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Sun Stuff Energy provides basic information on how the most common alternative energy sources work. Contact us for further details, consultation, and free estimates for your home or business.

Solar Water Heaters | Solar Pool Heaters | Solar Electricty | Wind Electric System

Solar Hot Water Heaters

Solar water heating systems include storage tanks and solar collectors. There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don't.

Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In one-tank systems, the back-up heater is combined with the solar storage in one tank.

Solar water heating systems almost always require a backup system for cloudy days and times of increased demand. Conventional storage water heaters usually provide backup and may already be part of the solar system package.

Three types of solar collectors are used for residential applications:

  • Flat-plate collector

    Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors—typically used for solar pool heating—have a dark absorber plate, made of metal or polymer, without a cover or enclosure.

  • Integral collector-storage systems

    Also known as ICS or batch systems, they feature one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues on to the conventional backup water heater, providing a reliable source of hot water. They should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather.

  • Evacuated-tube solar collectors

    They feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin's coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications.

Illustration of an active, closed loop solar water heater. A large, flat panel called a flat plate collector is connected to a tank called a solar storage/backup water heater by two pipes. One of these pipes is runs through a cylindrical pump into the bottom of the tank, where it becomes a coil called a double-wall heat exchanger. This coil runs up through the tank and out again to the flat plate collector. Antifreeze fluid runs only through this collector loop. Two pipes run out the top of the water heater tank; one is a cold water supply into the tank, and the other sends hot water to the house.There are two types of active solar water heating systems:

  • Direct circulation systems

    Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes.

  • Indirect circulation systems

    Pumps circulate a non-freezing, heat-transfer fluid through the collectors and a heat exchanger. This heats the water that then flows into the home. They are popular in climates prone to freezing temperatures.

Passive solar water heating systems are typically less expensive than active systems, but they're usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems:

  • Integral collector-storage passive systems

    These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs.

  • Thermosyphon systems

    Illustration of a passive, batch solar water heater. Cold water enters a pipe and can either enter a solar storage/backup water heater tank or the batch collector, depending on which bypass valve is opened. If the valve to the batch collector is open, a vertical pipe (which also has a spigot drain valve for cold climates) carries the water up into the batch collector. The batch collector is a large box holding a tank and covered with a glaze that faces the sun. Water is heated in this tank, and another pipe takes the heated water from the batch collector into the solar storage/backup water heater, where it is then carried to the house.Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but contractors must pay careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems.

Solar water heating systems almost always require a backup system for cloudy days and times of increased demand. Conventional storage water heaters usually provide backup and may already be part of the solar system package.

A backup system may also be part of the solar collector, such as rooftop tanks with thermosyphon systems. Since an integral-collector storage system already stores hot water in addition to collecting solar heat, it may be packaged with a demand (tankless or instantaneous) water heater for backup.

 

 

 

Solar Swimming Pool Heaters

Most solar pool heating systems include the following:

  • A solar collector — the device through which pool water is circulated to be heated by the sun
  • A filter — removes debris before water is pumped through the collector
  • A pump — circulates water through the filter and collector and back to the pool
  • A flow control valve — automatic or manual device that diverts pool water through the solar collector.
Example of a solar pool heating system. This diagram shows the path pool water would travel as it goes through a solar pool heating system. The water exiting the pool goes through a strainer, then is pumped through a filter, through the collector, through a conventional pool heater (if you have one), and back into the pool. This system also includes a check valve, a flow control valve, and temperature sensors.
Example of a solar pool heating system.

Pool water is pumped through the filter and then through the solar collector(s), where it is heated before it is returned to the pool. In hot climates, the collector(s) can also be used to cool the pool during peak summer months by circulating the water through the collector(s) at night.

Some systems include sensors and an automatic or manual valve to divert water through the collector(s) when the collector temperature is sufficiently greater than the pool temperature. When the collector temperature is similar to the pool temperature, filtered water simply bypasses the collector(s) and is returned to the pool.

Solar pool collectors are made out of different materials. The type you'll need depends on your climate and how you intend to use the collector. If you'll only be using your pool when temperatures are above freezing, then you'll probably only need an unglazed collector system. Unglazed collectors don't include a glass covering (glazing). They are generally made of heavy-duty rubber or plastic treated with an ultraviolet (UV) light inhibitor to extend the life of the panels. Because of their inexpensive parts and simple design, unglazed collectors are usually less expensive than glazed collectors. These unglazed systems can even work for indoor pools in cold climates if the system is designed to drain back to the pool when not in use. Even if you have to shut the system down during cold weather, unglazed collectors may be more cost effective than installing a more expensive glazed collector system.

An illustration of a solar panel. A tube is at each end of the panel, and arrows show the flow going through one tube, across the panel, and out the end of the other tube, which is labeled the header/manifold.
Example of how a
solar collector works

Glazed collector systems are generally made of copper tubing on an aluminum plate with an iron-tempered glass covering, which increases their cost. In colder weather, glazed collector systems—with heat exchangers and transfer fluids—capture solar heat more efficiently than unglazed systems. Therefore, they can be used year-round in many climates. Glazed collectors also can be used to heat domestic hot water year-round.

Both glazed and unglazed collector systems should include freeze protection if they'll be used in colder conditions.

 

 

Solar Electricity

Although solar electricity producing devices have been around for over 50 years, solar electricity devices, often referred to as photovoltaics or PV, are still considered cutting edge technology. The promise of clean, cheap, and abundant electricity from the sun has been the dream of many scientists and businesses. As a result each year a number of discoveries and advances for this technology have been made.

Solar cells—the basic building blocks of a PV system—consist of semiconductor materials. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms. This phenomenon is called the "photoelectric effect." These free electrons then travel into a circuit built into the solar cell to form electrical current. Only sunlight of certain wavelengths will work efficiently to create electricity. PV systems can still produce electricity on cloudy days, but not as much as on a sunny day.

A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped (N-type) silicon on top of a thicker layer of boron-doped (P-type) silicon. An electrical field is created near the top surface of the cell where these two materials are in contact, called the P-N junction. When sunlight strikes the surface of a PV cell, this electrical field provides momentum and direction to light-stimulated electrons, resulting in a flow of current when the solar cell is connected to an electrical load

A diagram explaining how a PV cell generates electricity.
Figure 1. Diagram of a photovoltaic cell.

Regardless of size, a typical silicon PV cell produces about 0.5 – 0.6 volt DC under open-circuit, no-load conditions. The current (and power) output of a PV cell depends on its efficiency and size (surface area), and is proportional the intensity of sunlight striking the surface of the cell. For example, under peak sunlight conditions, a typical commercial PV cell with a surface area of 160 cm^2 (~25 in^2) will produce about 2 watts peak power. If the sunlight intensity were 40 percent of peak, this cell would produce about 0.8 watts.

Photovoltaic arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day.

Because of their modularity, PV systems can be designed to meet any electrical requirement, no matter how large or how small. You also can connect them to an electric distribution system (grid-connected), or they can stand alone (off-grid).

An illustration showing a residential grid-connected small solar electric or photovoltaic system. It shows two square-shaped solar panels, each containing nine smaller squares, on the roof of a house. You can see how the electric current travels from the solar panels to an inverter box. From the inverter box, the electric current travels to a meter box and then to an electricity transmission tower, referred to as the utility service. Inside the house, from the inverter box, you see the electric current powering two lights, a television, and a clothes washer and dryer.

Wind Electric System

Small wind electric systems are one of the most cost-effective, home-based renewable energy systems. These systems are also nonpolluting.

If a small wind electric system is right for you, it can do the following:This illustration shows the basic parts of a small wind electric system. It shows the wind turbine. The turbine features two, long, thin blades attached at one end. Next to the the blades is a rotor, which looks like a metal band next to the blades. The rotor's connected to a generator/alternator, a cylindrical-shaped device. A long, thin, triangular-shaped metal piece extends from the generator/alternator, with a tail at the end, which is shaped and placed much like the tail of one of those small wooden model planes. The turbine sits atop a tower, which is basically a long metal pole. The tower is connected beneath the generator/alternator.

  • Lower your electricity bills by 50–90%
  • Help you avoid the high costs of having utility power lines extended to a remote location
  • Help uninterruptible power supplies ride through extended utility outages.

Small wind electric systems can also be used for a variety of other applications, including water pumping on farms and ranches.

Wind is created by the unequal heating of the Earth's surface by the sun. Wind turbines convert the kinetic energy in wind into clean electricity.

When the wind spins the wind turbine's blades, a rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator. The manuf acturer can provide information on the maximum wind speed at which the turbine is designed to operate safely. Most turbines have automatic overspeed-governing systems to keep the rotor from spinning out of control in very high winds.

A small wind system can be connected to an electric distribution system (grid-connected) or it can stand alone (off-grid).

All information courtesy U.S. Department of Energy

 

 
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