Solar Energy Moves Forward With CSP Plants

There are predominantly two types of solar power generation methods used to generate electricity on a commercial scale. Photovoltaic panels uses the sunlight to directly produce electricity by using solar cells set in photovoltaic modules. Concentrating solar power (CSP) uses thermal solar power, the heat of the sun, to produce environmentally friendly energy.

We will take a look at the way in which concentrating solar power plants create electricity. CSP plants are capable of producing electricity at a higher maximum capacity than a photovoltaic facility of the same size. They will play an increasingly important role in the move away from fossil-fuel sourced energy to that of renewable energy.

There are four main types of concentrating solar power systems: parabolic troughs, dish / engine systems, fresnel reflectors and central receiver systems. The technology involved with each is proven and either has been or still is in operation around the world with more solar thermal power in progress to increase global capacity.

Parabolic troughs use mirrors to direct sunlight onto a fluid-filled receiver positioned in directly in front of each trough. The heat generated from this process heats the fluid to high levels so that super-charged steam is created. Electricity is then created by means of a conventional steam generator.

A trough-based CSP plant typically consists of rows of mirrored troughs placed parallel to each other along a north-south axis in what is known as a collector field. The troughs pivot as they follow the sun to ensure that it is continuously focused on the receiver tubes. Electricity continues to get generated when the it’s cloudy or after the sun has set thanks to thermal storage. Technological advancements are continuing to prolong this production period in a bid to move to continuous solar electricity production.

Power plants known as Andasol 1, Andasol 2 and Andasol 3 in Spain all use the parabolic trough design, forming a combined 150MW solar power plant. The surface area of the mirrors used to form the energy collection field of Andasol 3 alone is around 500,000m2.

Dish / engine systems are stand-alone units that contain dish-shaped parabolic mirrors that concentrate the sun’s energy onto a receiver mounted above the dish. From there the energy is converted into mechanical power and electricity is generated similar to the way a mechanical engine runs. Each dish / engine unit has a capacity of around 25kW of solar power and it tracks the sun to ensure optimum power.

An example of the dish / engine technology is the Stirling Energy Systems dish called the Suncatcher that will be used in fields of thousands to form a power facility capable of generating over 500MW of electricity

Fresnel reflectors provide a more concentrated focus of solar energy onto centrally placed receivers. Costs are reduced using this method because the rows are positioned more closely together, there are fewer moving parts and less receivers are required. The receiver is stationary and it is shared by multiple mirrors.

An example of a recently commissioned CSP plant using reflector technology is the Kimberlina CSP plant in California developed by Ausra. This power plant is relatively small at only 5MW capacity, but it paves the way for future large-scale developments.

Central receiver systems, known colloquially as power towers, is another way to produce concentrated solar power. Looking as though they’re honoring a higher deity, thousands of mirrors called heliostats cluster around a receiver that sits on top of a tall tower. Molten salt is heated as it passes through the receiver and this then makes steam which operates a conventional steam generator. The molten salt can be stored for great lengths of time which means that this type of solar energy generates electricity continuously around the clock.

An example of a central receiver system in development is the Solar Tres power plant being built in Spain. The Solar Tres power plant will be a 15MW facility and it follows on from the successful demonstration power plant known as Solar Two which was located in the Mojave Desert.

As technological advancements continue to be made, the critical factor of the cost to produce each watt is gradually being addressed. Already, concentrating solar power plants hold a huge advantage over the traditional fossil fuelled counterparts in the lower impact to the environment. In fact, one of the only impacts that concentrating solar power plants have on the environment is land use.

There continues to be solid progress made in ways in which renewable energy is used to replace traditional energy sources. Concentrating solar power has proven to be a renewable energy source with still more untapped potential

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