Solar Power for Houses: Your Residential Solar Power System

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

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