How Do Solar Turbines Generate Electricity?
Solar turbines are devices that use solar energy to generate electricity. They work by converting sunlight into heat or electricity through concentrating solar power or photovoltaic cells. Solar turbines offer a clean, renewable way to produce electricity with zero emissions.
There are two main types of solar turbines: concentrating solar thermal systems that use mirrors or lenses to concentrate sunlight to drive a heat engine, and photovoltaic systems that convert sunlight directly into electricity through solar cells. Hybrid systems that combine both solar thermal and PV technology are also used.
Solar turbines provide many benefits when used for electricity generation. They produce no greenhouse gas emissions during operation, reducing environmental impact. Solar electricity can offset the need for fossil fuels, improving energy security and independence. Solar power is renewable and sustainable, and turbine systems require little maintenance once installed. Solar turbines can be installed in distributed, small-scale systems to provide electricity in remote areas. Overall, solar turbines provide a versatile, eco-friendly option for electricity generation with minimal environmental footprint.
Sources:
https://forevergreen-energy.co.uk/the-increasing-benefits-of-going-solar-in-2021/
How Solar Energy is Captured
Solar energy is most commonly captured using solar panels and photovoltaic cells. Solar panels contain photovoltaic cells made from materials like silicon that convert sunlight directly into electricity through the photovoltaic effect. When sunlight hits these cells, the energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity.
In order to maximize the amount of sunlight that hits the solar panels, trackers and solar concentrators are often used. Trackers tilt and rotate the panels to follow the sun’s path across the sky, ensuring the panels directly face the sun all day long. Solar concentrators use mirrors or lenses to focus sunlight onto smaller, highly efficient photovoltaic cells, concentrating the sunlight to multiply its power.
Solar heat concentrators can focus sunlight into a single point, heating that spot to very high temperatures. This heat can then be used to drive a Stirling engine or a steam turbine to generate electricity. Parabolic-shaped mirrors are often used for solar concentrators, rotating slowly to keep the focal point directly on the sun.
Generating Electricity from Heat
Solar thermal power plants use concentrated sunlight to heat a fluid, usually a synthetic oil, to very high temperatures. This heated fluid is then used to boil water and create steam that spins a turbine connected to an electrical generator, which converts the rotational mechanical energy into electricity.
There are different technologies used to concentrate the sun’s rays and heat the fluid, with parabolic troughs and solar power towers being most common. Parabolic trough systems use long rectangular mirrors curved into a U-shape to focus sunlight onto a pipe running along the focal point, heating the oil inside it to temperatures up to 400°C. Power tower systems use many flat mirrors called heliostats to direct sunlight to a central receiver at the top of a tower, which heats the fluid in the receiver to over 1000°C.
In both designs, the hot fluid from the solar collectors is pumped through a heat exchanger where it vaporizes water to produce steam. This high-pressure steam then spins the turbine and creates mechanical power that gets converted into electricity by the generator. Solar thermal plants with thermal storage can use excess heat to boil water that is then stored at high pressure in insulated tanks. The stored hot water can generate steam on demand when solar radiation is low.
Compared to photovoltaics, the advantage of solar thermal electricity generation is that it is not limited by thermodynamic efficiency as it uses heat engines. Solar thermal plants convert about 30-40% of the solar radiation into electricity, while PV modules have an efficiency of 15-20%.
Sources:
https://upcommons.upc.edu/bitstream/handle/2099.1/15636/TFG.pdf
Stirling Engine Solar Turbines
Stirling engines are heat engines that use an external heat source to generate motion and electricity. Solar Stirling engines convert concentrated sunlight into electricity using a Stirling engine and generator.
Stirling engines work by having one piston in a hot chamber and another in a cold chamber. The concentrated sunlight from reflectors or lenses heats up the gas in the hot piston, causing it to expand. The expansion pushes the hot piston, which is connected via linkages to the cold piston. The cold piston gets pushed and compresses the gas inside. The compression then pushes the hot piston back. This back-and-forth motion by the expanding and contracting gas drives the pistons in a repeating cycle. 1
The linear motion of the pistons gets converted into rotational motion using linkages and a crankshaft. The crankshaft spins a generator to produce electricity. This makes Stirling engines useful for converting heat differences into electrical energy. The greater the temperature difference between the hot and cold chambers, the more electricity can be generated.
Photovoltaic Solar Turbines
Photovoltaic solar turbines use solar cells, also known as photovoltaic cells, to directly convert sunlight into electricity. Solar cells are made of semiconductor materials like silicon that absorb photons from sunlight and release electrons, generating an electric current. This electric current generated from the solar cells is direct current (DC).
In order to connect the solar turbine system to the utility grid and power homes and businesses, the DC must be converted into alternating current (AC) using an inverter. The inverter takes the DC electricity from the solar cells and converts it into AC electricity that matches the type of electricity delivered over the utility grid. This allows the solar electricity to seamlessly integrate with the grid when connected.
Once converted into AC power, the electricity generated from the photovoltaic solar turbine can be used to power a home or business directly, fed into the utility grid to offset electricity usage, or both. Being grid-connected allows any excess solar electricity generated to flow back into the grid, spinning the household electric meter backwards. This allows consumers to get credit for the excess electricity they generate. The grid also acts as backup power source when solar production is low.
Some key references on photovoltaic solar turbine components:
https://www.fuelcellstore.com/blog-section/components-of-a-photovoltaic-system
https://www.alternative-energy-tutorials.com/solar-power/7-components-of-your-solar-power-system.html
Hybrid Solar Turbines
Hybrid solar turbines combine multiple solar energy technologies into one system to improve overall efficiency. The most common type of hybrid solar turbine uses a combination of solar thermal collectors and photovoltaic (PV) panels (Solar Technologies, 2022). Solar thermal collectors concentrate sunlight to heat a fluid, which creates steam to power a turbine generator. PV panels convert sunlight directly into electricity. Combining these methods allows the system to generate electricity from both the heat and light energy from the sun.
Hybrid systems have higher efficiency than either solar thermal or PV alone. The thermal component can continue producing energy even when the sun isn’t shining brightly enough for optimal PV output. And the PV panels provide extra electricity generation capacity to supplement the steam turbine. Hybrid solar plants also utilize solar trackers to optimize energy capture throughout the day (Reginald, 2017). The combined solar technologies work together to maximize energy production.
Solar Trackers
Solar trackers are structures that move solar panels to follow the sun’s path across the sky, helping the panels absorb more sunlight. Solar trackers aim to maximize solar energy capture by keeping panels perpendicular to the sun’s rays throughout the day (source).
There are two main types of solar trackers:
- Single-axis trackers: These move panels along one axis, typically left-right. They follow the sun’s east-west movement each day. Single-axis trackers increase energy production by around 25% compared to fixed panels.
- Dual-axis trackers: These move panels along two axes, allowing them to directly face the sun all day. Dual-axis trackers can boost energy production by around 35% versus fixed panels. However, they are more complex and expensive (source).
Solar trackers use motors and gearboxes to move the panels. Control systems with sensors and microprocessors tell the motors how much to move the panels based on the sun’s position. Precise tracking maximizes energy capture.
While solar trackers increase efficiency, they also add cost and complexity. Their moving parts need regular maintenance. Trackers take up more space than fixed tilt systems. Overall, trackers provide the greatest boost for utility-scale solar farms, where the extra energy production justifies the higher price tag.
Solar Turbine Maintenance
Proper maintenance is crucial for solar turbines to operate efficiently and maximize power output. Key maintenance activities include:
Cleaning Solar Panels
Solar panels need to be kept clean and free of debris, dust, dirt, and bird droppings to maintain peak performance. Panels are typically cleaned 1-4 times per year using soft brushes, squeegees, or low-pressure water. Cleaning frequency depends on environmental factors like wind, rain, and pollution levels (Solar Turbines).
Inspecting Components
Technicians inspect key components like turbines, generators, gearboxes, batteries, wiring, and controllers for damage, wear, and proper operation. Issues are repaired or replaced as needed. Inspections may occur daily, monthly, quarterly, or annually (Kurz).
Performance Monitoring
Remote monitoring systems track power output, equipment faults, weather data, and other metrics. Performance is analyzed to schedule maintenance and detect problems early. Cleaning schedules can be optimized based on output drops instead of fixed calendars (Kurz).
With routine care and maintenance, solar turbines can operate reliably for decades.
Challenges of Solar Turbines
Solar turbines face some key challenges that need to be addressed for the technology to reach its full potential. Some of the main challenges include:
The intermittency of sunlight. Solar turbines rely on constant sunlight to operate effectively. However, the availability of sunlight varies due to nighttime, cloud cover, and seasonal changes. This inconsistency can make solar turbines an unreliable energy source at times.[1]
Large land area required. Building utility-scale solar farms requires significant amounts of land, which isn’t always available near demand centers. Solar turbines work best in areas with consistent sunlight and minimal cloud cover.
High upfront costs. While solar power is inexpensive to operate, the initial investment for turbines and solar farms is still cost prohibitive for many applications. The costs for infrastructure, equipment, and installation are steep.
Ongoing research and development aims to tackle these solar turbine challenges through improved energy storage solutions, more efficient materials, and hybrid turbine systems. However, these factors continue to limit the scalability of solar turbines currently.
[1] https://www.justsolar.com/blog/solar-turbines
Future of Solar Turbine Technology
The future looks bright for continuing advancements in solar turbine technology. Here are some key areas of focus:
Efficiency improvements – Researchers are finding new ways to convert more of the sun’s energy into usable electricity. This includes developing better solar cell materials, improved mechanical designs, and innovations like multi-junction solar cells. The goal is to increase efficiency to reduce the overall cost per watt of solar power. Solar Turbines is continuously innovating to build more efficient gas turbine systems.
Lower costs – As solar technology matures, costs continue to come down. Economies of scale, reduced material costs, and streamlined manufacturing processes are making solar more affordable. Solar module prices have dropped 90% since 2009. Continued R&D and manufacturing improvements will further drive down costs over time.
Increased capacity and storage – Larger and more powerful solar installations are being built, including utility-scale solar farms. At the same time, energy storage solutions are improving thanks to better batteries, compressed air, hydrogen fuel cells and more. This enables solar power to be dispatched whenever needed, even at night or when the sun isn’t shining.
Overall, the future is bright for solar turbine technology to become more efficient, more affordable and have greater capacity to supply the world’s electricity needs in a sustainable way.
