Lowering your heating and cooling costs

The majority of your energy budget is spent heating and cooling your home. By maintaining your heating and cooling systems you can save money and enjoy year-round comfort.
Your Air Conditioner

1. Select an air conditioner with a high Energy Efficiency Rating (EER) and cut your cooling costs down significantly. Your upgrade will pay for itself.
2. Save money and extend the life of your system by properly maintaining your air conditioner.

• Check your filter every three or four weeks and replace or clean as needed.
  
• Hire a qualified technician to clean your coils and check your equipment annually.
  
• Keep air flow vents open and unobstructed and regularly vacuumed.

Fans

• Fans improve the air circulation in your home, making your furnace and air conditioner’s job easier.
  
• Ceiling fans use only one-tenth the electricity of a typical home air conditioner.
  
• Full-house attic fans push hot air out and draw cool night air in.
  
• Small attic fans remove hot air trapped in attics.
  
• Exhaust fans control humidity in your home.
  
• Most consumers require the services of electricians and carpenters to install attic, ceiling and exhaust fans.
  
• Exhaust fans require a duct leading outdoors to prevent grease and moisture buildup in your walls and attic.

Fireplaces

Great for setting a mood and making rooms cozy, fireplaces send most of their heat right up the chimney. Here are a few tips for making your fireplace as energy efficient as possible:

• Keep the damper closed when fireplace is not in use.
  
• Burn low to medium sized fires.
  
• Use long logs that offer greater surface area and reflect more heat.
  
• Use a cast iron "fireback" placed near the rear wall of the fireplace to reflect heat into the room.
  
• If your fireplace has glass doors, use them to cut down the amount of air drawn from the rest of your home.
  
• Provide combustion air from outdoors through a duct running directly to your fireplace.

Managing Your Thermostat

By knowing where to locate your thermostat and how and when to adjust it, you can save more on your heating and cooling costs.

• For an accurate indoor temperature reading, locate your thermostat on an interior wall and away from appliances that give off heat.
  
• If you plan to be away from home, or when you go to bed at night, turn your thermostat down in winter and up in summer to save money.
  
• When you are home, set the thermostat at a constant temperature so your system works efficiently and you save energy dollars.
  
• You can install a programmable thermostat with a built-in timer to automatically regulate your heating and air conditioning needs.
  
• Your thermostat is a precise, delicate instrument that does not require regular cleaning. For best results, occasionally remove the cover and gently blow out any dust or lint that has accumulated.
  
• An older thermostat of 15 years or more may need to be replaced with a new, efficient model.

Controlling Humidity

Your personal comfort is affected by humidity as well as temperature. Moist air feels warmer than dry air. Save energy dollars by retaining humidity in the winter and expelling it with exhaust fans during summer. Steam from showers, cooking and laundry add to your indoor humidity. Humidifying units, either freestanding or installed, will also add moisture to your air.

Energy efficiency pays. It produces long-term savings on your energy bill, improves productivity and saves valuable resources.
Using Electricity Efficiently
Whether it’s hot, cold or in between, the time’s always right to use energy wisely!

In the summer …

•  Take cool baths or showers
  
• Use fans to circulate the air
  
• Stay out of direct sunlight
  
• Wear lightweight, loose-fitting clothes
  
• Avoid hot foods and heavy meals
  
• Drink water frequently—whether you feel thirsty or not
  
• Seek medical help if you experience dizziness/dry skin (with no sweating) great weakness, nausea, diarrhea or vomiting. If you feel disoriented—altered consciousness or confusion, develop a throbbing headache, experience a rapid heartbeat, breathing problems, chest pains or cramps—all could be signs of heat stress.

If you have an air conditioner …

• Keep your air conditioner in the shade.
  
• Cool only the rooms you use, but don't close all your vents.
  
• Turn your thermostat up when you leave the house for several days or longer.
  
• Don't switch your air conditioner to a colder setting when you turn it on or adjust it throughout the day. Set the thermostat at 78 degrees Fahrenheit, if possible.
  
• Don’t place your thermostat on an external wall or near appliances that give off heat.
  
• Gently blow out any dust or lint out of your thermostat.
  
• A timer or programmable thermostat can be used to turn your air conditioner on before you get home. Make sure your air conditioner coils are clean.
  
• Check your filter at the beginning of the cooling season.
  
• Keep the heat out by drawing shades and curtains on hot days.
  
• If you have exhaust fans in your bathroom, laundry and kitchen, use them to help reduce the humidity burden on your air conditioner. These fans should not be used continuously, but periodically, as required.
  
• Help protect the ozone layer by repairing leaks in home and auto air conditioning systems. To learn more, contact the U.S. Environmental Protection Agency in Kansas City at 1 (800) 223-0425.

In the winter ...

• Install storm windows and caulking to keep cold air out and warm air in.
  
• Use weatherstripping around doors.
  
• Blown insulation for attics and walls is an easy-to-install energy-saver.
  
• Have a qualified technician check your furnace performance before the heating season starts.
  
• Use an insulating blanket on your hot water heater and wrap insulation around your hot water pipes to reduce heat loss. Reverse ceiling fans to circulate warm air.
  
• Glass doors for fireplaces save energy and heat.
  
• Consider an electric heat pump for year-round comfort, winter and summer.

Compact Flourescent Lighting

Many of us don't think twice about replacing a burned out light bulb in our homes. Although relatively simple in design and low in efficiency, the incandescent light bulb has changed little over its 120-year history, and it remains the residential light source of choice.

However, over the last 20 years, a new light source has emerged into a multi-million dollar market. Using refined and scaled-down designs from its bigger, tube-shaped cousin — the fluorescent bulb — the compact fluorescent lamp (CFL) has found its way into many homes. The first CFLs were used across Europe and Asia in primarily commercial and retail applications, including offices and public spaces.

A 100-watt incandescent bulb, which typically lasts about 1,000 hours, can now be replaced by a 25-watt CFL, lasting 10,000 hours. Not only would one save on the cost of 10 bulbs — equaling at least $5.00 — but at 7.2 cents per kilowatt-hour, an additional $54.00 would be saved in energy over the 10,000 hour life of the bulb. That's at least a $59.00 saving per bulb. The CFL purchase cost would be approximately $8.00-11.00, resulting in a net savings of up to $51.00 per bulb.

A variety of CFLs are now available. The newest are spiral shaped and have electronic circuitry. The spirals are not much larger than the incandescent bulbs they replace. Some CFLs (including spirals) are offered as a 2-piece design, where only the glass portion of the bulb is discarded after burnout. The glass portion "plugs in" to the electronic "ballast" in the plastic screw-in base. Spiral CFLs also best match the ball shape light pattern produced by incandescent bulbs, making them ideal for table lamps.

Over the last several years many CFL manufacturers in Asia and Europe had been aggressively competing with American manufacturers. The bottom line is that these products have become much more affordable and available. Purchasing the energy efficient CFLs makes sense, even in places where residential electricity is relatively low in cost.

CFLs are now available in a floodlight shape design (built on reflector) which can be used for recessed or track lighting applications. The vast majority of these have the replaceable glass portion as well as a detachable reflector for maintenance.

Some non-dimming CFL floodlight models are rated for outdoor use in the weather and can replace some of those expensive lower-wattage halogen floodlight bulbs we use to light our decks, yards and patios.

The plug-in CFLs used in the new floor lamps will last 8-10 times longer than halogen, which costs about $4.00 per bulb.

Today's CFLs are virtually indistinguishable in color from the incandescent bulbs they replace. Wattages for the electronic spiral versions range from 11 to 30 watts:

    * The 11-watt, the smallest size spiral replaces a 40-watt bulb.
* The 15-watt replaces a 60-watt bulb.
* The 20-watt replaces a 75-watt bulb.
* The 25 or 26-watt models replace the 100-watt bulb.

Here are some tips for using CFLs to light your home:

• Unless specified on the box, never use CFLs in sockets on dimmers, even if the dimmers are turned up to full brightness. This will cause very short life and poor performance.
  
• CFLs may be used outdoors, provided they are completely protected from the weather and are rated for cold temperatures. Most electronic CFLs will start down to 0 degrees Fahrenheit, some down to -22 degrees Fahrenheit. Always read the box before purchasing.
  
• CFLs should never be used in very warm or hot locations, such as in ovens, over range tops, saunas, attics, etc., as this will result in a very short life with no return on investment. Some high wattage CFLs may not be suitable for use in totally enclosed (unvented) light fixtures.
  
• The life of all fluorescent bulbs including CFLs is maximized when they are not frequently switched on or off. Avoid use in bathrooms, closets, pantries, etc.
  
• Your greatest and quickest savings will result in areas where you have more hours of continuous burning on a regular basis, such as kitchens, home offices, living areas, dens and outdoor lighting on all night.

Wind power
Wind Turbine Industries Corp - The Jacobs Wind Systems are on the cutting edge for providing clean, quality, reliable and efficient power in the USA and around the world.

In the energy conscious person of today we see a desire to reduce electrical usage or cut the cost paid for energy consumption.  A Jacobs Wind System can provide you a means of offsetting the ever-rising costs of your electrical energy. Since 1986
- Prior Lake, Minnesota
Turn-key Price Range: $61,000  - $126,000
Due to quality issues, MAAPS will not sell turbines that are not manufactured anywhere but in the United States, North America or Europe.

Proven Energy - The high performance Proven Turbine is the result of 25 years of
innovative research and development, and has become an international market leader, renowned for quality and durability. Key to their success is the unique design of the Proven blade, which adapts to the wind, optimising performance and safety even in the strongest winds. With over 800 installations worldwide, the Proven Turbine delivers affordable energy and security to a wide range of applications. 

Proven Energy works with Corporate bodies, Government agencies, Local Authorities, Community groups and Homeowners to provide sustainable energy solutions. Installing a Proven Turbine system will cut fuel consumption and reduce carbon emissions.
- Stewarton, Scotland, UK
Turn-key Price Range: $109,000  - $139,000
15kw Horizontal Axis Wind Turbine
Northern Power Systems - At 100 kilowatts of rated power, the Northwind 100 is a technological masterpiece with its innovative gearless design, best-in-class reliability, and pleasing aesthetics. 

With optimized performance, the Northwind 100 is built for low wind speeds, so you don’t have to live in a wind tunnel to benefit from wind power. Our turbines begin making power at wind speeds as low as 3 meters per second (6 mph) and can provide clear economic benefits in all kinds of wind regimes.
- Barre, Vermont
Turn-key Price Range: $450,000  - $600,000
100kw Horizontal Axis Wind Turbine

Solar Electricity
How Solar Cells Work

You've probably seen calculators that have solar cells -- calculators that never need batteries, and in some cases don't even have an off button. As long as you have enough light, they seem to work forever. You may have seen larger solar panels -- on emergency road signs or call boxes, on buoys, even in parking lots to power lights. Although these larger panels aren't as common as solar powered calculators, they're out there, and not that hard to spot if you know where to look. There are solar cell arrays on satellites, where they are used to power the electrical systems.
cell

You have probably also been hearing about the "solar revolution" for the last 20 years -- the idea that one 
day we will all use free electricity from the sun. This is a seductive promise: On a bright, sunny day, the sun shines
approximately 1,000 watts of energy per square meter of the planet's surface, and if we could collect all of that 
energy we could easily power our homes and offices for free.

Converting Photons to Electrons

The solar cells that you see on calculators and satellites 
are photovoltaic cells or modules (modules are simply a 
group of cells electrically connected and packaged in one
frame). Photovoltaics, as the word implies (photo = light, 
voltaic = electricity), convert sunlight directly into electricity.
Once used almost exclusively in space, photovoltaics are used more and more in less exotic ways. They could even power your house. How do these devices work?

Photovoltaic (PV) cells are made of special materials called semiconductors such as silicon, which is currently the most commonly used. Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely. PV cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off to use externally. For example, the current can power a calculator. This current, together with the cell's voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.

That's the basic process, but there's really much more to it. Let's take a deeper look into one example of a PV cell: the single crystal silicon cell.

Silicon

Silicon has some special chemical properties, especially in its crystalline form. An atom of silicon has 14 electrons, arranged in three different shells. The first two shells, those closest to the center, are completely full. The outer shell, however, is only half full, having only four electrons. A silicon atom will always look for ways to fill up its last shell (which would like to have eight electrons). To do this, it will share electrons with four of its neighbor silicon atoms. It's like every atom holds hands with its neighbors, except that in this case, each atom has four hands joined to four neighbors. That's what forms the crystalline structure, and that structure turns out to be important to this type of PV cell.

We've now described pure, crystalline silicon. Pure silicon is a poor conductor of electricity because none of its electrons are free to move about, as electrons are in good conductors such as copper. Instead, the electrons are all locked in the crystalline structure. The silicon in a solar cell is modified slightly so that it will work as a solar cell.

Silicon in Solar Cells

A solar cell has silicon with impurities -- other atoms mixed in with the silicon atoms, changing the way things work a bit. We usually think of impurities as something undesirable, but in our case, our cell wouldn't work without them. These impurities are actually put there on purpose. Consider silicon with an atom of phosphorous here and there, maybe one for every million silicon atoms. Phosphorous has five electrons in its outer shell, not four. It still bonds with its silicon neighbor atoms, but in a sense, the phosphorous has one electron that doesn't have anyone to hold hands with. It doesn't form part of a bond, but there is a positive proton in the phosphorous nucleus holding it in place.

When energy is added to pure silicon, for example in the form of heat, it can cause a few electrons to break free of their bonds and leave their atoms. A hole is left behind in each case. These electrons then wander randomly around the crystalline lattice looking for another hole to fall into. These electrons are called free carriers, and can carry electrical current. There are so few of them in pure silicon, however, that they aren't very useful. Our impure silicon with phosphorous atoms mixed in is a different story. It turns out that it takes a lot less energy to knock loose one of our "extra" phosphorous electrons because they aren't tied up in a bond -- their neighbors aren't holding them back. As a result, most of these electrons do break free, and we have a lot more free carriers than we would have in pure silicon. The process of adding impurities on purpose is called doping, and when doped with phosphorous, the resulting silicon is called N-type ("n" for negative) because of the prevalence of free electrons. N-type doped silicon is a much better conductor than pure silicon is.

Actually, only part of our solar cell is N-type. The other part is doped with boron, which has only three electrons in its outer shell instead of four, to become P-type silicon. Instead of having free electrons, P-type silicon ("p" for positive) has free holes. Holes really are just the absence of electrons, so they carry the opposite (positive) charge. They move around just like electrons do.

So where has all this gotten us?

N-type Plus P-type Silicon

The interesting part starts when you put N-type silicon together with P-type silicon. Remember that every PV cell has at least one electric field. Without an electric field, the cell wouldn't work, and this field forms when the N-type and P-type silicon are in contact. Suddenly, the free electrons in the N side, which have been looking all over for holes to fall into, see all the free holes on the P side, and there's a mad rush to fill them in.

Before now, our silicon was all electrically neutral. Our extra electrons were balanced out by the extra protons in the phosphorous. Our missing electrons (holes) were balanced out by the missing protons in the boron. When the holes and electrons mix at the junction between N-type and P-type silicon, however, that neutrality is disrupted. Do all the free electrons fill all the free holes? No. If they did, then the whole arrangement wouldn't be very useful. Right at the junction, however, they do mix and form a barrier, making it harder and harder for electrons on the N side to cross to the P side. Eventually, equilibrium is reached, and we have an electric field separating the two sides

The effect of the electric field in a PV cell

This electric field acts as a diode, allowing (and even pushing) electrons to flow from the P side to the N side, but not the other way around. It's like a hill -- electrons can easily go down the hill (to the N side), but can't climb it (to the P side).

So we've got an electric field acting as a diode in which electrons can only move in one direction. Let's see what happens when light hits the cell.

When Light Hits the Cell

When light, in the form of photons, hits our solar cell, its energy frees electron-hole pairs.

Each photon with enough energy will normally free exactly one electron, and result in a free hole as well. If this happens close enough to the electric field, or if free electron and free hole happen to wander into its range of influence, the field will send the electron to the N side and the hole to the P side. This causes further disruption of electrical neutrality, and if we provide an external current path, electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there, doing work for us along the way. The electron flow provides the current, and the cell's electric field causes a voltage. With both current and voltage, we have power, which is the product of the two.

Operation of a PV cell

How much sunlight energy does our PV cell absorb? Unfortunately, the most that our simple cell could absorb is around 25 percent, and more likely is 15 percent or less. Why so little?

Energy Loss

Why does our solar cell absorb only about 15 percents of the sunlight's energy? Visible light is only part of the electromagnetic spectrum. Electromagnetic radiation is not monochromatic -- it is made up of a range of different wavelengths, and therefore energy levels. (See How Special Relativity Works for a good discussion of the electromagnetic spectrum.)

Light can be separated into different wavelengths, and we can see them in the form of a rainbow. Since the light that hits our cell has photons of a wide range of energies, it turns out that some of them won't have enough energy to form an electron-hole pair. They'll simply pass through the cell as if it were transparent. Still other photons have too much energy. Only a certain amount of energy, measured in electron volts (eV) and defined by our cell material (about 1.1 eV for crystalline silicon), is required to knock an electron loose. We call this the band gap energy of a material. If a photon has more energy than the required amount, then the extra energy is lost (unless a photon has twice the required energy, and can create more than one electron-hole pair, but this effect is not significant). These two effects alone account for the loss of around 70 percent of the radiation energy incident on our cell.

Why can't we choose a material with a really low band gap, so we can use more of the photons? Unfortunately, our band gap also determines the strength (voltage) of our electric field, and if it's too low, then what we make up in extra current (by absorbing more photons), we lose by having a small voltage. Remember that power is voltage times current. The optimal band gap, balancing these two effects, is around 1.4 eV for a cell made from a single material.

We have other losses as well. Our electrons have to flow from one side of the cell to the other through an external circuit. We can cover the bottom with a metal, allowing for good conduction, but if we completely cover the top, then photons can't get through the opaque conductor and we lose all of our current (in some cells, transparent conductors are used on the top surface, but not in all). If we put our contacts only at the sides of our cell, then the electrons have to travel an extremely long distance (for an electron) to reach the contacts. Remember, silicon is a semiconductor -- it's not nearly as good as a metal for transporting current. Its internal resistance (called series resistance) is fairly high, and high resistance means high losses. To minimize these losses, our cell is covered by a metallic contact grid that shortens the distance that electrons have to travel while covering only a small part of the cell surface. Even so, some photons are blocked by the grid, which can't be too small or else its own resistance will be too high.

Finishing the Cell

There are a few more steps left before we can really use our cell. Silicon happens to be a very shiny material, which means that it is very reflective. Photons that are reflected can't be used by the cell. For that reason, an antireflective coating is applied to the top of the cell to reduce reflection losses to less than 5 percent.

The final step is the glass cover plate that protects the cell from the elements. PV modules are made by connecting several cells (usually 36) in series and parallel to achieve useful levels of voltage and current, and putting them in a sturdy frame complete with a glass cover and positive and negative terminals on the back.

Basic structure of a generic silicon PV cell

Single crystal silicon isn't the only material used in PV cells. Polycrystalline silicon is also used in an attempt to cut manufacturing costs, although resulting cells aren't as efficient as single crystal silicon. Amorphous silicon, which has no crystalline structure, is also used, again in an attempt to reduce production costs. Other materials used include gallium arsenide, copper indium diselenide and cadmium telluride. Since different materials have different band gaps, they seem to be "tuned" to different wavelengths, or photons of different energies. One way efficiency has been improved is to use two or more layers of different materials with different band gaps. The higher band gap material is on the surface, absorbing high-energy photons while allowing lower-energy photons to be absorbed by the lower band gap material beneath. This technique can result in much higher efficiencies. Such cells, called multi-junction cells, can have more than one electric field.

Powering a House

Now that we have our PV module, what do we do with it? What would you have to do to power your house with solar energy? Although it's not as simple as just slapping some modules on your roof, it's not extremely difficult to do, either.

First of all, not every roof has the correct orientation or angle of inclination to take advantage of the sun's energy. Non-tracking PV systems in the Northern Hemisphere should point toward true south (this is the orientation). They should be inclined at an angle equal to the area's latitude to absorb the maximum amount of energy year-round. A different orientation and/or inclination could be used if you want to maximize energy production for the morning or afternoon, and/or the summer or winter. Of course, the modules should never be shaded by nearby trees or buildings, no matter the time of day or the time of year. In a PV module, even if just one of its 36 cells is shaded, power production will be reduced by more than half.

If you have a house with an unshaded, south-facing roof, you need to decide what size system you need. This is complicated by the facts that your electricity production depends on the weather, which is never completely predictable, and that your electricity demand will also vary. These hurdles are fairly easy to clear. Meteorological data gives average monthly sunlight levels for different geographical areas. This takes into account rainfall and cloudy days, as well as altitude, humidity, and other more subtle factors. You should design for the worst month, so that you'll have enough electricity all year. With that data, and knowing your average household demand (your utility bill conveniently lets you know how much energy you use every month),there are simple methods you can use to determine just how many PV modules you'll need. You'll also need to decide on a system voltage, which you can control by deciding how many modules to wire in series.

Obstacles

You may have already guessed a couple of problems that we'll have to solve. First, what do we do when the sun isn't shining? Certainly, no one would accept only having electricity during the day, and then only on clear days, if they have a choice. We need energy storage -- batteries. Unfortunately, batteries add a lot of cost and maintenance to the PV system. Currently, however, it's a necessity if you want to be completely independent. One way around the problem is to connect your house to the utility grid, buying power when you need it and selling to them when you produce more than you need. This way, the utility acts as a practically infinite storage system. The utility has to agree, of course, and in most cases will buy power from you at a much lower price than their own selling price. You will also need special equipment to make sure that the power you sell to your utility is synchronous with theirs -- that it shares the same sinusoidal waveform and frequency. Safety is an issue as well. The utility has to make sure that if there's a power outage in your neighborhood, your PV system won't try to feed electricity into lines that a lineman may think is dead. This is called islanding.

If you decide to use batteries, keep in mind that they will have to be maintained, and then replaced after a certain number of years. The PV modules should last 20 years or more, but batteries just don't have that kind of useful life. Batteries in PV systems can also be very dangerous because of the energy they store and the acidic electrolytes they contain, so you'll need a well-ventilated, non-metallic enclosure for them.

Deep-cycle Batteries

What kind of batteries are used in PV systems? Although several different kinds are commonly used, the one characteristic that they should all have in common is that they are deep-cycle batteries. Unlike your car battery, which is a shallow-cycle battery, deep-cycle batteries can discharge more of their stored energy while still maintaining long life. Car batteries discharge a large current for a very short time -- to start your car -- and are then immediately recharged as you drive. PV batteries generally have to discharge a smaller current for a longer period (such as all night), while being charged during the day.

The most commonly used deep-cycle batteries are lead-acid batteries (both sealed and vented) and nickel-cadmium batteries. Nickel-cadmium batteries are more expensive, but last longer and can be discharged more completely without harm. Even deep-cycle lead-acid batteries can't be discharged 100 percent without seriously shortening battery life, and generally, PV systems are designed to discharge lead-acid batteries no more than 40 percent or 50 percent.

Also, the use of batteries requires the installation of another component called a charge controller. Batteries last a lot longer if care is taken so that they aren't overcharged or drained too much. That's what a charge controller does. Once the batteries are fully charged, the charge controller doesn't let current from the PV modules continue to flow into them. Similarly, once the batteries have been drained to a certain predetermined level, controlled by measuring battery voltage, many charge controllers will not allow more current to be drained from the batteries until they have been recharged. The use of a charge controller is essential for long battery life.

DC to AC

The other problem is that the electricity generated by your PV modules, and extracted from your batteries if you choose to use them, is direct current, while the electricity supplied by your utility (and the kind that every appliance in your house uses) is alternating current. You will need an inverter, a device that converts DC to AC. Most large inverters will also allow you to automatically control how your system works. Some PV modules, called AC modules, actually have an inverter already built into each module, eliminating the need for a large, central inverter, and simplifying wiring issues.  

General schematic of a residential PV system with battery storage

Throw in the mounting hardware, wiring, junction boxes, grounding equipment, overcurrent protection, DC and AC disconnects and other accessories and you have yourself a system. Electrical codes must be followed (there's a section in the National Electrical Code just for PV), and it's highly recommended that the installation be done by a licensed electrician who has experience with PV systems. Once installed, a PV system requires very little maintenance (especially if no batteries are used), and will provide electricity cleanly and quietly for 20 years or more.

If photovoltaics are such a wonderful source of free energy, then why doesn't the whole world run on solar power? Some people have a flawed concept of solar energy. While it's true that sunlight is free, the electricity generated by PV systems is not. As you can see from our discussion of a household PV system, quite a bit of hardware is needed. Currently, an installed PV system will cost somewhere around $9 per peak Watt. To give you an idea of how much a house system would cost, let's consider the Solar House -- a model residential home in Raleigh, North Carolina, with a PV system set up by the North Carolina Solar Center to demonstrate the technology. It's a fairly small home, and it is estimated that its 3.6-kW PV system covers about half of the total electricity needs (this system doesn't use batteries -- it's connected to the grid). Even so, at $9 per Watt, this installed system would cost you around $32,000.

That's why PV is usually used in remote areas, far from a conventional source of electricity. Right now, it simply can't compete with the utilities. Costs are coming down as research is being done, however. Researchers are confident that PV will one day be cost effective in urban areas as well as remote ones. Part of the problem is that manufacturing needs to be done on a large scale to reduce costs as much as possible. That kind of demand for PV, however, won't exist until prices fall to competitive levels. It's a Catch-22 situation. Even so, demand and module efficiencies are constantly rising, prices are falling, and the world is becoming increasingly aware of environmental concerns associated with conventional power sources, making photovoltaics a technology with a bright future.

You will not find any prices on this web site! P/V prices change almost daily, they go up and down, it would not be fair to list a price that might be unrepresenative We work with many different suppliers to bring you the best price possible for your solution. Please contact us for more information.

Photo courtesy DOE/NREL Photo credit SunLine Transit Agency Solar panels absorb energy to produce hydrogen at SunLine Transit Agency.
Sources
* Beckman, William A. and Duffie, John A., Solar Engineering of Thermal Processes. 2nd Ed. John Wiley and Sons, Inc. 1991, pp.768-793.
* Zweibel, Ken. Harnessing Solar Power: The Photovoltaics Challenge. Plenum Press, New York and London. 1990.