Solar Power- the most abundant renewable energy in the world

Solar Fast Facts

Enough solar energy hits the earth in one hour to power the entire planet for a year. Solar photovoltaic (PV) cells convert solar radiation to a usable form of energy: electricity ("photovoltaic" cells is simply another term for solar cells). PV solar power entails harnessing the sun's energy to directly produce electricity by converting sunlight into electricity through solar PV cells (the "photovoltaic effect"). The basic building block of the solar cell has commonly been silicon, an element found in sand (known as crystalline silicon solar cells). However, in modern advanced thin-film solar cells, silicon is replaced with other semiconductor materials; such as cadmium telluride, copper gallium. Even graphene has found a use in cutting-edge solar cell production (in solar cells still in R&D). Different forms of the traditional silicon cell, such as amorphous silicon, and nanocrystalline silicon, are being used in flexible, thin-film solar cells in production and use today.

A key advancement in the design of the solar cell is the production of more efficient solar cells using less expensive, and readily available materials. There have been recent breakthroughs in solar PV technology that have dropped the cost and increased the efficiency of solar cells- most significantly, with nano-PV and thin-film solar. Nano-PV solar cells result in much more cost-efficient, compact, thinner, and more energy efficient, solar units. Nanotechnologies in PV with from 4 to 7 times (or more) the efficiency of standard photovoltaic cells are currently being developed and implemented in all forms of commercial solar PV. There are nano, thin-film, and alternative material PV cells currently in R&D, and commercially available versions, with substantially higher efficiency than the standard silicon solar PV cell. Solar cells many times more efficient than even the most efficient commercially available solar cells are in limited beta-testing phases (see: engineers-just-created-the-most-efficient-solar-cells-ever, and The solar arrays now being produced today will be exponentially improved with the continued research, development, refinement, and implementation of nanotechnology.

These innovations in solar cell design are all developed to increase the efficiency of the conductivity of the cells, and decrease the cost of production of solar cells. Solar cells are combined with silicon, other organic materials, glass, and metal, to create solar panels, and solar panels are combined in what are known as photovoltaic arrays for home rooftops, buildings, properties, and microgrids; or large-scale (utility-scale) solar farms. The more efficient solar PV farms use utility-scale thin-film PV solar panel arrays. At the residential, business, or community level, (advanced) crystalline silicon is the norm for solar rooftop PV, and other small PV arrays for a property. Here is a basic illustration of how a solar rooftop PV system works:

illustration of a solar rooftop photovoltaic (PV) system

[1- rooftop photovaltaic array   2- home battery (optional home energy storage)   3- energy converter to produce usable electricity for the home from the solar energy    4- municipal grid (the home can sometimes send energy generated from its solar PV panels to the grid, in addition to continuing to receive electricity from the grid, see the links to net metering below)]

The most readily accessible form of solar power for most people is solar rooftop PV, or PV arrays for a convenient location somewhere on a property. However, in addition to solar PV for homes and businesses, community solar projects (and other solar microgrids) are also increasingly available throughout some cities; as exemplified by the city of Austin, Texas. The article on Green City Times that discusses community solar also describes net metering, in which a home/ building with rooftop solar PV panels, or a PV panel array on a property, provides excess energy back to the energy grid, lowering the energy bill of the building (*in cities and states where this is available). Also aiding the growing use of solar PV are incentives, rebates, and subsidies for solar PV (*in cities and states where government subsidies are available; and/ or in cities and states where rebates from manufacturers and retailers are available).

Large-scale (utility-scale) solar farms are created using arrays of thin-film PV panels, or created using a couple types of solar thermal technologies; such as concentrated solar power (CSP), and more mobile, smaller units of solar thermal energy such as dishes and troughs (parabolic solar). Solar water heaters can use solar PV, solar thermal technologies, or a hybrid of these solar technologies. Solar power, in all of its various forms, represents a consistently productive and continuously promising source of renewable energy. By combining solar energy with energy storage, the amount of energy that solar can provide is increased exponentially. Solar PV technology is consistently getting more efficient and less expensive.

Topaz Solar Farm
Topaz Solar Farm

An example of a large, successful, utility-scale solar photovoltaic farm using high-efficiency solar cell technology is the Topaz solar farm. Breakthroughs in solar cell technology are bringing the cost of utility-scale solar to cost parity with fossil fuels; as evidenced at Topaz, and throughout the global utility-scale solar industry, in new solar projects of all sizes and scales throughout the world. Solar PV continues to be a viable and constantly improving energy source to power the grid for most of the United States (in addition to other renewable energy sources, and non-renewable energy sources like natural gas and nuclear).Another key development in solar energy is the trend in the utility-scale solar industry of using natural gas and energy storage to augment solar energy production, which is intermittent and depends on the sun being out, or solar rays being able to get through the earth's atmosphere to hit the solar cells.

In addition to advancements in traditional photovoltaic technology and storage of solar energy, there have also been exponential advancements in the field of solar thermal energy. Instead of simply converting energy from the sun into electricity, with solar thermal technology, solar energy heats water, H2O + molten salt, or another working fluid, and then steam is used to drive generators. Solar thermal represents an advancement in solar energy with 4 to 5 times the power density of PV. However, reductions in the cost of this technology have been difficult to realize, but solar water heaters, and concentrated solar power (CSP) plants are successful commercial applications of solar thermal energy technologies. In addition to solar water heaters, and CSP, successful commercial solar thermal generation includes parabolic solar.

One commercially successful application of solar power is the solar powered water heater. Solar powered water heaters are mandatory in new construction in the state of Hawaii; and similarly installed in all new construction in the country of Israel, and other countries and localities. Some of the other applications of solar thermal energy include hot water and heating for homes, RVs, large appliances; and even in remotely situated buildings, in industrial buildings, schools, hospitals, etc...

Gemasolar Concentrated Solar Power plant in Seville, Spain
Gemasolar Concentrated Solar Power plant in Seville, Spain

The most promising new technologies in the world of utility-scale solar power are CSP and HCPV. Concentrated Solar Power (CSP) and High Concentration Photovoltaic (HCPV) are both technologies which use a large array of lenses and mirrors (heliostats) to focus sunlight onto PV cells set as a receiver on a central tower. An example of a large CSP plant is the Gemasolar Concentrated Solar Power Plant in Seville, Spain, and another is the Ivanpah Solar Plant in the Mojave desert. Similar to CSP, HCPV technological development holds great promise for the production of solar energy. HCPV is a technology which uses a large array of lenses or mirror collectors (heliostats) to focus and beam sunlight to a small area of solar cells. The concentrated light is then directly converted to power using the same means as other solar thermal arrays. - See more at: /HCPV

Concentrated solar power (CSP) plants/ farms, also known as concentrated solar thermal farms, use mirrors (heliostats) to focus sunlight onto a small receiver on a tower in the center of the array. An example of a large, successful CSP array in America is Ivanpah. The concepts in the solar thermal process take over as the concentrated light is converted into heat. CSP plants produce power by first focusing sunlight onto a concentrated group of solar cells arranged as an installation on a tower, and then using that heat energy to heat up a working fluid (like molten salt, oil, and/or water), creating steam, which drives a turbine. Great examples of CSP plants are found in Spain, Italy, Australia, and Mexico, as well as the US states California, Arizona, Colorado, New Mexico, Utah, and Nevada (just to mention a few locales for this emerging technology).

Also used for various power supply needs, and/ or in conjunction with CSP plants, are solar dishes and solar troughs. Solar dishes and troughs focus sunlight to heat a working fluid (such as molten salt, synthetic oil, and/or water). Dishes and troughs hold great promise for the future of renewable energy.

Dishes and troughs (parabolic solar) are often used in a CSP application, or applications like solar water heating, or on a stand-alone basis to power buildings, RVs, or large appliances. Solar dishes and troughs work by focusing sunlight onto a group of PVs, or a working fluid, or both, near the source. CSP plants first focus light on PV cells, then use that captured energy heat a working fluid, while solar dishes and troughs harness solar energy to heat a working fluid piped just above the dish or trough. Then, this high-temperature fluid is used to heat water, creating steam to spin a turbine or to power an engine that drives a generator.

Here's a quick illustration of a simple parabolic solar installation:

illustration of a simple parabolic solar installation

Both types of solar energy (PV and solar thermal) will continue to steadily lessen in cost as technological advancements are made. However, photovoltaic is projected to remain ahead of thermal in terms of cost of production and utilization. Solar thermal technologies do have a couple of advantages which compensate for the higher cost. Solar thermal energy is produced consistently throughout the day, not relying on weather conditions. The turbine will run on natural gas if there is no sun for an extended period of time. Solar thermal units fit easily with power storage systems and will continue to produce energy at night, using energy harnessed during the day.


Please click & read:


Recent breakthroughs in solar photovoltaic and solar thermal technologies

Community solar and net metering - pushing renewable energy forward

Ivanpah Solar Electric Generating System
The 550 megawatt Topaz Solar Plant

Renewable energy storage

Worldwide Subsidies, Credits, Rebates and Incentives for Renewables

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  1. Please let us here at Green City Times know what you think in a comment; and we’ll try and answer any questions as well.

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    [Dan Braff is the founder of GCT –

    Daniel Braff]

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