Last updated on March 15th, 2019 at 10:35 am
What is Solar Energy?
Solar energy is radiant heat and light from the Sun. It is an important source of renewable energy. There are two types of these technologies called active solar or passive solar. The difference is how they catch and share solar energy versus how they catch and turn it into solar power.
What is Renewable Energy?
Renewable energy is energy generated from natural resources which are renewable (naturally replenished). The United States currently relies on coal, oil, and natural gas for its energy. Fossil fuels are non-renewable. They draw on finite resources that will dwindle. They are becoming too expensive or too environmentally damaging to retrieve. In contrast, there are many types of renewable energy resources. Solar and wind energy are constantly replenished and will never run out.
Most renewable energy comes either directly or indirectly from the sun. Sunlight is our solar energy. The sun’s heat also drives the winds, captured with wind turbines. Then, the winds and the sun’s heat cause water to evaporate. Hydroelectric power is when this water vapor turns into rain or snow. Then, flows downhill into rivers or streams. Sunlight also causes plants to grow. The organic matter that makes up those plants is known as biomass. Biomass produces electricity, transportation fuels, or chemicals. Bioenergy is the name for using these. Hydrogen is another alternative. Once separated from another element, it is burned as a fuel or converted into electricity. It’s the most abundant element on the Earth. But it doesn’t occur naturally as a gas. Not all renewable energy resources come from the sun. Geothermal energy uses the Earth’s internal heat for a variety of uses. These include electric power production and the heating and cooling of buildings. The energy of the ocean’s tides come from the gravitational pull of the moon and the sun upon the Earth. This is tidal energy. Ocean energy comes from many sources. The ocean waves, from tides and winds. The temperature difference between surface and ocean depths. All these forms of ocean energy can be used to produce electricity.
Why is renewable energy important?
Renewable energy is important because of the benefits it provides. The main benefits are as follows:
Renewable energy technologies are clean sources of energy. They have a much lower environmental impact than conventional energy technologies.
It is energy for our children’s children’s children.
Renewable energy will not run out. Ever. Other sources of energy are finite and will someday be gone.
Jobs and the Economy
Most renewable energy investments spend on materials and workmanship. To build and maintain the facilities, rather than on costly energy imports. Renewable energy investments are usually spent within the United States. Mostly in the same state, and often in the same town. In doing so energy dollars stay home to create jobs. It also fuels local economies, rather than going overseas.
Meanwhile, renewable energy technologies built in the United States are being sold overseas. This also provides a boost to the U.S. trade deficit.
In the early 1970s, the U.S. faced oil supply disruptions. Since then, the U.S. has increased its dependence on foreign oil supplies instead of decreasing it. This increased dependence impacts more than our national energy policy.
What are the types of Solar Energy?
Passive solar is the name for technologies that put buildings facing the Sun. They will find and use special materials that can scatter light. They will also have designs that help the airflow without any blockages.
Active solar uses special systems like solar panels also known as photovoltaic (PV) systems. Also, concentrated solar power (CSP) and solar water heating to save
What are the most common uses of Solar Energy?
The two most common uses of solar energy are Solar Thermal and Solar Photovoltaic:
- Solar Thermal systems convert sunlight into thermal energy also known as heat. Most solar thermal systems use solar energy for space heating or to heat water, such as in a solar hot water system. The most common way solar energy is being used today by homeowners in America is by solar hot water systems. The heat from these systems can make steam. By using steam turbines, the steam can generate electricity.
Solar PV systems are systems that can convert sunlight into electricity. These systems use PV cells to do so. The more common term for PV cells is solar cells. Solar cells exist on rooftops,
- building and even vehicles have them integrated. Power plants have them installed scaled to a megawatt size.
History of Solar Energy
Albert Einstein wrote a paper in 1905 on the photoelectric effect. Titled: “On a Heuristic Viewpoint Concerning the Production and Transformation of Light”. This paper on the photovoltaic effect started to attract scientific attention.
Bell Laboratories worked on silicon semiconductors in the 1950’s. They discovered silicon had photoelectric properties. This helped to develop a silicon cell with 6% efficiency. Early satellites were the primary use for these first solar cells.
The “photovoltaic effect” is the ability of sunlight to excite the flow of electrons (electricity). It was first discovered more than 175 years ago.
Here is a summary of the first 175 years of humans discovery and use of photovoltaic technology:
- 1839 – Nineteen-year-old French physicist Alexandre Edmond Becquerel observes a physical phenomenon. Discovering light-electricity conversion. While experimenting with metal electrodes and electrolyte.
- 1883 – American inventor Charles Fritts describes the first solar cells made from selenium wafers.
- 1888 – First US patent for “solar cell” received by Edward Weston.
- 1901 – US patent for “method of utilizing, and apparatus for the use of, radiant energy” received by Nikola Tesla.
- 1905 – Albert Einstein publishes a paper on the theory behind the “photoelectric effect”. The same year he published the “theory of relativity” (E=MC2).
1916 – Robert Millikan experimented Einstein’s theory on the photoelectric effect.
- 1922 – Albert Einstein wins Nobel Prize for 1905 paper on the photoelectric effect.
- 1954 – Bell Labs exhibits first high-power silicon PV cell. The same year The New York Times forecasts solar cells will lead to a source of “limitless energy of the sun”.
- 1963 – Japan installs a 242-watt PV array on a lighthouse, the world’s largest array at that time. Sharp Corporation produces a viable photovoltaic module of silicon solar cells.
- 1966 – NASA launches Orbiting Astronomical Observatory with a 1-kilowatt PV array.
- The 1970s – Research drives PV costs down 80%. Reduced costs of offshore navigation warning lights and horns lighthouses. Also helped railroad crossings and remote use where utility grid connections are too costly.
- 1976 – Kyocera Corp starts production of Silicon ribbon crystal solar modules.
- 1977 – US Dept. of Energy establishes US Solar Energy Research Institute in Golden, CO. This organization currently known as NREL, the National Renewable Energy Laboratories.
- 1990 – Germany launches $500MM “100,000 Solar Roofs” program. The German’s spent the hard money when solar panels were still very expensive.
- 1994 – Japan starts “70,000 Solar Roofs” PV subsidy program.
- 2006 – The CA PUC launches the California Solar Initiative (CSI). A $3 billion solar subsidy program spanning 10 years.
- 2007 – The CSI program starts. Well received by the market, with higher than expected application volume.
- 2008 – The Energy Policy Act of 2005 (P.L. 109-58) created a 30 percent investment tax credit (ITC). For commercial and residential solar energy systems. Applicable January 1, 2006, through December 31, 2007. Tax Relief and Health Care Act of 2006 (P.L. 109-432) extended credits one more year in December 2006. In 2007, global investment in clean energy topped $100 billion. Solar energy leads clean energy technology for venture capital and private equity investment. The solar tax credits helped to create growth in the U.S. solar industry from 2006-2007. Solar electric capacity installations doubled in 2007 compared to 2006. The Emergency Economic Stabilization Act of 2008 (P.L. 110-343) added an eight-year extension. Covering commercial and residential solar ITC. This eliminated the monetary cap for residential solar electric installations. Companies and utilities paying the alternative minimum tax (AMT) qualified for the credit. In 2009, American Recovery and Reinvestment Act (P.L. 111-5) removed credit cap. The $2,000 credit cap on solar hot water installations no longer existed. This 30% Federal Tax credit renewed until 2016.
- 2008 – 2012 – Stronger subsidies in Germany and new subsidy programs in Spain, Italy, and Australia. The cost of PV modules falls from approximately $5 per watt to the $1 per watt level.
- 2010 – 2013 – Chinese manufacturing companies start to build large automated solar cell. Also, solar module production factories. This further reduced the cost of modules down towards $.70 per watt.
- 2012 – 2015 – Residential solar installations became cost effective for average American households. In 2015, more solar powers installed at home in the US over 18 months than in all the cumulative history before this.
- May 2015 – The Tesla Motor Company announces product launch of a lithium-ion battery storage. Price point would make it economic for ordinary American householders. Providing ability to store solar power generated during the day for use at night.
- Dec 2015 – The US Congress passed an 8-year extension to the 30% Federal Income Tax Credit. Ensures the continued growth and adoption of photovoltaic solar power systems in America.
How does Solar Energy work?
Our Sun is a naturally occurring nuclear reactor. It releases tiny packets of energy called photons. These photons travel 93 million miles from the sun to Earth. This only takes about eight-and-a-half minutes. Every hour, enough photons hit our planet to meet global energy needs for an entire year. Yet, solar-generated power in the United States accounts for 0.4% of the total energy consumed. As solar technology is improving, costs are dropping. Our ability to harness the sun’s surplus of energy is on the rise. A report from International Energy Agency states a big change by 2050. Solar energy could become the largest global source of electricity.
In the coming years, everyone will enjoy the benefits. As solar-generated electricity grows more popular every day.
PV solar panels
Photovoltaic (PV) solar panels are made up of many solar cells. Solar cells are made of silicon, like semiconductors. They are constructed with a positive layer and a negative layer, which together create an electric field, just like in a battery. When photons hit a solar cell, they knock electrons loose from their atoms. If conductors are attached to the positive and negative sides of a cell, it forms an electrical circuit. When electrons flow through such a circuit, they generate electricity. Multiple cells make up a solar panel, and multiple panels (modules) can be wired together to form a solar array. The more panels you can deploy, the more energy you can expect to generate.
Basics of electricity
PV solar panels are built of many solar cells. We use silicon to make Solar cells, like semiconductors. They are constructed with a positive layer and a negative layer. Both layers come together to create an electric field, like in a battery. When photons hit a solar cell, they knock electrons loose from their atoms. We can form an electric circuit by attaching a conductor to both positive and negative sides of a cell. When electrons flow through such a circuit, they generate electricity. Many cells make up a solar panel. We create a solar array by wiring many panels (modules) together. The more panels you can deploy, the more energy you can expect to generate.
Alternating current is one form of electricity, also known as AC. This is when electrons are pushed and pulled, reversing direction. This exchange is much like the cylinder of a car’s engine. Generators create AC electricity when a coil of wire is spun next to a magnet. Many different energy sources can “turn the handle” of this generator. Examples include gas or diesel fuel, hydroelectricity, nuclear, coal, wind, or solar.
The U.S. electrical power grid chose AC electricity. It is less expensive to transmit over long distances. Yet, solar panels create DC electricity. The only way to get DC electricity into the AC grid is by using an inverter.
A solar inverter takes the DC electricity from the solar array. It then uses that to create AC electricity. Inverters are like the brains of the system. Not only do they invert DC to AC power. They also provide ground fault protection. Provide system stats including voltage and current on AC and DC circuits. As well as stats on energy production, and largest power point tracking.
Central inverters have dominated the solar industry since the beginning. One of the biggest technology shifts in the PV industry was the introduction of micro-inverters. These inverters optimize for each individual solar panel. Rather than an entire solar system, as central inverters do. This enables every solar panel to perform at maximum potential. One solar panel will not drag down the performance of the entire solar array. In contrast, central inverters optimize for the weakest link.
Putting it all together
Here is an example of how a residential solar energy installation works. First, sunlight hits the solar panel or PV array on the roof. The panels convert the energy to DC current. This flows to the inverter. The inverter changes the solar DC power in 240V AC. This is suitable for your household appliances and feeding into the grid. Your home uses electricity from the solar PV modules first. Any additional demand is supplied from the Grid. A meter measures your electricity production and consumption. Any excess is exported to the electricity Grid.
The above example illustrates the basic idea of solar energy in the home. At this point, there may be a few questions. What happens if you are not at home to use the electricity the solar panels generate every sunny day? What happens at night when the solar system is not generating power in real time?
One way to solve this is to store the solar-generated energy for later use. If there is no home battery installed, the energy will flow back into the grid. But don’t worry, you still benefit from a system called “net metering”. This is the other solution.
A grid-tied PV system has no batteries. Neighbors will receive any excess power generated that is not used. This is known as “back feeding” the grid. At night, the grid will provide energy for lights and other appliances as usual. This covers solar users in exchange for the excess energy they shared with the grid during the day. A net meter records the energy sent compared to the energy received from the grid.
Now over 20,000 megawatts of solar electric capacity is operating in the United States. Around 650,000 homes and businesses have now gone solar.
In 2014, every two-and-a-half minutes a new solar project was installed. Projections say solar capacity will double in the next two years. Solar energy is the wave of the future. The sun belongs to everyone. Anyone can enjoy the freedom solar power systems provides. We need to commit to unlocking its vast energy. It all starts with a single solar cell.
How much energy can you get from solar electricity?
The map above shows the average amount of solar power produced each day from each state of the USA. Each number corresponds to the amount of kWh produced by the 1-kilowatt solar power system. As you can see the amount of electricity varies depending on your location. It also varies by the season and so the estimates given in the map above are annual averages.
Please note that these numbers are averages for the whole state. Some parts of some states have different climatic conditions. These numbers may not reflect when you live necessarily.
Across the USA daily production per kilowatt installed varies. From as little as 2.9 kWh per kW per day to almost to 4.7 kWh in very sunny locations.
The amount of electricity produced by each kW of solar you install will vary. This will depend on the level of solar irradiation that falls on your home or business. Solar irradiation is often measured in Sun Hours. Meteorologists measure Sun Hours in megajoules. Measuring total amount of irradiation in an area in each day. Next, they calculate complete hours compared to an area with 1000 megajoules per square meter on an area.
For example, if there were 500 megajoules falling on average over a 12 hour day then the Sun Hours would be 6.
These numbers may be confusing but are important. They relate to the output of solar panels. Solar panels are rated based on the power they produce. Per 1000 megajoules per square meter of irradiation falling on them.
Sun Hours measure irradiation. With this number, we can work out the actual amount of power we will produce. Real world solar power systems do produce less than their rated output.
The factors that reduce power rating include:
- Inverter inefficiency – most inverters will lose 3-5% of electricity when converting from DC to AC
- Cable Losses – small amounts of power lost through resistance in the cables
- Dirt – dirt, and grime on solar panels will reduce their real world performance.
- Temperature losses – solar panels are rated based on what they produce at 25 degrees celsius. As the cells in solar panels get hotter there is more resistance to the flow of electrons across the cells. Their power output reduces compared to when they are at a lower temperature. Even with the same level of irradiation.
Overall, total losses due to these derating factors will generally be between 20-30%. Yet, when we are working out the real world power of a system we usually use a derating factor of around 25%.
Please note when using the map above, estimates assume a perfect installation. Positioned due south, at an optimal tilt angle, and unshaded.
Pros and Cons for Solar Energy
Below are the advantages and disadvantages of installing solar panels on your home.
Advantages of Solar Energy
Marginal cost of generation is zero
Once the capital cost of installing a solar power system has returned, the energy is free. This is the most significant attraction for American homeowners. The only remaining question is how long the payback period will last. When comparing, it is possible this is a better deal than other ways to invest money.
Most homeowners are more interested in financial aspects of installing this system. Rather than the environmental benefits.
Insurance against rising power prices
Current solar panels have a year life of at least 25 years. By installing a solar power system on you home, you lock in a price for energy during this period. First, you need to calculate how much energy the solar panels will produce. Next, you can get an accurate price quote calculating each kilowatt-hour over the next 25 years. Many consumers are now able to get a Levelized cost of energy of $0.10 per kilowatt-hour. Next work out your average amount to pay for power over the next 25 years. Once your quote is available, you can compare the savings.
The average consumer with a $150 per month power bill can see savings in the range of $30,000 over the life of a solar system. At the beginning, the monthly savings are not huge. This may only be $50 per month but in the 25th year, it can reach savings of up to $300 per month.
Solar energy is a renewable energy source. NASA estimates that the sun will shine for another 6.5 billion years. This means that solar energy is abundant, and will never run out in our lifetime. The surface of the earth receives 120,000 terawatts of solar radiation (sunlight). This is 20,000 times more power than what needed to supply the entire world.
Harnessing solar energy does not generally cause pollution. There are some emissions during production and installation of solar energy equipment. These emissions are minimal when compared to generating electricity from fossil fuels. An Australian government research body (The CSIRO) estimates energy payback is 1.5 years. This means it takes a solar panel 1.5 years to generate the amount of power it took to make it. These numbers are from a statistic back in 2009. It is likely a lot quicker payback now. As solar panels last 25 years, this is good news.
Geographically widely available
The level of solar irradiation that falls upon the earth varies with the geography of the planet. Generally, the closer to the equator the more accessible solar energy is. What most do not realize is that solar energy is available anywhere.
In the sunniest parts of America, a solar system will produce on average 4.7 kWh of power per 1 kilowatt of solar panels.
The least sunny areas are different, such as in the mountains and northeast. In this area, it will produce 2.9-kilowatt hours per kilowatt, per day. Some areas are better than others are. For solar power, it is still viable in almost all locations.
Reduces Electricity Costs
Two schemes have been recently introduced net metering and feed-in tariff (FIT) schemes. Homeowners can now “sell” excess electricity or receive bill credits. This is possible during times a home produces more electricity than consumed. This means that homeowners can reduce their electricity expenses by going solar.
Data from www.solar-estimate.org show that adding solar panels can bring big savings. Annual savings of well above $1000 per year in many states.
In California, residents save on average $28,000 after 20 years! The availability of solar finance options has made it more affordable and available. Through Solar PPA agreements and zero down loans.
Community Solar can be used to overcome installation issues
Many American homes are unfit for solar panels. Due to shading, insufficient space and ownership issues.
With the introduction of shared solar, homeowners can subscribe to “community solar gardens”. With this approach, your own rooftop does not need any solar panels. the community generates the solar electricity.
Installation costs of many panels installed on vacant land are cheaper. This is a great advantage.
With this approach, Legislation is a need. This enables installations of community solar in each state. This has been available for some time now, but only started to arrive in California and New York.
No moving Parts means no noise and little maintenance
Solar panel systems have no moving parts. Also, there is no noise from the PV technology. When compared to other renewable technologies, solar wins in this category. One alternative like wind turbines has moving parts and causes noise pollution.
Financial Support from Government/State
In December 2015, the US Senate passed an extension of the 30% Renewable Tax Credit. This federal incentive extended the tax credit for a further 8 year.
There are also rebates available in some jurisdictions. Available at either the state, county or utility company level.
Technology is improving
Technology is always developing new advancements. This includes the design and manufacture of solar power equipment. Solar cells are becoming more efficient at turning solar energy into electricity. The amount of space required to generate a specific amount of solar power is reducing. As the popularity of solar increases, so will the dramatic advances. Improvements are incremental. Nothing revolutionary yet, but the future is bright.
Disadvantages of Solar Energy
High Capital Cost
Most people understand that solar power is expensive. This is one of the most debatable topics on the entire solar energy pros and cons list. Politics is the driving forces behind the development of solar energy.
Solar power received government subsidies. Yet, oil and coal industries have also been subsidized.
In 2010, coal received $1,189 billion in federal subsidies. Coal also received support for electricity production. Meanwhile, solar is not far behind at $968 billion.
Nowadays, the best solar panels can be cheaper than buying electricity.
Solar energy is an intermittent energy source
There are three aspects to the intermittent nature of solar power:
- The sun does not shine at night meaning solar panels do not generate power at night.
- The sun shines with different intensity. This changes based on location and time of year. Also, each day the sun shines at different times.
- Cloud cover can have a significant effect on the amount of energy produced by solar panels.
In the past, all these factors have meant that solar power is unreliable. It is a risk if relied on for baseload or for mission critical applications.
This is now changing. Tesla Motors announced last year a new product to solve this issue. A Lithium Ion battery for the home. This solution will allow consumers to cost-effectively store solar power energy.
Energy Storage is Expensive
Energy storage systems such as batteries will help smoothen out demand and load. This will make solar power more stable, but these technologies are currently expensive.
Looking at the numbers, we are fortunate. There is a good relation between our access to solar and energy demand. Our electricity peaks in the middle of the day. That is the same time there is a lot of sunlight!
Associated with Pollution
While solar power is less polluting than fossil fuels, some problems do exist. There are some greenhouse gas emissions associated with some manufacturing processes. Nitrogen trifluoride and sulfur hexafluoride are the talked about ones. The production of solar panels has found traces of these.
These are some of the most potent greenhouse gasses. Having many, thousand times the impact on global warming compared to carbon dioxide. Transportation and installation of solar power systems can also cause pollution.
The lesson of the day is: There is nothing that is completely risk-free in the energy world. Yet, solar power is most favorable when compared with all other technologies.
Certain solar cells need materials that are expensive and rare in nature. This is especially true for thin-film solar cells. Based on either cadmium telluride (CdTe) or copper indium gallium selenide (CIGS).
Power density is also called watt per square meter (W/m2). Used when looking at how much power an energy source has in a certain area. In this case, we are looking at real estate. Low power density means we need more real estate to get the power we demand at a good price. The global mean power density for solar radiation is 170 W/m². This is more than any other renewable energy source. But it cannot compare to oil, gas and nuclear power. Not yet anyway.
Solar doesn’t move house
One disadvantage with installing solar panels on your home is that it is expensive to move. If you move house, it is not easy to bring it with you. The net metering agreement with your utility is fixed to the property.
Yet, in practice, solar panels add value to a home. If you do move, you are likely to see the value of your investment in solar panels reflected in a higher sale price. The easiest way, in this case, is to buy the solar panels outright. With a lease or PPA, you need the new owner to agree to take over the agreement. That can be tricky.