Plants that harness solar power: how PV solar powered plant and CSP solar plant work

olar power has evolved from a niche technology to an essential part of the energy industry, and the utility-scale solar electric plants play a leading role. In the US, large-scale solar power plants have been driving the country’s solar market growth for a decade now and account for over 60% of cumulative solar capacity. US Energy Information Administration (EIA) expects an annual utility-scale solar capacity increase of more than 20 GW in the coming years.

Large-scale solar power: the main driver of the industry

Large-scale solar power facilities are a way to reduce carbon emissions and tackle climate change. But on top of that, a large solar power generation plant can support national economies by significantly cutting the costs of electricity production. The Levelized cost of energy (LCOE) of an average solar energy plant, i.e. the price at which the energy has to be sold to break even by the end of its lifetime, stands at $0.030-$0.042 per kWh. Thus, an average solar plant far surpasses coal with its LCOE of $0.065-$0.152 per kWh and even gas with $0.045-$0.074 per kWh.

Let's take a deeper look into the large-scale solar electric market and discuss what a solar powered plant is.

Types of solar power plants & how they work

A solar plant harnesses the power of the sun to produce energy at the utility level. The major difference between a solar powered plant and a residential solar electric roof-mounted system is that the electricity generated at a solar plant is sold to corporate and utility buyers, not ultimate consumers.

A solar plant can be of two types: a photovoltaic solar electricity plant and a thermal solar energy plant.

A solar panel power plant utilizes the same technology as a residential solar electric system, namely produces electricity with the help of the photovoltaic effect. To be considered a solar energy plant, a PV project has to have at least a 10 MW power capacity. A minimum of 44,000 solar panels and 150 acres of land are required to get a PV solar power plant working.

Large-scale solar thermal power generation facilities usually have at least 50 MW capacity. They employ a less sophisticated technology than a PV solar plant concentrating sunlight to produce enough heat needed to generate electricity.

PV solar power plant working principle

The key principle of a PV solar panel plant operation is photovoltaic effect, a physical process in which solar panels produce electricity when exposed to sunlight. When photons (the smallest particles of light) hit the surface of a solar cell, the electrons inside it are moved from their positions, which creates a current.

Solar cells in the panels of a solar energy plant are mostly made of crystalline silicon due to its great semiconducting properties, low cost, and long lifespan. The cells in a solar powered plant panel can be either polycrystalline or monocrystalline. Polycrystalline solar cells for solar electric systems are made of several crystals of silicon, they are usually blue-colored with straight edges. Monocrystalline solar cells are black with rounded edges and are manufactured using a higher-quality single crystal of silicon. They work about 20% less efficiently and need less space, therefore are considered a better choice for a large solar plant.

But the electricity generated by PV panels of a solar electric system isn’t ready to be fed to the distribution grid. They produce the direct current (DC), where the charge only flows in one direction. But transmission systems require alternating current (AC) electricity, where the electrons change their direction periodically. That’s why every solar cell power plant includes an inverter – a piece of equipment that converts the DC voltage created by panels into AC. A solar inverter also serves as a monitoring tool helping to optimize the voltage of a solar energy plant and keep track of its output.

Apart from this, a PV solar electric plant includes a wide range of equipment such as weather forecast systems, sun trackers, power management systems, and supervisory control and data acquisition (SCADA) systems.

What is the world’s largest PV solar powered plant?

The largest solar electric PV plant in the world is Bhadla Solar Park in Rajasthan, India. The facility spreads across more than 5,700 hectares (14,000 acres) and has more than 10 million solar panels reaching an operational capacity of 2245 MW. The plant is estimated to generate around 732,874 MWh per year. This huge solar plant is of particular significance to the Indian energy sector, as 75% of the country’s annual power generation still comes from coal.

Second and third place went to the solar power plants located in China - Longyangxia Dam Solar Park and Huanghe Hydropower Hainan Solar Park.

How does a concentrated solar power plant work?

Large-scale thermal solar power facilities, also known as concentrated solar power (CSP) plants, use arrays of mirrors or other reflecting surfaces to focus sunlight on a plant receiver containing heat transfer fluid. When heated, this fluid converts water to steam which, in turn, spins the turbines. The mechanical energy of the rotating turbines is later transformed into electricity by a generator. The working principle of a thermal solar energy plant is similar to fossil-fuel-based production, with the difference that it heats steam with sunlight instead of fossil fuel combustion.

A utility-scale solar powered plant can be of three types: a parabolic trough solar plant, linear Fresnel reflector plant, and solar power tower plant.

Parabolic trough solar plant

A thermal solar energy plant with a parabolic trough collector (PTC) is the most widespread option for electricity generation with solar thermal power. This type of solar plant utilizes large U-shaped focusing mirrors to concentrate the sun’s rays on a single point. This technology allows PTC solar electricity plant to focus more sunlight on a receiver and convert more solar energy into electricity than any other CSP solar plant.

A solar panel plan involves assessing energy needs, site evaluation, choosing the right system size and type, obtaining permits, installation, and maintenance. It aims to maximize energy efficiency and cost savings.

Linear Fresnel system

A linear Fresnel is another type of thermal solar powered plant. It generates electric power using an array of flat thin mirrors that concentrate the solar radiation on a linear plant receiver. This thermal plant solar system offers a lower energy concentration ratio and efficiency. However, considerably less investments and land use permissions are needed to build a linear Fresnel solar electricity plant.

Solar power tower

A solar power tower is a solar powered plant that uses large, sun-tracking mirrors to focus solar energy on a receiver placed at the top of a tower. Thermal energy storage technology allows the solar power system to generate electricity in cloudy weather and even at night.

The largest CSP solar plant

The world’s biggest concentrated solar power facility is The Noor Ouarzazate Solar Complex in Morocco. It comprises four solar power plants with a total capacity of 580 MW. The gigantic thermal solar electricity plant has a total surface of mirrors of 1.4 million square meters and stretches over 2,500 hectares (6,178 acres). This solar powered plant allows the country to get approximately half of its power from renewable sources.

PV solar powered plant vs CSP plant: which one can work more efficiently?

Both photovoltaic solar plant and thermal solar plant harvest the sun’s power to produce electricity, but each has pros and cons.

A thermal solar powered plant usually turns out to be more energy efficient and needs less space. However, such a plant typically requires more maintenance and has a shorter lifespan.

A PV solar electricity plant is normally cheaper to build, lasts longer, and can be installed at a wider range of locations. But it has disadvantages as well: a PV solar powered plant generates less dispatchable energy and can work only during sunny hours.