Solar Power for Houses: Your Residential Solar Power System

Passive solar heating is a great way to provide much of your home’s heating for free. Almost every home gets some solar energy coming through the windows, but there is a vast difference between the average house and a home heated with passive solar energy.

Building a new house that is passively solar heated is not significantly more expensive than building a normal house. This makes passive solar the most cost-effective form of solar power for the new home. Every new home should be built using passive solar techniques because home heating and cooling needs can be reduced greatly – potentially to zero in certain circumstances.

All this sounds wonderful, but there is one caveat: you must find a good architect who understands passive solar design. Some architects do not understand how to do it properly and mistakes made during the building process may prove costly later.

Passive solar heating covers a wide range of strategies, including passive solar thermal hot water heaters such as the batch and thermosyphon, but it’s usually used to describe heating the house air and structure.

Direct Passive Solar Heating

The simplest form is direct passive solar heating. This involves big windows on the south side of the house. The sunlight falls onto a dark surface with a high heat storage capacity such as a masonry floor or wall painted a dark color. Water is sometimes used instead – this involves water contained in glass or transparent plastic. It has slightly different properties than solid walls, but the basic idea is the same. The wall or floor absorbs energy on sunny days, and releases it at night or on cloudy days when things get cooler.

Of course, you don’t want the house to overheat in the summer. This is generally avoided by building overhangs over the windows. In the winter the sun is at a low angle and comes in the window. In the summer, especially near midday, the sun strikes the overhang and doesn’t come into the room. This leaves the room much cooler.

Trombe Walls (Indirect Gain) and Solar Spaces (Isolated Gain)

There are two other major passive solar heating strategies, Indirect Gain and Isolated Gain. The most common Indirect Gain method is the Trombe Wall, and the most common Isolated Gain method is the solar space.

Trombe walls involve a thick wall painted a dark colour. An inch or so in front of it is glass. Sunlight enters through the glass and is absorbed as heat by the wall. The glass helps prevent heat loss, and wall slowly releases the heat into the rest of the house. Again, a Trombe wall is placed on the south side of the house.

A solar space is basically a glassed-in space on the south side of the house. They are also sometimes known as solar rooms or solaria. Solar spaces can act as greenhouses, and they are sometimes referred to as greenhouses. However, they are not the same as greenhouses designed to grow plants.

The glass is vertical, and there usually isn’t glass overhead. This is so that the glass can be shaded in the summer to avoid overheating. It also means the plants that grow there have less light than they would in a true greenhouse, although more than they would in your house. Since they are attached to the house, you may not want to grow large numbers of plants in it if you’re allergic to mildew. However, if you’ve always wanted a greenhouse,why not use it to grow plants?

These three types of passive solar heating are the most commonly used. While the systems describes here are simple and this overview is simple, there’s a lot more to passive solar design when you really start looking deeply into the subject.

Sources:

Arizona Solar Center

US department of energy: energy efficiency and renewable energy. Passive solar home design.

In climates where there are freezing temperatures, the water in solar hot water panels is in danger of freezing.  No hot water is produced when this happens, and it’s possible that the panels or piping could be damaged when the water expands as it freezes.   However, it’s perfectly possible to get solar  hot water in a cold climate – even during the winter.

The most common way to prevent the solar hot water panels freezing is to use glycol-based solutions in the panels. This requires a closed loop system where the heat is transferred from the glycol solution into the water you use in your house via a heat exchanger.   These systems are more expensive than simpler systems, but they are much more resistant to freezing and can continue to produce heat through the middle of a cold winter.   You will probably want a tankless hot water heater as backup because they may not produce enough for your needs when there are long spells of cloudy weather, but they will still produce hot water.  Both active and passive heaters can be outfitted with glycol so long as there’s a closed loop system.

Four-Season Solar Thermal Systems

Glycol-based solutions are typically used in active solar thermal systems, but they are also used in some Thermosyphon systems.  In order to use glycol in a Thermosyphon system, it must be a closed-loop system in which the solution in the solar thermal panels does not mix with your household water supply.  The glycol acts as antifreeze, preventing the pipes from freezing.  These solutions are typically 50/50 glycol and water.  Active glycol systems tend to be expensive, but they are considered the best choice for very cold climates.

There is one type of water-based system that can be used in frost-prone areas.  This is the drainback system, which does not easily freeze so long as the piping is sufficiently inclined so that drainback can occur quickly.  However, I suspect that this system is less tolerant of extremely cold temperatures for long periods of time than a system that uses a glycol fluid.

Three Season Solar Hot Water Systems

It is also possible to use a very simple system such as the batch heater during the summer and drain it during the winter.  You will get no hot water from it in the winter, but it should still be usable the next summer.

As you can see, there are several choices of thermal hot water systems for homes in a cold climate. Whether active or thermosyphon glycol, drainback or summer-only batch, there is probably something available that will fit your needs and pocketbook.

Sources:

US Department of Energy. Energy Efficiency and Renewable Energy. Energy Savers: Solar Water Heaters. Retrieved June 19 2009

Homepower.com. Retrieved June 19 2009

Build it Solar: solar water heating. Retrieved June 19, 2009