Solar power is undeniably the way of the future for energy. It allows us to harness a free, everlasting power source and convert it to electricity in order to keep our modern lives comfortable and pollution-free.
But although we think of solar power as a cutting-edge technology, it is not really a new concept. The sun is and always will be the ultimate fuel source for our planet. Even fossil fuels began as sun rays: light particles (photons) were absorbed by plants and converted to energy during photosynthesis, allowing the plants to grow and even transferring that energy to animals who consumed the plants. Over the course of millions of years, the remnants of these plants and animals were compacted into the fossil fuels that have recently powered our lives.
Now that we struggle to find new sources of finite fossil fuels and to deal with the repercussions of pollution, it makes sense to cut out the “middlemen” and get our energy from the sun itself.
As with any technology, the methods of capturing solar energy become more refined and efficient, more widely available and cheaper to produce with each passing year. Whereas many commercial power plants used to run on coal, for example, solar power plants are now operating around the globe, producing mass quantities of energy and providing local citizens with clean energy. Gone are the days when you had to buy or build your own solar panels to escape from fossil fuels.
An Overview of Solar Harvesting Methods
“Solar power” can actually refer to several specific methods of energy capture. Solar thermal energy and solar photovoltaic cells are the two main solar power technologies. Here is an overview of these solar harvesting methods, as well as other terminology you may come across.
Solar Thermal Energy
Solar thermal energy represents a broad category of solar power that collects heat from the sun and uses this heat to increase the temperature of water or air, to aid in cooking and drying, or to concentrate the sun’s thermal energy in order to create electricity. Solar thermal energy is categorized by the temperature stored by the system.
Low-temperature solar thermal energy collectors are commonly used to heat buildings. The sun heats a “collector,” which also serves as the channel through which outside air passes into the building. The heat is transferred from the collector to the air as it passes through, thus heating the building.
Medium-temperature collectors are used to heat water, to dry lumber and food, to cook, and to purify drinking water. This is often an inexpensive and straightforward heating method, as the collector concentrates the sun’s heat and transfers it directly to the water, lumber or food. To purify drinking water using solar thermal energy, a simple distillation device is required in order to allow the water temperature to increase until evaporation, and then to allow the steam to cool back into liquid water in a separate chamber.
High-temperature collectors are the most sophisticated, and this method is also known as concentrated solar power. The collectors can be designed in several ways, including large reflective dishes, towers surrounded by reflective panels, or parabolic troughs. The heat is concentrated onto a single spot: for example, a dish will be designed so that sunlight bounces off of each area and onto a single reception point, or the panels surrounding a tower will all reflect the sun’s heat onto one specific reception point on the tower. These reception points can become incredibly hot. Temperatures of over 1,000 degrees Farenheit have been recorded. As a result, water is converted into steam, which powers an engine, which then produces electricity.
A unique example of a high-temperature solar thermal energy collector is a solar evaporation pond. Solar evaporation ponds are shallow pools of water in which a difference in salt content is naturally maintained between the bottom and top halves of the pool: the bottom layer of water has a higher salt content than the top layer, and the two rarely mix. This characteristic is key to the success of a solar evaporation pond, because it prevents heat from rising from the bottom of the pond to the top. Therefore, heat is trapped in the bottom of the pond and can be used to generate steam and, thus, electricity.
Small-scale solar concentrators can be used to power your home, but solar thermal energy stations require large, contiguous spaces of land that receive minimal cloud cover. Spain, Australia and the U.S. currently have the most and the largest solar thermal power stations.
Solar Photovoltaic Cells
Solar photovoltaic (PV) cells somewhat mimic the natural process of photosynthesis, which takes place inside a plant’s chloroplast cells.
PV cells are made of materials, like silicon, that naturally form strong electrical bonds. However, because an electrical current is only created when these bonds are disrupted, chemical impurities are added to the silicon to make it less stable.
When photons (light particles) interact with a PV cell, they are able to essentially rearrange the chemical bonds slightly, thus displacing electrons. PV cells are designed to have a clear electrical gradient (a negatively charged side and a positively charged side) in order to usher these electrons together. It is this flow of electrons that makes an electric current.
Solar photovoltaic cells are more likely to be used to produce electricity on a smaller scale than solar thermal, making it possible to mount one or two onto your roof. Like solar thermal energy, solar photovoltaic cells can be set up on large tracts of land in order to produce enormous amounts of energy all at once, so they are another viable option for commercially-available and cleanly-generated electricity.
It’s also important to mention passive solar during our discussion of solar power. Both solar thermal energy and solar photovoltaic cells are known as “active” solar energy systems. In other words, the collecting dishes that concentrate the sun’s heat or the PV cells that manipulate the sun’s energy outputs are both enhancing the effect of the sun to our advantage.
Passive solar also takes advantage of the sun, but in ways that don’t require collecting dishes or other forms of technology. Passive solar relies mainly on thermal mass, or the ability of a surface, such as a road, to retain heat.
Passive solar water heaters are useful for single-family homes, because the water container is small enough to allow the sun to directly heat the water and to provide warm water for a shower or for general home use. This differs from the solar thermal energy systems of larger, commercial water heating systems in which a small amount of water is heated thanks to the solar collectors, and then circulated around larger tanks of water to facilitate heat transfer.
Greenhouses are a perfect example of the power of passive solar heating, and cleverly positioned home windows can also take advantage of the sun by receiving sunlight during winter months and avoiding it during the summer months, when the sun is at a higher angle in the sky.
Notable Solar Power Plants to Date
The good news is that the record for being the largest solar power plant is constantly being broken year after year. In fact, Morocco is currently building a solar thermal energy station that will claim the title, at least for a while.
A few countries are known to have an impressive number of megawatts generated by solar power, or to have the largest arrays in the world. Here’s a quick look at the world’s current solar superstars:
The southwestern region of the U.S. is home to most of the country’s solar power stations. This region not only has the most sun exposure, but also is mostly desert, making it the perfect space to build sprawling power stations out of the way. The Ivanpah Solar Power Facility in San Bernardino County, CA is the country’s largest solar thermal power station, producing 392 MW of energy. The country’s largest solar PV power station, Solar Star, is located nearby in Rosamond, CA and produces 579 MW.
Spain receives exceptional sun exposure, more so than most other European countries. The southern region of Spain is riddled with solar power stations, and the country boasts the largest number of solar thermal energy stations in the world, with dozens more planned. The largest of Spain’s thermal stations is the Solaben Solar Power Station, a parabolic trough design that produces 200 MW of energy and is the sixth largest in the world (only the U.S. has larger thermal stations). Its largest PV station, Olmedilla Photovoltaic Park, was the largest in the world when it was built in 2008, but its size has since been surpassed by stations in a dozen other countries.
India currently boasts the world’s largest solar PV power station, the Charanka Solar Park. It was built in 2012, uses thin-film technology, involves projects by more than 19 different developers and has a capacity of 600 MW. India’s largest solar thermal power plant is a modest size, on a global scale, at 50 MW and is known as Godawari Green Energy Limited.
Germany has a handful of solar PV power stations that rank among the largest in the world, including Solarpark Meuro, Neuhardenberg Solar Park and Templin Solar Park, as well as a couple of solar thermal energy stations. However, Germany’s total solar power production tops any other country in the world, with over 35 GW capable of being produced by both commercial and residential solar power systems. In comparison, the U.S. has a capacity of around 19 GW produced by solar.
And finally, speaking of notable power plants, who says solar power stations have to be an eyesore? A modest PV power station in New Caledonia certainly proves otherwise, as its panels are arranged in the shape of a shiny heart on a backdrop of lush green grass.
The Future of Solar Power
We’ve seen how solar power is quickly replacing the need for coal-fired power plants around the world and even how homeowners can use solar power to replace natural gas water heaters. These are just two of the many exciting innovations in solar technology that we can expect in the next few years.
Transportation Industry and Solar Power
Transportation represents another major energy niche in which solar power is currently but a minor player. Can solar power really compete with diesel and gas-powered vehicles? Perhaps not directly, but with the rising popularity of electric vehicles, solar can play a part by providing the electricity used to charge such cars.
While it’s projected that diesel will continue to be used as the fuel of choice, at least for a while, by many in the trucking industry, solar power is not entirely out of the question. One company in particular is designing solar panels that will charge a truck’s battery, which is a huge benefit to drivers with refrigeration units. Known as SolarFlex panels, these PV cells are easily installed onto the roof of the cab with a simple adhesive.
Solar Panel Windows and Solar Roadways
Why relegate solar panels to rooftops and vast tracts of desert land? Virtually any surface that the sun touches could be transformed into an energy-producing gadget, which would hasten the world’s transition to clean energy. That’s the idea behind two exciting new innovations in solar technology: solar panel windows and solar roadways.
The solar panel windows are transparent, allowing them to perform as a window pane and as a solar energy harvester and allowing you to get the most out of your home’s sun exposure. Solar roadways is an exciting project still in development, but the tough panels promise more than just energy production, including customizable lighted patterns, heated roadways, improved repair times and excellent traction.
Solar technology is a rapidly progressing industry, and advancements are made every single year. It won’t be long before we all can benefit from clean and inexpensive electric power generated by the sun.