How Does a Solar Water Heater Work?

Solar water heaters do three basic operations before the hot water comes out of your faucet:

1. Energy Collection: Sunlight, shortwave energy, is collected and converted to heat which is longwave energy. The solar collector is mounted on or near your home facing south. As the sunlight passes through the collector’s plastic or glass “glazing,” it strikes a metal or rubber absorbing the material. This material converts the sunlight into long wave heat, and the glazing prevents the heat from escaping much like a greenhouse. It is like leaving a car parked in the sun with its windows rolled up. The temperature inside a glazed solar collector on your roof can easily reach 300F when there is no heat transfer fluid flowing through it.

Because of their high performance, simplicity, and cost-effectiveness, the most common types of solar collectors used in solar water heaters are glazed flat plate collectors. A glazed flat plate collector consists of a shallow rectangular box with a transparent plastic or glass “window” covering a flat black plate or selective “Chrome” coating. The black plate is attached to a series of parallel tubes or one serpentine tube through which water or other heat transfer fluids pass.

2. Energy Transfer: Circulating fluids like water in an “Open Loop” or Propylene Glycol in a “Closed Loop” transfer the collected energy in the form of heat to a storage tank. Heat energy is transferred from the collector to the water storage tank. In some water heaters, hot fluid is pumped from the collector to the storage tank. The pump is powered by electricity that either comes from an electrical wall outlet or a small photovoltaic module located near the collector.

3. Energy Storage: Solar-heated water is stored in an insulated tank until you need it. Hot water is drawn off the tank when tap water is used, and cold make-up water enters at the bottom of the tank. If additional heat is needed, it is provided by electricity or fossil fuel energy by the conventional “backup” water-heating system.

Solar water heaters tend to have larger hot water storage capacity than conventional water heaters. This is because solar heat is available only during the day and sufficient hot water must be collected to meet evening and morning requirements. How well an active solar energy system performs depends on effective siting, system design, location, and installation. Solar thermal water heating systems, which use the sun’s energy rather than electricity or gas to heat water, can efficiently provide 50 to 90% of your hot water needs—without fuel cost or pollution and with minimal operation and maintenance expense.

What You Need To Go Solar

Southern Orientation

Since the sun rises in the East, crosses over the horizon on the South and sets in the West, you want your collector to face as much to True South on your roof as possible. This is especially true for space heating where you need to be within 15 degrees of True South. Click Here: Home power true south article.

Up to 45 degrees East or West of true South has a very little effect on year-round domestic water heating. While less desirable, a West or even an East facing water heating system can work well, especially with an additional collector. Orientations over 45 degrees, such as a home with a North-South ridge line can tilt the collectors South with a SolarRoofs.com tilt kit. Click here to learn about optional tilt kits.

While most collectors are mounted on the roof, many have been mounted on the ground, or on an awning on the side of the house. Vertical mounting of collectors on the South roof is great for space heating. Naturally, it is important that there not be any shading where the collectors will go!

You Need Space for your Solar Collectors

SolarRoofs.com’s Skyline® collectors are rugged and powerful yet lightweight. These collectors are easy to carry by one person and are much safer to get on the roof to install. Both the 10-01 and 20-01 collectors are available in architectural colors and have an attractive appearance on the roof. No soldering is required to install the collector(s).

The Skyline® 10-01 collector weighs 19 pounds and measures 6′ long x 20″ wide by 3″ thick.

The feed and return are at one end. They have a 2″ space between them and up to (4) 10-01 collectors can be stacked one above the other or up to twelve in a stacked & side x side configuration.

The Skyline® 20-01 collector weighs 38 pounds and measures 12′ long x 20″ wide by 3″ thick.

The feed and return are at one end. They have a 2″ space between them and up to (4) 20-01 collectors can be stacked one above the other or up to (8) in a stacked & side x side configuration. 20-01 collectors have custom options: feed through and turnaround collectors extending up to 60′ with one feed and return. These collectors are ideal for commercial applications.

You need a Good Path For Solar Lines from Collectors to Solar Storage Tank

You need a good “path” for your two solar lines and wires to go from your tank to your South facing roof. It is desirable that this “path” is under 40 feet (one way), but up to 80 feet (if well insulated) is OK. You will be running two 1/2″ outside diameter copper tubes with a minimum of 1/2″ thick high-temperature insulation. You will also be running at least one wire set on the outside of the insulation for either power from a PV panel to the pump and/or a sensor wire for a differential controller. Horizontal lines need to be supported every six feet. For PV pumped Open Loop systems 1 and 3, a second wire set may be needed for a freeze snap switch, The Installation Manuals have good guidance on running solar lines. You will need a large enough storage tank or enough room for an added solar tank.

You need to know the right System Type for your area

Open Loop Skyline1, Skyline2 or Skyline3 Systems

With these systems, the solar loop is open to water pressure. They are excellent where there is anywhere from no freeze potential (tropical) to where there is light freeze potential (temperate) when used with light freeze protection options. Tropical Climate Systems are good for areas like the Florida Keys, Caribbean, Hawaii and all other areas with Absolutely No Freeze conditions or temperatures below 40F. Temperate Climate Systems include light freeze protection options and are good for Central Florida, Southern California and other areas where the temperature rarely goes down to 30F with absolutely No Hard Freeze. These systems must be drained and any remaining water in the collector lines blown out with air if a hard freeze may occur.

Closed Loop Skyline4 and Skyline5 Systems

For Freeze Climates, the solar loop is separated from water pressure by a storage tank with an internal heat exchanger. These systems are not subject to freeze damage when properly installed. These systems are also used in areas where bad water quality may plug up or destroy the copper tubing in the collectors.

Sizing Your System

Selecting the appropriate solar energy system depends on factors such as the site, design, and heating needs of your house. The local climate, the type and efficiency of the collector(s), and the collector area determine how much heat a solar heating system can provide. It is usually most economical to design an active system to provide 40%–80% of the home’s heating needs. A small system providing as little as 30% of your hot water can be very efficient and cost effective! If the budget is tight, consider getting a smaller system. More panels can be added later. The important thing is to take that important first step to go solar!

General Sizing Guidelines

Skyline1, 2 and 3 Systems for 75 to 90% coverage in warmer, sunny areas, use two 10-01 collectors or one 20-01 collector (20 square feet) for each two to three people in the household. For example, a family of 4 should have four 10-01 collectors or two 20-01 collectors (40 square feet).

Skyline4 and 5 for 60 to 70% coverage in areas subject to hard freeze and a lot of clouds, start with four 10-01 or two 20-01 collectors for the first two people and then two 10-01 collectors or one 20-01 collector for every additional two people. For example, a family of 4 should have six 10-01 collectors or three 20-01 collectors (60 square feet).

Storage

TROPICAL and TEMPERATE SYSTEMS may allow you to use your existing electric water heater for open-loop systems 1, 2 and 3, or you can add a low-cost water heater for solar storage to your existing water heater. You need at least 1 gallon of storage for each square foot of collector area. It is desirable that your storage tank be at least 50 gallons of storage for up to 40 square feet of collector area, although a 40-gallon water heater can work well with up to 30 square feet of collector area. Generally, the larger the water heater the better, up to 2.5 gallons per square foot of collector area in sunny areas.

FREEZE PROTECTED SYSTEMS 4 and 5 use an excellent Rheem / Rudd or Richmond (all the same manufacturer) 80 Gallon Storage tank with a very efficient 120 foot “wrap around” heat exchanger. For a closed-loop system using an existing tank or added standard tank, an optional system 4 “POWER ROD” or”DRAIN BACK” external heat exchanger is available. They use a second pump for the domestic water loop and a tank top “Quick Connect,” to the storage tank.

Building Codes and Regulations for Solar Heating Systems

Before installing a solar energy system, you should investigate local building codes, zoning ordinances, and subdivision covenants, as well as any special regulations pertaining to the site. You will probably need a building permit to install a solar energy system onto an existing building. Due to the light weight of Skyline® systems, are not usually any structural issues.

Maintaining Your Solar Water Heating System

Very little maintenance is needed for Skyline® systems and collectors. When there is no rain for a long period of time it is good to rinse your collectors with water to get the dust off. Please see Operations and Maintenance manuals. Most solar water heaters are automatically covered under your homeowner’s insurance policy. However, damage from freezing is generally not. Contact your insurance provider to find out the policy. Even if your provider will cover your system, it is best to inform them in writing that you own a new system.

How Does a Solar Water Heater Work?

Solar water heaters do three basic operations before the hot water comes out of your faucet:

1. Energy Collection: Sunlight, shortwave energy, is collected and converted to heat which is longwave energy. The solar collector is mounted on or near your home facing south. As the sunlight passes through the collector’s plastic or glass “glazing,” it strikes a metal or rubber absorbing the material. This material converts the sunlight into long wave heat, and the glazing prevents the heat from escaping much like a greenhouse. It is like leaving a car parked in the sun with its windows rolled up. The temperature inside a glazed solar collector on your roof can easily reach 300F when there is no heat transfer fluid flowing through it.

Because of their high performance, simplicity, and cost-effectiveness, the most common types of solar collectors used in solar water heaters are glazed flat plate collectors. A glazed flat plate collector consists of a shallow rectangular box with a transparent plastic or glass “window” covering a flat black plate or selective “Chrome” coating. The black plate is attached to a series of parallel tubes or one serpentine tube through which water or other heat transfer fluids pass.

2. Energy Transfer: Circulating fluids like water in an “Open Loop” or Propylene Glycol in a “Closed Loop” transfer the collected energy in the form of heat to a storage tank. Heat energy is transferred from the collector to the water storage tank. In some water heaters, hot fluid is pumped from the collector to the storage tank. The pump is powered by electricity that either comes from an electrical wall outlet or a small photovoltaic module located near the collector.

3. Energy Storage: Solar-heated water is stored in an insulated tank until you need it. Hot water is drawn off the tank when tap water is used, and cold make-up water enters at the bottom of the tank. If additional heat is needed, it is provided by electricity or fossil fuel energy by the conventional “backup” water-heating system.

Solar water heaters tend to have larger hot water storage capacity than conventional water heaters. This is because solar heat is available only during the day and sufficient hot water must be collected to meet evening and morning requirements. How well an active solar energy system performs depends on effective siting, system design, location, and installation. Solar thermal water heating systems, which use the sun’s energy rather than electricity or gas to heat water, can efficiently provide 50 to 90% of your hot water needs—without fuel cost or pollution and with minimal operation and maintenance expense.

What You Need To Go Solar

Southern Orientation

Since the sun rises in the East, crosses over the horizon on the South and sets in the West, you want your collector to face as much to True South on your roof as possible. This is especially true for space heating where you need to be within 15 degrees of True South. Click Here: Home power true south article.

Up to 45 degrees East or West of true South has a very little effect on year-round domestic water heating. While less desirable, a West or even an East facing water heating system can work well, especially with an additional collector. Orientations over 45 degrees, such as a home with a North-South ridge line can tilt the collectors South with a SolarRoofs.com tilt kit. Click here to learn about optional tilt kits.

While most collectors are mounted on the roof, many have been mounted on the ground, or on an awning on the side of the house. Vertical mounting of collectors on the South roof is great for space heating. Naturally, it is important that there not be any shading where the collectors will go!

You Need Space for your Solar Collectors

SolarRoofs.com’s Skyline® collectors are rugged and powerful yet lightweight. These collectors are easy to carry by one person and are much safer to get on the roof to install. Both the 10-01 and 20-01 collectors are available in architectural colors and have an attractive appearance on the roof. No soldering is required to install the collector(s).

The Skyline® 10-01 collector weighs 19 pounds and measures 6′ long x 20″ wide by 3″ thick.

The feed and return are at one end. They have a 2″ space between them and up to (4) 10-01 collectors can be stacked one above the other or up to twelve in a stacked & side x side configuration.

The Skyline® 20-01 collector weighs 38 pounds and measures 12′ long x 20″ wide by 3″ thick.

The feed and return are at one end. They have a 2″ space between them and up to (4) 20-01 collectors can be stacked one above the other or up to (8) in a stacked & side x side configuration. 20-01 collectors have custom options: feed through and turnaround collectors extending up to 60′ with one feed and return. These collectors are ideal for commercial applications.

You need a Good Path For Solar Lines from Collectors to Solar Storage Tank

You need a good “path” for your two solar lines and wires to go from your tank to your South facing roof. It is desirable that this “path” is under 40 feet (one way), but up to 80 feet (if well insulated) is OK. You will be running two 1/2″ outside diameter copper tubes with a minimum of 1/2″ thick high-temperature insulation. You will also be running at least one wire set on the outside of the insulation for either power from a PV panel to the pump and/or a sensor wire for a differential controller. Horizontal lines need to be supported every six feet. For PV pumped Open Loop systems 1 and 3, a second wire set may be needed for a freeze snap switch, The Installation Manuals have good guidance on running solar lines. You will need a large enough storage tank or enough room for an added solar tank.

You need to know the right System Type for your area

Open Loop Skyline1, Skyline2 or Skyline3 Systems

With these systems, the solar loop is open to water pressure. They are excellent where there is anywhere from no freeze potential (tropical) to where there is light freeze potential (temperate) when used with light freeze protection options. Tropical Climate Systems are good for areas like the Florida Keys, Caribbean, Hawaii and all other areas with Absolutely No Freeze conditions or temperatures below 40F. Temperate Climate Systems include light freeze protection options and are good for Central Florida, Southern California and other areas where the temperature rarely goes down to 30F with absolutely No Hard Freeze. These systems must be drained and any remaining water in the collector lines blown out with air if a hard freeze may occur.

Closed Loop Skyline4 and Skyline5 Systems

For Freeze Climates, the solar loop is separated from water pressure by a storage tank with an internal heat exchanger. These systems are not subject to freeze damage when properly installed. These systems are also used in areas where bad water quality may plug up or destroy the copper tubing in the collectors.

Sizing Your System

Selecting the appropriate solar energy system depends on factors such as the site, design, and heating needs of your house. The local climate, the type and efficiency of the collector(s), and the collector area determine how much heat a solar heating system can provide. It is usually most economical to design an active system to provide 40%–80% of the home’s heating needs. A small system providing as little as 30% of your hot water can be very efficient and cost effective! If the budget is tight, consider getting a smaller system. More panels can be added later. The important thing is to take that important first step to go solar!

General Sizing Guidelines

Skyline1, 2 and 3 Systems for 75 to 90% coverage in warmer, sunny areas, use two 10-01 collectors or one 20-01 collector (20 square feet) for each two to three people in the household. For example, a family of 4 should have four 10-01 collectors or two 20-01 collectors (40 square feet).

Skyline4 and 5 for 60 to 70% coverage in areas subject to hard freeze and a lot of clouds, start with four 10-01 or two 20-01 collectors for the first two people and then two 10-01 collectors or one 20-01 collector for every additional two people. For example, a family of 4 should have six 10-01 collectors or three 20-01 collectors (60 square feet).

Storage

TROPICAL and TEMPERATE SYSTEMS may allow you to use your existing electric water heater for open-loop systems 1, 2 and 3, or you can add a low-cost water heater for solar storage to your existing water heater. You need at least 1 gallon of storage for each square foot of collector area. It is desirable that your storage tank be at least 50 gallons of storage for up to 40 square feet of collector area, although a 40-gallon water heater can work well with up to 30 square feet of collector area. Generally, the larger the water heater the better, up to 2.5 gallons per square foot of collector area in sunny areas.

FREEZE PROTECTED SYSTEMS 4 and 5 use an excellent Rheem / Rudd or Richmond (all the same manufacturer) 80 Gallon Storage tank with a very efficient 120 foot “wrap around” heat exchanger. For a closed-loop system using an existing tank or added standard tank, an optional system 4 “POWER ROD” or”DRAIN BACK” external heat exchanger is available. They use a second pump for the domestic water loop and a tank top “Quick Connect,” to the storage tank.

Building Codes and Regulations for Solar Heating Systems

Before installing a solar energy system, you should investigate local building codes, zoning ordinances, and subdivision covenants, as well as any special regulations pertaining to the site. You will probably need a building permit to install a solar energy system onto an existing building. Due to the light weight of Skyline® systems, are not usually any structural issues.

Maintaining Your Solar Water Heating System

Very little maintenance is needed for Skyline® systems and collectors. When there is no rain for a long period of time it is good to rinse your collectors with water to get the dust off. Please see Operations and Maintenance manuals. Most solar water heaters are automatically covered under your homeowner’s insurance policy. However, damage from freezing is generally not. Contact your insurance provider to find out the policy. Even if your provider will cover your system, it is best to inform them in writing that you own a new system.