Solar Power
Below is a quick overview of solar power today. Below the overview, I’ve also added a number of additional solar power resources which are worth exploring if you want to take an even deeper dive into the subject.
To get rolling, here is a CNBC interview of me talking about why, very generally, solar power is so important, and also talking about its potential to help the world today.
Secondly, here’s a video about how much the cost of solar has dropped in recent years and what that means, followed by an “About Solar / Why Solar” video that gets into the specifics of the solar energy and overall energy markets a bit more:
- Solar Power’s Abundance
- Falling Solar Power Costs
- Solar Energy Industry Growth
- Largest Solar Power Projects
If you’re looking for specific information on solar power technology, that’s not included here, but I’d recommend these resources for more on that:
- How Do Solar Panels, Solar Cells and Solar Energy Work?
- Solar Thermal Panels, Practical but Not Yet Popular – A Solar Overview
- Most Efficient Solar Panels — Which Ones?
- The Solar Power Wikipedia page
Solar Power Abundance!
“2009 Estimate of finite and renewable planetary energy reserves (Terawatt-years). Total recoverable reserves are shown for the finite resources. Yearly potential is shown for the renewables.” (Perez Perez, 2015)
No other energy source compares to the energy potential of sunshine. Looking at the image above, make sure to notice that circles for coal, uranium, petroleum, and natural gas are total recoverable reserves, whereas the renewable energy circles (including the giant yellow solar energy one) are for energy potential per year.
The bottom line: Solar energy is the most abundant energy source on the planet, by far.
For a micro-scale example, the solar energy hitting the state of Texas each month is equal to the total amount of energy the Texas oil and gas industry has ever produced.
Solar Power Costs
Now, a lot of politicians and people connected to or confused by the fossil fuel industry like to contend that solar power is expensive. Well, to put the matter bluntly: No, it’s not.
Technology improvements and policies to promote research, development, and installation of solar have resulted in tremendous drops in the cost of solar power over the past several years. Even without taking important health and safety costs (note that a Harvard study concluded in 2011 that the health costs of coal are 500 billion a year in the U.S.), environmental costs, energy security costs, and other social costs into account, solar is already cost-competitive with new electricity from conventional energy options like coal and nuclear energy (if you take into account how long it would take coal or nuclear plants to get built) — see the graphs below.
Note that the 2012 solar LCOE of 14 cents/kWh is already way out of date, with solar hitting 3–9 cents/kWh in the Middle East, USA, Brazil, and elsewhere.
Note that the 2012 solar LCOE of 14 cents/kWh is already way out of date, with solar hitting 3–9 cents/kWh in the Middle East, USA, Brazil, and elsewhere.
That’s just an appetizer, of course. For more along these lines, here are a few more stories on solar power costs:
- True Value of Solar Power
- Cost of Solar Power Competitive with Coal in Some Places, Dropping Fast
- Solar Power Graphs to Make You Smile
- Historic Report: Solar Energy Costs Now Lower than Nuclear Energy
- Another Low-Solar-Price Record: Saudi Electric Company Lands Solar PPA Under 5¢/kWh
- Dubai Gets Record-Low Bid Of 2.99¢/kWh For 800 MW Solar PV Project
Solar Power Industry Growth
Dropping costs, as well as concerns like global warming and air pollution, have triggered massive growth in the solar energy industry. I’m going to FOCUS on U.S. solar energy industry growth here, but the trends are similar globally and in other major economies, like China, Germany, the UK, Spain, and many other countries.
One of my favorite solar graphs is this one, which is on the exponential solar power growth we’ve seen in recent years:
Here’s another one that goes through 2014 and shows the annual growth trend:
Some more key facts for you:
- The U.S. solar energy industry now employs ~175,000 people (more than the coal or steel industry).
- The U.S. solar energy industry has been the fastest-growing industry in the U.S. in recent years. (It has been creating jobs 10 times faster than the U.S. economy as a whole).
- Over 5,000 businesses (mostly small businesses) support the solar industry in the U.S., creating jobs for Americans in every state.
- 9 out of 10 Americans think we should be developing and using more solar power.
Solar is expected to continue booming. In the U.S., it might even double each year up to 2020 (under the right policy scenario):
Here are some more posts on solar energy industry growth:
- Solar Power Could Produce 50% of Global Electricity, IEA Report Concludes
- Solar Power Graphs to Make You Smile
- Renewables = 99% Of New Electricity Capacity In Q1 2016 In USA (CleanTechnica Electricity Reports)
- US PV Installations Predicted To Pass 8 GW, Say GTM SEIA
- US Solar PV Installations Surpassed 6 GW In 2014 (Charts)
2.Explotation of solar energy
There are currently two main ways of exploiting the solar energy:
Thermal solar energy
The exploitation of the thermal solar energy consists in using the radiation of the Sun to heat up a fluid which, depending on its temperature, is used to produce hot water, steam or electric energy.
The systems to take advantage of the solar energy thermally can be divided into three groups:
- Low temperature systems. The heating of water is produced below its boiling water, that is to say, 100ºC. Most of the equipment based on this technology is applied to the production of domestic hot water and acclimatisation.
- Medium temperature systems. They are used in those applications requiring temperatures between 100 and 300ºC for heating, providing heat in industrial processes, supply of steam, etc.
- High temperature systems. They are used in applications requiring temperatures of more than 250 or 300ºC such as, for example, to generate steam or for the generation of electric energy in thermo solar power stations.
Photovoltaic solar energy
The photovoltaic solar energy is exploited by transforming it directly into electricity by means of the photovoltaic effect. This transformation is carried out by means of the use of photovoltaic cells.
What is a solar power station?
The solar power stations are installations designed to take advantage of the radiation of the Sun to generate electric energy. There are two types of installations with which the energy of the Sun can be used to generate electricity:
- In the thermo solar power station the generation of electricity is achieved by means of the heating up of a fluid with which using a conventional thermodynamic cycle, an alternator is moved thanks to the steam generated in the same.
- In the photovoltaic installation the obtaining of electric energy is carried out by means of photovoltaic panels that capture the luminal energy from the Sun to transform it into electricity. In order to achieve the transformation photovoltaic cells are used, which are manufactured with semi-conducting material.
Thermo solar power stations
A thermo solar power station is an installation that allows using the energy of the Sun to generate electricity using a thermal cycle similar to that of the conventional thermal power stations. There are different types of thermo solar power stations, although the most important are the following:
- Central tower power stations. They have a series of large directional mirrors that concentrate the solar radiation on a point. The heat is transferred to a fluid circulating along the inside of the boiler and transforms it into steam, thus starting a conventional water-steam cycle.
- Distributed collector power stations. They use the concentration collectors, which concentrate solar radiation received at the surface, which allows obtaining high performance temperatures of up to 300ºC, enough to generate steam at high temperature, which is used to generate electricity or for other industrial processes.
Operation of a thermo solar power station
A central tower thermo solar power station is made up by a field of large directional mirrors that reflect the light of the Sun and concentrate the rays on a boiler located in a tower at a great height.
In the boiler the calorific contribution of the solar radiation is absorbed by a thermal fluid which is taken to a steam generator, in which its heat is transferred to a second fluid (generally water) to transform it into steam.
This steam is taken to a turbine to transform its energy into mechanical energy which will be transformed into electricity in the alternator.
The steam is taken to a condenser where it is turned into water again in order to repeat a new cycle of steam production.
The production in a solar power station depends on the hours of sunlight. That is why in order to increase production thermal insulation systems inserted in the heating circuit are usually installed.
You can learn more about the thermo solar power stations in the following interactive game.
Limitations of the thermo solar power stations
The development of this type of power stations faces various limitations:
- Economic: their exploitation costs are still very high, that is why they are not competitive with other types of power stations.
- Technological: there are still many improvements in order to increase the efficiency of the concentration and storage systems.
- Seasonality: the viability of the solar radiation and the meteorological uncertainties have to be taken into account.
Photovoltaic farms
The photovoltaic effect is a physical phenomenon which consists of the conversion of luminous energy into electric energy. The generation of radiation (photons) on a heterogeneous structure (photovoltaic cell) is absorbed by the electrons of the most external layers of the atoms making up this material; this creates an electric current inside a determined voltage.
The cells are connected in series in order to make up a photovoltaic module.
Operation of the photovoltaic power stations
The basic element of a photovoltaic farm is the group of photovoltaic cells which capture the solar energy, transforming it into direct electric current. The photovoltaic cells are integrated in modules that, when joined together, will form photovoltaic panels.
The direct current generated is sent, initially, to a direct current cabinet where the transformation will take place with the assistance of a current inverter and, it is finally taken to a transformation centre where the current is adapted to the intensity and voltage conditions of the transport lines of the electric network.
You can learn more about the operation of the photovoltaic farms in the following game.
Limitations of the photovoltaic farms
The technology available has to be optimised for the efficiency of the photovoltaic cells to improve reaching figures of about 18-20%.
Spain in a pioneering country in the development of this technology and financial subsidies are provided to this type of electricity production.
Solar thermal power plant
Solar thermal power plants are electricity generation plants that utilize energy from the Sun to heat a fluid to a high temperature. This fluid then transfers its heat to water, which then becomes superheated steam. This steam is then used to turn turbines in a power plant, and this mechanical energy is converted into electricity by a generator. This type of generation is essentially the same as electricity generation that uses fossil fuels, but instead heats steam using sunlight instead of combustion of fossil fuels. [2] These systems use solar collectors to concentrate the Sun’s rays on one point to achieve appropriately high temperatures.
There are two types of systems to collect solar radiation and store it: passive systems and active systems. Solar thermal power plants are considered active systems. [3] These plants are designed to operate using only solar energy, but most plants can use fossil fuel combustion to supplement output when needed. [2]
Types of Plants
Despite the fact that there are several different types of solar thermal power plants, they are all the same in that they utilize mirrors to reflect and concentrate sunlight on a point. At this point the solar energy is collected and converted to heat energy, which creates steam and runs a generator. This creates electricity.
Parabolic Troughs
These troughs, also known as line FOCUS collectors, are composed of a long, parabolic shaped reflector that concentrates incident sunlight on a pipe that runs down the trough. The collectors sometimes utilize a single-axis Solar tracking system to track the Sun across the sky as it moves from east to west to ensure that there is always maximum solar energy incident on the mirrors. The receiver pipe in the center can reach temperatures upward of 400°C as the trough focuses Sun at 30-100 times its normal intensity. [2]
These troughs are lined up in rows on a solar field. A heat transfer fluid is heated as it is run through the pipes in the parabolic trough. This fluid then returns to heat exchangers at a central location where the heat is transferred to water, generating high-pressure superheated steam. This steam then moves a turbine to power a generator and produce electricity. The heat transfer fluid is then cooled and run back through the solar field. [2]
Parabolic Dishes
These are large parabolic dishes that use motors to track the Sun. This ensures that they always receive the highest possible amount of incoming solar radiation that they then concentrate at the focal point of the dish. These dishes can concentrate sunlight much better than parabolic troughs and the fluid run through them can reach temperatures upwards of 750°C. [2]
In these systems, a Stirling engine coverts heat to mechanical energy by compressing working fluid when cold and allowing the heated fluid to expand outward in a piston or move through a turbine. A generator then converts this mechanical energy to electricity. [2]
Solar Towers
Solar power towers are large towers that act as a central receiver for solar energy. They stand in the middle of a large array of mirrors that all concentrate sunlight on a point in the tower. These large number of flat, sun tracking mirrors are known as heliostats. In the tower, there is a mounted heat exchanger where the heat exchange fluid is warmed. The heat concentrated to this point can be 1500 times as intense as incident sunlight. [2] The hot fluid is then used to create steam to run a turbine and generator, producing electricity. One drawback with these towers is they must be very large to be economical.
Benefits and Drawbacks
Because these systems can generate steam of such high temperatures, the conversion of heat energy to electricity is more efficient. As well, these plants get around the issue of being unable to efficiently store electricity by being able to store heat instead. The storage of heat is more efficient and cost-effective than storing electricity.
Additionally, these plants can produce dispatchable baseload energy, which is important as it means these plants produce a reliable amount of energy and can be turned on or up at will, meeting the energy demands of society. [7] In addition to this, solar thermal power plants represent a type of electricity generation technology that is cleaner than generating electricity by using fossil fuels. Thus, these are some of the cleanest options for generating electricity. Despite this, there are still associated environmental effects of these plants as a full life cycle analysis can show all associated carbon dioxide emissions involved in the building of these plants. However, emissions are still much lower than those associated with fossil fuel plants.
Some of the drawbacks include the large amount of land necessary for these plants to operate efficiently. As well, the water demand of these plants can also be seen as an issue, as the production of enough steam requires large volumes of water. [8] A final potential impact of the use of large focusing mirrors is the harmful effect these plants have on birds. Birds that fly in the way of the focused rays of Sun can be incinerated. Some reports of bird deaths at power plants such as these amount the deaths to about one bird every two minutes. [9]
For Further Reading
For further information please see the related pages below:
- Wikimedia Commons. (August 18, 2015). AS1 [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/e/e5/12-05-08_AS1.JPG
- 2.02.12.22.32.42.52.6 EIA. (August 18, 2015). Solar Thermal Power Plants [Online]. Available: http://www.eia.gov/Energyexplained/?page=solar_thermal_power_plants
- Maria Trimarchi. (August 18, 2015). Solar Thermal Systems [Online]. Available: http://science.howstuffworks.com/environmental/green-tech/energy-production/solar-thermal-power1.htm
- flickr. (April 5, 2018). Parabolic trough [Online]. Available: https://www.flickr.com/photos/argonne/7783883506
- Wikimedia Commons. (April 5, 2018). Solar Stirline Engine [Online]. Available: https://commons.wikimedia.org/wiki/File:SolarStirling_Engine.jpg
- Wikimedia Commons. (April 5, 2018). PS10 solar power tower [Online]. Available: https://commons.wikimedia.org/wiki/File:PS10_solar_power_tower.jpg
- Visions of Earth. (August 18, 2015). Solar Thermal Power [Online]. Available: http://www.visionofearth.org/featured-articles/solar-thermal-power/
- Wisions. (August 11, 2015). Solar Power Tower [Online]. Available: http://www.wisions.net/technologyradar/technology/solar-power-towers
- Sarah Fecht. (August 11, 2015). Solar Power Towers are Vaporizing Birds [Online]. Available: http://www.popsci.com/solar-power-towers-are-vaporizing-birds
Lawan-Purohitsar ISTS plant 600 MW (-)
Another Indian plant – located further north in Jaisalmer district, Rajasthan – is a new entry to the list with a capacity of 600 MW. It is one of a series of projects contracted by tender to supply power directly into India’s Inter-State Transmission System (ISTS).
The PV project, which spans the communities of Lawan and Purohitsar in Pokhran, was connected recently by SB Energy, the company acquired earlier this year from Japan’s Softbank by Adani.
Topaz 550 MW (8)
The USA’s third plant in this list at 550 MW, Topaz was briefly the country’s largest plant when commissioned in November 2014.
Developed by First Solar, it is built on multiple sites totaling nearly 1,400 hectares in Carrisa Plains in central California. Coincidentally this incorporates the site where the world’s first multi-megawatt solar project was built in the 1980s (outlined in white on this image).
São Gonçalo 549 MW (-)
We go to Brazil for the first South American project to reach this list of the world’s largest solar plants. But it is the second entry in Latin America for Italy’s Enel Green Energy.
The plant near São Gonçalo do Gurguéia in the State of Piauí is being constructed in three phases with an eventual capacity of 765 MW. When phase II was completed in February this year, the capacity reached 549 MW.
The plant uses bifacial modules mounted on single-axis trackers, and currently covers about 1,300 hectares.
Other large plants
Just below our cutoff, with a present capacity of 480 MWAC, is Vietnam’s largest plant at Ea Súp in Đắk Lắk Province. This is due to be expanded, so may join this list in the future.
Other large projects in development may lead to Australia, Saudi Arabia, Chile, France, and Texas, amongst others, joining soon.
The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: editors@pv-magazine.com.