The following is a solar workshop presentation I made in late August for local architects -- Jack Star

Breaking News (Sept. 29) At least 3 companies at Solar Power 2007 (Sept. 24-26)are reporting that by the end of 2008 or first quarter 2009 they will be producing solar-based electricity at $1 a watt. At that price point clean, unlimited solar power is competitive with natural gas and coal, and probably nuclear, power plants. More to come.

Whenever we talk about using solar as an energy source, the very first step is to plan to reduce energy demand. That is not only logical; generally it is the most cost effective.

The second step is to position the structure on the building site, and to design the roof, so that there is a south-facing, unobstructed rectangle of, at the very least, 110 square feet for each kilowatt you plan to install. When solar systems are an afterthought, the costs of installation almost invariable increase.

The basic solar cycle works this way:
The sun shines and the light strikes a photoreceptor freeing electrons that flow through a wire creating a direct current (like that of a car battery) which can:
directly operate lighting or other equipment, or
pass through a controller to charge a battery, or
pass through another circuit in a box called an inverter which converts the Direct Current to Alternating Current where it can:
be fed directly through a secondary breaker box to specific circuits in the building, or
        be merged with electricity coming from the power utility (the grid), or
        feed back to the grid any solar-produced excess electricity, which either
        spins the electric meter backward, or
        goes through a second meter providing a credit on the next electric bill.

Or all of the above, or any of the above, or any combination.

Today, at each stage: the solar cells, the modules that house them, the framework that supports the modules, the controller, the battery, the inverter are all undergoing technological advances and changes in manufacturing processes to increase efficiencies, optimize the amount of electricity produced, and lower the cost of producing that electricity. Everything is in flux. The only constant is the sun.

And speaking of the sun, about one kilowatt of solar energy falls on one square meter, approximately 10.75 sq ft -- about 93 watts per square foot when the sun is strongest. As a typical solar module is about 17.5 square ft. and most solar modules fall into the 160-200 watt range (9 to 11 watts/sq.ft.), these modules are currently capturing between 1/8th to 1/10th of the solar energy potential.

The Basic Module

Let´s start with the most prevalent system that is in use today. The heart of the system is a silicon wafer-based solar cell. This is where the interaction begins. We´ve had decades of experience with these cells, and that is why module manufacturers can offer 20 to 25 year warranties.

The solar cells in a module are laid out like a chessboard and positioned like the filling in a sandwich. There is a protective backing, and then the cells laminated with a clear plastic-like material and a special glass as the top layer and all of it held together by a frame, generally of anodized aluminum.

Their electrical connections are soldered together, connectors are soldered to one edge of the module and the wiring that connects the module together is attached to those connectors. In modern manufacturing plants the entire assembly is done using a series of computer controlled robotic arms that move the elements of the module through an automated process that includes final testing.

The modules come is a range of wattage and sizes. The typical ones you will be dealing with are just over five feet high and about three and a quarter feet wide, less than two inches high and weigh between 38-43 pounds.
 
So, the start of the process is the sun.  Even on cloudy days, as long as there is light, some electricity will still be generated. The more direct the sun, the more electricity is produced. That´s why you need modules to be placed facing, as much as practical, solar south, without trees, wires, chimneys, other buildings, casting shadows. Even small shadows, like that from a telephone wire, can reduce the efficiency of a module by 50 percent.

Stationary or Following the Sun

This positioning leads to one of the first variables to consider. Should the modules be stationary or should they move, following the sun from sunrise to sunset? The sun is also higher in the summer and lower in the winter. At what angle do stationary modules capture the maximum amount of sunlight all year round? If roof mounted, is the angle of the roof sufficient, or is additional bracing required to tilt the modules? [The "tilt angle" is typically the number of degrees of the local latitude -- in Savannah that is 32 degrees from the horizontal.]

The standard stationary modules are mounted on a pair of parallel rails, usually made of aluminum, which are held in place by anchors that penetrate the roof. There are a variety of types of anchors; some need to be fastened from the inside, while others are drilled into the roof truss. The connecting hardware pieces are made of aluminum and/or stainless steel and fastened by bolts.

Obviously care has to be taken to apply sealant, adhesives, roofing cement, and sometimes even flashing, to prevent future roof leaks.

But Can They Look Good

Over the last few years, manufacturers have been paying more attention to the aesthetics of the solar modules. Some homeowner´s associations have found them so unappealing that they have banned rooftop solar installations. Manufacturers have responded by providing frames in colors to match typical roof shingles, and by changing the color of the glass covering.

Now that you know where to place the modules, how much electricity do you plan to produce? That is the second variable because it depends upon the amount of roof space available, the energy demands of the building, the percentage of energy demand you expect solar to provide, and, frequently the determining factor, the budget available – including grants, rebates, tax credits, or other financial incentives.

Determining Energy Demand

The detailed way to determine energy demand is to catalog every electric light, appliance and piece of equipment, multiply the wattage of each by the average number of hours a day in service, multiple that by 365 days and divide by 1000 to determine the total number of kilowatt hours used each year.

A ballpark figure can more easily be arrived at by locating the electric bills for a comparable building and subtracting the starting kilowatt hour reading the first month of the year from the ending reading for the last month of the year. Some utilities can also give you average usage.

In the Southeast you can expect current solar modules to deliver from 1600 to 2000 kilowatt hours per year for each kilowatt of installed modules. Because some energy is lost in the wiring and by the inverter, the actual amount available is closer to 90% -- 1440 to 1800 kilowatt hours per year per installed kilowatt.

In this region currently the major costs of the system are: for the solar modules, roughly $4.30 a watt (updated Sept. 21), the inverter, about 90 cents a watt, and installation, $3 to $4 a watt. Generally speaking you install an inverter with wattage greater than that installed on the rooftop. Large systems tend to cost a little less per installed watt.

While prices of silicon-based solar cells have trended downwards for many years, the industry was caught unaware by the sharp increase in demand, particularly from overseas. As a result prices have remained firm. Current industry projections, however, predict a drop of close to 40 percent within two years. As solar modules represent about 50 percent of the cost of a solar installation that should mean the cost of a total installation will be cut by 20 to 30 percent. Economies of scale are kicking in as the sector has grown nearly 40 percent a year for the past decade and 60 percent from 2005 to 2006.

Thin Film Solar

Although silicon-based modules represent well over 80 percent of solar installations, thin film solar, currently growing at 70 percent a year, is posing a serious challenge. Part of the lure of thin film is its potential to rival traditional power utilities by providing clean, pollution free electricity with no carbon emissions for the same price as, or even less than, a coal burning power station.

As the name implies, microscopically thin layers of photoreceptors are sandwiched in and sealed between other layers, typically some form of plastic. Sometimes they use another, less expensive, form of silicon, other times they use chemical compounds that have properties that will allow light to excite the flow of electrons.

The names of these compounds can look like alphabet soup. CdTe – cadmium telluride; CIGS – copper, indium, gallium, selenide – doesn´t that roll off the tongue, TiO – titanium oxide combined with a dye.

It is the science of nanotechnology that underlies many of these developments. Particles at almost a molecular level are deposited in layers, either on a flexible backing or on glass, and then laminated with a durable protective coating. Some manufacturers produce photovoltaic strips on rolls that are miles long. Many employ a cell structure that is layered so that each layer absorbs a different wavelength of light: the top red, the middle yellow/green and the bottom blue.

Independent of the chemistry, the result is an electricity generating, durable film that can be applied, for example, to a thin layer of stainless steel, flexible plastic, glass, a variety of building materials, and even cloth.

There is a trade-off, however. While thin films can produce lighter modules, for example, currently they only produce about a third as much electricity per square foot when compared to traditional crystalline silicon. Manufacturers claim, however, that their products are able to use more diffuse light, on a cloudy day, for example, or light coming from a less than optimal angle. Whatever the measure, the cost per installed watt today is substantially less than solar cells based on silicon. Thin film uses 100 times less material than traditional crystalline silicon cells.

In fact, as I prepared this material, prices have already begun to come down. Latest industry figures show: (update March 2008 -- prices remain firm as demand exceeds supply)lowest mono-crystalline (silicon) module at $4.35 a watt, lowest multi-crystalline module at $4.29 a watt and lowest thin film module at $3.57 a watt.

Research labs around the world are developing techniques to sharply increase the efficiency of thin film solar, and it is likely that some of these will be entering the pilot plant stage as early as 2008.

You´ve heard a lot about BIPV, Building Integrated Photovoltaics. Thin films play a substantial role turning windows, awnings, canopies, carports, curtain walls, sunshades, sun louvers and curtains, skylights and atria into sources of electrical energy.

BIPV may also play a crucial role in retrofitting existing buildings to generate some of their own electricity.

It´s not too surprising that roofing materials comprise one of the major uses of thin film today. Companies are bonding thin film to roof shingles, tiles and metal roofs. Some are even providing a complete roofing package consisting of insulation, the waterproof membrane and the solar material.

As thin film solar can also be deposited directly on glass, other companies are specifically manufacturing large panes of glass for institutional windows.

Lightweight modules can also be pole-mounted elsewhere on the property and they can be fastened to a south-facing wall.

Although not in production, you can easily imagine that solar film could be incorporated into siding and shutters.

Dynamic Industry Spurs Change

One of the reasons I became so fascinated with solar energy is that the intellectual ferment that permeates the industry reminds me of the early days of the personal computer. Then, small companies and large, university and industrial research labs, individual tinkerers and software developers, inventors in garages and struggling start-ups, built a dynamic industry, which changed our world. That same dynamism infuses every area of solar power development and five years from now the world of energy will be forever changed.

Which brings us to concentrating photovoltaics, yet another way manufacturers seek to increase the amount of electricity they can squeeze from a solar cell.

High efficiency crystalline silicon solar cells are expensive to manufacture, so the basis for concentrating photovoltaics is to use a smaller amount of silicon, but concentrate the light. Again, as in so many areas of solar power development, there are a variety of different techniques. One uses Fresnel lenses to concentrate the sun´s rays, others use an array of small mirrors, or of reflective metal, others build in miniature well like structures to focus more light. Others use nanostructures to capture photons.

Concentrating photovoltaics generally require that the modules track the sun´s movement across the sky. Right now, concentrating photovoltaic systems are just beginning to come out of the lab and into pilot plant stage.

Show Me the Money

Now let's talk about money. The State of Georgia does not provide any financial incentives either to individuals or businesses. Neither does Georgia Power. The only incentive available is the Federal Tax Credit -- a tax credit comes directly from the amount of income tax owed the government. The current law, which was extended from the end of this year to the end of 2008, provides a 30 percent tax credit to individuals with a cap of $2,000 each for both photovoltaic and solar hot water heating systems. While this is good news for solar hot water it's only a modest amount for photovoltaics.

Business, however, also receive a 30 percent tax credit, and there is no cap. They can also take advantage of a five year accelerated depreciation. For both individuals and businesses the tax credit can be carried forward, if necessary.

Georgia Power does offer a dual metering program. All of the electricity produced goes directly to the grid through one meter -- and Georgia Power currently provides a credit of 17.4 cents per kWh -- and the electricity coming into the house is charged at the regular rate.

Part of the energy bill going through Congress this September contains some provisions that expand the incentives. The tax credit for individuals would no longer have a cap but the credit still runs through the end of  2008,  while the tax credit for businesses would be extended through 2016. It also provides the ability for corporate and personal filers to claim the Investment Tax Credit against the Alternative Minimum Tax.

According to an industry spokesman: "We estimate that, with the solar incentive provisions in the tax title, solar power will provide 50 percent of all new electricity in the US within eight years. The growth of solar energy markets will create tens of thousands of new high-tech jobs throughout the United States, while helping to conserve natural gas and saving American taxpayers billions in energy costs."

That conservation of natural gas may not be intuitive. It is a function of the way large utilities operate. Coal and nuclear power plants provide what the utility calls the base load -- that meets consistent demand. Where the demand sharply exceeds the base load, called peak demand, -- especially on hot summer days when air conditioners are running full force, the utility kicks in back up stations that are powered by natural gas, which are much more costly to operate. However, solar power generation is also greatest during this period of peak demand thus reducing the amount of natural gas required, and indirectly the cost to the consumer.

Big Box Solar Should Benefit

The extension of the tax credit for business should have a major, and significant, impact on corporations that have many "big box" buildings. Shopping centers, distribution centers and warehouses, and manufacturing facilities all have very large roof areas, some in the millions of square feet. These companies benefit greatly from solar installations. Wal-Mart, for example, plans to add solar to all of their major buildings. Staples and other large chains are also moving in that direction. Companies of this size often require many years to phase in these operations.

I mentioned at the very beginning that reducing energy demand was the first step to implementing a solar system. Here's one scenario. An average home in the Southeast uses from 10,000 to 12,000 kilowatt hours of electricity per year. In order to meet, say 50 percent using solar, would require the installation of at least 3 kilowatts of solar modules. At today's prices that's about $22,000, even with the tax credit.

If, however, the house is built to energy efficient standards that reduce demand by 35 percent - to roughly 6500 to 7800 kilowatt hours, a 2-kilowatt installation, at closer to $14,000, would make a major difference.

Why Now?

Then there is the interesting question: Why, if we know the cost of solar power is going to continually decrease, should we install now, why not wait?

1) Because if you aren't serious about solar from the beginning of the project, you will not plan sufficiently for it. That's just human nature.

2) Because it will cost you more to install after the building is up and running. You won't be saving that much, and you will have been paying top dollar to the utility while you wait.

3) If you need the tax credit now, or know you will need to carry some forward, you will miss the opportunity.

4) You always have the option to install part of the system now; get the infrastructure in place and understand how it works in your building, and then add more later, with no increase in installation costs. This way you also average the total cost down.

As you can see, there is quite a solar stew bubbling along right now, and we really haven't touched on large scale, utility size concentrating solar power fields that have begun operating in the Western desert and will be generating Gigawatts of solar power within the next few years.

In addition to this chaotic world of discovery that is going on in the solar field, one trend is rapidly emerging. Some of these newer technologies are ready for prime time. They are tested and commercially viable. The manufacturers have developed their own proprietary machinery. Within the next year or two we are about to witness a production explosion as a result of two levels of economies of scale.

The first occurs as the new factories reach capacity. And the second is underway as manufacturers are now beginning to replicate their proprietary production equipment. While the first few machines were expensive for them to build and test and fine tune, the next generation costs much less. Thus the entire manufacturing cycle leads to decreasing costs and increasing efficiencies. It is possible today to buy a turnkey factory – and that capability is jump-starting solar power development around the world.

The only constant is the sun.

Questions? Comments? Email Jack Star