it suitable for the power grid, as well as medium voltage switchgear that provides centralized control and protection of power generation equipment. PV plants are also fitted with SCADA (Supervisory Control & Data Acquisition) systems - software for monitoring and controlling power generation processes.
The biggest solar farms in the world
Tengger Desert Solar Park
Chinese Tengger Desert Solar Park located in Zhongwei, Ningxia, ranks fifth on the list. The photovoltaic power station spans 10,625 acres and occupies 3.2% of the Tengger desert. Built in 2015, it was at that time the largest solar plant in the world – it even got a nickname the 'Great Wall of Solar'. The PV station provides China with 1.55 GW of solar capacity and powers more than 600,000 homes.
Benban Solar Power Project
Located in the Aswan governorate, Egypt, Benban Solar power Park stretches over an area of 9,142 acres and consists of 41 solar power projects each developed by a different company. The total capacity of the plant reaches 1.8 GW and its annual electricity output averages at 3.8 TWh.
Pavagada Solar Park
Pavagada Solar Park covers an area of 13,096 acres in Karnataka state in India, to the northeast of the city of Pavagada. Launched in 2018 and fully completed in 2019, the photovoltaic park boasts a generation capacity of approximately 2.05 GW.
Huanghe Hydropower Hainan Solar Park
The third place goes to a 2.2-GW capacity plant in Qinghai province in Northwest China. Huanghe Hydropower Hainan Solar Park got commissioned in 2020 and is backed by 202.8 MW/MWh of storage capacity. It is connected to an ultra-high voltage (UHV) power transmission line designed to connect China's far northwestern parts to the more densely populated eastern regions.
Bhadla Solar Power Plant
Bhadla Solar Power Plant located in Rajasthan, India, is the world's largest solar park. The sprawling 14,085-acre solar station has a total generation capacity of 2.25GW, which is enough to power over 1.3 million homes. The plant comprises 10 million PV panels and has solar power storage with a capacity of 202.8 MW/MWh.
The future of large-scale solar PV
Solar costs have fallen 82% in just a decade which served as a key driving force in large-scale PV deployment. And everything suggests that this price reduction isn’t going to stop any time soon. Solar energy is only going to strengthen its position as a price leader and one of the most viable alternatives to fossil fuels on the global energy market.
According to experts, utility-scale PV plants will account for up to 50% of global solar capacity by 2030, thus remaining a key pillar of the industry. As BloombergNEF (BNEF) research shows, the levelized cost of electricity (LCOE) generated by utility-scale solar could fall by 55% globally by 2030. This is largely due to new technologies that would make PV plants more cost- and space-efficient. One of them is improvements in battery storage - thanks to them global solar storage capacity is expected to shoot up from 11 GW in 2020 to 168 GW in 2030. Storage is a great way to maximize the value of a PV park and ensure the energy can be delivered whenever it is needed.
Further development of crystalline silicon modules is another trend to watch. And the main focus is on the passivated emitter and rear cell (PERC) technology, where PV cells are given an extra layer on the back allowing them to capture more sunlight. PERC-based modules promise higher energy conversion and can boost the efficiency of large solar projects.
Another technology that is already being increasingly employed in large-scale PV is bifacial panels collecting sunlight on both sides of a PV module. The cells on the back side of a panel are capable of capturing indirect sunlight diffused in the atmosphere and reflected off the ground, which leads to a solid increase in power output. Analysts estimate that today bifacial panels already account for 30-50% of all U.S. solar power projects.
Floating PV installations are one more promising direction. This emerging technology works by placing a PV plant on top of a body of water and offers a great alternative to conventional on-land and rooftop projects. In particular, they could potentially solve the problem of unsustainable use of land and water resources.