Solar Space Air Heating Systems for your home: collectors, size, location, technology

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Solar Heating & House Air and Space Heating basics

Solar space/air heating is a major application of solar energy. The others are solar water heating systems and solar PV systems for electricity production.

Solar space heating comprises the following mains systems:

- direct and simple home air heating
- solar heating with forced air systems
- solar heating integrated with the home's radiators
- solar heating integrated in in-slab heat

For more details on these systems, see: Solar Heating and Air Forced Systems, Radiators and Radiant Floor

Type of collectors used on solar space heating

There are three main types of collectors: flat-plate, evacuated-tube, and concentrating collectors. Fat-plate collectors are the most common type, and comprises two big sub-types: air and liquid collectors.

Air flat-plate collectors are typically used for space heating.
Liquid flat-plate collectors are used both for space heating and solar water-heating.

Typical solar air collector
Image credit: EERE

If you just want to install a space heating system and if your climate justifies it (if it has a cold-long winter), the air flat-plate type collectors is a possibility. If you want to install both a space heating and a water-heating system, then liquid flat-plate collectors are a better choice.

Note:
A water-heating system application based on air heating collectors demand an air-to-water heat exchanger – which turns the system less efficient than liquid collectors. And demand also a reasonable investment in storage equipment, which makes the solution less interesting.

Elements of solar space heating systems

Basically, solar space-heating systems involve:

1) collectors that absorb solar radiation
2) an energy-storage element: Most liquid solar space heating systems use a large water tank to store heat. Systems based on air flat-plate collectors can also use rocks or other heat storage mediums. The goal of storage systems are obvious: using the stored heat during the non-sunny parts of the day.
3) electric fans / pumps to driven solar heat
4) a forced air system, or a set of radiators, or floor or ceiling radiant hydronic systems...

Most solar space heating systems are integrated ones: they may produce both hot water for domestic uses and space heating.

Solar space heating technologies

Most solar space heating systems operate much like solar water-heating systems, but they demand a larger collectors surface, and also larger storage units and more complex control systems.

The collectors can work on 1) liquid-based systems or 2) air-based systems. Liquid-based systems use hydronic collectors: they heat water or an antifreeze solution in them. Air-based systems use air collectors: they heat air in them...

Availability

Space heating through solar collectors and complementary hardware is a well-developed technology. There are many manufacturers on a national basis for this type of solar technology.

Combined hot water and space heating systems

Most of the solar heating systems are configured to provide both solar water heating and a part (40-80%) of the home space heating needs. That's often the most advantageous solution.

Costs and Payback

See Costs and Payback of Solar Space Heating.

Sizing a solar space heating system for your house

When sizing a solar space heating system do not base the size and the number of collectors on the worst heating conditions. The system would become oversized for most of the year, and too costly. You can base it on the average heat load of the house during the heating season: in this case the system will provide enough heat during most of the year though not in some colder days, when it would be necessary an auxiliary heating system.

A formula commonly used in the calculation of the needed number of collectors is:
Average heat load / collector heat output = number of collectors needed.

The storage system is typically sized to 1.5 gallons of storage for each square foot of collector area.

Location of the solar collectors

Collectors should have a southern orientation (or a northern one, in Southern Hemisphere countries). The goal is to align the collectors perpendicularly to the sun's rays in the heating season (when the best performance is needed). A reference usually used as the optimal position is the latitude of the place plus 15 degrees (you may use the site Time and date.com to know your latitude).

Make sure that trees, buildings or other landscape elements do not shade the collectors area, namely in the heating season.

Environmental alternatives to solar space heating?

Passive solar systems are based on elements as natural ventilation, orientation of the building, large south-facing windows (north-facing in the southern hemisphere) or sound thermal materials in the floors and walls…. They are less costly than active ones (based on solar collectors), and a top economic and environmental solution for most climates. If you are going to build your home, you should bet on passive solar principles, first of all. The costs to implement them are reduced and the energy gains are enormous, but when retrofitting a building active systems are often the only option for obtaining solar energy.

See, for details on Passive Solar Systems:
Passive Solar Design
Passive Solar Heating
Passive Solar Cooling
Passive Solar Plans
Passive Solar and Orientation and Shape of the House

Other environmental alternatives include, namely, geothermal heat pumps.

For more details on solar space heating systems, see:
Solar Heating and Air Forced Systems, Radiators and Radiant Floor