Commercial energy production using solar concentrators is becoming an energy priority for countries with high levels of solar insolation, including Spain, Morocco, UAE, USA, Mexico and others. Solar thermal power plants (STPP) energy is gaining worldwide recognition as one of the leading innovative technologies aimed at transitioning from fossil fuels to clean renewable sources of electricity and heat.

Solar thermal power plants (STPP) construction remains a balancing technique for socio-economic developments and environmental stability.

Thanks to government assistance in the form of high tariffs for electricity generated and tax deductions, STPPs have become profitable systems that guarantee an acceptable level of profitability for investors.

CP Finance UK offers comprehensive services in the field of financing, construction and modernization of STPPS, providing customized technical solutions to companies in many countries.

Our team, together with partners from Spain and other European countries, is also ready to offer you financing and construction of solar projects on favorable terms.

Types of solar thermal power plants

Photovoltaic and solar thermal technology are two main ways to use solar energy for commercial purposes.

The rest of the technologies, which may have a promising future, are still considered largely experimental. About ten solar thermal technologies have gone beyond research and have already become the basis for large STPPs with an installed capacity of up to several hundred megawatts.

A modern solar thermal power plants (STPP) are classified below:

• Hybrid STPPs combined with a gas boiler for fossil fuels.
• Hybrid STPPs combined with a solid fuel boiler for biomass.
• Hybrid STPPs using a combined cycle.
• Solar concentrators with parabolic trough and heat storage technology using inorganic salts.
• Solar thermal power plants with linear Fresnel concentrators.
• Tower solar concentrators with direct steam generation.
• Solar concentrators with parabolic troughs.

A technology based on concentrating solar energy along a pipe with a heat-conducting fluid using long parabolic troughs has been actively studied in the United States since the 1980s.

Based on this principle, the giant SEGS (Solar Energy Generating System) was built in the Mojave Desert, California.

As a result of years of operation of SEGS, researchers have accumulated tens of thousands of hours of experience to bring parabolic concentrator technology to its current state. No other technology has been studied so well. This is one of the reasons why most investors choose to build a STPP of this type, despite the well-known disadvantages and dangers (for example, the use of HTF based on aromatic hydrocarbons).

The first group of installations concentrates solar thermal energy along the line, and the second directs the rays to one point, reaching a much higher local temperature.

The first group of STPPs uses parabolic trough concentrators or Fresnel mirrors. The second group of installations, which operates with high temperatures and regulates the direction of the beams along two axes at once, uses either the central tower or Stirling engines. In the most advanced installations, thermal energy can be stored in order to convert it into electricity at the right time.

There are also hybrid solar thermal power plants that simultaneously use solar energy with fossil fuels or biomass. These engineering solutions significantly expand the list of opportunities for investors.

Solar thermal power plants

Solar thermal energy with a central receiver

The central receiver (solar tower) is responsible for converting concentrated solar radiation into heat, transferring it to a coolant, which can be air, water or inorganic salts. This medium can be used directly to convert water to steam and also to increase the performance of an integrated turbine by heating the intake air before entering the combustion chamber.

If the heat transfer fluid is water, central receiving units heat and vaporize the previously introduced fluid to produce steam at a specified pressure and temperature. This steam is then expanded in a steam turbine, following the general principles of any thermal power plant.

When the power plant is operating normally, inorganic salts are stored at around 290ºC in a large insulated tank.

A vertical centrifugal pump moves the salts from the reservoir to a receiver located at the top of the tower.

The heat transfer fluid, driven by the pumps, moves from the salt reservoir to a receiver at the top of the tower, where the temperature rises to about 560–600ºC.

The liquid is stored there until it is used to generate steam.

This technology allows CSPs to provide a relatively stable generation of electricity throughout the day, regardless of the intensity of sunlight.

Among others, the advantage of solar thermal power plants offer over other solar technologies are the following:

• The use of the same heat carrier for energy generation and storage, which simplifies the system and improves the economic performance of the facility.

• High temperature of the heating medium compared to alternative technologies, which contributes to an increase in the efficiency of the steam-water cycle.

• Heat transfer fluid (molten salts) circulates through a well-defined area with higher efficiency compared to parabolic systems.

• HTF pipelines can be drained by gravity when the unit is not running, without the need to install additional pumping equipment.

A prime example of a central tower CSP is the Noor Ouarzazate CSP power plant, which has been under construction in Morocco since 2013. It is considered the largest power plant of this type on the planet, which was designed for the extreme conditions of the desert.

Solar thermal power plants for energy storage

One of the major problems of renewable energy, which uses methods that are highly dependent on weather conditions, is the difficulty of generating energy during periods of peak consumption.

Generation is carried out under favorable natural conditions, but not at the peak of consumption.

Once electrical energy enters the grid, it must be consumed immediately. Since electricity is extremely expensive to store, production and consumption should ideally coincide in time.

This problem could be solved by generating electricity under favorable conditions and consuming it when needed. This means building a “storage” of energy in one form or another.

Since the storage of electrical energy on a large scale presents a number of problems that science has not yet solved, other types of energy storage have traditionally been used, for example, pressure or temperature differences.

So, pumped storage power plants are based on storing dammed water in order to drain reservoirs and use water at the right time.

Hybrid solar-fossil fuel power generation

Today it is extremely difficult to make reliable weather forecasts and predict the generation of electricity from a solar thermal power plant.

Since the beginning of construction of the first SEGS power plants in California, the possibility of adding an auxiliary fossil fuel boiler to the solar system has been investigated.

It is difficult to store electrical energy, so energy production and consumption must coincide in time. Otherwise, there will be certain imbalances in the power grid, which can lead to power outages for enterprises and entire regions.

While some experts believe that solar thermal power plants must have a heat storage system, in practice it is too expensive for a business.

The possibility of integrating an auxiliary boiler that runs on natural gas or biomass is provided for in the current standards in Spain and several other countries. That is, it is assumed that the STPP should be independent of natural conditions. Moreover, the boilers provide the necessary heat to prevent freezing of the heat transfer fluid, which is about + 12ºC.

Hybrid power plants capable of mixing steam generated from solar collectors and from a gas turbine waste heat boiler are called ISCC (Integrated Solar Combined Cycle) power plants.

Fossil fuels have many disadvantages, but ISCC has two obvious benefits. This is a low cost of electricity generation and smooth power regulation to match the current load.

Our services include financing and lending for solar thermal power projects.

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