How Much Does It Cost To Build A Solar Thermal Power Plant?

Solar thermal power plants generate electricity by concentrating sunlight to heat a fluid and produce steam that spins a turbine connected to a generator. Unlike solar photovoltaic systems that convert sunlight directly into electricity, solar thermal uses the heat from the sun’s rays. The goal of this article is to provide an estimate of what it costs to construct a solar thermal power plant. We will look at the major components and installation costs that factor into the total price.

Table of Contents

Power Plant Components

There are several major components that make up a typical solar thermal power plant:

Mirrors/Reflectors – Large mirrors, usually arranged in long rows and mounted on trackers to follow the sun, reflect and concentrate sunlight onto a receiver.

Receiver – The receiver absorbs the concentrated sunlight, converting it to heat. This is usually a panel or tube with a liquid or gas flowing through it.

Thermal Storage – Molten salt or other fluids store the heat from the receiver, allowing power generation to continue after sunset.

Steam Turbine – The heat from the receiver generates steam to spin the turbine and generate electricity through a generator.

Balance of System – Additional equipment like pumps, piping, controls and power electronics are needed to support the main components.

Land Acquisition

Solar thermal power plants require a large amount of land area to operate efficiently. This is because the solar collectors, which consist of many mirrors or other reflectors, need adequate space to focus sunlight onto the central receiver. The actual land area required can vary substantially depending on the size of the plant and solar technology used, but is typically on the order of 2-10 acres per megawatt of capacity. For a large 50-100 MW solar thermal plant, hundreds or even thousands of acres may be needed.

Acquiring this much land suitable for a solar power plant can be one of the most significant capital costs in building this type of renewable energy facility. The cost per acre of land depends greatly on the location, but desert and rural areas suitable for solar projects often range from $500 to several thousand dollars per acre. At $2,000/acre for example, a 100 MW solar thermal plant needing 2,000 acres would incur a land cost of $4 million just for acquisition. This does not include any costs for grading, access roads, fencing, or other preparations.

With such large areas needed, solar thermal developers typically try to locate projects on relatively inexpensive open land. However, competition for sites near transmission lines and roads can drive costs higher in some regions. Since land acquisition represents such a major upfront investment, it’s a key consideration when planning and budgeting for these renewable energy facilities.

Mirrors/Reflectors

The most expensive component of a solar thermal power plant is the field of mirrors or reflectors that concentrate sunlight onto a receiver to heat a working fluid. There are three main types of concentrating solar power technologies that use mirrors:

Parabolic troughs – Long, U-shaped mirrors that concentrate sunlight along a focal line. The mirrored surface area is around 80 square meters.

Power towers – An array of flat, movable mirrors (heliostats) that concentrate sunlight on a receiver mounted on top of a tower. Each heliostat is around 10-15 square meters.
Dish/engines – A parabolic dish-shaped reflector that concentrates sunlight onto a receiver at the focal point. Each dish is around 10-25 square meters.

The estimated cost per square meter of mirrors or reflectors is $75-$250 for parabolic troughs, $150-$250 for power towers, and $250-$400 for dish/engines. The total mirror/reflector costs range from 15-25% of the overall plant cost.

Receiver

The receiver is one of the core components of a solar thermal power plant. This is the part of the system where the concentrated sunlight is converted to heat. The receiver contains tubes or channels that carry a heat transfer fluid. As sunlight is focused on the receiver, it heats up the fluid inside to very high temperatures, often over 400°C.

Common heat transfer fluids used in solar thermal receivers include oils, molten salts, pressurized water or steam, sodium, and air. Using oils or molten salts allows the heat to be efficiently stored for later electricity production. Molten salts are particularly advantageous as they can be heated to over 550°C before turning to steam. Pressurized water/steam is used when there is no thermal storage system.

Building the receiver and filling it with heat transfer fluid is one of the major capital costs of a solar thermal plant. For large-scale commercial plants, the receiver system can cost $100-$300 million or more. The materials must withstand high temperatures over many years of operation. Stainless steels and specialized alloys are often used. The receiver design must also minimize heat losses through insulation and optimize heat transfer efficiency.

Thermal Storage

Thermal energy storage is an important component of any solar thermal power plant. Since sunlight is not available 24 hours a day, thermal storage allows the plant to continue generating electricity even when the sun is not shining.

Molten salt is commonly used for thermal storage in solar thermal plants. Molten salt has a very high heat capacity and can be heated to over 500°C without breaking down. The hot molten salt is stored in large insulated tanks during the day. Then, during times when solar energy is not available, the hot molten salt is used to produce steam to run the turbines.

The larger the thermal storage capacity, the longer the plant can operate at full power without any solar input. However, larger storage capacity also increases costs. Most solar thermal plants have enough storage to continue operating at full power for 6-8 hours after sunset.

The molten salt storage system adds significant cost to a solar thermal plant. Storage costs are estimated to be around $50 per kWh of capacity. For a 100 MW plant with 15 hours of storage, the storage system would cost around $75 million.

Steam Turbine

The steam turbine is a critical component of any thermal solar power plant. This device converts the steam’s thermal energy into rotational mechanical energy to drive an electrical generator. For large-scale solar thermal plants, the steam turbine size typically ranges from 50-150 megawatts (MW).

Steam turbines represent one of the largest capital expenses in building a solar thermal plant. The cost scales with the size of the turbine and can range from $500-$800 per kW of capacity. So a 100 MW steam turbine would cost $50-80 million. This accounts for the turbine itself plus any associated valves, controls, and other balance-of-plant costs.

There are opportunities to reduce the turbine capital cost through economies of scale and technology improvements. But the steam turbine remains one of the biggest line items in a solar thermal plant’s overall budget. Careful sizing and selection of the turbine is important to balance performance and costs.

Balance Of System

Aside from the major equipment in a solar thermal power plant, there are several other significant costs within the balance of system. This includes buildings to house the turbine generators and provide office space, control systems to operate the plant equipment, power transmission equipment to deliver electricity to the grid, roads and civil works within the plant, and more. These balance of system costs can add up to around 20-25% of the total plant cost. Here are some of the main balance of system costs:

– Plant buildings and structures – housing for turbine generators, maintenance shops, control rooms, warehouses, and administration offices.

– Electrical systems – transformers, switchgears, wiring, grounding, lighting, emergency power systems.

– Control systems – hardware and software for monitoring and controlling equipment, safety systems.

– Cooling equipment – heat exchangers, cooling towers, condensers.

– Water treatment systems – filtration, chemical treatment, recycling.

– Roads, fencing, drainage, landscaping, parking.

While not as expensive as the solar field and power block, the balance of system costs add significantly to the total price tag of a solar thermal power plant. Careful design and planning is needed to optimize these costs as much as possible.

Installation

Installing a solar thermal power plant is a major construction project that requires significant labor, equipment, and management. Hundreds of workers are needed to prepare the site, install components, and integrate all the systems.

Site preparation involves clearing and leveling land, digging trenches for pipelines and cables, building access roads, and constructing the power block area where the turbine and other equipment will be housed. Foundations must be poured for the solar field, turbine generator, buildings, and other structures.

The solar field is the most labor-intensive part of the plant to construct. Teams of workers must install thousands of mirrors mounted on trackers with supporting pylons dug deep into the ground. The mirrors are wired together and connected to the control system. The tower and receiver are assembled on site piece by piece.

Piping crews run miles of piping throughout the plant to connect all the systems. Electricians wire up the equipment and instruments. Control systems are tested and debugged. At peak construction, hundreds of workers may be on site operating cranes, forklifts, trucks, and other heavy equipment.

The construction management team oversees the entire project, coordinates contractors and suppliers, manages the schedule and budget, and ensures quality workmanship. A solar thermal plant typically takes 2-3 years to build from groundbreaking to commissioning. The total labor, construction, and management costs can amount to 20-30% of the overall project cost.

Total Cost Summary

In total, building a new solar thermal power plant can cost $3.5-5 billion for a 100 MW plant. This includes land acquisition, mirrors, receivers, thermal storage, turbines, installation, and other balance of system costs. While the upfront capital costs are higher than building a similarly sized coal or natural gas power plant, solar thermal plants have minimal fuel costs once constructed.

Coal-fired power plants can cost $1-3 billion for every 1,000 MW generated. Natural gas power plants cost slightly less at around $700 million – $1 billion per 1,000 MW. So for a 100 MW plant, coal would be $100-300 million and natural gas around $70-100 million upfront.

However, fuel and operating costs over the lifespan of a fossil fuel plant are far higher compared to solar thermal. While solar thermal plants require occasional mirror cleaning and maintenance, they utilize free sunlight as fuel. The lack of ongoing fuel costs is a major advantage of solar thermal power versus alternatives over the long run.