Solar water heaters can be used to heat swimming pools and spas.

In a solar pool-heating system, the existing pool filtration system pumps pool water through the solar collector, and the collected heat is transferred directly to the pool water. Solar pool-heating collectors operate just slightly warmer than the surrounding air temperature and typically use inexpensive, unglazed, low-temperature collectors made from specially formulated plastic materials. Glazed (glass-covered) solar collectors are not typically used in pool-heating applications, except for indoor pools, hot tubs, or spas in colder climates. In some cases, unglazed copper or copper-aluminum solar collectors are used.

In residential applications where the goal is usually to extend the swimming season into spring and fall, heating a swimming pool with solar energy requires a solar collector that is 50% to 100% of the surface area of the pool. In general, adding more square footage lengthens the swimming season and allows owners to use the pool in colder weather. A pool cover or blanket significantly reduces heat loss in a cost-effective manner and helps maintain warm temperatures for long periods.

A solar pool-heating system costs between $2,000 and $10,000 to buy and install, depending on size. Costs run between $7 – $12 per square foot depending on system design and collection type. This provides a return on investment between 1.5 and 7 years, depending on the cost of the auxiliary energy being displaced.

Maintenance of solar pool-heating systems is minimal. The systems are pre-engineered and can be sized for any pool by simply adding additional solar panels to obtain an adequate solar collector area.

The only moving part on a solar pool-heating system is the diverting valve. This valve controls when the water circulates through the collector loop. If the collector temperature is sufficiently higher than the temperature of the water in the pool, water is diverted from the filter systems through the collector loop. The water bypasses the solar collectors during the night or cloudy periods. Some smaller systems are operated manually or with timers. Larger systems are operated by electronic sensors and controls.

Green energy is the newest movement in for home owners, and solar energy is one of the more popular options.  Through the use of the various types of solar energy, homes and be heated and provided with electricity without causing any damage to the environment. For modern applications, solar energy can be used for several different reasons.  Those are;

• Heating
• Cooling
• Water Heating
• Light
• Electricity Generation

Each of these, aside from generating electricity, comes in two distinct forms, active and passive.  The difference is simple, active solar energy require extensive interference from technology in order to harness solar power, while passive gets solar energy without the use of any technology.

The sun has long been considered to be one of the greatest natural energy sources known to man.  Now, through both careful planning and creative technology, you can harness solar energy to help deplete your need for the use of fossil fuels.  Here is a breakdown of the different types of solar energy.

Heating

The sun naturally gives off the heat that makes this planet habitable, so why not use it to heat things like your home, office, or even your car.  Both active and passive solar heating can easily be achieved.  Passive solar heating is by far the better of the two options.  It involve the use of large windows appropriately oriented to get maximum exposure to the sun.  These large windows slightly focus the sun’s rays, slightly magnifying them, heating the inside of the structure.  For those that live in the northern hemisphere, your large windows should face south.  Those in the southern hemisphere, north.  These windows should be double paned and appropriately size to maximize sun exposure.  They should also not be blocked by vegetation or landscaping, providing them with a constant exposure to the sun.

There are two types of active solar heating (solar heating achieved through the use of technology).  Those types are liquid or air based heating system.  Liquid systems use the solar power to heat water, typically through tiles and boards on the roof, then store the hot water in a storage tank.  This water is then either used to fuel a blower, distributing hot air through the home, or the hot water is run through the different structures of the home, like the floors and walls.  Air systems heat air using solar power, then pump it through the home just like a furnace would.

Cooling

Passive solar cooling is much simpler than it sounds.  It involves orienting the home so that it can naturally take advantage of things like wind flow, shade, and the sun’s natural arc.  Consider it to be the opposite to passive solar heating, at least in theory.  Setting up windows in your home to promote a good wind flow in your home will help keep it cool in summer, and having the appropriate windows size will help to reduce the amount of solar heat generated.  Adequate ventilation will keep a nice breeze flowing in your home, keeping you cooler in the hotter months.  You can also incorporate vegetation and other types of landscaping into passive cooling.  A large shade tree will help keep the sun’s rays off your home, or planting a thick climbing vine, like ivy, can help to reduce the amount of heat your home takes on from the sun.

Active solar cooling comes in three majorly used forms.  While many of these are not commonly used in the home quite yet, they have proven quite successful in larger buildings and office complexes.  Solar absorption is an air conditioner fuels by heated liquids.  When the liquids are heated by the sun’s energy, they separate from other substances, starting the air conditioner.  A desiccant system works differently than your traditional air conditioner.  If forces the air from a building though a filtering system that removes humidity from the air, making the building feel cooler.  Then, solar energy is used to dry out the filtration system.

The final can be considered a form of active solar cooling, but it is more a form of electricity generation.  It is included with active solar cooling because it makes perfect sense.  Photovoltaic cooling uses solar panels to generate electricity for a standard air conditioner.  Though there may be some conversion of power involved, a solar panel can more than adequately provide enough energy to to fuel a standard central air unit.  Since you primarily run your air conditioner on those hot, and sunny, summer days, why not use it to your advantage.  Setting up a system like this can save you a fortune on your summer heating bills.

Water Heating

We use a lot of water in our homes, but for cleaning and bathing purposes, we use mostly hot water.  Unfortunately, passive solar energy will not heat water enough for common application in the home.  Hot water much reach a certain temperature before it can be used to clean.

To get around this, there are two active solar water heat

ing systems, direct and indirect.  More commonly referred to as an open loop system, direct water heating systems push the water through solar heating panels to raise it to a certain temperature.  Then, the water is stored in an insulated collection tank, which serves as your hot water reserve.  It is pumped from there to the faucets of your home.  The water is continuously moved through the solar panels, constantly heating the water supply.

The closed loop system (indirect) is highly similar, but instead of pumping the water itself through the solar panels, the pumps a heating fluid.  Once this fluid is hot, it is pumped through the water supply, heating it in a similar fashion to a pot full of water on the stove.  From the hot water reserve, it is distributed to your home.

Light

This may seem like common sense, but creating a home designed to function off of passive solar energy is more complex than you would think.  It can involve several architectural changes and the possibility for a complete adaptation of your living space.  Passive solar lighting involves the use of large windows and sun lights to allow natural light in the entire time the sun is up, eliminating the need to turn on a single light during the daytime.  Having several windows that face south and sun lights (windows in the ceiling) are good starts, but you must also keep these free from obstructions.  You will also need to consider the natural arc of your day.  You wake up at sunrise, and go to sleep at sunset.  You will use your kitchen several times a day, and you will primarily use your living room in the evening.  So, since the sun moves from east to west, your bedroom should be on the east side of your home (first light during the day, completely dark by bedtime), the kitchen should be on the south side of your home (constant light throughout the day, should be on the north side for those in the southern hemisphere), and you living room should be on the west side of the home, so it will be able to harness the evening sun for light.  Using passive solar lighting can really add a new dynamic to your home.

Active solar lighting comes in two types of solar energy, either through electricity generation of photovoltaic lighting.  Most homes will need a complex energy generation system to light an entire home, but this type of system would be used to provide your entire home with electricity.  Photovoltaic lighting is most commonly used on the outside of the home.  These lights create enough energy to run that individual light through smaller photo-reactive electric semiconductors.  These semiconductors produce small amount of electricity when exposed to sunlight.  This energy is stored in the light until it gets dark, when the light will automatically turn on.  These are commonly used to light gardens, walkways, driveways, and various architectural structures.

Electricity Generation

This is what most people will think of when you mention any type of solar energy.  It is the use of technology to turn solar energy into usable electricity, which can then power anything you want to in the home.  This is thanks to photovoltaics.  Certain substances can convert solar energy into electricity, and placing several panels made of these photo-reactive substances can be used to generate a substantial amount of electricity.  Now how does this work in the home.

To start, your home will stay hooked to the grid, that way you will never go without power.  Solar panels, made of these photovoltaic material, are installed on your roof, typically facing south to gather the most sun light.  When solar energy hits these panels , is generates electricity, which then flows through a converter to change it from a DC current to an AC current.  This energy is then used first to power your home, or, with certain systems, it can be stored for future use.  One of the bigger advantages is that energy you don’t use can back flow through your connection to the power company.  This provide the power company with additional energy, and pushes your meter back, lowering your bill when you’re not using your stores of solar power.

Electricity generation can be used to only power specific appliances as well.  This is a good gradual step into green energy.  Photo-reactive solar panels are used to power individual large appliances, eliminating their need to be attached to the grid, lowering your energy bill.  This can be set up to work on things like electric stoves, washers, dryers, air conditioners, or a number of large appliances found in the home.  Imagine eliminating your air conditioner from your electric bill during those hot summer months.

Here’s a look at some things we can expect in the future from solar technologies.

All our buildings will feature energy-efficient design, construction, and materials as well as renewable energy technologies. In effect, each building will both conserve energy and produce its own supply, to be one of a new generation of cost-effective “zero-energy buildings” that have no net annual need for nonrenewable energy.

In photovoltaic research and development, there will be more breakthroughs in new materials, cell designs, and novel approaches to product development. In a solar future, your mode of transportation—and even the clothes you wear—could produce clean, safe electric power.

With today’s technology roadmaps to lead the way, concentrating solar power will be fully competitive with conventional power-generating technologies within a decade. Concentrating solar power, or solar thermal electricity, could harness enough of the sun’s energy to provide large-scale, domestically secure, and environmentally friendly electricity, especially in the southwestern United States.

The enormous solar power potential of the Southwest—comparable in scale to the huge hydropower resource of the Northwest—will be realized. A desert area 10 miles by 15 miles could provide 20,000 megawatts of power, and the electricity needs of the entire United States could theoretically be met by a photovoltaic array within an area 100 miles on a side.

Within 10 years, photovoltaic power will be competitive in price with traditional sources of electricity.

Solar electricity will be used in an electrolysis process that separates the hydrogen and oxygen in water so the hydrogen can be used in fuel cells for transportation and in buildings.

Just as solar energy can heat the water for a building, it can also heat and cool the air.

Space Heating

A solar space-heating system can consist of a passive system, an active system, or a combination of both. Passive systems are typically less costly and less complex than active systems. However, when retrofitting a building, active systems might be the only option for obtaining solar energy.

Passive Solar Space Heating

Passive solar space heating takes advantage of warmth from the sun through design features, such as large south-facing windows, and materials in the floors or walls that absorb warmth during the day and release that warmth at night when it is needed most. A sunspace or greenhouse is a good example of a passive system for solar space heating.

Passive solar design systems usually have one of three designs:

• Direct gain (the simplest system) stores and slowly releases heat energy collected from the sun shining directly into the building and warming materials such as tile or concrete. Care must be taken to avoid overheating the space.
• Indirect gain (similar to direct gain) uses materials that hold, store, and release heat; the material is located between the sun and living space (typically the wall).
• Isolated gain collects solar energy remote from the location of the primary living area. For example, a sunroom attached to a house collects warmer air that flows naturally to the rest of the house.

For more information about passive solar space heating, visit the EERE Passive Solar Heating, Cooling, and Daylighting page.

Active Solar Space Heating

Active solar space-heating systems consist of collectors that collect and absorb solar radiation combined with electric fans or pumps to transfer and distribute that solar heat. Active systems also generally have an energy-storage system to provide heat when the sun is not shining. The two basic types of active solar space-heating systems use either liquid or air as the heat-transfer medium in their solar energy collectors.

Liquid-based systems heat water or an antifreeze solution in a hydronic collector. Air-based systems heat air in an air collector. Air-based solar heating systems usually employ an air-to-water heat exchanger to supply heat to the domestic hot water system, making the system useful in the summertime. Both of these systems collect and absorb solar radiation, then transfer the solar heat directly to the interior space or to a storage system, from which the heat is distributed. An auxiliary or backup system provides heat when storage is discharged. Liquid systems are more often used when storage is included.

Here is a summary of the many different types of active solar space-heating systems:

Medium-temperature solar collectors are generally used for solar space heating. Solar space heating systems operate in much the same way as indirect solar water-heating systems, but they have a larger collector area, larger storage units, and more complex control systems. They are also usually configured to provide solar water heating and typically provide 30% to 70% of the residential heating, or combined heating and hot water, requirements. Active solar space-heating systems require more sophisticated design, installation, and maintenance techniques.

• A very economical, but specialized space heating system is based upon use of transpired air collectors, mounted as an exterior cladding on a south-facing wall. These systems are used for ventilation preheating. This system heats only outdoor air. These collectors are unglazed, and a blower or fan is used to draw air through perforations in the wall to deliver ventilation air into the building. Solar ventilation air preheating systems are generally used in commercial and industrial applications that require large quantities of ventilation air, including: a) buildings that require much outdoor ventilation, such as warehouses, large manufacturing plants, and airplane maintenance hangars; b) crop drying; and c) pre-heatingof boiler combustion air.

Space Cooling

Cooling and refrigeration can be accomplished using thermally activated cooling systems (TACS) driven by solar energy. These systems can provide year-round utilization of collected solar heat, thereby significantly increasing the cost effectiveness and energy contribution of solar installations. These systems are sized to provide 30% to 60% of building cooling requirements using solar, with the remainder usually dependent on TACS fueled by natural gas. The TACS available for solar-driven cooling include absorption systems and desiccant systems. Generally, solar cooling is not used because of the high initial costs of TACS and the solar fields needed to drive them.

• Solar absorption systems use the thermal energy from a solar collector to separate a binary mixture of an absorbent and a refrigerant fluid. The refrigerant is condensed, throttled, and evaporated to yield a cooling effect, which is then re-absorbed to continue the cycle. Double-effect absorption systems (which use the heat twice in series) are about twice as efficient as single-effect systems, but require significantly higher input temperatures. Because of the high temperature requirements of absorption cooling systems, evacuated-tube or concentrating collectors are typically used.
• Solar desiccant systems use thermal energy from the solar collector to regenerate dessicants that dry ambient air; they then use that dry air in indirect and/or direct evaporative stages to provide cooled air to the load. The solar heat is used to regenerate the desiccant, driving off the absorbed water. Some systems use flat-plate collectors at intermediate temperatures.

The word solar stems from the Roman word for the god of the sun, Sol.  Therefore, the word solar refers to the Sun and “solar power” is power from the Sun.

When we say something is solar powered, we mean that the energy it uses for power came directly from solar energy or sunlight energy.  The sun provides Earth with 2 major forms of energy, heat and light.  Some solar powered systems utilize the heat energy for heating while others transform the light energy into electrical energy (electricity).

There are many practical applications for solar power that are in use today.  Passive solar home designs utilize heat energy.  By slanting windows in a house and facing them to the south you can control the heat energy that enters the house.  During the winter when the Sun is low in the sky it shines into the window to warm and illuminate the house.  During the summer when the Sun is high in the sky the slant of the windows keeps the sunshine out so that the house stays cooler.

There are vehicles that run on solar power.  Some have PV panels as a direct power source that convert light energy into electricity to power their motors.  Since those cars will not run when the sun is not available it is more practical to have a car powered by batteries that can be recharged with solar energy.

In countries and locations where traditional power sources are not available it is more economical to power a house with solar energy.  To these people, solar is not an alternative energy; it is their primary energy source.

The Law of Conservation of Energy:

• Energy can only change from one form to another.
• Energy can not be created or destroyed.

Solar Energy is the energy from the Sun.  The Sun is a big ball of heat and light resulting from nuclear fusion at its core.  The nuclear reaction releases energy that travels outward to the surface of the Sun.  Along the way to the surface the energy transforms so that by the time it is released it is primarily light energy.  Sunlight.  The two major types of solar energy that make it to Earth are heat and light.

Solar energy is often called “alternative energy” to fossil fuel energy sources such as oil and coal.

One example of our use of solar heat energy is for water heating systems.  A solar panel is used to collect heat.  The heat is transferred to pipes inside the solar panel and water is heated as it passes through the pipes.  The hot water, heated by the Sun, can then be used for showers, cleaning, or heating your home.

We also use solar thermal energy through passive solar designs.  Windows or skylights in your home can be designed to face the Sun so that they let heat into the house, keeping you warmer in the winter.

The light energy from the Sun can be transformed into electrical energy and used immediately or stored in batteries. Photovoltaic (PV) panels are the devices that convert light energy into electrical energy.

Energy changes from one Form to Another.

Let’s look at a solar powered vehicle that runs on electricity directly from solar energy as a simple example in the transformation of energy from one form to another.

• Sunlight hits the PV panel and the panel transforms the light energy into electrical energy.
• The electrical energy (electricity) passes through the wire circuit to the motor.
• The motor transforms the electrical energy into mechanical energy to turn the drive shaft which turns the wheels.
• The wheels rotate on the ground to move the vehicle transforming mechanical energy into vehicle motion (kinetic energy).

Solar Vehicle Ideal Energy Chain:

Light Energy >> Electrical Energy >> Mechanical Energy >> Kinetic Energy

Energy transformation is not perfect…..

The above case is ideal because not all systems are perfect and in reality there will be losses of energy from our system.

In a simplified view of this case some losses will be from:

• friction of electrons passing through the wires;  this is released as heat energy.
• friction of the drive shaft or wheels on the ground;  this is released as either heat or sound energy.

Even with these losses the law of conservation of energy still holds.  The amount of energy into a system will always equal the amount of energy out of a system.