A Beginner’s Guide To How Solar Technology Works

By Nicholas Brown.

Solar energy is defined as radiation of various wavelengths emitted by the sun. A solar-powered generator may be defined as a device or group of devices used to generate solar power using the sun’s rays (solar radiation/solar energy).

Photovoltaic solar panels are the most common technology used to generate solar power around the world.

There are a variety of ways to utilize solar power, and they will be explained below.

Contents

  1. Photovoltaic Cells
  2. What is the Problem with Solar Power?
  3. Backing Up Solar Power Plants
  4. How do I set up a solar power system and what wattage do I need?
  5. If not the entire house, which appliances should I power?
  6. Transfer Switch
  7. How much space do I need for solar panels?
  8. Relationship between cost and weather: What happens when it becomes overcast?
  9. Importance of Appliance Efficiency to the Cost of A Solar Setup
  10. Importance of Battery Efficiency to Solar Setups
  11. Can Solar Panels Fully Power My House?
  12. How to Store Solar Energy or Back Up Solar Panels
  13. Solar Panel and Solar Cell Efficiency
  14. Total Area and Single Cell Efficiency
  15. Controllability of Solar-Powered Generators
  16. Factors Affecting Cost of Solar Power
  17. Cost of Solar Power (including residential)
  18. Solar Thermal Energy
  19. Solar Water Heaters
  20. Applications of Solar Power

Photovoltaic Cell Technology

A large-scale solar power system.

Solar panels. Image obtained with thanks from USFWS Mountain Prairie on Flickr.

Photovoltaic cells are constructed of semiconductor materials (solid state) which convert the sun’s rays directly into electricity. People are most familiar with this type of solar power generator and it is also the most common for residential use. Solar cells are encased inside solar panels for protection.

How photovoltaic solar technology works: NASA Explanation.

Some of the semiconductor materials used in the construction of solar cells and solar panels includes:

  • Monocrystalline Silicon.
  • Polycrystalline Silicon.
  • Amorphous Silicon.
  • Gallium Arsenide (GaAs).
  • Cadmium Telluride (CdTe).
  • Titanium Dioxide.
  • Copper Indium Gallium Selenium (CIGS).
  • Copper Zinc Tin Sulfur/Selenium (CZTS).
  • Carbon Nanotube.

Some of the types of solar photovoltaic cells include:

  • Silicon wafer.
  • Thin Film.
  • Dye Sensitized Thin Film.

Advantages of Solar Power Systems

  • Solar panels (PV) are completely solid state and require no maintenance.
  • Solar panels have a long lifespan of 20-30 years.
  • They emit no pollutants nor radioactive waste so they can safely be used indoors.
  • Solar technology requires no fuels which are susceptible to price fluctuations.
  • Photovoltaic solar technology produces no noise nor vibration.
  • They can be manufactured for use on almost everything, because thin-film solar panels can be printed on plastic, glass and other substrate.
  • They are a convenient way to keep portable electronics’ batteries charged if solar cells are attached to the back of them.
  • Solar panels and other types of solar technology typically generate more electricity when electricity demand is higher due to increased solar radiation. Electricity demand is the highest when solar radiation is greatest.

One reason for this is increased air conditioner power consumption due to both increased use and inverters turning air conditioners up to meet cooling demand which automatically increases with environmental temperature.

  • The cost of solar power remains the same over the solar generators’ entire 30 year life because they require no fuel.
  • More light can be reflected on solar panels during low light periods using mirrors, this is more economical than purchasing additional solar panels to compensate for cloudy weather, but is more complex to setup and I do not know of any organization which offers that.
  • Solar power can help the electricity grid during peak hours when electricity demand is highest (because solar panel electricity generation peaks when electricity demand is highest), making it possible to decrease the amount of blackouts and brownouts caused by shortfalls in generating capacity.
  • Use of solar-powered generators as an alternative to fossil fuels means that less fossil fuels will be used to generate electricity, causing fossil fuels to last longer and helping to mitigate increases in demand which normally result in an increase in their cost. Greater fuel demand = higher fuel prices.

Disadvantages of Solar Power

  • The manufacturing cost of solar technology is high.
  • Solar technology in general is expensive to install, this is an even bigger issue than the cost of the panels themselves.
  • The cost of electricity from central solar power plants is high.
  • Solar panel efficiency is usually low, therefore the power production per square meter is low. An average of 110 to 200 watts per square meter. This means that solar power plants (not rooftop systems) occupy a large amount of land.

You must use an electricity usage meter (such as the Kill-A-Watt for example) to determine the power consumption of individual appliances which often varies. If you are using a grid-tie setup to solar power your building, then you don’t need to worry about metering your appliances yourself.

How To Set Up Solar Panels/How To Solar Power Your Home:

This section has a page of its own.

If not the entire house, which appliances should I power with my solar system?

Some appliances are easier to power with solar panels than others. This is due to the fact that it is easier to gauge their power consumption. A refrigerator, for example, is not the most straightforward appliance to solar power because of its intermittent operation which varies with weather, provided that the kitchen is not climate controlled (heated or air-conditioned).

In most cases, whichever appliance you choose to power with solar energy, the ratio of the amount of money spent on the solar setup to the amount of money saved by the solar panels is the same.

Therefore, powering your lamps with solar energy won’t necessarily save you more money and supplying those with solar power requires an electrician which has to be paid, so that actually costs more than solar powering plug-in appliances such as standing fans.

It is important to note that solar panels are cheaper in large quantities, so if you want to power your house with solar energy, then buy all the panels at once. You can obtain them for less than $3 per watt in such quantities.

Transfer Switches Make Solar Power A Reliable Option

A transfer switch is a device that enables you to directly solar power your items with a minimal amount of batteries in such a way that you would be backed up by the electricity grid, but without a grid-tie inverter/net metering system. You could also enjoy a limited amount of power during power outages from the electricity grid.

Basically, the solar panels would charge very few batteries, even a couple depending on your setup, their size, and your power consumption, and those batteries would buffer that power to your appliances. If the weather becomes cloudy for an extended period of time, the transfer switch can switch you over to the electricity grid so that you will not have to purchase extra panels to compensate for the reduced power production during that weather.

The capital cost of such a setup can be significantly lower than that of a traditional setup which consists of extra panels, because extra panels cost plenty of extra money. In other words, the cost per watt to install this is far less than a typical setup, so it pays for itself much faster.

The drawback is that it only saves energy during the day so it cannot completely eliminate your electric bill, but it can reduce it.

If you know how to set up a regular 120 volt inverter, batteries, etc, you can avoid the electrician’s fee and do the in-home part of this job yourself.

How Much Space Do I Need For Solar Panels?

To determine how much space you would need to place your solar panels flat on a surface such as your roof, you would first determine how much power a square metre of them would generate.

You would do this by multiplying the decimal efficiency rating of the panels by the amount of sunlight received by the earth per square meter when it is sunny (this is just a guideline) which is 1,000 Watts/sq metre.

The average solar panel is 10% efficient (it can be as much as 22%, but it is usually 10%, so use 10% as a guideline). Multiply 0.10 by 1000 and the result is the number of watts per square metre that specific model of panel generates which is 100 watts/square metre. You would purchase many of that same panel to achieve your desired electricity generation capacity.

Second: To finally determine how much space you would need in square metres on the surface you are putting the solar panels flat on top of, you would divide the number of watts that you intend to purchase by the watts/square metre figure which is 100.

So if you are purchasing 300 watts of those solar panels, you would divide 300 by 100 and the result is that you would require three square metres of panels to generate a maximum of 300 watts of power.

If you want the U.S. average of 3,000 watts of solar panels for your system, that would require 30 square metres of space.

For smaller projects, it is easier to use small units such as square centimetres. Simply divide the watts per square metre figure by 10,000 to determine the wattage per square centimeter. If you prefer square inches, then divide the watts per square metre figure by 1550.0031.

Example: 120 watts/square metre (12% efficient) in square centimetres is 120 / 10,000 = 0.012 watts per square centimeter, or 12 mW, or milliwatts/square centimeter. Visit the power consumption page for more information on energy units.

Solar-Powered Blackberry Example: If a Blackberry 8320 has 54 square metres of space available on the back of it for solar cells, then if you were to attach 12% efficient solar cells which cover that area, they could generate 648 mW or 0.648 watts total, if the back of the blackberry is exposed to direct sunlight.

Calculating area of a rectangle or square in square centimetres: measure the length and width of the flat object that you want to determine the area of, and then multiply the two together because area = length x width. The laptop area I measured was 24 x 30 cm = 720 square cm.

Solar-Powered Laptop Example: If you wanted to cover the back of a laptop monitor with 30 cm x 24 cm (720 square cm) of 12% efficient solar cells, they could generate 8.64 watts, which is not ideal for a laptop. A 20% efficient solar cell would be much more useful because it could generate 14.4 watts. All of this only applies if the solar cells are exposed to direct sunlight


Importance of Apparatus/Appliance Efficiency To the Cost of A Solar Power System

In some cases, you can lower the overall up front cost of a solar power system significantly by slashing your power consumption. Here are some examples which definitely pay for themselves where lowering the cost of solar power systems is concerned:

Lighting: Switching from incandescent to fluorescent light bulbs. Solar panels cost $2-$4 per watt excluding installation, this is extremely expensive compared to fluorescent bulbs which cost $0.26 per watt and sometimes less.

If you had to choose a 75 watt incandescent over a 15 watt fluorescent, both of which are a similar brightness, you would have to spend an additional $120 to $240 on solar panels to produce enough power for the incandescent light bulb. So the return on the fluorescent investment in such a case would be very sound and prompt.


Importance of Battery Efficiency to Solar Power Systems, Battery Technology Varies (Significantly)

Another factor which can significantly affect the wattage of the solar panels needed (this applies to off-grid setups) is the efficiency of the batteries you will charge with the solar power system.

Remember that batteries don’t only back up your solar system at night, they also act as a buffer for solar power, the amount of energy supplied by the batteries is always less than the energy supplied to them by solar panels or whatever else charges them.

Example: If a battery is 80% efficient then you get back 80% if the solar power that you supplied to it, the other 20% is lost as heat.

For the sake of simplicity: If you were originally contemplating a 100% efficient lithium-ion battery (which is not realistic),and decided to use a 50% efficient lead-acid battery because it is “cheaper”, you would need to purchase twice as many solar panels.

The lead-acid batteries waste 50%-80% of the energy produced by the solar panels, so if you purchased your solar power system with the hope of getting 1,000 watts from it,  you would only get 500 watts, so this is why you would need to buy twice as many panels.

Lead-acid batteries are 50% to 80% efficient, and lithium-ion batteries are 80% to 99% efficient.

So, by doing this, you would actually incur a huge up front cost, which is the cost of the extra panels.

Can Solar Technology Fully Power A House?

Yes, they can. Any type of generator can be used to power your house completely, but solar panels are costly, so people usually buy them to supply only a portion of their electricity, or to partially offset electricity consumption.

How Do I Store Solar Power Or Back Up My Solar Panels?

Solar power can be stored or supplemented using a variety of methods, some common methods include:

  • Deep-cycle lead-acid batteries.
  • Natural Gas/Propane (LPG) fueled generator.
  • A combination of the above.

One can either use a large bank of batteries which are kept charged by the solar panels during the day to supply the house with electricity all day, so the solar panels would not directly power the house.

One can also use a smaller and much cheaper bank of batteries which would be charged by the solar panels during the day, and the batteries would supply the house with electricity all day.

However, the natural gas or LPG powered generator would backup the solar panels and turn on to help charge the batteries if they are not charged enough (for instance, if it is cloudy for a very long time or at night).

It is possible to use grid electricity (power from the utility company) to help the solar power system to charge a small bank of batteries during the day if it is cloudy, and at night, your electricity could come directly from the utility company when electricity rates are cheaper. A DC (direct current) battery charger is required for this.

Converting Battery Power To 120 Volts AC For Appliances

If you want to use batteries to supply solar power directly to appliances, you cannot directly do this, you have to purchase an inverter, which is a device that converts 12 or 24 volts DC to 120 Volts AC which appliances use. You would then plug the appliances into the inverter.


Net Metering (Connecting Your Solar Power System To The Electricity Grid)

There is an alternative to storing energy produced my solar panels, which does not involve directly powering the household appliances. You can contact your power company and ask them for more information about net metering and their policies.

You would purchase a grid-tie inverter which the solar panels would supply DC (direct current) electricity to. A grid-tie inverter is a technology would convert that DC current into AC current (pure sine wave) and supply it to the electricity grid through a power meter.

In this case, the solar panels would be used to offset your power consumption by turning your power consumption meter backwards. When it is turned backwards, you are charged less for electricity.

For example. If you consumed 600 kWh (kilowatt-hours) after a month, and the solar panels generated 200 kWh during that month, then they turn the meter back from 600 kWh to 400 kWh.

Depending on the power company, you may or may not be paid a fair rate for the electricity generated by your solar panels, this is another reason you need to contact them and learn more about their policies.

Solar Panel And Solar Cell Efficiency

Difference Between Total Area Efficiency And Single Cell Efficiency

Total Area Efficiency is defined as the performance of an entire (normal) solar panel that consists of multiple solar cells and single cell efficiency is the performance of a single solar cell without a protective panel. Solar panels reflect some light away from solar cells, and they can even trap some heat, which worsens solar cell efficiency.

Another reason an entire solar panel is not as efficient as a single solar cell is because of electrical resistance encountered when electricity is trying to pass through the cells sequentially.

Total area efficiency is the most realistic efficiency rating.


Your Ability To Control Solar Panels And Electricity Demand

The amount of solar power your system generates is not controllable, but, they do generate more electricity during times of increased solar radiation intensity which is good because electricity demand also increases at that time.


Factors Affecting Cost

The cost of a solar power plant or a residential system is affected by a variety of factors, some of which include:

Importance of Solar Panel Efficiency

The lower the efficiency of a solar technology, the less electricity it will generate per square meter. Therefore, this means that less efficient solar panels are larger, per watt, than higher efficiency panels.

If a one square meter solar panel is 100% efficient, then it would have a peak power output of 1,000 watts. If it is 50% efficient, then the peak power output is 500 watts. Since the second panel is 50% efficient, it generates half as much electricity as the technology which is 100% efficient.

If you wanted to use panels which are 50% efficient to generate 2000 watts of solar power, then you would need 4 square metres of them, but they would only generate 2000 watts when it is sunny. Power output decreases with solar radiation.

There is the possibility that contractors may charge you more money to install larger solar panels, since they are more difficult to install, and take longer to install as well, in such cases, it would cost more to install lower efficiency panels, because they are larger.

Please weigh the total cost of buying and installing low efficiency panels with the cost of high-efficiency panels to determine which suits you best. Get a quote from contractor organizations.


Other Financial Information

Cost of Solar Power

In order to understand the following, you need to read this.

  • The cost of solar power (if photovoltaic technology is used) is an average of 13 cents/kWh in the United States. The amount of solar radiation varies significantly with location. More radiation normally translates to a lower cost per kWh.

Cost of solar power in comparison to conventional sources of electricity: Solar electricity from solar power plants (not rooftop solar setups) is more expensive than electricity from coal power plants at the moment.

However, the future is what is to come. It is important to consider the price trend that both sources of electricity have been following most consistently.

The trend is that the cost of coal goes up, and the cost of solar power goes down.

The extent to which the cost of coal inflates is also very important, and is more than significant enough to justify extensive R&D (Research and Development) of alternative sources of energy.

The cost of coal electricity will inevitably exceed the cost of solar power due to the laws of demand and supply as well as dwindling coal reserves, because coal is not renewable.

Residential

Residential solar setups are cheaper than utility supplied solar electricity for multiple reasons even though power plants can purchase the same solar panel technology at a lower price than most consumers due to quantity discounts), some of which include:

  • No step-up and step-down transformers or transmission equipment has to be purchased by the resident.
  • No wages nor salaries to pay.

How much do solar panels cost?: This is dependent on your power consumption. Solar panels themselves cost $2.50 to $5.50 USD per watt (so a 1,000 watt panel array costs $3,500 to $5,500 USD. You have to factor in both the dollars and cents/kWh. Do not practice approximation when comparing solar panel prices. A price difference of $0.50 per watt for a 1,000 watt panel is $500.

Please read the “Importance of Solar Panel Efficiency” section before continuing.

To determine the cost per watt of a solar panel using the price tag: price tag divided by wattage.

How much does it cost to install solar panels?: This varies, but it is common for solar setups to cost $7 to $9 per watt. You would then multiply that by the desired panel wattage, which is also difficult to determine, scroll up to learn more about that.

Residential Cost Of Solar Power Per kWh (April 2011)

Assumptions:

No Government Rebates.

Year: 365 Days.

Currency: USD.

Hours per year if half of each day was completely dark (during the day of course) with absolutely no sunlight like night-time (very conservative assumption): 2,190 hours. This would mean that during the day there would only be 6 hours of daylight instead of 11 to 13.

Cost of solar panel: $3 per watt of electricity generating capacity. The price of it would be $3,000 excluding installation because $3 per watt * 1,000 watts = $3,000.

Wattage of Entire Solar Setup: 1,000 watts.

Such a solar setup could generate 2,190 kWh of electricity per year (1,000 watts is 1,000 Wh for every sunny hour). Multiply that by the 30 year lifespan of the panels and the result is 65,700 kWh or 65.7 MWh.

To determine the cost per kWh of electricity generated by the panels over the 30 year period, divide the cost of the panels by the amount of electricity that they would generate after 30 years.

Divide $3,000 by 65,700 kWh and the result is $0.045/kWh or 4.5 cents per kWh. Remember that is unrealistic because the amount of sunlight is underestimated.

Solar panels still generate electricity when it is cloudy but it can be used as an example to help you to understand what you need to take into consideration to calculate the cost. My power consumption page will explain how I calculated what I did above.

The average number of hours of sunshine per year for your geographic location can help you to make your calculations. Remember that the average number of hours of sunshine does not include cloudy daytime hours in this example.

Full Cost Including Installation, No Rebates And Everything Else

Assuming the same weather that I described above, and using the same calculation method:

$7 per watt is a common cost of a grid-tie (connected to electricity grid to turn meter backwards without batteries) solar setup in the United States. $7 per watt total for a 1,000 watt solar panel array is a total cost of $7,000.

Therefore, the unsubsidized cost per kWh is 10.6 cents or $0.106 (this is equivalent to 6.6 pence, £0.066, which is 7.52 eurocents or €0.0752/kWh). If it was a 3 kW system that you wanted, the cost per kWh would still be 10.6 cents.

This is comparable to the cheapest conventional sources of electricity in the U.S such as coal. People pay $0.09 to $0.11/kWh on average for electricity in the United States for example [source], and much more in some other locations, especially those that utilize gasoline and diesel generators.

This cost includes everything.

The Cost Of Solar If The Government Paid 30% Of It

$4,900 or $4.90 per watt which is $0.074/kWh or 7.4 cents/kWh.


Solar Thermal Energy

Solar thermal power plants convert the thermal energy radiated by the sun into electricity or use it to provide heat using the following methods:

– Steam: The heat provided by the sun’s rays can be used to heat a boiler, which produces steam by boiling a fluid such as water or mineral oil (at a temperature of 400 °C), and the steam enters the steam admission section, and is passed over steam turbine blades by a high pressure nozzle, causing them to turn.

Next, they turn an alternator which converts mechanical energy into electrical energy. Concentrated sunlight may be used as a heat source for this type of generator by using motorized mirrors (heliostats) to focus a sunlight on the boiler.

– Stirling: A stirling engine is a hot air engine which utilizes a temperature difference between both sides (cylinders) to convert heat energy into mechanical energy, which is then converted into electrical energy by an alternator.

Concentrated sunlight may be used as a heat source for this type of generator by using motorized mirrors (heliostats) to focus a sunlight on the stirling engine.

– Thermoelectric: A thermoelectric device is a very compact, solid-state (non-mechanical), flat device which can generate electricity when heat is applied to one side of it. As heat flows from that side to the other side, where heat is dissipated with a radiator or a large heat sink, some of the heat is converted into electricity.

Concentrated sunlight may be used as a heat source for this type of generator by using motorized mirrors (heliostats) to focus a sunlight on the hot side of the thermoelectric module. The greater the temperature difference between the sides of the modules, the greater the power output.


Applications of Solar Technology

Refrigeration and Air Conditioning: Heat from the sun’s rays can be used to power heat powered refrigerators, such as absorption refrigerators. Photovoltaic panels (commonly known as solar panels) can be used to power the common type of air conditioner, which uses the vapour compression cycle to cool.

Water Heating: Solar water heaters normally heat water by using dull black copper tubing to absorb sunlight which then heats water as it passes through the tubing. Solar panels can also be used to generate electricity to power conventional electric water heaters.

Portable Electronics: Portable electronics such as cellphones and notebook computers are battery-powered, and it is common for their batteries to die at the worst times, these devices can be manufactured with solar cells printed on them to keep their batteries charged.

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