Solar Power for Houses: Your Residential Solar Power System

Have you always dreamed of having a house powered by the sun? Perhaps you are seriously thinking about it, but want to know more about your options. When most people think about solar power, they think of the classic solar panels that produce electricity. These are solar photovoltaic panels. But solar photovoltaics are not the only way to use solar energy.

Solar hot water: uses the sun to heat your water instead of fossil fuels. There are several different types of solar hot water systems available. They are usually lower tech and cheaper to install than household solar photovoltaic systems, although pricing varies widely with the type of system chosen.
Pro: cheaper to buy than photovoltaic
easier to DIY than photovoltaic
Con: will only give you hot water
too heavy for some roofs
cheapest varieties don’t work in freezing temperatures

Solar swimming pool: this is actually a very inexpensive way to heat your swimming pool. It pays for itself within a few years.
Pro: short payoff time
Con: only heats your pool water

Solar thermal: technically this includes both solar hot water and solar swimming pool systems, as well as solar cookers. It also refers to heating air by the heat of the sun.
Pro: cheaper than solar photovoltaic for the amount of energy produced
Con: heat only, won’t give you electricity

Passive solar/solar architecture: designing or renovating a house so that it gains the maximum benefit from the sun’s heat, while not getting overheated during the summer.
Pro: adds very little to cost of a new house for major reductions in heating needs
Con: hard to retrofit

Solar cooker: uses the sun to cook food. It tends to cook food more slowly – can be compared to a slow cooker. Very easy to DIY compared to other solar options. They are also inexpensive to buy.
Pro: easy to DIY
cheap to buy or make
Con: needs sun to cook food
won’t do anything other than cook food
cooks food slower than most cooking methods

Solar photovoltaic: solar electricity created using the classic solar panels. A full system for your house is expensive compared to other solar power options, but it’s more versatile. It is also possible to buy very small systems intended for charging cell phones for laptops. These are very much cheaper.
Pro: extremely versatile as electricity can be used for almost anything
Con: more technically complex than other solar methods
more expensive than other solar methods for the amount of energy acquired
high-voltage electricity produced makes DIY photoelectric more hazardous than other solar power projects.

1.  Albert Einstein received a 1921 noble prize for experiments on the photoelectric effect.
2.  10,000 U.S. households are now using solar energy to power their homes.
3. On his African journey 200 years ago, John Herschel (a british astronomer) was able to cook food using solar power.
4. The first large scale solar power plant was opened in 1982 in California.
5.  Solar power comes in two major varieties: solar thermal and solar photovoltaic.
6. Solar thermal is less technologically complex than solar photovoltaic and is much easier to DIY.
7. In 2007, more Chinese homes use solar hot water than in all other countries combined.
8. The price of solar photovoltaic panels has dropped by at least 200% in the past 30 years.
9. The price of solar photovoltaic panels is currently continuing to drop.
10. The lowest solar photovoltaic prices per watt are usually for thin film.
11. The lowest solar photovoltaic module retail price is $1.25/watt (Oct. 2011) for thin film from a German retailer.
12. Current (Nov. 2011) low prices are partly due to a glut of polysilicon on the market from Chinese manufacturers, some of whom are going out of business.
13. There are pollution problems at some Chinese plants producing polysilicon.
14. Germany uses more solar photovoltaic power than the USA despite having a climate less adapted to it.
15. Photosynthesis has been in use on Earth for 3.5 billion years.

The need for solar power

The Earth is facing a multi-headed environmental crisis. These problems may seem enormous, but we are not powerless.  There is a great deal we can do to take control over our impact on the Earth and its biosphere.  The tools to do so are not yet to be invented.  We already have them, and they’ve been available for years.  We just have to do the work to change the way we do things. One of the main dangers is climate change, which is currently being driven by fossil fuel extraction. This means we need to reduce fossil fuel use drastically.

But we will still need a power source. This is where solar power comes in, along with wind, small hydro, biomass, geothermal and other renewable energy sources. Some include nuclear, but I’m not going to get into that debate right now.

Solar power, in both its thermal and solar photovoltaic forms was discovered many years ago.  It has been used in various ways since – you’ve probably used a solar powered calculator, tried to burn something with a magnifying glass when you were a kid, and seen photographs of spacecraft with their solar panel wings. We can do far more with it than we have so far.

In its thermal form, people have been making use of solar for far longer – think solariums, greenhouses and orangeries. Then of course there’s plants and photosynthesis. Starting with cyanobacteria and other algae, they’ve been using it for at least 3.5 billion years!

Solar power’s two flavors: solar thermal and solar photovoltaic

Solar photovoltaic transforms light from the sun into electricity.  If you want to light your home with solar, you need to use solar photovoltaic.  This form of solar energy is more versatile than solar thermal since you can use electricity for almost anything, but is also more technically complicated and expensive to install for the amount of energy produced.

Solar thermal uses the sun’s energy in the form of heat. It is frequently used in the form of solar hot water systems, as well as pool heating, greenhouses for growing plants, solar cookers, solar dehydrators, and passive and active heating for the house. Solar thermal is a lot easier and more practical as a DIY project than solar photovoltaic.  The materials are often cheaper and less technically complicated.  It’s also safer if you have less skill with electrical circuits, since you aren’t working with high voltage electricity.

Why solar power is practical, and how to make it work for you

Solar photovoltaic power has undergone major improvements in recent years and has become a lot more affordable.  There are now many solar photovoltaic modules with a price of under $2.00 per watt.  This is vastly better than even a year ago.  There have also been changes in the way solar is marketed – a few power companies are offering to install solar photovoltaic systems on your house for free, and then charging a set price for electricity produced that is lower than their standard electricity rates.  This makes residential solar a possibility for many people who would not have been able to afford solar on their own.

With the exception of a very few power companies, most of the costs of solar photovoltaics are up front, one time costs.  If you go this route, you pay a large sum at the beginning but then have free electricity thereafter.  Under modern circumstances of fluctuating energy prices and a changing climate, this is an excellent investment if you have the money. If you’re off the grid using a generator, you can save a lot of money over time if you go solar.

If you have rather less money but have skill with building things or electronics and some basic equipment, there are also kits for making solar panels and solar installations.  Remember that solar thermal is usually easier and safer as a do it yourself project than solar photovoltaic.

Of course, you might be more interested in other renewable energy options. There will be more articles on these subjects on this site soon.

There are a lot of ads for build-your-own solar panels on the internet, including on this site. I have no control over what ads do or do not appear, but felt a bit of research as to whether DIY solar panels were possible or cost effective was in order.

Solar Panel Price Comparisons

When sites say ‘build solar panels for under $100!’, they often seem to be comparing the materials cost of the homemade panel to the cost of an entire solar photovoltaic system which (for a house) usually includes multiple panels, an inverter, a charge controller and sometimes batteries. This is not comparing the same thing. A true cost comparison would be one of two things: the cost of the entire system, or the cost per watt of power produced by a single panel.

The full cost for a DIY solar photovoltaic system includes the number of panels that you wish to build as well as buying or building all the other parts of a system. Also include your time that you will be spending building the panels and mounting racks and then wiring and installing everything. A single solar panel by itself is not much use for home applications without an inverter and charge controller, and one solar panel will not power an ordinary house. Costs for solar panels are usually a little over 1/3 the price of an installed system, so while they are a major component they are not the only component.

Comparing Solar Panel Prices: Price Per Watt

The usual method of comparing the prices of solar panels is price per watt. For example, if a 60 watt panel is built for a materials cost of $104.85, as the maker of mdpub.com did, the price per watt is $1.75. The average price per watt for a commercially made module of over 125 W is $4.39 as of September 2009. Prices for smaller modules are generally higher per watt, so the home-made panel looks pretty good. So yes, it is possible to build a solar panel for less money than you would pay for commercial one. But there are several caveats:

• This is presuming no materials were ruined while you learned how to make the panel
• This is presuming that you manage to make the panel work properly
• This is counting your own labor cost as $0
• This is assuming the you do not have to buy soldering equipment or paint, plexiglass, wire, or screws in order to make the panel since the author of this site had them on hand
• The person who made the solar panel used as an example has also built a wind turbine and a jet engine

DIY Installation of Solar Photovoltaic Systems

Once you have made your panels, will you be installing and wiring everything yourself or will you get someone else to do it? The level of skill required is an important consideration because installing solar photovoltaic systems means working with electricity, which has a certain amount of inherent danger involved. On-grid residential solar power systems usually involve high-voltage electricity, which increases the danger if you do zap yourself.

So is Building Your Own Solar Panels For You?

I would not want to try this myself, nor do I have the equipment I would need. If you have to go and buy the equipment and then teach yourself how to use everything I would not advise attempting to do it yourself. If, on the other hand, you are an electrician with a large workshop looking for a project, building your own photovoltaic system might be worth another look.

Sources:

http://www.mdpub.com/SolarPanel/index.html

Cassandra Sweet. Sept 8, 2009 Let the Sun Shine. The Wall Street Journal

Solar module retail price environment Sept. 2009

Batteries are an important component of off-grid and many grid-tied residential solar power systems. They are used to store excess electricity produced by the photovoltaic panels for times when they are producing less electricity than needed, such as at night. Batteries are used in both off-grid applications and in grid-tied battery-backed systems. Batteries for off-grid are usually sized to last through normal use on three cloudy days.

The batteries in grid-tied residential solar power systems are used for backup when the grid goes out. There are usually fewer batteries in these banks because they are only used for backup rather than being used every single night.

The three main types of solar batteries are all lead-acid batteries. However, they are very different from the batteries used in a car because they are deep cycle batteries. This means that they can be drained much more deeply of their charge than shallow cycle batteries such as those used in cars. Car batteries will not stand up to the strain that a residential solar power system will place on them.

Batteries Suitable for Residential Solar Power Systems

Flooded Lead-Acid Solar Batteries

Flooded lead-acid batteries are the cheapest type of lead-acid batteries commonly used to store solar power. They also have the longest life, but require regular maintenance. Distilled water must be added as necessary to replace that lost during charging, and because they are not sealed they must be kept clean and there is a danger of spillage.

Absorbed Glass Matt Sealed Lead-Acid Solar Batteries

These are sealed, and therefore do not require regular maintenance as flooded lead-acid batteries do. They are a newer invention and so far less widely used than flooded lead-acid.

Gelled Electrolyte Sealed Lead-Acid Solar Batteries

These are freezing resistant and are typically used in unheated spaces. They must be charged slowly in order to avoid decreasing capacity, making them better for grid-tied backup than for off-grid uses.

Sources:

Homepower.com

Solar-Batteries.net

There are three main types of solar panel for sale at present: monocrystalline, multicrystalline, and thin film panels. A fourth, sometimes known as vaporware, is sometimes mentioned in the media, but does not yet exist. There is no one best solar panel for every purpose, but each type of solar panel has its own advantages and disadvantages.

Monocrystalline Photovoltaic Panels:

Pros:

• Most efficient, especially in low light conditions
• Less space required for the same amount of power
• More durable than Thin Film

Cons:

• Most expensive per watt
• Production process uses more silicon and more energy
• Rigid

Polycrystalline/Multicrystalline Photovoltaic Panels:

Pros:

• Lower price than Monocrystalline
• Higher efficiency than Thin Film

Cons:

• Higher price per watt than Thin Film
• Rigid
• Lower efficiency than Monocrystalline

Amorphous/Thin Film Photovoltaic Panels:

Pros:

• Cheapest per watt
• Can be made flexible
• Harder to break
• Uses less silicon and less energy during manufacture

Cons:

• Degrades faster
• Lower efficiency
• More space required to produce the same amount of electricity

Vaporware?

This doesn’t actually exist yet, but if it ever does, it will be photovoltaic material that you spray onto a substrate which then becomes a photovoltaic panel.

In Practice:

The type of application has a major impact on which type of solar panel is best for you.  If you want to have solar panels on a backpack where the panels have to be flexible, your only choice is Amorphous/Thin Film panels.  However, if you require the largest possible amount of electricity from the smallest area of solar panel and do not care about it being flexible, then Monocrystalline photovoltaic panels are best.  The choice is up to you.

For More Information:

Northern Arizona wind and sun

Solar Sphere

There are now many types of portable solar equipment available.  They range from the truly gimmicky to the sensible. From hats with a solar panel and fan for cooling your head to  solar powered calculators and portable solar charging systems.  Keeping track of what’s out there can be a challenge.

Portable Solar Devices:

Some of the solar powered items for sale on the Internet include halogen lanterns, hats with fans, Christmas lights, radios, portable refrigerator/freezers, battery chargers, bags, outdoor lighting of almost every description, rodent repellers, children’s toys and others.  Examples of such things for sale can be found at solarhut.com, as well as many other places on the internet.  Many solar objects are new designs or are being made by companies without a long reputation in the field.  This means that while there is a wonderful selection, the quality is rather variable.

Portable Solar Charging Systems

Portable solar charging systems are much more practical than they used to be.  Many of them make use of technologies like thin film photovoltaics so that they can be folded up and packed away when not in use.  For people like backpackers, this means that you can stick your solar panel in your backpack and have power wherever you go.  There are also battery chargers that are part of bags or backpacks.  A review of such an item can be found on treehugger.com. On a somewhat larger scale, solar panels are also used on boats and RVs to power appliances and charge batteries.

Solar thermal and solar photovoltaic power are similar in that both use the sun as an energy source, and both are renewable. However, there are quite a few differences between them, including price, type of energy output, and the things that energy can be used for in your home.  The table below should give you a good idea of the pros and cons of both types of solar power.

Prices are global average for July 2009 and are US denomination. They exclude rebates your government may give. They assume the system is grid-tied.

http://www.solarbuzz.com/solarindices.htm

Solar pool heaters are the most common use of solar thermal technology in North America.   This is because they are extremely cost effective: a solar pool heater will typically pay for itself in 2 to 3 years (Can. Solar Industries). Even without considering the savings in greenhouse gas emissions, solar pool heaters make a lot of sense.   The total price of solar heating a pool is usually $3,000-$4,000 US including installation, but can range from $2,500 to $7,000 US (Costhelper.com).

Solar hot water panels used in pools are flat plate collectors. They are usually made of rubber or black plastic and are a very simple use of solar thermal technology compared to solar water heating systems for drinking water.

The solar hot water panels are usually about 50% of the pool’s service area.  If a pool is indoors or is not in direct sunlight, a larger area of solar heating panels must be used to reach the same temperature.   A pool cover should be used at night to reduce heat loss.  If you don’t use a pool cover, you’ll need to install twice the area of solar hot water panel.

While solar pool heaters make excellent sense for swimming pools, they don’t work as well for hot tubs.  The water temperature can be raised high enough using metal collectors used for heating domestic water, but if the jets in the hot tub are used, the water will swiftly cool down again.

Sources:

Canadian solar industries association.  Solar pool heating overview.  Retrieved June 20, 2009

Costhelper.com

Residential solar pool heating systems: a buyer’s guide 2001 retrieved June 20, 2009

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