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

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.

People turn to solar power for several different reasons:

• High energy prices
• Climate change
• Fossil fuel depletion
• Solar energy costs are coming down

When these factors are taken into account, it’s no wonder that people are going solar. Here are some more data on each:

High Energy Prices

While we’ve been hearing most about high oil prices over the past few years, electricity prices have also been going up in many places. When combined with the price of solar photovoltaics coming down, solar looks a lot more practical than it used to. The recession may have lowered energy prices temporarily, but how long will that last? The volatility in energy prices also makes solar power attractive because you don’t get left vulnerable to energy price spikes when you produce more electricity than you use.

Climate Change

Operating a residential solar power system does not produce CO2. While some CO2 is produced during the making of solar panels and other elements of the system, there are vastly lower emissions than from the production of electricity from oil, gas, or most especially coal. Thus, every solar photovoltaic array very slightly reduces the likelihood of catastrophic climate change.

Fossil Fuel Depletion

The easiest, cheapest oil gets used first. Most oilfields and wells being brought into use now produce oil that is difficult to access or process in some way. This tends to keep oil prices high. It looks increasingly likely that we have hit Peak Oil, which means diminishing supplies of oil in the future no matter how much oil exploration and development we do.

While most electricity does not come from oil, prices for all forms of energy are linked and are likely to become increasingly so as more electric vehicles are made, and even more so if Coal-to-Liquids technology is used on any large scale. In the US, coal is the largest source of electricity. If Coal-to-Liquids plants are built to compensate for Peak Oil, this would increase the price of coal, and therefore that of electricity.

Coal supplies are not endless and it looks increasingly likely that there may be less recoverable coal than commonly thought. This is likely to raise electricity prices in the future. In such an environment renewable energy sources, including solar, look better and better.

Residential Solar Energy is Becoming More Affordable

The current recession has resulted in people buying less. During the high oil prices, producers of solar panels and other components vastly increased capacity. When the recession hit, they found themselves with excess solar photovoltaic systems, components, and raw materials. Prices dropped.

The USA is about to start giving larger rebates for solar which will help increase affordability for a very large, affluent market. This is likely to increase demand for solar energy, which might prevent lowering of prices in the short term, but will likely reduce them in the long term by increasing the capacity of industry. China has also started manufacturing solar panels, which is likely to reduce solar panel price due to economies of scale and cheaper labor in that country.

In California there is at least one company that offers leases of solar photovoltaic systems with guaranteed electricity prices lower than that of some utilities in that area. This increases affordability of solar by eliminating the high start-up costs of home solar systems which act as the largest barrier to going solar for many people.

More Information:

Fossil Fuel Depletion, Peak Oil and Energy Prices:

The Oil Drum

Richard Heinberg’s Museletter

Heinberg, R. 2009 Blackout: coal, climate and the last energy crisis. New Society Publishers.

Trends in Renewables and Renewable Energy News:

Renewable Energy World

This job requires tolerance of heights, strength to lift heavy objects
and knowledge of how to install electrical objects safely.

The pay is usually about 15 to 23 dollars an hour. The whole solar sector is a high growth sector of the economy, and job prospects are bright. A high school education is usually expected, along with some construction experience and an apprenticeship or trade school education. However, the exact things employers look for vary somewhat. I culled the list below from actual job ads:

Things employers look for when hiring solar installers are:

• Ability to lift heavy objects (approx. 30-50lbs)
• Ability to work in a variety of positions
• Ability to work in hot sun and awkward spaces
• Not afraid of Heights
• Ability to interact with clients
• Attention to detail
• Ability to keep records and understand documentation
• Driver’s license and clean driver’s record
• Construction-related experience

Knowledge of Computer Software, OSHA safety regulations, and ability to understand blueprints is also often required.

Sources:

SolarInstallerjobs.com

A Day (or Three) in the Life of a Solar Installer

Places Hiring Solar Installers:

Standard Solar

SolarCity

Rec Solar

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

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

To create hot water using solar thermal energy, the sun’s heat is used to heat water directly without converting it into electricity.   The most common use of solar hot water in North America is heating swimming pools, but solar thermal’s potential goes far beyond this.

Solar thermal is commonly used for water heating and for heating houses.  The cost of heating by a solar thermal system is usually lower than the cost of an equivalent amount of electricity supplied by photovoltaics because solar thermal is on average 3x more efficient at converting the sun’s heat into energy, although the savings depend on the type of solar thermal technology used.  Solar thermal systems are also low maintenance.

Types of Solar Water Heater

1) Collector (solar hot water panel) Types

There are three main collector types: flat plate, batch, and evacuated tube.  Evacuated tube technology is generally more expensive than flat plate and batch because it is mechanically more complicated.

2) System Type: Passive or Active

Active systems include a pump; passive systems do not.  Passive systems are less expensive and may be more reliable but are less efficient (Energy Savers: Solar Water Heaters).

Passive Solar Water Heating

Batch Heater

A batch heater is the simplest type of solar water heater available.  They are also sometimes known as breadbox heaters, since the tank of water on the roof is often about the size of a breadbox.  If you wish to build your own solar hot water system, a batch heater is probably your best bet.   Being water-based, they are not suitable for winter use in climates where freezing weather can be expected.  They also have the disadvantage that hot water cools overnight and usually isn’t hot early in the morning.   The Florida Solar Energy Center has a free set of plans and instructions for building one, which can be found here.  They give the materials cost as being US $70.00.

Thermosyphon

This design tends to be more expensive than batch heaters.  However, because there is an insulated storage tank hot water is available at all times of the day or night, unlike the batch filter.  This design is actually the world’s most popular solar water heater (Homepower.com).  It may be closed loop or open loop.  If it is a closed loop system, glycol can be used.  This modified design is suitable for using in climates with freezing temperatures.

Active Solar Water Heating

Drainback Heater

This type of heater is more complex, being a closed loop system where the water in the collector does not mix with the house’s water.  A heat exchanger is used to move the heat from the liquid in the collector to the house’s water.  Like most active systems, it is more expensive than a batch heater.  On the other hand, this system can be used in the winter in climates with freezing temperatures if the pipes are adequately sloped to ensure drainback occurs quickly.

Glycol-based Solar Thermal Systems

Systems containing glycol are primarily used in areas which have freezing temperatures during winter.  This is because they continue to work and provide hot water during such weather, unlike most systems that use water.  Water-based systems may also suffer damage when the collectors freeze that will then need to be repaired.  Glycol-based systems are more expensive than systems that use water, but in a cold climate this disadvantage is outweighed by their resistance to freezing (Homepower.com).

Overall, solar thermal hot water is a technology that is economical to install and run by renewable energy standards and can be used almost anywhere.  It has excellent potential for home use and should be perhaps the first alternative energy technology considered by a homeowner wanting to reduce dependence on the electricity grid.

Sources:

Build Your Own Solar Batch Water Heater. Florida Solar Energy Center Retrieved June 12, 2009.
http://www.builditsolar.com/Projects/WaterHeating/FSECFS36Batch11349.pdf

US Department of Energy. Energy Efficiency and Renewable Energy. Energy Savers:Solar Water Heaters. Retrieved June 12 2009
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850

Homepower.com
http://www.homepower.com/basics/hotwater/