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Due to the high cost of energy, my husband and I would like to consider
converting to solar. Could you please give us an overview of how it works, how
much it costs, and whether it’s feasible?
There are two main ways to use the power of the sun to reduce energy costs in
your home. You can use the heat from the sun’s rays to heat your home or your
domestic hot water, or to produce electricity to power lights and appliances.
Other people have written some very good books about using
solar energy in both renovations and new construction of homes. (See the list at
the end of this article for some good ones.) So in the small amount of space
available here, we’ll give you the very basics as well as some things to think
Rather than spreading energy payments over a long period of
time, as with natural gas or electricity, a solar system places all the costs up
front. However, once the system is paid for, the sun doesn’t charge for its
energy, so the pay-back begins.
The initial costs (and, hence, the pay-back timeline) will
depend on the purpose, type and size of the solar system you choose. And that
will depend on your budget, as well as the size of your family, your lifestyle,
your geographic location, and the way your house is situated. However, an
increasing number of governments are offering financial incentives to encourage
homeowners to switch to solar, so you’ll need to research what’s available in
Heating Hot Water
You are probably looking at a relatively high initial cost to retrofit your
home with a thermal space heating system. But just about anyone whose house or
yard is exposed to continuous sunlight can preheat their hot water using solar
energy, so that might be a good place to begin your solar adventure. The initial
cost is not as high as other solar projects and the payback won’t take too many
In 2006, the solar industry reported that the average price of a solar
domestic hot water system in Canada was around $6000. Estimated payback
periods for a solar water heater range from six to 13 years for water
originally heated by electricity, and 12 to 20 years for natural gas
heating. That system will easily cut your water heating bill in half and
could save up to two metric tonnes of greenhouse gas emissions annually.
Solar water heating systems include solar collectors and storage tanks.
Two main types of solar collectors are used for residential purposes in cold
climates. They are flat plate collectors and evacuated tube collectors.
Glazed flat-plate collectors are insulated, weatherproofed boxes that
contain a dark absorber plate under one or more glass or 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.
Evacuated-tube solar collectors 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 heat
In climates where temperatures rarely dip below freezing, a direct
circulation system can be used, where pumps circulate household water
through the collectors and into the home. In colder climates, an indirect
circulation system is used, with pumps circulating a non- non-freezing,
heat-transfer fluid through the collectors and a heat exchanger.
There are also passive solar water heating systems. A thermosyphon system
works on the principle that warm water rises as cooler water sinks. The
collector is installed below the storage tank so that warm water will rise
into the tank, typically situated on a roof.
Most solar water heaters require a well-insulated storage tank. 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.
A typical family of four in North America uses about 80 US gallons of hot
water per day. One gallon of hot water requires one square foot of collector
area. A family of four will probably require two four-foot by ten-foot solar
collectors and a tank with a 100-gallon capacity.
Hot water can also be used to heat your whole home. In that scenario, solar
hot water is used for in-floor radiant heating or even to circulate through
But that will not keep your house warm when the sun isn’t shining and hardly
seems worth the effort or cost if a conventional heating system was also still
required. So you would need to add a serious amount of thermal mass to the
equation, perhaps in the form of thermal mass interior walls, which would be
warmed by the solar heated water, and retain and radiate that heat for longer.
However, that sort of experimentation is not easily accomplished in a retrofit
Conventional solar electric technology uses photovoltaic (PV) cells, which
are semiconductor devices, usually made of silicon. Photons in sunlight are
absorbed by the silicon and electrons are knocked loose from their atoms,
allowing them to flow through the silicon to produce electricity. Because they
contain no liquids, corrosive chemicals or moving parts, PV cells require very
little maintenance, don’t pollute and operate silently.
Individual PV cells are used for powering small devices such as electronic
calculators. To provide larger amounts of energy, the cells are bundled together
into modules or what we know as “solar panels” to produce higher voltages and
increased power. These panels have a sheet of glass on the front, allowing light
to pass while protecting the cells from the elements. Panels can be linked
together in arrays.
These panels generate direct current (DC), the kind of electricity produced
by batteries. Most North American electrical devices require 120-volt
alternating current (AC), which is what is supplied by local utilities. A device
known as an inverter is used to convert the solar-generated DC to AC current for
use in your home. Inverters vary in size and in the quality of electricity they
supply. Less expensive inverters are suitable for simple loads, such as lights
and water pumps, but high quality models are needed to power electronic devices
such as TVs, stereos, microwave ovens and computers.
Many PV systems are grid-tied, either ground-mounted or built into the roof
or walls of a building. Off-grid PV systems generally use rechargeable batteries
to store excess electricity. With grid-tied systems, excess electricity can be
sent to the transmission grid. Net metering programs give these systems a credit
for the electricity they deliver to the grid. This credit offsets electricity
provided from the grid when the system cannot meet demand, effectively using the
grid as a storage mechanism.
Due to the increasing demand for solar energy, the manufacture of solar cells
and PV arrays has been increasing by almost 50 percent a year recently.
Technology has also been improving rapidly, decreasing the cost and making the
cells smaller and more flexible.
Although prices vary, for a small scale PV system, you would probably pay
around twice what you’d pay for a solar water heating system and the payback
period would be approximately 15 to 25 years. Greater cost savings are usually
realized through an economy of scale: The larger the solar energy system, the
lower the cost of energy delivered for the money invested.
If you have sat by a sunny, south-facing window on a cold day, you have felt
the effects of passive solar energy. Passive solar uses walls, windows, floors
and roofs, in addition to exterior building elements and landscaping, to collect
and store heat generated by solar radiation. Although it won’t provide all of
the space heating necessary in a cold climate, passive solar can significantly
lower your bill. Experts claim that using building envelope upgrades alone,
passive solar can supply 25 percent of a building’s heating requirement.
For effective passive solar heating, high performance windows are necessary,
including insulated frames, multiple glazing, low-e coatings, insulating glass
spacers and inert gas fills. The most efficient window orientation for heat gain
is due south, but any orientation within 30 degrees of due south will work. To
let the sun in, a ratio of roughly eight percent window to floor area is
recommended for south walls.
Once the heat is in, R-2000 levels of insulation and an air-tight building
envelope help keep it there. With the heat contained, a simple ceiling fan or
your furnace fan can distribute the heat.
The solar warmth can be maintained by using thermal mass in the walls and
floors to absorb the sun’s heat and radiate it back into the room in the
evening. Common thermal mass materials include stone, cement and water.
A solar (or thermal) chimney is a passive solar ventilation system composed
of a vertical shaft connecting the interior and exterior of a building. As the
chimney warms, the air inside is heated causing an updraft that pulls air
through the building.
So you can see that there are many options for harnessing the power of the
sun in your home!
Solar Water Heating: A Comprehensive Guide to Solar Water and Space Heating
Systems by Bob Ramlow, Benjamin Nusz (New Society Publishers, 2006)
Passive Solar House by James Kachadorian (Chelsea Green Publishing Company,
The Renewable Energy Handbook: A Guide to Rural Energy Independence, Off-Grid
and Sustainable Living by William H. Kemp (Aztext Press, 2006)
Photovoltaics: Design and Installation Manual by Solar Energy International
(New Society Publishers, 2004)
The Solar House: Passive Heating and Cooling by Daniel D. Chiras (Chelsea
Green Publishing Company, 2002)
Wendy Priesnitz is Natural Life Magazine's co-founder and editor.
She is also a journalist with over 35 years of experience and the author of twelve books.
This article was published in Natural Life Magazine's
November/December 2008 issue.